LimeSDR 2 Rx channels coherent

Hello,

I am trying to receive and record two channels simultaneously on LimeSDR, it is important that they are coherent.
How can i do that?

Thanks,
Mariana

Hello @meo,

Per my understanding, RX channels on LimeSDR (LMS7002M based) are coherent by default because they use the same LO. Everything you probably need, just call a Calibrate function before receiving a signal.

I’m a beginner, so please feel free to correct me if I’m wrong.

Best Regards.

Not so simple. Check this document for more information:
https://github.com/myriadrf/LMS7002M-docs/blob/master/LimeSDR-USB_channel_alignment_v01r00.pdf

1 Like

Hi @Zack,

Thank you for the provided link! It is very good that LimeSuite has such good documentation with a detailed explanation of the problems and its solutions.

Answering the original question and to summarize mentioned in the document info, to set up coherence in the MIMO mode is enough to add the LMS_ALIGN_CH_PHASE flag to the Rx channel numbers and all necessary work will be done automatically by the LimeSuite.

For example:

lms_stream_t rx1;
lms_stream_t rx2;
rx1->isTx = false;
rx2->isTx = false;
...

// We are not interested in coherence.
rx1->channel = 0;
rx2->channel = 1;
...

// Both Rx channels need to be coherent.
rx1->channel = 0 | LMS_ALIGN_CH_PHASE;
rx2->channel = 1 | LMS_ALIGN_CH_PHASE;
...

Could you confirm my understanding?

Hey @Gluttton,

Yeah that is all that’s needed. It’s not necessary to add LMS_ALIGN_CH_PHASE to all RX channels as it will perform the alignment if any of the channels have the flag.

Hi @Garmus,

Thank you for the clarification!