digitizg.m

MATLAB编写的GPS 信号的产生捕获程序

% digitizg.m This prog generates the C/A code and digitizes it
function code2=digitizg(n,fs,offset,svnum);

% code - gold code
% n - number of samples
% fs - sample frequency in Hz;
% offset - delay time in seconds must be less than 1/fs cannot shift
% svnum - satellite number;

gold_rate=1.023e6; %gold code clock rate in Hz.
ts=1/fs;
tc=1/gold_rate;

cmd1=codegen(svnum); % generate C/A code
code_in=cmd1;

% ***** creating 16 C/A code for digitizing *****
code_a=[code_in code_in code_in code_in];
code_a=[code_a code_a];
code_a=[code_a code_a];

% ***** digitizing *****

b=[1:n];
c=ceil((ts*b+offset)/tc);
code=code_a(c);

% ***** adjusting first data point *****

if offset>=0;
    code2=[code(1) code(1:n-1)];
else
    code2=[code(n) code(1:n-1)];
end