mirror of https://github.com/gnss-sdr/gnss-sdr
388 lines
9.6 KiB
C++
388 lines
9.6 KiB
C++
#include "gps_sdr_signal_processing.h"
|
|
|
|
#include <math.h>
|
|
#include <stdlib.h>
|
|
#include <cmath>
|
|
|
|
/*!
|
|
* The SV ID is _prn=ID -1
|
|
*/
|
|
void code_gen_conplex(std::complex<float>* _dest, int32 _prn, unsigned int _chip_shift) {
|
|
|
|
uint32 G1[1023];
|
|
uint32 G2[1023];
|
|
uint32 G1_register[10], G2_register[10];
|
|
uint32 feedback1, feedback2;
|
|
uint32 lcv, lcv2;
|
|
uint32 delay;
|
|
int32 prn = _prn-1; //Move the PRN code to fit an array indices
|
|
|
|
/* G2 Delays as defined in GPS-ISD-200D */
|
|
int32 delays[51] = {5, 6, 7, 8, 17, 18, 139, 140, 141, 251, 252, 254 ,255, 256, 257, 258, 469, 470, 471, 472,
|
|
473, 474, 509, 512, 513, 514, 515, 516, 859, 860, 861, 862, 145, 175, 52, 21, 237, 235, 886, 657, 634, 762,
|
|
355, 1012, 176, 603, 130, 359, 595, 68, 386};
|
|
|
|
/* A simple error check */
|
|
if((prn < 0) || (prn > 51))
|
|
return;
|
|
|
|
for(lcv = 0; lcv < 10; lcv++)
|
|
{
|
|
G1_register[lcv] = 1;
|
|
G2_register[lcv] = 1;
|
|
}
|
|
|
|
/* Generate G1 & G2 Register */
|
|
for(lcv = 0; lcv < 1023; lcv++)
|
|
{
|
|
G1[lcv] = G1_register[0];
|
|
G2[lcv] = G2_register[0];
|
|
|
|
feedback1 = G1_register[7]^G1_register[0];
|
|
feedback2 = (G2_register[8] + G2_register[7] + G2_register[4] + G2_register[2] + G2_register[1] + G2_register[0]) & 0x1;
|
|
|
|
for(lcv2 = 0; lcv2 < 9; lcv2++)
|
|
{
|
|
G1_register[lcv2] = G1_register[lcv2+1];
|
|
G2_register[lcv2] = G2_register[lcv2+1];
|
|
}
|
|
|
|
G1_register[9] = feedback1;
|
|
G2_register[9] = feedback2;
|
|
}
|
|
|
|
/* Set the delay */
|
|
delay = 1023 - delays[prn];
|
|
delay+=_chip_shift;
|
|
delay %= 1023;
|
|
/* Generate PRN from G1 and G2 Registers */
|
|
for(lcv = 0; lcv < 1023; lcv++)
|
|
{
|
|
_dest[lcv] = std::complex<float>(G1[(lcv+_chip_shift)%1023]^G2[delay], 0);
|
|
if(_dest[lcv].real()==0.0) //javi
|
|
{
|
|
_dest[lcv].real(-1.0);
|
|
}
|
|
delay++;
|
|
delay %= 1023;
|
|
//std::cout<<_dest[lcv].real(); //OK
|
|
}
|
|
|
|
}
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
/*!
