GPS overlay system for a geostationary satellite
First Claim
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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Accused Products
Abstract
Whether or not a pseudo GPS signal is normally received is monitored from the data state in a reception unit. Then, at the stage when the pseudo GPS signal can be normally received, the satellite output timing is substantially synchronized with the ground reference time while the control is carried out so as to advance/delay the timing of outputting a transmission PN code in correspondence to the moving direction of a satellite. Subsequently, a time period ranging from a time point when transmitting the pseudo GPS signal to a time period when receiving the pseudo GPS signal which has been returned via the satellite is observed, while the control is carried out so as to increase/decrease continuously a frequency of the transmission PN code, in such a way that the intermediate time therebetween becomes the reference time. Next, the frequency of the transmission carrier is controlled in correspondence to the control of increasing/decreasing the frequency of the transmission PN code, while the epoch pull out and the reception interruption are monitored, so as to maintain the relationship in which the frequency of the received carrier is 1,540 times as high as that of the received reception PN code frequency. By executing the above-mentioned processings, it is possible to cancel the transponder frequency error of the geostationary satellite site as well as the Doppler component added in the uplink.
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Citations
4 Claims
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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:
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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. - View Dependent Claims (2, 3, 4)
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Specification