Device and method for minimizing the number of crystal oscillators used in an integrated navigation receiver and cellphone

• US 7,592,951 B2
• Filed: 02/27/2008
• Issued: 09/22/2009
• 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:
  US12/038,000
• Publication Number:
  US 20080143590A1
• Time in Patent Office: 573 Days
• Field of Search: 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. A method for limiting the number of crystals in a combination of a navigation receiver and cellphone, comprising:

generating reference frequencies from one master clock crystal reference oscillator for general use by each of a collocated navigation receiver, mobile telephone and host CPU, the general use including controlling a master clock to maintain generated Global Positioning System (GPS) system time;

stopping the generating of said reference frequencies from said master clock crystal reference oscillator when a user inputs a power-off command;

restarting the generating of said reference frequencies from said master clock crystal reference oscillator when a user inputs a power-restart command;

continuously operating a real-time clock (RTC) and crystal at a frequency orders of magnitude less than said one master clock crystal reference oscillator, and said RTC thereby consumes orders of magnitude less operating power than said one master clock crystal reference oscillator;

regenerating GPS system time from said RTC when said user inputs said power restart command; and

using a software controlled crystal oscillator (SCXO) to receive current time information derived from RTC and previous samples of accurate time derived from GPS receiver, and current temperature information (T), and then to provide corrections to said master clock crystal reference oscillator during a user initiated power restart;

wherein, said crystals are the only ones included in the whole combination of said collocated navigation receiver, mobile telephone and host CPU; and

wherein, continuously operating said RTC during power down substantially improves any frequency uncertainty that would otherwise prevail for said one master clock crystal reference oscillator from a power restart.

2. An integrated navigation receiver and cellphone with a minimized number of crystal oscillators, comprising:

one master clock crystal reference oscillator for generating reference frequencies for general use by each of a collocated navigation receiver, mobile telephone and host CPU, the general use including controlling a master clock to maintain generated Global Positioning System (GPS) system time;

a power-off device for stopping the generating of said reference frequencies from said master clock crystal reference oscillator when a user inputs a power-off command;

a power restart device for restarting the generating of said reference frequencies from said master clock crystal reference oscillator when a user inputs a power-restart command;

a real-time clock (RTC) and crystal for continuously operating at a frequency orders of magnitude less than said one master clock crystal reference oscillator, and said RTC thereby consumes orders of magnitude less operating power than said one master clock crystal reference oscillator;

a device for regenerating GPS system time from said RTC when said user inputs said power restart command;

a software controlled crystal oscillator (SCXO) to receive current time information derived from RTC and previous samples of accurate time derived from GPS receiver, and current temperature information (T), and then to provide corrections to said master clock crystal reference oscillator during a user initiated power restart;

wherein, said crystals are the only ones included in the whole combination of said collocated navigation receiver, mobile telephone and host CPU.