实验报告：用FFT对信号作频谱分析.doc

文档介绍：实验三:用FFT对信号作频谱分析
(1)程序如下:
x1n=[1 1 1 1];
x2n=[1 2 3 4 4 3 2 1];
x3n=[4 3 2 1 1 2 3 4];
X1=fft(x1n,8);
subplot(321);stem(abs(X1));
X11=fft(x1n,16);
subplot(322);stem(abs(X11));
X2=fft(x2n,8);
subplot(323);stem(abs(X2));
X22=fft(x2n,16);
subplot(324);stem(abs(X22));
X3=fft(x3n,8);
subplot(325);stem(abs(X3));
X33=fft(x3n,16);
subplot(326);stem(abs(X33));
(2)运行结果如下:
2、(1)程序如下:
n=0:7;
x4n=cos(pi*n/4);
x5n=cos(pi*n/4)+cos(pi*n/8);
X4=fft(x4n,8);
subplot(221);stem(abs(X4));
X5=fft(x5n,8);
subplot(223);stem(abs(X5));
n=0:15;
x4n=cos(pi*n/4);
x5n=cos(pi*n/4)+cos(pi*n/8);
X44=fft(x4n,16);
subplot(222);stem(abs(X44));
X55=fft(x5n,16);
subplot(224);stem(abs(X55));
运行结果如下:
3、(1)程序如下:
Fs=64;
T=1/Fs;
N=16;
n=0:N-1;
xnT=cos(8*pi*n*T)+cos(16*pi*n*T)+cos(20*pi*n*T);
X16=fft(xnT);
Tp=N*T;
F=1/Tp;
k=0:N-1;
f=k*F;