Antenna device and radio frequency IC device

• US 8,070,070 B2
• Filed: 12/02/2008
• Issued: 12/06/2011
• Est. Priority Date: 12/26/2007
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Taniguchi, Katsumi, Sasaki, Jun, Kato, Noboru
• Primary Examiner(s): FRANKLIN, JAMARA ALZAIDA
• Application Number:
  US12/326,117
• Publication Number:
  US 20090166434A1
• Time in Patent Office: 1,099 Days
• Field of Search: 235/492, 3405721-5729
• US Class Current: 235/492
• 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 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• 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 7/00 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

Abstract

An antenna device is arranged to transmit or receive a radio frequency communication signal to or from an external device such as a reader/writer, and is arranged such that an antenna resonance circuit including an antenna coil and a capacitor is connected to an additional resonance circuit including an inductor and a capacitor. A radio frequency IC device preferably includes the antenna device and a radio frequency IC. The antenna device is constructed such that a change in characteristics thereof caused by a change in the distance between a radio frequency IC device and a reader/writer is minimized, and the radio frequency IC device performs communication with high reliability.

Claims

1. An antenna device included in a radio frequency IC device that is arranged to perform radio frequency communication with an external device, the antenna device comprising:

an antenna element including an antenna coil arranged to transmit or receive a radio frequency communication signal to or from the external device; and

an additional resonance circuit that is connected to the antenna element, that includes at least one inductor, and has a resonance frequency characteristic different from a resonance frequency of the antenna element;

wherein

a physical dimensional size of the at least one inductor of the additional resonance circuit is smaller than a physical dimensional size of the antenna coil.

2. The antenna device according to claim 1,

wherein the antenna coil and the at least one inductor included in the additional resonance circuit are arranged to be magnetically coupled.

3. The antenna device according to claim 1, wherein the additional resonance circuit is a parallel resonance circuit.

4. The antenna device according to claim 1,

wherein the antenna element is connected in series to the additional resonance circuit.

5. The antenna device according to claim 1, wherein

the additional resonance circuit includes a resonance circuit having a resonance frequency lower than a communication frequency used by the radio frequency IC device;

and

the resonance frequency of the antenna element is higher than the communication frequency used by the radio frequency IC device.

6. The antenna device according to claim 1, wherein

the additional resonance circuit includes a first additional resonance circuit having a resonance frequency lower than a communication frequency used by the radio frequency IC device, and a second additional resonance circuit having a resonance frequency higher than the communication frequency used by the radio frequency IC device;

and

the resonance frequency of the antenna element is higher than the communication frequency used by the radio frequency IC device.

7. The antenna device according to claim 6, wherein inductors included in the first additional resonance circuit and the second additional resonance circuit individually include two adjacent lines of different lengths.

8. The antenna device according to claim 1,

wherein the at least one inductor included in the additional resonance circuit is magnetically shielded.

9. The antenna device according to claim 8, wherein the additional resonance circuit is provided in a multilayer substrate including a magnetic substance.

10. The antenna device according to claim 9, further comprising an output inductor that is connected in series to an input portion that is arranged to receive a signal transmitted from the radio frequency IC and is provided in the multilayer substrate.

11. The antenna device according to claim 9, wherein the additional resonance circuit includes a chip capacitor disposed either on a surface of the multilayer substrate, or in the multilayer substrate.

12. A radio frequency IC device comprising:

the antenna device according to claim 9;

wherein

the radio frequency IC is disposed either on a surface of the multilayer substrate of the antenna device, or in the multilayer substrate of the antenna device.