Re: [PSES] 6dB pad

[Paolo Roncone]

Hi Ken and all others,

Thanks again for your comments and inputs. I checked the data sheets of the
two antennas that I'm using in the 30M-6G range and considering CISPR
16-1-4 sec.4.5.3 "c) The return loss of the antenna with the antenna feeder
connected shall not be less than 10 dB. A matching attenuator may be part
of the antenna feeder cable for antennas if needed to meet this
requirement."

I'm leaning towards the following change:

30 MHz - 1 GHz range :
the bilog antenna I'm using has a typical VSWR way above 1.9 below 200 MHz,
corresponding to RL way below 10 dB -> 6dB pad moved to antenna end of
cable

1 - 6 GHz range:
the horn antenna I'm using has a typical VSWR of 1.5, corresponding to RL
of  14 dB -> 6dB pad to be removed from the chain, relying on the nominal
50 ohm input impedance and on the auto attenuation of the EMI receiver, and
hoping that the minimum 10dB does not increase the noise floor too much. I
also need to get notch filters for the 2.4G and 5G BL and Wi-Fi signals
that I get more and more frequently in our tested EUTs.

Does that sound ok?

Thanks again
Paolo

On Sun, Jul 16, 2023 at 12:26 AM Ken Javor 
wrote:

> The typical spectrum analyzer / EMI receiver input only looks like 50 Ω
> with some input attenuation. Typically, they specify vswr in a 50 Ω system
> with 10 dB internal attenuation selected.
>
>
>
> --
>
> Ken Javor
>
> (256) 650-5261
>
>
>
> *From: *Richard Nute 
> *Reply-To: *
> *Date: *Saturday, July 15, 2023 at 4:28 PM
> *To: *
> *Subject: *Re: [PSES] 6dB pad
>
>
>
>
>
> This discussion not only applies to EMI testing, it also applies to
> high-frequency and fast risetime pulse voltage measurements.  A 6 dB (2x
> voltage attenuation) or 10 dB (~3x voltage attenuation) in a 50-ohm system
> which would otherwise be subject to reflections due to impedance
> discontinuities (i.e., which create the VSWR) will give a more accurate
> voltage measurement (which would otherwise be dependent on the length of
> the cable due to VSWR).  The attenuator makes the input impedance look like
> nearly 50 ohms regardless of actual load impedance.  Same for a source
> impedance that is not 50 ohms.
>
>
>
> I’m not sure that you need a pad at both ends.  If the input to the
> receiver is 50 ohms throughout the frequency band, then there are no
> reflections from the receiver end and no VSWR that would distort the
> measurement.  Arguments?
>
>
>
> Best regards,
>
> Rich
>
>
>
> *From:* Ken Javor 
> *Sent:* Saturday, July 15, 2023 10:15 AM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* Re: [PSES] 6dB pad
>
>
>
> Receiver vswr is specified with 10 dB attenuation because the mixer itself
> is not 50 Ω.
>
>
>
> Antenna vswr is usually best in the middle of the usable frequency range.
> Worst case at the low end for EMI antennas used down to 30 MHz, because
> except for half-wave dipoles, they are electrically short at and near 30
> MHz. Antenna vswr is typically stated at the antenna port, without any
> added attenuation.
>
>
>
> Putting attenuation at the EMI receiver input takes care of mixer
> mismatch, and padding the antenna takes care at the opposite end. You need
> a pad at both ends to completely control vswr-related uncertainty.
>
>
>
> Unfortunately, you often cannot stand the desensitization of all the extra
> attenuation.
>
>
>
> --
>
> Ken Javor
>
> (256) 650-5261
>
>
>
> *From: *Paolo Roncone 
> *Reply-To: *Paolo Roncone 
> *Date: *Saturday, July 15, 2023 at 10:29 AM
> *To: *
> *Subject: *Re: [PSES] 6dB pad
>
>
>
> Hi Ken
>
>
>
> Thanks for your feedback. Why should the VSWR be specified with 10 dB
> attenuation? That would alter (for the better) the specified VSWR itself. I
> checked th
>
> e data sheets of 3 antennas that I'm using (a hybrid bilog, a log-periodic
> and a horn) and in all of them a "typical" VSWR is specified, without any
> mention to a 10dB attenuation.
>
>
>
> Paolo
>
>
>
> On Fri, Jul 14, 2023 at 11:33 PM Ken Javor 
> wrote:
>
> Not expressing an opinion, just listing some facts.
>
>
>
> Absent any input attenuation, vswr will be higher than manufacturer
> specifies, because the specification is with 10 dB input attenuation
> (typically). Therefore, the use of a 6 dB pad, absent any internal
> attenuation, will not meet the manufacturer’s spec for vswr, and thus your
> uncertainty budget increases.
>
>
>
> If your ambient source is brush noise, preselection should help with that,
> once you are out of band to it.
>
>
>
> Band stop filters will help with known transmitters.
>
>
>
> --
>
> Ken Javor
>
&

Re: [PSES] 6dB pad

[Paolo Roncone]

Hi Ken and Tom

Thanks for your inputs. Yes, the 6 dB pad is at the receiver input, in
addition or not (depending on the signal level) to the built-in attenuator
of the receiver.
If the same 6dB pad is put at the antenna output instead of receiver input,
it's at the other end of the cable connecting antenna with receiver.

Is it preferable, or recommended, or right to consider the 6dB pad only at
the antenna output, rather than at the receiver input? If yes, why,
considering that the whole chain (antenna, cable, pad) is nominal 50 ohm?

Shouldn't the 6dB pad in any case improve the VSWR or return loss of the
antenna-cable-receiver chain? Maybe I'm oversimplifying the picture...

Anyway, *assuming* the antenna has a good (> 10dB) return loss or good (<
1.5) VSWR, no need for any pad at all, or better (recommended) no pad at
all?

Thanks

Paolo

On Sat, Jul 15, 2023 at 3:30 AM Ken Javor 
wrote:

> But he is placing the pad at the receiver input in lieu of an internally
> selected 10 dB, not at the antenna's output port.
>
> --
> Ken Javor
>
> (256) 650-5261
>
> On 7/14/23, 6:00 PM, "T.Sato"  wrote:
>
> On Fri, 14 Jul 2023 22:53:41 +0200,
>   Paolo Roncone  wrote:
>
> > I'm having a discussion with my colleague about the use of a fixed
> 6dB
> > attenuation pad at the input of the EMI receiver for radiated EMI in
> the
> > range 30MHz - 6GHz.
> > The pad I'm using is a Weinschel 6dB N-type 50ohm.
> > My colleague says the pad is an unnecessary element in the
> measurement
> > chain, because the receiver built-in attenuator (typically with 10dB
> steps)
> > and proper adjustments in the amplitude settings are enough.
> ...
>
> For example in case of CISPR 16, CISPR 16-1-4 requires antennas to have
> return loss higher than 10 dB.
>
> 6 dB pad at antenna output makes this requirement satisfied regardless
> of
> return loss of the antenna itself, even for biconical and hybrid
> antennas
> which will have very bad VSWR.
>
> Regards,
> Tom
>
>
>
> On Fri, 14 Jul 2023 22:53:41 +0200,
>   Paolo Roncone  wrote:
>
> > Hi all,
> >
> > I'm having a discussion with my colleague about the use of a fixed
> 6dB
> > attenuation pad at the input of the EMI receiver for radiated EMI in
> the
> > range 30MHz - 6GHz.
> > The pad I'm using is a Weinschel 6dB N-type 50ohm.
> > My colleague says the pad is an unnecessary element in the
> measurement
> > chain, because the receiver built-in attenuator (typically with 10dB
> steps)
> > and proper adjustments in the amplitude settings are enough.
> >
> > The reason I'm using the 6dB pad is that - based on my EMI testing
> > experience, the 6dB pad is a good trade-off between the need to avoid
> > receiver overload and maintaining a good enough noise floor.
> > Without the pad the noise floor is of course lower and everything is
> fine
> > as long as the input levels are low enough.
> > But in the majority of the test scenarios I'm working on the input
> levels
> > are not so low and the 6dB pad is just enough to avoid triggering
> the auto
> > built-in 10dB attenuation, that kicks in when the receiver
> attenuation is
> > in auto mode, and that is oftentimes an overkill, raising the noise
> floor
> > too much, especially in the 1-6 GHz range.
> > I have the 6dB pad calibrated for cable loss once a year together
> with the
> > N-cable connecting to the antenna. And also the cable calibrated
> without
> > the pad.
> >
> > The most typical sources of overload are transient noise generated by
> > motors (especially brush DC motors)  and signals from radio modules
> like
> > 2.4G wi-fi, Bluetooth and 5G wi-fi.
> >
> > In addition to overload protection, the 6dB pad improves the VSWR at
> the
> > cable-receiver interface, as explained in C.J.Paul's EMC
> Introduction to
> > EMC (John Wiley 2nd Ed.) Ch.7.
> > Based on the above I think that, being a resistive network
> stabilizing the
> > 50ohm termination impedance at the receiver end, the 6dB 50ohm pad
> is a
> > good practice that can prevent overload or excessive
> auto-attenuation, and
> > worst-case doesn't do any harm. Or, am I missing something here?
> >
> > I'd like to know if there is someone else in this community who has
> > experience using fixed attenuation pads at the receiver end of EMI
> > receivers/spectrum analyzers, or any opinion about it.
&

Re: [PSES] 6dB pad

[Paolo Roncone]

Hi Ken

Thanks for your feedback. Why should the VSWR be specified with 10 dB
attenuation? That would alter (for the better) the specified VSWR itself. I
checked th
e data sheets of 3 antennas that I'm using (a hybrid bilog, a log-periodic
and a horn) and in all of them a "typical" VSWR is specified, without any
mention to a 10dB attenuation.

Paolo

On Fri, Jul 14, 2023 at 11:33 PM Ken Javor 
wrote:

> Not expressing an opinion, just listing some facts.
>
>
>
> Absent any input attenuation, vswr will be higher than manufacturer
> specifies, because the specification is with 10 dB input attenuation
> (typically). Therefore, the use of a 6 dB pad, absent any internal
> attenuation, will not meet the manufacturer’s spec for vswr, and thus your
> uncertainty budget increases.
>
>
>
> If your ambient source is brush noise, preselection should help with that,
> once you are out of band to it.
>
>
>
> Band stop filters will help with known transmitters.
>
>
>
> --
>
> Ken Javor
>
> (256) 650-5261
>
>
>
> *From: *Paolo Roncone 
> *Reply-To: *Paolo Roncone 
> *Date: *Friday, July 14, 2023 at 3:53 PM
> *To: *
> *Subject: *[PSES] 6dB pad
>
>
>
> Hi all,
>
>
> I'm having a discussion with my colleague about the use of a fixed 6dB
> attenuation pad at the input of the EMI receiver for radiated EMI in the
> range 30MHz - 6GHz.
> The pad I'm using is a Weinschel 6dB N-type 50ohm.
> My colleague says the pad is an unnecessary element in the measurement
> chain, because the receiver built-in attenuator (typically with 10dB steps)
> and proper adjustments in the amplitude settings are enough.
>
> The reason I'm using the 6dB pad is that - based on my EMI testing
> experience, the 6dB pad is a good trade-off between the need to avoid
> receiver overload and maintaining a good enough noise floor.
>
> Without the pad the noise floor is of course lower and everything is fine
> as long as the input levels are low enough.
>
> But in the majority of the test scenarios I'm working on the input levels
> are not so low and the 6dB pad is just enough to avoid triggering the auto
> built-in 10dB attenuation, that kicks in when the receiver attenuation is
> in auto mode, and that is oftentimes an overkill, raising the noise floor
> too much, especially in the 1-6 GHz range.
>
> I have the 6dB pad calibrated for cable loss once a year together with the
> N-cable connecting to the antenna. And also the cable calibrated without
> the pad.
>
>
> The most typical sources of overload are transient noise generated by
> motors (especially brush DC motors)  and signals from radio modules like
> 2.4G wi-fi, Bluetooth and 5G wi-fi.
>
> In addition to overload protection, the 6dB pad improves the VSWR at the
> cable-receiver interface, as explained in C.J.Paul's EMC Introduction to
> EMC (John Wiley 2nd Ed.) Ch.7.
> Based on the above I think that, being a resistive network stabilizing the
> 50ohm termination impedance at the receiver end, the 6dB 50ohm pad is a
> good practice that can prevent overload or excessive auto-attenuation, and
> worst-case doesn't do any harm. Or, am I missing something here?
>
>
> I'd like to know if there is someone else in this community who has
> experience using fixed attenuation pads at the receiver end of EMI
> receivers/spectrum analyzers, or any opinion about it.
>
> Thanks a lot in advance for any feedback!
>
> Paolo
> --
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
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> emc-pstc postings are archived and searchable on the web at:
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[PSES] 6dB pad

[Paolo Roncone]

Hi all,

I'm having a discussion with my colleague about the use of a fixed 6dB
attenuation pad at the input of the EMI receiver for radiated EMI in the
range 30MHz - 6GHz.
The pad I'm using is a Weinschel 6dB N-type 50ohm.
My colleague says the pad is an unnecessary element in the measurement
chain, because the receiver built-in attenuator (typically with 10dB steps)
and proper adjustments in the amplitude settings are enough.

The reason I'm using the 6dB pad is that - based on my EMI testing
experience, the 6dB pad is a good trade-off between the need to avoid
receiver overload and maintaining a good enough noise floor.
Without the pad the noise floor is of course lower and everything is fine
as long as the input levels are low enough.
But in the majority of the test scenarios I'm working on the input levels
are not so low and the 6dB pad is just enough to avoid triggering the auto
built-in 10dB attenuation, that kicks in when the receiver attenuation is
in auto mode, and that is oftentimes an overkill, raising the noise floor
too much, especially in the 1-6 GHz range.
I have the 6dB pad calibrated for cable loss once a year together with the
N-cable connecting to the antenna. And also the cable calibrated without
the pad.

The most typical sources of overload are transient noise generated by
motors (especially brush DC motors) and signals from radio modules like
2.4G wi-fi, Bluetooth and 5G wi-fi.

In addition to overload protection, the 6dB pad improves the VSWR at the
cable-receiver interface, as explained in C.J.Paul's EMC Introduction to
EMC (John Wiley 2nd Ed.) Ch.7.
Based on the above I think that, being a resistive network stabilizing the
50ohm termination impedance at the receiver end, the 6dB 50ohm pad is a
good practice that can prevent overload or excessive auto-attenuation, and
worst-case doesn't do any harm. Or, am I missing something here?

I'd like to know if there is someone else in this community who has
experience using fixed attenuation pads at the receiver end of EMI
receivers/spectrum analyzers, or any opinion about it.

Thanks a lot in advance for any feedback!


Paolo

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[PSES] 6dB pad

[Paolo Roncone]

Hi all,

I'm having a discussion with my colleague about the use of a fixed 6dB
attenuation pad at the input of the EMI receiver for radiated EMI in the
range 30MHz - 6GHz.
The pad I'm using is a Weinschel 6dB N-type 50ohm.
My colleague says the pad is an unnecessary element in the measurement
chain, because the receiver built-in attenuator (typically with 10dB steps)
and proper adjustments in the amplitude settings are enough.

The reason I'm using the 6dB pad is that - based on my EMI testing
experience, the 6dB pad is a good trade-off between the need to avoid
receiver overload and maintaining a good enough noise floor.
Without the pad the noise floor is of course lower and everything is fine
as long as the input levels are low enough.
But in the majority of the test scenarios I'm working on the input levels
are not so low and the 6dB pad is just enough to avoid triggering the auto
built-in 10dB attenuation, that kicks in when the receiver attenuation is
in auto mode, and that is oftentimes an overkill, raising the noise floor
too much, especially in the 1-6 GHz range.
I have the 6dB pad calibrated for cable loss once a year together with the
N-cable connecting to the antenna. And also the cable calibrated without
the pad.

The most typical sources of overload are transient noise generated by
motors (especially brush DC motors)  and signals from radio modules like
2.4G wi-fi, Bluetooth and 5G wi-fi.

In addition to overload protection, the 6dB pad improves the VSWR at the
cable-receiver interface, as explained in C.J.Paul's EMC Introduction to
EMC (John Wiley 2nd Ed.) Ch.7.
Based on the above I think that, being a resistive network stabilizing the
50ohm termination impedance at the receiver end, the 6dB 50ohm pad is a
good practice that can prevent overload or excessive auto-attenuation, and
worst-case doesn't do any harm. Or, am I missing something here?

I'd like to know if there is someone else in this community who has
experience using fixed attenuation pads at the receiver end of EMI
receivers/spectrum analyzers, or any opinion about it.

Thanks a lot in advance for any feedback!

