Method and apparatus for self-calibration and adaptive temperature compensation in GPS receivers

A method of compensating an oscillator frequency drift, comprising:

• encoding a memory device with a first look-up table;
• determining a frequency drift value associated with a temperature reading of said oscillator;
• incrementally populating said first look-up table with said frequency drift values as said oscillator is exposed to temperature changes;
• acquiring satellite signals;
• computing a frequency drift value at a current temperature after the receiver has acquired the satellite signals;
• when a frequency drift value is presently stored in the first look-up table at the current temperature, averaging the computed frequency drift value with the presently stored frequency drift value in said first look-up table to obtain an average frequency drift value;
• replacing the presently stored frequency drift value in said first look-up table with the average frequency drift value;
• and
• validating said frequency drift values before storing in said first look-up table.

A navigational satellite signal receiver, comprising:

• a local reference oscillator;
• a temperature sensor in proximity or within said oscillator for obtaining temperature readings on said oscillator;
• a processor coupled to said temperature sensor, said processor capable of processing navigational satellite signals;
• and
• a memory device coupled to said processor and encoded with a first look-up table for storing frequency drift values associated with said temperature readings of said oscillator;
• wherein
• said first look-up table incrementally populated with said frequency drift values as said oscillator is exposed to temperature changes;
• wherein
• said processor utilizes said first look-up table to adaptively compensate said temperature changes;
• and wherein
• said processor computes a frequency drift value at a current temperature after the receiver has acquired satellites signals;
• wherein when a frequency drift value is presently stored in the first look-up table at the current temperature, said processor averages the computed frequency drift value at the current temperature with the presently stored frequency drift value at the current temperature to obtain an average frequency drift value and replaces the presently stored drift value in the first look-up table with the average frequency drift value at the current temperature;
• and
• wherein said memory device is encoded with a second look-up table for confirming that valid frequency drift values are stored in said first look-up table.

A computer-readable medium storing computer-executable program instructions, comprising:

• code for encoding a memory device with a first look-up table;
• code for determining a frequency drift value associated with a temperature reading of said oscillator;
• code for incrementally populating said first look-up table with said frequency drift values as said oscillator is exposed to temperature changes;
• code for adaptively compensating said temperature changes utilizing said first look-up table;
• code for initializing said first look-up table to all zeros;
• code for averaging frequency drift values associated with same temperature reading;
• code for retrieving from said first look-up table a frequency drift value that correspond to a temperature reading;
• code for discarding one or more frequency drift values that are higher or lower than predefined threshold values;
• code for validating said frequency drift values before storing in said first look-up table;
• code for encoding said memory device with a second look-up table encoding said memory device with a second look-up table comprising indices that indicate which entries in the first look-up table have valid frequency drift values;
• and
• code for determining whether there are at least two valid frequency drift values and correspondingly interpolating or extrapolating said at least two valid frequency drift values.

A method of compensating an oscillator frequency drift, comprising:

• encoding a memory device with a first look-up table;
• determining a frequency drift value associated with a temperature reading of said oscillator;
• incrementally populating said first look-up table with said frequency drift values as said oscillator is exposed to temperature changes;
• adaptively compensating said temperature changes utilizing said first look-up table;
• acquiring satellite signals;
• computing a frequency drift value at a current temperature after a receiver has acquired satellite signals;
• wherein when the first look-up table contains a single valid frequency drift value and the current temperature does not correspond to the single valid frequency drift value, further comprising:
• utilizing a zero frequency drift value in the compensating step.

A method of compensating an oscillator frequency drift, comprising:

• encoding a memory device with a first look-up table;
• determining a frequency drift value associated with a temperature reading of said oscillator;
• incrementally populating said first look-up table with said frequency drift values as said oscillator is exposed to temperature changes;
• adaptively compensating said temperature changes utilizing said first look-up table;
• acquiring satellite signals;
• computing a frequency drift value at a current temperature after a receiver has acquired satellite signals;
• wherein the oscillator is a temperature compensated oscillator and when the current temperature is above a predetermined temperature, further comprising:
• assuming that the frequency drift is at a constant value above the predetermined temperature;
• and
• utilizing the constant value in the compensating step.

A method of compensating an oscillator frequency drift, comprising:

• encoding a memory device with a first look-up table;
• determining a frequency drift value associated with a temperature reading of said oscillator;
• incrementally populating said first look-up table with said frequency drift values as said oscillator is exposed to temperature changes;
• adaptively compensating said temperature changes utilizing said first look-up table;
• acquiring satellite signals;
• computing a frequency drift value at a current temperature after a receiver has acquired satellite signals;
• wherein the oscillator is a temperature compensated oscillator and when the current temperature is below a predetermined temperature, further comprising:
• assuming that the frequency drift is at a constant value below the predetermined temperature;
• and
• utilizing the constant value in the compensating step.

A method of compensating an oscillator frequency drift, comprising:

• encoding a memory device with a first look-up table;
• determining a frequency drift value associated with a temperature reading of said oscillator;
• incrementally populating said first look-up table with said frequency drift values as said oscillator is exposed to temperature changes;
• adaptively compensating said temperature changes utilizing said first look-up table;
• acquiring satellite signals;
• computing a frequency drift value at a current temperature after a receiver has acquired satellite signals;
• wherein when the first look-up table does not contain a valid frequency drift value at the current temperature, further comprising:
• extrapolating the frequency drift value at the current temperature using frequency drift values stored in the first look-up table;
• determining an error of the extrapolation;
• if the error is below a predetermined value, utilizing the extrapolated frequency drift value in the compensating step;
• and
• if the error is above the predetermined value, utilizing a zero frequency drift value in the compensating step.