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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
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
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
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