西电数字信号处理上机实验.docx
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西电数字信号处理上机实验.docx
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西电数字信号处理上机实验
实验一
1-1、a=[-201-13];
b=[120-1];
c=conv(a,b);
M=length(c)-1;
n=0:
1:
M;
stem(n,c);
xlabel('n');
ylabel('幅度');
title('离散卷积’);
1-2、N=41;
a=[0.8-0.440.360.22];
b=[10.7-0.45-0.6];
x=[1zeros(1,N-1)];
k=0:
1:
N-1;
y=filter(a,b,x);
stem(k,y)
xlabel('n');ylabel('幅度');
title('差分方程');
1-3、k=256;
num=[0.8-0.440.360.02];
den=[10.7-0.45-0.6];
w=0:
pi/k:
pi;
h=freqz(num,den,w);
subplot(2,2,1);
plot(w/pi,real(h));grid
title('实部');
xlabel('\omega/\pi');ylabel('幅度');
subplot(2,2,2);
plot(w/pi,imag(h));grid
title('虚部');
xlabel('\omega/\pi');ylabel('Amplitude');
subplot(2,2,3);
plot(w/pi,abs(h));grid
title('幅度谱');
xlabel('\omega/\pi');ylabel('幅值');
subplot(2,2,4);
plot(w/pi,angle(h));grid
title('相位谱');
xlabel('\omega/\pi');ylabel('弧度');
实验二
2-1、
N=16;
n=0:
1:
15;
p=8;
q=4;
a=0.1;
f=0.0625;
xa=exp(-((n-p).^2)./q);
figure
(1)
stem(n,xa,'.');
title('xa(n)序列')
xlabel('n')
ylabel('xa(n)')
gridon
[H,w]=freqz(xa,1,[],'whole',1);
Hamplitude=abs(H);
Hphase=angle(H);
Hphase=unwrap(Hphase);
figure
(2)
subplot(2,1,1)
plot(w,Hamplitude)
title('幅频响应')
xlabel('w/(2*pi)')
ylabel('|H(exp(jw))|')
gridon
subplot(2,1,2)
plot(w,Hphase)
title('相频响应')
xlabel('w/(2*pi)')
ylabel('fai(H(exp(jw)))')
gridon
2-2、
n=0:
1:
15;
a=0.1;
f1=0.0625;f2=0.04375;f3=0.05625;
xb1=exp(-a*n).*sin(2*pi*f1*n);
figure
subplot(3,2,1)
stem(n,xb1,'.');
title('f=0.0625的时域特性')
xlabel('n')
ylabel('xb1(n)')
gridon
[H,w]=freqz(xb1,1,[],'whole',1);
Hamplitude=abs(H);
subplot(3,2,2)
plot(w,Hamplitude)
title('f=0.0625的幅频响应')
xlabel('w/(2*pi)')
ylabel('|H(exp(jw))|')
gridon
xb2=exp(-a*n).*sin(2*pi*f2*n);
subplot(3,2,3)
stem(n,xb2,'.');
title('f=0.04375的时域特性')
xlabel('n')
ylabel('xb2(n)')
gridon
[H,w]=freqz(xb2,1,[],'whole',1);
Hamplitude=abs(H);
subplot(3,2,4)
plot(w,Hamplitude)
title('f=0.04375的幅频响应')
xlabel('w/(2*pi)')
ylabel('|H(exp(jw))|')
gridon
xb3=exp(-a*n).*sin(2*pi*f3*n);
subplot(3,2,5)
stem(n,xb3,'.');
title('f=0.05625的时域特性')
xlabel('n')
ylabel('xb3(n)')
gridon
[H,w]=freqz(xb3,1,[],'whole',1);
Hamplitude=abs(H);
subplot(3,2,6)
plot(w,Hamplitude)
title('f=0.05625的幅频响应')
xlabel('w/(2*pi)')
ylabel('|H(exp(jw))|')
gridon
2-3、
n1=0:
1:
3;
xc1=n1+1;
n2=4:
7;
xc2=8-n2;
xc=[xc1,xc2];
n=[n1,n2];
figure
stem(n,xc);
xlabel('n');
ylabel('xc');
title('三角序列');
n1=0:
1:
3;
xd1=4-n1;
n2=4:
