acqu.m

GPS的CA码捕获跟踪源代码

function [fd_a,f_ac_code] = acqu(Signal_Source)
global fs;
global nn;
global F_if
% ======================================Create Localcode============== %
ph_code = 0;
fd_code = 0;
Loop_time = 1;
CA_Code = CAcode(ph_code,fd_code,Loop_time);
Localcode = CA_Code;


% ==================================function RxSignal============%
x1 = Signal_Source(1:length(Localcode));

t = [0:length(Localcode)-1];
for i=1:41
    fr=F_if-10000+(i-1)*500;
    lc = x1.*exp(j*2*pi*fr.*t./fs);
    xf = fft(lc);
    lcf = fft(Localcode);
    yy(i,:)=ifft(xf.*conj(lcf));
 end
 
L1=length(yy(1,:));
LL=L1;
yy1=zeros(41,LL);
yy1=yy([1:41],[1:LL]);
Corr_value = (abs(yy1)).^2; 
%  figure
%  mesh(Corr_value);

[value,code_p] = max(max( Corr_value));
[value,carrier_p] = max(max( Corr_value'));

fd_a = -10000+(carrier_p-1)*500;
ac_carrier = F_if-10000+(carrier_p-1)*500;

ac_code = nn-code_p-1; 

xsh = nn/1023;
f_ac_code = ac_code/xsh;

showaquc = Corr_value(carrier_p,:);
showzb_mid = [1:nn];
showzb =(nn-showzb_mid-1)/xsh;