RFID tag reader/writer

• US 20060220859A1
• Filed: 02/10/2006
• Published: 10/05/2006
• Est. Priority Date: 09/19/2003
• Status: Active Grant

• Current Assignee: Brother Kogyo Kabushiki Kaisha
• Original Assignee: Brother Kogyo Kabushiki Kaisha
• Inventors: Ohashi, Tsuyoshi, Nagai, Takuya, Taki, Kazunari
• Granted Patent: US 8,111,137 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: B41J 3/50 Mechanisms producing characters by printing and also producing a record by other means , e.g. printer combined with RFID writer
• CPC Class Codes: G06K 17/0025 the arrangement consisting of a wireless interrogation device in combination with a device for optically marking the record carrier
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

An RFID tag reader/writer having a high degree of stability of communication with only a desired RFID tag. The frequency of a carrier wave to be transmitted from the RFID tag reader/writer is set on the basis of a resonance frequency of an antenna of the RFID tag located within a predetermined nearby communication area, which resonance frequency changes due to mutual coupling between the antenna of the RFID tag and an antenna of the RFID tag reader/writer. According to this setting, the RFID tag located within the nearby communication area has a high degree of sensitivity, and the RFID tag located outside the nearby communication area has a low degree of sensitivity, so that it is possible to effectively prevent an interference between the communication of the RFID tag reader/writer with the selected RFID tag and the communication of the reader/writer with the other or non-selected RFID tag.

Claims

1. An RFID tag reader/writer communicable with an RFID tag circuit element which has an IC circuit portion storing predetermined information, and an antenna connected to the IC circuit portion and arranged to effect transmission and reception of information, said RFID tag reader comprising:

an access-information generating portion operable to obtain access to RFID tag information of said IC circuit portion, for reading and writing said predetermined information, by communication with said RFID tag circuit element;

a carrier-wave generating portion operable to generate a carrier wave for obtaining access to said RFID tag information of said IC circuit portion;

a carrier-wave modulating portion operable to modulate the carrier wave generated by said carrier-wave generating portion, by using access information generated by said access-information generating portion;

a modulated-wave amplifying portion operable to amplify the carrier wave modulated by said carrier-wave modulating portion; and

an antenna for transmitting an output of said modulated-wave amplifying portion to said IC circuit portion, for obtaining access to said RFID tag information, by non-contact radio communication with said IC circuit portion, by using a radio frequency,

and wherein a frequency of the carrier wave to be generated by said carrier-wave generating portion is set on the basis of a resonance frequency of the antenna of said ratio-tag circuit element located within a predetermined nearby communication area, which resonance frequency changes due to mutual coupling between the antenna of said RFID tag circuit element and the antenna of said RFID tag reader/writer.

2. The RFID tag reader/writer according to claim 1, wherein said nearby communication area is set by setting a spacing distance between the antenna of said RFID tag circuit element and the antenna of said ratio tag reader/writer, to be not larger than 0.1 times a wavelength corresponding to a resonance frequency of the antenna of said RFID tag circuit element when said RFID tag circuit element exists alone, said carrier-wave generating portion generating the carrier wave having a frequency higher than the resonance frequency of the antenna of said RFID tag circuit element when the spacing distance between the antenna of said RFID tag circuit element and the antenna of said RFID tag reader/writer is 0.5 times the wavelength corresponding to the resonance frequency of the antenna of said RFID tag circuit element when said RFID tag circuit element exists alone.

3. The RFID tag reader/writer according to claim 1, which is operable to effect information reading and writing communication with the RFID tag circuit element provided with a half-wave dipole antenna as said antenna, and wherein said nearby communication area is set by setting the spacing distance between the antenna of said RFID tag circuit element and the antenna of said RFID tag reader/writer, to be not larger than 0.05 times a wavelength corresponding to a resonance frequency of the antenna of said RFID tag circuit element when said RFID tag circuit element exists alone, said carrier-wave generating portion generating the carrier wave having a frequency not smaller than 1.03 times the resonance frequency of the antenna of said RFID tag circuit element when said RFID tag circuit element exists alone.

4. The RFID tag reader/writer according to claim 1, wherein said nearby communication area is set by setting the spacing distance between the antenna of said RFID tag circuit element and the antenna of said RFID tag reader/writer, to be within a range between not smaller than 0.2 times and not larger than 0.4 times a wavelength corresponding to a resonance frequency of the antenna of said RFID tag circuit element when said RFID tag circuit element exists alone, said carrier-wave generating portion generating the carrier wave having the resonance frequency of the antenna of said RFID tag circuit element when the spacing distance between the antenna of said RFID tag circuit element and the antenna of said RFID tag reader/writer is within said range.

