From: Ridler, Samantha [mailto:[email protected]] Sent: Monday, August 23, 2004 12:22 AM To: '[email protected]' Subject: Average Detection
Hello All FCC part 18 requires the use of an Average detector. For measurements above 1GHz on a HP8593E EMC (Spectrum) analyser, would using a Video Average of 100 or more be equivalent to taking a measurement with an Average detector? It has been suggested to me by a test house that this is the case, but I have not managed to find any rationale for this. The setup for the Analyser in question during the measurent was as follows if this helps: SPAN = 2GHz, RBW =1MHz, VBW = 3MHz, SWEEP =40ms Many thanks. Samantha Ridler BEng MIEE Compliance Engineer Samantha: No, this setup will just give you an average of the detected peaks, which is not the average value of the signals. This was discussed on the list a couple of months ago, and one of our members is currently gathering information on how various labs actually do average testing using a spectrum analyzer. I would suggest you search the recent list archives for a look at that thread. It's my understanding that the spectrum should first be scanned using Peak detection (and a logarithmic amplitude scale) using CISPR bandwidths. This is often done under computer control. After completion of the scan, any peak which exceeds the average limit is individually examined. This consists of retuning to the signal, setting the span to zero Hz, setting the scale to linear amplitude, and setting the video bandwidth to a very narrow value, typically 1 Hz. A few sweeps may need to be made to assure a high order of probability of intercept (should the signal have a low repetition rate), and the amplitude can be recorded or transferred back to the controlling computer. Then you move on to the next peak, and repeat the process. And if there's a smarter way to do this, I await re-education. And that reminds me; how is that survey coming along? Regards, Ed Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [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: http://www.ieeecommunities.org/emc-pstc
