LFMchirpdechirp.zip_DEMO_LFM chirp_Lfm dechirp_dechirp_lfm

%%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 figure(1) 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 result','sinc function'); xlabel('Time in sec times\itB'); ylabel('MagnituddB'); title('\fontsize{9}脉冲压缩后的回波(归一化后)'); figure(2) %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]); legend('\fontsize{9}仿真结果','理论结果'); xlabel('\fontsize{9}时间\times\itB (s)'); ylabel('\fontsize{9}相对幅度dB'); title('\fontsize{9}脉冲压缩后的回波(归一化后局部图)'); %%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)');