脈沖雷達(dá)初相識(三）

% This function implements the matched filter processor%% Inputs    % tau          == uncompressed pulse width in seconds    % b            == chirp bandwidth in Hz    % range        == scatterers?relative range in m    % rcs          == vector of scatterers?RCS in meter squared% Output    % y             == normalized compressed output%clcclose allclear alltau = 1e-6;b = 50e6;fs =5*b; rcs = 1;range = 150;nnoise = 0.05;n = ceil(tau*fs); %Number of sample points of chirp signalc = 3e8;ts = 1/fs;t = 0:ts:ts*(n-1);
% Transmitted LFM Chirp pulse:x =  exp(i * pi * (b/tau) .* t.^2);replica = exp(i * pi * (b/tau) .* t.^2);
ntarget = size(range,2);time_delay = 2*range/c;y = zeros(ntarget,ceil(max(time_delay/ts))+n-1);for k = 1:ntarget    y(k,ceil(time_delay(k)/ts):ceil(time_delay(k)/ts)+n-1) = x*rcs(k);endycomp = ones(1,ntarget)*y;ycomp =ycomp +nnoise*randn(1,size(ycomp,2));
tsamp = 0:ts:ts*ceil((length(ycomp)-1));


nfft =size(ycomp,2)H =  (conj(fft(replica,nfft)));h = (b*tau/n)*ifft(H.*fft(ycomp));filter_out = h;tout = 0.0:ts:ts*(length(filter_out)-1);% subplot(2,2,4); % plot(tout*1e6,20*log10( filter_out+0.0004));% title('\bf Output of Matched Filter');% xlabel('\bf Time \mu s');% grid% ylabel ('\bf Pulse compression gain in dB')
delr = (tout)*c/2;figuresubplot(2,1,1)filter_out = filter_out./max(filter_out);plot(70*tout*1e6,20*log10( filter_out+0.0004),'linewidth',1.5);title('\bf Output of Matched Filter');xlabel('\bf Time \mu s');gridylabel ('\bf Output vs. time')title({['\bf Targets range 10.5 km', '; delay = 70 \mu sec']})
% determine Hamming window
H =  conj(fft(replica,nfft));h= (b*tau/n)*ifft((H.*fft(ycomp)));filter_out = h;tout = 0:ts:ts*(length(filter_out)-1);filter_out = filter_out./max(filter_out);subplot(2,1,2)plot((10350+delr)./1000,20*log10( filter_out+0.00004));xlabel('\bf Target range in km');ylabel('\bf Output vs. range')grid