MATLAB: Design Notching Filter for different frequencies

Question

Hi,

I want to design a filter with Notches in different frequencies. The MATLAB give the option for one Notch only:

F0 = 60;   % interference is at 60 Hz
Fs = 3000; % sampling frequency is 3000 Hz
BW=1;
f = fdesign.notch('N,F0,BW',2,F0,10,Fs);
h = design(f,'SystemObject',true);
hfvt= fvtool(h,'Color','white');

Any idea how to filter the other frequencies?

Answer 1

You can use dfilt.cascade to combine filters in series.

In the following code, I create two notch filters, and cascade them together.

F0 = 60;   % interference is at 60 Hz
Fs = 3000; % sampling frequency is 3000 Hz
BW=1;
f = fdesign.notch('N,F0,BW',2,F0,10,Fs);
h = design(F);
hfvt= fvtool(h,'Color','white');
f2 = fdesign.notch('N,F0,BW',2,F0+300,10,Fs);
h2 = design(f2);
hfvt= fvtool(h2,'Color','white');
hd = dfilt.cascade(h, h2);
hfvt= fvtool(hd,'Color','white');