Keeping Accurate Time For A Hybrid GPS Receiver And Mobile Phone When Powered Off
First Claim
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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Accused Products
Abstract
A hybrid navigation satellite receiver and mobile telephone uses only two crystal oscillators. One that operates a master clock around 27-MHz and that consumes milliwatts of power. The other oscillator consumes only microwatts of power and operates continuously on battery power at about 32-KHz. Only the second, low frequency oscillator is kept running during power “off”. On power “restart”, a real-time-clock counter is consulted to cause an estimate of the GPS system time to be regenerated and supplied to the GPS-DSP to quicken its initialization. The master clock is GPS-calibrated, and the accurate clock is used to drive NCO'"'"'s for the mobile telephone part and host CPU.
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Citations
1 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:
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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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Specification