Speaking for myself only, I need more info. How good of a job of matching source and load to the 150 Ohm plate did you do? While the electric field is constant and perpendicular to the plates, the magnetic field has some curvature to it, where you make the measurement (and with how large a loop) makes a difference in the answer you get. In fact I would try different size loops, starting with very small. Up to some point you should get correlatable answers, but then you will see problems with a larger loop. And I may be way off base on this one (others please correct me if so) but at some point a grounded element protruding into the center of the cavity may disturb the field structure enough to invalidate the measurement.
---------- >From: Jochen Feldhaar <[email protected]> >To: [email protected] >Subject: Measuring inside a TEM cell >Date: Wed, Nov 20, 2002, 11:25 AM > > > Hello all, > > I have a problem regarding E and H field generation inside a TEM cell. I > have built a standard cell with Zw of 150 Ohms, which I need to generate > a known magnetic field strength around 90 MHz. The separation of the top > and bottom conductor is 25 cm, the overall length is about 130 cm. > > But I don't get the expected results, only at lower frequencies up to 20 > MHz the results are usable. At higher frequencies I suspect that I get a > standing wave inside my room, or that the cell dimensions in itself are > so large compared to the wavelength, that I get an unwanted resonance > inside the cell. > > I have been looking for material about this in the 'net, but so far I > have not found pay dirt..... > > What am I missing here??? > > Greets > Jochen Feldhaar > Telejet GmbH > > > ------------------------------------------- > 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: > 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://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > ------------------------------------------- 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: 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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
