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Synchronization between the TX and the RX signals.

Category: Hardware
Product Number: ADLAM-Pluto

I am currently working on implementing a FMCW radar for SAR application, I have successfully generated, transmitted, received the CWchrip. But when I move to the calculation of the beat frequency by multiplying the Tx and the Rx signals, the beat that I get is moving and not stable as it should be even though the target is stable.

As I read, I found that I need to synchronize the two pulses before beat calculation in order to get the perfect beat frequency. But I don't understand how I synchronize the two pulses.

After reading some papers I kind of got the Idea that I can use a correlator block in GNU radio to sync the signals I want to know how I can do that and if it can be done through software or I need to provide external clock pulse to the pluto sdr using arduino or something. I also saw a paper that said if you know the range you can add a particular delay to your Rx signal as the FPGA delay will be deterministic.

Below is my setup, the results that I am currently getting.


Link to the screen recording showing the moving beat frequency.