南理工数字信号处理课程实验报告.docVIP

数字信号处理project

实验报告

学院：电子工程与光电技术学院

专业：通信工程

学号：

姓名：

IIR低通滤波器设计

滤波器要求：

Usingbilineartransformmethods,designaIIRlow-passfilterwiththefollowingspecifications:

(1)Writeaprogramtocomputetherequiredorderofthe

ButterworthorChebyshevanalogfilters;

(2)Usingbilineartransformmethods,transformtheanalogfiltersto

thecorrespondingdigitalfilters;

Sketchthefrequencyresponseofthefilters.

2.滤波器设计程序如下：

wp=0.25*pi;

ws=0.45*pi;

Wp=tan(wp/2);

Ws=tan(ws/2);

ap=0.5;

as=20;

[N,Wn]=cheb1ord(Wp,Ws,ap,as,s);

[B,A]=cheby1(N,1,Wn,s);

[num,den]=bilinear(B,A,0.5);

[h,w]=freqz(num,den);

subplot(211);

plot(w/pi,20*log10(abs(h)));

ylim([-505]);

xlim([01]);

xlabel(\Omega/\pi);

ylabel(增益（dB）);

title(幅度响应曲线);

grid;

[h,w]=phasez(num,den);

subplot(212);

plot(w/pi,h/pi*180);

xlabel(\Omega/\pi);

ylabel(phase(degree));

title(相位响应曲线);

grid;

其中，wp,ws是角频带边界频率，Wp,Ws是模拟低通滤波器的边带角频率，ap是通带波纹，as是阻带波纹，h是频率响应。

幅度相位响应波形如下：

FIR低通滤波器设计

滤波器要求：

Designalow-passFIRfilterbywindowing,thespecificationsofthefilterare

Pleaseusingtwodifferentwindowsdesignthefilter,andsketchtheirfrequencyresponse.

滤波器设计程序如下：

clear;

fp=845;

fs=1005;

Fs=4000;

as=45;

wp=(fp*2*pi)/(Fs);

ws=(fs*2*pi)/(Fs);

wc=(wp+ws)/2;

dw=ws-wp;

%Hamming

M=ceil(3.32*pi/dw);

N=2*M+1;

b=fir1(N,ws/(2*pi));

[H,w]=freqz(b,1,512);

figure(1);

stem(b);

title(冲激响应);

xlabel(Time-index-n);

ylabel(h[n]);

figure(2);

plot(w/pi,20*log10(abs(H)));

grid;

xlabel(\omega/\pi);

ylabel(增益（dB）);

title(幅度响应);

axis([01-8010]);

[H,w]=phasez(b,1,512);

figure(3);

plot(w/pi,H/pi*180);

grid;

xlabel(\omega/\pi);

ylabel(phase(degree));

title(相位响应);

%Blackman

M=ceil(5.56*pi/dw);

N=2*M;

b=fir1(N,ws/(2*pi),blackman(N+1));

[H,w]=freqz(b,1,512);

figure(4);

stem(b);

title(冲激响应);

xlabel(Time-index-n);

ylabel(h[n]);

figure(5);

plot(w/pi,20*log10(abs(H)));

grid;

xlabel(\omega/\pi);

ylabel(增益（dB）);

title(幅度响应);

axis([01-20010]);

[H,w]=phasez(b,1,512);

figure(6);

plot(w/pi,H/pi*180)