On Tue, Jun 28, 2011 at 4:48 PM, Minhoo Kim <ki...@purdue.edu> wrote:
> > Hello, I'm new to this mailing list and gnuradio. > sorry if I fail follow certain etiquettes.. > what I'm trying to do now is to have a transmitter that hops around under > 1ms, which needs to have 1MHz bandwidth and hop around in 10MHz range total > (at least). > the problem I'm having is that I can't get the USRP motherboard to generate > that high of frequency. > I need the motherboard to generate at least up to 10MHz range because the > signal needs to be hopped around pretty fast.. > and has to be passed on to 2.4GHz range using RFX2400. > This is the error message I get: > > File "multiplytest.py", line 86, in <module> > test_signal = my_top_block() > File "multiplytest.py", line 46, in __init__ > fmtx = blks2.nbfm_tx (self.sample_rate/10, self.sample_rate, tau=75e-6, > max_dev=1e5) > File "/usr/lib/python2.6/dist-packages/gnuradio/blks2impl/nbfm_tx.py", > line 69, in __init__ > 40) # stopband atten dB > File "/usr/lib/python2.6/dist-packages/gnuradio/optfir.py", line 44, in > low_pass > taps = gr.remez (n + nextra_taps, fo, ao, w, "bandpass") > File > "/usr/lib/python2.6/dist-packages/gnuradio/gr/gnuradio_swig_py_general.py", > line 352, in remez > return _gnuradio_swig_py_general.remez(*args, **kwargs) > RuntimeError: gr_remez: insufficient extremals -- cannot continue > > i looked up gr_remez, and I haven't really found a solution to get USRP to > have 10MHz bandwidth. > I did find that the frequency has to do with self.sample_rate, and the > highest rate I got was 2 Mega, which in turn can generate up to 1MHz > because > of the nyquist rate. > I know the interpolation rate has to be in multiples of 4 ( 4, 8, 12, ...) > and the USRP rate hast to be 128Mega to match the USB data flow rate (I > don't know if that's the right term). > I have my code attached. > Another way I'm looking at is to change the center frequency of the > daughterboard, but I haven't been able to figure out to make that happen > fast enough. > > so the questions are, > How to get the sample rate up to the maximum (which should be 32MHz in > theory)? > > How to retune the daughterboard while it's running? > > > Any help/suggestions would be great! > > I am using USRP1 and RFX2400. > > http://old.nabble.com/file/p31947513/multiplytest.py multiplytest.py > > Thanks for reading this. > > -- > View this message in context: > http://old.nabble.com/How-to-retune-a-daughterboard-bring-up-the-sample-rate-on-USRP--tp31947513p31947513.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > Hi Minhoo, * By 10MHz, do you mean -10MHz to 10MHz at baseband or -5MHz to 5MHz. The former requires a sampling rate of at least 20MHz, which the USRP cannot do. The latter requires 10MHz, which the USRP can do. This restriction on sampling frequency is due to the USB bandwidth. * At best the USRP can do -8MHz to 8MHz at baseband, or 16MHz sampling. Check out the pfb (polyphase filter banks) based blocks for dealing with multi-rate applications --Colby
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