Keeping accurate time for a hybrid GPS receiver and mobile phone when powered off

• US 7,362,263 B2
• Filed: 04/20/2005
• Issued: 04/22/2008
• Est. Priority Date: 09/04/2003
• Status: Active Grant

• Current Assignee: Furuno Electric Co, Ltd, Seiko Epson Corporation (Seiko Group)
• Original Assignee: eRide, Inc. (Furuno Electric Co, Ltd), Seiko Epson Corporation (Seiko Group)
• Inventors: McBurney, Paul W., Rode, France, Woo, Arthur N.
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US11/110,200
• Publication Number:
  US 20050195105A1
• Time in Patent Office: 1,098 Days
• Field of Search: 342/357.12, 342/357.02
• US Class Current: 342/357.62
• 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 hybrid navigation satellite receiver and mobile telephone combination (100), comprising:

a master clock and reference oscillator (112,114) for both a GPS receiver (102) and mobile telephone (104, and that consumes milliwatts of power, and that is shut off during a power down of a hybrid navigation satellite receiver and mobile telephone combination (100);

a real time clock (RTC) and oscillator (126,128) that consumes only microwatts of power and operates continuously on battery power at about 32-KHz regardless of said power down;

a GPS time regenerator (124) connected to the RTC (126) and providing for a regenerated GPS restart-time to a GPS-DSP (110) computed from an off-time and offset when said navigation satellite receiver (102) last was tracking GPS system time and frequency errors of the master clock were being corrected;

a software controlled oscillator (SCXO) (118) for correcting the operating frequency of the master clock and reference oscillator (112,114) according to GPS time provided by said GPS-DSP (110), or provided by said regenerated GPS time from the GPS time regenerator (124) when GPS time is unavailable because tracking has not yet commenced;

wherein, the master clock and reference oscillator (112,114) provides a corrected local oscillator reference frequency for both a GPS-RF stage (108) and a communications transceiver (132); and

wherein, on any subsequent power restart, the navigation satellite receiver (102) can reduce frequency uncertainties and quicken its cold-start initialization.

2. The hybrid combination of claim 1, further comprising:

a 27-MHz crystal disposed in the master clock oscillator (112,114); and

a 32-KHz crystal (128) disposed in the RTC.

3. The hybrid combination of claim 1, further comprising:

a host CPU (136) co-resident with the GPS radio frequency and DSP processing stage and the mobile telephone transceiver and DSP processing stage; and

a numeric controlled oscillator (NCO) (138) programmable by the host CPU and connected to supply variable local oscillator reference frequencies.

4. The hybrid combination of claim 1, wherein:

the GPS time regenerator (124) continuously associates an offset count from the RTC with GPS system time and stores a last association when a “

power off”

command is input.

5. The hybrid combination of claim 4, wherein:

when a power “

restart”

command is input, the GPS time regenerator (124) reads in a current offset count from the RTC (126) and combines it with said last association to estimate a regenerated GPS system time.

6. The hybrid combination of claim 5, wherein:

the GPS time regenerator (124) provides for initialization of the GPS-DSP processing stage with said regenerated GPS system time.