fir_hp.m

FIR滤波器设计

function FIR_HP

clear
clc
Wp=0.6*pi;
Ws=0.4*pi;
tr_width=Wp-Ws;                         %过渡带宽度
N=ceil(6.2*pi/tr_width)                        %滤波器长度
n=0:1:N-1;
Wc=(Ws+Wp)/2;                         %理想低通滤波器的截止频率

hd=ideal_hp(Wc,N);                      %理想低通滤波器计算,hd=0-(N-1)之间的理想脉冲响应,wc＝截止频率（弧度）,N=理想滤波器的长度
wd1=hanning(N)';b1=hd.*wd1;
wd2=hamming(N)';b2=hd.*wd2;
wd3=blackman(N)';b3=hd.*wd3;
wd4=kaiser(N)';b4=hd.*wd4;

[db1,mag1,pha1,w]=freqz_m(b1,1);%汉宁窗
delta_w=2*pi/1000;
Ap1=-(min(db1(Wp/delta_w+1:1:501)));         %实际带通波动
As1=-round(max(db1(1:1:Ws/delta_w+1)));         %实际阻带纹波


[db2,mag2,pha2,w]=freqz_m(b2,1);%海明窗
delta_w=2*pi/1000;
Ap2=-(min(db2(Wp/delta_w+1:1:501)));         %实际带通波动
As2=-round(max(db2(1:1:Ws/delta_w+1)));         %实际阻带纹波
[db3,mag3,pha3,w]=freqz_m(b3,1);%blackman
delta_w=2*pi/1000;
Ap3=-(min(db3(Wp/delta_w+1:1:501)));         %实际带通波动
As3=-round(max(db3(1:1:Ws/delta_w+1)));         %实际阻带纹波
[db4,mag4,pha4,w]=freqz_m(b4,1);%kaiser
delta_w=2*pi/1000;
Ap4=-(min(db4(Wp/delta_w+1:1:501)));         %实际带通波动
As4=-round(max(db4(1:1:Ws/delta_w+1)));         %实际阻带纹波
figure(1)
stem(n,hd);
title('理想脉冲响应')
axis([0 N-1 -0.4 0.5]);xlabel('n');ylabel('hd(n)');

figure(2)
subplot(2,2,1)
plot(w,mag1,':b')
legend('汉宁窗高通滤波器')
subplot(2,2,2)
plot(w,mag2,'-.g')
legend('海明窗高通滤波器')
subplot(2,2,3)
plot(w,mag3,'--r')
legend('布来克曼窗高通滤波器')
subplot(2,2,4)
plot(w,mag4,'-c')
legend('凯泽窗高通滤波器')

figure(3)

plot(w,mag1,':b',w,mag2,'-.g',w,mag3,'--r',w,mag4,'-c')
legend('汉宁窗高通滤波器','海明窗高通滤波器','布来克曼窗高通滤波器','凯泽窗高通滤波器')


figure(4)
plot(w/pi,20*log10(mag1),':b',w/pi,20*log10(mag2),'-.g',w/pi,20*log10(mag3),'--r',w/pi,20*log10(mag4),'-c')
legend('汉宁窗幅度响应（dB）','海明窗幅度响应（dB）','布来克曼窗幅度响应（dB）','凯泽窗幅度响应（dB）')
figure(5)
plot(n,b1,':b',n,b2,'-.g',n,b3,'--r',n,b4,'-c')
legend('汉宁窗h(n)','海明窗h(n)','布来克曼窗h(n)','凯泽窗h(n)')