7;
xd2=n2-3;
xd=[xd1,xd2];
n=[n1,n2];
figure
stem(n,xd);
xlabel('n');
ylabel('xd');
title('反三角序列');
N=16;
[H1,w1]=freqz(xc,1,256,'whole',1);
Hamplitude1=abs(H1);
figure
plot(2*w1,Hamplitude1)
title('xc幅频响应')
xlabel('w/pi')
ylabel('|H(exp(jw))|')
gridon
[H2,w2]=freqz(xd,1,256,'whole',1);
Hamplitude2=abs(H2);
figure
plot(2*w2,Hamplitude2)
title('xd幅频响应')
xlabel('w/pi')
ylabel('|H(exp(jw))|')
gridon
[H3,w3]=freqz(xc,1,N,'whole',1);
Hamplitude3=abs(H3);
figure
subplot(2,1,1)
h3=stem(2*w3,Hamplitude3,'*');
title('xc幅频响应进行N点FFT’);
xlabel('n')
ylabel('|H(exp(jw))|')
gridon
[H4,w4]=freqz(xd,1,N,'whole',1);
Hamplitude4=abs(H4);
subplot(2,1,2)
h4=stem(2*w4,Hamplitude4,'*');
title('xd幅频响应进行N点FFT');
xlabel('n')
ylabel('|H(exp(jw))|')
gridon
2-4、
N=128;
f1=1/16;
n=0:
N-1;
xn=sin(2*pi*0.125.*n)+cos(2*pi*(0.125+f1).*n);
figure
stem(n,xn);
figure
subplot(2,1,1),plot(n,abs(fft(xn)));
title('f=1/16幅频响应');
f2=1/64;
xn=sin(2*pi*0.125.*n)+cos(2*pi*(0.125+f2).*n);
subplot(2,1,2),plot(n,abs(fft(xn)));
title('f=1/64幅频响应');
2-5、
N=16;
n=0:
1:
15;
p=8;
q=2;
a=0.1;
f=0.0625;
xa=exp(-((n-p).^2)./q);
xb=exp(-a*n).*sin(2*pi*f*n);
%线性卷积
x=conv(xa,xb);
XDft=fft(x,32);
XDftR=abs(XDft);
XDftPhase=angle(XDft);
XDftPhase=unwrap(XDftPhase);
figure
(1);
stem(x,'.');
title('x(n)序列');
xlabel('n')
ylabel('x(n)')
gridon
figure
(2)
subplot(2,1,1)
stem(XDftR,'.');
title('X(k)的幅度’);
xlabel('k')
ylabel('|X(k)|')
gridon
subplot(2,1,2)
stem(XDftPhase,'.');
title('X(k)的相角')
xlabel('k')
ylabel('fai((X(k)))')
gridon
%圆周卷积
XDft161=fft(xa,N);
XDft16R1=abs(XDft161);
XDft16Phase1=angle(XDft161);
XDft16Phase1=unwrap(XDft16Phase1);
XDft162=fft(xb,N);
XDft16R2=abs(XDft162);
XDft16Phase2=angle(XDft162);
XDft16Phase2=unwrap(XDft16Phase2);
XDft16=XDft161.*XDft162;
XDft16R=XDft16R1.*XDft16R2;
XDft16Phase=XDft16Phase2+XDft16Phase1;
x=ifft(XDft16,N);
figure(3)
stem(x,'.')
title('x(n)序列')
xlabel('n')
ylabel('x(n)')
gridon
figure(4)
subplot(2,1,1)
t=0:
1:
N-1;
stem(t,XDft16R,'.');
title('X(k)的幅度')
xlabel('k')
ylabel('|X(k)|')
gridon
subplot(2,1,2)
stem(t,XDft16Phase,'.');
title('X(k)的相角')
xlabel('k')
ylabel('fai((X(k)))')
gridon
2-6、
xe=rand(1,512);
n1=0:
1:
3;
xc1=n1+1;
n2=4:
7;
xc2=8-n2;
xc=[xc1,xc2];
%重叠相加法
yn=zeros(1,519);
forj=0:
7
xj=xe(64*j+1:
64*(j+1));
xak=fft(xj,71);
xck=fft(xc,71);
yn1=ifft(xak.*xck);
temp=zeros(1,519);
temp(64*j+1:
64*j+71)=yn1;
yn=yn+temp;
end;
n=0:
518;
figure
(1)
subplot(2,1,1);
plot(n,yn);
