GPS system and method for deriving pointing or attitude from a single GPS receiver
First Claim
1. A GPS pointing and attitude measurement system using a single GPS receiver and multiple antennas to derive pointing and attitude measurement using a selected PRN code recovered from GPS navigation signals, wherein azimuth and elevation are determined in pointing application and roll, pitch, and yaw are determined in attitude application, comprising:
- a reference and at least one slave antenna mounted to a foundation, such that the separation is significantly less than the correlation interval for the selected PRN code;
reference and, for each slave antenna, slave precorrelation electronics for providing respective digital representations of the GPS signals received by said reference and slave antennas;
at least one replica carrier generator for generating a replica of the GPS carrier signal;
at least one replica code generator for generating a replica of the selected GPS PRN code signal;
reference correlation electronics, including a carrier mixer and a selected number of code correlators, responsive to the reference GPS signal, and to replica carrier and replica code signals, for generating reference I and Q correlation outputs;
for each slave antenna, slave correlation electronics including a carrier mixer and at least one code correlator responsive to the slave GPS signals, and to replica carrier and replica code signals, for generating slave I and Q correlation outputs; and
a GPS processor responsive to the reference I and Q correlation outputs for tracking with the reference antenna, and responsive to the reference and slave I and Q correlation outputs for computing pointing and attitude measurements.
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Accused Products
Abstract
A GPS single-receiver pointing/attitude system derives pointing/attitude measurements by correlating a selected GPS code (either P or C/A), recovered from GPS navigation signals using a single GPS receiver with multiple GPS antennas (a reference antenna and at least two slave antennas for pointing or three for attitude). For a two antenna pointing application, the GPS receiver (FIG. 4) includes, for each receiver channel, the incoming GPS signals are applied to three code correlators (72-75) assigned to the reference antenna, and three code correlators (76-77) assigned to the slave antenna, which provide corresponding reference and slave I and Q correlation outputs. The single-receiver pointing technique involves: (a) using the reference I and Q correlation outputs to establish a conventional reference antenna tracking loop; and (b) processing the reference and slave I and Q correlation outputs (using differential carrier doppler phase or code phase measurements) to determine phase differences from which pointing can be computed.
251 Citations
40 Claims
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1. A GPS pointing and attitude measurement system using a single GPS receiver and multiple antennas to derive pointing and attitude measurement using a selected PRN code recovered from GPS navigation signals, wherein azimuth and elevation are determined in pointing application and roll, pitch, and yaw are determined in attitude application, comprising:
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a reference and at least one slave antenna mounted to a foundation, such that the separation is significantly less than the correlation interval for the selected PRN code; reference and, for each slave antenna, slave precorrelation electronics for providing respective digital representations of the GPS signals received by said reference and slave antennas; at least one replica carrier generator for generating a replica of the GPS carrier signal; at least one replica code generator for generating a replica of the selected GPS PRN code signal; reference correlation electronics, including a carrier mixer and a selected number of code correlators, responsive to the reference GPS signal, and to replica carrier and replica code signals, for generating reference I and Q correlation outputs; for each slave antenna, slave correlation electronics including a carrier mixer and at least one code correlator responsive to the slave GPS signals, and to replica carrier and replica code signals, for generating slave I and Q correlation outputs; and a GPS processor responsive to the reference I and Q correlation outputs for tracking with the reference antenna, and responsive to the reference and slave I and Q correlation outputs for computing pointing and attitude measurements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 27)
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12. The GPS single-receiver pointing and attitude system of claim wherein the differential code phase measurements are computed according to the relationship:
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space="preserve" listing-type="equation">(RLE-REE-SLE+SEE)/(RLE+REE+SLE+SEE)where REE=SQRT (IRE2 +QRE2) RLE=SQRT (IRL2 +QRL2) SEE=SQRT (ISE2 +QSE2) SLE=SQRT (ISL2 +QSL2) and where IRE2 /QRE2 are in-phase and quadrature reference Early correlation outputs, IRL2 /QRL2 are in-phase and quadrature reference late correlation outputs, ISE2 /QSE2 are in-phase and quadrature slave Early correlation outputs, and ISL2 /QSL2 are in-phase and quadrature slave Late correlation outputs.
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25. A GPS pointing and attitude measurement method using a single GPS receiver and multiple antennas to derive pointing and attitude measurements using a selected PRN code recovered from GPS navigation signals, wherein azimuth and elevation are determined in pointing applications and roll, pitch and yaw are determined in attitude applications, comprising the steps:
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mounting a reference and at least one slave antenna mounted to a foundation, such that the separation is significantly less than the correlation interval for the selected PRN code; for the reference antenna, establishing a reference antenna tracking loop to generate reference I and Q correlation outputs using a set of reference code correlators and the selected PRN code signals; for each slave antenna, generating slave I and Q correlation outputs using at lest one slave code correlator and the selected PRN code signals; and processing the reference and slave I and Q correlation outputs to compute pointing and attitude measurements. - View Dependent Claims (26, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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Specification