lpm.zip_lfm_matlab_problemol6_线性调频信号_雷达

%3．LFM信号的雷达监测仿真 % input('\nPulse radar compression processing: \n '); clear; close all; T=10e-6; B=30e6; Rmin=8500;Rmax=11500; R=[9000,10000,10200]; RCS=[1 1 1 ]; C=3e8; K=B/T; Rwid=Rmax-Rmin; Twid=2*Rwid/C; Fs=5*B;Ts=1/Fs; Nwid=ceil(Twid/Ts); t=linspace(2*Rmin/C,2*Rmax/C,Nwid); M=length(R); td=ones(M,1)*t-2*R'/C*ones(1,Nwid); SNR=[1,0.1,0.01,0.001,10,100,1000]; for i=1:1:7 Srt1=RCS*(exp(1i*pi*K*td.^2).*(abs(td)<T/2)); n=sqrt(0.5*SNR(i))*(randn(size(Srt1))+1i*randn(size(Srt1))); Srt=Srt1+n; %Digtal processing of pulse compression radar using FFT and IFFT Nchirp=ceil(T/Ts); Nfft=2^nextpow2(Nwid+Nwid-1); Srw=fft(Srt,Nfft); Srw1=fft(Srt1,Nfft); t0=linspace(-T/2,T/2,Nchirp); St=exp(1i*pi*K*t0.^2); Sw=fft(St,Nfft); Sot=fftshift(ifft(Srw.*conj(Sw))); Sot1=fftshift(ifft(Srw1.*conj(Sw))); N0=Nfft/2-Nchirp/2; Z=abs(Sot(N0:N0+Nwid-1)); figure subplot(211) plot(t*1e6,real(Srt)); axis tight; xlabel('us');ylabel('幅度') title(['加噪线性调频信号压缩前,SNR =',num2str(-1*10*log10(SNR(i)))]); subplot(212) plot(t*C/2,Z) xlabel('Range in meters');ylabel('幅度') title(['加噪线性调频信号压缩后,SNR =',num2str(-1*10*log10(SNR(i)))]); end