Rao, The comb generator is not a bad choice, but a few things should be checked (yes, I've done this).
First, establish the base variation in the source. No antenna, just a direct connection to the receiver/SA that you will use for the evaluation under an expected, reasonable variation in temperature and battery condition. Take enough samples over enough days to make yourself statistically comfortable with the level of uncertainty you're targeting. Second, use the volumetric calibration procedure (as required for "alternative" test facilities) on both the SAC _and_ the OATS. Having done volumetric NSAs on high quality SACs and low quality OATS, I can say there is _no_ reason the OATS can be considered a "gold standard" in all instances. Lowell Kolb of Hewlett-Packard did an excellent paper on comparison of OATS sites a few years back. I would suggest looking up his paper for an idea of OATS site to site variation. Lastly, everything I've just said will, most likely, be totally swamped by variations in the EUT setup under "real" EUT testing unless you can _strictly_ control them. Don't go there. The more "real" the simulated EUT becomes, the more variables you introduce into the site evaluation. As more variables are introduced, the greater the number of data points will be required to resolve the result. While it is obvious to the most casual observer that the simple comb generator does not represent a "real" EUT, it does represent a single frequency component at a single phase component for each of the volumetric measurement points. The best work done in this area has used a VNA for evaluation of both quantities, but from the literature, this would appear to be most useful in diagnostic applications. Empirically, if the magnitude of the seven single planar volumetric points looks good, the site is _probably_ pretty good. Of course, if the SA is systematically off at all points, check the antenna calibration! Best regards, Brent DeWitt -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Rao, Praveen Sent: Sunday, January 06, 2002 6:16 PM To: [email protected] Subject: Comparing EMI test results I'm trying to setup a programme to compare test results (for Radiated Emissions) between test labs. The plan is to circulate a "Artifact" around the labs and compare the results. The test sites being compared are Semi-anechoic Chambers v/s OATS. The source used is a wideband "RF comb generator". I would like to understand the concept fully before I initiate this programme. Is there any information readily available on this topic? Any help will be greatly appreciated. Thanks. Praveen ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
