Method and apparatus for adaptively processing GPS signals in a GPS receiver
First Claim
1. A method of determining pseudoranges in a global positioning system (GPS) receiver, said method comprising the steps of:
- receiving a plurality of signals from a plurality of in-view GPS satellites;
storing said plurality of signals in a digital snapshot memory to produce stored data;
selecting a first satellite for processing from said plurality of in-view satellites based on a position of said first satellite relative to other satellites of said plurality of in-view GPS satellites;
selecting a first integration time period that determines a portion of said stored data to process;
selecting a first Doppler frequency offset with which to process said portion of said stored data to determine a pseudorange for said first satellite; and
processing said portion of said stored data from said first satellite for said Doppler frequency offset.
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Abstract
A method and apparatus is disclosed for adaptively processing Global Positioning System (GPS) signals in a GPS receiver. An adaptive method of processing GPS signals optimizes the initial acquisition of GPS signals by performing the search using three separate parameters. These parameters include satellite number, Doppler information, and integration time. A block processing method of GPS signal processing is performed for particular in-view satellites over particular time intervals and for each of a set of hypothesized Doppler frequencies. Each parameter is optimized such that the GPS signal acquisition operation for a location fix is performed in a short period of time.
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Citations
44 Claims
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1. A method of determining pseudoranges in a global positioning system (GPS) receiver, said method comprising the steps of:
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receiving a plurality of signals from a plurality of in-view GPS satellites; storing said plurality of signals in a digital snapshot memory to produce stored data; selecting a first satellite for processing from said plurality of in-view satellites based on a position of said first satellite relative to other satellites of said plurality of in-view GPS satellites; selecting a first integration time period that determines a portion of said stored data to process; selecting a first Doppler frequency offset with which to process said portion of said stored data to determine a pseudorange for said first satellite; and processing said portion of said stored data from said first satellite for said Doppler frequency offset. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining pseudoranges in a global positioning system (GPS) receiver, said method comprising the steps of:
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receiving a plurality of GPS signals from a plurality of in-view GPS satellites; storing said plurality of GPS signals in a memory; selecting for processing a first satellite from said plurality of in-view satellites based on a position of said first satellite relative to other satellites of said plurality of in-view GPS satellites, said GPS signals comprising pseudorandom sequences; selecting a first integration time period that determines a portion of data in said memory to process; selecting a first Doppler frequency offset with which to process said portion of data to determine a pseudorange for said first satellite; and computing a pseudorange for said first satellite by performing a plurality of fast convolutions on a corresponding plurality of blocks of data within said portion of data to provide a plurality of corresponding results of each fast convolution and summing a plurality of mathematical representations of said plurality of corresponding results to obtain a first position information. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of determining pseudoranges in a global positioning system (GPS) receiver, said method comprising the steps of:
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receiving GPS signals from a plurality of in-view GPS satellites, said GPS signals comprising pseudorandom sequences; storing said GPS signals in a memory; selecting for processing a first satellite from said plurality of GPS satellites; selecting an integration time period that determines a portion of data in said memory to process; selecting a first Doppler frequency offset with which to process said signals to determine a pseudorange for said first satellite; and computing pseudoranges for said GPS satellites by performing a plurality of fast convolutions on a corresponding plurality of blocks of data within said portion of data to provide a plurality of corresponding results of each fast convolution and summing a plurality of mathematical representations of said plurality of corresponding results to obtain a first position information. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. A GPS receiver apparatus comprising:
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an antenna for receiving GPS signals at an RF frequency from a plurality of in-view satellites; a downconverter coupled to said antenna, said downconverter reducing the RF frequency of said received GPS signals to an intermediate frequency (IF) to produce a baseband signal; a digitizer coupled to said downconverter and receiving said baseband signal, said digitizer sampling said baseband signal at a predetermined rate to produce a sampled baseband signal; a memory coupled to said digitizer, said memory storing a data record of said sampled baseband signal during a predetermined time period; and a digital signal processor (DSP) coupled to said memory, said DSP performing fast convolution operations, wherein said DSP processes a portion of said data record to process a signal from a first satellite of said plurality of in-view satellites by performing a plurality of fast convolution operations on a corresponding plurality of blocks of said portion of said data record to provide a plurality of corresponding results of each fast convolution operation and summing a plurality of mathematical representations of said plurality of corresponding results to obtain a position information, and wherein said DSP is further operable to perform said plurality of fast convolution operations for a first Doppler frequency offset, said first Doppler frequency offset being selected from a plurality of Doppler frequency offsets within a range of Doppler frequency offsets. - View Dependent Claims (27, 28, 29, 30, 31, 32)
