p5_17.m

来自「Digital Signal Processing-A Computer-Bas」· M 代码 · 共 14 行

%Program ZouyxLabExeSheet_2
%Program to Design Butterworth Lowpass Filter
%
%Type in the filter order and 3-dB cutoff frequency
N=input('Type in filter order = ');
Wn=input('3-dB cutoff frequency = ');
%Determine the transfer function
[num,den]=butter(N,Wn,'s');
%Compute and plot the frequency response
omega=[0:200:20000*pi];
h=freqs(num,den,omega);
plot(omega/(2*pi),20*log10(abs(h)));grid
xlabel('Frequency,Hz');ylabel('Gain,dB');
title('The gain response of the Butterworth lowpass filter');