Paolo

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Re: [PSES] Antenna tilting or bore sighting for radiated emissions

[Paolo Roncone]

nce so it is within its ½
> power beamwidth at all times as it travels up and down the antenna mast.
>
>
>
> Larry K. Stillings
> Compliance Worldwide, Inc.
> *Test Locally, Sell Globally and Launch Your Products Around the World!*
> *FCC - Wireless - Telecom - CE Marking - International Approvals - Product
> Safety*
> 357 Main Street
> Sandown, NH 03873
> (603) 887 3903 Fax 887-6445
> complianceworldwide.com
>
> *Follow us on social media*
>
>linkedin.com/company/compliance-worldwide-inc
> twitter.com/complianceww
>
> Privileged/Confidential Information may be contained in this message. If
> you are not the addressee indicated in this message (or responsible for
> delivery of the message to such person), you may not copy or deliver this
> message to anyone. In such case, you should destroy this message and kindly
> notify the sender by reply email. Please advise immediately if you or your
> employer do not consent to Internet email for messages of this kind.
> Opinions, conclusions and other information in this message that do not
> relate to the official business of my firm shall be understood as neither
> given nor endorsed by it.
>
>
>
> *From:* Paolo Roncone
> *Sent:* Wednesday, March 29, 2023 1:06 PM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* [PSES] Antenna tilting or boresigjting for radiated emissions
>
>
>
> Hi all,
>
>
>
> Is there an FCC / ANSI requirement, or  maybe just recommendation, for
> antenna tilting or boresighting wrt radiated emissions in a semi-anechoic
> chamber ?
>
>
>
> If yes, can you please get me the reference section in FCC Part15 or ANSI
> std or somewhere else?
>
>
>
>
>
> Thanks a lot in advance!
>
> Paolo
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
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[PSES] Antenna tilting or boresigjting for radiated emissions

[Paolo Roncone]

Hi all,

Is there an FCC / ANSI requirement, or  maybe just recommendation, for
antenna tilting or boresighting wrt radiated emissions in a semi-anechoic
chamber ?

If yes, can you please get me the reference section in FCC Part15 or ANSI
std or somewhere else?


Thanks a lot in advance!
Paolo

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[PSES] Implantation Cardiac Devices aka Pacemakers EMI

[Paolo Roncone]

Hello everybody

anyone can give infos about interference levels on implantation cardiac
devices, also known as pacemakers ?

1. standard levels of EMI that are allowed. Is IEC/EN 60601-1-2 the only
applicable standard or is there any other more specific for pacemakers?

2. typical and hazardous levels of EMI that are tolerated in field, for
example with cell phone use, but also EMI generated by broadcast antennas,
microwave ovens, and all sorts of electronics around us

Thanks in advance

Paolo

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formats), large files, etc.

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[PSES] ESD generated by rotating turntable

[Paolo Roncone]

Hi everybody

we are considering doing radiated emissions scans during the turntable slow
rotation (about 5min/360deg) in a chamber with turntable flush on the metal
floor and sliding contacts.
The likely issue is ESD generated peaks coming from the sliding contacts.
Anyone has experience with this setup, and in that case, what kind of
mitigation techniques (if any) would be available?

I have direct experience with another chamber with a different kind of
turntable (not flush, , wooden structure raised about 20cm from the ground
plane) and have no issues in the 30MHz to 18GHz range.

Thanks in advance
Paolo

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[PSES] Railway EMC requirements in USA

[Paolo Roncone]

Hi all,

anyone can tell me if there is an EMC standard specific for the railway
environment in the USA, that would cover all hardware used in the railway
environment, both onboard trains and in the adjacent infrastructure in USA?
I mean something equivalent to the EN / IEC standards, but specific to USA:

EN 50121-x / IEC 62236-x
for example:
EN 50121-3-2 / IEC 62236-3-2
EN 50121-4 / IEC 62236-4
EN 50121-5 / IEC 62236-5

I tried the Search box in the FCC Part 47 page, but came up with nothing..
Maybe the FCC accepts compliance to the above mentioned IEC standards ?

Thanks in advance for any feedback !

Best regards

Paolo Roncone

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Re: [PSES] FCC Part 15 - Frequency range of radiated emissions

[Paolo Roncone]

Hello Charlie

Thanks a lot!  Now it's much clearer to me.

Best regards
Paolo

On Tue, Dec 21, 2021 at 9:01 PM Charlie Blackham <
char...@sulisconsultants.com> wrote:

> Paolo
>
>
>
> I would recommend FCC KDB 996369 D04 Module Integration Guide V02
>
>
> https://apps.fcc.gov/oetcf/kdb/forms/FTSSearchResultPage.cfm?id=44637=P
>
>
>
> § 15.33(a) gives you an upper frequency of 12.5 GHz for part 15B “emc”
> emissions
>
> § 15.33(b) gives you an upper frequency of 25 GHz for part 15C “radio
> spurious” emissions
>
>
>
> Best regards
>
> Charlie
>
>
>
> *Charlie Blackham*
>
> *Sulis Consultants Ltd*
>
> *Tel: +44 (0)7946 624317*
>
> *Web: https://sulisconsultants.com/ <https://sulisconsultants.com/> *
>
> Registered in England and Wales, number 05466247
>
>
>
> *From:* Paolo Roncone 
> *Sent:* 21 December 2021 12:24
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* Re: [PSES] FCC Part 15 - Frequency range of radiated emissions
>
>
>
> Hi David
>
>
>
> Thanks for the reply
>
> You mean both EMI and Radio must cover up to 10× BT module frequency?
>
>
>
> Thanks again
>
> Paolo
>
>
>
> On Tue, Dec 21, 2021, 13:05 David Schaefer 
> wrote:
>
> Paolo,
>
>
>
> You are correct. Part 15.33 requires 10x the highest frequency, including
> the radio.
>
>
>
> https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15
>
> *§ 15.33 Frequency range of radiated measurements.*
>
> (a) For an intentional radiator, the spectrum shall be investigated from
> the lowest radio frequency signal generated in the device, without going
> below 9 kHz, up to at least the frequency shown in this paragraph:
>
> (1) If the intentional radiator operates below 10 GHz: to the tenth
> harmonic of the highest fundamental frequency or to 40 GHz, whichever is
> lower.
>
>
>
> Thanks,
>
>
>
>
>
> *David Schaefer**​*
>
> Technical Manager
>
> Element Materials Technology
>
> 9349 W Broadway Ave
>
> Brooklyn Park
>
> ,
>
> MN
>
> 55445
>
> ,
>
> United States
>
> O *+1 612 638 5136* <+1%20612%20638%205136>
>
> ext. 10461
>
> *david.schae...@element.com* 
>
> www.element.com
>
>
> <https://www.linkedin.com/organization-guest/company/element-materials-technology?challengeId=AQFf9AemZ4SobwAAAXOQwivOsnkHiTt2ByoCkOxVQjOGOjRlivicVgYlN1dz5QXjId9bpa0keWzfVxhl8KPj78uD6-S6nfqRsg=e49e0dc0-96a3-2516-27fa-ee2e8c42b177>
>
> <https://twitter.com/ElementTesting/>
>
> <https://elementmaterials.eu.qualtrics.com/jfe/form/SV_3xQqm84s6IydI5D>
>
> *From:* Paolo Roncone [mailto:paoloc...@gmail.com]
> *Sent:* Tuesday, December 21, 2021 5:32 AM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* [PSES] FCC Part 15 - Frequency range of radiated emissions
>
>
>
> *CAUTION:*This email originated from outside of Element Materials
> Technology. *DO NOT* click links or open attachments unless you recognize
> the sender and know the content is safe. Please contact IT Service Desk if
> you are in any doubt about this email.
>
> Hi all,
>
>
>
> an EUT with built-in Bluetooth 2.4 GHz module must be tested - as any
> electrical/electronic equipment sold in the USAm to FCC requirements for
> EMI.
>
>
>
> Questions:
>
> 1. What is the frequency range of EMI radiated emissions for the EUT in
> question?
>
> According to § 15.33 of Part 15:
>
> https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15#15.33
>
>
>
> [image: image.png]
>
> My understanding is that the above mentioned EUT must be tested up to at
> least  10 x 2.4 GHz = 24 GHz for radiated emissions, with the limits
> specified in § 15.109 (Field strength in uVolts/m).
>
>
>
> 2. Does it make any difference wrt question 1 (EMI frequency range), if
> the 2.4G Bluetooth module is already covered by a Declaration of conformity
> or certified according to FCC 47 CFR Part 2 Subpart J (spurious emissions,
> or Radio tests) ?
>
> https://www.ecfr.gov/current/title-47/part-2/subpart-J
>
>
>
> According to a colleague of mine, if the Bluetooth module is already Radio
> tested and/or certified, we may test the subject EUT as an "unintentional
> radiator" (Subpart B), excluding the 2.4 GHz and the 10x rule, but using
> the 5x highest frequency rule for unintentional radiators as the radiated
> EMI range.
>
>
>
> [image: image.png]
>
> I'm not at all convinced..
>
>
>
> I hope someone in this forum can clarify this.
>
>
>
> Thanks a lot in advance and happy holidays!
>
>
>
> Paolo
>
&

[PSES] FCC Part 15 - Frequency range of radiated emissions

[Paolo Roncone]

Hi all,

an EUT with built-in Bluetooth 2.4 GHz module must be tested - as any
electrical/electronic equipment sold in the USAm to FCC requirements for
EMI.

Questions:
1. What is the frequency range of EMI radiated emissions for the EUT in
question?
According to § 15.33 of Part 15:
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15#15.33

[image: image.png]
My understanding is that the above mentioned EUT must be tested up to at
least  10 x 2.4 GHz = 24 GHz for radiated emissions, with the limits
specified in § 15.109 (Field strength in uVolts/m).

2. Does it make any difference wrt question 1 (EMI frequency range), if the
2.4G Bluetooth module is already covered by a Declaration of conformity or
certified according to FCC 47 CFR Part 2 Subpart J (spurious emissions, or
Radio tests) ?
https://www.ecfr.gov/current/title-47/part-2/subpart-J

According to a colleague of mine, if the Bluetooth module is already Radio
tested and/or certified, we may test the subject EUT as an "unintentional
radiator" (Subpart B), excluding the 2.4 GHz and the 10x rule, but using
the 5x highest frequency rule for unintentional radiators as the radiated
EMI range.

[image: image.png]

I'm not at all convinced..

I hope someone in this forum can clarify this.

Thanks a lot in advance and happy holidays!

Paolo

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Re: [PSES] ESD - Floating metal knob, otherwise grounded equipment

[Paolo Roncone]

Hi all,

in these cases (floating metal parts of EUT) we connect the floating part
to Earth Ground with a 2x 470kohm cable similar (or same) as that used for
VCP/HCP.

See IEC/EN 61000-4-2 sec. 7.2.4 Ungrounded Equipment:
"A cable with 470 kohm bleeder resistors, similar to the one used with the
HCP and VCP is the preferred device to remove charges; see 7.2"

Regards
Paolo

On Thu, Mar 12, 2020 at 7:08 PM Paasche, Dieter <
dieter.paas...@christiedigital.com> wrote:

> Hi
>
>
>
> I had a similar situation.  We ended using the alternative test method,
> with just extending the time between discharges. As per IEC 61000-42
> Section 7.4.2.1:
>
>
>
> Therefore as an alternative, the following options may be used:
>
> − the time interval between successive discharges shall be extended to
> the time necessary to allow natural decay of the charge from the EUT;
>
>
>
> Sincerely,
>
>
>
> Dieter Paasche
>
> Senior Product Developer, Electrical
>
> CHRISTIE
>
> 809 Wellington Street North
>
> Kitchener, ON N2G 4Y7
>
> Phone: 519-744-8005 ext.7211
>
> www.christiedigital.com
>
>
>
> This e-mail message (including attachments, if any) is confidential.  Any
> unauthorized use, distribution or disclosure is prohibited.  If you have
> received this e-mail message in error, please notify the sender by reply
> e-mail or telephone and delete it and any attachments from your computer
> system and records.
>
>
>
> *From:* DEREK WALTON <00734758d943-dmarc-requ...@ieee.org>
> *Sent:* Thursday, March 12, 2020 1:31 PM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* Re: [PSES] ESD - Floating metal knob, otherwise grounded
> equipment
>
>
>
> Oh Boy Elliott,
>
>
>
> you’ll get a few answers here, lol.
>
>
>
> My 10 cents is that when you are not discharging each time you are adding
> more and more charge to the isolated control, that eventually will snap
> over At that point you are discharging quite a significantly higher level
> of chart than an individual event.
>
>
>
> I would not call that a realistic “ compliance” test.
>
>
>
> OTOH, if it’s possible that may happen in the real world with an operator
> continually adding charge as they use your EUT, you may want to find a way
> of adding some way to bleed charge over a few seconds.
>
>
>
> Interesting problem, lets see what others say,
>
>
>
> Sincerely,
>
>
>
> Derek
>
> LFResearch and SSCLabs.com
> 
>
>
>
>
>
> On Mar 12, 2020, at 10:53 AM, Elliott Martinson <
> elliott.martin...@subzero.com> wrote:
>
>
>
> Hi Everybody,
>
>
>
> We’re having some disagreements regarding the 61000-4-2 standard. In the
> section “ungrounded equipment”, it states that ungrounded equipment or
> part(s) of equipment shall have the charge removed in between ESD pulses in
> order to not over-test.
>
> We have a product that only fails pre-compliance when repeated ESD pulses
> are applied to a floating metal knob without removing the charge in between
> (eventually there is a second discharge between the knob and the
> enclosure). The product as a whole is “grounded equipment”.
>
> Since the issue only happens when the charge isn’t removed in between
> pulses, is this a pass or a fail?
>
>
>
> Thanks,
>
>
>
> Elliott Martinson
>
> Controls Engineer
>
> Sub-Zero/Wolf
>
> elliott.martin...@subzero.com
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
> 
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
>  http://product-compliance.oc.ieee.org/
> 
>  can be used for graphics (in well-used formats), large files, etc.
>
> Website:  http://www.ieee-pses.org/
> 
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> 

[PSES] test message

[Paolo Roncone]

Test message
Please delete

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Re: [PSES] EN 55032 Testing on Wired Network Port

[Paolo Roncone]

Hello,

according to EN55032/CISPR32, the port you describe is not a wired network
port (sec.3.1.32), rather a signal/control port. (sec.3.1.30).
In Annex A of the standard I don't see tests required on such a port.

Best regards,
Paolo

On Tue, Apr 24, 2018 at 12:18 PM, itl-emc user group 
wrote:

> A device has a wired network port used for de-bugging only.
>
> The port is not used during normal operation of the device.
>
> Any opinions on whether or not this port should be tested?
>
>
>
>
>
> *Regards,*
>
> *David Shidlowsky* | Technical Reviewer
>
> *Address* 1 Bat-Sheva St. LOD
> 
> 7120101 Israel
>
> *Tel* 972-8-9186113 *Fax* 972-8-9153101
>
> *Mail* : dav...@itlglobal.org
>
>
>
> This e-mail message may contain privileged or confidential information.
>
> If you are not the intended recipient, you may not disclose, use,
> disseminate, distribute, copy or rely upon this message or attachment in
> any way. If you received this e-mail message in error, please return by
> forwarding the message and its attachments to the sender.
>
>
>
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
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> emc-p...@ieee.org
>
> All emc-pstc postings are archived and searchable on the web at:
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>
> Attachments are not permitted but the IEEE PSES Online Communities site at
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>
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Re: [PSES] shielded cable connections

[Paolo Roncone]

Hi Doug,

I figure it's the case where you have a high input impedance at the other
end (second box), or just open-ended. In that case the filed to shield
against is prevalent E-field and in that case the shield works pretty much
the same whether it's connected or not at the other end. No need to close a
current loop...

Regards,
Paolo


On Sun, Feb 4, 2018 at 5:06 AM, Doug Smith  wrote:

> Hi All,
>
> I have another riddle for you, this time a video is not needed.
>
> We all know that cable shields need to be connected on both ends to work
> at high frequencies, but do they?
>
> Imagine the case of a source in a metal box driving a shielded cable,
> let's assume it is shielded twisted pair and we are worried about the
> common mode noise on the pair radiating or ESD noise getting in and
> saturating the receiver in the box, exceeding its common mode range. We can
> also assume that the shielded connector on the first metal box is ra eally
> good one with a 360 degree connection to the box. The other end of the
> shielded cable goes to another metal box with a passive circuit inside, say
> a temperature sensor connected to the twisted pair wires. There is one
> special, but not uncommon, case where it does not matter if the shield is
> connected to the second box or not (or even if there is a second box at
> all), it will work in either case! Do you know what that case is?
>
> This is another experiment I do during my classes. I prove the conditions
> needed for the situation above and what the limits are.
>
> I am pretty much a lab rat and I have devised experiments to test the
> limits of most all EE concepts I have learned. I find there is more than
> meets the eye on most every principle. I started doing experiments like
> this around age 11 when I duplicated one of Marconi's experiments to see if
> it really worked, it did, although I suspect the neighbors may have had a
> rough time watching TV that day in 1958. A few years later another
> experiment brought the FCC to my house, but that is another story.
>
> Doug
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
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>
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Re: [PSES] Clicks per CISPR 14-1

[Paolo Roncone]

Agree, but that would be a bit too clear...I think there's an office
somewhere within IEC whose mission is to maximize the intricacy of
something already intricate
An alternative, but maybe too simple and easy, would be to add peak limits
for conducted EMI, higher than QP and Average..

