数字信号处理大作业.docx

1、数字信号处理大作业数字信号处理大作业第二次大作业1.n=0:10;x=(-0.9).n;h=-400:400;w=(pi/100)*h;Xjw1=x*(exp(-j*pi/100).(n*h);subplot(2,2,1);plot(w/pi,abs(Xjw1);grid on;xlabel(w1/pi);ylabel(|X(jw1)|);title(幅度特性);subplot(2,2,2);plot(w/pi,angle(Xjw1)/pi);xlabel(w1/pi);ylabel(phi(omega1)/pi);title(相位特性);grid on;Xjw2=conj(x*(exp(-j

2、*(-pi)/100).(n*h);subplot(2,2,3);plot(w/pi,abs(Xjw2);grid on;xlabel(w2/pi);ylabel(|X(jw2)|);title(幅度特性);subplot(2,2,4);plot(w/pi,angle(Xjw2)/pi);xlabel(w2/pi);ylabel(phi(omega2)/pi);title(相位特性);grid on;可看出具有共轭对称性2.n=0:10;x=(0.9*exp(j*pi/3).n;k=-400:400;w=(pi/100)*k;Xjw=x*(exp(-j*pi/100).(n*k);subplo

3、t(2,1,1);plot(w/pi,abs(Xjw);grid on;xlabel(w/pi);ylabel(|X(jw)|);title(幅度特性);subplot(2,1,2);plot(w/pi,angle(Xjw)/pi);xlabel(w/pi);ylabel(phi(omega)/pi);title(相位特性);grid on;X（ejw）因变量w是以w=2*pi为最小正周期的3.由题得：H(Z)=1/(1-0.9Z(-1);b=1;a=1,-0.9;zplane(b,a);xlabel(实部);ylabel(虚部);title(零极点分布图); grid on;H,w=freq

4、z(b,a,100);o=abs(H);p=angle(H);figure;subplot(2,1,1);plot(w/pi,o);grid;xlabel(w/pi); ylabel(|H(ejomega)|);title(幅度特性);subplot(2,1,2);plot(w/pi,o/pi);grid;title(相位特性);xlabel(w/pi); ylabel(phi(omega);figure(3);b=1;a=1,-0.9;impz(b,a,50);xlabel(取样n);ylabel(幅度);title(单位脉冲响应); grid on;a.b.c.4.由题意知道其传递函数为：

5、H(jw)= 第a问：b=1,1;a=1,-0.9,0.81;H,w=freqz(b,a,256,whole);m=abs(H);p=angle(H)subplot(2,1,1);plot(w/pi,m);grid;xlabel(w/pi); ylabel(|H(ejomega)|);title(幅度特性);subplot(2,1,2);plot(w/pi,p/pi);grid on;title(相位特性);xlabel(w/pi); ylabel(phi(omega);第b问：它的差分方程为：y(n)-0.9*y(n-1)+0.81*y(n-2)= x(n-1)+1第C问：b=1,1;a=1

6、,-0.9,0.81;impz(b,a,60);xlabel(取样n);ylabel(幅度);title(单位脉冲响应);grid on;5.第a问：n=0:3;x=(ones(1,4);k=-400:400;w=(pi/100)*k;Xjw=x*(exp(-j*pi/100).(n*k);subplot(2,1,1);plot(w/pi,abs(Xjw);grid on;xlabel(w/pi);ylabel(|X(jw)|);title(幅度特性);subplot(2,1,2);plot(w/pi,angle(Xjw)/pi);xlabel(w/pi);ylabel(phi(omega)/

7、pi);title(相位特性);grid on;第b问： xn=ones(1,4); N=4; n=0:1:N-1; k=n; WN=exp(-j*2*pi/N); nk=n*k; WNnk=WN.nk; xk=xn* WNnk; xk=(xk)xk = 4.0000 -0.0000 + 0.0000i 0 + 0.0000i 0.0000 + 0.0000i6.x1=1,2,2,1;x2=1,-1,-1,1;x3=conv(x1,x2);subplot(2,1,1);n=0:length(x3)-1;stem(n,x3);xlabel(n);ylabel(X3);title(线卷积图像);g

