ex9_11.m

MATLAB的程序

lear  all;
close  all;
clc;
t=10e-6;
fs=40e6;
ts=1/fs;
fc=9e6;
f0=10e6;
B=2e6;
ft=0:1/fs:t-1/fs;
N=length(ft);
k=B/fs*2*pi/max(ft);
y=modulate(ft,fc,fs,'fm',k);
y_fft_result=fft(y);
%%%%%%%%%%%%%%%%%正交解调%%%%%%%%%%%%%%%
n=0:N-1;
local_oscillator_i=cos(n*f0/fs*2*pi);
local_oscillator_q=sin(n*f0/fs*2*pi);
fbb_i=local_oscillator_i.*y;
fbb_q=local_oscillator_q.*y;
window=chebwin(51,40);
[b,a]=fir1(50,2*B/fs,window);
fbb_i=[fbb_i,zeros(1,25)];
fbb_q=[fbb_q,zeros(1,25)]
fbb_i=filter(b,a,fbb_i);
fbb_q=filter(b,a,fbb_q);
fbb_i=fbb_i(26:end);
fbb_q=fbb_q(26:end);
fbb=fbb_i+j*fbb_q;
%%%%%%%%产生理想线性调频脉冲压缩系数%%%%%%%%%%%%%%%%
M=4096;
D=B*t;
match_filter=ts*fliplr(conj(fbb))*sqrt(D)*2/t;
match_filter_fft=fft(match_filter,M);
figure,
subplot(2,1,1),plot(real(match_filter_fft)),title('脉冲压缩系数（实部）');
subplot(2,1,2),plot(imag(match_filter_fft)),title('脉冲压缩系数（虚部）');
%%%%%%%%%%%%%%%%产生理想回波信号%%%%%%%%%%%%
t1=100e-6;
%signal=y;
signal=[zeros(1,(t1-2*t)/ts),y,zeros(1,t/ts)];
n=0:t1/ts-1;
local_oscillator_i=cos(n*f0/fs*2*pi);
local_oscillator_q=sin(n*f0/fs*2*pi);
fbb_i=local_oscillator_i.*signal;
fbb_q=local_oscillator_q.*signal;
window=chebwin(51,40);
[b,a]=fir1(50,2*B/fs,window);
fbb_i=[fbb_i,zeros(1,25)];
fbb_q=[fbb_q,zeros(1,25)]
fbb_i=filter(b,a,fbb_i);
fbb_q=filter(b,a,fbb_q);
fbb_i=fbb_i(26:end);
fbb_q=fbb_q(26:end);
signal=fbb_i+j*fbb_q;

%%%%%%%%%%%%%%%%%%%脉冲压缩处理%%%%%%%%%%%%%%%%

signal_fft=fft(signal,M);
pc_result_fft=signal_fft.*match_filter_fft;
pc_result=ifft(pc_result_fft,M);

figure,
subplot(2,1,1),plot((0:ts:t1-ts),signal),title('解调后');
subplot(2,1,2),plot((0:ts:length(signal)*ts-ts),abs(pc_result(1:length(signal)))),
xlabel('时间，单位：s'),title('回波脉冲压缩处理结果');