Hello all,
I am doing CW Transmit measurement in a shielded room. I have 3 receiver antennas (Helical) in V, H, and 45deg polarization and DUT is a ZigBee module. I see path loss of 5dB variation in an ISM band. Ideally, path loss should almost be the same with little variation. I added more absorbers to reduce the Q of the shielded room. It improves at a certain frequency but not all. I do not understand the reason for variation in path loss. looking for suggestion.
In a shielded room the signal will be reflected from all the surfaces. Corners behave as corner reflectors (retro-reflectors). You will see multiple images of the transmit and receive antennas, and 45 turns to -45 in a (single) reflection in a vertical or horizontal surface. Signals to and from all these paths (images) add and interfere (which means add or subtract). From your description you are looking for just the direct path measurement. You probably need more RAM. It's not enough to reduce the Q, you need to stop reflections.
Hi.,
Refer this link:
https://core.ac.uk/download/pdf/9848473.pdf
Best wishes..
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