if using the AD9361 for qpsk, bpsk and qam inputs can and how would it perform carrier recovery?
AD9361 does not have a built in carrier recovery circuit. Estimation and compensation for phase and frequency difference between the carrier and LO would have to be done off chip.
I am using Zedboard + FMCOMMS3 and I would also like to do qpsk/bpsk coherent demodulation and for that I need carrier recovery. If I implement Costas Loop (or any other suitable loop) in PL (Programmable Logic) of Zynq how my loop can interact with LO at Rx path of AD9361. As long as I can see, LO of AD9361 is controlled though SPI settings by PS (Processing System) of Zynq, due to that I doubt that I can perform LO regulation in real time.
What is suggestion how to implement carrier recovery and how to integrate the loop and LO?
I'm also using the ZedBoard with FMCOMMS3. Trying to implement QAM. I have the same issue.
I have written my own SPI in the PL as an AXI slave and modified the C code that AD provides to use the custom SPI peripheral rather than the PS's SPI (I did it since I wanted more control over the AD9361 from my RTL code).
Therefore, I guess I will have to see what registers that the C code writes to when you change the LO frequency and emulate the same writes in order to dynamically change the LO frequency.
My question is, is that going to be fast enough? And will there be any stability issues due to the digital nature of the VCO control over SPI as opposed to a traditional analog type control (any phase jumps etc. when changing LO frequency).
Have you solved the issue?
SPI Writes typically do not lend themselves well for real time device control due to the finite speed of the SPI interface, number of SPI Writes required and the asynchronous nature of the SPI interface.
If you have a need for real time LO control consider using external LO inputs.
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