spreader.m

Spread-spectrum techniques are methods by which electromagnetic energy generated in a particular ban

function [sig1,sig2]=spreader(Isymbols,Qsymbols,seq1,seq2,N)
%Bob Gess, June 2008 for EE473 (Header data  and time vector from QPSK_TX_IQ_RX program
%written by JC and posted to Mathworks Dec 2005)

%This module spreads the data by the PRN sequence generated previously

%The plots are scaled by the data rate.  If you have a high ratio between
%the chip rate and the data rate, some of the plots become unintelligible.

%N=1e3;		        % Number of data bits(bit rate)
fs=40*2e3;		    % Sampling frequency
Fn=fs/2;            % Nyquist frequency
Ts=1/fs;	        % Sampling time = 1/fs
T=1/N;		        % Bit time
randn('state',0);   % Keeps PRBS from changing on reruns
td=[0:Ts:(N*T)-Ts]';% Time vector(data)(transpose)

tiq = [0:Ts*2:(N*T)-Ts]';% Time vector for I and Q symbols(transpose)

%Spreading data by prn sequences
sig1=Isymbols.*seq1;
sig2=Qsymbols.*seq2;

%=====================================================================
%Plots
%======================================================================
figure(2)

subplot(2,1,1)
plot(tiq,sig1)
axis([0 5/N -2 2]);
grid on
xlabel('                                                          Time')
ylabel('Amplitude')
title('I Channel(one bit/symbol(phase)) Data')

subplot(2,1,2)
plot(tiq,sig2)
axis([0 5/N -2 2]);
grid on
xlabel('                                                          Time')
ylabel('Amplitude')
title('Q Channel(one bit/symbol(phase)) Data')

end