Positioning device, electronic instrument, and storage medium storing program

• US 7,570,207 B2
• Filed: 08/16/2007
• Issued: 08/04/2009
• Est. Priority Date: 10/26/2006
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kimura, Akira
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Liu; Harry
• Application Number:
  US11/839,614
• Publication Number:
  US 20080100509A1
• Time in Patent Office: 719 Days
• Field of Search: 342/357.12
• US Class Current: 342/357.63
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain

Abstract

Signals output from two filters included in a filter section 70 and differing in passband are respectively stored in different memories included in a memory section 80, and a positioning process is performed based on the signal stored in the memory. Specifically, the signal strength of a received signal is calculated by a coherent accumulation process and an incoherent accumulation process, and a signal system used for positioning is alternatively switched to a high-sensitivity system S1 or a high-accuracy system S2 as a result of determining whether or not the signal strength is equal to or greater than a threshold value.

Claims

1. A positioning device comprising:

a plurality of filters which differ in passband, each of the filters extracting a signal in a specific frequency band from a signal received by an RF reception circuit section which receives a GPS satellite signal;

storage sections which correspond to the respective filters, each of the storage sections storing a signal output from the corresponding filter; and

a positioning section which alternatively selects one of the storage sections and performs a specific positioning process based on the signal stored in the selected storage section.

2. The positioning device as defined in claim 1, wherein the positioning section acquires the satellite signal by performing a coherent accumulation process for the signal stored in the selected storage section while changing a coherent accumulation time depending on the selected storage section, and then performs the specific positioning process.

3. The positioning device as defined in claim 2,

wherein the filters have a passband inclusion relationship;

and

wherein the positioning section performs the coherent accumulation process with a longer coherent accumulation time for the signal stored in the storage section corresponding to the filter with a narrower passband.

4. The positioning device as defined in claim 2, wherein the GPS satellite signal received by the RF reception circuit section includes signals respectively transmitted from a plurality of satellites;

and wherein the positioning section selects the storage section and acquires and/or tracks the satellite signal from the satellite in units of acquisition and/or tracking target satellites.

5. The positioning device as defined in claim 2, wherein the positioning section includes a switch determination section which determines whether or not to switch the storage section selected, 1) when an acquisition target satellite used for the positioning process has been changed, or 2) each time the positioning process is periodically performed, and selects the storage section determined by the switch determination section after the switch determination section has determined to switch the storage section.

6. The positioning device as defined in claim 5, wherein the switch determination section determines whether or not to switch the storage section subsequently selected based on a signal strength calculated by the coherent accumulation process with a coherent accumulation time corresponding to the selected storage section.

7. The positioning device as defined in claim 6, wherein the switch determination section determines to switch the storage section to the storage section corresponding to the filter with a broader band when the signal strength calculated by the coherent accumulation process with a coherent accumulation time corresponding to the selected storage section satisfies a specific high-strength condition, and determines to switch the storage section to the storage section corresponding to the filter with a narrower band when the signal strength satisfies a specific low-strength condition.

8. An electronic instrument comprising the positioning device as defined in claim 1.

9. A computer-readable storage medium storing a program for a device which includes a plurality of filters which differ in passband, each of the filters extracting a signal in a specific frequency band from a signal received by an RF reception circuit section which receives a GPS satellite signal, storage sections which correspond to the respective filters, each of the storage sections storing a signal output from the corresponding filter, and a processor which can execute a program,

the program causing the processor to function as:

a positioning section which alternatively selects one of the storage sections and performs a specific positioning process based on the signal stored in the selected storage section.

10. The storage medium as defined in claim 9, wherein the positioning section acquires the satellite signal by performing a coherent accumulation process for the signal stored in the selected storage section while changing a coherent accumulation time depending on the selected storage section, and then performs the specific positioning process.

11. The storage medium as defined in claim 10,

wherein the filters have a passband inclusion relationship;

and

wherein the positioning section performs the coherent accumulation process with a longer coherent accumulation time for the signal stored in the storage section corresponding to the filter with a narrower passband.

12. The storage medium as defined in claim 10, wherein the GPS satellite signal received by the RF reception circuit section includes signals respectively transmitted from a plurality of satellites;

and wherein the positioning section selects the storage section and acquires and/or tracks the satellite signal from the satellite in units of acquisition and/or tracking target satellites.

13. The storage medium as defined in claim 10, wherein the positioning section includes a switch determination section which determines whether or not to switch the storage section selected, 1) when an acquisition target satellite used for the positioning process has been changed, or 2) each time the positioning process is periodically performed, and selects the storage section determined by the switch determination section after the switch determination section has determined to switch the storage section.

14. The storage medium as defined in claim 13, wherein the switch determination section determines whether or not to switch the storage section subsequently selected based on a signal strength calculated by the coherent accumulation process with a coherent accumulation time corresponding to the selected storage section.

15. The storage medium as defined in claim 14, wherein the switch determination section determines to switch the storage section to the storage section corresponding to the filter with a broader band when the signal strength calculated by the coherent accumulation process with a coherent accumulation time corresponding to the selected storage section satisfies a specific high-strength condition, and determines to switch the storage section to the storage section corresponding to the filter with a narrower band when the signal strength satisfies a specific low-strength condition.