I’m sending generated DE-QPSK frames in a loop and I’m relying on hardware to control the rate. I’ve set a TX sample rate of 108 kSps (108e3), yet with the LimeSDR-USB, it seems to transmit the signal at 10 Msps (10e6). I have tried different SDRs (B200, N200) and they do not have this issue (though signal quality is much lower compared to the LimeSDR – lots of aliasing on TX).
I am using SoapySDR with a straightforward setup. I have a fixed symbol rate and I do interpolation of my signal (8 times) to get the 108 kSps rate.
This is all verified through a spectrum analyzer (Agilent CSA Spectrum Analyzer N1996A).