Hi Evgeny, A few months ago, I had I believe a similar situation with the LimeSDR-mini you describe below and show in your attached spectrum plots. Although not a MIMO configuration.
For me the solution was to not use the gnu radio in-tree modulation blocks in gnuradio version 3.8 with the LimeSDR sink block. I used my own modulator blocks for BPSK and later QPSK with the LimeSDR block. I sent a square wave pulse shape baseband signal to the input of the LimeSDR-mini. The full discussion and solution for this work-around with flowgraphs and spectrum plots is on a Lime Myriad RF site thread in August that I established to get some input from the Lime Microsystems folks: "LimeSDR-Mini GR-3.8 Block Transmit Distortion" Regards, Dave ---------- Forwarded message --------- From: Evgeny Hahamovich Date: Thu, Oct 28, 2021 at 11:57 AM Subject: MIMO with LimeSDR To: <discuss-gnuradio@gnu.org> Hi all, I am interested in checking the MIMO (well, actually it's SIMO for now) work mode for my LimeSDR with GNURadio (v.3.8.3.1). Getting into the MIMO mode was simple by setting RxChannel = A+B, but I got stuck just after this... In the attached screenshots you can see the spectrum and constellations I got for QPSK. As you can see, one of the channels offers terrible performance :( Have you encountered something similar? This is strange to me, I didn't expect such a major difference between the 2 channels performance. Maybe I'm doing something wrong... Also, can you advise on some blocks I can use for 2 antenas detection to improve performance or point me to some documentation or examples for using this mode? Thank you, Evgeny
