matlab_扩频通信系统仿真_频谱扩展_伪随机序列编码调制

%function PNCode=Code() %生成31位m序列 %设置码片速率100bpsk %码片速率1/Tc=3100cps %fb=12400hz % %fs=fb*16 a=[1,1,1,1,1]; m=[0,0,1,0,1]; PNCode=[]; for i=1:31 R=mod(sum(a.*m),2); PNCode=[PNCode,a(5)]; a=[R,a(1:4)]; end N=10; %function signal=signalsource(N) %signal=signalsource() %函数输出signal为欲传输的01比特流 %函数输入N为生成的01比特流的个数 signal=rand(1,N)>0.5;%生成个数为N的01比特流 signal_spreading =[]; PNCode_spreading =[]; for i=1:length(signal) for j=1:31 signal_spreading=[signal_spreading,signal(i)]; end PNCode_spreading=[PNCode_spreading,PNCode]; end signal2=signal_spreading.*PNCode_spreading; fb=1240; %bit速率12400hz fc=1240*3; %载波频率fc=250*1000 %function signal_bpsk=bpsk(signal2，fb，fc) %bpsk函数实现信号的bpsk调制 %signal2 %fb为调制信号的比特速率 %fc为载波信号的速率 %t=linspace(0,1/fc,64); t=1/(fc*16):1/(fc*16):1/fc; %时间轴t,每个周期抽样点数16 carrier1=[]; carrier2=[]; for i=1:(fc/fb); %fc/fb每个bit包含的载波周期 carrier1=[carrier1,cos(2*pi*fc*t)]; carrier2=[carrier2,cos(2*pi*fc*t-pi)]; end figure(1); subplot(2,1,1); plot(carrier1); grid on; subplot(2,1,2); plot(carrier2); grid on; signal_bpsk=[]; for i=1:length(signal2) if signal2(i)==1 signal_bpsk=[signal_bpsk,carrier1]; else signal_bpsk=[signal_bpsk,carrier2]; end end figure(2); subplot(2,1,1); plot(signal_bpsk); title('signal_ bpsk'); grid on; axis([0,100,-1,1]); %function transmitted=channel(signal_bpsk,snr) %加噪声 transmitted=awgn(signal_bpsk,20); subplot(2,1,2); plot(transmitted); grid on; axis([0,100,-1,1]); title('signal_ awgn') %function %解扩 PNCode_spreading=[]; for i=1:31 %length(PNCode)=31 for j=1:16*fc/fb %每个载波周期抽样点数为16 PNCode_spreading=[PNCode_spreading,PNCode(i)]; %将PNCode数组中的每个元素扩展为每个bit包含的载波周期的长度，即16*fc/fb end end PNCode_spread=[]; for i=1:N PNCode_spread=[PNCode_spread,PNCode_spreading]; end %将扩展之后的PNCode_spreading变为双极性码 for i=1:length(PNCode_spread) if PNCode_spread(i)==0 PNCode_spread(i)=-1; end end signal3=PNCode_spread.*transmitted; figure(3); subplot(2,1,1); plot(signal3); grid on; axis([0,200,-1,1]); title('与PNcode进行相异或后的信号'); %带通滤波 load Bandpass; den=1; signal4=filter(BandNum,den,signal3); subplot(2,1,2); plot(signal4); grid on; axis([0,100,-1,1]); title('signal_ reverseSpread'); %function %解调 carrier=[]; for i=1:length(signal4)/length(carrier1) carrier=[carrier,carrier1]; end x=signal4.*carrier; figure(4); subplot(2,1,1); plot(x); grid on; axis([100,200,-1,1]); %低通滤波器 load Lowpass; den=1; signal_demo=filter(LowNum,den,x); subplot(2,1,2); plot(signal_demo); %axis([100,200,-1,1]); grid on; signal_demodulation=[]; for i=(16*3/2):(16*3):(length(signal_demo)-8) if signal_demo(i)>0 signal_demodulation=[signal_demodulation,1]; else signal_demodulation=[signal_demodulation,0]; end end %function signal_reverse=[]; i=1; for j=16:31:31*N signal_reverse(i)=signal_demodulation(j); i=i+1; end