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    function [TxOut, PN, MF] = Modulator(chips, MFType, Walsh); 
%此函数用于实现IS-95前向链路系统的数据调制
% chips为发送的初始数据
% MFType为成型滤波器的类型选择 
% Walsh为walsh码
% TxOut为调制输出信号序列 
% PN为用于扩频调制的PN码序列
% MF为匹配滤波器参数
global Zi Zq show R Gi Gq  
N = length(chips)*length(Walsh);   
% 输入速率 = 19.2 KBps, 输出速率= 1.2288 Mcps 
tmp = sign(Walsh-1/2)*sign(chips'-1/2); 
chips = reshape(tmp, prod(size(tmp)), 1);  
[PNi Zi] = PNGen(Gi, Zi, N);   
[PNq Zq] = PNGen(Gq, Zq, N);   
PN = sign(PNi-1/2) + j*sign(PNq-1/2); 
chips_out = chips.*PN;     
chips = [chips_out, zeros(N, R-1)];	
chips = reshape(chips.' , N*R, 1);  
%成型滤波器
switch (MFType) 
case 1 
   %升余弦滤波器   
   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 
   %矩形滤波器   
   L = R;  L_2 = floor(L/2); 
   MF = ones(L, 1); 
   MF = MF/sqrt(sum(MF.^2));     
case 3 
   %汉明滤波器   
   L = R;  L_2 = floor(L/2); 
   MF = hamming(L); 
   MF = MF/sqrt(sum(MF.^2));     
end  
MF = MF(:);  
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