Terminal apparatus, positioning method, control program for terminal apparatus, and computer readable recording medium having recorded therein control program for terminal apparatus

• US 20050253754A1
• Filed: 05/11/2005
• Published: 11/17/2005
• Est. Priority Date: 05/14/2004
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Hayashi, Akifumi, Mizuochi, Shunichi
• Granted Patent: US 7,535,418 B2
• Time in Patent Office: Days
• US Class Current: 342/357.680
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• 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 19/30 code related G01S19/246 takes precedence

Abstract

A terminal apparatus includes a control unit and a positioning device. The control unit determines a first satellite-to-be-acquired from among a plurality of SPS satellites, and generates an initial search frequency for the first satellite-to-be-acquired. The positioning device has a plurality of search units, and is configured to acquire the first satellite-to-be-acquired using the plurality of search units. The control unit determines first difference information, which is a difference between the initial search frequency and the frequency at which the first satellite-to-be-acquired is acquired. The control unit generates corrected search frequencies for other SPS satellites, using the first difference information. The positioning device acquires other necessary SPS satellites using the corresponding corrected search frequencies. The terminal apparatus can acquire SPS satellites accurately even when there has been a frequency shift in the terminal apparatus since the last positioning.

Claims

1. A terminal apparatus that is configured to receive position related information signals from a plurality of SPS satellites, the terminal apparatus comprising:

a control unit configured to determine a first satellite-to-be-acquired from among the plurality of SPS satellites, and to generate a first initial search frequency for the first satellite-to-be-acquired; and

a positioning device having a plurality of search units, the positioning device being configured to acquire the first satellite-to-be-acquired using the plurality of search units,

wherein

the control unit is further configured to determine first difference information, which is a difference between the first initial search frequency and the frequency at which the first satellite-to-be-acquired is acquired,

the control unit is further configured to generate, using the first difference information, corrected search frequencies for at least some of the plurality of SPS satellites excluding the first satellite-to-be-acquired, and

the positioning device is further configured to acquire at least another position information satellite using the corresponding corrected search frequency.

2. The terminal apparatus according to claim 1, wherein

the control unit is further configured to determine a second satellite-to-be-acquired from among the plurality of SPS satellites excluding the first satellite-to-be-acquired,

the control unit is configured to generate a second initial search frequency for the second satellite-to-be-acquired,

the positioning device is configured to acquire the second satellite-to-be-acquired using some of the plurality of search units, and

the control unit is further configured to determine second difference information, which is a difference between the second initial search frequency of the second satellite-to-be-acquire and the frequency at which the second satellite-to-be-acquired is acquired.

3. The terminal apparatus according to claim 2, wherein

the control unit is configured to verify the first difference information by comparing the first and second difference information,

when the first and second difference information is substantially equal, the control unit is further configured to generate, using one of the first and second difference information, corrected search frequencies for at least some of the plurality of SPS satellites excluding the first and second satellites-to-be-acquired, and

the positioning device is further configured to acquire at least another position information satellite using the corresponding corrected search frequency.

4. The terminal apparatus according to claim 2, wherein

the positioning device is configured to set aside some of the search units for tracking the first satellite-to-be-acquired that has been acquired, and

the positioning device is configured to acquire the second satellite-to-be-acquired using all of the remaining search units.

5. The terminal apparatus according to claim 2, wherein

the positioning device is configured to set aside some of the remaining search units for tracking the second satellite-to-be-acquired that has been acquired,

the control unit is configured to determine how many SPS satellites need to be acquired, and

the positioning device is configured to acquire all other SPS satellites that need to be acquired using all of the remaining search units and allocating the remaining search units substantially equally among the SPS satellites that need to be acquired.

6. The terminal apparatus according to claim 1, wherein

the positioning device is configured to set aside some of the remaining search units for tracking the first satellite-to-be-acquired that has been acquired, and

when the tracking of the first satellite-to-be-acquired fails, the control unit is further configured to determine a new first satellite-to-be-acquired.

7. The terminal apparatus according to claim 1, wherein

the positioning device is configured to set aside some of the remaining search units for tracking the first satellite-to-be-acquired that has been acquired,

the control unit is configured to determine how many SPS satellites need to be acquired, and

the positioning device is configured to acquire all other SPS satellites that need to be acquired using all of the remaining search units and allocating the remaining search units substantially equally among the SPS satellites that need to be acquired.

8. A terminal apparatus that is configured to receive position related information signals from a plurality of SPS satellites, the terminal apparatus comprising:

search means for searching SPS satellites with a predetermined search power;

synchronizing frequency information means for determining initial search frequencies of the terminal for each of the plurality of SPS satellites;

first satellite-to-be-acquired determining means that determines a first satellite-to-be-acquired from among the plurality of SPS satellites;

first satellite-to-be-acquired acquiring means that acquires a first satellite-to-be-acquired using the search means with search power;

first difference information obtaining means that obtains first difference information indicating a difference between the initial search frequency of the first satellite-to-be-acquired and a first acquisition frequency at which the first satellite-to-be-acquired is acquired;

means for acquiring sufficient satellites that acquires, using the first difference information, a sufficient number of SPS satellites required for positioning the terminal apparatus; and

positioning means for obtaining position related information from the SPS satellites that have been acquired and locating a present position of the terminal apparatus.

