function h=rayli(fm,fs,N)
% clear;
% clc;
% fm=100;
% fs=23040;
% % f2=23040;
% N=100000;
if fm == 0
    h=ones(1,N);
else
deltaf=fs/N;
Nmax=ceil(fm/deltaf);
noisex=randn(1,N);
noisey=randn(1,N);
Fx=fft(noisex);
Fy=fft(noisey);

basex=[Fx(1:Nmax) zeros(1,N-2*Nmax) Fx(N-Nmax+1:N)];
basey=[Fy(1:Nmax) zeros(1,N-2*Nmax) Fy(N-Nmax+1:N)];
hx=real(ifft(basex));
hy=real(ifft(basey));
hx = hx-mean(hx);
hy = hy-mean(hy);
h=sqrt(hx.^2+hy.^2);
power=mean(h.^2);
h=(hx+j*hy)/sqrt(power); figure;plot(abs(h))
end