function [ afg, afG,wafg, afpeak ] = calculate_apparent_freuqency( y, fc, fb ,filtersize)
%calculate the apparent frequency of the input signal
% y is input signal, fc is center frequency to down conver, fb is frequency
% bandwith

fso1=exp(-1j*2*pi*fc*(0:size(y,1)-1)'/1e6);
fso=repmat(fso1,[1,size(y,2)]);
y2=gfilter(y.*fso,1e6,0,fb);
y3=G_filter(y.*fso,1e6,0,fb);
afg=((real(y2).*[diff(imag(y2));ones([1,size(y,2)])])-(imag(y2).*[diff(real(y2));ones([1,size(y,2)])]))./(2*pi*0.000001*(abs(y2).^2));
afG=((real(y3).*[diff(imag(y3));ones([1,size(y,2)])])-(imag(y3).*[diff(real(y3));ones([1,size(y,2)])]))./(2*pi*0.000001*(abs(y3).^2));
afg(end)=afg(end-1);
afG(end)=afG(end-1);
% id=abs(y2)<mean(abs(y2));
% wafg=afg;
% wafg(id,:)=wafg(id,:).*abs(y2(id,:))/mean(abs(y2));
[ wafg ] = weightedfilter( abs(y2), afg, filtersize );
afpeak=wafg(abs(y2)==max(abs(y2)));
end