METHOD OF ACQUIRING ERROR CORRECTION VALUE OF REFERENCE FREQUENCY, TERMINAL DEVICE, AND RECORDING MEDIUM

• US 20080068258A1
• Filed: 08/29/2007
• Published: 03/20/2008
• Est. Priority Date: 09/14/2006
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: MAEZAWA, Hidekazu, YANO, Koichiro
• Granted Patent: US 7,741,995 B2
• Time in Patent Office: Days
• US Class Current: 342/357.03
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence

Abstract

A terminal device receives satellite signals from a plurality of satellite positioning system (SPS) satellites and locates a position. The terminal device periodically calculates a first drift df1 of a local oscillator using a reference frequency Hr, calculates a search range of the satellite signal using the first drift df1, calculates a second drift df2 of the local oscillator using a reception frequency of the satellite signal, calculates a reference frequency error β which is an error of the reference frequency by calculating a difference between the first drift df1 and the second drift df2, and calculates an error correction value βav of the reference frequency by subjecting a plurality of the reference frequency errors β to a statistical process.

Claims

1. A method of causing a terminal device, which receives satellite signals from a plurality of satellite positioning system (SPS) satellites and locates a position, to acquire an error correction value of a reference frequency, the method comprising:

periodically calculating a first drift of a local oscillator using the reference frequency;

calculating a search range of the satellite signal using the first drift;

calculating a second drift of the local oscillator using a reception frequency of the satellite signal;

calculating a reference frequency error which is an error of the reference frequency by calculating a difference between the first drift and the second drift; and

calculating an error correction value of the reference frequency by subjecting a plurality of the reference frequency errors to a statistical process.

2. The method as defined in claim 1, comprising:

correcting the first drift by subjecting a plurality of the first drifts to a statistical process;

wherein the reference frequency error is calculated by calculating a difference between the corrected first drift and the second drift.

3. The method as defined in claim 2, wherein the first drift is corrected by generating a regression line based on a plurality of the first drifts, and calculating the first drift on the regression line corresponding to a present time.

4. A terminal device which receives satellite signals from a plurality of satellite positioning system (SPS) satellites and locates a position, the terminal device comprising:

a first drift calculation section which periodically calculates a first drift of a local oscillator using a reference frequency;

a search range calculation section which calculates a search range of the satellite signal using the first drift;

a second drift calculation section which calculates a second drift of the local oscillator using a reception frequency of the satellite signal;

a reference frequency error calculation section which calculates a reference frequency error which is an error of the reference frequency by calculating a difference between the first drift and the second drift; and

an error correction value calculation section which calculates an error correction value of the reference frequency by subjecting a plurality of the reference frequency errors to a statistical process.

5. The terminal device as defined in claim 4, comprising:

a first drift correction section which corrects the first drift by subjecting a plurality of the first drifts to a statistical process;

wherein the reference frequency error calculation section calculates the reference frequency error by calculating a difference between the corrected first drift and the second drift.

6. The terminal device as defined in claim 5, wherein the first drift correction section corrects the first drift by generating a regression line based on a plurality of the first drifts, and calculating the first drift on the regression line corresponding to a present time.

7. A computer-readable recording medium storing a program for a computer included in a terminal device which receives satellite signals from a plurality of satellite positioning system (SPS) satellites and locates a position, the program causing the computer to:

periodically calculate a first drift of a local oscillator using a reference frequency;

calculate a search range of the satellite signal using the first drift;

calculate a second drift of the local oscillator using a reception frequency of the satellite signal;

calculate a reference frequency error which is an error of the reference frequency by calculating a difference between the first drift and the second drift; and

calculate an error correction value of the reference frequency by subjecting a plurality of the reference frequency errors to a statistical process.

8. The recording medium as defined in claim 7,

wherein the program causes the computer to correct the first drift by subjecting a plurality of the first drifts to a statistical process;

and

wherein the reference frequency error is calculated by calculating a difference between the corrected first drift and the second drift.

9. The recording medium as defined in claim 8, wherein the first drift is corrected by generating a regression line based on a plurality of the first drifts, and calculating the first drift on the regression line corresponding to a present time.