直扩DS-BPSK抗干扰代码

clear;close all; %---------------------------扩频系统参数设置-------------------------------% rb = 20000; %扩频前的数据速率/bit/s 20k SF = 500; %扩频倍数 Rb = rb*SF; %扩频后的码片速率/Mc/s Tsum = 10; %仿真时间/ms bits_num = rb*Tsum/1000; SNR = 10; %仿真信噪比/dB %% 发射机部分 %----------------------------m 序列产生模块---------------------------------% %产生m序列 load Coef.mat n = floor(log2(500))+2;%m序列的长度 fx = (de2bi(base2dec(Coef.Ci(n-2),8),n+1,2)); fx = fliplr(fx(1:end-1)); % fx = (de2bi(primpoly(n-1,'max'),n,2)); reg = [zeros(1,n-1) 1]; %移位寄存器的初始状态 mseq = zeros(n,1); mseq(1)= reg(n); N = 2^(n-1)-1; for i = 2:N regTemp = zeros(1,n); regTemp(1)= mod(sum(fx.*reg),2); for j = 2:n regTemp(j)= reg(j-1); end reg = regTemp; %移位后的寄存器 mseq(i) = reg(n); %新的寄存器输出 end mseq = 1-2*mseq(1:SF);% 1->-1 0->1 mseq_rp = reshape(repmat(mseq',bits_num,1)',bits_num*SF,1); % figure;subplot(211);stairs(mseq);subplot(212);stairs(mseq_rp); % figure;xc = xcorr(mseq);plot(xc); %------------------------------BPSK编码-----------------------------------% bits = randi(2,bits_num,1); %仿真比特数据 0 1 CFdata = 2*bits-3;%bpsk 调制 2->1 1->-1 %-------------------------------扩频:1 扩 SF--------------------------------% CFdata_os = reshape(repmat(CFdata',SF,1),length(CFdata)*SF,1); DS_data = CFdata_os' .* mseq_rp'; %信道部分，只仿真到中频，不考虑射频部分 %% 接收机部分 %-------------------------------接收信号AD--------------------------------% US = 4; % AD 4倍过采样 DS_data_os = reshape(repmat(DS_data,US,1),length(DS_data)*US,1); CodePhaseShift =123; % 码相位偏移 DS_data_rx = [2*randi(2,1,CodePhaseShift)-3,DS_data_os(1:end - CodePhaseShift)'];% 偏移位置前扩充随机信号 DS_data_rx = awgn(DS_data_rx,100,'measured'); % AWGN信号噪声 %-------------------------------捕获阶段--------------------------------% mseq_rec = reshape(repmat(mseq',US,1),SF*US,1); % 本地扩频码 过采样 disp('----------捕获开始----------'); IntCap = zeros(bits_num,1); flagCapture = zeros(bits_num,1); CPhShiftLocalRec = zeros(bits_num,1); CPhShiftLocal = 0; % 本地码初始相偏 step = US/2; % 捕获阶段 粗捕获 相位移动为1/2个码片 % 串行搜索 for i = 1:bits_num mseq_local = circshift(mseq_rec,CPhShiftLocal);% 循环移位 IntCap(i) = abs(DS_data_rx((i-1)*SF*US+1:step:i*SF*US)*mseq_local(1:step:end)); % coarse if (IntCap(i))>= step*SF/2 % 捕获门限 flagCapture(i) = 1; disp('----------捕获成功！