Best regards,
Paolo

On Fri, Nov 10, 2017 at 1:42 PM, John Woodgate <j...@woodjohn.uk> wrote:

> I still say that the wording of 3.3.3 is not as rigorous as it should be.
> It should read something like: "discontinuous disturbance, the amplitude
> of which, measured with the QP receiver, exceeds the quasi-peak limit for
> continuous disturbance, the duration of which is NOT LONGER than 200 ms and
> which is separated from a subsequent disturbance by at least 200 ms,...".
> Without that clarification, if the amplitude exceeds the limit for however
> short a time, the disturbance is a click.
>
> John Woodgate OOO-Own Opinions Only
> J M Woodgate and Associates www.woodjohn.uk
> Rayleigh, Essex UK
>
> On 2017-11-10 12:30, Paolo Roncone wrote:
>
> Hi John,
>
> I see only an upper duration limit (200 msec), because clicks are
> referenced/measured only with a QP detector. See CISPR 14-1 sec.C2.2 "The
> amplitude of the clicks shall be measured with a receiver having a
> quasi-peak detector according to Clause 4 of CISPR 16-1-1:2015."
> So clicks shorter than 1 ms would not be picked up by a QP detector or at
> least never charge it high enough to reach the QP limit...that's my guess.
>
> Best regards,
> Paolo
>
>
> On Fri, Nov 10, 2017 at 12:06 PM, John Woodgate <j...@woodjohn.uk> wrote:
>
>> I think the 1 ms attack time ensures that the click is detected. But
>> there is an issue with the wording. It appears that a 0.5 ms pulse above
>> the QP  limit is a click as defined , but is too short compared with the QP
>> rise-time to show  as exceeding the limit. I think there should be a lower
>> limit of duration as well as the 200 ms upper limit.
>>
>> But this probably doesn't help.
>>
>> John Woodgate OOO-Own Opinions Only
>> J M Woodgate and Associates www.woodjohn.uk
>> Rayleigh, Essex UK
>>
>> On 2017-11-10 10:37, Paolo Roncone wrote:
>>
>> Hi all,
>>
>> Question:
>> IF the EUT Mains conducted emissions Quasi-peak levels are under the
>> CISPR 14-1 Quasi-peak limit (CISPR 14-1 Table 5), when measured with a
>> CISPR 16-1-1 compliant EMI receiver, is the click procedure/assesment
>> deemed to be complied with, or not?
>> In other words, is there in a PASS case still the need to go through the
>> very complicated procedures detailed in sections 4.4, Fig.6 (Flow diagram)
>> and Annex C of CISSPR 14-1 for determining, analyzing, measuring and
>> assessing compliance of clicks ?
>>
>> Going through CISPR 14-1 (2016 ed.):
>> Section 4.4.1 says: "Discontinuous disturbances shall be assessed WHEN
>> they exceed the limits for continuous disturbances,.."
>> Click definition in sec.3.3.3: "discontinuous disturbance, the amplitude
>> of which exceeds the quasi-peak limit for continuous disturbance, the
>> duration of which is NOT LONGER than 200 ms and which is separated from a
>> subsequent disturbance by at least 200 ms,..."
>>
>> Now, the charge/discharge times of a Band B (150k-30M) QP receiver =
>> 1msec/160msec, so a click lasting less than 160msec (see click examples in
>> Fig.2 of CISPR 14-1) yet exceeding the QP limit might NOT be picked up by
>> the QP receiver during a standard mains conducted EMI measurement..here is
>> the origin of my doubts.
>>
>> Thanks in advance for any feedback
>> Paolo
>> -
>> 
>>
>> This message is from the IEEE Product Safety Engineering Society emc-pstc
>> discussion list. To post a message to the list, send your e-mail to <
>> emc-p...@ieee.org>
>>
>> All emc-pstc postings are archived and searchable on the web at:
>> http://www.ieee-pses.org/emc-pstc.html
>>
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>> at http://product-compliance.oc.ieee.org/ can be used for graphics (in
>> well-used formats), large files, etc.
>>
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Re: [PSES] Clicks per CISPR 14-1

[Paolo Roncone]

Hi John,

I see only an upper duration limit (200 msec), because clicks are
referenced/measured only with a QP detector. See CISPR 14-1 sec.C2.2 "The
amplitude of the clicks shall be measured with a receiver having a
quasi-peak detector according to Clause 4 of CISPR 16-1-1:2015."
So clicks shorter than 1 ms would not be picked up by a QP detector or at
least never charge it high enough to reach the QP limit...that's my guess.

Best regards,
Paolo


On Fri, Nov 10, 2017 at 12:06 PM, John Woodgate <j...@woodjohn.uk> wrote:

> I think the 1 ms attack time ensures that the click is detected. But there
> is an issue with the wording. It appears that a 0.5 ms pulse above the QP
> limit is a click as defined , but is too short compared with the QP
> rise-time to show  as exceeding the limit. I think there should be a lower
> limit of duration as well as the 200 ms upper limit.
>
> But this probably doesn't help.
>
> John Woodgate OOO-Own Opinions Only
> J M Woodgate and Associates www.woodjohn.uk
> Rayleigh, Essex UK
>
> On 2017-11-10 10:37, Paolo Roncone wrote:
>
> Hi all,
>
> Question:
> IF the EUT Mains conducted emissions Quasi-peak levels are under the CISPR
> 14-1 Quasi-peak limit (CISPR 14-1 Table 5), when measured with a CISPR
> 16-1-1 compliant EMI receiver, is the click procedure/assesment deemed to
> be complied with, or not?
> In other words, is there in a PASS case still the need to go through the
> very complicated procedures detailed in sections 4.4, Fig.6 (Flow diagram)
> and Annex C of CISSPR 14-1 for determining, analyzing, measuring and
> assessing compliance of clicks ?
>
> Going through CISPR 14-1 (2016 ed.):
> Section 4.4.1 says: "Discontinuous disturbances shall be assessed WHEN
> they exceed the limits for continuous disturbances,.."
> Click definition in sec.3.3.3: "discontinuous disturbance, the amplitude
> of which exceeds the quasi-peak limit for continuous disturbance, the
> duration of which is NOT LONGER than 200 ms and which is separated from a
> subsequent disturbance by at least 200 ms,..."
>
> Now, the charge/discharge times of a Band B (150k-30M) QP receiver =
> 1msec/160msec, so a click lasting less than 160msec (see click examples in
> Fig.2 of CISPR 14-1) yet exceeding the QP limit might NOT be picked up by
> the QP receiver during a standard mains conducted EMI measurement..here is
> the origin of my doubts.
>
> Thanks in advance for any feedback
> Paolo
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
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[PSES] Clicks per CISPR 14-1

[Paolo Roncone]

Hi all,

Question:
IF the EUT Mains conducted emissions Quasi-peak levels are under the CISPR
14-1 Quasi-peak limit (CISPR 14-1 Table 5), when measured with a CISPR
16-1-1 compliant EMI receiver, is the click procedure/assesment deemed to
be complied with, or not?
In other words, is there in a PASS case still the need to go through the
very complicated procedures detailed in sections 4.4, Fig.6 (Flow diagram)
and Annex C of CISSPR 14-1 for determining, analyzing, measuring and
assessing compliance of clicks ?

Going through CISPR 14-1 (2016 ed.):
Section 4.4.1 says: "Discontinuous disturbances shall be assessed WHEN they
exceed the limits for continuous disturbances,.."
Click definition in sec.3.3.3: "discontinuous disturbance, the amplitude of
which exceeds the quasi-peak limit for continuous disturbance, the duration
of which is NOT LONGER than 200 ms and which is separated from a subsequent
disturbance by at least 200 ms,..."

Now, the charge/discharge times of a Band B (150k-30M) QP receiver =
1msec/160msec, so a click lasting less than 160msec (see click examples in
Fig.2 of CISPR 14-1) yet exceeding the QP limit might NOT be picked up by
the QP receiver during a standard mains conducted EMI measurement..here is
the origin of my doubts.

Thanks in advance for any feedback
Paolo

-

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Re: [PSES] FCC testing of intentional vs unintentional radiators

[Paolo Roncone]

Hello Michael,

Thanks for the quick feedback. So, based on it seems my interpretation is
more conservative, but less (not more) right!
Just to make sure we are on the same page, the subject of my query is just
EMC emissions testing, not the radio tests that you mention (conducted
antenna port tests of the transmitter, transmitter emissions tests on 3
channels).
Anyway, my view is that an intentional radiator (radio module), even an
already tested & qualified, built into a new (or not before tested) device
/ combination can behave in unpredictable ways as far as EMC is concerned.
If device A and B are separately EMC-compliant, the A+B combination is not
automatically compliant. This logic is/was used for the CE marking even
combining two EMC-compliant  unintentional radiators. So I see it even more
applicable if one device is an intentional radiator and the A+B should be
completely EMI retested. But again, looks like I'm wrong..

About the frequency range of EMI testing, looking at the example of a
2.4GHz module (test up to 5x 2.4 GHz, not 10x 2.4GHz as I believed) I
understand 15.33 (b), not 15.33 (a) must be applied, because a device with
built-in certified radio module is like an unintentional radiator, right? I
have some troubles understanding it, but seems I have to accept it.

Thanks again!
Paolo



On Fri, Jul 7, 2017 at 2:59 PM, Michael Derby <micha...@acbcert.com> wrote:

> Hello,
>
>
>
> I have added some comments below in red text…..
>
>
>
> Michael.
>
>
>
>
>
> *From:* Paolo Roncone [mailto:paoloc...@gmail.com]
> *Sent:* 07 July 2017 13:44
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* [PSES] FCC testing of intentional vs unintentional radiators
>
>
>
> Dear EMC & Radio experts,
>
>
>
> I have a couple of questions about FCC compliance testing of devices with
> radio modules.
>
> If a device has a built-in radio module, that is already FCC
> tested/certified, how must this device be tested ? Here below two
> interpretations that came up within our company:
>
>
>
> You’ve saved money and effort on certification (because you do not need to
> certify your final radio); and you may have saved ‘some’ money on testing;
> but that doesn’t mean you do not do any additional testing….
>
>
>
> A) the complete device must be tested as an intentional radiator, hence
> FCC Part 15 Subpart C must be followed.
>
> No, you should not need to repeat all the ‘conducted antenna port’ tests
> of the transmitter.
>
> Also, you should not need to repeat all the transmitter emissions tests on
> 3 channels and every modulation, etc.
>
>
>
> You can just verify that the radiated test cases (most likely the
> transmitter spurious emissions) are ‘ok’ in the final installation and that
> you have not accidentally created a non-compliant device.
>
>
>
> B) the device should be tested as unintentional radiator (again if the
> radio module is already certified), hence test to Subpart B.
>
> Yes, you should test it as an unintentional radiator.
>
> And also just check the radiated transmitter emissions, to ensure you
> haven’t created a monster.
>
> (I don’t imagine you would test 3 channels, every modulation, etc., unless
> you find you are very close to the limit).
>
>
>
>
>
> Some significant consequences of the (A) or (B) interpretation are:
>
>
>
> 1.  Applicable emissions limits: Class B only if interpretation (A)
> is correct (§15.207, §15.209) or Class A or B (§15.107, §15.109) if
> interpretation (B) is correct.
>
>
>
> I know what you’re saying, it’s strange.   But, I think you can take some
> guidance from FCC 15.31 (k)
>
>
>
> Also, you are not fully re-testing the transmitter part.   You are
> ensuring that the spurious emissions of the final product in ‘transmit
> mode’ are not over the limits of the final product.   I think it should be
> ok for you to verify your product to the Class A limits, if it’s a Class A
> device.
>
>
>
>
>
> 2.  frequency range of radiated measurements: determined per § 15.33
> (a) if interpretation (A) is correct or § 15.33 (b) if interpretation (B)
> is correct. Within this section, I noticed some difference in FCC
> terminology:
>
> In 15.33 (a) I read "..radio frequency signal generated in the device...",
> "highest fundamental frequency"..
>
> In 15.33 (b) I read "frequency generated or used in the device or on which
> the device operates or tunes (MHz)".
>
>
>
> About the frequency range, here below two additional interpretations that
> came up, also regarding any device with built-in radio module(s) , labeled
> following the previous A and B):
>
>
>
> Regardless of how you read it,

[PSES] FCC testing of intentional vs unintentional radiators

[Paolo Roncone]

Dear EMC & Radio experts,

I have a couple of questions about FCC compliance testing of devices with
radio modules.
If a device has a built-in radio module, that is already FCC
tested/certified, how must this device be tested ? Here below two
interpretations that came up within our company:

A) the complete device must be tested as an intentional radiator, hence FCC
Part 15 Subpart C must be followed.

B) the device should be tested as unintentional radiator (again if the
radio module is already certified), hence test to Subpart B.

Some significant consequences of the (A) or (B) interpretation are:
1. Applicable emissions limits: Class B only if interpretation (A) is
correct (§15.207, §15.209) or Class A or B (§15.107, §15.109) if
interpretation (B) is correct.
2. frequency range of radiated measurements: determined per § 15.33 (a) if
interpretation (A) is correct or § 15.33 (b) if interpretation (B) is
correct. Within this section, I noticed some difference in FCC terminology:
In 15.33 (a) I read "..radio frequency signal generated in the device...",
"highest fundamental frequency"..
In 15.33 (b) I read "frequency generated or used in the device or on which
the device operates or tunes (MHz)".

About the frequency range, here below two additional interpretations that
came up, also regarding any device with built-in radio module(s) , labeled
following the previous A and B):

C) only the non-intentional fundamental frequencies should be considered,
not the radio module(s) operating frequency.

D) any signal generated in the device (including the radio signal, if any,
for example a 2.4 GHz Wi-Fi) must be considered.

I hope to get a clarification about which of the above interpretations
(A,B,C,D) is correct, and possibly get directions to where in the FCC
 rules or publications one can find any unambiguous explanations.

My personal interpretation of the right combination is A/D, but since I got
different opinions I might well be wrong and I decided to seek some
directions within this esteemed forum.

Thanks a lot in advance!
Best regards
Paolo Roncone

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Re: [PSES] DC-power conducted emissions per CISPR11: 2016

[Paolo Roncone]

Hi all,

There's also another question that I would like to clarify. There is a
statement in CISPR 11 (2016) - quoted text below:

"6.2.1 Limits for conducted disturbances
6.2.1.1 General
..
The limits for the LV d.c. power port specified hereafter apply only to
grid connected power convertors (GCPCs) intended for assembly into
photovoltaic power generating systems."

So, it seems that this dc-power CE with 150 Ω  Delta-network would not
apply to medical devices (60601-1-2) and lab equipment (61326-1) unless
they are dc-fed through a photovoltaic power generating system?

Anyway, I still find the CISPR11 (2016) a bit ambiguous, since this
"photovoltaic-only" requirement is not repeated or confirmed later on in
"Table 3 – Limits for conducted disturbances of class A group 1 equipment
measured on a test site (d.c. power port)", except for > 20kVA equipment.
Also, the definition of d.c. power port in sec.3.7:
"port used to connect to a low voltage d.c. power generating system or
energy storage, or to another source/load
Note 1 to entry: Such a system may be for example a photovoltaic or a fuel
cell power generating system, or also a battery." doesn't fully clarify.

So now the question is: is the statement in sec.6.2.1.1 quoted above enough
to exclude anything not powered through photovoltaic power generatic system
from the dc-power conducted emissions with 150 Ω Delta-networks?

