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

    %% IIR Filter Effective Impulse Response Length --- --- Digital Filter
% Use |designfilt| to design a 4th-order lowpass elliptic filter with
% normalized passband frequency $0.4\pi$ rad/sample. Specify 1 dB of
% passband ripple and 60 dB of stopband attenuation. Determine the
% effective impulse response sequence length and visualize it.

% Copyright 2015 The MathWorks, Inc.


%%

d = designfilt('lowpassiir','FilterOrder',4,'PassbandFrequency',0.4, ...
               'PassbandRipple',1,'StopbandAttenuation',60, ...
               'DesignMethod','ellip');
len = impzlength(d)
impz(d)