cacode.m

GPS的CA码捕获跟踪源代码

function CA_Code = CAcode(phcode,fd,Loop_time)

global time_cyc;
global fs;
global nn;
global F_if;
global CA_freq;
global tc;
global CA;
global F_Carrier;

ts = (1+(fd/F_Carrier))/fs;



if(phcode < 0)
    offset = (1023+phcode)/(CA_freq);   
else
    offset = phcode/(CA_freq);
end

CA_S=[];
for i = 0:nn-1
    time_dyn = mod((ts*(i+nn*(Loop_time-1))+offset),time_cyc); 
%     time_dyn = mod(ts*i+offset,time_cyc);
    n = ceil(time_dyn/tc)+1;
    if (n > length(CA))
        n = n-1;
    else
        n = n;
    end
    CA_S(i+1) = CA(n);
end
CA_S;
CA_Code = CA_S;