Thanks to all who provide feedback!
Paolo

On Mon, Nov 28, 2016 at 11:32 AM, ce-test, qualified testing bv - Gert
Gremmen <g.grem...@cetest.nl> wrote:

> EN 61326-1:2013 makes a date reference to CISPR11:2009+A12010 in its Annex
> ZA
> as well as in article 2.
> Par 7.2 also refers to CISPR11:2009 .
> The limit references for Class A and B do not refer to a dated CISPR11
>
> While I am convinced this is the kind of carefulness that is common in
> standards
> published by IEC and CENELEC, the normative consequences are that the
> latest
> versions apply.
>
> So yes, since the publication date of  June, 26th 2016 this new
> version :
>
> Allows for FAR room measurements
> Prescribes limits for DC in/output ports and defines the delta LISN type
> to be used:
>
> "For   measurements   at   LV   d.c.   power   ports   of   power
>  electronic   equipment,   a   modern
> implementation  of  the  150 Ω  Delta-network  specified  in  CISPR
> 16-1-2  has  been  made available"
>
> Regards,
>
> Ing. Gert Gremmen
> Approvals manager
> 
> 
>
>
> + ce marking of electrical/electronic equipment
> + Independent Consultancy Services
> + Compliance Testing and Design for CE marking
>  according to EC-directives:
> - Electro Magnetic Compatibility 2004/108/EC
> - Electrical Safety 2006/95/EC
> - Medical Devices 93/42/EC
> - Radio & Telecommunication Terminal Equipment 99/5/EC
> + Improvement of Product Quality and Reliability testing
> + Education
>
> Web:www.cetest.nl (English)
> Phone :  +31 10 415 24 26
> ---
> This e-mail and any attachments thereto may contain information
> that is confidential and/or protected by intellectual property rights
> and are intended for the sole use of the recipient(s) named above.
> Any use of the information contained herein (including, but not
> limited to, total or partial reproduction, communication or
> distribution in any form) by persons other than the designated
> recipient(s) is prohibited. If you have received this e-mail in error,
> please notify the sender either by telephone or by e-mail and
> delete the material from any computer.
> Thank you for your co-operation.
>
> From: Paolo Roncone [mailto:paoloc...@gmail.com]
> Sent: Monday 28 November 2016 10:25
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: [PSES] DC-power conducted emissions per CISPR11: 2016
>
> Hi all,
>
> the new 2016 edition of CISPR11 requires DC power ports conducted
> emissions to be done with a "150 Ohm CISPR Delta-network (DC-AN) – see
> CISPR11 ed.6.1 (2016) sec. 6.2.1.3, 7.3.2.3 and Annex I) instead of a
> "standard" 50uH/50ohm V-LISN, used for AC-power conducted emissions and
> also for AC power conducted emissions according to IEC/EN 61000-6-3,
> CISPR22 and other standards.
>
> That means - to my understandiing - that DC-powered Laboratory equipment
> (tested per IEC/EN 61326-1, sec. 7.2) and Medical devices (tested according
> to IEC 60601-1-2 (sec.7.1.1) must be tested with the Delta-LISN for
> DC-power conducted emissions.
>
> Is my understanding correct?
>
> Best regards,
> Paolo
> -
> ---

[PSES] DC-power conducted emissions per CISPR11: 2016

[Paolo Roncone]

Hi all,

the new 2016 edition of CISPR11 requires DC power ports conducted emissions
to be done with a "150 Ohm CISPR Delta-network (DC-AN) – see CISPR11 ed.6.1
(2016) sec. 6.2.1.3, 7.3.2.3 and Annex I) instead of a "standard"
50uH/50ohm V-LISN, used for AC-power conducted emissions and also for AC
power conducted emissions according to IEC/EN 61000-6-3, CISPR22 and other
standards.

That means - to my understandiing - that DC-powered Laboratory equipment
(tested per IEC/EN 61326-1, sec. 7.2) and Medical devices (tested according
to IEC 60601-1-2 (sec.7.1.1) must be tested with the Delta-LISN for
DC-power conducted emissions.

Is my understanding correct?

Best regards,
Paolo

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[PSES] Line-PE AC power Surge per IEC/EN 61000-4-5

[Paolo Roncone]

Hi everyone,


Question:

how to properly (i.e. formally) test the line-to-ground AC power surge per
IEC 61000-4-5 on Class I products, with Line, Neutral, Ground AC input,
 when the following two conditions are met:


1. the Neutral is at 0 VAC, i.e. connected somewhere to the Safety Earth


2. the product can be operated with symmetrical (or unpolarized) AC
plugs/sockets


Condition 2 means that Line and Neutral conductor are equivalent
(symmetrical) inside the product and, therefore, any of the two AC lines
can be connected to the full AC sinusoidal waveform. The L/N configuration
inside the product is symmetrical (or balanced), including fuses on both
L/N conductors.


The above two conditions are met in a significant percent of AC powered
products marketed worldwide, since several countries have symmetrical or
unpolarized AC power outlets and cable cords (the Schuko is one example).
And many AC networks have grounded Neutral line.


May be this question was already addressed somewhere or was already
discussed and I just missed it. In that case, please point me to where I
can find it. And you don't need to read the rest...:-)


The 61000-4-5 rev.3 standard says that the N-PE surge is made without
synchronization if the Neutral is at 0V (N-GND surge is 1/4 of the time
needed vs L-GND surge). This is certainly clear where the AC plug and
outlet is polarized, like in the US and UK, and one can tell which is Line
and which is Neutral in the EUT. Or with 3-Phase products for which the AC
wiring is unequivocal and/or fixed.


However, when the plug/outlet is symmetrical/unpolarized, there is no
univocally identified Neutral in the product; both AC lines can be tied to
the ‘hot’ wire. In this case, I think that the Line-to-GND surge should be
made the same way on both AC lines. In other words, we should test the
L-GND surge with the full AC waveform applied to each of the two AC lines
of the EUT in sequence and with synchronization for both. This is the same
approach used in Safety, where both lines are fused and both should be
tested the same way.

One possible way to properly test the Line-GND surge is to use a Schuko (or
other symmetrical) AC cable/plug to couple the EUT to the Surge CDN, turn
the AC cable Schuko plug 180deg after the first L-GND surge sequence, and
repeat the same test.

In this way both AC lines of the EUT are tested the same way
(symmetrically) for Line to Ground AC surge.

If we just apply the standard procedure, one AC line is fully tested with
AC power and synchronization (0, 90, 180, 270deg) applied, and the other is
not fully tested (no AC voltage, no synchronization).

Any comments, suggestions etc would be much appreciated!


Thanks and best regards,


Paolo

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[PSES] Line-PE AC power Surge per IEC/EN 61000-4-5

[Paolo Roncone]

Hi everyone,

Question:
how to properly (i.e. formally) test the line-to-ground AC power surge per
IEC 61000-4-5 on Class I products, with Line, Neutral, Ground AC input,
 when the following two conditions are met:

1. the Neutral is at 0 VAC, i.e. connected somewhere to the Safety Earth
2. the product can be operated with symmetrical (or unpolarized) AC
lugs/sockets

Condition 2 means that Line and Neutral conductor can be swapped and, as a
consequence, any of the  two AC lines can be connected to the full AC
sinusoidal waveform. The L/N configuration inside the product is
symmetrical (or balanced), including fuses on both L/N conductors.

The above two conditions are met in a significant percent of AC powered
products marketed worldwide, since several countries have symmetrical or
unpolarized AC power outlets and cable cords (the Schuko is one example).
And many AC networks have grounded Neutral line.

May be this question was already addressed somewhere or was already
discussed and I just missed it. In that case please point me to where I can
find it. And you don't need to read the rest...:-)

The 61000-4-5 rev.3 standard says that the N-PE surge is made without
synchronization if the Neutral is at 0V (N-GND surge is 1/4 of the time
needed vs L-GND surge). This is certainly clear where the AC plug and
outlet is polarized, like in the US and UK, and one can tell which is Line
and which is Neutral in the EUT. Or with 3-Phase products for which the AC
wiring is unequivocal and/or fixed.

However, when the plug/outlet is symmetrical/unpolarized, there is no
univocally identified Neutral in the product; both AC lines can be tied to
the ‘hot’ wire. In this case, I think that the Line-to-GND surge should be
made the same way on both AC lines. In other words, we should test the
L-GND surge with the full AC waveform applied to each of the two AC lines
of the EUT in sequence and with synchronization for both. This is the same
approach used in Safety, where both lines are fused and both should be
tested the same way.
One possible way to properly test the Line-GND surge is to use a Schuko (or
other symmetrical) cable and plug to couple the UT to the Surge CDN, turn
the cable plug 180deg after the first L-GND surge sequence, and repeat the
same test.
In this way both AC lines of the EUT are tested the same way
(symmetrically) for Line to Ground AC surge.

Any comments, suggestions etc would be much appreciated!

Thanks and best regards,

Paolo

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[PSES] FCC listing of test facility

[Paolo Roncone]

Hi all,

can anyone help me find the right path to follow for applying for FCC
registration (or listing) of a test site facility ?
I started in www.fcc.gov, but then I got lost and putting test site
listing and the like in the search engine didn't bring up anything useful.
May be the terminology is changed?

Thanks!
Paolo

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RE: EMC EH close field probes / Mindcruiser

[Paolo Roncone (proncone)]

I fully agree with Ken. I have many times used house-made sniffer probes to 
locate sources (and also coupling paths and/or antennas) of radiated emissions. 
They helped me identify and fix a number of compliance issues by pointing to 
the critical elements. 
That is the real plus of these tools. On the other end, there is no point 
trying to correlate near and far-field readings.  

Regards,
Paolo


-Original Message-
From: Ken Javor [mailto:ken.ja...@emccompliance.com] 
Sent: Friday, November 22, 2002 12:24 AM
To: Jim Bacher; Emc-Pstc (E-mail)
Cc: 'tkrze...@genius.org.br'
Subject: Re: EMC EH close field probes / Mindcruiser



My opinion only, curious to see what others say.  The relationship between
what is measured very close to a source and what is measured at three or ten
meters depends very strongly on the efficiency of the radiating element.
For example, if a chip by itself were radiating intensely close-in, you
would get a very different 3 or 10 m signal than if the chip were connected
to a long path on a PCB, and it would radiate still more if that path had a
discontinuity in the ground plane beneath it (assuming a high enough
frequency) and ground bounce then drove an externally connected cable.  So
my opinion, for what it's worth, is that trying to correlate measured
amplitudes close-in with 3 or 10 m signals is not practical in the general
case of troubleshooting a test item.  The probe is useful for locating the
source of an emission.

--
From: Jim Bacher jim.bac...@paxar.com
To: Emc-Pstc (E-mail) emc-p...@majordomo.ieee.org
Cc: 'tkrze...@genius.org.br' tkrze...@genius.org.br
Subject: FW: EMC EH close field probes / Mindcruiser
Date: Thu, Nov 21, 2002, 3:46 PM



 Forwarding for Thomas Krzesaj, please copy Thomas when you respond.

 --
 EMC EH close field probes Message ID: 538546

 Hi,

 I would like to get more informations about close field probes and the
 measurement methods.
 What close field value can we consider as critical ?
 How to interpret the result from the probe ?
 We actually bought Agilent  11941A  11940a probes and FischerCC EH close
 field probes.


 My idea is to get an EMC-scanner like the DetectusAB one
 (http://www.detectus.se/) to get more repeatibility. Can I get some advices?

 Thanks,
 Thomas Krzesaj

 Genius Instituto de Tecnología
 Av. Açaí, 875 Bloco E
 69075-904 Distrito Industrial
 Manaus - Amazonas
 Brasil

 Tel: +55 92 614-6578 / Fax: +55 92 613-3144
 mailto:tkrze...@genius.org.br
 http://www.thomask.fr.st
 http://www.genius.org.br
Posted on Nov 20,2002 at 07:15am






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RE: STP vs FTP Ethernet cables (2)

[Paolo Roncone]

Eric,

this 150 ohm story of STP cables sounds completely new to me. Also, my 
understanding is that both UTP and STP are used for 10bT ethernet.
In the STP definition of IEEE802.3, there is no mention about different 
characteristic impedances from the required 100ohm of 10bT.
Unfortunately I haven't yet received an answer to my original question as 
to how STP cables should be actually made (shielded twisted pairs vs 
overall shield) .
As I already said in previous e-mails, the STP cables that I got look 
pretty much the same as FTP cables, that is they have just an overall 
shield (aluminum foil) around all wires. And they are all declared to be 
100 ohms.


Paolo


At 16:56 06/09/2001 -0400, you wrote:


Paolo,

You may want to check if the FTP cable has a 100 Ohms characteristic
impedance which would make it compatible with interfaces designed for UTP
cable. STP cable is supposed to have a 150 Ohms impedance which is not
compatible with standard 10baseT interfaces which are usually designed for
UTP.

Eric

===

Éric Meunier
Hardware Architect

E-mail: eric.meun...@ca.kontron.com mailto:emeun...@teknor.com

Kontron Communication Inc. (Teknor)
616, rue Curé-Boivin
Boisbriand, Québec
Canada, J7G 2A7

Tel: 1-450-437-4661 ext. 2419
Fax: 1-450-437-8053

Web: http://www.teknor.com http://www.teknor.com



-Original Message-
From:   Paolo Roncone [SMTP:pronc...@cisco.com]
Sent:   Thursday, September 06, 2001 4:18 AM
To: Doug McKean
Cc: EMC-PSTC Discussion Group
Subject:Re: STP vs FTP Ethernet cables (2)

Doug,

I re-paste the first part of the definition in IEEE 802.3 (2000):

1.4.249 shielded twisted-pair (STP)cable: An electrically
conducting cable,comprising one or more ele-
ments,each of which is individually shielded.There may be an overall
shield,in which case the cable is
referred to as shielded twisted-pair cable with an overall shield
(from ISO/IEC 11801:1995)

My understanding is that elements should refer to individual PAIRS
(signal/return), rather than single wires. But - as I said in my previous
e-mail - I'd like to check whether this is put into practice by some
vendors. So far I didn't get any clue on this.
The STP cables that I found so far (form a couple of vendors) have
just an OVERALL shield around all wires, and these are identical to FTP
(Foiled Twisted Pair) cables that are also on the market.
I agree with you, something doesn't sound right...

Paolo


At 09:36 05/09/2001 -0700, Doug McKean wrote:



Paolo Roncone wrote:

 The reason of my inquiry is that we bought samples of
STP and
FTP
 cat.5 cables for 10bT ethernet applications from different
vendors
and to
 our surprise we discovered that both STP and FTP types
have an
 overall (external) shield made of aluminum foil, but no
shields on
individual
 wires or wire couples (as per 802.3 definition above).

Maintaining a characteristic impedence of a twisted pair
by shielding the individual wires of that twisted pair?

Something doesn't sound right.

- Doug McKean



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---
Paolo Roncone
EMC Compliance Engineer - Cisco Photonics Italy
via Philips 12 - Monza (MI) 20052
mailto:pronc...@cisco.com mailto:pronc...@cisco.com
phone: +39 039209 1538
fax: +39 039209 2036



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Technical Committee emc-pstc discussion list.

Visit our web site at:  http

Re: STP vs FTP Ethernet cables

[Paolo Roncone]

Hi Doug,

thanks a lot for your reply. I take this chance to express my appreciation 
for your web page with so many useful articles and suggestions  for people 
in this field (especially the Technical Tidbits).
Yes I know about the potential problems related to the shield, and I also 
know your article.
I used to work with printers (in my previous life as EMC engineer) and I 
discovered many times that the shield of common interface cables  like 
Centronics and RS232 worked more as antennas than as shields.


The reason why we are using a shielded cable for 10bT is that in this way 
we are exempted from GR1089 Intrabuilding Surge requirements. If the cable 
is not shielded we have to test and we should put extra protections on the 
interface, but that would be a problem because one of the affected units is 
bought from an outside vendor and we can no longer get it changed.


In any case, we already tested radiated emissions and immunity and found no 
difference between UTP and FTP (that means the ground to which the shield 
is connected is clean enough RF-wise).
So, being stuck with shielded cables we are considering STP vs FTP, and I 
already told the rest of the story...


Paolo



At 11:37 03/09/2001 -0700, you wrote:

Hi Paolo,

I worked for a few years in the part of Bell Labs that was involved with
networking cable systems several years ago. I am suspicious of foil
shielded cables as it is difficult to properly terminate the foil shield
(360 degrees). I have had a foil shield crack and split if the cable is
flexed very much.

On a related topic, a good UTP (unshielded twisted pair) system can have
lower emissions and higher immunity than most shielded systems. The
interface design is not hard to do to make this happen. I have seen
cases where the presense of the shield causes immunity problems because
a large noise current lands on the chassis of the data equipment. It
there are slits and holes in the chassis (back of a PC?) problems
result. Take a peek at the paper:

http://www.dsmith.org/pdf/roma94.pdf

which I authored several years ago and presented at the EMC Roma
conference. In that paper a couple of commercial STP systems were
compared with a good UTP system at a test lab in Switzerland. The UTP
system won hands down on both emissions and immunity! The presense of a
shield, by itself, does not guarantee good performance. I seem to
remember also that the shielded systems had higher losses for signal
transmission than UTP which resulted in shorter permissable cable
lengths.

