Method for acquisition of GPS signals and GPS receiver with sample time error and frequency offset compensation
First Claim
1. A method performed by a global positioning system (GPS) receiver for acquisition of GPS signals for use in determining a geographic location, the method comprising resampling GPS signals at each of a plurality of different sample rates for each of a plurality of predetermined frequency offsets to compensate for sample time error and frequency offset of a crystal oscillator,wherein the resampling at different sample rates provides samples at different time-locations;
- andwherein the predetermined frequency offsets comprise possible frequency offsets between a reference frequency generated from the crystal oscillator and a reference frequency of the reference clocks of the GPS satellites.
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Abstract
Embodiments of a method for acquisition of GPS signals and a GPS receiver with sample time error and frequency offset compensation are generally described herein. Other embodiments may be described and claimed. In some embodiments, GPS signals are resampled at a plurality of sample rates for each of a plurality of predetermined frequency offsets to compensate for sample time error and frequency offset of a crystal oscillator. The resampled GPS signals may be cross correlated for each of the predetermined frequency offsets. In some embodiments, the sample time error and the frequency offset of the crystal oscillator may substantially exceed a time and frequency drift of reference clocks on GPS satellites.
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Citations
20 Claims
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1. A method performed by a global positioning system (GPS) receiver for acquisition of GPS signals for use in determining a geographic location, the method comprising resampling GPS signals at each of a plurality of different sample rates for each of a plurality of predetermined frequency offsets to compensate for sample time error and frequency offset of a crystal oscillator,
wherein the resampling at different sample rates provides samples at different time-locations; - and
wherein the predetermined frequency offsets comprise possible frequency offsets between a reference frequency generated from the crystal oscillator and a reference frequency of the reference clocks of the GPS satellites. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A GPS receiver comprising:
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resampling circuitry to resample received GPS signals at each of a plurality of different sample rates to provide samples at different time-locations; and a cross correlator to cross correlate the resampled signals for each of a plurality of predetermined frequency offsets, wherein resampling operations performed by the resampling circuitry at the plurality of sample rates, and cross correlation operations performed by the cross correlator for the predetermined frequency offsets, compensate for sample time error and frequency offset of a crystal oscillator within the GPS receiver, and wherein the predetermined frequency offsets comprise possible frequency offsets between a reference frequency generated from the crystal oscillator and a reference frequency of reference clocks of the GPS satellites. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A GPS receiver comprising:
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resampling circuitry to resample received GPS signals at each of a plurality of different sample rates to provide samples at different time-locations; and a cross correlator to cross correlate the resampled signals for each of a plurality of predetermined frequency offsets, wherein resampling operations performed by the resampling circuitry at the plurality of sample rates, and cross correlation operations performed by the cross correlator for the predetermined frequency offsets, compensate for sample time error and frequency offset of a crystal oscillator within the GPS receiver, wherein the resampling circuitry comprises; a resampler to resample the received GPS signals at the plurality of sample rates; a complex multiplier to frequency shift the resampled signals from the resampler with each of the predetermined frequency offsets to generate frequency-shifted samples; and wherein the cross correlator performs cross correlations with the frequency-shifted samples and known GPS symbols for each resampling operation performed by the resampler, to generate a correlation output, wherein the GPS receiver further comprises a resample controller to either generate each of the predetermined frequency offsets for application by the complex multiplier or provide each of the predetermined frequency offsets from a table, and wherein the resample controller individually provides the predetermined frequency offsets to the complex multiplier for each resampling operation performed by the resampler.
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16. A GPS receiver comprising:
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resampling circuitry to resample received GPS signals at each of a plurality of different sample rates to provide samples at different time-locations; and a cross correlator to cross correlate the resampled signals for each of a plurality of predetermined frequency offsets, wherein resampling operations performed by the resampling circuitry at the plurality of sample rates, and cross correlation operations performed by the cross correlator for the predetermined frequency offsets, compensate for sample time error and frequency offset of a crystal oscillator within the GPS receiver, wherein the resampling circuitry comprises; a resampler to resample the received GPS signals at the plurality of sample rates; and a complex multiplier to apply a frequency shift to known GPS symbols by applying each of the predetermined frequency offsets to generate frequency-shifted reference sequences, wherein the cross correlator performs a cross correlation with resampled signals from the resampler and the frequency-shifted reference sequences for each resampling operation performed by the resampler, wherein the GPS receiver further comprises a resample controller to either generate each of the predetermined frequency offsets for application by the complex multiplier or provide each of the predetermined frequency offsets from a table, and wherein the resample controller individually provides the predetermined frequency offsets to the complex multiplier for each resampling operation performed by the resampler.
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17. A spread spectrum receiver comprising:
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resampling circuitry to resample received GPS signals at each of a plurality of different sample rates to provide samples at different time-locations; and a cross correlator to cross correlate the resampled signals for each of a plurality of predetermined frequency offsets, wherein resampling operations performed by the resampling circuitry at the plurality of sample rates, and cross correlation operations performed by the cross correlator for the predetermined frequency offsets compensate for sample time error and frequency offset of a crystal oscillator within the receiver, wherein the cross correlator performs a cross correlation with resampled outputs from the resampling circuitry and one of a plurality of frequency-shifted reference sequences for each resampling operation, and wherein the plurality of sample rates and the plurality of frequency-shifted reference sequences are determined from possible frequency offsets and between a frequency output of the crystal oscillator and a frequency output of system reference clocks. - View Dependent Claims (18, 19, 20)
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Specification