AnsweredAssumed Answered

Understanding Tx Quad Cal

Question asked by jeffkt2 on Sep 28, 2016
Latest reply on Oct 3, 2016 by Vinod



I'm testing an application on the fmcomms2 using No-OS drivers provided. I'm observing quite a bit of LO leakage, so I'm trying to understand how the Tx Quad Cal works. As I understand, LO leakage is caused by IQ DC offsets. 


After reading all the resources I could find on Tx quad calibration, I'm still really confused. Below two references describe how to perform calibration and how the auto cal is implemented in the No-OS drivers:

AD9361 Transmit Quadrature Calibration (Tx Quad Cal) 

ad9361 tx quad cal recommended procedure -vs- driver implementation 


Can someone explain to me in painful detail how this calibration is done? What role does the Rx NCO play in this? How does changing the Rx NCO phase offset adjust LO leakage?