Paolo, we can go offline if you want to discuss more details. Either
call or email me.

Doug

Paolo Roncone wrote:

 Hi all,

 anybody out there can explain the difference between FTP (Foiled
 Twisted Pair) and STP (Shielded Twisted Pair) cables used for Ethernet
 links.
 In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP
 (herebelow in copied and pasted from the standard - page 28):
 In a vendor's catalog, I found a definition of FTP as

 1.4.249 shielded twisted-pair (STP)cable: An electrically conducting
 cable,comprising one or more ele-
 ments,each of which is individually shielded.There may be an o erall
 shield,in which case the cable is
 referred to as shielded twisted-pair cable with an o erall shield
 (from ISO/IEC 11801:1995).Speci .cally
 for IEEE 802.3 100BASE-TX,150 . balanced inside cable with performance
 characteristics speci .ed to
 100 MHz (i.e.,performance to Class D link standards as per ISO/IEC
 11801:1995).In addition to the
 requirements speci .ed in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and
 25 provide additional perfor-
 mance requirements for 100BASE-T operation o er STP.

 The reason of my inquiry is that we bought samples of STP and FTP
 cat.5 cables for 10bT ethernet applications from different vendors and
 to our surprise we discovered that both STP and FTP types have an
 overall (external) shield made of aluminum foil, but no shields on
 individual wires or wire couples (as per 802.3 definition above).

 Any inputs, suggestions etc. would be appreciated.

 Paolo

 
---

 Paolo Roncone
 EMC Compliance Engineer - Cisco Photonics Italy
 via Philips 12 - Monza (MI) 20052
 mailto:pronc...@cisco.com
 phone: +39 039209 1538
 fax: +39 039209 2036

--
---
___  _   Doug Smith
 \  / )  P.O. Box 1457
  =  Los Gatos, CA 95031-1457
   _ / \ / \ _   TEL/FAX: 408-356-4186/358-3799
 /  /\  \ ] /  /\  \ Mobile:  408-858-4528
|  q-( )  |  o  |Email:   d...@dsmith.org
 \ _ /]\ _ / Website: http://www.dsmith.org
---



---
Paolo Roncone
EMC Compliance Engineer

STP vs FTP Ethernet cables (2)

[Paolo Roncone]

This is a re-post with some corrections plus added some letters that got 
lost on the way from the .pdf file.

Sorry for the inconvenience.


Hi all,

anybody out there can explain the difference between FTP (Foiled Twisted 
Pair) and STP (Shielded Twisted Pair) cables used for Ethernet links.
In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP 
(herebelow in copied and pasted from the standard - page 28):


1.4.249 shielded twisted-pair (STP)cable: An electrically conducting 
cable,comprising one or more ele-
ments,each of which is individually shielded.There may be an overall 
shield,in which case the cable is
referred to as shielded twisted-pair cable with an overall shield (from 
ISO/IEC 11801:1995).Specifically
for IEEE 802.3 100BASE-TX,150 ohm balanced inside cable with performance 
characteristics specified to
100 MHz (i.e.,performance to Class D link standards as per ISO/IEC 
11801:1995).In addition to the
requirements specified in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and 25 
provide additional perfor-

mance requirements for 100BASE-T operation over STP.

The reason of my inquiry is that we bought samples of STP and FTP cat.5 
cables for 10bT ethernet applications from different vendors and to our 
surprise we discovered that both STP and FTP types have an overall 
(external) shield made of aluminum foil, but no shields on individual wires 
or wire couples (as per 802.3 definition above).


Any inputs, suggestions etc. would be appreciated.

Paolo

---
Paolo Roncone
EMC Compliance Engineer - Cisco Photonics Italy
via Philips 12 - Monza (MI) 20052
mailto:pronc...@cisco.com
phone: +39 039209 1538
fax: +39 039209 2036

STP vs FTP Ethernet cables

[Paolo Roncone]

Hi all,

anybody out there can explain the difference between FTP (Foiled Twisted 
Pair) and STP (Shielded Twisted Pair) cables used for Ethernet links.
In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP 
(herebelow in copied and pasted from the standard - page 28):

In a vendor's catalog, I found a definition of FTP as

1.4.249 shielded twisted-pair (STP)cable: An electrically conducting 
cable,comprising one or more ele-
ments,each of which is individually shielded.There may be an o erall 
shield,in which case the cable is
referred to as shielded twisted-pair cable with an o erall shield (from 
ISO/IEC 11801:1995).Speci .cally
for IEEE 802.3 100BASE-TX,150 . balanced inside cable with performance 
characteristics speci .ed to
100 MHz (i.e.,performance to Class D link standards as per ISO/IEC 
11801:1995).In addition to the
requirements speci .ed in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and 25 
provide additional perfor-

mance requirements for 100BASE-T operation o er STP.

The reason of my inquiry is that we bought samples of STP and FTP cat.5 
cables for 10bT ethernet applications from different vendors and to our 
surprise we discovered that both STP and FTP types have an overall 
(external) shield made of aluminum foil, but no shields on individual wires 
or wire couples (as per 802.3 definition above).


Any inputs, suggestions etc. would be appreciated.

Paolo

---
Paolo Roncone
EMC Compliance Engineer - Cisco Photonics Italy
via Philips 12 - Monza (MI) 20052
mailto:pronc...@cisco.com
phone: +39 039209 1538
fax: +39 039209 2036

Cable layout per GR1089

[Paolo Roncone]

Hi,

anyone can get me clarifications on the cable layout for radiated immunity 
and emissions testing per GR1089 with overhead cable trays (ref. fig.3-13 ) ?
In fig.3.13 + sections 3.4.6 and 3.5.5 of GR1089 I don't see any specified 
length of the horizontal section projecting out of the EUT boundaries.
Also I don't see any indication thereof in ANSI C63.4 (fig.10), while 
CISPR22/EN55022 (fig.13) specifies MINIMUM 20 cm of horizontal length.



Thanks,

Paolo

Re: Clock dithering

[Paolo Roncone]

Hi Cyril,

I have a very good (EMC-wise) experience with clock dithering.
I started using the Spread Spectrum Clock Generation (SSCG) technique 
(patented by Lexmark) in 1995 when I worked for my previous company.
We made printers and one of our main customers was IBM. They pushed us to 
use an SSCG chip (there was only one licenced vendor at that time) in order 
to get our impact printers pass class B emissions limits (CISPR22 and FCC 
part 15) with the required guardband (IBM is very strict on EMC).
The SSCG worked great on reducing radiated emissions of clock and clock 
related signals (data, control etc.). We gained in the range of 4 to 10+ 
dBs (depending on the frequencies), plus we managed to make a big cost 
reduction by switching from 4-layer to 2-layer motherboards with the 
addition of SSCG and careful PCB layout (also note we had no shielding over 
our electronics).
Before SSCG we were just failing class B by 2-3 dB (with 4-layer boards). 
After the SSCG chip was embedded in our motherboards we were safely belowe 
the limits. Also we passed class B on models with coax/twinax interface 
boards (typically class A products). The clock frequencies running on our 
electronics were in the range 20-35 MHz.


Basically the SSCG slowly modulates the main clock oscillator frequency. 
Slowly means that the modulating periodis  over many (several 
hundreds) clock cycles. The total amount of spread can be varied between a 
few tens of a percent to a few percents of the clock frequency (in our 
application we used +/-2.5% deviation).
The higher the frequency deviation, the higher the amount of spreading and 
the consequent attenuation of peak emission levels because (as you say) 
energy is spread over the spectrum. So the minimum bandwidth of the 
spreaded clock (fundamental frequency) is wider than the standard 120 kHz 
resolution BW of EMI receivers specified for radiated emission tests. Also 
key is the wave shape of the modulating function of the clock signal. 
That's what the Lexmark patent covers. The patented waveshape is the so 
called Herschey kiss or Lexmark shape, that produces a FLAT spectral 
profile. By contrast, any sinusoidal or triangular modulating waveform 
spreads the spectrum of clock fundamental + harmonics but the resulting 
shape has two peaks (at the min/max frequencies of the spread).


PLUS : big EMI reductions can be achieved without compromising system 
performance (clock speed/rise-fall times are unaltered). This does not mean 
that you don't need to control EMI. You just have many more chances to 
pass. Without optimized board layout we would have failed class B even with 
the dithered clock !


CONS: EMC-wise, increased chance of exciting resonant structures 
(associated with cables, PCB's geometries and  other mechanical parts) 
because the emissions cover a wider frequency spectrum. Also the clock 
jitter tolerances must be thoroughly checked in order to adjust the amount 
of deviation allowed. In some applications (ex. clocks driving video 
signals as in scanners or laser printers) even the minimum clock jittering 
is not allowed so clock dithering cannot be used.


As for interference to broadband receivers (like TV equipment) I remember a 
Lexmark study published a few years ago that showed no increased 
interference from modulated clocks vs unmodulated clocks (there was also a 
related discussion in this forum a while ago). I honestly don't know if 
anything new came up recently.


Cheers,

Paolo



At 14:16 15/06/2001 -0400, Binnom, Cyril A wrote:


Resending due to no subject listed in first e-mail.

  -Original Message-
 From: Binnom, Cyril A
 Sent: Friday, June 15, 2001 10:14 AM
 To:   'emc-pstc'
 Cc:   McBride, James; Wismer, Sam; Massey, Doug C.; Davis, Brett A.
 Subject:

 Group,

 I am experiencing a EMI failure during testing and it has been isolated to
 the processor board in which the fundamental frequency is 66.6 MHz the 3rd
 harmonic that is our failure frequency is 199.8 MHz. We consulted the
 manufacturer of the board and they have come up with a spectrum
 spreading application for me to try. As I understand it, these type of
 applications work by essentially jittering the clock frequency in order to
 spread the energy over a wider band of frequencies. Thus the level at any
 particular frequency is reduced even though the overall amount of energy
 radiated is the same. The file they are sending me is a test application.
 If it works well enough to get the unit to pass test, they have the
 ability to enable the same application in the BIOS so it is always
 running.

 Does anyone have any experience using this type of application? Any
 opinions on its validity? To those that can attest to its validity, any
 pros or cons to the use of this application?

 Regards,

 Cyril A. Binnom Jr.
 EMI/EMC Approvals Engineer
 LXE, Inc.
 (770) 447-4224 Ext. 3240
 (770) 447-6928 Fax
 binno...@lxe.com



---
This 

Re: Clock dithering

[Paolo Roncone]

Hi Cyril,

I have a very good (EMC-wise) experience with clock dithering.
I started using the Spread Spectrum Clock Generation (SSCG) technique 
(patented by Lexmark) in 1995 when I worked for my previous company.
We made printers and one of our main customers was IBM. They pushed us to 
use an SSCG chip (there was only one licenced vendor at that time) in order 
to get our impact printers pass class B emissions limits (CISPR22 and FCC 
part 15) with the required guardband (IBM is very strict on EMC).
The SSCG worked great on reducing radiated emissions of clock and clock 
related signals (data, control etc.). We gained in the range of 4 to 10+ 
dBs (depending on the frequencies), plus we managed to make a big cost 
reduction by switching from 4-layer to 2-layer motherboards with the 
addition of SSCG and careful PCB layout (also note we had no shielding over 
our electronics).
Before SSCG we were just failing class B by 2-3 dB (with 4-layer boards). 
After the SSCG chip was embedded in our motherboards we were safely belowe 
the limits. Also we passed class B on models with coax/twinax interface 
boards (typically class A products). The clock frequencies running on our 
electronics were in the range 20-35 MHz.


Basically the SSCG slowly modulates the main clock oscillator frequency. 
Slowly means that the modulating periodis  over many (several 
hundreds) clock cycles. The total amount of spread can be varied between a 
few tens of a percent to a few percents of the clock frequency (in our 
application we used +/-2.5% deviation).
The higher the frequency deviation, the higher the amount of spreading and 
the consequent attenuation of peak emission levels because (as you say) 
energy is spread over the spectrum. So the minimum bandwidth of the 
spreaded clock (fundamental frequency) is wider than the standard 120 kHz 
resolution BW of EMI receivers specified for radiated emission tests. Also 
key is the wave shape of the modulating function of the clock signal. 
That's what the Lexmark patent covers. The patented waveshape is the so 
called Herschey kiss or Lexmark shape, that produces a FLAT spectral 
profile. By contrast, any sinusoidal or triangular modulating waveform 
spreads the spectrum of clock fundamental + harmonics but the resulting 
shape has two peaks (at the min/max frequencies of the spread).


PLUS : big EMI reductions can be achieved without compromising system 
performance (clock speed/rise-fall times are unaltered). This does not mean 
that you don't need to control EMI. You just have many more chances to 
pass. Without optimized board layout we would have failed class B even with 
the dithered clock !


CONS: EMC-wise, increased chance of exciting resonant structures 
(associated with cables, PCB's geometries and  other mechanical parts) 
because the emissions cover a wider frequency spectrum. Also the clock 
jitter tolerances must be thoroughly checked in order to adjust the amount 
of deviation allowed. In some applications (ex. clocks driving video 
signals as in scanners or laser printers) even the minimum clock jittering 
is not allowed so clock dithering cannot be used.


As for interference to broadband receivers (like TV equipment) I remember a 
Lexmark study published a few years ago that showed no increased 
interference from modulated clocks vs unmodulated clocks (there was also a 
related discussion in this forum a while ago). I honestly don't know if 
anything new came up recently.


Cheers,

Paolo



At 14:16 15/06/2001 -0400, Binnom, Cyril A wrote:


Resending due to no subject listed in first e-mail.

  -Original Message-
 From: Binnom, Cyril A
 Sent: Friday, June 15, 2001 10:14 AM
 To:   'emc-pstc'
 Cc:   McBride, James; Wismer, Sam; Massey, Doug C.; Davis, Brett A.
 Subject:

 Group,

 I am experiencing a EMI failure during testing and it has been isolated to
 the processor board in which the fundamental frequency is 66.6 MHz the 3rd
 harmonic that is our failure frequency is 199.8 MHz. We consulted the
 manufacturer of the board and they have come up with a spectrum
 spreading application for me to try. As I understand it, these type of
 applications work by essentially jittering the clock frequency in order to
 spread the energy over a wider band of frequencies. Thus the level at any
 particular frequency is reduced even though the overall amount of energy
 radiated is the same. The file they are sending me is a test application.
 If it works well enough to get the unit to pass test, they have the
 ability to enable the same application in the BIOS so it is always
 running.

 Does anyone have any experience using this type of application? Any
 opinions on its validity? To those that can attest to its validity, any
 pros or cons to the use of this application?

 Regards,

 Cyril A. Binnom Jr.
 EMI/EMC Approvals Engineer
 LXE, Inc.
 (770) 447-4224 Ext. 3240
 (770) 447-6928 Fax
 binno...@lxe.com



---
This 

Ethernet baluns

[Paolo Roncone]

Hi everyone:

I'm looking for a passive (no ac/dc power supply needed) balun to convert 
from an Ethernet 10b2 (unbalanced coax 50 ohm) to an Ethernet 10bT 
(balanced, twisted pair, UTP, 100 ohm).
Anyone knows if this kind of box exists ? So far I came up with a perfect 
match, but for the impedance of the coax connector (75 ohms instead of 50 
ohms).
We need this in order to improve the EMC behavior of the 10b2 Ethernet that 
we have to live with (you bet it's a real damn pain in the neck EMC-wise !!!).


Thanks
Paolo


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RE: Site Correlation

[Paolo Roncone]

Good point Lothar,
it was about time that the original technical grounds and limitations of CE 
method were brought up.
Just one additional point: with the ever increasing operating frequencies 
of many electronic products, box and/or PCB level radiation is getting more 
and more important vs cable radiation (and as a by-product cable layout 
should weigh less in measurement uncertainty).


One last point: I was a bit perplexed by the way this thread shifted from 
the original question. I myself stepped in early with a question about 
fully-anechoic vs semi-anechoic pre-compliance chambers but then the 
subject switched to the CE vs RE issue and nobody gave a damn about me..


Paolo


At 11:28 AM 1/16/01 -0800, Lothar Schmidt wrote:


I have the feeling that different issues are mixed in this discussion.

supposed that CE vs. RE methods is the issue, I can give you some historical
information. The CE method is used as a simplified method for the radiation
of the tested device.
The CE method was used for devices which have to met several conditions
1. the cable length was long compared to the size of the device ( the
longest side should not be longer than 80 cm)
2. the number of cable is limited to one or maximum 2 cables.
3. the frequencies produced in the equipment have to be low due the
limitation of the method to 300 MHz.

Reasons for
1. the cable should be the preferred antenna for the emission of the device
2. You can only made a correlation between CE and RE if all the radiated by
the one cable. You will not be able to calculate the sum of different cables
because you don't know the relation.
3. The method is only specified up to 300 MHz. At higher frequencies the
cables act different.

