Abstract: A time reference system for generating a time reference from signals produced by a global navigation satellite constellation has a satellite signal receiver to receive and down-convert code-modulated signals from a plurality of satellites and a correlator to track and decode the down-converted signals to provide signals containing partial pseudo-range measurements for respective satellites. A data processing arrangement receives assistance data from an external source and performs data-bit synchronization in which bit edges of a low frequency data bit stream carried by the received satellite signals are identified, to perform a preliminary position-velocity-time solution to provide an approximate time reference, and to perform auto-correlation of pre-selected data sequences in the data stream to resolve time ambiguities thereby to compute a precise time reference signal in weak received signal conditions.

Abstract: A time reference system for generating a time reference from signals produced by a global navigation satellite constellation has a satellite signal receiver to receive and down-convert code-modulated signals from a plurality of satellites and a correlator to track and decode the down-converted signals to provide signals containing partial pseudo-range measurements for respective satellites. A data processing arrangement receives assistance data from an external source and performs data-bit synchronisation in which bit edges of a low frequency data bit stream carried by the received satellite signals are identified, to perform a preliminary position-velocity-time solution to provide an approximate time reference, and to perform auto-correlation of pre-selected data sequences in the data stream to resolve time ambiguities thereby to compute a precise time reference signal in weak received signal conditions.

Abstract: A positioning or timing receiver, for receiving pseudo-noise encoded signals includes mask mixers in the main signal paths, prior to accumulators. The mask mixers are fed with mask signals having a period equal to the period of the pseudo-noise code, provided by a mask generator. The mask generator and mixers provide an extra level of functionality in the receiver, through which a large number of uses can be made. For example, without modifying a code signal mixed into the main signal path, the mask mixers allow dynamic adaptability from a wide correlator to a narrow correlator by simple control of the mask generator. Many different discrimination patterns can be obtained. By changing the mask signals and examining correlator outputs, it is possible to detect whether a signal being tracked contains a multipath component. The receiver also includes a switch, whereby two correlators may be fed with signals from the in-phase main signal path.