Radio-Frequency Device, And Radio-Frequency Tag Communication Device

• US 20070279277A1
• Filed: 06/08/2007
• Published: 12/06/2007
• Est. Priority Date: 12/13/2004
• Status: Active Grant

• Current Assignee: Brother Kogyo Kabushiki Kaisha
• Original Assignee: Brother Kogyo Kabushiki Kaisha
• Inventors: Ohashi, Tsuyoshi, Taki, Kazunari, Kuramoto, Katsuyuki
• Granted Patent: US 8,169,367 B2
• Time in Patent Office: Days
• US Class Current: 342/147
• CPC Class Codes: H01Q 19/30 the primary active element being centre-fed and substantially straight, e.g. Yagi antenna
• CPC Class Codes: H01Q 3/04 for varying one co-ordinate of the orientation
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming

Abstract

A radio-frequency device includes a PAA processing portion configured to control a directivity of reception of a receiver antenna device, a received-signal-strength detecting portion configured to detect a strength of the received signal received by the receiver antenna device, and a direction detecting portion configured to detect the direction toward the communication object, on the basis of a direction in which a higher one of two strength values of the received signal respectively detected in first and second maximum-reception-directivity directions of a predetermined angular difference established by the PAA processing portion is minimal. The direction detecting portion is operated based on a fact that the received signal strength is minimal at the bottom of a gain existing in an area of overlapping of two main lobes extending in the respective two directivity directions of the predetermined angular difference, so that the resolution of detection can be made higher than in the case based on the main lobe direction in which the sensitivity of communication with the radio-frequency tag is maximum. Accordingly, the direction toward the radio-frequency tag can be suitably detected.

Claims

1. A radio-frequency device including a receiver antenna device for receiving a received signal from a desired communication object, and configured to detect a direction in which said communication object is located, on the basis of the received signal received by said receiver antenna device, said radio-frequency device comprising:

a reception-directivity control portion configured to control a directivity of reception of said receiver antenna device;

a received-signal-strength detecting portion configured to detect a strength of the received signal received by said receiver antenna device; and

a direction detecting portion configured to detect the direction in which said communication object is located, on the basis of a direction in which a higher one of two strength values of the received signal respectively detected in first and second maximum-reception-directivity directions of a predetermined angular difference established by said reception-directivity control portion is minimal.

2. The radio-frequency device according to claim 1, wherein said direction detecting portion is configured to effect, prior to said detection, preliminary detection to detect the direction toward the communication object, on the basis of a direction in which a highest value of the strength of the received signal is detected by said received-signal-strength detecting portion as the maximum-reception-directivity direction in which said directivity of reception is highest is changed at a predetermined angular interval.

3. The radio-frequency device according to claim 2, wherein said direction detecting portion is configured to determine initial values of said first and second maximum-reception-directivity directions on the basis of the direction toward the communication object as detected in said preliminary detection.

4. The radio-frequency device according to claim 1, wherein said direction detecting portion is configured to repeat said detection as said first and second maximum-reception-directivity directions are changed at a predetermined angular interval.

5. The radio-frequency device according to claim 1, wherein said receiver antenna device consists of at least two antenna elements.

6. The radio-frequency device according to claim 5, wherein said receiver antenna device is an array antenna device having at least two antenna elements.

7. The radio-frequency device according to claim 1, further comprising a received-signal memory portion for storing the received signals received by said receiver antenna device.

8. The radio-frequency device according to claim 1, wherein said direction detecting portion is configured to compensate an angle formed between said first and second maximum-reception-directivity directions such that the angle formed between the first and second maximum-reception-directivity directions increases with an increase of an angle formed between a reference direction and a predetermined original direction that are used for determining the first and second maximum-reception-directivity directions.

9. The radio-frequency device according to claim 1, further comprising a transmitter antenna device for transmitting a predetermined signal to said communication object.

10. The radio-frequency device according to claim 9, wherein said reception-directivity control portion is configured to set an initial value of the directivity of reception of said receiver antenna device such that said initial value corresponds to a direction in which a directivity of transmission of the signal to be transmitted from said transmitter antenna device is maximum.

