No-outage GPS/commercial RF positioning system

  • US 5,422,813 A
  • Filed: 09/02/1993
  • Issued: 06/06/1995
  • Est. Priority Date: 12/17/1992
  • Status: Expired due to Term
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First Claim
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1. In a GPS system wherein a plurality of satellites transmit time and location data over radio frequency signals to enable a mobile GPS receiver station on the ground to determine its position and produce a GPS position signal, and a cellular telephone carried with said mobile GPS receiver, anda plurality of conventional ground based amplitude modulated (AM) transmitters for broadcasting AM signals, the improvement comprising:

  • 1) each mobile GPS receiver station including phase detection means for simultaneously receiving a predetermined number of said AM signals, and measuring the changes in phase of each of said AM signals as said mobile GPS receiver travels, and deriving therefrom an AM position signal,2) a reference station for receiving said GPS and AM signals and providing correction signals and transmitting said correction signals by said cellular telephone to said mobile receiver station, and3) means for using said GPS position signal for resolving any ambiguities in said AM radio position signal and to accommodate the lack of synchronization in said AM transmitters.

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