Communications systems that reduces auto-correlation or cross-correlation in weak signals
First Claim
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1. A communications system, comprising:
- a Global Positioning System (GPS) receiver, adapted to be coupled to a transceiver capable of using a wireless communications link for transmission and reception of wireless signals, the GPS receiver being usable for at least computing a position of the transceiver, the GPS receiver comprising;
a correlator engine for correlating a plurality of digital samples of an incoming GPS signal within a signal window with a locally generated signal produced by a coder so as to generate a current lock signal;
a processor for verifying whether the current lock signal is a desired GPS signal, where the signal window contains at least 2 milliseconds of the incoming GPS signal, the processor determining whether the signal window of the incoming GPS signal has at least one characteristic which differentiates the incoming GPS signal from an auto-correlated or cross-correlated signal, wherein the GPS receiver can configure the coder to change the locally generated signal used by the correlator engine to search subsequent signal windows of the incoming GPS signal if the current signal window of the incoming GPS signal lacks the at least one characteristic, until a desired lock signal is achieved; and
one or more registers for loading a plurality of uncorrelated digital samples of the incoming GPS signal to be provided to the processor, thereby bypassing the correlator engine.
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Abstract
The present invention discloses methods, apparatuses, and systems for eliminating auto- and cross-correlation in weak signal CDMA systems, such as GPS systems. The invention uses parallel data paths that allow standard correlation of signals in parallel with verification of the lock signal to determine whether the system has locked onto the proper signal within the scanned signal window. The invention can be made with multiple CPUs, a single CPU with dual input modes, on multiple IC chips, or as a single IC chip solution for small, low cost reception, downconversion, correlation, and verification systems.
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Citations
19 Claims
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1. A communications system, comprising:
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a Global Positioning System (GPS) receiver, adapted to be coupled to a transceiver capable of using a wireless communications link for transmission and reception of wireless signals, the GPS receiver being usable for at least computing a position of the transceiver, the GPS receiver comprising; a correlator engine for correlating a plurality of digital samples of an incoming GPS signal within a signal window with a locally generated signal produced by a coder so as to generate a current lock signal; a processor for verifying whether the current lock signal is a desired GPS signal, where the signal window contains at least 2 milliseconds of the incoming GPS signal, the processor determining whether the signal window of the incoming GPS signal has at least one characteristic which differentiates the incoming GPS signal from an auto-correlated or cross-correlated signal, wherein the GPS receiver can configure the coder to change the locally generated signal used by the correlator engine to search subsequent signal windows of the incoming GPS signal if the current signal window of the incoming GPS signal lacks the at least one characteristic, until a desired lock signal is achieved; and one or more registers for loading a plurality of uncorrelated digital samples of the incoming GPS signal to be provided to the processor, thereby bypassing the correlator engine. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A Global Positioning System (GPS) receiver, comprising:
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a downconverter for converting an incoming GPS signal to a baseband signal; a sampler that generates digital samples of the downconverted incoming GPS signal; a correlator engine for correlating a plurality of the digital samples of the incoming GPS signal within a signal window with a locally generated signal produced by a coder so as to generate a current lock signal; a processor for verifying whether the current lock signal is a desired GPS signal, where the signal window contains at least 2 milliseconds of the incoming GPS signal, the processor determining whether the signal window of the incoming GPS signal has at least one characteristic which differentiates the incoming GPS signal from an auto-correlated or cross-correlated signal, wherein the GPS receiver can configure the coder to change the locally generated signal used by the correlator engine to search subsequent signal windows of the incoming GPS signal if the current signal window of the incoming GPS signal lacks the at least one characteristic, until a desired lock signal is achieved; and one or more registers for loading a plurality of uncorrelated digital samples of the incoming GPS signal to be provided to the processor, thereby bypassing the correlator engine.
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Specification