----------'); break; else CPhShiftLocal = CPhShiftLocal+step; % 相位控制字 调整相偏 end CPhShiftLocalRec(i) = CPhShiftLocal; end figure;set(gcf,'Color','w','Position',[100 100 400 350]); subplot(311);stairs(IntCap,'b','LineWidth',0.7);ylim([0 1.2*step*SF]);title('\fontname{宋体}捕获阶段积分结果'); subplot(312);stairs(CPhShiftLocalRec,'b','LineWidth',0.7);title('\fontname{宋体}捕获阶段本地码相位'); subplot(313);stairs(flagCapture,'b','LineWidth',0.7);ylim([-0.2,1.2]);xlabel('i');title('\fontname{宋体}捕获标志位'); %-------------------------------跟踪阶段--------------------------------% CapStarter = i+1; IntE = zeros(bits_num,1); IntL = zeros(bits_num,1); IntDS = zeros(bits_num,1); CPhShiftLocalRec = zeros(bits_num,1); CPhShiftLocalRec(CapStarter -1) = CPhShiftLocal; step = 1; % 相位移动为1/US 个码片 disp('----------跟踪阶段----------'); for i = CapStarter:bits_num mseqE = circshift(mseq_rec,CPhShiftLocal+1); % 超前码 mseqL = circshift(mseq_rec,CPhShiftLocal-1); % 滞后码 IntE(i) = abs(DS_data_rx((i-1)*SF*US+1:step:i*SF*US)*mseqE(1:step:end)); % 超前码积分 IntL(i) = abs(DS_data_rx((i-1)*SF*US+1:step:i*SF*US)*mseqL(1:step:end)); % 滞后码积分 if abs(IntE(i) - IntL(i)) <= step CPhShiftLocal = CPhShiftLocal; elseif IntE(i) > IntL(i) CPhShiftLocal = CPhShiftLocal+step;% 超前支路>滞后支路 调整相偏右移 else CPhShiftLocal = CPhShiftLocal-step; % 超前支路<滞后支路 调整相偏右移 end CPhShiftLocalRec(i) = CPhShiftLocal; mseqDS = circshift(mseq_rec,CPhShiftLocal); IntDS(i) = (DS_data_rx((i-1)*SF*US+1:step:i*SF*US)*mseqDS(1:step:end)); % 本地码积分 end figure;set(gcf,'Color','w','Position',[100 100 400 450]); subplot(411);stairs(IntE,'b','LineWidth',0.7); xlim([CapStarter-2,bits_num]);ylim([-5 1.2*SF*US]);title('\fontname{宋体}超前支路积分'); subplot(412);stairs(IntL,'b','LineWidth',0.7); xlim([CapStarter-2,bits_num]);ylim([-5 1.2*SF*US]);title('\fontname{宋体}滞后支路积分'); subplot(413); plot(CodePhaseShift*ones(bits_num,1),'--r','LineWidth',0.8);hold on; stairs(CPhShiftLocalRec,'b','LineWidth',0.7);hold off;title('\fontname{宋体}本地码相位'); xlim([CapStarter-2,bits_num]);ylim([CodePhaseShift-US CodePhaseShift+US]); subplot(414);stairs(IntDS,'b','LineWidth',0.7); xlim([CapStarter-2,bits_num]);ylim([-1.2*SF*US 1.2*SF*US]);title('\fontname{宋体}本地码积分');xlabel('\it{i}'); %-------------------------------鉴相曲线--------------------------------% mseqE = circshift(mseq_rec,1); mseqL = circshift(mseq_rec,-1); i=20; [r1,lags] = xcorr(DS_data_rx((i-1)*SF*US+1:i*SF*US),mseqE); [r2,~] = xcorr(DS_data_rx((i-1)*SF*US+1:i*SF*US),mseqL); figure;set(gcf,'Color','w','Position',[100 100 400 250]); subplot(211);plot(lags,r2,'r','LineWidth',0.6);hold on; plot(lags,r1,'b','LineWidth',0.6);hold off; legend('\fontname{宋体}超前支路','\fontname{宋体}滞后支路'); xlim([-CodePhaseShift-20*US,CodePhaseShift+20*US]);ylim([-1.2*SF*US,1.2*SF*US]); xlabel('$\tau$','Interpreter','latex'); subplot(212);plot(lags,r2-r1,'color',[0,104,107]/255,'LineWidth',0.6); xlim([-CodePhaseShift-20*US,CodePhaseShift+20*US]);ylim([-1.2*SF*US/2,1.2*SF*US/2]); xlabel('$\tau$','Interpreter','latex');