11. The radio-frequency device according to claim 9, further comprising a transmission-directivity control portion configured to control a directivity of transmission of the signal to be transmitted from said transmitter antenna device.

12. The radio-frequency device according to claim 11, wherein said transmission-directivity control portion is configured to control said directivity of transmission independently of said directivity of reception.

13. The radio-frequency device according to claim 11, wherein said transmission-directivity control portion is configured to control said directivity of transmission such that the directivity of transmission is coincident with said directivity of reception.

14. The radio-frequency device according to claim 11, wherein said transmission-directivity control portion is configured to control said directivity of transmission such that the controlled directivity of transmission is aligned with a direction of a centerline between said first and second maximum-reception-directivity directions.

15. A radio-frequency tag communication device including an antenna device and configured to transmit a transmitted signal toward a radio-frequency tag and receive a reply signal transmitted from the radio-frequency tag in response to the transmitted signal, for thereby effecting radio communication with the radio-frequency tag, said radio-frequency tag communication device comprising:

an attitude sensor device configured to detect an attitude of said antenna device in a predetermined coordinate system; and

a directivity control portion configured to control a directivity of communication with the radio-frequency tag, according to the attitude detected by said attitude sensor device.

16. The radio-frequency tag communication device according claim 15, which is a portable device movable in a predetermined area.

17. The radio-frequency tag communication device according to claim 15, wherein said attitude sensor device includes an inclination sensor configured to detect an angle of inclination of said antenna device with respect to a gravity direction.

18. The radio-frequency tag communication device according to claim 15, wherein said attitude sensor device includes an azimuth sensor configured to detect an angle of inclination of said antenna device with respect to a geomagnetic direction.

19. The radio-frequency tag communication device according to claim 15, wherein said directivity control portion is configured to control the directivity of communication such that the controlled directivity of communication is maximized in a predetermined one direction.

20. The radio-frequency tag communication device according to claim 15, wherein said directivity control portion is configured to control the directivity of communication such that the controlled directivity of communication is maximized in a selected one of a plurality of predetermined directions.

21. The radio-frequency tag communication device according to claim 15, further comprising a selector device configured to selectively enable or disable said directivity control portion to control the directivity of communication.

22. The radio-frequency tag communication device according to claim 15, wherein said antenna device includes a plurality of antenna elements commonly used to transmit said transmitted signal and receive said reply signal.

23. The radio-frequency tag communication device according to claim 22, wherein said plurality of antenna elements include at least three antenna elements having a directivity of communication in a predetermined one direction.

24. The radio-frequency tag communication device according to claim 22, wherein said antenna device includes five antenna elements the directivity of which is controllable with respect to a gravity direction and a geomagnetic direction, said five antenna elements including one antenna element commonly used for said gravity and geomagnetic directions.

25. The radio-frequency tag communication device according to claim 21, which is a portable device comprising a display portion configured to display images relating to the communication with the radio-frequency tag, and a holder portion at which the radio-frequency tag communication device is held for carrying, said display portion and said holder portion being hinged to each other pivotally foldably, and wherein said selector device is disposed on said holder portion.

26. The radio-frequency tag communication device according to claim 21, which is capable of writing desired information on said radio-frequency tag, and wherein said selector device enables the directivity control portion to control the directivity of communication upon writing of the desired information on said radio-frequency tag.

27. A radio-frequency tag communication device configured to transmit an interrogating wave toward a desired radio-frequency tag and to receive a reply wave transmitted from the radio-frequency tag, for thereby effecting radio communication with the radio-frequency tag, said radio-frequency tag communication device comprising:

a directivity control portion configured to change a directivity of transmission of said interrogating wave during a period between moments of initiation and termination of transmission of a unit portion of the interrogating wave, which unit portion permits the radio communication with the radio-frequency tag.

28. The radio-frequency tag communication device according to claim 27, wherein said directivity control portion changes the directivity of transmission of the interrogating wave during the period between the moments of initiation and termination of transmission of the unit portion of the interrogating wave, such that effective areas of communication corresponding to the directivity of transmission before and after a change of the directivity of communication partially overlap each other.

