Satellite radio wave capturing method for a global positioning system (GPS) receiver

• US 5,323,164 A
• Filed: 03/05/1993
• Issued: 06/21/1994
• Est. Priority Date: 03/16/1992
• Status: Expired due to Term

• Current Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Original Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Inventors: Endo, Isao
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/026,050
• Time in Patent Office: 473 Days
• Field of Search: 342/357, 455/12.1
• US Class Current: 342/357.65
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence

Abstract

A satellite radio wave capturing method of a GPS receiver, in which an offset value of an oscillator of the GPS receiver is calculated by subtracting a Doppler frequency deviation of the first captured satellite radio wave from an actual received frequency of the first captured satellite radio wave, and with respect to the second and subsequent satellite radio waves to be captured, the search center frequencies are reset by using the calculated offset value, and an oscillating frequency of the oscillator is changed by using the set search center frequency as a reference, thereby capturing the radio wave of the target satellite. The elapsed time which is required from the power-OFF at the preceding position measurement by the GPS receiver to the power-ON at the present position measurement is measured. In accordance with the duration of the measured elapsed time, a determination is made to see whether or not the offset value of the oscillator which has been obtained at the preceding position measurement and stored in a memory in the GPS receiver is used as an offset value of the oscillator at the present position measurement. The mean value of a plurality of offset values obtained within a predetermined time just after the power-ON of the GPS receiver is calculated and stored. At the next power-ON of the receiver, the stored mean value of the offset values is used as an initial offset value at the start of the position measurement.

Claims

1. A satellite radio wave capturing method for a Global Positioning System (GPS) receiver, in which a search center frequency is set for every satellite radio wave to be captured and an oscillating frequency of an oscillator in said GPS receiver is changed using said set search center frequency as a reference, thereby capturing a radio wave of a target satellite, comprising the steps of:

calculating an offset value of said oscillator by subtracting a Doppler frequency deviation of a first captured satellite radio wave from an actual received frequency of said first captured satellite radio wave; and

resetting said search center frequency using said calculated offset value with respect to second and subsequent satellite radio waves to be captured.

2. A satellite radio wave capturing method for a Global Positioning System (GPS) receiver, in which a search center frequency is set using an offset value of an oscillator in said GPS receiver and a Doppler frequency deviation of a target satellite and an oscillating frequency of said oscillator is changed using said set search center frequency as a reference, thereby capturing a radio wave of a target satellite, comprising the steps of:

measuring an elapsed time from a power-OFF of said GPS receiver at a preceding position measurement by said GPS receiver to a power-ON of said GPS receiver at a present position measurement; and

on the basis of a duration of said measured elapsed time, determining whether or not an offset value of said oscillator at a preceding position measurement stored in a memory in said GPS receiver is used as an offset value of said oscillator at said present position measurement.

3. A satellite radio wave capturing method for a Global Positioning System (GPS) receiver, in which a search center frequency is set using an offset value of an oscillator in said GPS receiver and a Doppler frequency deviation of a target satellite and an oscillating frequency of said oscillator is changed using said set search center frequency as a reference, thereby capturing a radio wave of a target satellite, comprising the steps of:

calculating a mean value of a plurality of offset values obtained within a predetermined time just after a power-ON of said GPS receiver and storing said mean value; and

using said stored mean value of said offset values as an initial offset value at a start of position measurement at a time of a next power-ON of said GPS receiver.