Antenna for RFID

• US 7,161,542 B2
• Filed: 12/18/2001
• Issued: 01/09/2007
• Est. Priority Date: 12/18/2000
• Status: Expired due to Term

• Current Assignee: Mitsubishi Materials Corporation
• Original Assignee: Mitsubishi Materials Corporation
• Inventors: Yahata, Seirou, Yonezawa, Tadashi, Endo, Takanori
• Primary Examiner(s): Nguyen; Hoang V.
• Assistant Examiner(s): Mancuso; Huedung
• Application Number:
  US10/433,606
• Publication Number:
  US 20040075616A1
• Time in Patent Office: 1,848 Days
• Field of Search: 343/702, 343/700.MS, 343/895, 343/866, 343/867, 343/873
• US Class Current: 343/702
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• 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 19/07779 the inductive antenna being a coil
• CPC Class Codes: G06K 19/07781 the coil being fabricated in a winding process
• CPC Class Codes: G06K 19/07783 the coil being planar
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 7/06 with core of ferromagnetic material H01Q7/02 takes precedence
• CPC Class Codes: H01Q 9/27 Spiral antennas

Abstract

An antenna for RFID (Radio Frequency Identification) configured to be electrically connected to an IC (Integrated Circuit) chip or capacitor and configured to be affixed to an article. The antenna includes: a planar conductive member having a first side configured to be mounted on the article; and a coil body configured with coil turns and mounted on or at a second side which is opposite to the first side of the conductive member. The number of the coil turns and diameter of the coil body are adjusted such that a characteristic of said coil body has a predetermined value. The conductive member shields the coil body from the article.

Claims

1. An antenna for RFID (Radio Frequency Identification) configured to be electrically connected to an IC (Integrated Circuit) chip or capacitor and configured to be affixed to an article, comprising:

a planar conductive member having a first side configured to be mounted on the article; and

a coil body configured with coil turns and mounted on or at a second side of the conductive member which is opposite to the first side of the conductive member, wherein the number of the coils turns and diameter of said coil body are adjusted such that the characteristic of said coil body has a predetermined value, and the coil body is shielded by conductive member,

wherein said conductive member is a sheet, plate, or foil, having a spiral shape and two ends connected to each other.

2. The antenna for RFID according to claim 1, wherein

electrical resistance between both ends of an area having a width of 1 cm and a length of 1 cm of said conductive member in a longitudinal direction is 5Ω

or less.

3. The antenna for RFID according to claim 1, wherein

said conductive member is a conductive paint film applied to a planar nonconductive member, and

said coil body is affixed to a surface of said nonconductive member.

4. The antenna for RFID according to claim 1, wherein

said conductive member is laminated on a planar nonconductive member, and

said coil body is affixed to a surface of said nonconductive member.

5. The antenna for RFID according to claim 1, wherein

a gap between said conductive member and said coil body ranges between 0.01 and 5 mm.

6. The antenna for RFID according to claim 1, wherein

a hole is formed at a portion of said conductive member surrounded by said coil body.

7. The antenna for RFID according to claim 1, wherein

a soft magnetic member is disposed between said conductive member and said coil body.

8. The antenna for RFID according to claim 7, wherein

said soft magnetic member has a value of 0.5 or more in a product of magnetic permeability and thickness in millimeters of said soft magnetic member.

9. The antenna for RFID according to claim 7, wherein

said soft magnetic member is formed of at least one of a rapidly solidifying material, casting material, rolling material, forging material, and sintering material each including at least one of an amorphous alloy, permalloy, magnetic steel, silicon steel, sendust alloy, Fe—

Al alloy, and soft-magnetic ferrite.

10. The antenna for RFID according to claim 7, wherein

said soft magnetic member includes a composite material of (1) fine particles or flakes of a metal or ferrite, and (2) plastic or rubber, or

said soft magnetic member includes a film of a paint containing fine particles or flakes of a metal or ferrite.

11. The antenna for RFID according to claim 7, wherein

said soft magnetic member is an adhesive sheet obtained by adhering a plurality of flakes, comprised of a metal or soft magnetic ferrite, to a surface of a base-material sheet comprised of plastic so that the flakes closely contact each other.

12. The antenna for RFID according to claim 11, wherein

said soft magnetic member is further obtained by covering the flakes with a cover sheet comprised of plastic and adhering said base-material sheet and said cover sheet together.

13. An antenna for RFID (Radio Frequency Identification) configured to be electrically connected to an IC (Integrated Circuit) chip or capacitor and configured to be affixed to an article, comprising:

a planar soft magnetic member having a first side configured to be mounted on the article; and

a coil body including coil turns and mounted on or at a second side of the soft magnetic member which is opposite to the first side of said soft magnetic member,

wherein the number of the coil turns and diameter of said coil body are set such that a characteristic of said coil body has a predetermined value, and the coil body is shielded by said soft magnetic member from the article,

wherein said soft magnetic member is an adhesive sheet obtained by adhering a plurality of flakes, comprised of a metal or soft magnetic ferrite, to a surface of a base-material sheet made of plastic so that the flakes closely contact each other.

14. The antenna for RFID according to claim 13, wherein

said soft magnetic member has a value of 0.5 or more in a product of magnetic permeability and thickness in millimeters of said soft magnetic member.

15. The antenna for RFID according to claim 13, wherein

said soft magnetic member is formed of at least one of a rapidly solidifying material, casting material, rolling material, forging material, and sintering material of each including at least one of an amorphous alloy, permalloy, magnetic steel, silicon steel, sendust alloy, Fe—

Al alloy, or soft-magnetic ferrite.

16. The antenna for RFID according to claim 13, wherein

said soft magnetic member includes a composite material of (1) fine particles or flakes of a metal or ferrite, and (2) plastic or rubber, or

said soft magnetic member includes a film of a paint containing fine particles or flakes of a metal or ferrite.

17. The antenna for RFID according to claim 16, wherein said soft magnetic member is further obtained by covering the flakes with a cover sheet comprised of plastic and adhering said base-material sheet and said cover sheet together.

18. The antenna for RFID according to claim 16, wherein the hole permits the electromagnetic waves to more easily pass through said conductive member.