matlab实验

1、在[-pi pi]画出序列x=[2 4 6 8 10 12 14 16

18DTFT幅度，相位特性；

>> w=-pi:2*pi/255:pi;

>> x=[2 4 6 8 10 12 14 16 18];

>> den=[1 -0.6];

>> h=freqz(x,den,w);

>>subplot(2,2,1);

>> plot(w,real(h));

>>subplot(2,2,2);

>> plot(w,imag(h));

>>subplot(2,2,3);

>> plot(w,abs(h));

>>subplot(2,2,4);

>> plot(w,angle(h));

2 画x(n-10)的DTFT幅度、相位特性

> >w=-pi:2*pi/255:pi;

>> x=[2 4 6 8 10 12 14 16 18];

>> h1=freqz(x,1,w);

>> h2=freqz([zeros(1,10) x],1,w);

>> plot(w,real(h2));

>> plot(w,imag(h2));

>> plot(w,abs(h2));

>> plot(w,angle(h2));

3 画exp(0.2pi*n)x(n)的DTFT幅度、相位特性>> w=-pi:2*pi/255:pi;w0=0.2*pi;

>> num1=[2 4 6 8 10 12 14 16 18];

>> l=length(num1);

>> h1=freqz(num1,1,w);

>> n=0:l-1;

>> num2=exp(w0*i*n).*num1;

>> h2=freqz(num2,1,w);

>> subplot(2,2,1)

>> plot(w,abs(h1))

>> title('origin serials a-w curve')

>> subplot(2,2,2)

>> plot(w,abs(h2))

>> title('f-shift a-w curve')

>> subplot(2,2,3)

>> plot(w,angle(h1))

>> title('origin serials angle-w curve')

>> subplot(2,2,4)

>> plot(w,angle(h2))

>> title('f-shift angle-w curve')

4 序列x1=[1 2 3 4 3 2 1]求x与x1卷积的DTFT并画图

>> w=-pi:2*pi/255:pi;

>> x1=[12 3 4 3 2 1];

>> x=[2 4 6 8 10 12 14 16 18];

>> y=conv(x,x1);

>> h1=freqz(x,1,w);

>> h2=freqz(x1,1,w);

>> hp=h1.*h2;

>> h3=freqz(y,1,w);

>> subplot(2,2,1)

>> plot(w,abs(hp))

>> title('幅度乘积')

>> subplot(2,2,2)

>> plot(w,abs(h3))

>> title('卷积序列的幅度')

>> subplot(2,2,3)

>> plot(w,angle(hp))

>> title('相位譜的和')

>> subplot(2,2,4)

>> plot(w,angle(h3))

>> title('卷积序列的相位谱')

5 求x与x1乘积的DTFT并画图

>> w=-pi:2*pi/255:pi;

>> x=[2 4 6 8 10 12 14 16 18];

>> x1=[1 2 3 4 3 2 1];

>> h1=freqz(x,1,w);

>> h2=freqz(x1,1,w);

>> h=h1.*h2;

>> h3=freqz(h,1,w);

>> subplot(2,1,1);

>> plot(w,abs(h3));

>> title('幅度特性')

>> subplot(2,1,2);

>> plot(w,angle(h3));

>> title('相角特性')

6已知X1(z)=2+3z^(-1)+4z^(-2),X2(z)=3+4z^(-1)+5z^(-2)+6z^(-3),求下X3(z)=X1(z)X2(z) >>x1=[2 3 4];

>>x2=[3 4 5 6];

>>y=conv(x1,x2);

>>y=

6 1

7 34 43 3

8 24

X3(z)=6+17z^(-1)+34z^(-2)+43z^(-3)+38z^(-4)+24z^(-5)

1、

x=[1 1 1 1 1];

>> y=fft(x,101);

>> y1=fft(x,1024);

>> subplot(2,1,1)

>> stem(y)

>> subplot(2,1,2)

>> stem(y1)

2、

x1=[1 3 5 7 9];x2=[2 2 0 1 1];

y=circonv(x1,x2);

h1=fft(x1);h2=fft(x2);

h3=fft(y);

hp=h1.*h2;

subplot(2,2,1);stem(x1);

subplot(2,2,2)

subplot(2,2,3)

stem(abs(h3))

title('序列卷积的DFT的幅度') subplot(2,2,4)

stem(abs(hp))

title('序列DFT的乘积的幅度')

3、

x1=[1 3 5 7 9];x2=[2 2 0 1 1];

x1e=[x1 zeros(1,length(x2)-1)];

x2e=[x2 zeros(1,length(x1)-1)];

y=conv(x1,x2);

ye=circonv(x1e,x2e);

subplot(4,1,1)

stem(x1e);