Just to add to the point David is making: it seems that in bands where intermittant ambient signals are present, it would be nearly impossible to have an automated system such as this. If your OATS is in a location away from such ambient, it seems that it wouldn't be worth the cost or effort. And how does this system weed through broadband ambient or the new HDTV signals? It sounds great on paper, but any engineer who has spent a lot of time on an OATS should be extremely skeptical of its abilities and limitations.
Jeremy Pickens Senior Project Engineer Intertek Testing Services -----Original Message----- From: Brumbaugh, David [mailto:[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? > > > > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
