---------------------- Forwarded by Brent F Pahl/FOS/PEC on 03/28/2000 03:59 PM
---------------------------
Brent F Pahl
03/23/2000 01:43 PM
To: "Lacey,Scott" <[email protected]>
cc:
Subject: RE: Ambient Cancellation Device for OATS (Document link: Brent F
Pahl)
I recently attended one of the CASSPER demonstrations, and when asked the
question of how their instrument deals with EUT noise buried under ambient
noise, they gave this response: The CASSPER system not only compares the
frequency of the incoming ambient (ambients being brought in through the
"distant" antenna), but it also compares the phase and waveform of the signal.
If the phase and waveform between the two antennae signals does not match, then
the signal is not canceled out. They specifically claim that they can find EUT
noise buried under ambient noise. Honestly, I'm still a little skeptical.
Hopefully I'll be able to test this and see how true it is some time soon.
Cheers,
Brent
"Lacey,Scott" <[email protected]> on 03/23/2000 09:34:35 AM
Please respond to "Lacey,Scott" <[email protected]>
To: "'Brumbaugh, David'" <[email protected]>
cc: "'[email protected]'" <[email protected]> (bcc: Brent F Pahl/FOS/PEC)
Subject: RE: Ambient Cancellation Device for OATS
Exactly.
Scott Lacey
-----Original Message-----
From: Brumbaugh, David [SMTP:[email protected]]
Sent: Thursday, March 23, 2000 11:19 AM
To: [email protected]
Subject: RE: Ambient Cancellation Device for OATS
I would like to add that one must be careful when it comes to using
such a system. I apologize if this has been pointed out already, but it
can't be emphasized enough. When using a system like this, you take the risk
that the ambient environment will mask significant emissions from the EUT.
You may never see these emissions under such conditions, and it will bite
you later.
I am particularly concerned when I hear this being touted as a
panacea for testing in traditionally noisy environments, such as development
labs. Be careful folks.
My 2 cents.
DB
> ----------
> From: Price, Ed[SMTP:[email protected]]
> Reply To: Price, Ed
> Sent: Thursday, March 23, 2000 9:01 AM
> To: 'Doug'; [email protected]
> Subject: RE: Ambient Cancellation Device for OATS
>
>
> Doug:
>
> As I understand the process, there isn't actually cancellation AT
the OATS.
> They have a monitor antenna nearby, but relatively far from the
EUT on the
> OATS. A real EUT signal should fall off considerably by the time
it reaches
> the monitor antenna, but an ambient emission will be relatively
constant at
> the monitor and measurement antennas. All you have to do is sample
the
> ambient, invert it, and sum it with the measurement antenna
voltage. This
> should delete the ambient from the measurement data. (Easy to say!
All you
> need is enough computing power and sufficiently capable processing
> algorithms.)
>
> The "cancellation" takes place as a data operation within the
Cassper
> hardware (or it's controlling computer), and not as an energy
cancellation
> of the propagating fields actually on the OATS site.
>
> And yes, I would also like to know more about how Cassper manages
to do
> this. But, I also realize they can't give away their trade secrets
either.
>
> Ed
>
>
>
:-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-)
> 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
>
:-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-)
>
> > -----Original Message-----
> > From: Doug [SMTP:[email protected]]
> > Sent: Wednesday, March 22, 2000 11:38 PM
> > To: [email protected]
> > Subject: Re: Ambient Cancellation Device for OATS
> >
> >
> > Perhaps it's because I've never understood ...
> >
> > How exactly does one do ambient cancellation at an OATS?
> >
>
>
>
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