Distance Measuring Apparatus, Distance Measuring Method, Reflector and Communication System

• US 20080150699A1
• Filed: 09/01/2005
• Published: 06/26/2008
• Est. Priority Date: 03/09/2005
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Ohara, Hideyuki, Kawai, Takehiro, Saito, Keisuke, Hayama, Kosuke
• Granted Patent: US 7,649,491 B2
• Time in Patent Office: Days
• US Class Current: 340/10.4
• CPC Class Codes: G01S 13/38 wherein more than one modulation frequency is used
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement
• CPC Class Codes: H04B 17/27 for locating or positioning the transmitter
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A transmission controller 7B is configured to transmit an R/W request signal for requesting transmission of a tag response signal to a RFID tag 1 twice. At this time, a frequency controller 7A controls a PLL section 5A to transmit the R/W request signal via different carrier frequencies. A phase information acquirer 8A detects a phase change amount of the tag response signal that is transmitted via different carrier frequencies. A distance calculator 8B calculates the distance between the reader/writer 2 and the RFID tag 1 on the basis of the phase change amount.

Claims

1. A distance measuring apparatus, comprising:

a transmitter, that transmits a request signal from an antenna to the outside via radio waves having a plurality of different carrier frequencies;

a receiver, that receives a reflection signal which is a signal composed of one frame and is obtained when the request signal transmitted from the transmitter is reflected by a reflector while being modulated;

a phase information acquirer, that calculates an amount of phase change between the reflection signal received by the receiver and the request signal for each of the carrier frequencies transmitted from the transmitter; and

a distance calculator, that calculates a distance between the antenna and the reflector on the basis of the carrier frequencies and the phase change amount for each of the carrier frequencies acquired by the phase information acquirer, wherein;

the reflection signal is transmitted from the reflector via three or more different carrier frequencies; and

the phase information acquirer acquires the phase change amount by selecting signals of two carrier frequencies having signal states which satisfy a prescribed criterion for calculating the distance, from signals of the carrier frequencies.

2. The distance measuring apparatus as set forth in claim 1, wherein:

the transmitter sets a plurality of divided periods in a period for transmitting one request signal, and controls such that the different carrier frequencies are used for the respective divided periods.

3. The distance measuring apparatus as set forth in claim 1, wherein:

the transmitter transmits the request signal via one of the carrier frequencies composed of different carrier frequency components.

4. The distance measuring apparatus as set forth in claim 1, wherein:

the request signal is a signal composed of one frame; and

the reflection signal is a signal composed of one frame and including a preamble section.

5. The distance measuring apparatus as set forth in claim 1, further comprising:

a frequency converter, that performs a frequency conversion processing with respect to the reflection signal received, wherein;

the frequency converter converts the reflection signal to an I signal and a Q signal.

6. The distance measuring apparatus as set forth in claim 1, wherein:

the distance calculator calculates the distance with high-resolution spectrum analysis.

7. The distance measuring apparatus as set forth in claim 6, wherein:

the distance calculator utilizes a MUSIC (MUltiple Signal Classification) method as the high-resolution spectrum analysis, in which the reflection signal received via the different carrier frequencies is used as an input, an MUSIC evaluation function is obtained using a mode vector as a function of the distance, and the distance is calculated by obtaining peak values of the MUSIC evaluation function.

8. The distance measuring apparatus as set forth in claim 1, wherein:

the distance calculator calculates the distance also on the basis of a reception intensity of the reflection signal received.

9. The distance measuring apparatus as set forth in claim 1, further comprising:

a reception controller, that acquires information in a data section of the reflection signal, and outputs, to the outside, the distance calculated by the distance calculator which is associated with the information in the data section.

10. The distance measuring apparatus as set forth in claim 1, wherein:

the distance calculator measures a direction that the reflector that has transmitted the reflection signal is located, on the basis of the reflection signal.

11. The distance measuring apparatus as set forth in claim 1, wherein:

the distance calculator calculates the distance by analyzing a signal in a preamble section of the reflection signal.

18. The distance measuring method as set forth in claim 6 wherein:

the distance calculator utilizes a MUSIC (Multiple Signal Classification) method as the high-resolution spectrum analysis, in which the reflection signal received via the different carrier frequencies is used as an input, an MUSIC evaluation function is obtained using a mode vector as a function of the distance, and the distance is calculated by obtaining peak values of the MUSIC evaluation function.

26. A communication system, comprising:

the distance measuring apparatus as set forth in any one of claims 1 to 3 and 5 to 11; and

at least one reflector that performs wireless communication with the distance measuring apparatus.

27. A communication system, comprising:

the distance measuring apparatus as set forth in any one of claims 1 to 3 and 5 to 11; and

a management apparatus, that manages at least one of articles, people, and living things that are associated with the reflectors on the basis of a communication result between the distance measuring apparatus and the reflectors.

12. A distance measuring method, comprising:

a transmitting step of transmitting a request signal from an antenna to the outside via radio waves having a plurality of different carrier frequencies;

a receiving step of receiving a reflection signals which is obtained when the request signal transmitted in the transmitting step is reflected from a reflector while being modulated;

a phase information acquisition step of calculating an amount of phase change between the reflection signal received in the receiving step and the request signal for each of the carrier frequencies transmitted in the transmitting step; and

a distance calculating step of calculating a distance between the antenna and the reflector on the basis of the carrier frequencies and the phase change amount for each of the carrier frequencies acquired in the phase information acquiring step, wherein;

the reflection signal is transmitted from the reflector via three or more different carrier frequencies; and

the phase information acquirer acquires the phase change amount by selecting signals of two carrier frequencies having signal states which satisfy a prescribed criterion for calculating the distance, from signals, of the carrier frequencies.

13. The distance measuring method as set forth in claim 12, wherein:

the transmitting step is configured to set a plurality of divided periods in a period for transmitting one request signal, and to control such that the different carrier frequencies are used for the respective divided periods.

14. The distance measuring method as set forth in claim 12, wherein:

the transmitting step is configured to transmit the request signal via one of the carrier frequencies composed of different carrier frequency components.

15. The distance measuring method as set forth in claim 12, wherein:

the request is a signal composed of one frame; and

the reflection signal is a signal composed of one frame and including a preamble section.

16. The distance measuring method as set forth in claim 12, further comprising:

a frequency converting step of performing a frequency conversion processing with respect to the reflection signal received, wherein;

the frequency converting step converts the reflection signals to an I signal and a Q signal.

17. The distance measuring method as set forth in claim 12, wherein:

the distance calculating step calculates the distance with high-resolution spectrum analysis.

19. The distance measuring method as set forth in claim 12, wherein:

the distance calculating step calculates the distance on the basis of a reception intensity of the reflection signal received.

20. The distance measuring method as set forth in claim 12, further comprising:

a reception control step of acquiring information in a data section of the reflection signal, and outputting, to the outside, the distance calculated by the distance calculator which is associated with the information in the data section.

21. The distance measuring method as set forth in claim 12, wherein:

the distance calculating step measures a direction that the reflector that has transmitted the reflection signal is located, on the basis of the reflection signal.

22. The distance measuring method as set forth in claim 12, wherein:

the distance calculating step calculates the distance by analyzing a signal in a preamble section of the request signal.

23-25. -25. (canceled)