I read a paper years ago regarding this. It stated that whether the measured signal was lower or higher than reality depended on whether the overloading signal was broadband or narrowband in nature. Can't find the paper right now, however.
Bob Richards, NCT. --- On Thu, 12/4/08, Clif Brick <[email protected]> wrote: > From: Clif Brick <[email protected]> > Subject: RE: EMI Receiver > To: "Gert Gremmen" <[email protected]>, [email protected] > Date: Thursday, December 4, 2008, 2:49 PM > I could be wrong as it's been a few years, but it seems > to me that a > spectrum analyzer receiver in overload will show a signal > to be a lower > amplitude than it really is (in addition to ghosts, spurs > and intermod > products). The issue is one of compression, and in fact an > overlaoded > analyzer will show comply when in fact the device is > non-compliant just > as readily as the opposite. > > If an overlaod condition exists, you may get a reading of a > real (from > the EUT) signal that is say 0dBm, you add 10 dB of > attenuation and get > -3dBm. This means that in fact your signal is at least 7dB > larger than > your display. If you add 10 dB more and get say -7, > you're still in > overload. You would need to continue until you get linear > response. > Important to understand is that it may be well outside of > the band of > interest that the overlaoding signal is comin in on. This > is why > preselection helps.... > > Best regards, > Clif > > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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]>
