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From: David Cubero on 30 Jun 2010 10:50
Hello, I have implemented a notch filter to remove sinusoidal interference

wo = 2 * pi * Fi /Fs
b = [ 1 -2cosw0 1 ];
a = [1 -2rcoswo r^2];
clf, freqz ( b,a,NFFt,Fs);
tittle ( "...."), pause

How can I do to use a notch filter to remove DC????
thank you
From: Wayne King on 30 Jun 2010 11:19
"David Cubero" <sirdivi(a)hotmail.com> wrote in message <i0flj6$crh$1(a)fred.mathworks.com>...
> Hello, I have implemented a notch filter to remove sinusoidal interference
>
> wo = 2 * pi * Fi /Fs
> b = [ 1 -2cosw0 1 ];
> a = [1 -2rcoswo r^2];
> clf, freqz ( b,a,NFFt,Fs);
> tittle ( "...."), pause
>
> How can I do to use a notch filter to remove DC????
> thank you

Hi David, how about just making your signal zero mean. That will set the value of \omega = 0 to be zero.

sig = 10+randn(100,1);
mean(sig)
sig = detrend(sig,'constant');
mean(sig)


Wayne
From: David Cubero on 30 Jun 2010 11:35
i need to use a notch filter, sorry, thank you very much
From: Wayne King on 30 Jun 2010 11:50
"David Cubero" <sirdivi(a)hotmail.com> wrote in message <i0fo7a$7k4$1(a)fred.mathworks.com>...
> i need to use a notch filter, sorry, thank you very much

Hi,
How is removing the mean not a notch filter for DC? The Fourier coefficient at DC is just the sum of the elements in the data vector.

Wayne
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