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Re: [Discuss-gnuradio] gr_remez insufficient extremals


From: Bernardo Guadagnin Gonçalves
Subject: Re: [Discuss-gnuradio] gr_remez insufficient extremals
Date: Tue, 1 Mar 2011 16:39:02 -0300

Thanks Martin,

Thanks for the idea... and, yes, 1kHz for audio stop isn't a good idea. I've reinstalled the 3.2.2 and it really works fine. Anyway, I'll be trying to do a filter as you recommended.

Thanks!
Bernardo

On Tue, Mar 1, 2011 at 5:54 AM, Martin Braun <address@hidden> wrote:
Hi Bernardo,

I'm pretty sure the filter code hasn't changed too much since 3.2.2.
However, I'm surprised it worked before: Your FM demodulator requires a
pretty steep filter (the transition width is less than 0.005 normalised
to the sampling frequency). I only had a quick peek, but since your
decimation in the FM demod is 1, you could use a frequency demod instead
and couple it with your own (custom) filter.
The gr_remez code is a bit unstable in this respect. You normally have
to fiddle around with the parameters until you get a good filter, and
the FM demod block doesn't give you enough knobs.

MB


On Mon, Feb 28, 2011 at 11:25:54AM -0300, Bernardo Guadagnin Gonçalves wrote:
> Hello,
>
>
> Until last week I was using the Gnu Radio 3.2.2 (which is ready for use in
> ubuntu), then I decided to try the latest version (v3.3.1git-147-g5a23954a).
> The flowgraph was working perfectly. It's for "in" GRC simulation only. I know
> it's very simple and the 38kHz recovery (at the receiver) is not the
> recommended way.
>
>
> Flowgraph: http://dl.dropbox.com/u/8898915/FMstereotxrx2.grc
>
> .Wav for simulation: http://dl.dropbox.com/u/8898915/sine4k.wav
>
>
> The messages that are now shown are:
>
>
> Showing: "/home/mula/Dropbox/Public/FMstereotxrx2.grc"
>
>
> Generating: "/home/mula/Dropbox/Public/top_block.py"
>
>
> Executing: "/home/mula/Dropbox/Public/top_block.py"
>
>
> gr_remez: insufficient extremals -- cannot continue
>
> Traceback (most recent call last):
>
>   File "/home/mula/Dropbox/Public/top_block.py", line 361, in <module>
>
>     tb = top_block()
>
>   File "/home/mula/Dropbox/Public/top_block.py", line 193, in __init__
>
>     tau=tau,
>
>   File "/usr/local/lib/python2.6/dist-packages/gnuradio/blks2impl/fm_demod.py",
> line 65, in __init__
>
>     60)   # Stopband attenuation
>
>   File "/usr/local/lib/python2.6/dist-packages/gnuradio/optfir.py", line 53, in
> low_pass
>
>     taps = gr.remez (n + nextra_taps, fo, ao, w, "bandpass")
>
>   File "/usr/local/lib/python2.6/dist-packages/gnuradio/gr/
> gnuradio_swig_py_general.py", line 432, in remez
>
>     return _gnuradio_swig_py_general.remez(*args, **kwargs)
>
> RuntimeError: gr_remez: insufficient extremals -- cannot continue
>
>
> >>> Done
>
>
> Thanks!
>
>
> Regards,
> Bernardo
>

> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio


--
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu

KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association


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