www.gusucode.com > signal 案例源码程序 matlab代码 > signal/IIRFilterImpulseResponseLengthSecondOrderSectionsExample.m

    %% IIR Filter Effective Impulse Response Length -- Second-Order Sections
% Design a 4th-order lowpass elliptic filter with a cutoff frequency of $0.4\pi$ 
% rad/sample. Specify 1 dB of passband ripple and 60 dB of stopband attenuation. 
% Design the filter in pole-zero-gain form and obtain the second-order section 
% matrix using |zp2sos|. Determine the effective impulse response sequence length 
% from the second-order section matrix.

% Copyright 2015 The MathWorks, Inc.


[z,p,k] = ellip(4,1,60,.4);
[sos,g] = zp2sos(z,p,k);
len = impzlength(sos)