Antenna for reader/writer and reader/writer having the antenna

• US 7,495,625 B2
• Filed: 01/17/2003
• Issued: 02/24/2009
• Est. Priority Date: 01/17/2002
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Materials Corporation
• Original Assignee: Mitsubishi Materials Corporation
• Inventors: Yahata, Seirou, Endo, Takanori, Tsuchida, Takashi
• Primary Examiner(s): Ho; Tan
• Application Number:
  US10/500,457
• Publication Number:
  US 20050162331A1
• Time in Patent Office: 2,230 Days
• Field of Search: 343/741, 343/742, 343/866, 343/788, 343/895, 340/572.5, 340/572.6
• US Class Current: 343/788
• CPC Class Codes: G06K 19/07771 the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 1/52 Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure absorbing means H01Q17/00
• CPC Class Codes: H01Q 7/06 with core of ferromagnetic material H01Q7/02 takes precedence

Abstract

A soft magnetic member which is formed by a composite of an organic object to satisfy a predetermined relationship with an antenna area, a circumference length, and a magnetic transmission ratio and a conductive member are provided between an antenna coil which is formed by at least one loop and a metal surface of the conductive member such as a metal casing. The magnetic flux which invades into the conductive object is blocked by the soft magnetic member and the conductive member so as to restrict the influence thereof.

Claims

1. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface;

an antenna coil which is formed by at least one turn and disposed on the soft magnetic member; and

a conductive member disposed on said soft magnetic member on an opposite side of a placement of the antenna coil,

wherein an object with said reader/writer antenna affixed thereon is a metal member or a member which contains the metal member.

2. A reader/writer antenna according to claim 1 wherein the antenna coil is wound in a spiral manner.

3. A reader/writer antenna according to claim 1 wherein the soft magnetic member is formed to contact a part of an antenna coil surface defined planarly by the one turn of the antenna coil so that a magnetic flux which is generated by the antenna coil is formed asymmetrically with reference to a center axis of the antenna coil.

4. A reader/writer antenna according to claim 1 wherein the soft magnetic member is a compound of either a metal powder, a flake or a ferrite powder, which are formed by flattening a metal powder.

5. A reader/writer antenna according to any of claims 1-3, wherein the soft magnetic member is one of an amorphous alloy, a permalloy, a magnetic steel, a silicon steel, a sendust alloy, a Fe—

AL alloy, or a soft magnetic ferrite.

6. A reader/writer antenna according to claim 1 wherein the soft magnetic member is an amorphous film or a layered member of an amorphous film.

7. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface; and

an antenna coil which is formed by at least one turn and is disposed on the soft magnetic member,

wherein a thickness t for the soft magnetic member or a magnetic core for forming a plate satisfies a relationship S/L>

t>

S/(L/μ

) under condition that S indicates an area for the antenna coil, L indicates a circumferential length of the antenna coil, and μ

indicates a magnetic transmittance ratio of the soft magnetic member or the magnetic core.

8. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface; and

an antenna coil which is formed by at least one turn and disposed on the soft magnetic member,

wherein the soft magnetic member is a compound of either a metal powder, a flake or a ferrite powder, which are formed by flattening a metal powder,

wherein the metal powder is one of a carbonyl iron powder, a reduced iron powder, an atomized powder, or an amorphous powder, and

the reader/writer antenna is configured to be disposed so as to contact a casing which is formed by a non-magnetic member which has an initial resistance of approximately 10×

10<sup>−

8</sup> Ω

m or lower.

9. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface; and

an antenna coil which is formed by at least one turn and disposed on the soft magnetic member,

wherein the soft magnetic member is a compound of either a metal powder, a flake or a ferrite powder, which are formed by flattening a metal powder,

wherein the metal powder or the flake is made by flattening a water-atomized iron base alloy or an iron base alloy powder mechanically, and

the reader/writer antenna is configured to be disposed so as to contact a casing which is formed by a non-magnetic member which has an initial resistance of approximately 10×

10<sup>−

8</sup> Ω

m or lower.

10. A reader/writer antenna according to claim 9 wherein the iron base alloy contains 6 w % to 15 w % of silicon.

11. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magentic member configured to be disposed on a surface; and

an antenna coil which is formed by at least one turn and disposed on the soft magnetic member,

wherein the soft magnetic member is a compound of either a metal powder, a flake or a ferrite powder, which are formed by flattening a metal powder,

wherein the metal powder or the flake is made by flattening a water-atomized iron base alloy or an iron base alloy powder mechanically, and

the iron base alloy contains at least approximately 1 w % of aluminum or lower, approximately 3 w % of nickel or copper or lower, approximately 5 w % of chromium or lower, approximately 10 w % of cobalt or lower in addition to approximately 6 w % to 15 w % of silicon.

12. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface; and

an antenna coil which is formed by at least one turn and disposed on the soft magnetic member,

wherein the soft magnetic member is a compound of either a metal powder, a flake or a ferrite powder, which are formed by flattening a metal powder, and

wherein the compound is an injection molded member, a compressed molded member, a rolled stripped member, or a member to which a painting member is applied.

13. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface of an object; and

an antenna coil which is formed by at least one turn and is disposed on the soft magnetic member,

wherein a non-magnetic conductive member of which resistivity is approximately 10×

10<sup>−

8</sup>Ω

m or lower or a conductive member of which resistivity is approximately 3×

10<sup>−

8</sup>Ω

m is configured to be disposed between the soft magnetic member and the object.

14. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface of an object; and

an antenna coil which is formed by at least one turn and is disposed on the soft magnetic member,

wherein a non-magnetic conductive member has a 0.015 Ω

resistance or lower with 1 cm length, 1 cm width, and is configured to be disposed between the soft maghetic member and the objuect.

15. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface;

an antenna coil which is formed by at least one turn and disposed on the soft magnetic member; and

conductive member disposed on said soft magnetic member on an opposite side of a placement of the antenna coil,

wherein the reader/writer antenna is configured to be disposed so as to contact a casing which is formed by a non-magnetic member which has an initial resistance of approximately 10×

10<sup>−

8</sup>Ω

m or lower.

16. A reader/writer antenna which is used with a Radio Frequency Identification (RFID) system for non-contacting data communication comprising:

a soft magnetic member configured to be disposed on a surface; and

an antenna coil which is formed by at least one turn and disposed on the soft magnetic member,

wherein the antenna coil is wound in a spiral manner, and said antenna is configured to be disposed so as to contact a casing made of a conductive member which has 0.015 Ω

or lower resistance.