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

• Current Assignee: Furuno Electric Co, Ltd
• Original Assignee: eRide, Inc. (Furuno Electric Co, Ltd), Seiko Epson Corporation (Seiko Group)
• Inventors: McBurney, Paul W., Rode, France, Woo, Arthur N.
• Granted Patent: US 7,592,951 B2
• Time in Patent Office: Days
• US Class Current: 342/357.1
• CPC Class Codes: G01S 19/03 Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain

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.

Claims

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.