8、rid on;y1=x1,zeros(1,3);y2=x2,zeros(1,3);x4=ifft(fft(y1).*fft(y2);subplot(2,1,2);stem(n,x4);xlabel(n);ylabel(X4);title(圆卷积图像); grid on;x1,x2做圆卷积时，两个序列的长度一样，并且大于或等于4+4-1=7；圆卷积和线卷积的结果是一样的。第三次大作业1.a=-4 1 -1 -2 5 6 5 -2 -1 1 -4;b=length(a);L=(b-1)/2;d=2*a(L+1:-1:1);n=0:1:L;w=0:1:1000.*pi/500;Hr=cos(w*n)

9、*d.;subplot(2,1,1);plot(w/pi,Hr);xlabel(频率 /);ylabel(Hr);title(振幅响应);grid on;subplot(2,1,2);zplane(h,1); title(零极点);grid on;2.wp=0.2*pi;ws=0.3*pi;tr_width=ws-wp;g=ceil(6.6*pi/tr_width);n=0:1:g-1;wc=(ws+wp)/2;a=(g-1)/2;n=0:1:(g-1);m=n-a+eps;hd=sin(wc*m)./(pi*m);w_ham=(hamming(g);h=hd.*w_ham;H,w=freqz

10、(h,1,1000,whole); H=(H(1:1:501);w=(w(1:1:501)mag=abs(H);db=20*log10(mag+eps)/max(mag);pha=angle(H);grd=grpdelay(h,1,w);delta_w=2*pi/1000;Rp=-(min(db(1:1:wp/delta_w+1);As=-round(max(db(ws/delta_w+1:1:501);subplot(2,2,1);stem(n,hd);title(Ideal Impluse Response) ;grid on;axis(0 g-1 -0.1 0.3);ylabel(hd(

11、n)subplot(2,2,2);stem(n,w_ham);title(Hamming Window) ;grid on;axis(0 g-1 0 1.1);ylabel(w(n)subplot(2,2,3);stem(n,h);title(Actual Impluse Response) ;grid on;axis(0 g-1 -0.1 0.3);ylabel(h(n)subplot(2,2,4);plot(w/pi,db);title(Magtitude Response in db) ;grid on;axis(0 1 -200 10);ylabel(Decibels)3.%可以用脉冲

12、响应不变法设计滤波器如下：wp=0.2*pi; ws=0.3*pi; Rp=7; Rs=16;Ts=0.01; Nn=128; Wp=wp/Ts; Ws=ws/Ts;N,Wn=buttord(Wp,Ws,Rp,Rs,s);z,p,k=buttap(N); Bp,Ap=zp2tf(z,p,k); b,a=lp2lp(Bp,Ap,Wn);bz,az=impinvar(b,a,1/Ts); freqz(bz,az,Nn,1/Ts);4.wp=0.2*pi;ws=0.3*pi;Rp=1;As=16;T=1; Rip=10(-Rp/20);Atn=10(-As/20);OmegaP=wp*T;Omega

13、S=ws*T;n,Wn=cheb1ord(OmegaP,OmegaS,1,15,s); b,a=cheby1(n,1,Wn,low,s); freqs(b,a); bz,az=impinvar(b,a,T); H,W=freqz(bz,az,512,T); ma=20*log10(abs(H),pha=20*log10(unwrap(angle(H),hi=impz(bz,az);ni=step(bz,az);subplot(2,2,1),plot(W,ma);title(幅频特性(dB); ;grid on;xlabel(w(/);ylabel(dB);subplot(2,2,2),plot(W,pha);title(相频特性); ;grid on;xlabel(w(/);ylabel(pha(/);subplot(2,2,3),plot(hi);title(单位冲击响应); ;grid on;xlabel(n);ylabel(h(n);subplot(2,2,4),plot(ni); title(单位阶越响应); ;grid on;xlabel(n);ylabel(h(n);