matched_filter.m

包含FIR IIR窗函数法

function[y]=matched_filter(nt,taup,f0,b,rmin,rrec,tr,trcs,winid)
eps=1.0e-16;
htau=taup/2;
c=3.e8;
n=fix(2.*taup*b);
m=power_integer_2(n);
nfft=2.^m;
x(nt,1:nfft)=0.;
y(1:nfft)=0.;
y1(1:nfft)=0.;
if(winid==0.)
    win(1,nfft)=1.;
    win=win';
else
    if(winid==2.)
        win=kaiser(nfft,pi);
    else
       if(winid==3.)
        win=chebwin(nfft,60);
    end
end
end
end
deltar=c/2./b;
max_rrec=deltar*nfft/2.;
maxr=(max(tr)-rmin)*10^3;
if(rrec>max_rrec|maxr>=rrec)
    'Error.Receive window is too large;or scatterers fall outside window'
    break
end
trec=2.*rrec/c;
deltat=taup/nfft;
t=0:deltat:taup-eps;
uplimit=max(size(t));
replica(1:uplimit)=exp(i*2.*pi*(.5*(b/taup).*t.^2));
figure(3)
subplot(2,1,1)
plot(real(replica))
title('Matched filter time domain response')
subplot(212)
plot(fftshift(abs(fft(replica))));
title('Matched filter frequency domain response')
for j=1:nt
    t_tgt=2.*(tr(j)-rmin)*10^3/c+htau;
    x(j,1:uplimit)=trcs(j).*exp(i*2.*pi*(.5*(b/taup).*(t+t_tgt).^2));
     x1(j,1:uplimit)=trcs(j).*exp(i*2.*pi*(f0*(t+t_tgt)+(.5*(b/taup).*(t+t_tgt).^2)));
    y=y+x(j,:);
    y1=y1+x1(j,:);
end
figure(1)
plot(t,real(y),'k')
figure(5)
plot(t,real(y1),'k')

xlabel('Relative delay-seconds')
ylabel('Uncompressed echo')
title('Zero delay coincide with minimum rage')
rfft=fft(replica,nfft);
yfft=fft(y,nfft);
out=abs(ifft((rfft.*conj(yfft)).*win')).*(nfft);
figure(2)
time=-htau:deltat:htau-eps;
plot(time,out,'k')
xlabel('relative delau-seconds')
ylabel('Compressed echo')
title('Zero delay coincide with minimun range')
grid on


function n=power_integer_2(x)
m=0.;
for j=1:30
    m=m+1.;
    delta=x-2.^m;
    if(delta<0.)
        n=m;
        return
    else
    end
end