GPS receiver device and method for calibrating a temperature uncompensated crystal oscillator
First Claim
1. A GPS satellite receiver device for locking to a signal transmitted from a satellite, the GPS receiver device comprising:
- a receiver for receiving the satellite signal;
an oscillator having a crystal, wherein said crystal has an operable temperature range and oscillates at an actual frequency which drifts from a nominal frequency of said crystal over said operable temperature range of said crystal;
a memory device for storing data indicative of said actual frequency at which said crystal oscillates over said operable temperature range of said crystal;
a temperature sensor for sensing temperature in proximity to said crystal and emitting a signal indicative of the temperature sensed; and
a processor for receiving said satellite signal and said signal indicative of the temperature sensed and retrieving from said memory the data indicative of the crystal oscillation frequency associated with the sensed temperature, wherein said data is utilized as starting data in an attempt to match said data indicative of the crystal oscillation frequency with data indicative of said frequency of said satellite signal.
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Abstract
A device and method for compensating a crystal oscillator that is not electrically compensated over its operable temperature range. A GPS receiver device stores in memory data indicative of the actual offset frequency of oscillation of the crystal over its operable temperature range. The first time the device is activated, the temperature at the crystal is sensed and data, stored in memory, indicative of the specified frequency offset of the crystal at the sensed temperature is retrieved, and used to control the receiver\decoder. When the receiver locks onto a sufficient number of satellites to calculate its two-dimensional location, the actual frequency offset of the crystal is calculated and stored in memory. Repeated use of the receiver device permits a database of actual frequency offset data of the crystal, over its operable temperature range to be stored. Subsequent uses of the device permit retrieval of this data for use in locking the receiver onto satellite signals. If such data is not available, the device uses the average offset data at the given temperature. The device further adjusts the offset data originally retrieved or computed until the receiver locks onto the desired signal.
170 Citations
13 Claims
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1. A GPS satellite receiver device for locking to a signal transmitted from a satellite, the GPS receiver device comprising:
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a receiver for receiving the satellite signal; an oscillator having a crystal, wherein said crystal has an operable temperature range and oscillates at an actual frequency which drifts from a nominal frequency of said crystal over said operable temperature range of said crystal; a memory device for storing data indicative of said actual frequency at which said crystal oscillates over said operable temperature range of said crystal; a temperature sensor for sensing temperature in proximity to said crystal and emitting a signal indicative of the temperature sensed; and a processor for receiving said satellite signal and said signal indicative of the temperature sensed and retrieving from said memory the data indicative of the crystal oscillation frequency associated with the sensed temperature, wherein said data is utilized as starting data in an attempt to match said data indicative of the crystal oscillation frequency with data indicative of said frequency of said satellite signal. - View Dependent Claims (2, 3, 4, 5)
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6. A GPS satellite receiver device for locking to a signal transmitted, at a selected frequency, from a satellite, the GPS receiver device comprising:
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a receiver for receiving the satellite signal; an oscillator having a crystal, wherein said crystal has an operable temperature range, a nominal oscillation frequency, and wherein the actual oscillation frequency of said crystal drifts, within a known range of frequency drift, from said nominal frequency over said operable temperature range of said crystal; a memory means for storing data indicative of said range of frequency drift over said operable temperature range of said crystal; a temperature sensor for sensing temperature in proximity to said crystal and emitting a signal indicative of the temperature sensed; and a processor for receiving said satellite signal and said signal indicative of the temperature sensed and retrieving from said memory the data indicative of the range of frequency drift of said crystal at the sensed temperature, wherein, when data indicative of said actual oscillation frequency of said crystal matches data indicative of the frequency of said satellite signal, said GPS satellite receiver device locks onto said satellite signal, and when data indicative of said actual oscillation frequency of said crystal does not match data indicative of a selected frequency of said satellite signal, said data initially retrieved from memory is adjusted until it matches said data indicative of the frequency of the satellite signal. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. A method of calibrating a crystal oscillator in a GPS receiver device having a memory, the receiver for locking onto a signal transmitted from a satellite, the crystal oscillator having a crystal with specified offset frequency characteristics over an operable temperature range, the method comprising:
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storing in memory data indicative of the specified offset frequency characteristics of said crystal over the operable temperature range of said crystal; sensing the temperature of said crystal in operation; retrieving from said memory data indicative of the offset frequency of the crystal at the temperature sensed and using that data to control said receiver; and adjusting said data indicative of said offset frequency until said receiver device locks onto said satellite signal.
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Specification