This method was used e. g. simple household devices and tools.

I don't know if I got the real point because I didn't followed the whole
discussion, but perhaps I can put in some more ideas.

Best Regards

Lothar Schmidt
Technical Manager EMC/Bluetooth,
BQB, Competent Body
Cetecom Inc.
411 Dixon Landing Road
Milpitas, CA 95035
Phone: +1 (408) 586 6214
Fax:   +1 (408) 586 6299


-Original Message-
From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Tuesday, January 16, 2001 7:45 AM
To: Ralph Cameron; chris maxwell; dan kwok
Cc: EMC-PCST (E-mail)
Subject: Re: Site Correlation



I am getting the distinct (but uncomfortable) feeling that was is being
discussed by a lot of people on this thread is that cable cm CE need to be
controlled to prevent either crosstalk to another bundle, or to prevent
interference to equipment connected to the same bundle.  Am I interpreting
these comments correctly?  For the record, I don't believe either of these
is a real issue.  The only traditional, and in my experience, legitimate
purpose of controlling cable cm CE is to prevent coupling to the antennas
connected to radio receivers.

Ken Javor

--
From: Ralph Cameron ral...@igs.net
To: Chris Maxwell chris.maxw...@gnnettest.com, Ken Javor
ken.ja...@emccompliance.com, dan kwok dk...@intetron.com
Cc: EMC-PCST \(E-mail\) emc-p...@majordomo.ieee.org
Subject: Re: Site Correlation
Date: Tue, Jan 16, 2001, 9:01 AM


 What it boils down to Chris is the lack of immunity of the consumer
 equipment contributes to degradation of the intended function. Once the
 undesired energy reaches the consumer device there's no way to get rid of
 it. The rememdy is to prevent it from reaching the device and or isolating
 it from the source.

 At one time injection clamps were used for immunity testing- are they
still?

 Ralph Cameron


 - Original Message -
 From: Chris Maxwell chris.maxw...@gnnettest.com
 To: 'Ralph Cameron' ral...@igs.net; Ken Javor
 ken.ja...@emccompliance.com; dan kwok dk...@intetron.com
 Cc: EMC-PCST (E-mail) emc-p...@majordomo.ieee.org
 Sent: Tuesday, January 16, 2001 8:38 AM
 Subject: RE: Site Correlation


 Seems like this thread has gotten into how to correlate common mode cable
 currents with their expected radiated emissions.

 For those interested, Fischer Custom Communications makes coupling and
 measuring clamps which can measure common mode surface currents on cables
 and surfaces.  They used to publish some application notes regarding the
 usage of their clamps to measure surface/cable currents and how to
 correlate
 them to expected radiated emissions.

 I read them a couple of years ago.  I never bought the clamps, but it did
 make for some very good technical reading.

 I do know of a table top power supply manufacturer that uses this method
 almost exclusively.  They send one power supply to a calibrated OATS.
 They
 get it to pass.  Then, when the sample comes back to the factory, they
 take
 clamp measurements of the common mode currents of the AC input and DC
 output
 cable.

 They then model the power supply as a dipole antenna with the AC input
 cable
 and DC output cable being the two poles.

 For future power supplies, they then use the clamp method in-house to
 measure the cable 

RE: Site Correlation

[Paolo Roncone]

Interesting... we are gojng to set-up a pre-compliance semi-anechoic 
chamber for 3 m measurements (mainly radiated emissions) on telecom 
products and we'll need to correlate it with a 10m full-compliant chamber.
Our DUT's are typically sub-rack or 2m+ high telecom racks. Your idea of 
considering a fully anechoic vs semi-anechoic chamber sounds pretty 
interesting to me. We are limited in height to about 2 m (chamber internal 
space) so we are not able to maximize with a limited antenna height 
scanning. So rotating the EUT and adding 6 dB for the missing in-phase 
floor reflection sounds reasonable... unless I'm missing something
I heard some time ago about a correlation study btw fully- and 
semi-anechoic rooms performed by CISPR subcommittee A and if I remember 
well they came up with disturbing increased uncertainties / variancies 
related to cables layout due to missing coupling between cables and ground 
floor (image theory and stuff...).

Anyone who can fill me in more with this would be welcome !

Regards,

Paolo Roncone


At 10:37 AM 1/11/01 -0500, David Heald wrote:

Hello all
   There are a few variables that need to be addressed to answer this 
question.  The first is the nature of the chamber.  My reply will assume 
that this is a fully anechoic chamber (walls, floor, and ceiling all 
lined with absorber material).  Otherwise, all bets are off due to the 
unpredictable reflections from the surfaces in the chamber.  In a chamber 
this size, I will also assume that the antenna height is fixed, or at 
least not very adjustable.  Given a fully anechoic room and a fixed 
antenna height, theoretically you should be able to extrapolate (about 10 
dB from 1 to 3 meters antenna distance and another 10 dB from 3 to 10 
meters) with only about 6 dB of uncertainty.  In practice this is usually 
accurate but real world conditions have slightly more uncertainty so 10 
dB is a fairly safe margin to use.
   A few things to keep in mind:  if the chamber is only semi-anechoic 
(walls and ceiling lined) you will have more uncertainty due to possible 
cancellation due to floor reflections.  At this point, relative change or 
frequency identification is about the only thing the chamber is good 
for.  Also, near field readings can be significantly different from 
far-field readings.  If you come up with marginal near field readings, be 
prepared for the worst when you take 10m readings.  Finally, be sure to 
check BOTH antenna polarities.


I hope this helps

Usual employer disclaimer . . .


David Heald
Senior EMC Engineer/
Product Safety Engineer

Curtis-Straus LLC NRTL
Laboratory for NEBS, EMC, Safety, and Telecom








Voice:978.486.8880x254   Fax:978.486.8828
http://www.curtis-straus.comwww.curtis-straus.com

Tudor, Allen wrote:




Greetings:

What's the best way to correlate a pre-compliance chamber (smaller than a 3m
chamber) to a 10m anechoic chamber?  Should I use a signal generator and
antenna or should I use a comb generator?

Would the answer be different if I were correlating the pre-compliance
chamber to an OATS?

Thanks in advance.


Allen Tudor, Compliance Engineer
ADC DSL Systems Inc.
6531 Meridien Dr.
Raleigh, NC  27616
phone: 919.875.3382
email: mailto:allen_tu...@adc.comallen_tu...@adc.com


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R: Component Qualification

[Paolo Roncone]

Dear Koh:

My opinion is that first you should distinguish between active components (like 
oscillators, but also EMC sensitive parts like microprocessors, memories, 
ASIC's and all fast logic IC's) and passive components (like ferrites).
For the first type, in any case you cannot be enough confident about the 
goodness of second source components without testing.  My experience tells me 
that even same vendor, same-all active components can have significant 
spreads in EMC behavior, because of the parasitic (and often uncontrolled) 
parameters involved. That is especially true for radiated emissions. I remember 
having sometimes nasty surprises when testing products with identical 
components that were just from different mfg batches. One typical example is 
the edge rate (rise/fall times) that is usually specified relative to maximum 
values but not at all for minimum values. So even if the edge rates in the data 
sheets are identical, you can get different EMI behaviors (even from the same 
vendor).
As for passive components (like ferrite beads, resistors, capacitors etc. used 
to filter noise at the PCB level) I think you can go with just looking at the 
data sheet, but I would recommend that you test if there is even a small 
difference in impedance curves (that could trigger unexpected resonances or 
change the emissions profile). 
Whenever the purchase dept guys approach me with second (or third) source 
EMI-sensitive components (like those that you mention) I follow these steps:
1. First screening based on data sheet (example impedance curves for ferrites). 
If they at least don't match those of the already qualified/tested components 
they are discarded. If they look the same or even better (example: higher 
impedance for ferrites or higher resonance frequency for capacitors) I go on to 
step 2.
2. Test 

Just my opinion...
Hope this helps.

Paolo

-Messaggio originale-
Da: Koh Nai Ghee [SMTP:koh...@cyberway.com.sg]
Inviato:martedì 19 settembre 2000 22.48
A:  EMC-PSTC
Oggetto:Component Qualification


Group,
Can anyone advice on any guide for checking/qualifying second source
component, such as crystal, oscillator  ferrite bead, mounted on
product is still meeting the emission limits?

We are manufacturer of pheripherals cards. Some card has crystal and/or
oscillator for digital circuitry. Ferrite bead are used too.
As these component will affect the final product EMI level, therefore
some qualification/guide in terms of EMI must be considered when
qualifying second source component.
These components are used in lots of product that we made, it would be
costly to perform scan for every model.
Every product are tested and pass EMI with initial source components.

Can we just made a comparison of the specification of the first source
compnent with this second source?
If yes, what are the crucial specs/information that must meet the first
source component?
For crystal/oscillator, beside the Frequency stability  tolerance
specs, what other item is crucial.
For Ferrite bead, impedance curve, what other item is crucial.

If happens that some specs are slightly out, e.g. 2nd source crystal are
having 5PPM more than initla source crystal,
Can we make use of the product passing margin, say 3dB, and do some
calculation to confidently say that the second source component on the
card is still EMI compliance. Likewise for oscillator and ferrite bead.
If yes, could you advice on an example of such calculation.

Many thanks in advance for the replies.

Regards
Koh


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R: R: Conducted Emissions on Telecom Ports

[Paolo Roncone]

Ken and Cortland and many others that entered this subject : 

First, radiated emissions are best measured with radiated (not conducted) 
measurements. There is a correlation between CM currents and RE but that's not 
all (resonances, cable layout  etc. count a lot). 
Second, you say that CE are easier to measure than RE ? Agree if you talk about 
emissions on AC power cords (as per CISPR22 and FCC part 15). But for the new 
requirements on telecom ports, I suggest you to take a look at the new (3.ed.) 
CISPR22 or EN55022 (sec. 9.5 + annex C.1) and may be you change your opinion !
Radiated emissions above 30 MHz are already covered.
If you wanna take care of lower frequencies ( 30 MHz) take a loop antenna 
(remember  the old VDE rules ?) and measure radiated H-fields with your system 
in the same (typical) layout used for the higher frequencies (with whatever 
cables you specify, UTS, STP etc.). I am sure that is much quicker, easier and 
repeatable than all the nonsense (ISNs, CDNs, clamps, current probes, 
capacitive probes, ferrites, 150 ohm resistors, signal generators, impedance 
measurements, voltage measurements, current measurements and more) in the new 
CISPR22. 
As for the question of outside world, I think in this ever more connected 
world the border line between INSIDE and OUTSIDE is getting more and more 
blurred, BUT I also think that a line must be drawn by the standard bodies, 
otherwise it's gonna really get too much confusing  (hope some CISPR/CENELEC 
member gets it). 
If we spill over the line (office, floor, building... whatever), emissions 
requirements  are triggered. But within that line it's to be considered an 
intra-system (what's the system ? that's another good question to be settled) 
interference potential and the manufacturer should take care of it without need 
of enforcement because he has all the interest in making a product (system) 
that works properly and reliably.
 
One last point: based on David Sterner's note, looks to me that North America 
has a pretty extensive Ethernet and-the-like network. I honestly don't know if 
the FCC has already enforced emission limits on LAN ports. Anyway, based on 
David's note looks like there are no complaits of interference with TV and 
telephones. And please note, this is the very bottom line of it. Emission 
limits should be intended to protect public services ... and physics works the 
same on both sides of the Atlantic... or not 

My personal opinion ...

Paolo






-Messaggio originale-
Da: Ken Javor [SMTP:ken.ja...@emccompliance.com]
Inviato:giovedì 7 settembre 2000 18.43
A:  Paolo Roncone; 'eric.lif...@ni.com'
Cc: 'emc-p...@ieee.org'
Oggetto:Re: R: Conducted Emissions on Telecom Ports

Although I don't work commercial EMC on a regular basis and I do not know 
over what frequency range the telecom port CE are controlled (I assume here
150 kHz - 30 MHz), I believe that there is a mistaken premise inherent in
the comments to which I am responding.  The purpose of controlling common
mode CE on any port is not to protect equipment at the other end of the
cable, or other co-sited cables, but rather to control radiated emissions in
a frequency range in which CE are easier to measure than RE.  In turn, the
purpose of controlling RE is to protect broadcast radio reception.
--
From: Paolo Roncone paolo.ronc...@compuprint.it
To: 'eric.lif...@ni.com' eric.lif...@ni.com
Cc: 'emc-p...@ieee.org' emc-p...@ieee.org
Subject: R: Conducted Emissions on Telecom Ports
Date: Thu, Sep 7, 2000, 9:45 AM



 Hi Eric,

 I 100% agree with you. The scope of emissions standard should be to protect
 the outside (i.e. public) environment from interference. So only ports
 that connect to public telecom networks should be covered by the standard.
 The problem is (as pointed out in one of the previous notes) that the new
 CISPR22 / EN55022 standard clearly includes LAN ports in the definition of
 telecommunications ports (section 3.6) no matter if they connect to the
 outside world or not.

 Regards,
  
 Paolo Roncone
 Compuprint s.p.a.
 Italy



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R: Immunity Testing to EN55024

[Paolo Roncone]

Hi,
The test level specified in EN55024 is 3 V/m unmodulated, rms (Erms).
You calibrate the forward power in order to get 3 V/m rms unmodulated. 
At this point the peak value of the unmodulated sinusoidal field is Epk = Erms 
=  3 V/m.
When you test, you apply 80% AM to this wave. At this point is the rms value 
still 3 V/m ? (yes according to Ed's answer).
The peak values are changed: AM Epk = (1+0.8) x Epk = 1.8 Epk = 7.6 V/m.
Where Epk is the peak value of unmodulated carrier (= sqrt(2) x Erms = 4.24 
V/m).
AM Epk-pk (peak-to-peak value of 80% AM field) = 2 x sqrt(2) x 1.8 x Erms = 
5.09 x Erms = 15 V/m. The rms value (3 V/m) is most significant, but the peak 
value changes a lot !  

my 2 cents


Paolo Roncone
Compuprint s.p.a.
Italy

 

-Messaggio originale-
Da: Gary McInturff [SMTP:gary.mcintu...@worldwidepackets.com]
Inviato:mercoledì 6 settembre 2000 23.47
A:  'Bronaugh, Edwin '; ''emc-p...@majordomo.ieee.org' '
Oggetto:RE: Immunity Testing to EN55024


 Are you sure you are reading that correctly. In the radiated portion in a
note to the side of the levels it says that the test level is prior to
modulation. I believe that is trying to say turn up the levels until 3 v/m
measured and once that is done then begin the modulation and start sweeping
through the test frequencies.
gary

-Original Message-
From: Bronaugh, Edwin
To: 'emc-p...@majordomo.ieee.org'
Sent: 9/6/00 11:31 AM
Subject: RE: Immunity Testing to EN55024


It remains 3 V/m.  However, the peak envelop power is 5.1 dB higher than
the
unmodulated carrier level.  If you set a signal generator to produce an
unmodulated carrier (usually through an amplifier) of 3 V/m and then
modulate it 80 %, the generator will still show the same carrier level,
but
the amplifier will have to produce nearly four times as much power.  If
you
measure the E-Field level with an average (carrier) detector in an EMI
meter, the carrier level will not change from unmodulated to modulated.
If
you use a peak detector, the E-Field level will be 5.1 dB higher.  EdB

-Original Message-
From: Antonio Cinquino [mailto:cinqu...@cae.ca]
Sent: Wednesday, September 06, 2000 10:34 AM
To: 'emc-p...@majordomo.ieee.org'
Subject: Immunity Testing to EN55024



Hello Group,
 
 
Table 1 of EN55024 calls for a test specification of 3 V/m
(umodulated, r.m.s) radio-frequecny EM field for Immunity at the
enclosure
port. 
 
Does anyone know off-hand the value when the signal is 80%
modulated
with an AM signal of 1kHz as called for in the same table?
 

Antonio Cinquino 
CAE Electronics Ltd. 
Electrical System Designer 

Phone : (514) 341-2000 (ext. 4303) 
Fax  : (514) 340-5552 
Email  : cinqu...@cae.ca mailto:cinqu...@cae.ca  

 

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R: Conducted Emissions on Telecom Ports

[Paolo Roncone]

Hi Eric,

I 100% agree with you. The scope of emissions standard should be to protect the 
outside (i.e. public) environment from interference. So only ports that 
connect to public telecom networks should be covered by the standard. The 
problem is (as pointed out in one of the previous notes) that the new CISPR22 / 
EN55022 standard clearly includes LAN ports in the definition of 
telecommunications ports (section 3.6) no matter if they connect to the 
outside world or not. 

