Designing filters: remez?

Hello!

I thought about a graphical filter designer (probably to be integrated
with GRC). I read up about the window method and the Remez method. I
found both in GNU Radio code, but the examples only use the window
method functions. Is there something bad about designing filters with
the Remez method? I thought it would be clever to constraint the filter
to a number of coefficients, as this parameter is most important for
processing speed.

Moreover, what would bring faster results, a designer using the window
method or one with the remez method?

Patrick

Engineers motto: cheap, good, fast: choose any two
Patrick S.
Student of Telematik, Techn. University Graz, Austria

On Thursday, 10. January 2008 20:01, Patrick S. wrote:

method functions. Is there something bad about designing filters with
the Remez method? I thought it would be clever to constraint the filter
to a number of coefficients, as this parameter is most important for
processing speed.

I haven’t had a look at the code, but in general the Remez method is
always
superior. In fact, the last course I had on filter design taught me the
window method is only really used in quick-and-dirty filter design and
in
teaching, because it’s so simple to explain (plus, it’s easier to code).

Moreover, what would bring faster results, a designer using the window
method or one with the remez method?

I doubt the window method can be beaten in terms of speed, as it’s only
an FFT
and a multiplication, but I don’t know how much faster it is.
However, usually the filter design is not in the time critical part of
an
application, whereas the number of taps has direct influence on
performance.
Given the choice, I’d say use remez when possible.

martin


Martin B.
Institut fuer Nachrichtentechnik
Universitaet Karlsruhe

http://www.int.uni-karlsruhe.de

On Fri, Jan 11, 2008 at 01:34:18PM +0100, Martin B. wrote:


Martin B.
Institut fuer Nachrichtentechnik
Universitaet Karlsruhe

http://www.int.uni-karlsruhe.de

The existing GNU Radio wrapper around the remez primitive needs help.
IIRC only the low_pass case works. Perhaps one of you guys can take a
look at it. Creating a few test cases would be great too :wink:

Eric

Eric B. schrieb am 2008-01-11 18:05:

The existing GNU Radio wrapper around the remez primitive needs help.
IIRC only the low_pass case works. Perhaps one of you guys can take a
look at it. Creating a few test cases would be great too :wink:

I found optfir.low_pass with a passband ripple of more than apr. 1
failing. More to come.

Patrick

Engineers motto: cheap, good, fast: choose any two
Patrick S.
Student of Telematik, Techn. University Graz, Austria

On Mon, Jan 14, 2008 at 11:09:25AM +0100, Patrick S. wrote:

Eric B. schrieb am 2008-01-11 18:05:

The existing GNU Radio wrapper around the remez primitive needs help.
IIRC only the low_pass case works. Perhaps one of you guys can take a
look at it. Creating a few test cases would be great too :wink:

I found optfir.low_pass with a passband ripple of more than apr. 1 failing.
More to come.

Patrick

Thanks!

On Monday 14 January 2008 11:09:25 Patrick S. wrote:

I found optfir.low_pass with a passband ripple of more than apr. 1
failing. More to come.

I can confirm that… more than or equal, to be precise.

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