Float carrier phase for RTK simulation

gpssim.c

@@ -1618,9 +1618,12 @@ int allocateChannel(channel_t *chan, ephem_t *eph, ionoutc_t ionoutc, gpstime_t
 						r_ref = rho.range;
 
 						phase_ini = (2.0*r_ref - r_xyz)/LAMBDA_L1;
+#ifdef FLOAT_CARR_PHASE
+						chan[i].carr_phase = phase_ini - floor(phase_ini);
+#else
 						phase_ini -= floor(phase_ini);
-						chan[i].carr_phase = (unsigned int)(512 * 65536.0 * phase_ini);
-
+						chan[i].carr_phase = (unsigned int)(512.0 * 65536.0 * phase_ini);
+#endif
 						// Done.
 						break;
 					}
@@ -2153,8 +2156,9 @@ int main(int argc, char *argv[])
 
 				// Update code phase and data bit counters
 				computeCodePhase(&chan[i], rho, 0.1);
-				chan[i].carr_phasestep = (int)(512 * 65536.0 * chan[i].f_carr * delt);
-
+#ifndef FLOAT_CARR_PHASE
+				chan[i].carr_phasestep = (int)round(512.0 * 65536.0 * chan[i].f_carr * delt);
+#endif
 				// Path loss
 				path_loss = 20200000.0/rho.d;
 
@@ -2176,8 +2180,11 @@ int main(int argc, char *argv[])
 			{
 				if (chan[i].prn>0)
 				{
-					iTable = (chan[i].carr_phase >> 16) & 511;
-
+#ifdef FLOAT_CARR_PHASE
+					iTable = (int)floor(chan[i].carr_phase*512.0);
+#else
+					iTable = (chan[i].carr_phase >> 16) & 0x1ff; // 9-bit index
+#endif
 					ip = chan[i].dataBit * chan[i].codeCA * cosTable512[iTable] * gain[i];
 					qp = chan[i].dataBit * chan[i].codeCA * sinTable512[iTable] * gain[i];
 
@@ -2218,7 +2225,16 @@ int main(int argc, char *argv[])
 					chan[i].codeCA = chan[i].ca[(int)chan[i].code_phase]*2-1;
 
 					// Update carrier phase
+#ifdef FLOAT_CARR_PHASE
+					chan[i].carr_phase += chan[i].f_carr * delt;
+
+					if (chan[i].carr_phase >= 1.0)
+						chan[i].carr_phase -= 1.0;
+					else if (chan[i].carr_phase<0.0)
+						chan[i].carr_phase += 1.0;
+#else
 					chan[i].carr_phase += chan[i].carr_phasestep;
+#endif
 				}
 			}
 

gpssim.h

@@ -1,6 +1,8 @@
 #ifndef GPSSIM_H
 #define GPSSIM_H
 
+#define FLOAT_CARR_PHASE // For RKT simulation. Higher computational load, but smoother carrier phase.
+
 #define TRUE	(1)
 #define FALSE	(0)
 
@@ -159,8 +161,12 @@ typedef struct
 	int ca[CA_SEQ_LEN]; /*< C/A Sequence */
 	double f_carr;	/*< Carrier frequency */
 	double f_code;	/*< Code frequency */
+#ifdef FLOAT_CARR_PHASE
+	double carr_phase;
+#else
 	unsigned int carr_phase; /*< Carrier phase */
 	int carr_phasestep;	/*< Carrier phasestep */
+#endif
 	double code_phase; /*< Code phase */
 	gpstime_t g0;	/*!< GPS time at start */
 	unsigned long sbf[5][N_DWRD_SBF]; /*!< current subframe */