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Post subject: TEM alternate
Posted: Thu Sep 29, 2005 10:53 am
I saw an interesting question on another forum (won't mention since probably against policy) that I'd like to pose here.
"As an alternate to a TEM cell, we're exploring the idea of using a waveguide-below-cutoff as a means of creating a controlled environment for receiver sensitivity measurements. The receiver is within cellphone-sized package and contains a loop antenna. The receive frequency is roughly 900 MHz.
The thought is to construct a simple tubular rectangular metal structure with height and width dimensions appropriate to prevent waveguide propagation, supposedly providing a steep attenuation characteristic to an incident field at 900 MHz. One end of the tube would be open and allow placement of the receiver in a tightly controlled position within the tube. The other end of the tube would be closed off by a metal plate containing a panel-mount coaxial connector attached by cable to a signal generator.
The thought is to terminate the other end of the connector with some sort of a load appropriate to the generator (50 ohm wirewound resistor?) creating a field within the tube that would rapidly decay.
The generator level, length of the tube, and position of the receiver within the tube would be experimentally determined (using a known good receiver) to be appropriate for threshold testing of subsequent receivers.
Does the concept have merit? Any comments/suggestions would be most welcome."