Position detection system and position detection method

• US 10,371,789 B2
• Filed: 11/02/2017
• Issued: 08/06/2019
• Est. Priority Date: 05/07/2015
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Takizawa, Koichi
• Primary Examiner(s): Hu, Jinsong
• Assistant Examiner(s): Madani, Farideh
• Application Number:
  US15/801,723
• Publication Number:
  US 20180143288A1
• Time in Patent Office: 642 Days
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A mobile station transmits a first radio signal, a reference station transmits a second radio signal. Fixed stations extract phase differences (Δφmf1) to (Δφmf3), respectively, between a carrier included in the first radio signal and reference clocks of the respective fixed stations. The fixed stations extract phase differences (Δφsf1) to (Δφsf3), respectively, between a carrier included in the second radio signal and the reference clocks of the respective fixed stations. A server cancels phase offsets (φf1) to (φf3) of the respective fixed stations using phase difference information between the mobile station and each of the fixed stations and phase difference information between the reference station and each of the fixed stations, obtains distance information between each of the fixed stations and the mobile station, and calculates a position of the mobile station.

Claims

1. A position detection system comprising:

a mobile station having a mobile station reference clock circuit, a radio signal transmission circuit, and a transmission antenna;

a reference station having a reference station reference clock circuit, a radio signal transmission circuit, and a transmission antenna; and

at least three or more fixed stations each having a fixed station reference clock circuit, a radio signal reception circuit, and a reception antenna, wherein

the fixed station reference clock circuits of the three or more fixed stations each asynchronously and independently operate and generate reference clocks with same frequency as one another,

the mobile station intermittently transmits at least one first radio signal based on a reference clock of the mobile station reference clock circuit,

the reference station is disposed at a predetermined position and intermittently transmits at least one second radio signal based on a reference clock of the reference station reference clock circuit,

each of the fixed stations receives the first radio signal and extracts a phase difference between a carrier included in the first radio signal and each of the reference clocks of each of the fixed stations, receives the second radio signal and extracts a phase difference between a carrier included in the second radio signal and each of the reference clocks of each of the fixed stations,

a phase offset of the reference clock of each of the fixed stations is canceled using phase difference information between the mobile station and each of the fixed stations and phase difference information between the reference station and each of the fixed stations, distance information between each of the fixed stations and the mobile station is obtained, and a position of the mobile station is calculated.

2. The position detection system according to claim 1, wherein

the mobile station transmits a trigger radio signal in order for the reference station to transmit the second radio signal,

the reference station has a radio signal reception circuit and a reception antenna, and

the reference station transmits the second radio signal when receiving the trigger radio signal transmitted by the mobile station.

3. The position detection system according to claim 1, wherein

at least one of the mobile station reference clock circuit of the mobile station and the reference station reference clock circuit of the reference station generates a reference clock with the same frequency as a frequency of each of the fixed station reference clock circuits of each of the fixed stations.

4. The position detection system according to claim 2, wherein

the mobile station transmits the trigger radio signal and the first radio signal with a predetermined time gap.

5. The position detection system according to claim 1, wherein

at least one fixed station of the three or more fixed stations also includes a function of the reference station and transmits the second radio signal.

6. The position detection system according to claim 1, wherein

the mobile station reference clock circuit of the mobile station has a function of generating reference clocks with two or more frequencies, and

the mobile station transmits the first radio signals with two or more types of carrier frequencies.

7. The position detection system according to claim 6, wherein

the reference station transmits the second radio signals with two or more types of carrier frequencies being the same as the carrier frequencies of the mobile station.

8. A position detection method using a position detection system,

the position detection system including:

a mobile station having a mobile station reference clock circuit, a radio signal transmission circuit, and a transmission antenna;

a reference station having a reference station reference clock circuit, a radio signal transmission circuit, and a transmission antenna; and

at least three or more fixed stations each having a fixed station reference clock circuit, a radio signal reception circuit, and a reception antenna,

the position detection method comprising;

asynchronously and independently operating each of the fixed station reference clock circuits of the three or more fixed stations to generate reference clocks with same frequency as one another;

intermittently transmitting at least one first radio signal based on a reference clock of the mobile station reference clock circuit in the mobile station;

disposing the reference station at a predetermined position and intermittently transmitting at least one second radio signal based on a reference clock of the reference station reference clock circuit;

in each of the fixed stations, receiving the first radio signal and extracting a phase difference between a carrier included in the first radio signal and each of the reference clocks of each of the fixed stations, receiving the second radio signal and extracting a phase difference between a carrier included in the second radio signal and each of the reference clocks of each of the fixed stations; and

canceling a phase offset of the reference clock of each of the fixed stations using phase difference information between the mobile station and each of the fixed stations and phase difference information between the reference station and each of the fixed stations, obtaining distance information between each of the fixed stations and the mobile station, and calculating a position of the mobile station.

9. The position detection method according to claim 8, wherein

the mobile station transmits a trigger radio signal in order for the reference station to transmit the second radio signal,

the reference station has a radio signal reception circuit and a reception antenna, and

the reference station transmits the second radio signal when receiving the trigger radio signal transmitted by the mobile station.

10. The position detection method according to claim 8, wherein

at least one of the mobile station reference clock circuit of the mobile station and the reference station reference clock circuit of the reference station generates a reference clock with the same frequency as a frequency of each of the fixed station reference clock circuits of each of the fixed stations.

11. The position detection method according to claim 9, wherein

the mobile station transmits the trigger radio signal and the first radio signal with a predetermined time gap.

12. The position detection method according to claim 8, wherein

at least one fixed station of the three or more fixed stations also includes a function of the reference station and transmits the second radio signal.

13. The position detection method according to claim 8, wherein

the mobile station reference clock circuit of the mobile station has a function of generating reference clocks with two or more frequencies, and

the mobile station transmits the first radio signals with two or more types of carrier frequencies.

14. The position detection method according to claim 13, wherein

the reference station transmits the second radio signals with two or more types of carrier frequencies being the same as the carrier frequencies of the mobile station.