Low Quality Output Signal

[ugy99]

Hello,
I am trying to transmit a pure sine wave with a frequency of exactly 63.795MHz using LimeSuite API. For this, I have written only ones in the tx buffer in the given basicTX.cpp example. However, both the frequency and the shape of signal is very inaccurate. Examining the signal with an oscilloscope, the frequency is 63.76598MHz and its not even close to being a pure sinusoid. What could be the problem here? Below you can find an image of the oscilloscope output.

Thank you,
Ugur.

[TehWan]

There seems to be a lot of harmonics in the signal and the frequency is off by 29 kHz. I’ve had this issue before where the frequency was not as commanded with a lot of harmonics and the signal bandwidth was also wrong.

TX signal sample rate issues

Hey @TehWan, Thanks for posting such descriptive issue. To check the problem out I first did some basic tests using gr-limesdr and NCO. My basic test flowgraph was Noise source->LPF(500kHz)->LimeSDR(TX) on transmit side and LimeSDR(RX)(different board)->QT GUI sink. As expected, the whole signal bandwidth is 1MHz and when I set TX NCO to 1MHz signal moves to the desired location without change of bandwidth. After downloading and trying it with your provided signal I noticed the problem you we…

I was sending too large of a signal to the SDR and it was causing issues. Make sure the samples you send are contained within [-1.0, 1.0[