5. The RFID tag reader/writer according to claim 1, further comprising a mode switching portion operable to place said carrier-wave generating portion in one of a nearby communication mode for communication with said RFID tag circuit element only when said RFID tag circuit element is located within said nearby communication area, and a far communication mode for communication with said RFID tag circuit element when said RFID tag circuit element is located outside said nearby communication area, said carrier-wave generating portion being operable to generate the carrier wave having respective different frequencies when said carrier-wave generating portion is placed in said nearby communication mode and said far communication mode, respectively.

6. An RFID tag reader/writer comprising:

an RFID tag circuit-element accommodating portion for accommodating a plurality of RFID tag circuit elements such that the RFID tag circuit elements can be successively taken out, each of said plurality of RFID tag circuit elements including an IC circuit portion for storing desired information, and a tag-side antenna connected to the IC circuit portion and operable for transmission and reception of information;

an access-information generating portion operable to obtain access to RFID tag information of said IC circuit portion;

a carrier-wave generating portion operable to generate a carrier wave for obtaining access to said RFID tag information of said IC circuit portion;

a carrier-wave modulating portion operable to modulate the carrier wave generated by said carrier-wave generating portion, by using the access information generated by said access-information generating portion;

a modulated-wave amplifying portion operable to amplify the carrier wave modulated by said carrier-wave modulating portion;

a device-side antenna for transmitting an output of said modulated-wave amplifying portion to said IC circuit portion, for obtaining access to said RFID tag information, by non-contact radio communication with said IC circuit portion, by using a radio frequency in a UHF band; and

an RFID tag circuit-element holding portion for holding each of said RFID tag circuit elements successively taken out from said RFID tag circuit-element accommodating portion, in a predetermined accessible area in which said device-side antenna obtains access to said RFID tag information,

and wherein said RFID tag circuit-element accommodating portion is positioned such that said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion is located in an area in which a sensitivity of said device-side antenna is relatively low.

11. The RFID tag reader/writer according to claim 6, wherein said RFID tag circuit-element accommodating portion is positioned such that said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion is located in an area in which an intensity of an electric field of a signal received from said device-side antenna is not larger than one tenth of that at said RFID tag circuit-element holding portion.

12. The RFID tag reader/writer according to claim 6, wherein said RFID tag circuit-element accommodating portion is positioned such that said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion is located in an area in which a radiation directivity of said device-side antenna is almost equal to a lowest value.

21. The RFID tag reader/writer according to claim 6, wherein said RFID tag circuit-element accommodating portion includes a reel member holding a roll of a label material in the form of a tape having said plurality of RFID tag circuit elements successively formed in its longitudinal direction.

22. The RFID tag reader/writer according to claim 6, wherein said RFID tag circuit-element accommodating portion includes a tray member accommodating a stack of a plurality of planar label elements which are laminated on each other and each of which carries one RFID tag circuit element formed thereon.

7. An RFID tag reader/writer comprising:

an RFID tag circuit-element accommodating portion for accommodating a plurality of RFID tag circuit elements such that the RFID tag circuit elements can be successively taken out, each of said plurality of RFID tag circuit elements including an IC circuit portion for storing desired information, and a tag-side antenna connected to the IC circuit portion and operable for transmission and reception of information;

an access-information generating portion operable to obtain access to RFID tag information of said IC circuit portion;

a carrier-wave generating portion operable to generate a carrier wave for obtaining access to said RFID tag information of said IC circuit portion;

a carrier-wave modulating portion operable to modulate the carrier wave generated by said carrier-wave generating portion, by using the access information generated by said access-information generating portion;

a modulated-wave amplifying portion operable to amplify the carrier wave modulated by said carrier-wave modulating portion;

a device-side antenna for transmitting an output of said modulated-wave amplifying portion to said IC circuit portion, for obtaining access to said RFID tag information, by non-contact radio communication with said IC circuit portion, by using a radio frequency in a UHF band; and

an RFID tag circuit-element holding portion for holding each of said RFID tag circuit elements successively taken out from said RFID tag circuit-element accommodating portion, in a predetermined accessible area in which said device-side antenna obtains access to said RFID tag information,

and wherein said device-side antenna is positioned such that a sensitivity of said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion is relatively low.

13. The RFID tag reader/writer according to claim 7, wherein said device-side antenna is positioned such that an intensity of an electric field of a signal which is received by said device-side antenna and which is reflected from said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit element accommodating portion is not larger than one tenth of that of a signal which is received by said device-side antenna and which is reflected from said tag-side antenna of the RFID tag circuit element held by said RFID tag circuit-element holding portion.

