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

function [SD] = Demodulator(RxIn, PN, MF, Walsh); 
% 
% DEMODULATOR			This function performs demodulation of the forward 
%                                       Channel packet, based on RAKE Receiver 
% 						Block Diagram 
%						Input Signal -> [Matched Filter] -> [Sampler] -> [RAKE Receiver] -> [Walsh] -> [DeSpreading] 
% 
% 						Inputs: RxIn - input signal (I/Q) analoge 
%                                    PN - PN sequence (used for De-spreading) 
%                                    MF - matched filter taps 
%                                    Walsh - Used row of Walsh matrix for  recovering 
% 
% 						Outputs: SD - Soft Decisions of RAKE receiver 
% 
 
global R  
N = length(RxIn)/R; 
 
%--------------- Matched Rx Filter (Analog) -------------------- 
L = length(MF); 
L_2 = floor(L/2); 
rr = conv(flipud(conj(MF)), RxIn); 
rr = rr(L_2+1: end - L_2); 
 
%----------- Rx Symbols Sampling ------------ 
% R = 1.2288 Mcps 
Rx = sign(real(rr(1:R:end))) + j*sign(imag(rr(1:R:end)));   
 
%----------- RAKE Receiver ------------ 
Rx = reshape(Rx, 64, N/64); 				% -------- column oriented 
 
%-------- Walsh recovering --------- 
Walsh = ones(N/64, 1)*sign(Walsh'-1/2);	%--- row oriented Walsh  
PN = reshape(PN, 64, N/64)'; 					%--- conjugated row oriented PN sequence 
PN = PN.*Walsh;									%--- Walsh Orthogonalization  
 
%---------- Despreading (Correlate and Sum) 
% Input Rate = 1.2288 Mpbs, Output Rate = 19.2 KBps 
SD= PN*Rx;  	 
SD= real(diag(SD));  % Find Soft Decisions (on main diagonal)