xlabel('n');ylabel('y(n)');
title('xc(n)与xe(n)的线性卷积的时域波形-重叠相加法');
subplot(2,1,2);
plot(n,abs(fft(yn)));
xlabel('k');ylabel('Y(k)');
axis([0,600,0,300]);
title('xc(n)Óëxe(n)的线性卷积的幅频特性-重叠相加法');
%重叠保留法
k=1:
7;
xe1=k-k;
xe_1=[xe1,xe];
yn_1=zeros(1,519);
forj=0:
7
xj_1=xe_1(64*j+1:
64*j+71);
xak_1=fft(xj_1);
xck_1=fft(xc,71);
yn1_1=ifft(xak_1.*xck_1);
temp_1=zeros(1,519);
temp_1(64*j+1:
64*j+64)=yn1_1(8:
71);
yn_1=yn_1+temp_1;
end;
n=0:
518;
figure
(2)
subplot(2,1,1);
plot(n,yn_1);
xlabel('n');ylabel('y(n)');
title('xc(n)的线性卷积的时域波形-重叠保留法');
subplot(2,1,2);
plot(n,abs(fft(yn_1)));
xlabel('k');ylabel('Y(k)');
axis([0,600,0,300]);
title('xc(n)Óëxe(n)的线性卷积的幅频特性-重叠保留法');
实验三
3-1、
Wp=0.3;Ws=0.2;Rp=0.8;Rs=20;
[N,Wpo]=cheb1ord(Wp,Ws,Rp,Rs);
[Bz,Az]=cheby1(N,Rp,Wpo,'high');
w=0:
0.1:
pi;
[H,w1]=freqz(Bz,Az,w);H=20*log10(abs(H));
plot(w/pi,H),gridon
xlabel('\omega/\pi');ylabel('|H(e^j^\omega)|/dB')
title('Chebyshev高通滤波器');
3-2、
Wp=0.2;Ws=0.3;Rp=1;Rs=25;
[N,Wc]=buttord(Wp,Ws,Rp,Rs);
[Bs,As]=butter(N,Wc,'s');
[Bz,Az]=impinvar(Bs,As);
w=0:
0.1:
pi;
[H,w1]=freqz(Bz,Az,w);H=20*log10(abs(H));
subplot(211);plot(w/pi,H),gridon
xlabel('\omega/\pi');ylabel('|H(e^j^\omega)|/dB')
title('脉冲响应不变法')
[N,Wc]=buttord(Wp,Ws,Rp,Rs);
[Bz,Az]=butter(N,Wc);
w=0:
0.1:
pi;
[H,w1]=freqz(Bz,Az,w);H=20*log10(abs(H));
subplot(212);plot(w/pi,H),gridon
xlabel('\omega/\pi');ylabel('|H(e^j^\omega)|/dB')
title('双线性变换法')
3-3、
Wp=1.2/8;Ws=2/8;Rp=0.5;Rs=40;
[N,Wpo]=cheb1ord(Wp,Ws,Rp,Rs);
[Bz,Az]=cheby1(N,Rp,Wpo);
w=0:
0.1:
pi;
[H,w1]=freqz(Bz,Az,w);H=20*log10(abs(H));
subplot(311);plot(w/pi,H),gridon
xlabel('\omega/\pi');ylabel('|H(e^j^\omega)|/dB')
title('切比雪夫')
[N,Wc]=buttord(Wp,Ws,Rp,Rs);
[Bz,Az]=butter(N,Wc);
w=0:
0.1:
pi;
[H,w1]=freqz(Bz,Az,w);H=20*log10(abs(H));
subplot(312);
plot(w/pi,H),gridon
xlabel('\omega/\pi');ylabel('|H(e^j^\omega)|/dB')
title('巴特沃斯')
[N,Wpo]=ellipord(Wp,Ws,Rp,Rs);
[Bz,Az]=ellip(N,Rp,Rs,Wpo);
w=0:
0.1:
pi;
[H,w1]=freqz(Bz,Az,w);H=20*log10(abs(H));
subplot(313);
plot(w/pi,H),gridon
title('椭圆')
xlabel('\omega/\pi');ylabel('|H(e^j^\omega)|/dB')
3-4、
Wp1=2/15;Wpu=0.2;Ws1=0.1;Wsu=0.4;Rp=3;Rs=20;
Wp=[Wp1,Wpu];Ws=[Ws1,Wsu];
[N,Wc]=buttord(Wp,Ws,Rp,Rs);
[Bz,Az]=butter(N,Wc);
w=0:
0.1:
pi;
[H,w1]=freqz(Bz,Az,w);H=20*log10(abs(H));
plot(w/pi,H),gridon
xlabel('\omega/\pi');ylabel('|H(e^j^\omega)|/dB')
title('双线性变换法Butterworth型数字带通滤波器')
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