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fc=3000; 
% fk=zeros(1,length(fc)); 
% for i=1:length(fc)     
    fi=16e3; 
    fr=fc+fi; 
fs=(1.28e6)*4; 
t=1/(100*fs):1/fs:513/fs; 
re=cos(2*pi*fr*t); 
ev=(15e3:21e3); 
fv1=min(ev); 
fv2=max(ev); 
tell=50; 
 A0=1; 
 W0=1; 
 sita=2*pi*fv1/fs; 
 N=513; 
 M=(fv2-fv1)/tell+1; 
 L=1024; 
 fai=2*pi*(fv2-fv1)/(fs*(M-1)); 
 A=A0*exp(j*sita); 
 W=W0*exp(-j*fai); 
% h=zeros(1,1024); 
%  for n=1:L 
%     if n<=M 
%     h(n)=W^(-(n-1)^2/2); 
%     else 
%     h(n)=W^(-(n-L-1)^2/2); 
%     end 
% end 
%  
% for s=1:N 
%     y1(s)=re(s)*(A^(-s+1))*(W^((s-1)^2/2)); 
% end 
% y=[y1,zeros(1,L-N)]; 
% H=fft(h,L); 
% Y=fft(y,L); 
% V=H.*Y; 
% v=ifft(V,L); 
%  k=0:L-1; 
% out=W.^(k.^2/2).*v; 
% out=out(1:M); 
% %out=fft(re,65536); 
% p=out.*conj(out); 
% [c,m]=max(p); 
% % fe = (m-1)/(65536*fs)- fi 
% % fk=(sita+fai*(m))/(fs*2*pi)-fi 
% % fe = (m-1)/(65536*fs)- fi 
% % fk(r)=(sita+fai*(m-1))/(fs*2*pi)-fi; 
% % fe = (m-1)/(65536*fs)- fi 
n = (0:M-1); 
hl = W .^ (-n .^ 2 ./ 2); 
n = (L-N+1:L-1); 
hltmp = W .^ (-(n-L) .^ 2 ./2); 
hl = [hl,zeros(1,L-N-M+1),hltmp]; 
 
n = (0:N-1); 
y = re .* A .^(-n) .* W .^(n.^2/2); 
y = [y,zeros(1,L-N)]; 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
%¼ÆËãX(k) 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
H = fft(hl); 
Y = fft(y); 
V = H .* Y; 
v = ifft(V); 
n = (0:L-1); 
Xtmp = W .^ (n.^2/2) .* v; 
X = Xtmp(1:M); 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
Pyy = X.* conj(X) / L; 
[c,m] = max(Pyy); 
% fe = (sita + (m-1)*fai)*fs / (2*pi) 
 
fk=(sita+fai*(m-1))*fs/(2*pi)-fi 
% end 
% plot(fc,fk,'b:p') 
% title('the performance of czt') 
% xlabel('frequency offset (Hz)'); 
% ylabel('czt output (Hz)');