新建 文本文档 (7).txt

利用MATLAB对直扩信号的产生进行了研究

% Lab 06 
% WiCom_3 
% By Kashif Shahzad  
% 01-ET-31 
% 3rd July 2004 
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
% Direct Sequence Spread Spectrum 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
clc 
clear 
 
% Generating the bit pattern with each bit 6 samples long 
b=round(rand(1,20)); 
pattern=[]; 
for k=1:20 
    if b(1,k)==0 
        sig=zeros(1,6); 
    else 
        sig=ones(1,6); 
    end 
    pattern=[pattern sig]; 
end 
plot(pattern); 
axis([-1 130 -.5 1.5]); 
title('\bf\it Original Bit Sequence'); 
 
% Generating the pseudo random bit pattern for spreading 
spread_sig=round(rand(1,120)); 
figure,plot(spread_sig); 
axis([-1 130 -.5 1.5]); 
title('\bf\it Pseudorandom Bit Sequence'); 
 
% XORing the pattern with the spread signal 
hopped_sig=xor(pattern,spread_sig); 
 
% Modulating the hopped signal 
dsss_sig=[]; 
t=[0:100];     
fc=.1 
c1=cos(2*pi*fc*t); 
c2=cos(2*pi*fc*t+pi); 
for k=1:120 
    if hopped_sig(1,k)==0 
        dsss_sig=[dsss_sig c1]; 
    else 
        dsss_sig=[dsss_sig c2]; 
    end 
end 
figure,plot([1:12120],dsss_sig); 
axis([-1 12220 -1.5 1.5]); 
title('\bf\it DSSS Signal'); 
 
% Plotting the FFT of DSSS signal 
figure,plot([1:12120],abs(fft(dsss_sig)))