14. The RFID tag reader/writer according to claim 7, wherein said device-side antenna is positioned such that an intensity of a radiation directivity of the tag-side antenna of one of the RFID tag circuit elements which is located nearest to an outlet of said RFID tag circuit-element accommodating portion is almost equal to a lowest value.

8. An RFID tag reader/writer comprising:

an RFID tag circuit-element accommodating portion for accommodating a plurality of RFID tag circuit elements such that the RFID tag circuit elements can be successively taken out, each of said plurality of RFID tag circuit elements including an IC circuit portion for storing desired information, and a tag-side antenna connected to the IC circuit portion and operable for transmission and reception of information;

an access-information generating portion operable to obtain access to RFID tag information of said IC circuit portion;

a carrier-wave generating portion operable to generate a carrier wave for obtaining access to said RFID tag information of said IC circuit portion;

a carrier-wave modulating portion operable to modulate the carrier wave generated by said carrier-wave generating portion, by using the access information generated by said access-information generating portion;

a modulated-wave amplifying portion operable to amplify the carrier wave modulated by said carrier-wave modulating portion;

a device-side antenna for transmitting an output of said modulated-wave amplifying portion to said IC circuit portion, for obtaining access to said RFID tag information, by non-contact radio communication with said IC circuit portion, by using a radio frequency in a UHF band; and

an RFID tag circuit-element holding portion for holding each of said RFID tag circuit elements successively taken out from said RFID tag circuit-element accommodating portion, in a predetermined accessible area in which said device-side antenna obtains access to said RFID tag information,

and wherein said RFID tag circuit-element accommodating portion and said device-side antenna are disposed such that a plane of polarization of said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion, and a plane of polarization of said device-side antenna are inclined with respect to each other.

15. The RFID tag reader/writer according to claim 8, wherein said RFID tag circuit-element accommodating portion and said device-side antenna are disposed such that an angle not smaller than 60°

and not larger than 90°

is formed between the plane of polarization of the tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion and the plane of polarization of said device-side antenna.

16. The RFID tag reader/writer according to claim 8, wherein said RFID tag circuit-element accommodating portion and said device-side antenna are disposed such that an angle of about 90°

is formed between the plane of polarization of the tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion and the plane of polarization of said device-side antenna.

17. The RFID tag reader/writer according to claim 8, wherein said RFID tag circuit-element accommodating portion and said RFID tag circuit-element holding portion are disposed such that an angle not smaller than 60°

and not larger than 90°

is formed between the plane of polarization of said tag-side antenna of one of the RFID tag circuit elements which is located at an outlet of said RFID tag accommodating portion and the plane of polarization of said tag-side antenna of one of the RFID tag circuit elements which has already been taken out from said RFID tag circuit-element accommodating portion and which is held by said RFID tag circuit-element holding portion.

18. The RFID tag reader/writer according to claim 17, further comprising a deflecting portion operable to change a direction of feeding of said RFID tag circuit elements, at a position between said outlet and said RFID tag circuit-element holding portion, such that the angle not smaller than 60°

and not larger than 90°

is formed between the plane of polarization of the tag-side antenna of said RFID tag circuit element located at said outlet and the plane of polarization of the tag-side antenna of said RFID tag circuit element held by said RFID tag circuit-element holding portion.

19. The RFID tag reader/writer according to claim 8, wherein said RFID tag circuit-element accommodating portion and said device-side antenna are disposed such that an angle of about 90°

is formed between the plane of polarization of said tag-side antenna of one of the RFID tag circuit elements which is located at an outlet of said RFID tag accommodating portion and the plane of polarization of said tag-side antenna of one of the RFID tag circuit elements which has already been taken out from said RFID tag circuit-element accommodating portion and which is held by said RFID tag circuit-element holding portion.

20. The RFID tag reader/writer according to claim 19, further comprising a deflecting portion operable to change a direction of feeding of said RFID tag circuit elements, at a position between said outlet and said RFID tag circuit-element holding portion, such that the angle of about 90°

is formed between the plane of polarization of the tag-side antenna of said RFID tag circuit element located at said outlet and the plane of polarization of the tag-side antenna of said RFID tag circuit element held by said RFID tag circuit-element holding portion.

