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%A.1 C/A Code Generator 
function CA = cacode(n, chiprate, fs, n_samples,coph) 
% The funtion 
% CA = cacode(n, chiprate, fs, n_samples) 
% returns the Gold code for GPS satellite ID n 
% n = 1..32 
% chiprate = number of chips per second. 
% fs = sampling freqeuncy 
% n_samples = number of samples 
% The code is represented at levels : -1 for bit = 0 
% 1 for bit = 1 
% phase assignments 
phase=[2 6; 3 7; 4 8; 5 9; 1 9; 2 10; 1 8; 2 9; 3 10; 
2 3; 3 4; 5 6; 6 7; 7 8; 8 9; 9 10; 1 4; 2 5; 
3 6; 4 7; 5 8; 6 9; 1 3; 4 6; 5 7; 6 8; 7 9; 
8 10; 1 6; 2 7; 3 8; 4 9]; 
% Intial state - all ones 
G1 = -1*ones(1,10); 
G2 = G1; 
% Select taps for G2 delay 
s1 = phase(n,1); 
s2 = phase(n,2); 
tmp=0; 
for i=1:1023; 
% Gold-code 
G(i)=G2(s1)*G2(s2)*G1(10); 
% Generator 1 - shift reg 1 
tmp=G1(1); 
G1(1)=G1(3)*G1(10); 
G1(2:10)=[tmp G1(2:9)]; 
 
% Generator 2 - shift reg 2 
tmp=G2(1); 
G2(1)=G2(2)*G2(3)*G2(6)*G2(8)*G2(9)*G2(10); 
G2(2:10)=[tmp G2(2:9)]; 
end; 
G 
G=[G G G G G]; 
G=[G G G G G]; 
% Resample - doesn't work for (i*chiprate/fs)>1023 
% but replica chiprate is constant in this 
% implementation 
i=1:n_samples; 
CA(i) = G(ceil((i/fs+coph)*chiprate)+1023);