On Tue, Dec 06, 2005 at 06:16:32PM -0500, [EMAIL PROTECTED] wrote:
> On Tue, 6 Dec 2005 14:24:43 -0800, Eric Blossom [EMAIL PROTECTED] wrote:
> > Quick answer:
> >
> > use the defaults.
> >
> > Involved answer:
> >
> > It's a Mueller and Müller (M&M) discrete-time error-tracking
> synchronizer.
> >
> > See "Digital Communication Receivers: Synchronization, Channel
> > Estimation and Signal Processing" by Heinrich Meyr, Marc Moeneclaey, &
> Stefan Fechtel.
> > ISBN 0-471-50275-8.
>
> I should have seen that answer coming.
In certain areas, I'm quite predictable ;)
> I am trying to get the book, no luck so far.
Amazon carries it.
> The default values dont seem to work.
>
> What should the data going in and out of the gr.clock_recovery_mm_ff look
> like?
Probably the easiest thing is to modify gmsk_test.py and add code to
write the signals you're interested in to files using gr.file_sink.
That's how we debugged it.
In gmsk_test.py, make main look like this: (untested, but probably pretty
close)
fg = my_graph(rx_callback, options.spb, options.bt, options.snr,
options.freq_error)
fg.connect(fg.packet_receiver.gmsk_demod.sub,
gr.file_sink(gr.sizeof_float, "before_clock_recovery.dat"))
fg.connect(fg.packet_receiver.gmsk_demod.clock_recovery,
gr.file_sink(gr.sizeof_float, "after_clock_recovery.dat"))
fg.start()
Then after it runs, you can read the binary log files into octave and
display them as you like.
In your ~/.octaverc add (modify as required for your gnuradio build directory):
LOADPATH=":~/gr-build/gnuradio-core/src/utils";
$ octave
>>> before = read_float_binary("before_clock_recovery.dat", 4e6);
>>> after = read_float_binary("after_clock_recovery.dat", 4e6);
>>> plot(before(1:1000));
>>> plot(after(1:1000));
> I see that in gmsk2.py you remove DC offset, should the signal be varying
> +/-Vpeak equally?
Yes, pretty close.
> Any requirements that the signal should be over sampled?
The sample rate needs to be at least 2x the data rate.
> Is the output basically resampled at the data clock rate so that each
> output point represent a bit?
Yes.
Eric
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
