ntp-92/ntpd/refclock_wwv.c

120  * on signal loss. SSYNC is set when the second sync pulse has been
122  * sync pulse has been acquired. DSYNC is set when the units digit has
131  * and the minute sync slips a second.
133 #define MSYNC		0x0001	/* minute epoch sync */
134 #define SSYNC		0x0002	/* second epoch sync */
135 #define DSYNC		0x0004	/* minute units sync */
161 #define SYNERR		0x8	/* not tracking second sync */
172 #define SYNCH		40	/* station sync timeout */
181 #define MTHR		13.	/* minute sync gate (percent) */
182 #define TTHR		50.	/* minute sync threshold (percent) */
183 #define AWND		20	/* minute sync jitter threshold (ms) */
184 #define ATHR		2500.	/* QRZ minute sync threshold */
185 #define ASNR		20.	/* QRZ minute sync SNR threshold (dB) */
186 #define QTHR		2500.	/* QSY minute sync threshold */
187 #define QSNR		20.	/* QSY minute sync SNR threshold (dB) */
188 #define STHR		2500.	/* second sync threshold */
189 #define	SSNR		15.	/* second sync SNR threshold (dB) */
190 #define SCMP		10 	/* second sync compare threshold */
303 #define SYNC2		13	/* latch minute sync pulse */
315 	{SYNC2,	0},		/* 0 latch minute sync pulse */
477  * used for the second and minute sync pulses, 1000 Hz for WWV and 1200
480 struct sync {
482 	double	maxeng;		/* sync max energy */
483 	double	noieng;		/* sync noise energy */
488 	double	amp;		/* sync signal */
489 	double	syneng;		/* sync signal max */
490 	double	synmax;		/* sync signal max latched at 0 s */
491 	double	synsnr;		/* sync signal SNR */
504 	struct sync wwv;	/* wwv station */
505 	struct sync wwvh;	/* wwvh station */
536 	int	yepoch;		/* sync epoch */
537 	int	repoch;		/* buffered sync epoch */
538 	double	epomax;		/* second sync amplitude */
539 	double	eposnr;		/* second sync SNR */
551 	struct sync *sptr;	/* station pointer */
594 static	void	wwv_qrz		(struct peer *, struct sync *, int);
604 static	double	wwv_metric	(struct sync *);
906  * counts the samples starting at the 5-ms second sync pulse found
912  * the minute starting at the 800-ms minute sync pulse found during the
917  * sinusoids: 100 Hz for the data signal, 1000 Hz for the WWV sync
918  * signal and 1200 Hz for the WWVH sync signal. These drive synchronous
920  * sync signal (800 ms at 1000 Hz) and WWVH minute sync signal (800 ms
922  * as required for the WWV second sync signal (5 cycles at 1000 Hz) and
923  * WWVH second sync signal (6 cycles at 1200 Hz).
933 	struct sync *sp, *rp;
946 	static int jptr;	/* sync channel pointer */
971 	static double epobuf[SECOND]; /* second sync comb filter */
972 	static double epomax, nxtmax; /* second sync amplitude buffer */
973 	static int epopos;	/* epoch second sync position buffer */
1004 	 * the 1000/1200-Hz sync signals, as well as the 440-Hz and
1051 	 * Baseband sync demodulation. The 1000/1200 sync signals are
1079 	 * The 1000/1200 sync signals are demodulated using a pair of
1083 	 * sync signals are produced by multiplying the filtered signal
1087 	 * minute sync signal and detect which one (or both) the WWV or
1090 	 * produce the second sync signal. The signals are scaled to
1168 			 * If minute sync has not been acquired before
1195 	 * sync epoch is zero. Watch out for the first second; if
1196 	 * already synchronized to the second, the buffered sync epoch
1224 	 * The second sync pulse is extracted using 5-ms (40 sample) FIR
1240 	 * Enhance the seconds sync pulse using a 1-s (8000-sample) comb
1243 	 * propagation delay. Once each second look for second sync. If
1244 	 * not in minute sync, fiddle the codec gain. Note the SNR is
1279  * wwv_qrz - identify and acquire WWV/WWVH minute sync pulse
1282  * minute sync and to mitigate among the ten frequency and station
1283  * combinations. During minute sync acquisition the process probes each
1301 	struct sync *sp,	/* sync channel structure */
1329 	 * sync pulse, as well as the difference between the current and
1375  * wwv_endpoc - identify and acquire second sync pulse
1377  * This routine is called at the end of the second sync interval. It
1378  * determines the second sync epoch position within the second and
1381  * Second sync is determined in the RF input routine as the maximum
1420 	 * second sync lamp and wait for hotter ions. If no stations are
1435 	 * second sync pulse. The median sample becomes the candidate
1604  * minute sync pulse detected in the wwv_rf() routine and the second
1605  * sync pulse detected in the wwv_epoch() routine. The transmitted
1612  * sync pulses. Therefore, the data subcarrier reference phase is
1631 	 * Find the maximum minute sync pulse energy for both the
1761 	struct sync *sp, *rp;
1804 	 * sync pulse is contained in second 0. At the end of second 58
1807 	 * sync pulse. At the end of second 1 measure the data pulse and
1811 	 * At the end of second 0 save the minute sync amplitude latched
1821 	 * At the end of second 1 use the minute sync amplitude latched
1823 	 * sync pulse and SNR are above thresholds and the data pulse
2009 	 * the timescale and the minute sync repeats the second. Once
2043  * the time is considered valid if the second sync bit is lit. It should
2047  * loss, the minute sync epoch will be in the same second. This requires
2374  * probe frequency in order to search for minute sync pulse and data
2378  * sync pulse at 1000 Hz and WWVH at 1200 Hz. The probe frequency
2386  * of ties, the award goes to the channel with the highest minute sync
2392  * bits are cleared so the second sync is disabled and the data bit
2402 	struct sync *sp, *rp;
2435 	 * we are beneath the waves, so squelch the second sync and
2483  *	(SYNCH) without finding station sync (INSYNC lit).
2485  * 3	After finding station sync (INSYNC lit), going more than 2 days
2538  * the minute sync pulse amplitude. The combined value is scaled 0-100.
2542 	struct sync *sp		/* station pointer */
2596  * s	sync indicator ('?' or ' ')
2620 	struct sync *sp;