Hello All, I am using X310 USRPs. I did a loopback test with this USRP, that is, Tx was connected to Rx (with a 20dB attenuator between them). This is for checking the channel status.In my test, Tx is free running without stop, and Rx is occasional. Both transmission and capture are time-based, that is, signals are transmitted at specified time, and capture starts at specified time. Master clock rate: 184.32MHzSampling rate: 184.32MHz Using the captured signals, I can calculate the channel coefficient. A few captures were made. I expected constant channel because it was cable connection and it was in the same USRP, but I found that the constellations of the pilot signals rotated when comparing different captures. I think this can be caused by the phase difference between Tx LO and Rx LO, but not sure. Questions:1. are there independent LOs for Tx and Rx in a USRP?2. Is the Rx LO on and off in test, that is, it starts when capture starts and stops when capture is completed? So, the LO phase offset between Tx and Rx is random? Any feedback will be highly appreciated. Kind regards,Hongwei
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