I've read through the reference manual, EngineerZone posts, the FAQ but don't understand why adjusting the AD9361 RX NCO phase would help the quadrature calibration for TX.
- (AD9361 TX quad cal FAQ) AD9361 Transmit Quadrature Calibration (Tx Quad Cal)
- (AD9361 block diagram) https://wiki.analog.com/_detail/resources/eval/user-guides/ad-fmcomms2-ebz/ad9361.svg?id=resources%3Aeval%3Auser-guides%3Aad-fmcomms2-ebz%3Aad9361
- When I say "RX chain", I'm referring to the components boxed in blue. When I say "TX chain", I'm referring to the components boxed in red.
Does "RX NCO phase offset" refer to phase adjustment of the RX NCOs in the RX chain? Or does it refer to a different/separate knobs that adjusts TX NCOs directly in the TX chain?
If "RX NCO Phase offset" refers to controlling the RX NCOs in the RX chain, I'm concerned that adjusting the RX NCO for calibration isn't valid when the RX and TX links aren't connected. The FAQ linked above says "The Rx NCO Phase Offset compensates for the delay of the signal through the signal path.", but in our application the output of the RX path goes to a modem that decodes bits then encodes bits for the TX path. The path delays on TX can't be compensated by the RX chain so I want to understand how the RX NCO phase helps with the TX IQ imbalance in more detail. I've seen the block diagram linked above but don't see a connection between the RX NCO path and the TX path.
Can someone provide insight, and is there a more detailed block diagram showing the RX NCO phase control and how that connects to the TX chain?
