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HFM信号
HFM 信号表达式:
式中:T 为脉冲宽度,b = -k / f1 f2 为信号的调频参数,k = B / T 为对应的线性调频斜率,B 为信号带宽,f0 为波形中心频率,f1 = f0 -B / 2 为下限频率,f2 =f0 +B / 2 为上限频率。
仿真结果：
clcclearclose all%%Hfmfc=12.5e3;fs=5*fc;ts=1/fs;N=450;T=(1/fs)*N;B=6000;fmax=fc/(1-B/(2*fc));fmin=fc/(1+B/(2*fc));bw=fmax-fmin;t0=fc*N*ts/B;K=N*ts*fmax*fmin/B;W=B*N*ts;t=(-(N-1)/2:1:(N-1)/2).'*ts;x0=exp(-1i*(2*pi*K*log(1-t/t0)));m=bw/T;v=9;c=1500;D=1+2*v/c;ft=fc./(1-(m/fc).*t);ftr=fc*D./(1-(m/fc).*D*t);figure(1)plot(t,ft,t,ftr);grid ontr=((-(N-1)/2:1:(N-1)/2).'+50)*ts;xr=exp(-1i*(2*pi*K*log(1-tr/t0)));prf=100;L=round((1/prf)/ts);x=zeros(L,1);x(1:1:N,1)=x0;[afmag,delay,doppler]=ambgfun(x,fs,prf);ambgu=afmag.*(afmag>0.5);figure(2)% contour(delay,doppler,afmag,'ShowText','on');mesh(delay,doppler,afmag);xlim([-8e-3,8e-3]);ylim([-6600,6600]);xlabel('Delay (second)');ylabel('Doppler Shift (hertz)');colormap jet;colorbar;grid onfigure(3)contour(delay,doppler,ambgu);xlim([-8e-3,8e-3]);ylim([-7600,7600]);xlabel('Delay (second)');ylabel('Doppler Shift (hertz)');colormap jet;colorbargrid on%%afmag_T0=afmag(1025,:);afmag_f0=afmag(:,625);figure(4)plot(delay*1000,afmag_T0);xlabel('Delay (ms)');ylabel('Amplitude');grid onxlim([-2 2]);ylim([0 1]);hold onhline=refline(0,0.7);hline.Color='r';hline.LineStyle='--';hline.LineWidth=1.2;plot([-0.44/bw -0.44/bw]*1000,[0 1],'r--','LineWidth',1.2);figure(5)plot(doppler,afmag_f0);xlabel('Doppler Shift (hertz)');ylabel('Amplitude');xlim([-3/T 3/T]);ylim([0 1]);grid onhold onhline=refline(0,0.7);hline.Color='r';hline.LineStyle='--';hline.LineWidth=1.2;plot([-0.44/T -0.44/T]*1000,[0 1],'r--','LineWidth',1.2);%%signaltx=(0:1:L-1)*ts*1000;figure(6)subplot(2,1,1)plot(t,real(x0));ylim([-1.1 1.1]);xlabel('Time/ms');ylabel('Amplitude');grid onsubplot(2,1,2)nfft=2^nextpow2(450);fre=(0:1:nfft/2)*fs/nfft/1000;fftr=fft(x(1:450,1),nfft);plot(fre,abs(fftr(1:1:nfft/2+1,1)));xlabel('Frequency/kHz');ylabel('Amplitude');grid on