9. The terminal apparatus according to claim 8, further comprising:

second satellite-to-be-acquired determining means that determines a second satellite-to-be-acquired from among the plurality of SPS satellites excluding the first satellite-to-be-acquired;

second satellite-to-be-acquired acquiring means that acquires the second satellite-to-be-acquired; and

second difference information obtaining means that obtains second difference information indicating a difference between the initial search frequency of the second satellite-to-be-acquired and a second acquisition frequency at which the second satellite-to-be-acquired is acquired,

wherein

the means for acquiring sufficient satellites acquires the sufficient number of SPS satellites using the first and second difference information.

10. The terminal apparatus according to claim 9, further comprising

first satellite-to-be-acquired tracking means that tracks the acquired first satellite-to-be-acquired using some of the search power,

wherein

the second satellite-to-be-acquired acquiring means acquires the second satellite-to-be-acquired using all of the remaining search power.

11. The terminal apparatus according to claim 9, further comprising

first satellite-to-be-acquired tracking means that tracks the acquired first satellite-to-be-acquired using some of the search power;

and

second satellite-to-be-acquired tracking means that tracks the acquired second satellite-to-be-acquired using some of the remaining search power,

wherein

the means for acquiring sufficient satellites acquires the sufficient number of SPS satellites with the still remaining search power.

12. The terminal apparatus according to claim 10, wherein

when the first satellite-to-be-acquired tracking means cannot track the acquired first satellite-to-be-acquired, the first satellite-to-be-acquired determining means determines a first satellite-to-be-acquired again.

13. A positioning method for use in a terminal apparatus that is configured to receive position related information signals from a plurality of SPS satellites, the positioning method comprising:

a first satellite-to-be-acquired determining step in which the terminal apparatus determines a first satellite-to-be-acquired from among the plurality of SPS satellites;

a first satellite-to-be-acquired acquiring step in which the terminal apparatus acquires the first satellite-to-be-acquired using a first initial search frequency of the first satellite-to-be-acquired;

a first difference information obtaining step in which the terminal apparatus obtains first difference information, the first difference information indicating a difference between the first initial search frequency of the first satellite-to-be-acquired and a first acquisition frequency at which the first satellite-to-be-acquired is acquired;

a step of acquiring sufficient satellites in which the terminal apparatus acquires, using the first difference information, a sufficient number of SPS satellites required for positioning the terminal apparatus; and

a positioning step in which the terminal apparatus obtains position related information from the SPS satellites that have been acquired and locates a present position of the terminal apparatus.

14. The positioning method according to claim 13, further comprising:

a second satellite-to-be-acquired determining step in which the terminal apparatus determines a second satellite-to-be-acquired from among the plurality of SPS satellites excluding the first satellite-to-be-acquired;

a second satellite-to-be-acquired acquiring step in which the terminal apparatus acquires the second satellite-to-be-acquired using a second initial search frequency of the second satellite-to-be-acquired; and

a second difference information obtaining step in which the terminal apparatus obtains second difference information indicating a difference between the second initial search frequency of the second satellite-to-be-acquired and a second acquisition frequency at which the second satellite-to-be-acquired is acquired,

in the step of acquiring sufficient satellites, the terminal apparatus acquiring, using the first and second difference information, the sufficient number of SPS satellites required for positioning the terminal apparatus.

15. The positioning method according to claim 14, wherein

in the step of acquiring sufficient satellites, the terminal apparatus compares the first and second difference information and acquires the sufficient number of SPS satellites using one of the first and second difference information when the first and second difference information is substantially equal.

16. The positioning method according to claim 14, further comprising

a step of tracking the first satellite-to-be-acquired that is acquired in the first satellite-to-be-acquired acquiring step, using some of search power of the terminal apparatus,

wherein

the terminal executes the second satellite-to-be-acquired acquiring step using all the remaining search power.

17. The positioning method according to claim 14, further comprising

a step of tracking the first satellite-to-be-acquired that is acquired in the first satellite-to-be-acquired acquiring step, using some of search power of the terminal apparatus;

and

a step of tracking the second satellite-to-be-acquired that is acquired in the second satellite-to-be-acquired acquiring step, using some of the remaining search power of the terminal apparatus,

wherein

in the step of acquiring sufficient satellites, the sufficient number of SPS satellites being acquired allocating the remaining search power substantially equally among the number of SPS satellites to be acquired.

18. The positioning method according to claim 13, wherein

in the first satellite-to-be-acquired tracking step, when the first satellite-to-be-acquired cannot be tracked, the terminal apparatus executes the first satellite-to-be-acquired determining step again.

19. A control program for a terminal apparatus that causes a computer to execute the steps of the positioning method set forth in claim 15.

20. A computer readable recording medium having recorded therein the control program for a terminal apparatus as set forth in claim 19.