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33. A method of determining pseudoranges in a global positioning system (GPS) receiver, said method comprising the steps of:
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receiving a plurality of GPS signals from a plurality of in-view GPS satellites; storing said plurality of GPS signals in a memory; selecting for processing a first satellite from said plurality of in-view satellites based on a position of said first satellite relative to other satellites of said plurality of in-view GPS satellites, said GPS signal comprising pseudorandom sequences; selecting a first integration time period that determines a first portion of data in said memory to process; selecting a first Doppler frequency offset with which to process said first portion of said data to determine a pseudorange for said first satellite; computing a pseudorange for said first satellite by performing a series of fast convolutions on a corresponding plurality of blocks of data within said first portion of data to provide a plurality of corresponding output values of each fast convolution; and comparing each output value of said corresponding output values to a pre-defined noise threshold. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40)
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41. A method of determining pseudoranges in a global positioning system (GPS) receiver, said method comprising:
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receiving a plurality of signals from a plurality of in-view GPS satellites; selecting a first satellite for processing a first signal from said plurality of in-view satellites; selecting a first integration time period; selecting a set of Doppler frequency offsets; processing said first signal over said first integration time period and said set of Doppler frequency offsets to produce a first set of outputs; comparing said first set of outputs with a first detection threshold in order to form a first set of detected outputs, corresponding to any of said first set of outputs that exceed said first detection threshold; associating time indices of said first set of detected outputs with a pseudorange of said first signal and associating amplitudes of said first set of detected outputs with a signal strength of said first signal; selecting a second integration time period, which is longer than the first integration time period, if said first set of detected outputs contains no members; processing said first signal over said second integration time period and said set of Doppler frequency offsets to a produce a second set of outputs; comparing said second set of outputs with a second detection threshold in order to form a second set of detected outputs, corresponding to any of said second set of outputs that exceed said second detection threshold; associating time indices of said second set of detected outputs with a pseudorange of said first signal and associating amplitudes of said second set of detected outputs with the signal strength of said first signal. - View Dependent Claims (42)
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43. A method of determining pseudoranges in a global positioning system (GPS) receiver said method comprising:
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receiving a plurality of signals from a plurality of in-view GPS satellites; selecting a first integration time period, selecting a set of at least two in view GPS satellites for processing at least two signals from said plurality of in-view satellites, for each GPS satellite in said set of at least two in view GPS satellites, performing a first method comprising; selecting a first set of Doppler frequency offsets; processing a signal, corresponding to each satellite in said set of at least two in view GPS satellites, over said first integration time and said first set of Doppler frequency offsets to a produce a first set of outputs; comparing said first set of outputs with a first detection threshold, in order to form a first set of detected outputs, corresponding to any of said first set of outputs that exceed said first detection threshold; associating time indices of said first set of detected outputs with a pseudorange of said signal and associating amplitudes of said first set of detected outputs with a signal strength of said first signal, selecting a second integration time period, which is longer than the first integration time period, for each GPS satellite in said set of at least two in view GPS satellites, for which said first set of detected outputs contained no members, performing a second method comprising; selecting a second set of Doppler frequency offsets; processing a signal corresponding to each satellite in said set of at least two in view GPS satellites for which said first set of detected outputs contained no members, over said second integration time and said second set of Doppler frequency offsets to a produce a second set of outputs; comparing said second set of outputs with a second detection threshold in order to form a second set of detected outputs, corresponding to any of said second set of outputs that exceed said second detection threshold associating time indices of said second set of detected outputs with a pseudorange of said signal and associating amplitudes of said second set of detected outputs with a signal strength of said signal. - View Dependent Claims (44)
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Specification