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

• US 7,450,062 B2
• Filed: 02/27/2008
• Issued: 11/11/2008
• Est. Priority Date: 09/04/2003
• Status: Expired due to Term

• Current Assignee: Furuno Electric Co, Ltd
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: McBurney, Paul W., Rode, France, Woo, Arthur N.
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US12/038,004
• Publication Number:
  US 20080143591A1
• Time in Patent Office: 258 Days
• Field of Search: 342/357.02, 342/357.06, 342/357.1, 342/357.12
• US Class Current: 342/357.4
• 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 integrated satellite navigation receiver and communication device combination system, comprising:

a single portable device that includes a global positioning system (GPS) receiver part and a communications transceiver part;

said GPS receiver part including a GPS RF-receiver, a GPS digital processor and frequency generator (GPS-chip), a GPS oscillator (oscGPS), a lower-frequency oscillator (osc3) operating at about 32-KHz, and a clock selector for selecting between clock frequency choices for normal and time-keeping only low-power operation;

said communications transceiver part including a cellphone transceiver, a digital signal processor (DSP), a phone host CPU, a divider, and a voltage controlled oscillator (VCO);

wherein, at turn-on, the GPS-chip loads a default startup processor clock synthesis-frequency value for said phone CPU, and a host processor clock frequency is generated by multiplying a GPS clock that is input to a numeric controlled oscillator (NCO) that can then be digitally programmed to generate a requested output frequency; and

wherein, if the GPS receiver part is tracking GPS satellites and solving for frequency error, it compensates a requested frequency by computing the error in said GPS oscillator (oscGPS) to provide a more stable frequency to said VCO.

2. The system of claim 1, wherein:

said host CPU is enabled to chose different frequencies via a communication link between the host CPU and said GPS-chip; and

said communications transceiver part can request a particular output frequency, and it can control when said VCO begins outputting such frequency.

3. The system of claim 1, wherein:

the communications transceiver part sends a request for said GPS receiver part to enter said low-power mode if a low-power mode is to be engaged.

4. The system of claim 1, wherein:

time is maintained with a low frequency crystal with an input from osc3.

5. The system of claim 1, wherein:

said GPS receiver part sends interrupts to the communications transceiver part that wake certain processes.

6. The system of claim 1, wherein:

the GPS receiver part puts itself into a sleeping, low-power mode and enables a user to decide when to use the GPS function.

7. The system of claim 1, further comprising:

a variable-VCO output from said GPS receiver part responsive to requests from said communications transceiver part to generate particular frequencies, waveforms, and phasing.

8. The system of claim 1, further comprising:

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