www.pudn.com > Simulation.zip > Modulator.m

function [TxOut, PN, MF] = Modulator(chips, MFType, Walsh); 
% 
% MODULATOR			This function modulate the forward Channel chips. 
% 						Block Diagram 
%						InChips -> [Walsh] -> [Spreading] -> [Output Tx Shaping Filter] 
% 
% 						Inputs: chips - chips sequence to transmit 
%                                    MFType - Shaping Filter type (default - Rise Cosine) 
%                                    Walsh - Used row of Walsh matrix 
% 
% 						Outputs: TxOut - Transmitted signal (analog signal) 
%                                       PN - PN sequence for I/Q Channels 
%									    MF - mathed filter taps (Shaping Filter) 
 
global Zi Zq show R Gi Gq 
 
N = length(chips)*length(Walsh);  	% Number of output chips 
 
%-------- Walsh covering --------- 
% Input Rate = 19.2 KBps, Output Rate = 1.2288 Mcps 
tmp = sign(Walsh-1/2)*sign(chips'-1/2); 
chips = reshape(tmp, prod(size(tmp)), 1); 
 
%-------- PN Spreading sequences generation--------- 
% Rate = 1.2288 Mcps 
[PNi Zi] = PNGen(Gi, Zi, N);  % I-channel PN generation 
[PNq Zq] = PNGen(Gq, Zq, N);  % Q-channel PN generation 
 
PN = sign(PNi-1/2) + j*sign(PNq-1/2); 
 
%--------------- Signal Spreading -------------------- 
% Rate = 1.2288 Mcps 
chips_out = chips.*PN;     % (I-Q signal) 
 
chips = [chips_out, zeros(N, R-1)];	% Pulse generation 
chips = reshape(chips.' , N*R, 1); 
 
 
%--------------- Shaping Filter -------------------- 
switch (MFType) 
case 1 
   %----------------- Raised Cosine filter ------------    
   L = 25; 
   L_2 = floor(L/2); 
   n = [-L_2:L_2]; 
   B = 0.7; 
   MF = sinc(n/R).*(cos(pi*B*n/R)./(1-(2*B*n/R).^2)); 
   MF = MF/sqrt(sum(MF.^2)); 
    
case 2 
   %----------------- Rectangular Filter ------------    
   L = R; 
   L_2 = floor(L/2); 
   MF = ones(L, 1); 
   MF = MF/sqrt(sum(MF.^2)); 
    
case 3 
   %----------------- Triangular Filter ------------    
   L = R; 
   L_2 = floor(L/2); 
   MF = hamming(L); 
   MF = MF/sqrt(sum(MF.^2)); 
    
end 
 
MF = MF(:); 
 
%---------------- Transmit ----------------- 
TxOut = sqrt(R)*conv(MF, chips)/sqrt(2); 
TxOut = TxOut(L_2+1: end - L_2); 
 
 
if (show) 
   figure; 
   subplot(211); plot(MF, '-o'); title('Matched Filter'); grid on; 
   subplot(212); psd(TxOut, 1024, 1e3, 113); title('Spectrum'); 
end