assignment_3.m

来自「Digital Signal Processing-A Computer-Bas」· M 代码 · 共 19 行

%Butterworth带通滤波器的设计
%估计滤波器阶数
[N,Wn]=buttord(1,2.9021128,1,32,'s');
%设计滤波器
[B,A]=butter(N,Wn,'s');  %Butterworth analog LPF
[BT,AT]=lp2bp(B,A,0.6084340,0.2170171);  %Spectral transform from analog LPF to analog BPF(center frequency &bandwidth)
[num,den]=bilinear(BT,AT,0.5);  %Bilinear transform to obtain the digital BPF 
%显示传输函数
disp('分子系数是');disp(num);
disp('分母系数是');disp(den);
%计算增益响应
[h,omega]=freqz(num,den,256);
gain=20*log10(abs(h));
%绘制增益响应
plot(omega/pi,gain);grid
axis([0 1 -40 5]);
xlabel('\omega/\pi');
ylabel('增益,dB');
title('Butterworth带通滤波器的增益响应');