MEMORY REDUCTION METHOD FOR A DSP-BASED GPS PROCESSOR
First Claim
1. A GPS receiver data storage apparatus comprising:
- a first switch, said first switch receiving a digital GPS data;
a first memory;
a second memory in parallel with said first memory, with said first memory and said second memory being selectable by said first switch for filling with said digital GPS data; and
a second switch selectable between said first memory and said second memory for extracting said digital GPS data therefrom;
wherein GPS signal processing extracts digital GPS data from said first memory while said second memory is being filled and extracts digital GPS data from said second memory while said first memory is being filled.
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Abstract
A method and apparatus for determining position in a GPS receiver (FIG. 4) is provided according to the invention. The apparatus includes a first switch (402), the first switch (402) receiving a digital GPS data, a first memory (409), a second memory (410) in parallel with the first memory, with the first memory and the second memory selectable by the first switch (402) for filling with the digital GPS data, and a second switch (416) selectable between the first memory (409) and the second memory (410) in order to extract the digital GPS data therefrom, wherein DSP signal processing (140) extracts digital GPS data from the first memory (409) while the second memory (410) is being filled and extracts digital GPS data from the second memory (410) while the first memory is being filled, and wherein the first memory (409) and the second memory (410) allow the digital GPS data to be processed in real time.
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Citations
40 Claims
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1. A GPS receiver data storage apparatus comprising:
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a first switch, said first switch receiving a digital GPS data;
a first memory;
a second memory in parallel with said first memory, with said first memory and said second memory being selectable by said first switch for filling with said digital GPS data; and
a second switch selectable between said first memory and said second memory for extracting said digital GPS data therefrom;
wherein GPS signal processing extracts digital GPS data from said first memory while said second memory is being filled and extracts digital GPS data from said second memory while said first memory is being filled. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A GPS receiver apparatus, comprising:
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a first switch, said first switch receiving a digital GPS data;
a first memory;
a second memory in parallel with said first memory, with said first memory and said second memory being selectable by said first switch for filling with said digital GPS data;
a second switch selectable between said first memory and said second memory for extracting said digital GPS data therefrom;
a mixer connected to said second switch and further connected to a numerically controlled oscillator with said numerically controlled oscillator being provided with a predetermined Doppler characteristic, said mixer being capable of removing said predetermined Doppler characteristic from said digital GPS data;
a stack RAM connected to said mixer, said stack RAM being capable of accumulating a predetermined time interval of said digital GPS data from said mixer;
a correlator connected to said stack RAM, said correlator also receiving a predetermined Gold code, with said correlator being capable of correlating said predetermined Gold code against said digital GPS data;
a magnitude squaring block connected to said correlator, said magnitude squaring block squaring the correlation output to produce a squared integration output; and
a non-coherent integrator connected to said magnitude squaring block and capable of integrating said squared integration output to provide a pseudorange and Doppler characteristic output;
wherein GPS signal processing extracts digital GPS data from said first memory while said second memory is being filled and extracts digital GPS data from said second memory while said first memory is being filled, and wherein said first memory and said second memory allow said digital GPS data to be processed in real time;
and wherein said numerically controlled oscillator is capable of being provided with a Doppler characteristic for a selected visible GPS satellite and said correlator is capable of being provided with a corresponding Gold code for said selected visible GPS satellite to enable said apparatus to process a digital GPS data for said selected visible GPS satellite. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39, 40)
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23. A method of storing and processing a digital GPS signal in a GPS receiver having a reduced amount of memory, comprising the steps of:
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storing said digital GPS signal in a first memory during a first predetermined time period;
extracting a first stored digital GPS data segment from a second memory simultaneous with said storing of said digital GPS signal in said first memory;
wherein during subsequent predetermined time periods said storing step alternates between said first memory and said second memory while said extracting step alternates between said second memory and said first memory.
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26. A method of storing and processing a digital GPS signal in a GPS receiver having a reduced amount of memory, comprising the steps of:
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storing said digital GPS signal in a first memory during a first predetermined time period;
extracting a first stored digital GPS data segment from a second memory simultaneous with said storing of said digital GPS signal in said first memory;
generating a predetermined Doppler signature for a subject visible satellite;
mixing said predetermined Doppler signature with said first stored digital GPS data segment to remove a Doppler characteristic from said first stored digital GPS data segment;
correlating a Gold code of said subject visible satellite to said first stored digital GPS data segment, producing a correlation output; and
integrating said correlation output to produce a pseudorange output and a Doppler output;
wherein said generating step through said mixing step are repeated for each visible satellite, and wherein during subsequent predetermined time periods said storing step alternates between said first memory and said second memory while said extracting step alternates between said second memory and said first memory.
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34. A method of minimizing a GPS satellite search time in a GPS receiver having a plurality of correlation and integration satellite processing branches, comprising the steps of:
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computing initial conditions that estimate a position of said GPS receiver and that estimate a GPS receiver clock accuracy;
computing an initial range estimate; and
computing an optimum satellite search order, with said optimum satellite search order computed so as to minimize a search space and minimize a search time needed to find visible GPS satellites.
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Specification