Receiver having a memory based search for fast acquisition of a spread spectrum signal
First Claim
1. A receiver, comprising:
- a signal memory for storing a digitized representation of a certain time period of an incoming signal;
a replica memory for storing several digitized replicas representative of several desired signals, respectively, in said incoming signal;
a memory comparator coupled to the signal memory and the replica memory for comparing the same said stored digitized representation of said certain time period of said incoming signal to said replicas and issuing an acquisition detection signal when said stored digitized representation of said incoming signal matches a particular one of said replicas; and
a microprocessor system coupled to the replica memory and the memory comparator for receiving said acquisition detection signal and providing control information associated with said particular replica for adjusting a local reference frequency and a local reference time according to said particular replica for acquiring one of said desired signals.
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Accused Products
Abstract
A GPS receiver having a fast time to lock to a GPS signal by storing a time period of an incoming GPS signal in a signal memory and rapidly comparing the signal memory against locations in a replica memory having stored GPS signal replicas. The GPS receiver includes a memory-based search engine for acquiring the GPS signal so that it may be tracked. The memory-based search engine includes a signal memory for storing a millisecond of a digitized GPS signal, a replica memory section for storing replicas representative of the digitized GPS signal for all possible frequency differences between the GPS carrier frequency and a local reference frequency and phase offsets between the GPS code phase and a local reference time, and a GPS memory comparator for comparing the stored signal in signal memory to the stored replicas in replica memory and issuing an acquisition detection signal when the level of the comparison is greater than a selected threshold.
49 Citations
15 Claims
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1. A receiver, comprising:
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a signal memory for storing a digitized representation of a certain time period of an incoming signal; a replica memory for storing several digitized replicas representative of several desired signals, respectively, in said incoming signal; a memory comparator coupled to the signal memory and the replica memory for comparing the same said stored digitized representation of said certain time period of said incoming signal to said replicas and issuing an acquisition detection signal when said stored digitized representation of said incoming signal matches a particular one of said replicas; and a microprocessor system coupled to the replica memory and the memory comparator for receiving said acquisition detection signal and providing control information associated with said particular replica for adjusting a local reference frequency and a local reference time according to said particular replica for acquiring one of said desired signals. - View Dependent Claims (7)
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2. A receiver, comprising:
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a signal memory for storing a digitized representation of a certain time period of an incoming signal; a replica memory for storing several digitized replicas representative of several desired signals, respectively, in said incoming signal; a memory comparator coupled to the signal memory and the replica memory for comparing the same said stored digitized representation of said certain time period of said incoming signal to said replicas and issuing an acquisition detection signal when said stored digitized representation of said incoming signal matches a particular one of said replicas; and
wherein;said stored digitized representation of said incoming signal includes a code having a signal code phase offset; and said several replicas include said code with several replica code phase offsets. - View Dependent Claims (3, 6)
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4. A receiver, comprising:
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a signal memory for storing a digitized representation of a certain time period of an incoming signal; a replica memory for storing several digitized replicas representative of several desired signals, respectively, in said incoming signal; a memory comparator coupled to the signal memory and the replica memory for comparing the same said stored digitized representation of said certain time period of said incoming signal to said replicas and issuing an acquisition detection signal when said stored digitized representation of said incoming signal matches a particular one of said replicas; and
wherein;said desired signals are spread spectrum signals.
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5. A receiver, comprising:
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a signal memory for storing a digitized representation of a certain time period of an incoming signal; a replica memory for storing several digitized replicas representative of several desired signals, respectively, in said incoming signals, respectively; a memory comparator coupled to the signal memory and the replica memory for comparing the same said stored digitized representation of said certain time period of said incoming signal to said replicas and issuing an acquisition detection signal when said stored digitized representation of said incoming signal matches a particular one of said replicas; and
wherein;said desired signals are global positioning system (GPS) signals.
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8. A method for acquiring an incoming signal, comprising steps of:
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receiving said incoming signal at a receiver; digitizing said incoming signal; storing a certain time period of said digitized incoming signal, said stored incoming signal including a signal code having a signal code phase offset; storing several digitized replicas representative of several desired incoming signals, respectively, said several replicas including said code with several replica code phase offsets; comparing the same said certain time period of said stored incoming signal to said replicas; and generating an acquisition detection signal when said stored incoming signal matches a particular one of said replicas. - View Dependent Claims (9)
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10. A method for acquiring an incoming signal, comprising steps of:
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receiving said incoming signal at a receiver; digitizing said incoming signal; storing a certain time period of said digitized incoming signal; storing several digitized replicas representative of several desired incoming signals, respectively, where said desired incoming signals are spread spectrum signals; comparing the same said certain time period of said stored incoming signal to said replicas; and generating an acquisition detection signal when said stored incoming signal matches a particular one of said replicas.
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11. A method for acquiring an incoming signal, comprising steps of:
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receiving said incoming signal at a receiver; digitizing said incoming signal; storing a certain time period of said digitized incoming signal; storing several digitized replicas representative of several desired incoming signals, respectively, where said desired incoming signals are global position system (GPS) signals; comparing the same said certain time period of said stored incoming signal to said replicas; and generating an acquisition detection signal when said stored incoming signal matches a particular one of said replicas. - View Dependent Claims (12, 13)
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14. A receiver for receiving incoming signals, comprising:
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a replica memory for storing several digitized replicas representative of several desired ones of said incoming signals, respectively, said several replicas including a replica code with several replica code phase offsets at several replica carrier frequencies; a signal memory for storing a digitized representation of a certain time period of said incoming signals, said stored digitized representation of said incoming signals including a carrier at a signal carrier frequency modulated by a signal code having a signal code phase offset; and a memory comparator coupled to the signal memory and the replica memory for comparing the same said stored digitized representation of said certain time period of said incoming signals to said replicas and issuing an acquisition detection signal when said stored digitized representation of said incoming signals matches a particular one of said replicas, wherein said particular one of said replicas matches said stored digitized representation of said incoming signal when said replica code matches said signal code, said replica code phase offset matches said signal phase offset, and said replica carrier frequency matches said signal carrier frequency.
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15. A method for acquiring an incoming signal, comprising steps of:
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storing several digitized replicas representative of several desired incoming signals, respectively, said several replicas including a replica code with several replica code phase offsets at several replica carrier frequencies; receiving said incoming signal at a receiver; digitizing said incoming signal; storing a certain time period of said digitized incoming signal, said stored incoming signal including a carrier at a signal carrier frequency modulated by a signal code having a signal code phase offset; comparing the same said certain time period of said stored incoming signal to said replicas; generating an acquisition detection signal when said stored incoming signal matches a particular one of said replicas, and wherein said particular one of said replicas matches said stored incoming signal when said replica code matches said signal code, said replica code phase offset matches said signal phase offset, and said replica carrier frequency matches said signal carrier frequency.
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Specification