|
|
* code_gen, generate the given prn code
|
|
* */
|
|
int32 code_gen(CPX *_dest, int32 _prn)
|
|
{
|
|
|
|
uint32 G1[1023];
|
|
uint32 G2[1023];
|
|
uint32 G1_register[10], G2_register[10];
|
|
uint32 feedback1, feedback2;
|
|
uint32 lcv, lcv2;
|
|
uint32 delay;
|
|
int32 prn = _prn-1; //Move the PRN code to fit an array indices
|
|
|
|
/* G2 Delays as defined in GPS-ISD-200D */
|
|
int32 delays[51] = {5, 6, 7, 8, 17, 18, 139, 140, 141, 251, 252, 254 ,255, 256, 257, 258, 469, 470, 471, 472,
|
|
473, 474, 509, 512, 513, 514, 515, 516, 859, 860, 861, 862, 145, 175, 52, 21, 237, 235, 886, 657, 634, 762,
|
|
355, 1012, 176, 603, 130, 359, 595, 68, 386};
|
|
|
|
/* A simple error check */
|
|
if((prn < 0) || (prn > 51))
|
|
return(0);
|
|
|
|
for(lcv = 0; lcv < 10; lcv++)
|
|
{
|
|
G1_register[lcv] = 1;
|
|
G2_register[lcv] = 1;
|
|
}
|
|
|
|
/* Generate G1 & G2 Register */
|
|
for(lcv = 0; lcv < 1023; lcv++)
|
|
{
|
|
G1[lcv] = G1_register[0];
|
|
G2[lcv] = G2_register[0];
|
|
|
|
feedback1 = G1_register[7]^G1_register[0];
|
|
feedback2 = (G2_register[8] + G2_register[7] + G2_register[4] + G2_register[2] + G2_register[1] + G2_register[0]) & 0x1;
|
|
|
|
for(lcv2 = 0; lcv2 < 9; lcv2++)
|
|
{
|
|
G1_register[lcv2] = G1_register[lcv2+1];
|
|
G2_register[lcv2] = G2_register[lcv2+1];
|
|
}
|
|
|
|
G1_register[9] = feedback1;
|
|
G2_register[9] = feedback2;
|
|
}
|
|
|
|
/* Set the delay */
|
|
delay = 1023 - delays[prn];
|
|
|
|
/* Generate PRN from G1 and G2 Registers */
|
|
for(lcv = 0; lcv < 1023; lcv++)
|
|
{
|
|
_dest[lcv].i = G1[lcv]^G2[delay];
|
|
_dest[lcv].q = 0;
|
|
|
|
delay++;
|
|
delay %= 1023;
|
|
}
|
|
|
|
return(1);
|
|
|
|
}
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
|
|
|
|
/*!
|
|
* code_gen_complex_sampled, generate GPS L1 C/A code complex for the desired SV ID and sampled to specific sampling frequency
|
|
*/
|
|
void code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, int32 _fs, unsigned int _chip_shift)
|
|
{
|
|
// This function is based on the GNU software GPS for MATLAB in the Kay Borre book
|
|
std::complex<float> _code[1023];
|
|
int32 _samplesPerCode,_codeValueIndex;
|
|
float _ts;
|
|
float _tc;
|
|
const int32 _codeFreqBasis=1023000; //Hz
|
|
const int32 _codeLength=1023;
|
|
|
|
//--- Find number of samples per spreading code ----------------------------
|
|
_samplesPerCode = round(_fs / (_codeFreqBasis / _codeLength));
|
|
|
|
//--- Find time constants --------------------------------------------------
|
|
_ts = 1/(float)_fs; // Sampling period in sec
|
|
_tc = 1/(float)_codeFreqBasis; // C/A chip period in sec
|
|
code_gen_conplex(_code,_prn,_chip_shift); //generate C/A code 1 sample per chip
|
|
//std::cout<<"ts="<<_ts<<std::endl;
|
|
//std::cout<<"tc="<<_tc<<std::endl;
|
|
//std::cout<<"sv="<<_prn<<std::endl;
|
|
for (int32 i=0;i<_samplesPerCode;i++)
|
|
{
|
|
//=== Digitizing =======================================================
|
|
|
|
//--- Make index array to read C/A code values -------------------------
|
|
// The length of the index array depends on the sampling frequency -
|
|
// number of samples per millisecond (because one C/A code period is one
|
|
// millisecond).
|
|
|
|
|
|
_codeValueIndex = ceil((_ts * ((float)i+1)) / _tc)-1;
|
|
|
|
//--- Make the digitized version of the C/A code -----------------------
|
|
// The "upsampled" code is made by selecting values form the CA code
|
|
// chip array (caCode) for the time instances of each sample.
|
|
if (i==_samplesPerCode-1){
|
|
//--- Correct the last index (due to number rounding issues) -----------
|
|
_dest[i] = _code[_codeLength-1];
|
|
|
|
}else{
|
|
_dest[i] = _code[_codeValueIndex]; //repeat the chip -> upsample
|
|
}
|
|
//std::cout<<_codeValueIndex;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
/*!
