AD9371 ADC I/Q imbalance

What is the level of the signal at image frequency that you are observing at 4800MHz and 2400MHz LO?

Is QEC calibration failing at both the frequencies?

Thanks for your reply. Last time I saw it at 4800MHz LO, the amplitude of in-phase is 8000 and quadrature is 10000, which is about 20db. It is random. QEC calibration is always success.

Can you share the time domain plot of  I Q signal which shows the imbalance  at 4800MHz and 2400MHz LO.

You can try disabling the quad tracking cal and then check so as to ensure that the difference in amplitude is not because of it.

This is at 4800MHz LO.

I tried what you suggested. I run the setup with qec disabled, and the problem exist as well. And I wrote a loop to enable qec and disable qec for every 60 sec, and if it is imbalance after the initial setup, it will remain imbalance. 

So do you think it is a problem of qec, or something else?

The imbalance if happening within the chip can happen only after the mixer. QEC does correct amplitude of IQ signals but it cannot create such condition.

This can be because of power supply which is causing the chip to misbehave . You can check the power lanes and also the reference clock.

Are you seeing this on both Rx1 and Rx2 ?

Is your TX path working correctly.? 

I see this sometimes on Rx1, sometimes on Rx2, but never simutaniously. Tx path is working, but I haven't measured its performance.

hi @yangzhaojun， I meet the same IQ imblance problem , how to solve? thanks a lot