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Re: [Discuss-gnuradio] Efficient notch filters
From: |
Martin Dvh |
Subject: |
Re: [Discuss-gnuradio] Efficient notch filters |
Date: |
Tue, 31 Jul 2007 01:29:02 +0200 |
User-agent: |
Icedove 1.5.0.12 (X11/20070607) |
Marcus Leech wrote:
> Is there a way to produce an efficient notch filter with the bandpass
> filter designer in Gnu Radio?
You can use a resonating IIR filter for that.
They are very efficient for building a notch or narrowband filters (single out
a single frequency)
The filter designers in gnuradio can not design it yet for you unfortunatly.
(I am working on source which can design them.)
I do already have an optimized implementation of a resonating IIR filter.
(Several of the taps are +1, -1 and 0)
See:
http://www.olifantasia.com/projects/gnuradio/mdvh/iir/
This filter only uses 2 multiplies to get very nice and narrow filters.
ALso note that the current standard multitap IIR implementation probably has a
bug, (See my mail with a fix for that in the mailinglist archive)
Greetings,
Martin
>
> I'm seeing narrowband interfering signals that are in-band (with respect
> to the bulk filtering in front
> of the receiver), and I want to notch one or more of them into
> oblivion. I'd previously used an
> FFT filter, and set zeros in the bins where I wanted notches, but it
> wasn't very efficient.
>
>
>
>
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