Forums

How to Design a Comb Filter in Matlab

Started by Unknown October 21, 2001
hi to all,
this is really intersting one!!!!!!

If One Input with some Useful Information and Noise and both information and
noise are sinusoidal and i want to remove that noise using Comb Filter then How
can I design a perfect comb filter in Matlab.
I have
freq of information = 200 Hz
freq of noise = 60 Hz
Sampling freq = 500 samples per sec

Design of this filter should have gain such that it can not affect the amplitude
of useful information

can anybody??????????

Thanks in advance
Ojas



An comb filter, or sinc filter, is typically used in highly oversampled
situations because it has a monotonically decreasing passband ("droop")
which is much sloppier than an equiripple FIR design. The advantage of a
comb filter is that it can implement an extremely high dynamic range
(passband-gain / stopband-gain) using only relatively low-precision integer
coefficients. The disadvantage is that the stopbands are relatively
narrow, and the passband has the droop already mentioned.

Comb filters are various cascades of the extremely simple impulse response
[ 1 1 1 .... 1 ], where the length N of the impulse response is usually the
decimation/interpolation ratio.

Your data is scarcely oversampled, and as such I would not use a comb
filter. Or perhaps when you say "comb filter" you really mean an FIR
filter, whereas I think of the specific filter I've been describing.

The best filter for you would be one which has a stopband at 60 Hz and a
passband over your data frequencies. You can use "sptool", which I believe
is part of the Matlab signal processing toolbox, to design such a filter. Sincerely,
Glen Ragan