9. An RFID tag reader/writer comprising:

an RFID tag circuit-element accommodating portion for accommodating a plurality of RFID tag circuit elements such that the RFID tag circuit elements can be successively taken out, each of said plurality of RFID tag circuit elements including an IC circuit portion for storing desired information, and a tag-side antenna connected to the IC circuit portion and operable for transmission and reception of information;

an access-information generating portion operable to obtain access to RFID tag information of said IC circuit portion;

a carrier-wave generating portion operable to generate a carrier wave for obtaining access to said RFID tag information of said IC circuit portion;

a carrier-wave modulating portion operable to modulate the carrier wave generated by said carrier-wave generating portion, by using the access information generated by said access-information generating portion;

a modulated-wave amplifying portion operable to amplify the carrier wave modulated by said carrier-wave modulating portion;

a device-side antenna for transmitting an output of said modulated-wave amplifying portion to said IC circuit portion, for obtaining access to said RFID tag information, by non-contact radio communication with said IC circuit portion, by using a radio frequency in a UHF band; and

an RFID tag circuit-element holding portion for holding each of said RFID tag circuit elements successively taken out from said RFID tag circuit-element accommodating portion, in a predetermined accessible area in which said device-side antenna obtains access to said RFID tag information,

and wherein said RFID tag circuit-element accommodating portion is positioned such that said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion is located in an area in which a sensitivity of said device-side antenna is relatively low, and

said RFID tag circuit-element accommodating portion and said device-side antenna are disposed such that a plane of polarization of said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion, and a plane of polarization of said device-side antenna are inclined with respect to each other.

10. An RFID tag reader/writer comprising:

an RFID tag circuit-element accommodating portion for accommodating a plurality of RFID tag circuit elements such that the RFID tag circuit elements can be successively taken out, each of said plurality of RFID tag circuit elements including an IC circuit portion for storing desired information, and a tag-side antenna connected to the IC circuit portion and operable for transmission and reception of information;

an access-information generating portion operable to obtain access to RFID tag information of said IC circuit portion;

a carrier-wave generating portion operable to generate a carrier wave for obtaining access to said RFID tag information of said IC circuit portion;

a carrier-wave modulating portion operable to modulate the carrier wave generated by said carrier-wave generating portion, by using the access information generated by said access-information generating portion;

a modulated-wave amplifying portion operable to amplify the carrier wave modulated by said carrier-wave modulating portion;

a device-side antenna for transmitting an output of said modulated-wave amplifying portion to said IC circuit portion, for obtaining access to said RFID tag information, by non-contact radio communication with said IC circuit portion, by using a radio frequency in a UHF band; and

an RFID tag circuit-element holding portion for holding each of said RFID tag circuit elements successively taken out from said RFID tag circuit-element accommodating portion, in a predetermined accessible area in which said device-side antenna obtains access to said RFID tag information,

and wherein said device-side antenna is positioned such that a sensitivity of said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion is relatively low, and

said RFID tag circuit-element accommodating portion and said device-side antenna are disposed such that a plane of polarization of said tag-side antenna of each of the RFID tag circuit elements accommodated in said RFID tag circuit-element accommodating portion, and a plane of polarization of said device-side antenna are inclined with respect to each other.

23. An RFID tag reader/writer comprising:

an RFID tag circuit-element accommodating portion for accommodating a plurality of RFID tag circuit elements such that the RFID tag circuit elements can be successively taken out, each of said plurality of RFID tag circuit elements including an IC circuit portion for storing desired information, and a tag-side antenna connected to the IC circuit portion and operable for transmission and reception of information;

an access-information generating portion operable to generate access information for obtaining access to RFID tag information of said IC circuit portion;

a directional antenna for transmitting said access information generated by said access-information generating portion, to said tag-side antenna, for obtaining access to said RFID tag information of said IC circuit portion, by non-contact radio communication with said tag-side antenna; and

an RFID tag circuit-element holding portion for holding each of said RFID tag circuit elements successively taken out from said RFID tag circuit-element accommodating portion, in a predetermined accessible area in which said directional antenna obtains access to said RFID tag information,

said RFID tag reader/writer being wherein said RFID tag circuit-element holding portion is spaced from said directional antenna in a direction of directivity of the directional antenna, while said RFID tag circuit-element accommodating portion is spaced from said directional antenna in a direction opposite to said direction of directivity.

24. The RFID tag reader/writer according to claim 23, wherein said directional antenna is a micro strip antenna which is provided with a micro strip antenna element on one of opposite sides thereof, and a base plate on the other of said opposite sides.

25. The RFID tag reader/writer according to claim 24, wherein said RFID tag circuit-element holding portion is disposed on the side of said micro strip antenna element, while said RFID tag circuit-element accommodating portion is disposed on the side of said base plate.

26. The RFID tag reader/writer according to claim 24, characterized on that a dimension of said micro strip antenna element in a longitudinal direction of the tag-side antenna of the RFID tag circuit element held in said accessible area is smaller than a dimension of said tag-side antenna in said longitudinal direction.

