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Keeping Accurate Time For A Hybrid GPS Receiver And Mobile Phone When Powered Off

  • US 20080143590A1
  • Filed: 02/27/2008
  • Published: 06/19/2008
  • Est. Priority Date: 09/04/2003
  • Status: Active Grant
First Claim
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1. A method for limiting the number of crystals needed for reference oscillators when integrally combining a navigation receiver and cellphone to two, comprising:

  • providing a GPS oscillator with a first crystal operating at about 27-MHz;

    providing a watch oscillator with a second crystal operating at about 32-KHz;

    connecting a multiplier to the GPS oscillator to produce higher frequencies to operate a GPS receiver;

    generating a VCO frequency with a first numeric controlled oscillator (NCO1) to operate a communications transceiver;

    generating a host CPU frequency with a second numeric controlled oscillator (NCO2); and

    producing time events to host CPU with logic combinations of GPS-msec interrupts, GPS-second pulses, digital offsets, and said watch oscillator.

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