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

• US 7,598,909 B2
• Filed: 09/11/2008
• Issued: 10/06/2009
• Est. Priority Date: 09/04/2003
• Status: Expired due to Fees

• 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.
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US12/208,450
• Publication Number:
  US 20090002225A1
• Time in Patent Office: 390 Days
• Field of Search: None
• 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. An apparatus comprising:

a global position system (GPS) navigation receiver part including;

a GPS radio frequency (RF)-receiver, a GPS oscillator that provides a reference frequency to the GPS RF receiver, a low-frequency oscillator, a clock selector to select between the GPS oscillator and the low-frequency oscillator, a GPS-chip including a GPS digital processor for acquiring and tracking GPS satellite signals from the GPS RF receiver when connected by the clock selector to the GPS oscillator, and a numeric controlled oscillator (NCO) with a frequency output that can be compensated with GPS satellite time standard information derived during the tracking of said GPS satellites;

a communications transceiver part having no crystal oscillator of its own by depending on frequency references provided over said NCO output, and including;

a cellphone transceiver, a digital signal processor connected to the cellphone transceiver, a phone host CPU, a clock frequency divider connected to receive GPS-corrected frequencies from said NCO output instead of a communications VCO-crystal, and a voltage controlled oscillator (VCO) that receives a reference clock frequency output from the divider, and that provides a programmable synthesized reference frequency for the cellphone transceiver that has been compensated to GPS satellite time standards by values loadable into said NCO;

wherein, at turn-on, the GPS-chip loads a default value for the phone host processor CPU into said NCO that will produce a startup processor clock, and thereafter a particular NCO output frequency can be requested by loading other values into said NCO; and

wherein, the GPS receiver part provides for the compensation of NCO output frequencies by computing any error in the GPS oscillator to provide a compensated frequency to the VCO.

2. The apparatus of claim 1, further comprising:

a communication link between the phone host CPU and the GPS-chip providing for the loading of values to said NCO that will produce particular NCO output frequencies; and

the communications transceiver part can request a particular output frequency to change the band of operation of the cellphone transceiver, and when the voltage controlled oscillator begins outputting such frequency.

3. The apparatus of claim 1, wherein:

the clock selector selects between clock frequency choices for a first operation mode and a second operation mode that needs less power for time maintenance during a sleeping period; and

the communications transceiver part sends a request for the GPS receiver part to enter the second operation mode if the second operation mode is to be engaged.

4. The apparatus of claim 1, wherein:

the GPS receiver part sends interrupts to the communications transceiver part to trigger time maintenance processes.

5. The apparatus of claim 1, wherein:

the clock selector selects between clock frequency choices for a first operation mode and a second operation mode that needs less power than the first operation mode; and

the GPS receiver part puts itself into the second operation mode and enables a user to decide when to use the GPS function.

6. The apparatus of claim 1, wherein:

the output of said NCO in the GPS receiver part is responsive to requests from the communications transceiver part to generate particular frequencies, waveforms, and phasing.

7. The apparatus of claim 1, wherein:

a time interval interrupt is constructed from combinations of GPS-second and GPS-millisecond interrupts included in the GPS receiver part.