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TR Module testing

Question asked by nsm on Mar 23, 2012
Hi all,

I am testing a TR module in the L band. The transmit o/p  power is 40W and the pulse width is 10us and the PRF 4KHz. I am using the E8362C with the Z5623A H81 pulse modulator. I have a transfer switch between the TR module and the network analyzer to switch out the attenuator when doing receiver measurements.

I need to do the measurements in the following conditions. I am using the N4691B option 00F ecal module for calibration.

Transmitter : Measurement to be done at an i/p of -25dBm, 10us pulse width and 4KHz PRF. 
I am using narrow band detection for this measurement set up. I have a 20dB attenuator at the o/p and also I have the 25dB receiver switched in on the B receiver.For doing the cal, I have set the power level to 0dBm and doing an enhanced response cal. I find that the cal is very noisy and the peak to peak variation on S21 mag is close to 1.5dB. Why is this happening?Is there any way I can improve the cal?

Receiver. Measurement to be done at an i/p of -70dBm, 160us pulse width and 4KHz PRF.Gain is around 60dB

For this measurement, I switch out the 20dB attenuator. The calibration is good in this mode and I do the calibration at -40dBm. I do a full 2 port cal.

However since the measurment needs to be done at -70dBm input, will there be noise in the measurementof S21?What is the SNR of the signal generated by the PNA? I find that the S21 mag and phase trace is very noisy.

Please let me know as to how I can get a good measurement and cal. 

Will using smoothing and averaging a good option. Is smoothing recommended?