%計算信號FFT變換的幅值和相位值
N=256;
t=1:N;
Fs=1000;
x=sin(2*pi*t*100/Fs)+sin(2*pi*t*200/Fs)+sin(2*pi*t*400/Fs);
y=fft(x);
A=abs(y);
B=angle(y);
f=(0:length(y)/2-1)'/length(y)*Fs;
subplot(2,1,1),plot(f,A(1:N/2));
xlabel('Abs');
subplot(2,1,2),plot(f,B(1:N/2));
xlabel('Angle');