www.gusucode.com > dsp 案例源码程序 matlab代码 > dsp/CompareNotchFiltersOfDifferentOrdersExample.m

    %% Compare Notch Filters Designed with Different Orders
% Design an eigth-order notch filter and compare it to a traditional
% second-order notch filter designed with |IIRNOTCH|. 

% Copyright 2015 The MathWorks, Inc.

Fs  = 44.1e3;
N   = 8;
G   = -inf;
Q   = 1.8;
Wo  = 60/(Fs/2); % Notch at 60 Hz
BW  = Wo/Q; % Bandwidth occurs at -3 dB for this special case
[SOS1,SV1] = iirparameq(N,G,Wo,BW);  
[NUM,DEN]  = iirnotch(Wo,BW); 
SOS2 = [NUM,DEN];

%%
% Design the notch filters using the SOS and SV values.
BQ1 = dsp.BiquadFilter('SOSMatrix',SOS1,'ScaleValues',SV1);
BQ2 = dsp.BiquadFilter('SOSMatrix',SOS2);

%%
% Plot the magnitude response of both filters. The filters
% intersect at -3 dB point.
FVT = fvtool(BQ1,BQ2,'Fs',Fs,'FrequencyScale','Log');
legend(FVT,'8th order notch filter','2nd order notch filter');