27. The RFID tag reader/writer according to claim 23, further comprising a shielding portion for reducing an intensity of a radio communication signal, said shielding portion being spaced from said RFID tag circuit-element holding portion in said direction of directivity.

28. The RFID tag reader/writer according to claim 23, further comprising an outlet through which the RFID tag circuit element is fed out of the RFID tag reader/writer after said RFID tag information of said IC circuit portion has been accessed in said accessible area.

29. The RFID tag reader/writer according to claim 28, wherein said outlet is spaced from said directional antenna in a direction substantially perpendicular to said direction of directivity.

30. The RFID tag reader/writer according to claim 28, wherein said outlet is spaced from said directional antenna in a direction in which an electric field intensity of the directional antenna is lower by at least 10 dB than that in said direction of directivity.

31. The RFID tag reader/writer according to claim 24, wherein said base plate has a size larger than a surface area of projection of said RFID tag circuit-element accommodating portion as seen from said micro strip antenna.

32. The RFID tag reader/writer according to claim 24, wherein said base plate has side wall portions extending in a direction toward said RFID tag circuit-element accommodating portion and away from said micro strip antenna element.

33. The RFID tag reader/writer according to claim 32, wherein said base plate is substantially U-shaped.

34. An RFID tag reader/writer comprising:

an RFID tag circuit-element accommodating portion for accommodating a plurality of RFID tag circuit elements such that the RFID tag circuit elements can be successively taken out, each of said plurality of RFID tag circuit elements including an IC circuit portion for storing desired information, and a tag-side antenna connected to the IC circuit portion and operable for transmission and reception of information;

an access-information generating portion operable to generate access information for obtaining access to RFID tag information of said IC circuit portion;

a directional antenna for transmitting said access information generated by said access-information generating portion, to said tag-side antenna, for obtaining access to said RFID tag information of said IC circuit portion, by non-contact radio communication with said tag-side antenna;

an RFID tag circuit-element holding portion for holding each of said RFID tag circuit elements successively taken out from said RFID tag circuit-element accommodating portion, in a predetermined accessible area in which said directional antenna obtains access to said RFID tag information; and

a shielding portion for reducing an intensity of a radio communication signal,

said RFID tag reader/writer being wherein;

said RFID tag circuit-element holding portion is spaced from said directional antenna in a direction of directivity of the directional antenna;

said shielding portion is spaced from said RFID tag circuit-element holding portion in the direction of directivity of said directional antenna; and

said RFID tag circuit-element accommodating portion is spaced from said shielding portion in the direction of directivity of said directional antenna.

35. The RFID tag reader/writer according to claim 34, wherein a spacing distance between said shielding portion and said holding portion is larger than a spacing distance between said directional antenna and said holding portion.

36. The RFID tag reader/writer according to 34, wherein said directional antenna is a micro strip antenna which is provided with a micro strip antenna element on one of opposite sides thereof, and a base plate on the other of said opposite sides.

37. The RFID tag reader/writer according to 36, wherein said RFID tag circuit-element holding portion is disposed on the side of said micro strip antenna element, while a reflecting plate for reflecting the communication signal is disposed on the side of said base plate.

38. The RFID tag reader/writer according to claim 36, wherein a dimension of said micro strip antenna element in a longitudinal direction of the tag-side antenna of the RFID tag circuit element held in said accessible area is smaller than a dimension of said tag-side antenna in said longitudinal direction.

39. The RFID tag reader/writer according to claim 34, wherein said RFID tag circuit-element accommodating portion is removably installed on a main body of the RFID tag reader/writer, and said shielding portion is disposed on the main body of the RFID tag reader/writer.

40. The RFID tag reader/writer according to claim 34, further comprising an outlet through which the RFID tag circuit element is fed out of the RFID tag reader/writer after said RFID tag information of said IC circuit portion has been accessed in said accessible area.

41. The RFID tag reader/writer according to claim 40, wherein said outlet is spaced from said directional antenna in a direction substantially perpendicular to said direction of directivity.

42. The RFID tag reader/writer according to claim 40, wherein said outlet is spaced from said directional antenna in a direction in which an electric field intensity of the directional antenna is lower by at least 10 dB than that in said direction of directivity.

43. The RFID tag reader/writer according to claim 34, wherein said shielding portion is a planar member having a size larger than a surface area of projection of said RFID tag circuit-element accommodating portion as seen from said shielding portion.

44. The RFID tag reader/writer according to claim 34, wherein said shielding portion has side wall portions extending in a direction toward said RFID tag circuit-element accommodating portion and away from said micro strip antenna element.

45. The RFID tag reader/writer according to claim 44, wherein said shielding portion is substantially U-shaped.