sy61.m

1）已知2N点实数序列 N=64。用一个64点的复数FFT程序

N=64;
n=0:2*N-1;
k=0:N-1;
WN=exp(-j*2*pi/(2*N));
x=cos(2*pi*7*n/N)+1/2*cos(2*pi/N*19*n);
x0=cos(2*pi*7*(2*k)/N)+1/2*cos(2*pi/N*19*(2*k));
x1=cos(2*pi*7*(2*k+1)/N)+1/2*cos(2*pi/N*19*(2*k+1));
xk3=fft(x,128);
subplot(3,1,1);;
stem(abs(xk3));
x2=fft(x0,64);x3=fft(x1,64);
Xk0=x2+(WN.^k).*x3;
Xk1=x2-(WN.^k).*x3;
Xk=[Xk0,Xk1];
subplot(3,1,2);;
stem(abs(Xk))
n0=0:N-1;
k0=0:N-1;
xk=1./(1-0.8*WN.^k0);
xn=ifft(xk,N);
subplot(3,1,3);;
stem(abs(xn));