LFM.rar_lfm_脉冲压缩_雷达

clear;clc;close all; K=5e12; T=42e-6; B=K*T; ratio1=1.4; fs=B*ratio1; ratio2=1.4; dt=1/fs; Nrh=ceil(T/2/dt*ratio2); Nr=Nrh*2+1; t=dt*(-Nrh:Nrh); df=fs/Nr; f=df*(-Nrh:Nrh); s=exp(1i*pi*K*t.^2).*(abs(t)<T/2); figure,plot(t*1e6,abs(s)); xlabel('time(us)'); ylabel('amplitude'); axis tight; figure,plot(t*1e6,real(s)); figure;plot(t*1e6,imag(s),'r'); s_phase=unwrap(angle(s)); figure,plot(s_phase); sf=fftshift(fft(ifftshift(s))); figure,plot(f*1e-6,real(sf)); figure,plot(f*1e-6,imag(sf),'r'); xlabel('frequency(MHz)'); ylabel('amplitude'); sf_phase=unwrap(angle(sf)); figure,plot(sf_phase); %%非基带 tc=T/4; s1=exp(1i*pi*K*(t-tc).^2).*(abs(t)<T/2); sf1=fftshift(fft(ifftshift(s1))); figure,plot(t*1e6,real(s1)); xlabel('time(us)'); ylabel('amplitude'); figure,plot(f*1e-6,real(sf1)); xlabel('frequency(MHz)'); ylabel('amplitude'); %%时域卷积 h=exp(-1i*pi*K*t.^2).*(abs(t)<T/2); sc_conv=conv(s,h); t_new=dt*(-Nr+1:Nr-1); figure,plot(t_new*1e6,abs(sc_conv)); xlabel('time(us)'); ylabel('amplitude'); sc_xcorr=xcorr(s,s); figure,plot(t_new*1e6,abs(sc_xcorr)); xlabel('time(us)'); ylabel('amplitude'); %%加窗 wnh=round(T/2/dt); wn=2*wnh+1; beta=2.5; window=kaiser(wn,beta); h(Nrh+1-wnh:Nrh+1+wnh)=h(Nrh+1-wnh:Nrh+1+wnh).*window.'; sc_conv_win=conv(s,h); t_new=dt*(-Nr+1:Nr-1); alpha=10;%%升采样倍数 sc_cw_up=ifft(fftshift(fft(sc_conv_win)),alpha*(2*Nr-1)); sc_c_up=ifft(fftshift(fft(sc_conv)),alpha*(2*Nr-1)); G1=20*log10(abs(sc_cw_up)/max(abs(sc_cw_up))); G2=20*log10(abs(sc_c_up)/max(abs(sc_c_up))); figure,plot(G1); hold on;plot(G2,'r'); ylim([-40 0]); legend('加窗后','加窗前');