# US 10,371,789 B2 · Position detection system and position detection method

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- Number: US 10,371,789 B2
- Document ID: US10371789B2
- Status: Granted
- Kind: B2
- Application number: 15/801,723
- Filed: 2017-11-02
- Published: 2018-05-24
- Granted: 2019-08-06
- Earliest claimed: 2015-05-07
- Assignees: Murata Manufacturing Co., Ltd.
- Applicants: Murata Manufacturing Co., Ltd.
- Inventors: Koichi Takizawa
- Web page: https://patentgrep.com/patent/US10371789B2

## CPC

- G01S 5/06: Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence)
- G01S 5/0036: {of measured values, i.e. measurement on mobile and position calculation on base station}
- G01S 5/021: {Calibration, monitoring or correction (G01S5/0252 takes precedence)}
- G01S 5/02216: {Timing or synchronisation of the receivers}
- G01S 5/14: Determining absolute distances from a plurality of spaced points of known location
- H04W 64/00: Locating users or terminals {or network equipment} for network management purposes, e.g. mobility management
- H04W 4/02: Services making use of location information
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## 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

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 2)

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.

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 6)

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.

### Claim 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.

### Claim 9 (depends on 8)

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.

### Claim 10 (depends on 8)

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.

### Claim 11 (depends on 9)

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.

### Claim 12 (depends on 8)

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.

### Claim 13 (depends on 8)

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.

### Claim 14 (depends on 13)

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.