Calibration and correction system for satellite position location systems
First Claim
1. A method of calibrating and correcting a GPS receiver to receive a GPS signal in a mobile device using an externally transmitted signal, comprising:
- producing a first frequency locked to said externally transmitted signal;
generating a second frequency in a GPS oscillator that is applied to process said GPS signal;
predicting a GPS oscillator error for the next time period; and
correcting the GPS receiver in the next time period responsive to said predicted GPS frequency error.
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Accused Products
Abstract
To provide accurate and quick position measurements in a practical mobile position location system, the GPS receiver is calibrated, a frequency error in the next time period is predicted using a first frequency locked to an externally transmitted signal, and a second frequency is generated by a GPS oscillator. To predict the error in the next time period, several measurements are made over time, error estimations are made, an error function is approximated responsive to the set of error estimations. This predicted error is then used to correct the GPS receiver in the next time period. In one implementation, a multiple function portable device is disclosed for providing cellular communication using a network of cellular stations that operate at predefined ideal cellular frequencies, and also for providing position location using GPS satellites that transmit GPS signals at a predefined GPS frequency.
47 Citations
25 Claims
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1. A method of calibrating and correcting a GPS receiver to receive a GPS signal in a mobile device using an externally transmitted signal, comprising:
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producing a first frequency locked to said externally transmitted signal;
generating a second frequency in a GPS oscillator that is applied to process said GPS signal;
predicting a GPS oscillator error for the next time period; and
correcting the GPS receiver in the next time period responsive to said predicted GPS frequency error. - View Dependent Claims (2, 3, 4, 5)
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6. A method of calibrating and correcting a GPS receiver in a mobile device using an externally transmitted signal other than a GPS signal, said externally transmitted signal having a predefined precision carrier frequency, to receive a GPS signal transmitted at a predefined GPS frequency, comprising the steps of:
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generating a first frequency signal responsive to said precision carrier frequency;
generating a second frequency signal in said GPS receiver, said second frequency signal applied to process said GPS signal;
estimating an error in said first and second frequencies in a first time period, and repeating said error estimating step for at least one additional time period to provide a set of error estimations;
approximating an error function of said second frequency responsive to said set of error estimations;
predicting an error in a next time period utilizing said approximated function; and
correcting said second frequency of said GPS receiver to process said GPS signal in said next time period responsive to said predicted error. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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14. A method of calibrating and correcting a GPS receiver in a mobile device to receive a GPS signal transmitted at a predefined GPS frequency using a communication signal transmitted from a cellular base staion, said communication signal including a predefined precision carrier frequency, comprising the steps of:
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synchronizing a first local oscillator to the precision carrier frequency to generate a first frequency;
generating a second frequency signal in said GPS receiver having a nominal value close to a predetermined value, said second frequency signal applied to process said GPS signal;
monitoring said first and second frequencies over a plurality of time periods to provide a frequency measurement for each of said plurality of time periods;
estimating an error in said first and second frequencies for each monitored time period to provide a set of error estimations;
approximating a frequency error vs. time function for said second frequency by fitting a mathematical function responsive to said set of error estimations;
predicting an error in a next time period utilizing said approximated function;
developing a correction signal for said next time period responsive to said predicted error; and
processing said GPS signal responsive to said correction signal. - View Dependent Claims (15, 16, 17, 18)
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19. A multiple function portable device for providing cellular communication using a network of cellular stations that operate at predefined ideal cellular frequencies, and also for providing position location using GPS satellites that transmit GPS signals at a predefined GPS frequency, comprising:
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a cellular communication system including a first local oscillator that generates a first frequency for demodulating communications with said network of cellular stations;
a GPS system including a second local oscillator that generates a second frequency coupled to process said GPS signals;
an error prediction and correction system that predicts an error in a next time period responsive to measurements of said first and second frequencies over a plurality of previous time periods, said system also generating a correction signal for said next time period responsive to said predicted error; and
a local oscillator in said GPS system that receives said correction signal and responsive thereto processes said GPS signal during said next time period. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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Specification