Some FM modulator questions

Hi all

Sorry if this question is stupid. I want to generate an FM signal as
it would be seen by the adc_interface part on the USRP board after
coming from the TVRX module and then the ADC. So obviously that would
be an FM signal sitting at 20MHz, sampled at 64MHz and quantisized to
12-bits. Does anyone have any good ideas on doing this? What I am
trying at the moment is to decode an mp3 using sox and grabbing 32kHz
mono PCM samples. I then need to get this to an FM signal sampled at
64MHz before mixing it up to 20MHz. I’m struggling with the FM
modulation part. I have in the past used the FM modulator in
Gnuradio, but only to get the sampling rate up from 44.1kHz to 441kHz
when modulating an mp3. I’m using this block:

fmtx = blks2.wfm_tx(32000,64000000,tau=75e-6, max_dev=75e3)

The problem is with the 64000000 part. Interpolating a 32kHz signal
to 64MHz not funny. I’m trying to do it in Gnuradio and my
application has been running for the last hour. DOes anybody have any

Thank you very much.


Sebastiaan H.
Radar and Remote Sensing Group, University of Cape Town
Tel: +27 83 305 5667