www.pudn.com > pulse_simulation_of_LFM_radar.rar > chirpaftermatchedfilter.m

%%demo of chirp signal after matched filter 
T=10e-6;                                   %pulse duration10us 
B=30e6;                                    %chirp frequency modulation bandwidth 30MHz 
K=B/T;                                       %chirp slope 
Fs=10*B;Ts=1/Fs;                     %sampling frequency and sample spacing 
N=T/Ts; 
t=linspace(-T/2,T/2,N); 
St=exp(j*pi*K*t.^2);                     %chirp signal 
Ht=exp(-j*pi*K*t.^2);                    %matched filter 
Sot=conv(St,Ht);                         %chirp signal after matched filter 
subplot(211) 
L=2*N-1; 
t1=linspace(-T,T,L); 
Z=abs(Sot);Z=Z/max(Z);             %normalize  
Z=20*log10(Z+1e-6); 
Z1=abs(sinc(B.*t1));                   %sinc function 
Z1=20*log10(Z1+1e-6); 
t1=t1*B;                                          
plot(t1,Z,t1,Z1,'r.'); 
axis([-15,15,-50,inf]);grid on; 
legend('emulational','sinc'); 
xlabel('Time in sec \times\itB'); 
ylabel('Amplitude,dB'); 
title('Chirp signal after matched filter'); 
subplot(212)                              %zoom 
N0=3*Fs/B; 
t2=-N0*Ts:Ts:N0*Ts; 
t2=B*t2; 
plot(t2,Z(N-N0:N+N0),t2,Z1(N-N0:N+N0),'r.'); 
axis([-inf,inf,-50,inf]);grid on; 
set(gca,'Ytick',[-13.4,-4,0],'Xtick',[-3,-2,-1,-0.5,0,0.5,1,2,3]); 
xlabel('Time in sec \times\itB'); 
ylabel('Amplitude,dB'); 
title('Chirp signal after matched filter (Zoom)');