LMS7002M issue with close Tx-/Rx-frequency

Projects LimeSDR
1

we currently face a problem with the LMS7000m chip when we use Tx- and Rx- for a channel where we have a slight frequency offset (e.g. 5 kHz offset between Tx and Rx).

We can reproduce the issue with the Lime suite and a LimeSDR USB board. See the attached ini-Files for the three VCOs.

If we configure the LimeSDR with the attached ini-Files, then we see the strong influence of the RX-VCO on our Tx-signal. Is there anything we could do to solve this issue?

Best regards,

2

Rx VCO could be disabled, and switched to use Tx’s VCO, that would eliminate the interference, and make Rx/Tx LO to be the same frequency. Then you can configure either Rx or Tx NCO to digitally offset the channel by the 5kHz.