%
%恒虛警(CFAR)
%

function [cfar,cfar1,cfarn]=cfar(y,N)
N1=N+5;
y=log2(y);
for i=1:length(y)-N1+1
    y1=y(i:i+N1-1);
sum2=sum(y1(1:N/2))*2/N;
sum3=sum(y1((N1-N/2+1):N1))*2/N;
cmp1=max([sum2,sum3]);
sel1=y1(N/2+3)-(cmp1*sqrt(pi/2)*0.2);
cmp(i)=cmp1;
sel(i)=sel1;
if 2.^sel1>=4.29   %0.0001
    cfar1(i)=1;
else 
    cfar1(i)=0;
end
cfarn(i)=i+N/2+2;
end
cfar=2.^sel;