将一模拟信号采样后，用FFT估算模拟信号FT幅度频谱的matlab实现

t = 0:0.001:0.6;
x = sin(2*pi*50*t)+sin(2*pi*120*t);
y = x + 2*randn(size(t));
plot(1000*t(1:50),y(1:50))
title('Signal Corrupted with Zero-Mean Random Noise')
xlabel('time (milliseconds)')

Y = fft(y,512);

Pyy = Y.* conj(Y) / 512;

f = 1000*(0:256)/512;
plot(f,Pyy(1:257))
title('Frequency content of y')
xlabel('frequency (Hz)')

楼上的还注意幅值了？做了一点修改

t = 0:0.001:0.6;
x = 3*sin(2*pi*50*t)+4*sin(2*pi*120*t);
y = x + 2*randn(size(t));
subplot(211)
plot(1000*t(1:50),y(1:50))
title('Signal Corrupted with Zero-Mean Random Noise')
xlabel('time (milliseconds)')

Y = fft(y,512);

Pyy=abs(Y)*2/601;

f = 1000*(0:256)/512;
subplot(212)
plot(f,Pyy(1:257))
title('Frequency content of y')
xlabel('frequency (Hz)')