29. The radio-frequency tag communication device according to claim 28, wherein said directivity control portion changes the directivity of transmission such that an overlapping area of communications before and after the change of the directivity of transmission is narrower than a sum of the effective area of communication corresponding to the directivity of transmission before said change and the effective area of communication corresponding to the directivity of transmission after said change.

30. The radio-frequency tag communication device according to claim 28, wherein said directivity control portion is capable of changing an overlapping area of communications before and after the change of the directivity of transmission.

31. The radio-frequency tag communication device according to claim 27, wherein said interrogating wave includes a command portion including a command for radio communication with the radio-frequency tag, and a non-command portion not including said command.

32. The radio-frequency tag communication device according to claim 31, wherein said directivity control portion changes the directivity of transmission of said interrogating wave during the period between the moments of initiation and termination of transmission of said command portion.

33. The radio-frequency tag communication device according to claim 31, wherein said directivity control portion changes the directivity of transmission of said interrogating wave during a period of initiation and termination of transmission of said non-command portion, after the transmission of said command portion.

34. The radio-frequency tag communication device according to claim 31, wherein said directivity control portion changes the directivity of transmission of said interrogating wave at a moment of switching from the transmission of said command portion to the transmission of said non-command portion.

35. The radio-frequency tag communication device according to claim 27, wherein said directivity control portion changes the directivity of transmission of said interrogating wave when a predetermined time has passed after the moment of termination of said unit portion of the interrogating wave.

36. The radio-frequency tag communication device according to claim 27, wherein said directivity control portion changes a direction of a main lobe of the directivity of transmission of said interrogating wave, during the period between the moments of initiation and termination of said unit portion of the interrogating wave.

37. The radio-frequency tag communication device according to claim 27, wherein said directivity control portion changes a characteristic of directivity of transmission of said interrogating wave during the period between the moments of initiation and termination of transmission of said unit portion of the interrogating wave.

38. The radio-frequency tag communication device according to claim 27, which is configured to change an electric energy of transmission of said interrogating wave during the period between the moments of initiation and termination of transmission of said unit portion of the interrogating wave.

39. The radio-frequency tag communication device according to claim 27, wherein said directivity control portion changes the directivity of transmission of said interrogating wave during the period between the moments of initiation and termination of transmission of said unit portion of the interrogating wave, such that directions in which the directivity of transmission is maximum before and after a change of the directivity of transmission are symmetrical with each other with respect to an axis indicative of a predetermined reference direction.

40. The radio-frequency tag communication device according to claim 39, wherein said predetermined reference direction is a direction of a man lobe of a directivity of reception of said reply wave transmission from the radio-frequency tag in response to said interrogating wave.

41. The radio-frequency tag communication device according to claim 27, wherein said directivity control portion changes the directivity of transmission of said interrogating wave during the period between the moments of initiation and termination of transmission of said unit portion of the interrogating wave, such that directions in which the directivity of transmission is maximum before and after a change of the directivity of transmission are symmetrical with each other with respect to an axis indicative of a predetermined reference direction, said directivity control portion changing said reference direction each time the interrogating wave is transmitted toward said radio-frequency tag.

42. The radio-frequency tag communication device according to claim 39, wherein said directivity control portion changes the directivity of transmission of said interrogating wave after a moment of initiation of reception of said reply wave from said radio-frequency tag in response to said interrogating wave, such that a direction of a man lobe of the directivity of transmission is parallel to said predetermined reference direction.

43. The radio-frequency tag communication device according to claim 28, wherein said directivity control portion changes the directivity of transmission of said interrogating wave after a moment of initiation of reception of said reply wave from said radio-frequency tag in response to said interrogating wave, such that a main lobe of the directivity of transmission is substantially coincident with the overlapping area of communications before and after the change of the directivity of transmission.

44. The radio-frequency tag communication device according to claim 27, wherein said directivity control portion changes the directivity of transmission of said interrogating wave such that an area of overlapping of main lobes of the directivity of transmission before and after a change of the directivity of transmission of said unit portion of the interrogating wave is narrowed each time the interrogating wave is transmitted toward said radio frequency tag.