Good members of the regulatory Jedi Council :-) How about a few thought-provoking questions.
Let's say that you have a high resolution imaging system. The system has a focal plane array that detects IR radiation...the signals from this array are read out as a clocked analog data stream. i.e. each pixel gives an analog value when it is read. This clocked analog stream goes through an A/D converter. The sampling/clock rates are all set so that the eventual output of this imager is a completely digital data stream that is sent out as NSTC video. The video is piped out of the imager to a display via coax cable. Here's the problem. The display shows what appears to be a "light snow-like" noise. I'm thinking about some analytical and measurement methods that could be used to track down the noise source. What would happen if I fed the video signal directly to a Spectrum Analyzer??? I'm assuming that I would have to install a "pad" on the spectrum analyzer input to attenuate the signal and help to impedance match the 75 Ohm coax with the 50 Ohm spectrum analyzer input. It seems to me that we may be able to detect some frequency peaks that persist even if we change the scene that the camera is looking at...maybe these peaks would point us toward the noise source in our system? What about an FFT? What would be the feasibility of grabbing a subset of the data and performing an FFT on it? Since the noise is all over; it doesn't seem to me that we would have to perform the FFT on all 65,000 points of pixel data. Maybe we could use a 100x100 subset near the center of the image? Of course, I've also instructed my friend who is working on this to run a wet finger over the circuits while the video is running to see if he can crudely locate the noise source by looking for a change in the snow on the screen. Here's another question for those of you who are more familiar with video than myself. Is there an intuitive method of homing in on the noise freqencies by looking at how the noise appears? For instance, our noise is a sort of granular "snow" that drifts on the screen...it doesn't stay still. Thanks in advance for any tidbits that you may turn up. Chris Maxwell, M.Sc Electrical Engineer Critical Imaging LLC [email protected] 315-732-1544 x127 www.criticalimaging.net - 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/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
