We are testing a custom board with AD9375. In reception the level change for unknown reason. In the picture below I had the chance to capture it. Raw I and Q data of the same channel are plot. The input signal is a kind of AM, the carrier is at the same frequency as the Rx OL, the modulation is a sine. In this situation, usually the component (I or Q) with the least level is changing, the other stays at a constant level.
What I usually do is to compute the RMS value of a set of received samples, again and again, and the result is changing in less than a second. On the other side I rarely see it happening an a small set of data plotted (which last less than a microsecond).
I have checked the gain, it is manual, and it does not change (anyway it should change both I and Q). I have checked the gain compensation and slicer, they are disabled. I have tried to disable all tracking calibration, the result is the same.
PS. In another situation where the input signal is a CW, at a frequency slightly different from the OL frequency (in such a way that I and Q have the same level), I do not see the same think (I have other problems, by the way).
Can you readback gain and see if there is a gain change.
IF you are seeing this issue happening exactly at LO it could be because of LOL /DC offset calibration.
Cross check if tracking cals are realy disabled.
I have read back gain, and there is no gain change (I am able to switch to automatic gain, and see it changing, then I go back to manual gain, and it does not change any more)
I thought LO-Leakage and DC Offset calibrations are only *initial* calibrations, but here I keep Radio On, and see level change.
I have disabled tracking calibration, and I can read back their status.
Can you share the frequency domain plot of the signal at RX? What is the frequency of the carrier signal with which you are modulating? Can you share the waveform file?
The OL frequency is 300 MHz, but it seems that we have this issue at any OL frequency. The modulation is a custom sine at 480 kHz. I did not save the waveform file, so I can not share the frequency domain plot.
Is this issue resolved. ?
can you try sending signal at 1 MHz offset. ?
What is the level of input signal? Is AGC enabled?