I am using AD9361 FMCOMMS3 to sent a 9 MHz DDS signal, and baseband sample frequency is 20MHz.
Below is my settings.
Spectrum is as follow, you can see that there has a peak at -11 MHz from central frequency, I think this is due to my sample frequency is 20 MHz, so there has a peak at -20 MHz + 9 MHz = -11 MHz.
My question is how to eliminate that peak at -11 MHz, or how to decrease the power to less than -50 dB?
Thanks a lot.
p.s. Attachment is the spectrum diagram.