Lab_2-QPSK.rar_matlab通信系统_通信系统matlab

clear; clf; %%%%%%%%%%%%%%%%%%%%%%%%% Parameters %%%%%%%%%%%%%%%%%%%%%%%%%%%%% Rs=1200; % Symbol rate Ts=1/Rs; % Symbol interval T=50; % oversample rate = number of samples in a symbol fs=Rs*T; % sampling rate ts=1/fs; N=30; % Length of the seq. n_range=(0:N*T-1); t=n_range*ts; %%%%%%%%%%%%%%%%%%%%%%%%% Baseband signaling %%%%%%%%%%%%%%%%%%%%%%%% bnOri=unifrnd(-1,+1,1,N)>0; bn1ri=unifrnd(-1,+1,1,N)>0; gTpulse=ones(1,T); % NRZ n_dly=n_range+T/2+1; B0=1.0*Rs; OriImpulses=upsample(bnOri,T,T/2); % build the impluse train mOri=conv(OriImpulses,gTpulse); % generate baseband (PAM) signal mOri=mOri(n_dly); m0=2.*mOri-1; riImpulses=upsample(bn1ri,T,T/2); % build the impluse train m1ri=conv(riImpulses,gTpulse); % generate baseband (PAM) signal m1ri=m1ri(n_dly); % time alignment m1=2.*m1ri-1; %%%%%%%%%%%%%%%%%%%%%%%%% Bandpass signaling %%%%%%%%%%%%%%%%%%%%%%%% fc=1800; s1=(1/sqrt(2)).*m1.*cos(2*pi*fc*t); s0=(1/sqrt(2)).*m0.*sin(2*pi*fc*t); s=s1-s0; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% plot %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% sRng=[0,N*(T-1)*ts, -1.5,+1.5]; figure(1); subplot(411),plot(t,m0,'r',t,s0,'b'); axis(sRng); figure(2); subplot(411),plot(t,m1,'r',t,s1,'b'); axis(sRng); figure(3); subplot(411),plot(t,s,'g'); axis(sRng); %%%%%%%%%%%%%%%%%%%%%%%%% AWGN Channel %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% N0=10^2.225/10^7; sigma=sqrt(N0*fs/2); w=normrnd(0,sigma,[1,N*T]); % 正态分布随机数 Es=sum(s.^2)*ts/N; SNR=10*log10(Es/N0); Baud_B0_EbN0=[Rs,B0,SNR] %%%%%%%%%%%%%%%%%%%%%%%%%%% Receiver %%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%% BFP %%%%%%%%%%%%%%%%%%%%%%%%%%% h1BPF=fir1(100,[fc-1200,fc+1200]/(fs/2)); % 考虑101阶 r1=filter(h1BPF,1,s); % BPF for f1 r0=filter(h1BPF,1,s); % BPF for f0 %%%%%%%%%%%%%%%%%%%%%%%%%%% LFP %%%%%%%%%%%%%%%%%%%%%%%%%%% hLPF=fir1(100,[B0]/(fs/2)); %考虑101阶 r1_posi=r1.*cos(2*pi*fc*t); r1_out=filter(hLPF,1,r1_posi); r0_posi=r0.*cos(2*pi*fc*t); r0_out=filter(hLPF,1,r0_posi); r_out=r1_out.*2+r0_out; sRng=[0,N*(T-1)*ts, -1.2,+1.2]; subplot(414),plot(t,r1_posi,'r',t,r1_out,'b',t,r_out,'k'); axis(sRng); %%%%%%%%%%%%%%%%%%%%%%%%%%% PSD %%%%%%%%%%%%%%%%%%%%%%%%%%%% Nfft=length(t);Nfft=2^ceil(log2(Nfft)+2); df=fs/Nfft; fk=(-Nfft/2:Nfft/2-1)*df; Rxx=xcorr(s)/N; sOri1_f=ts*fftshift(fft(Rxx,Nfft)); Rxx=xcorr(s)/N; sOri0_f=ts*fftshift(fft(Rxx,Nfft)); Rxx=xcorr(s)/N; sOri_f=ts*fftshift(fft(Rxx,Nfft)); Rxx=xcorr(s)/N; sAns_f=ts*fftshift(fft(Rxx,Nfft)); Rxx=xcorr(s)/N; s_f=ts*fftshift(fft(Rxx,Nfft)); figure(4); f_range=[0,5000,-40,-10]; subplot(411),plot(fk,10*log10(abs(sOri1_f)),'b',fk,10*log10(abs(sOri0_f)),'r');axis(f_range); subplot(412),plot(fk,10*log10(abs(sOri_f)));axis(f_range); f_range=[0,5000,-40,-20]; subplot(413),plot(fk,10*log10(abs(sOri_f)),'b',fk,10*log10(abs(sAns_f)),'r');axis(f_range); subplot(414),plot(fk,10*log10(abs(s_f)));axis(f_range);