Dual Frequency global positioning system
First Claim
1. A global position sensing receiver for receiving over L1 and L2 bands, respectively, L1 signals that are modulated both by a C/A-code and a P-code that is, at times, encrypted and L2 signals that are modulated by the P-code that is, at times, encrypted, the receiver including:
- A. means for producing a locally-generated version of the C/A-code that is aligned with the C/A-code in the received L1 signal;
B. an L1 P-code generator for producing a locally-generated version of the P-code that is phase-locked to the locally-generated version of the C/A-code;
C. an L2 carrier angle estimation means for producing an estimate of the phase angle of an L2 carrier;
D. an L2 P-code generator for producing a locally-generated version of the P-code;
E. a controller for controlling the operations of the L2 P-code generator, the controller receiving signals associated with a correlation between the locally-generated P-code and the received L2 signals, and adjusting the L2 P-code generator to align the locally-generated P-code with the L2 signals; and
F. a detector for resolving a 1/2-cycle ambiguity in tracking the L2 P-code, the detector including;
i. a majority vote circuit for determining if a majority of bits of the received L2 P-code match or do not match corresponding bits of the received L1 P-code, andii. means for adjusting the carrier angle estimation means if the majority vote circuit determines that a majority of the L1 and L2 bits do not match.
2 Assignments
0 Petitions
Accused Products
Abstract
A global position system receiver recovers the L1 and L2 carriers, the C/A-code measurements and the L1 and L2 P-code measurements by (a) producing an estimate of the L1 carrier phase angle and synchronizing a locally generated C/A-code with the L1 signal using an L1 delay lock loop and controlling, based on the locally generated C/A code, an L1 P-code generator that produces a synchronized version of the P-code; (b) initializing an L2 P-code generator based on the phase of the P-code generated by the L1 P-code generator; (c) determining, for the L2 signal, an estimate of signal power that is adjusted to compensate for noise; (d) determining an L2 carrier phase angle; (e) tracking the L2 P-code by adjusting an L2 P-code generator until the estimate of signal power is maximized. The GPS receiver also resolves a 1/2 cycle ambiguity in tracking the L2 P-code by comparing demodulated L1 P-code bits and L2 P-code bits. If the bits do not match in the majority of instances, the receiver determines that it is tracking the L2 P-code with 1/2 cycle error and adjusts its estimate of the P-code phase accordingly. The receiver may determine the reliability of the independently tracked L2 signal, by determining an associated carrier-to-noise ratio.
62 Citations
20 Claims
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1. A global position sensing receiver for receiving over L1 and L2 bands, respectively, L1 signals that are modulated both by a C/A-code and a P-code that is, at times, encrypted and L2 signals that are modulated by the P-code that is, at times, encrypted, the receiver including:
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A. means for producing a locally-generated version of the C/A-code that is aligned with the C/A-code in the received L1 signal; B. an L1 P-code generator for producing a locally-generated version of the P-code that is phase-locked to the locally-generated version of the C/A-code; C. an L2 carrier angle estimation means for producing an estimate of the phase angle of an L2 carrier; D. an L2 P-code generator for producing a locally-generated version of the P-code; E. a controller for controlling the operations of the L2 P-code generator, the controller receiving signals associated with a correlation between the locally-generated P-code and the received L2 signals, and adjusting the L2 P-code generator to align the locally-generated P-code with the L2 signals; and F. a detector for resolving a 1/2-cycle ambiguity in tracking the L2 P-code, the detector including; i. a majority vote circuit for determining if a majority of bits of the received L2 P-code match or do not match corresponding bits of the received L1 P-code, and ii. means for adjusting the carrier angle estimation means if the majority vote circuit determines that a majority of the L1 and L2 bits do not match. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A global position sensing receiver for receiving over L1 and L2 bands, respectively, L1 signals that are modulated both by a C/A-code and a P-code that is, at times, encrypted, and L2 signals that are modulated by the P-code that is, at times, encrypted, the receiver including:
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A. means for producing a locally-generated version of the C/A-code that is aligned with the C/A-code in the received L1 signal; B. an L1 P-code generator for producing a locally-generated version of the P-code that is phase-locked to the locally-generated version of the C/A-code; C. an L2 P-code generator for producing a locally-generated version of the P-code; D. correlation means for determining how closely the P-code produced by the L2 P-code generator and the P-code in the L2 signal are aligned, said means producing L2 correlation signals; E. L2 carrier angle estimation means for providing an estimate of a carrier phase angle based on the correlation signals produced by the correlation means; and F. a controller for controlling the operations of the L2 P-code generator and the L2 carrier angle estimation means, the controller receiving signals from the correlation means and the L2 Carrier angle estimate means, and adjusting the L2 P-code generator, to align the locally-generated P-code with the L2 signals, and adjusting the L2 carrier angle estimation means to phase lock said means to the L2 signal, the controller determining a carrier phase error estimate as;
##EQU4## where K1 and K2 are constants, I and Q are inphase and quadrature correlation signals, "sign I" represents the sign of the I signal, and ST is an estimate of total signal power, the controller using the error estimate to adjust the L2 carrier angle estimation means. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A global position sensing receiver for receiving over L1 and L2 bands, respectively, L1 signals that are modulated both by a C/A-code and a P-code that is, at times, encrypted, and L2 signals that are modulated by the P-code that is, at times, encrypted, the receiver including:
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A. means for producing a locally-generated version of the C/A-code that is aligned with the C/A-code in the received L1 signal; B. an L1 P-code generator for producing a locally-generated version of the P-code that is phase-locked to the locally-generated version of the C/A-code; C. an L2 P-code generator for producing a locally-generated version of the P-code; D. correlation means for determining how closely the P-code produced by the L2 P-code generator and the P-code in the L2 signal are aligned, said means producing L2 correlation signals; E. L2 carrier angle estimation means for providing an estimate of a carrier phase angle based on the correlation signals produced by the correlation means; and F. a controller for controlling the operations of the L2 P-code generator and the L2 carrier angle estimation means, the controller receiving signals from the correlation means and the L2 carrier angle estimate means, and adjusting the L2 P-code generator, to align the locally-generated P-code with the L2 signals, and adjusting the L2 carrier angle estimation means to phase lock said means to the L2 signal, the controller determining a carrier phase error estimate based on an estimate of total signal power, ST, which is determined as a sum of a. signal power in an inphase path minus inphase noise components, and b. signal power in a quadrature path minus quadrature noise components, the controller using the error estimate to adjust the L2 carrier angle estimation means. - View Dependent Claims (17, 18, 19, 20)
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Specification