High accuracy low power GPS time source

A global positioning system (GPS) receiver comprising:

• GPS signal receiving means for receiving Y-code modulated GPS signals from a plurality of GPS satellites;
• signal processing means for directly acquiring from the modulated GPS signals the Y-code used to modulate the GPS signals;
• low power time source means for providing to the signal processing means a digital representation of a time period for use in direct Y-code acquisition, the low power time source means comprising:
• an oscillator adapted to provide an uncompensated frequency signal having a quantity of frequency error over a time period relative to a desired frequency such that the uncompensated frequency signal has an average uncompensated frequency which is different than the desired frequency;
• and
• a counter operably coupled to the oscillator and generating as a function of the uncompensated frequency signal a digital representation of a time period;
• and
• compensation means for compensating the digital representation of the time period in order to minimize temperature dependent errors in the digital representation of the time period.

A method of providing a high accuracy time source for use in a global positioning system receiver for direct Y-code acquisition of GPS satellite signals, the method comprising:

• providing an uncompensated clock signal having a quantity of frequency error over a time period relative to a desired frequency such that the uncompensated clock signal has an average uncompensated frequency which is different than the desired frequency;
• sensing a temperature affecting the frequency error in the uncompensated clock signal;
• generating a control signal as a function of the sensed temperature, and thereby as a function of the quantity of frequency error over the time period;
• XORing the uncompensated clock signal and the control signal to provide a compensated clock signal;
• and
• counting cycles of the compensated clock signal to provide a digital representation of the time period.