bendpass.m

关于带通带阻滤波器的设计

[array,fs]=wavread('c:\se144.wav');
T = 1; Fs = 1/T; % Set T=1
%T=2;
Wpl=tan(0.4/2/Fs*pi);
Wph=tan(0.6/2/Fs*pi);
Wsl=tan(0.3/2/Fs*pi);
Wsh=tan(0.7/2/Fs*pi);
Rp = 1; % Passband ripple in dB
As = 40; % Stopband attenuation in dB
%计算模拟低通原型的参数
OmigaP=Wph-Wpl; %低通滤波器通带截止频率
OmigaS=Wsh-Wsl; %低通滤波器通带截止频率
[N,Wn]=buttord(OmigaP,OmigaS,Rp,As,'s');
[B,A]=butter(N,Wn,'s');
[BT,AT]=lp2bp(B,A,sqrt(Wph*Wpl),Wph-Wpl);%低通转带通
[b,a]=bilinear(BT,AT,Fs);%双线性变换
H=freqz(b,a,80000,'whole');
figure(1);
plot(abs(H));
y=filter(b,a,array);%信号通入滤波器，y为输出
fftwave=fft(y);%快速傅立业变换
figure(2)
plot(abs(fftwave));%显示频率响应
figure(3);
freqz(y);%显示y的幅频和象频特性
wavwrite(y,fs,'c:\bendpass.wav');