clear all;t=0:0.1:50;yp=sin(2*pi*2*t);yq=sin(2*pi*2.0125*t);y=yp+yq; Y1=fft(y,512);Y2=fft(y,4096);Y1=fftshift(Y1);Y2=fftshift(Y2);c1=[0:255]/51.2;c2=[0:2047]/409;subplot(2,1,1);plot(c1,abs(Y1(257:512)));axis([1.2,2.2,-30,300]);title('512点FFT的频
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![clear all;t=0:0.1:50;yp=sin(2*pi*2*t);yq=sin(2*pi*2.0125*t);y=yp+yq; Y1=fft(y,512);Y2=fft(y,4096);Y1=fftshift(Y1);Y2=fftshift(Y2);c1=[0:255]/51.2;c2=[0:2047]/409;subplot(2,1,1);plot(c1,abs(Y1(257:512)));axis([1.2,2.2,-30,300]);title('512点FFT的频](/uploads/image/z/3848144-32-4.jpg?t=clear+all%3Bt%3D0%3A0.1%3A50%3Byp%3Dsin%282%2Api%2A2%2At%29%3Byq%3Dsin%282%2Api%2A2.0125%2At%29%3By%3Dyp%2Byq%3B+Y1%3Dfft%28y%2C512%29%3BY2%3Dfft%28y%2C4096%29%3BY1%3Dfftshift%28Y1%29%3BY2%3Dfftshift%28Y2%29%3Bc1%3D%5B0%3A255%5D%2F51.2%3Bc2%3D%5B0%3A2047%5D%2F409%3Bsubplot%282%2C1%2C1%29%3Bplot%28c1%2Cabs%28Y1%28257%3A512%29%29%29%3Baxis%28%5B1.2%2C2.2%2C-30%2C300%5D%29%3Btitle%28%27512%E7%82%B9FFT%E7%9A%84%E9%A2%91)
clear all;t=0:0.1:50;yp=sin(2*pi*2*t);yq=sin(2*pi*2.0125*t);y=yp+yq; Y1=fft(y,512);Y2=fft(y,4096);Y1=fftshift(Y1);Y2=fftshift(Y2);c1=[0:255]/51.2;c2=[0:2047]/409;subplot(2,1,1);plot(c1,abs(Y1(257:512)));axis([1.2,2.2,-30,300]);title('512点FFT的频
clear all;
t=0:0.1:50;
yp=sin(2*pi*2*t);
yq=sin(2*pi*2.0125*t);
y=yp+yq;
Y1=fft(y,512);
Y2=fft(y,4096);
Y1=fftshift(Y1);
Y2=fftshift(Y2);
c1=[0:255]/51.2;
c2=[0:2047]/409;
subplot(2,1,1);plot(c1,abs(Y1(257:512)));
axis([1.2,2.2,-30,300]);
title('512点FFT的频谱');
grid on;
subplot(2,1,2);plot(c2,abs(Y2(2049:4096)));
axis([1.2,2.2,-30,300]);
title('4096点FFT的频谱');
grid on;
clear all;t=0:0.1:50;yp=sin(2*pi*2*t);yq=sin(2*pi*2.0125*t);y=yp+yq; Y1=fft(y,512);Y2=fft(y,4096);Y1=fftshift(Y1);Y2=fftshift(Y2);c1=[0:255]/51.2;c2=[0:2047]/409;subplot(2,1,1);plot(c1,abs(Y1(257:512)));axis([1.2,2.2,-30,300]);title('512点FFT的频
只是个MATLAB的程序吧.
t=0:0.1:50;t取值 0-50 间隔是0.1
yp=sin(2*pi*2*t); 三角函数 SIN(2π2t)
yq=sin(2*pi*2.0125*t);同上
y=yp+yq; 相加 也就是在yp的图形上加上yq的图形合成
Y1=fft(y,512);用FFT函数进行频谱分析
Y2=fft(y,4096);同上
Y1=fftshift(Y1);让正半轴部分和负半轴部分的图像分别关于各自的中心对称,将fft计算输出的零频移到输出的中心位置
Y2=fftshift(Y2);同上
c1=[0:255]/51.2;C1分别取值除51.2
c2=[0:2047]/409;
subplot(2,1,1);plot(c1,abs(Y1(257:512)));画图函数subplot(2,1,1)表示画2个图 此为第一个
axis([1.2,2.2,-30,300]);横纵坐标起始和结束位置(此为纵坐标1.2-2.2,横坐标-30到300)
title('512点FFT的频谱');给上图命名
grid on;
subplot(2,1,2);plot(c2,abs(Y2(2049:4096)));同上
axis([1.2,2.2,-30,300]);
title('4096点FFT的频谱');
grid on;