|
|
* sine_gen, generate a full scale sinusoid of frequency f with sampling frequency fs for _samps samps and put it into _dest
|
|
* */
|
|
void sine_gen(CPX *_dest, double _f, double _fs, signed int _samps) {
|
|
|
|
signed int lcv;
|
|
signed short c, s;
|
|
float phase, phase_step;
|
|
|
|
phase = 0;
|
|
phase_step = (float)TWO_PI*_f/_fs;
|
|
|
|
for(lcv = 0; lcv < _samps; lcv++) {
|
|
c = (signed short)floor(16383.0*cos(phase));
|
|
s = (signed short)floor(16383.0*sin(phase));
|
|
_dest[lcv].i = c;
|
|
_dest[lcv].q = s;
|
|
|
|
phase += phase_step;
|
|
}
|
|
}
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
void sine_gen_complex(std::complex<float>* _dest, double _f, double _fs, unsigned int _samps) {
|
|
|
|
double phase, phase_step;
|
|
|
|
phase_step = ((double)TWO_PI*_f)/_fs;
|
|
|
|
for(unsigned int i = 0; i < _samps; i++) {
|
|
|
|
//_dest[i] = std::complex<float>(16383.0*cos(phase), 16383.0*sin(phase));
|
|
_dest[i] = std::complex<float>(cos(phase),sin(phase));
|
|
|
|
phase += phase_step;
|
|
}
|
|
|
|
}
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
void sine_gen(CPX *_dest, double _f, double _fs, int32 _samps, double _p)
|
|
{
|
|
|
|
int32 lcv;
|
|
int16 c, s;
|
|
double phase, phase_step;
|
|
|
|
phase = _p;
|
|
phase_step = (double)TWO_PI*_f/_fs;
|
|
|
|
for(lcv = 0; lcv < _samps; lcv++)
|
|
{
|
|
c = (int16)floor(16383.0*cos(phase));
|
|
s = (int16)floor(16383.0*sin(phase));
|
|
_dest[lcv].i = c;
|
|
_dest[lcv].q = s;
|
|
|
|
phase += phase_step;
|
|
}
|
|
|
|
}
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
/*!
|
|
* wipeoff_gen, generate a full scale sinusoid of frequency f with sampling frequency fs for _samps samps and put it into _dest
|
|
* */
|
|
void wipeoff_gen(MIX *_dest, double _f, double _fs, int32 _samps)
|
|
{
|
|
|
|
int32 lcv;
|
|
int16 c, s;
|
|
double phase, phase_step;
|
|
|
|
phase = 0;
|
|
phase_step = (double)TWO_PI*_f/_fs;
|
|
|
|
for(lcv = 0; lcv < _samps; lcv++)
|
|
{
|
|
c = (int16)floor(16383.0*cos(phase));
|
|
s = (int16)floor(16383.0*sin(phase));
|
|
_dest[lcv].i = _dest[lcv].ni = c;
|
|
_dest[lcv].q = s;
|
|
_dest[lcv].nq = -s;
|
|
|
|
phase += phase_step;
|
|
}
|
|
|
|
}
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
void downsample(CPX *_dest, CPX *_source, double _fdest, double _fsource, int32 _samps)
|
|
{
|
|
|
|
int32 lcv, k;
|
|
uint32 phase_step;
|
|
uint32 lphase, phase;
|
|
|
|
phase_step = (uint32)floor((double)4294967296.0*_fdest/_fsource);
|
|
|
|
k = lphase = phase = 0;
|
|
|
|
for(lcv = 0; lcv < _samps; lcv++)
|
|
{
|
|
if(phase <= lphase)
|
|
{
|
|
_dest[k] = _source[lcv];
|
|
k++;
|
|
}
|
|
|
|
lphase = phase;
|
|
phase += phase_step;
|
|
}
|
|
|
|
}
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
/*!
|
|
* Gather statistics and run AGC
|
|
* */
|
|
int32 run_agc(CPX *_buff, int32 _samps, int32 _bits, int32 _scale)
|
|
{
|
|
int32 lcv, num;
|
|
int16 max, *p;
|
|
int16 val;
|
|
|
|
p = (int16 *)&_buff[0];
|
|
|
|
val = (1 << (_scale - 1));
|
|
max = 1 << _bits;
|
|
num = 0;
|
|
|
|
if(_scale)
|
|
{
|
|
for(lcv = 0; lcv < 2*_samps; lcv++)
|
|
{
|
|
p[lcv] += val;
|
|
p[lcv] >>= _scale;
|
|
if(abs(p[lcv]) > max)
|
|
num++;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
for(lcv = 0; lcv < 2*_samps; lcv++)
|
|
{
|
|
if(abs(p[lcv]) > max)
|
|
num++;
|
|
}
|
|
}
|
|
|
|
return(num);
|
|
|
|
}
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
|
|
|
|
/*----------------------------------------------------------------------------------------------*/
|
|
/*!
|
|
* Get a rough first guess of scale value to quickly initialize agc
|
|
* */
|
|
void init_agc(CPX *_buff, int32 _samps, int32 bits, int32 *scale)
|
|
{
|
|
int32 lcv;
|
|
int16 *p;
|
|
int32 max;
|
|
|
|
p = (int16 *)&_buff[0];
|
|
|
|
max = 0;
|
|
for(lcv = 0; lcv < 2*_samps; lcv++)
|
|
{
|
|
if(p[lcv] > max)
|
|
max = p[lcv];
|
|
}
|
|
|
|
scale[0] = (1 << 14) / max;
|
|
|
|
}
|
|
/*----------------------------------------------------------------------------------------------*/
|