Regards,

Paolo Roncone
Compuprint s.p.a.
Italy

-Messaggio originale-
Da: eric.lif...@ni.com [SMTP:eric.lif...@ni.com]
Inviato:mercoledì 6 settembre 2000 17.55
A:  emc-p...@ieee.org
Oggetto:Re: Conducted Emissions on Telecom Ports


All,

As a not-quite-outside-observer (strictly EN 55011 here) of this thread, it's
not fun seeing LAN ports classified as telecom; IMO that's overkill for the
folks using EN 55022.

Up till now, I considered a port to be telecom only if it connects a client
facility to a carrier's network (DSL, ISDN, T1 and so on).

With repeaters every 5 meters, USB and 1394 can support a bus long enough to
connect between adjacent buildings.  So, I wonder if some fanatic will soon be
promoting USB/1394 ports as telecom?

If Chris is right, and the EN 55022 version of the old telecom port conducted
emission standard was intended to protect other telecom signals in a bundle,
then I would think that this test is clearly redundant to the immunity tests
(61000-4-6 and -4-3) that offer the needed protection from the other end.

Does this emission requirement appear to be a waste of time and money to anyone
else?

Regards,
Eric Lifsey
Compliance Manager
National Instruments






Please respond to Chris Allen chris_al...@eur.3com.com

To:   Pryor McGinnis c...@prodigy.net
cc:   david_ster...@ademco.com, emc-p...@ieee.org,
  gary.mcintu...@worldwidepackets.com, John Moore
  john_mo...@eur.3com.com (bcc: Eric Lifsey/AUS/NIC)

Subject:  Re: Conducted Emissions on Telecom Ports


Pryor,

Unfortunately, I don't think the definition is in question. It specifically
states, that for the purposes of the standard, LANs are to be considered as
telecomms ports as per section 3.6. It probably would have been less ambiguous
if the standard defined Telecomms ports as Ports which are intended to be
connected to the telecomms network OR LANs OR similar networks.

As far as enforcement goes this will not change from the current method of
enforcing compliance, primarily via the end user requesting DoCs and the
relevent test data to back this document up.

I believe the requirement goes back to a test that was performed under either
VDE 0805 or 0806 (it was a long time ago that I had to perform the test). It was
specifically aimed at unscreened cables over a certain length being placed in
cable ducts and their impact on adjacent telecomms cables (if anybody remebers
StarLan this was the product I was involved in).

Chris.





Pryor McGinnis c...@prodigy.net on 05/09/2000 20:54:51

Please respond to Pryor McGinnis c...@prodigy.net

Sent by:  Pryor McGinnis c...@prodigy.net


To:   david_ster...@ademco.com, emc-p...@ieee.org,
  gary.mcintu...@worldwidepackets.com
cc:(Chris Allen/GB/3Com)
Subject:  Re: Conducted Emissions on Telecom Ports


I do not disagree with the positions posted on this subject.  My question is
how does the EU interpret and enforce this requirement/definition.

Pryor

- Original Message -
From: david_ster...@ademco.com
To: emc-p...@ieee.org; gary.mcintu...@worldwidepackets.com
Sent: Tuesday, September 05, 2000 2:07 PM
Subject: RE: Conducted Emissions on Telecom Ports



  LAN ports
  Testing Conducted RF Emissions on LAN twisted-pair lines is almost
  contrary to the intent of EN 55022 as Gary pointed out.  Conducted
  emissions is more appropriate for asynchronous analog lines.

  LAN transmissions are digital and synchronous (except maybe ATM); the
  receiver part of the interface circuitry locks onto the frequency of
  data, rejecting spurious frequencies. The signals are truely digital,
  not analog as in a modem.

  Arcnet, Ethernet, and Fast Ethernet TP cabling links two points
(node,
  hub, switch, bridge) which digitally reconstitute the signal,
  eliminating spurious cable frequencies.

  Token-Ring is peer-peer, usually through a passive hub.  Each node
  (peer) reconstitutes the signal as above.

  Ethernet, F-E and Token-Ring ANSI/IEEE or ISO/IEC physical layer
  requirements define interfaces, cable lengths/type(s) and timing.

  Coax cable rules for Arcnet, 10Base2 Ethernet) permit connection to
  multiple nodes but again, the digital nature of the signals and the
  well-defined connectivity rules prevent problems.

  David


  __ Reply Separator
  _
 Subject: RE: Conducted Emissions on Telecom Ports

R: R: R: Voltage Breakdown

[Paolo Roncone]

Hi Rich and all others: 

Thanks a lot for clarifying this issue. I was living with one wrong idea about 
electro-static build-up mechanisms until you guys got me the right explanation. 
This to me is another confirmation of the value of this forum.

Thank you again,

Paolo 

-Messaggio originale-
Da: Rich Nute [SMTP:ri...@sdd.hp.com]
Inviato:mercoledì 12 luglio 2000 18.40
A:  paolo.ronc...@compuprint.it
Oggetto:Re: R: R: Voltage Breakdown




Hi Paolo:


From the other responses to your question, it appears
that there are several phenomena that apply.

Upon reading the other responses, and reading the 
referenced web sites, it appears that, in a humid
atmosphere, build-up of electrostatic charge is 
limited by micro-condensation on material surfaces,
which tend to bleed off charge before it can build
to a value sufficient to break down the electric
strength of the air.

So, there appears to be no conflict between the fact
that humid air has a slightly higher dielectric
strength than dry air, and the fact that humid air
limits the build-up of surface charge compared to
dry air.

(I have not copied the list with this response, but
I did want to reply to you personally since you had
ask a question of me personally.)


Best regards,
Rich




   

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R: R: Voltage Breakdown

[Paolo Roncone]

Hi Rich:

thanks for your reply. Now I regret to say that I am a bit confused. 
Based on what you say I don't understand why in dry weather you have more 
chances of high voltage ESD than in humid weather. As I said this is a common 
experience that anyone can confirm.
I thought the explanation is that dry air has higher dielectric strength so 
higher electrostatic fields need to build up before a discharge.
Another point suggesting the dependence from humidity is that the ESD standard 
EN 61000-4-2 specifies relative humidity among ambient conditions to control 
during ESD tests.

Regards,

Paolo

-Messaggio originale-
Da: Rich Nute [SMTP:ri...@sdd.hp.com]
Inviato:martedì 11 luglio 2000 19.39
A:  paolo.ronc...@compuprint.it
Cc: Product Safety Technical Committee
Oggetto:Re: R: Voltage Breakdown




Hi Paolo:


   what about relative humidity of air ?
   I believe breakdown voltage depends also on humidity content of air.

Contrary to conventional wisdom, the water 
content of air, humidity, actually increases
the dielectric strength of air by a slight 
amount.  (Sorry, but I cannot cite where I
read this.)  As I recall, the increase is so
small as to be negligible compared to all of
the other factors affecting dielectric 
strength of air.

Note that liquid water and gaseous water
(water vapor) have entirely different physical
properties.  It is not unreasonable for water
vapor to have a greater electric strength 
than air.  

For gases, according to the Standard Handbook 
for Electrical Engineers:

The relative dielectric strength, with few
exceptions, tends upward with increasing
molecular weight.

The noble atomic gases (helium, argon, neon,
etc.) are poorest... and have the lowest
dielectric strengths.

If we applied this generality (contrary to my
initial assertion), then the electric strength 
of water vapor, H2O, should be less than that 
of either oxygen, O2, or nitrogen, N2.  However, 
note that the actual number of molecules of 
water vapor in air at any temperature is very 
small compared to the number of molecules of 
oxygen and nitrogen.  So, the reduction of 
dielectric strength by the presence of water 
vapor, if any, will be very small.



Regards,
Rich



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R: Voltage Breakdown

[Paolo Roncone]

Hi,
what about relative humidity of air ?
I believe breakdown voltage depends also on humidity content of air.
One thing anybody can experience is the much higher frequency of ESD jolts one 
gets in dry weather vs. humid weather.  Anyone knows a quantitative relation or 
formula ?

my penny's worth...
Regards

Paolo Roncone

-Messaggio originale-
Da: bogdan matoga [SMTP:bogda...@pacbell.net]
Inviato:sabato 8 luglio 2000 22.57
A:  Rich Nute
Cc: allen_tu...@pairgain.com; emc-p...@ieee.org
Oggetto:Re: Voltage Breakdown


Gentlemen:
Let me add my penny's worth to Rich's information.
a. Parallel plates provide a homogenous field only in their center, the
field fringes at the edges. (One could configure the plates according to
Rogowski form).
b. The breakdown voltage is not a linear function, even for spherical
electrodes. What applies is Paschen's law, which gives the voltage as a
function of distance x atmospheric
pressure.
Have fun!
Regards,
Bogdan.

Rich Nute wrote:

 Hi Allen:

 The voltage breakdown of air is presented in
 IEC 664.

 There is no fixed number (i.e., mm/kV) that
 describes or predicts voltage breakdown of air.

 The principle factor that affects voltage
 breakdown is the shape of the electrodes
 (degree of homogeneousness of the electric
 field between the two electrodes).  The more
 homogeneous the field, the higher the breakdown
 voltage, and vice versa.

 For example, at 2 mm, the breakdown of an
 inhomogeneous field is about 2.5 kV, while the
 breakdown of an homogeneous field is almost 8
 kv!

 An homogeneous field is created by two parallel
 planes.  An inhomogeneous field is created by
 a needle-point and a plane.

 The second factor that affects voltage
 breakdown of air is the voltage waveshape.  The
 more impulse-type waveshape, the higher the
 breakdown voltage; the more sinusoidal-type
 waveshape, the lower the breakdown voltage.

 The third factor that affects voltage breakdown
 of air is the air pressure.  The higher the air
 pressure, the higher the breakdown voltage, and
 vice-versa (Paschen's Law).

 There are still other factors such as temperature,
 but these are minor effects compared to the first
 three.

 If you are interested, I can send a Powerpoint
 4.0 file of the voltage-distance curves of the
 homogeneousness effect.  It covers the distance
 range from 0 to 2 mm for both homogeneous and
 inhomogeneous fields for sinsoidal waveforms.
 The data is taken from IEC 664.

 Best regards,
 Rich

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Re: EFT/Burst

[Paolo Roncone]

Thank you for your replies to my first inquiry.
In particular, George's observation that sec. 7.3.1 applies only to 
post-installation tests made me realize that I missed the right point in the 
standard, that is sec.7.2.2. I just don't understand why the guys who wrote the 
document were not specific in the more important (and used) case of tests 
performed in labs (those are mostly the ones used to verify compliance). So 
they leave the door open to any possible combination of phase/neutral/ground 
when applying the bursts to the AC line.
One important point that I didn't mention in my previous note was that the 
failure is not specifically  related to the printer, but to a LAN/Ethernet box 
that is attached. Our OEM got 2 different printers to fail under the same 
conditions (bursts with positive polarity @ 1kV applied to Line and Protective 
Earth (PE) simultaneously) with the very same box attached. The printer stops 
printing and go to a Ready state. You are able to make the printer Not Ready 
and back to Ready, but it does not continue to print. the PC driving the 
printer says the data timed out sending to the device.
The same printers don't fail when tested without this LAN box.
Our feeling is they want to pull us into working on the problem because the 
vendor of the LAN box is not so willing or able to help.

Of course any additional hints can be very helpful.
 

Paolo Roncone



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Re: origin of common-mode currents

[Paolo . Roncone]

Muriel,

One more opinion on the subject. I was going to reply to you yesterday but I
then I didn't get the time to do it..
I agree with Jim Knighten. The first thing that came to my mind was the paper
that he mentioned in his second reply:

Investigation of fundamental EMI source mechanisms driving common-mode
radiation from printed circuit boards with attached cables  by:
D.M.Hockanson,  J.L.Drewniak,  T.H.Hubing,  T.P.Van  Doren,  Fei  Sha  and M. J.
Wilhelm - IEEE Transactions on EMC, Vol.38, no.4, November 1996.

I think this is a very good and solid reference covering the subject (addressed
to common-mode radiation).
It also contains other useful references on the subject of common mode
disturbances.

The  physical  phenomena of the common-mode emissions are essentially related to
the  finite  (non-zero)  impedance  of  each  and every conductor. Every circuit
carrying  time-varying  (differential  mode)  voltages/currents generates common
mode voltages/currents.
This is deep-rooted in physics and specifically in Maxwell's equations.
Faraday's  law  is  one  of  them:  it  says that every time you have a variable
current - variable magnetic field, you have a voltage drop - that voltage drop
drives the cm current.
Typical  case:  the  voltage  drop  across the inductance of return paths in any
circuit  drives a common mode current that flows across a stray capacitance (you
never have open circuits in rf !).
The  higher the frequencies in your signals (differential mode voltage/current),
the  higher  the  effects  of stray inductances and capacitances in any circuit.
These  are  inevitable  phenomena.  One  key  factor in EMC is to minimize these
parasitic inductances and capacitances.
As for your example, a DC battery feeding a resistor doesn't have cm currents in
stationary conditions (constant voltage/current). But when you open or close the
circuit you have transients that generate cm currents.
Whether they are negligible or not, that depends on the stray impedances in your
circuit  and  on the wave-shape of the transients (the faster they are, the more
likely you will see cm currents).
For all the details go to the above mentioned paper

Just my 0.2 cents..



Regards,

Paolo Roncone
Compuprint s.p.a. - Italy





Muriel Bittencourt de Liz mur...@grucad.ufsc.br on 04/05/2000 17.12.42

Please respond to Muriel Bittencourt de Liz mur...@grucad.ufsc.br
  
  
  
 To:  EMC-PSTC List emc-p...@ieee.org   
  
 cc:  (bcc: Paolo Roncone/IT/BULL)
  
  
  
 Subject: Re: origin of common-mode currents  
  








Group,

Thanks for all the answers to the question of common-mode emissions.

But, as I did once, most of you didn't understand what I meant.

I've already read books of EMC (like C.R. Paul), saw a lot of
homepages/magazines (RBItem, chapters of IEEE EMC society), read books
of electronics-area... etc... But all this references did not mention
anything about the physical phenomena of the common-mode emissions. I
don't know if I'm not being clear... So, please question me about more
details...

For example, in a simple circuit (a DC battery feeding a resistor), do I
have common-mode emissions? Are the common-mode emissions inherent from
any physical system? Can I model them in HF?

Thanks in advance.

Muriel

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Re: Is the modular approach to EMC the same as CE + CE = CE?

[Paolo . Roncone]

Here is my understanding of the approach to systems compliance for CE marking.
If all parts of the system are CE marked you are not (legally) required to
re-test the system for compliance to the EMC Directive, provided you give clear
instructions for assembly/installation/operation/maintenance in the instructions
for use (installation guidelines). The Declaration of Conformity , as well as
the instructions for use, must refer to the system as a whole. My understanding
of the modular approach is that if all parts are CE-marked you are not
required to put the CE mark on the system as a whole. This is the legal aspect.
On the other end, I fully agree that CE + CE  = CE is far from sure until you
have tested the whole system for compliance ! There is a clear statement on this
in the Guide to the Application of Directive 89/336/EEC published by the
European Commission (1997). In sec. 6.4.2.1 (System assembled from only CE
marked apparatus)  there is a paragraph titled Additional comment:
... combining two or more CE-marked subassemblies may not automatically produce
a system which meets the requirements of the relevant standard.
I fully agree with this statement, since the
wirings/packaging/grounding/shielding aspects of any assembly process can
determine the EMC behavior of the complete system.
So my conclusion is: the safest way is to test the system as a whole, because in
any case (whether you choose to follow the modular approach or not) the
Declaration of Conformity refers to the whole system and manufacturer is
responsible for compliance.

Hope this helps.

Best Regards,

Paolo Roncone
Compuprint - Italy






Canio Dichirico cdich...@eso.org on 27/03/2000 14.30.50

Please respond to Canio Dichirico cdich...@eso.org
  
  
  
 To:  IEEE EMC List emc-p...@ieee.org 
  
 cc:  (bcc: Paolo Roncone/IT/BULL)
  
  
  
 Subject: Is the modular approach to EMC the same as CE +   
  CE = CE?
  








Hi All!

The designer/manufacturer of a (prototype) system has recently exposed to me the
following argument. If the system is built out of subsystems that are CE-marked,
the complete system may be considered compliant with the EMC Directive
89/336/EEC. The designer stated that this is possible on the basis of the
modular approach to EMC.

In order to understand this argument I read the paper Update on the European
Union's EMC Directive, appeared on the European Edition of Compliance
Engineering - 1999 Annual Reference Guide. In this paper one may read that For
systems and installations ... either a system or a modular approach may be used
to demonstrate compliance. The TCF [Technical Construction File] route is thus
not required for verifying a system and/or installation if all subunits and
subsystems comply with the EMC requirements (modular approach), presuming that
the referenced standards are relevant for intended environments and that
installation guidelines are followed.

