DGPS Servers

GPS Receivers

It is well known that GPS can be used as a source of highly accurate synchronisation and time transfer. The ability of the GPS system to achieve this is down to the fact that the GPS satellites themselves are synchronised with on-board Caesium or Rubidium atomic clocks that are in turn synchronised to GPS time (GPS time has a direct relationship to UTC).In this way, it means that the GPS satellites are all phase coherent that allows the GPS system to be used as method of highly accurate synchronisation for systems that can be on opposite sides of the globe. Similarly, highly accurate time transfer can be achieved with the GPS system.

There are various forms of GPS based equipment on the market designed for synchronisation, but NavSync has a unique GPS receiver platform that allows the direct generation of a GPS steered output frequency and 1pps signal, with the ability of the receiver to maintain GPS lock even in extremely poor signal strength areas. This unique ability allows the GPS antenna used in the system to be sited in far more convenient locations (even inside buildings) with reduced cabling requirements and often the removal of any lightning strike protection.

In order for a GPS receiver to acquire and track satellite signals, it must perform a two dimensional signal replication process of the received satellite signals. This two dimensional process consists first of a search for the phase of the desired satellite signal, and then a search for the carrier frequency plus Doppler of the satellite. This becomes even more evident as the received satellite signals reduce in strength, and with limited numbers of correlators the receiver sensitivity is rarely very much below –140 to –145dBm

In normal GPS receivers, when a positional computation is required the receiver needs to have the following data available in order to gain a rapid fix;

• An up to date almanac
• Rough estimates of receiver location and velocity
• An estimate of GPS time
• Valid satellite ephemeris for satellites in view
• NavSync GPS products are based on architectures designed specifically to allow the acquisition and tracking of satellites under very harsh conditions with very low signal strengths such as indoor applications.

A number of different versions of these GPS Timing and Navigational receivers are available to suit different applications:

• GPS Timing Solutions
• GPS Navigation Solutions
• Integrated GPS Modules
• Parthus Legacy GPS Products