北邮DSP matlab实验.docx
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北邮DSPmatlab实验
1.单位抽样序列
n=-10:
10;
y=[zeros(1,10),1,zeros(1,10)];
stem(n,y)
axis([-10,10,0,2]);
2.单位阶跃序列
n=-10:
10;
y=[zeros(1,10),ones(1,11)];
stem(n,y)
axis([-10,10,0,2]);
3.正弦序列
n=0:
60;
A=5;f=200;Fs=5000;fai=pi/3;
y=A*sin(2*pi*f*n/Fs+fai);
stem(n,y)
axis([0,60,-5,5]);
4.复正弦序列
n=0:
20;
w=pi/10;
x=exp(j*n*w);
subplot(3,2,1);stem(n,x);title('x');xlabel('n');
subplot(3,2,2);stem(n,real(x));title('实部');xlabel('n');
subplot(3,2,3);stem(n,imag(x));title('虚部');xlabel('n');
subplot(3,2,4);stem(n,abs(x));title('振幅');xlabel('n');
subplot(3,2,5);stem(n,(180/pi)*angle(x));title('相位');xlabel('n');
5.指数序列
n=0:
10;
y=1.5.^n;
stem(n,y)
6.复指数序列
n=-10:
1:
10;
alpha=-0.1+0.3j;
x=exp(alpha*n);
subplot(2,2,1);stem(n,real(x));title('实部');xlabel('n');
subplot(2,2,2);stem(n,imag(x));title('虚部');xlabel('n');
subplot(2,2,3);stem(n,abs(x));title('振幅');xlabel('n');
subplot(2,2,4);stem(n,(180/pi)*angle(x));title('相位');xlabel('n');
二、
1.h(n)
n=-20:
20;
>>stem(n,y);
>>a=[1,0.75,0.125];b=[1,-1];
x=[zeros(1,20),1,zeros(1,20)];
n=-20:
20;
y=filter(b,a,x);
stem(n,y);
理论计算:
h(n)=6*(-0.5).^n-5*(-0.25).^n;
当n取0,1,2,....,10时,h(n)计算结果如下:
1.0000
-1.7500
1.1875
-0.6719
0.3555
-0.1826
0.0925
-0.0466
0.0234
-0.0117
0.0059
与matlab程序画的单位冲击响应的图形一致。
g(n)
x2=[zeros(1,20),ones(1,21)];
y2=filter(b,a,x2);
stem(n,y2);
理论计算:
g(n)=4*(1-(-0.5).^(n+1))-4*(1-(-0.25).^(n+1));
当n取0,1,2,....,10时,h(n)计算结果如下:
1.0000
-0.7500
0.4375
-0.2344
0.1211
-0.0615
0.0310
-0.0156
0.0078
-0.0039
0.0020
与matlab程序画的单位阶跃响应的图形一致。
2.
h(n)
>>b=[0,1,1,1,1];
>>a=4;
>>x=[zeros(1,20),1,zeros(1,20)];
>>n=-20:
20;
>>y=filter(b,a,x);
>>stem(n,y)
理论计算:
h(n)=0.25(delta(n-1)+delta(n-2)+delta(n-3)+delta(n-4))
与程序计算结果相符
g(n)
x2=[zeros(1,20),ones(1,21)];
y2=filter(b,a,x2);
stem(n,y2);
理论计算:
g(n)=0.25(u(n-1)+u(n-2)+u(n-3)+u(n-4))
与程序计算结果一致。
三、
>>b=[0.0528,0.0797,0.1295,0.797,0.0528];
>>a=[1,-1.8107,2.4947,-1.8801,0.9537,-0.2336];
>>zplane(b,a)
零极点图
[H,w]=freqz(b,a,100,'whole');
plot(w,abs(H))
axis([0,2*pi,0,14]);
xlabel('w');ylabel('|H|');
幅度频率响应特线