fsk.rar_fsk 解调

%sim_FSK_bandpass_noncoherent.m % simulates a digital communication system % with non-coherent FSK signaling in Fig.7.4.2 %Copyleft: Won Y. Yang, wyyang53@hanmail.net, CAU for academic use only clear, clf b=1; M=2^b; % # of bits per symbol and the modulation order SNRbdBt=0:0.1:10; SNRbt=10.^(SNRbdBt/10); pobet=exp(-SNRbt/4)/2; % Eq.(7.2.20) Tb=1; Ts=b*Tb; % Bit/Symbol time Ns=32; T=Ts/Ns; LB=4*Ns; LBN1=LB-Ns+1; % Sample time and Buffer size Es=2; % Energy of signal waveform wc=8*pi/Ts; dw=2*pi/Ts; w=wc+[0:M-1]*dw; wcT=wc*T; t=[0:Ns-1]*T; tt=[0:LB-1]*T; nd=0; % Delay sample time (time offset between XMTR and RCVR clocks) for m=1:M % BFSK signal waveforms sw(m,:)=sqrt(2*Es/Ts)*cos(w(m)*t); su(2*m-1:2*m,:)=sqrt(2/Ts)*[cos(w(m)*t); sin(w(m)*t)]; end suT=su*T; ss=[0; 1]; SNRdBs=[1:10]; MaxIter=10000; % Range of SNRbdB and # of iterations for iter=1:length(SNRdBs) SNRbdB= SNRdBs(iter); SNR=10^(SNRbdB/10); N0=2*(Es/b)/SNR; sigma2=N0/2; sgmsT=sqrt(sigma2/T); st=zeros(1,LB); sws=zeros(1,LB); y=zeros(M,LB); yn=zeros(M,1); r=zeros(1,LB); yr=zeros(M,LB); yrn=zeros(M,1); nobe= 0; % Number of bit errors to be accumulated for k=1:MaxIter i=ceil(rand*M); s=ss(i,:); % Signal index, Data bits to transmit for n=1:Ns % Operation per symbol time sws=[sws(2:LB) sw(i,n)]; % updates the signal waveform buffer st=[st(2:LB) sws(end-nd)]; % Uncontaminated received signal ycss=suT*st(LBN1:LB)'; % Correlator output with no noise for m=1:M, yn(m)=ycss(2*m-1)^2+ycss(2*m)^2; end y=[y(:,2:LB) yn]; % Envelope detector output wct=wcT*(n-1); bp_noise= randn*cos(wct)-randn*sin(wct); r=[r(2:LB) sws(end-nd)+sgmsT*bp_noise]; % Received signal ycss=suT*r(LBN1:LB)'; % Correlator output with noise for m=1:M, yrn(m)=ycss(2*m-1)^2+ycss(2*m)^2; end yr=[yr(:,2:LB) yrn]; % Envelope detector output buffer end %Detector(DTR) [yremax,mmax]=max(yrn); d=ss(mmax,:); % Detected data bits nobe=nobe+sum(s~=d); if nobe>100; break; end end pobe(iter)= nobe/(k*b); end subplot(221), plot(tt,st,'k', tt,r,'b:'), title(' r(t)') subplot(222), plot(tt,y(1,:),'k', tt,yr(1,:),'b:') hold on, plot([1:4]*Tb-T,yr(1,[1:4]*Ns),'+'), title('y0(t)') subplot(224), plot(tt,y(2,:),'k', tt,yr(2,:),'b:') hold on, plot([1:4]*Tb-T,yr(2,[1:4]*Ns),'+'), title('y1(t)') subplot(223), semilogy(SNRbdBt,pobet,'k-', SNRdBs,pobe,'b*') title('Bit Error Probability for non-coherent BFSK Signaling')