X-band DRO Design pHEMT noise issue

Hi,

I am in hte middle od evaluating a pHEMT based DRO design that I recently got built. it is part of a simple RF radar detector that I am experimenting on within the uni lab.

I have noticed a strange effect. When I log into my baseband circuit for a couple of hours during an overnight soak, I sometimes get a burst in noise in my receive signal.

I have tried to root cause this by looking at power supply, RFI and IF,baseband op-amps and I have seen that it seems to be related to DRO.

What would cause a DRO to misbehave or appear noisey for a short period of the time, effectively it ooks like burst of noise for 5minutes duration and can happne 3-4 times over a 12 hour soak.

any suggestions as I have been looking at hte DRO, which is based on a standard DRO design?

Have you ever tough the screening precautions ?There might be a transmitter such as GSM basestation or some other wireless activities.