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GPS overlay system for a geostationary satellite

  • US 5,760,738 A
  • Filed: 09/27/1996
  • Issued: 06/02/1998
  • Est. Priority Date: 09/29/1995
  • Status: Expired due to Term
First Claim
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1. A GPS overlay system for a geostationary satellite in which both a PN code and a carrier are generated in a ground station, the PN code is subjected to data modulation using the PN code spectrum diffusion, a pseudo GPS signal is produced by carrier phase modulation using the diffused PN code so as to be transmitted to a geostationary satellite, and the pseudo GPS signal is retransmitted from said geostationary satellite to the ground, thereby utilizing said geostationary satellite as one of GPS satellites, said system comprising:

  • pseudo GPS signal receiving means for receiving the pseudo GPS signal from said geostationary satellite;

    epoch rough synchronization control means for monitoring the pseudo GPS signal received by said pseudo GPS signal receiving means in order to control the timing of generating the PN code in such a way that when transmitting the pseudo GPS signal, a PN code epoch of the pseudo GPS signal which has been transmitted from said geostationary satellite is substantially synchronized with the ground reference time; and

    epoch accurate synchronization control means for controlling a frequency of the PN code in such a way that after completion of the rough synchronization by said rough synchronization control means, the intermediate time between the PN code epoch when transmitting the pseudo GPS signal from said ground station to said moving geostationary satellite and the PN code epoch when the ground station receives the pseudo GPS signal from said moving geostationary satellite becomes the ground reference time.

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