bask1.m

有关信号的调制

% bask1.m
%
% Simulation program to realize BASK transmission system
% 没有过采样的
% Programmed by snowflier,
%

%******************** basic information of the signal **********************

T=1          % time duration
delta_T=T/200;        % the interval of the signal
alpha=0.5;   % rolloff factor
fc=40/T;   % carrier frequency
t=-5*T+delta_T:delta_T:5*T;      % time
N=length(t);    % Number of signals

%******************** Data generation ********************************  

	data=rand(1,N)>0.5;  % rand: built in function
        data=data.*2-1;
        

%******************* Filter initialization ********************

for i=1:N
  if(abs(t(i))~=T/(2*alpha)),
      g_T(i)=sinc(t(i)/T)*(cos(pi*alpha*t(i)/T)/(1-4*alpha^2*t(i)^2/T^2));
  else
      g_T(i)=0;
end;
end;
         data1=conv(data,g_T);

%********************modulation********************************
delta_T1=1/length(data1);
t1=delta_T1:delta_T1:T;
 bask=data1.*cos(2*pi*fc*t1);
 figure(1)
 subplot(211)
 plot(t,g_T)
 subplot(212)
 plot(t1,bask);
 
 %*******************spectrem**********************************
 G_T=abs(fft(g_T));
 Bask=abs(fft(bask));
 f=-0.5/delta_T:1/(delta_T*(N-1)):0.5/delta_T;
 f1=-0.5/delta_T1:1/(delta_T1*(length(data1)-1)):0.5/delta_T1;
 figure(2)
 subplot(211)
 plot(f,fftshift(G_T))
 subplot(212)
 plot(f1,fftshift(Bask));