实验二用FFT做谱分析.

n1=0:3;x1=[1,1,1,1];

subplot(221;stem(n1,x1;title('x1序列';

k1=0:7;y11=fft(x1,8;magy11=abs(y11;

subplot(222;stem(k1,magy11;title('x1的8点FFT'; k2=0:15;y12=fft(x1,16;magy12=abs(y12;

subplot(224;stem(k2,magy12;title('x1的16点FFT';

n1=0:7;x2=[1,2,3,4,4,3,2,1];

subplot(221;stem(n1,x2;title('x2序列';

k1=0:7;y21=fft(x2,8;magy21=abs(y21;

subplot(222;stem(k1,magy21;title('x2的8点FFT'; k2=0:15;y22=fft(x2,16;magy22=abs(y22;

subplot(224;stem(k2,magy22;title('x2的16点FFT';

n1=0:7;x3=[4,3,2,1,1,2,3,4];

subplot(221;stem(n1,x3;title('x3序列';

k1=0:7;y31=fft(x3,8;magy31=abs(y31;

subplot(222;stem(k1,magy31;title('x3的8点FFT'; k2=0:15;y32=fft(x3,16;magy32=abs(y32;

subplot(224;stem(k2,magy32;title('x3的16点FFT';

n1=0:15;x4=cos((pi/4*n1;

subplot(221;stem(n1,x4;title('x4序列';

k1=0:7;y41=fft(x4,8;magy41=abs(y41;

subplot(222;stem(k1,magy41;title('x4的8点FFT'; k2=0:15;y42=fft(x4,16;magy42=abs(y42;

subplot(224;stem(k2,magy42;title('x4的16点FFT';

n1=0:15;x5=sin((pi/8*n1;

subplot(221;stem(n1,x5;title('x5序列';

k1=0:7;y51=fft(x5,8;magy51=abs(y51;

subplot(222;stem(k1,magy51;title('x5的8点FFT';

k2=0:15;y52=fft(x5,16;magy52=abs(y52;

subplot(224;stem(k2,magy52;title('x5的16点FFT';

n1=0:0.03125:0.5;x6=cos(8*pi*n1+cos(16*pi*n1+cos(20*pi*n1; subplot(221;plot(x6;title('x6函数';

n2=0:0.0625:0.5;x6=cos(8*pi*n2+cos(16*pi*n2+cos(20*pi*n2; k1=0:7;y61=fft(x6,8;magy61=abs(y61;

subplot(222;stem(k1,magy61;title('x6的8点FFT';

k2=0:15;y62=fft(x6,16;magy62=abs(y62;

subplot(224;stem(k2,magy62;title('x6的16点FFT';

n4=0:15;x4=cos((pi/4*n4;

n5=0:15;x5=sin((pi/8*n5;

n7=0:15;x7=x4+x5;

subplot(221;stem(n7,x7;title('x7的16点序列';

k7=n7;y7=fft(x7,16;magy7=abs(y7;

subplot(222;stem(k7,magy7;title('x7的16点FFT'; X4=real(y7;X5=imag(y7*i;

subplot(223;stem(k7,abs(X4;title('x4的16点FFT'; subplot(224;stem(k7,abs(X5;title('x5的16点FFT';

n4=0:15;x4=cos((pi/4*n4;

n5=0:15;x5=sin((pi/8*n5;

n8=0:15;x8=x4+x5*i;

subplot(221;stem(n8,abs(x8;title('x8的16点序列'; k8=n8;y8=fft(x8,16;magy8=abs(y8;

subplot(222;stem(k8,magy8;title('x8的16点FFT'; tempk=mod((16-k8,16;tempy8=y8(tempk+1; convy8=real(tempy8-imag(tempy8*i;

X4=0.5*(y8+convy8;

subplot(223;stem(k8,abs(X4;title('x4的16点FFT'; X5=1/(2*i*(y8-convy8;

subplot(224;stem(k8,abs(X5;title('x5的16点FFT';