Does what I read on Compliance Engineering confirm what declared by the
(prototype) system designer?

Which are the installation guidelines that the paper quoted above is referring
to? Which are the differences, if any, between the modular approach and the
equation CE + CE = CE? I remember reading in this forum (plenty of times) that
CE + CE does not necessarily equal CE.

Any replies or comments are welcome.

Thank you all in advance!


Canio Dichirico
European Southern Observatory
Technical Division - Electronic Systems Department
Karl-Schwarzschild-Str. 2
D-85748 Garching bei München

Tel. +49-89-3200 6500
Fax +49-89-320 23 62
email: cdich...@eso.org
website: www.eso.org



Hi All!

The designer/manufacturer of a 
(prototype)system has recently exposed to me the following argument. If 
the system is built out ofsubsystems that are CE-marked, the complete 
system may be considered compliant with the EMC Directive 89/336/EEC. The 
designer stated that this is possible on the basis of the "modular approach to 
EMC".

In ordertounderstand this argument I 
read thepaper "Update on the European Union's EMC Directive", appeared on 
the European Edition of Compliance Engineering- 1999 Annual Reference 
Guide. In this paper onemayread that "For systems and installations 
... either a system or a modular approachmay be used to demonstrate 
compliance. The TCF [Technical Construction File] route is thus not required for 
verifying a s

Re: modest proposal

[Paolo . Roncone]

Hi all,
that's the world we live in. Like it or not, English is the de-facto
international language, especially in the technical/scientific community.
I personally enjoy participating in this forum mostly for its invaluable
technical contents but I also find it a very useful tool for improving my
knowledge of the english language (mostly american English I should say).
As a non-english participant, I personally prefer colloquial or informal English
than the bureaucratic English used in the regulatory documents (CENELEC, IEC,
FCC etc.). The spirit of this forum is to be an informal gathering of
professionals open to discuss any EMC/Sfafety issue like they would do if they
met personally.
The only recommendation I would make - especially to the majority of US
participants - is not to let too much slang into their language, if they
honestly want to  reach out to all international participants. It's not  a
question of oversimplifying the english language, just take care of using a
little bit more of plain standard English than you would normally do when
talking to your next-door buddies !   I think that would not impoverish the
language and would just be more understandable to a wider international
audience. As Lou pointed out, not everyone out there has the same proficiency in
the english language so it's just a question of keeping it a little more
standard if you want to maximize the EMC/Safety knowledge and experience that
you can tap from this planet .
Having said that, I personally enjoy extending my vocabulary and learning
american slang, but that's another, more personal, point.


Thanks to all

Paolo Roncone
Compuprint - Italy

P.S. BTW (= By The Way) Scott, what's the meaning of   Please include gotcha's
to watch out for.. ?
(taken from you post with subj: PCI Cards  EMC Testing)



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RE: Dithered clocks and EMC - BEWARE

[Paolo . Roncone]

I have a very succesfull experience with SSCG (Spread Spectrum Clock Generation)
that  is  a  patented  technology  used  to  intentionally  spread the energy of
oscillators  and  clock signals and any signal derived from the clock. I am sure
Keith Hardin knows it first-hand because he is one of the developers !
We  have  been  using  an SSCG chip since 1995 on most of the electronics of our
printers  -  most  of  them  class B devices, with oscillator frequencies in the
range  24  -  32  MHz.   We   even managed to get significant cost reductions by
switching from 4-layer to 2-layer boards and still passing CISPR22 and FCC class
B limits for radiated emissions.

One  point  that  seems  not  to  have come up in this discussion is the kind of
dithering we are talking about.
In SSCG the main clock frequency is modulated, but just ANY frequency modulation
is  not  enough  ! Key is the wave-shape of the modulating function, and that is
the  crucial  point  in  the  SSCG  patent (Keith, correct me if I'm wrong). The
trick  is  to  maximize  the  rate  of change of the function representing the
frequency  modulation,  so  that  the  oscillator spends the minimum time on any
given  frequency  within the modulating range, thus avoiding additional peaks in
the  emission  spectrum. The modulating function in the SSCG technique does just
that.
This is best explained in the first (to my knowledge) publication on the subject
(here, too, Keith knows much more !!) :

K.B.Hardin,  J.T.Fessler,  D.R.Bush  (Lexmark  Intl.):  Spread  Spectrum  Clock
Generation  for  the  Reduction  of  Radiated  Emissions   -   1994  IEEE Intl.
Symposium on EMC, August 1994 Chicago (Symposium Record page 227)

I  suspect  an explanation to Scott's problem may be that he didn't use the SSCG
technique  but  another form of  dithering that was not controlled in such a way
as  to  get  the  flat  frequency distribution that you get with SSCG.  Also the
amount  of  frequency  deviation  can  be  important. The attenuation you get in
quasi-peak  (QP)  readings  is  dependent on that. I hope Scott can give us more
details.

As  to  the  problems with digital TV, I honestly don't have any knowledge about
that,  but  I  remember  the  same inventors of SSCG did a study on interference
potential of this technique :

K.B.Hardin,   J.T.Fessler,   D.R.Bush   (Lexmark  Intl.): A  Study  of  the
Interference  Potential  of  Spread Spectrum Clock Generation Techniques - 1995
IEEE Intl. Symposium on EMC Atlanta ( Symposium Record page 624).

Hope this helps.

Paolo Roncone
Compuprint s.p.a. - Italy



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Re: Antenna factors to be used for NSA measurement

[paolo . roncone]

Barry,
thanks a lot for the information. I'll check the article as soon as possible.

Back to my latest post on the subject, I realized I missed an important detail 
in the last point (4). Quoting myself:

for NSA measurements and site validation you can
limit the job to horizontal polarization (as required by the standards).
The antenna calibration in vertical polarization is useful to improve accuracy
of emissions measurements of products (using vertical and horizontal AFs).

I forgot that both Horizontal and Vertical (not just Horizontal)NSA are 
required 
by the standards to validate the test site. 
So my conclusion is (based on the work by Z.Chen and M.Foegelle): the best 
choice 
would be to perform both Horizontal AND Vertical NSA measurement on the 
standard 
site (3 antenna method)and use both Horizontal and Vertical AFs of the antennas
used for validation of your test site (measured NSA to be within +/- 4 dB of 
ThNSA). 
Also the same Horizontal and Vertical AFs can be used during emissions 
measurements 
of products to maximize accuracy.
I agree with Robert that variations of AFs with antenna height can be 
important. 
On the other end I just wonder how to include this AF variations into 
measurements 
without unacceptable impact on test time. You should use different AFs for 
different 
antenna heights and for each polarization ! 


Paolo Roncone

RCIC - http://www.rcic.com
Regulatory Compliance Information Center




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Re: Antenna factors to be used for NSA measurement

[Paolo . Roncone]

Robert,
there are a couple of points that came up in your posts that I would like to
more fully understand.

1. ...the site under test is verified against the performance of the site on
which the antenna factors are calibrated.
I honestly don't get this point. The applicable standards (ANSI C63.4 and
CISPR22) require that you verify the measured Normalized Site Attenuation (NSA)
against a Theoretical Normalized Site Attenuation (ThNSA) of an ideal site
(infinite perfectly conductive ground plane), NOT against the site on which the
antenna factors are calibrated. Ref. sec.ANSI C63.4-1992 sec.5.4.6.1, CISPR 22 -
1997 (3.ed) sec.10.3.2. This is what the standard says, although its validity
has been questioned by a number of EMC experts.

2. ...a dual antenna factor calibration suffices if the same antennas will be
used in the NSA measurement, there is no accuracy advantage when using a
three-antenna method in this case.
In ANSI C63.5-1988 I read (sec.5.2 page12): In practice, two antennas are never
identical, and the antenna factor calculated by Eq.8 is the geometric mean of
the individual factor for each of the two antennas..
That's the reason why I said that the 3 antenna method is more accurate.
Also,your statement: Antenna factors provided by the manufacturer or measured
by a cal lab are typically not of sufficient accuracy (with a few exceptions)
reinforces my opinion.

3. There are substantial difference in the antenna factors (and site
attenuation) values at various range distances.
I agree that it's always better to calibrate antennas at the test distance. On
the other end, within the range of 3-10 m distance my experience with broadband
antennas (biconicals and log-periodic) between 30 and 1000 MHz tells me that the
error is well within 1 dB, as long as you are in the far-field at 3 m (which is
the case most of the times using biconicals). I have not direct experience but
my guess is that you may have non-negligible errors for distances  3m and/or
highly directional antennas (horns  freq. 1GHz), whereby you can be  in the
near field even at 3+ meters distance.

4. I know the article you mentioned (Z. Chen and M.Foegelle: Numerical
Investigations of Ground Plane Effects on Biconical Antenna Factor) exposes one
weakness of the ideal (theoretical) model used for calculating ThNSA (see point
1). The analytically derived model assumes that the antennas used are point
dipoles that behave in a different way than the most used broadband antennas.
They use a numerical analysis to measure the effects of the ground plane on AFs
of biconical antennas (field variations and antenna coupling with the ground
plane). Their conclusions are, in their words, that if an ANSI C63.5 standard
site calibrated AF is used for ANSI C63.4 (NSA measurements), all the
approximations and ground plane effects exactly cancel.
My understanding is that if you use the same geometry for the calibration of
antennas (3 antenna method) over a ground plane and for the validation of your
site (OATS or SAR), the variations of antenna factors associated with the
coupling antenna-ground plane are compensated and do not add errors to the NSA
measurements. Provided the two ground planes (calibration site and test site to
be qualified) have ground planes that behave in the same way !
So under these conditions, for NSA measurements and site validation you can
limit the job to horizontal polarization (as required by the standards).
The antenna calibration in vertical polarization is useful to improve accuracy
of emissions measurements of products (using vertical and horizontal AFs) other
than in cases - as mentioned by Don Umbdenstock - where the error introduced by
AF variation does not get you over your total budgeted measurement uncertainty.

Any further comment would be highly appreciated.

Regards,

Paolo Roncone



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Re: Antenna factors to be used for NSA measurement

[Paolo . Roncone]

Hi Pierre,

did anyone reply to your post ? I would be a bit surprised in that case, given
the high and broad level of EMC experience among us.
I am pretty much interested in how your NSA and antenna calibration measurements
are going and what results are you getting. This subject is widely covered and
discussed in the EMC literature and my understanding is that there are quite a
number of different opinions on how to combine or match NSA with the most
appropriate antenna factors.
I presently work in a 3m/10m OATS, but I also have worked in 3/10m SARs.
First one question: did you actually perform the four different NSA measurements
that you describe in your email ?
You say :

Depending the method used, the NSA is OK or NOT.

So I guess you did try all of them. If this is the case, which one(s) got the
good NSA and which  one(s) didn't ??

By good NSA (the one that is OK in your words) I mean one that is within +/-
4dB all over the 30-1000 MHz range as specified by ANSI C63.4 and CISPR22.
Now I give you my personal opinion, based both on my direct experience and on
other people's experience, taken from the EMC literature.

I personally used either choice 1 or 2.
CHOICE 1: the manufacturer's antenna factors IF they are individually calibrated
for the serial numbers of the antennas that you purchased and IF they are
determined following one of ANSI C63.5 methods. This can work for about 1 year
after purchase of the antennas. You should recalibrate your antennas after one
year of frequent use.
CHOICE 2: antenna factors determined with the 3 Antenna Method or Standard Site
Method. The site to be used for antenna calibration should be an OATS different
from the site that you want to qualify and later used for your emissions tests,
be it an OATS or SAR. The reason is that the site imperfections of the Standard
Site (the site that you use for antenna calibration) are embedded in the
calculated AFs of the antennas and would cancel out when
you calculate the NSA of your site (the 3m SAR).

A good reference can be the following article from the 1995 IEEE EMC Symposium
Record (page 327):

W.M.Elliott, J.M.Roman, R.Robles: Three-Site Study of Variations Introduced by
Standard Site Imperfections Using the ANSI 63.5 - 1988 Standard Site Method for
Antenna Calibration.

If you don't know how to get it, I may fax you a copy. Just let me know.
I pick up this formula from the reference and refer it to your case :

NSA = ThNSA + da - db

where

NSA = VD - VS - AF1 - AF2

ThNSA = theoretical NSA (ref. ANSI C63.4 and CISPR22)
da = SAR deviation from ThNSA
db = Standard Site deviation from ThNSA
AF1, AF2 = antenna factors of transmitting / receiving antennas

If you use the 3 antenna method in your SAR, da = db and the site error would
cancel out giving you an apparent perfect result (NSA = ThNSA) for your SAR,
even if the site is not perfect.

I would not recommend choice 3 (two antenna method) in favor of choice 2 (three
antenna method) that basically follows the same path but is more accurate.
As for choice 4, it's not clear to me if you performed the measurements in the
SAR or in a OATS. The first case would be wrong because of the above shown
formulas (you would not see your SAR's imperfections). In any case it looks to
me similar to choice 3 and so less accurate than the 3 antenna method.
If you perform both Vertical and Horizontal measurements, that would improve
your accuracy, giving you separate Vertical and Horizontal AFs. But, again, I
would stick with the classical three-antenna method just adding the Vertical
polarization.
The ThNSA is used in the reference standards (ANSI and CISPR) to calibrate your
site (SAR or OATS) against the reference theoretical site (infinite ground
plane).

One final point: the ANSI standard C63.5 latest edition is 1998. I heard that
free space antenna factors are considered for SARs (I still don't have a copy of
it).
My opinion is that it's better to calibrate your antennas over a reflecting
ground plane (OATS) if you are going to use the antennas over a ground plane
(OATS or SAR), because the ground plane affects antenna factors.
The good side of free space antenna factors is that they average out the AF
variations with antenna height (1-4 m scan of receiving antenna), but - on the
other end - you lose the non-negligible ground plane coupling effects. So I
think it's better to use free space AFs in a Fully Anechoic Room (FAR), rather
than in SARs or OATS.
My opinion is that - given the many variables involved - we should strive for
the most reasonable compromise between measurement accuracy and ease of
reproducibility of measurement procedures among all test laboratories, and that
(as we all know) is far from easy !

Hope this helps. Let me know !!

Paolo Roncone
Compuprint s.p.a. - Italy








Pierre SELVA (NCE) pierre.se...@wanadoo.fr on 09/03/2000 10.00.27

Please respond to Pierre SELVA (NCE) pierre.se...@wanadoo.fr

Re: EMC and product safety split?

[Paolo . Roncone]

Hi Michael,

I am also interested in EMC design issues, as an EMC Engineer following my
company's products (printers) from crib to grave.
Can you address me to the EMC design or SI forum that, I understand, you are in
?
Thanks a lot in advance.

P.S. One comment over the EMC-safety split: I agree with many in this forum that
it's good as it is now, even if I work on EMC only. That's because (1) it's
always good to get a wider perspective, plus (2) the two topics - as already
mentioned - can overlap and (3) because of the last point in some cases I may be
interested in keeping some posts with a safety subject.


Paolo Roncone
Compuprint s.p.a.
Italy






Michael Vrbanac vrban...@swbell.net on 12/03/2000 05.50.08

Please respond to Michael Vrbanac vrban...@swbell.net
  
  
  
 To:  Robert Legg rl...@tectrol.com, IEEE EMC-PSTC  
  Forum emc-p...@majordomo.ieee.org 
  
 cc:  (bcc: Paolo Roncone/IT/BULL)
  
  
  
 Subject: Re: EMC and product safety split?   
  









All,

After reading several responses on this, I'll throw my two cents in

Since my main interests are in high performance physical system design and
integration,  EMC and signal integrity design (among others) are foremost
in my
interests, so design issues are of primary importance to me and regulatory
details of secondary importance.  So the following opinion is offered under

these considerations.

I have valued the forum as it is and how it has progressed in the several
years
I have been on it.  The regulatory content has been excellent.  I have, in
the
recent past however, noted the lower incidence of posts dealing with
specific
design issues. This is not a bad thing but being also a member of the
SI-Forum, I have noticed most of the technical EMC design posts migrating

over there in the last year or two.  While it is granted that some EMC
design
issues can resolved by attention to signal integrity, it is wondered why it
is felt
that they must post EMC questions on a signaling forum.  Is it because
this
forum is now dealing with primarily regulatory details rather than design
details
or migrating that way?

I really don't have an answer for that but it bears some thought and may be
the
underlying basis for the question that Robert has posed to us.  In an
attempt to
answer to his question, I wonder if it lies in what we want the forum to
address
and what we decide to emphasize.  If we can't address it all here, perhaps
another forum is in order.  The only downside for me to that is that I
don't need
another forum to inundate me with email.  This one and the other I
mentioned
is quite enough as it is.

So that's my thought for the day enjoy!

Michael E. Vrbanac



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