zspsk.m

用MATLAB仿真雷达的函数

%%%%%产生理想的7位巴克码2PSK信号%%%%%%
code=[1,1,1,-1,-1,1,-1];   %7位巴克码
tao=0.5e-6;   %脉冲带宽0.05us
f0=10e6;    %载波10MHz
fs=40e6;    %采样频率40MHz
ts=1/fs;
t_tao=0:1/fs:tao-1/fs;
n=length(code);
pha=0;
t=0:1/fs:7*tao-1/fs;
s=zeros(1,length(t));
for i=1:n
    if code(i)==1
        pha=0;
    else
        pha=pi;
    end
    s(1,(i-1)*length(t_tao)+1:i*length(t_tao))=cos(2*pi*f0*t_tao+pha);
end
figure,plot(t,s),xlabel('t(单位：S）');title('二相码（7位巴克码）');
%%%%%%%%%正交解调%%%%
N=length(t);
n=0:N-1;
local_oscillator_i=cos(n*f0/fs*2*pi);    %I路本振信号
local_oscillator_q=sin(n*f0/fs*2*pi);    %Q路本振信号
fbb_i=local_oscillator_i.*s;  %I路解调
fbb_q=local_oscillator_q.*s;  %Q路解调
window=chebwin(51,40);   %采用50阶cheby窗的FIR低通滤波器
[b,a]=fir1(50,0.5,window);
fbb_i=[fbb_i,zeros(1,25)];   %信号扩展
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);    %截取有效信息
fbb_q=fbb_q(26:end);
fbb=fbb_i+j*fbb_q;
%%%%%%%%%产生7位巴克码2PSK脉冲压缩系数%%%%%%%
M=4096;   %作4096点的FFT
t1=100e-6;  
t=tao*length(code);
match_filter=2*ts*fliplr(conj(fbb))*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）');
%%%%%%%%%%产生理想点目标回波信号%%%%%%%%%%%
fbb=fbb_i+j*fbb_q;
t1=100e-6;
t=tao*length(code);
signal=[zeros(1,(t1-2*t)/ts),s,zeros(1,t/ts)];
%%%%%%%%%%正交解调%%%%%%%%%%%
N=length(signal);
n=0:N-1;
local_oscillator_i=cos(n*f0/fs*2*pi);   %I路本振信号
local_oscillator_q=sin(n*f0/fs*2*pi);   %Q路本振信号 
fbb_i=local_oscillator_i.*signal;   %I路解调
fbb_q=local_oscillator_q.*signal;   %Q路解调
window=chebwin(51,40);   %采用50阶cheby窗的FIR低通滤波器
[b,a]=fir1(50,0.5,window);
fbb_i=[fbb_i,zeros(1,25)];   %信号扩展
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),
xlabel('时间，单位：S');title('回波信号（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');