[Discuss-gnuradio] undersampling with USRP

[Jonathan Gill]

Hi all,

 

I’m having some problems with sub-sampling signals using with the USRP.  I currently have the board connected to a signal generator with a sinusoidal input at 0dBm.  I’m using the usrp_rx_cfile.py script from USRP examples with the -8 –s and --no-hb flags and a decimation of 4 and –f 0 (no down conversion).

 

This gives me an output file with interleaved I and Q samples (with one set being empty due to –f 0), this works fine up to Nyquist frequency (8MHz, as sampling frequency is 64/4 = 16MHz) but beyond this the operation is not as expected.  At 10MHz I expect to see a single sinusoidal component at 6MHz, however this is corrupted by a strong component at 2MHz, and at any frequency above 10MHz no signal is recorded.  Any suggestions?  (I have checked the signal generator, it is working fine)

 

Thanks for your help

 

Jon

 

 

--========================================

Jon Gill

address@hidden

CAA Institute of Satellite Navigation

University of Leeds

Tel: +44 (0) 113 343 2025

==========================================