There are two ways external RF signals enter a product : via the power
mains source or via the antenna, front end, or connecting cable i,e any
input /ouput connecting cable.
It would be possible to generalize and state that a simple common mode
filter on the power /mains input will provide the necessary isolation and
in some cases better rf port design is necessary. For the specific cases you
have cited , I can tell you what my experince can be but remember that the
length of the connecting cable(s) play a large role in how much undesired
signal is carried to the device and this is frequency sensitive. The only
sure way to provide isolation is right at the device so that the length of
attachning /controlling cabling is isolated..
Victim Equipment FI threshold
Proper Control
IR motion sensors varies by model .some are <100 mV/m narrower
sector/ cm chokes at device
Car alarms rare but has been < 1.0 V/m
microprocessor activated, required filtering on control leads
Garage door openers due to frequency conflicts with other services uV.m
powersupply induced typically 2-3 V/m lenghten coding sequence,
filter mains
supply
Baby monitors uV/m
better rf selectivity required
Telephones 1-2V/m caused
by audio rectification rf bypass on transmitter, cm chokes in
line
Computer speakers <100 microvolts (typical)
Computer modems 100-500uV conducted rf
on power adaptor wrap DC cable to device through toroid core
Note: While the above devices will respond to radiated emissions they are
also affected by conducted currents induced in the connecting mains source.
Due to the random nature of connecting power/control/ antenna
cables any of the above devices may appear more radiosensitive and respond
in unintended ways. . I call the connecting wiring " unintentional "
antennas. RI and CI limits for Europe appear to be quite practical and
reasonable in today's ever increasing wireless market and I have yet to have
to suppress devices so marked.
Ralph cameron
EMC Consulting and Suppression of Consumer Electronics Equipment
(After Sale)
----- Original Message -----
From: "Ken Javor" <[email protected]>
To: "Ralph Cameron" <[email protected]>; "Price, Ed" <[email protected]>;
"EMC-PCST (E-mail)" <[email protected]>
Sent: Tuesday, January 16, 2001 11:46 PM
Subject: Re: Consumer Electronics Compatibility
>
> I would surmise the following, and would appreciate if Mr. Cameron could
> confirm / correct as appropriate:
>
> Victim equipment FI threshold proper control
>
> IR motion sensors > 100 mV/m RI
>
> car alarms > 100 mV/m RI
>
> garage door openers uV/m RE/better rf port design
>
> baby monitors uV/m RE/better rf port design
>
> telephones (cordless?) uV/m RE/better rf port design
>
> computer speakers > 100 mV/m RI
>
> The point being that RE are only controlled to protect intentional radio
> reception, and RI is imposed to protect equipment from intentional radio
> transmissions. A grey area would be a garage door opener succumbing to a
> high level signal out of band to its design frequency, which would be
> addressed by limits placed on out-of-band sensitivity, like the old
> MIL-STD-461 CS03/04/05/08.
>
> Ken Javor
>
> ----------
> >From: "Ralph Cameron" <[email protected]>
> >To: "Price, Ed" <[email protected]>, "EMC-PCST \(E-mail\)"
> <[email protected]>
> >Subject: Re: Consumer Electronics Compatibility
> >Date: Tue, Jan 16, 2001, 3:54 PM
> >
>
> >
> > Ed and all who responded:
> >
> > I'm sorry to belabor this issue but I think it is generally one of
awareness
> > and perhaps may not have been raised before in such a manner. I think
all of
> > your observations are correct as Ed surmised < Consumer electronics has
not
> > been well addressed because it has been largely a voluntary requirement.
My
> > opinion is such requirements are not observed in the real world.
> >
> > I am attached a PDF file called EMCAB-1 which in this country was
> > promolgated many years ago and I think that will provide the information
you
> > ae missing. I might say that EMCAB-1 was ignored by manufacturers but
the
> > problems have persisted.
> >
> > I can also say that 15 years ago there were 30,000 cases a year in Cnada
> > alone. This has dropped considerably in the last ten years but now we
find
> > consumer switch mode power supplies casuing the same problem . These are
> > type, typically free running that do not contain microprocessors so do
not
> > fall under the Digital emissions regulations ( FCC Part 15).
> >
> > The harmonics from "electronic" transformers is condcuted back into the
> > powerline and from there is re radiated by house wiring . It is not a CE
> > problem relating to cables.
> >
> > My experience has been that the majority of this 'nuisance " can be
removed
> > effectively with common mode inductors which could be offered as some
> > consumer relief. In Canada, this is the consumer's responsibility.
> >
> > p.s recent devices exhibiting radiosensitivity are : Infra red motion
> > sensors, car alarms, garage door openers, baby monitors, telephones ,
> > computer speakers etc.
> >
> > Ralph Cameron
> > ----- Original Message -----
> > From: "Price, Ed" <[email protected]>
> > To: "EMC-PCST (E-mail)" <[email protected]>
> > Sent: Tuesday, January 16, 2001 10:02 AM
> > Subject: Consumer Electronics Compatibility
> >
> >
> >>
> >> Ralph:
> >>
> >> Would you provide a little more detail about the <30MHz Consumer
> > Electronics
> >> compatibility problems that you have been addressing? Are you finding
that
> >> the path is a direct galvanic connection, or is the problem caused
> > primarily
> >> by radiation of energy off of the power lines? What are the most common
> >> emitting devices, and what types of devices are the most numerous
victims?
> >> And of course, what's usually the best solution?
> >>
> >> Thanks,
> >>
> >> Ed
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: Ralph Cameron [mailto:[email protected]]
> >> Sent: Monday, January 15, 2001 7:57 PM
> >> To: Ken Javor; dan kwok
> >> Cc: EMC-PCST (E-mail)
> >> Subject: Re: Site Correlation
> >>
> >>
> >>
> >> No, your message is clear, what I am saying is that the emissions below
> >> 30Mhz cause the majority of the interference problems to consumer
> >> electronics and that's not being addressed.
> >>
> >> Ralph Cameron
> >>
> >> ----- Original Message -----
> >> From: "Ken Javor" <[email protected]>
> >> To: "Ralph Cameron" <[email protected]>; "dan kwok" <[email protected]>
> >> Cc: "EMC-PCST (E-mail)" <[email protected]>
> >> Sent: Monday, January 15, 2001 10:34 PM
> >> Subject: Re: Site Correlation
> >>
> >>
> >> > I must have been unclear in my previous message. The purpose of
> >> controlling
> >> > cable cm CE is to control the resultant cable-induced RE, which are
> >> > controlled to protect tunable antenna-connected radio receivers,
period.
> >> > There was never any other purpose for controlling CE or RE.
> >> >
> >> > Ken Javor
> >>
> >> Ed Price
> >> [email protected]
> >> Electromagnetic Compatibility Lab
> >> Cubic Defense Systems
> >> San Diego, CA. USA
> >> 858-505-2780 (Voice)
> >> 858-505-1583 (Fax)
> >> Military & Avionics EMC Services Is Our Specialty
> >> Shake-Bake-Shock - Metrology - Reliability Analysis
> >>
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> >>
> >>
> >
> >
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