ANTENNA DEVICE AND METHOD OF SETTING RESONANT FREQUENCY OF ANTENNA DEVICE

• US 20120262357A1
• Filed: 10/13/2011
• Published: 10/18/2012
• Est. Priority Date: 04/21/2009
• Status: Abandoned Application

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: KATO, Noboru, TANIGUCHI, Katsumi, SASAKI, Jun, GOCHI, Naoki
• Application Number:
  US13/272,365
• Publication Number:
  US 20120262357A1
• Time in Patent Office: Days
• US Class Current: 343/788
• CPC Class Codes: G06K 19/07779 the inductive antenna being a coil
• CPC Class Codes: H01P 11/00 Apparatus or processes specially adapted for manufacturing waveguides or resonators, lines, or other devices of the waveguide type
• CPC Class Codes: H01P 11/001 Manufacturing waveguides or transmission lines of the waveguide type
• CPC Class Codes: H01Q 1/22 by structural association with other equipment or articles
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• 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 1/2291 used in bluetooth or WI-FI devices of Wireless Local Area Networks [WLAN] H01Q1/241 takes precedence; WLAN in general H04W
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• 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 1/48 Earthing means; Earth screens; Counterpoises
• 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 19/02 Details fastening of an element on a boom H01Q1/1228
• CPC Class Codes: H01Q 19/062 for focusing
• 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 7/04 Screened antennas H01Q7/02, H01Q7/06 take precedence
• CPC Class Codes: H01Q 7/06 with core of ferromagnetic material H01Q7/02 takes precedence
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: Y10T 29/49016 Antenna or wave energy "plumbing" making

Abstract

In antenna device, a coil conductor of an antenna coil module and a conductor layer at least partially overlap. A current flows in the conductor layer and blocks a magnetic field generated by a current flowing in the coil conductor. A current, which flows around the periphery of an opening of the conductor layer, flows along the periphery of a slit and around the periphery of the conductor layer due to a cut-edge effect. Since magnetic flux does not pass through the conductor layer, magnetic flux attempts to bypass the conductor layer along a path in which the conductor opening of the conductor layer is on the inside and the outer edge of the conductor layer is on the outside. Accordingly, the magnetic flux generates relatively large loops linking the inside and the outside of a coil conductor of an antenna on a reader/writer side.

Claims

1. An antenna device comprising:

a coil conductor having a loop shape or a spiral shape in which a winding center portion defines a coil opening; and

a conductor layer that is arranged on a side closer to an antenna on a communication partner side than a location of the coil conductor;

wherein

the conductor layer includes a conductor opening and a slit, the slit connecting the conductor opening and an outer edge of the conductor layer; and

when the coil conductor is viewed in plan view, the coil conductor and conductor layer are superposed one on top of the other.

2. The antenna device according claim 1, wherein when the coil conductor is viewed in plan view, the coil opening and the conductor opening at least partially overlap.

3. The antenna device according to claim 1, wherein the coil conductor and the conductor layer are arranged so as to be in a vicinity of each other.

4. The antenna device according to claim 1, wherein an area of the conductor layer is larger than an area of a region in which the coil conductor is located.

5. The antenna device according to claim 1, wherein the coil conductor is wound across a plurality of layers.

6. The antenna device according to claim 1, wherein, when the coil conductor is viewed in plan view, the coil opening and the conductor opening overlap each other over almost entire peripheries thereof.

7. The antenna device according to claim 1, wherein the conductor layer is located on an inner surface or an outer surface of a casing of an electronic appliance.

8. The antenna device according to claim 1, wherein the coil conductor is located on a substrate, a magnetic sheet is stacked on a surface of the substrate on a side that is distant from the antenna of the communication partner side, and an antenna coil module is defined by the substrate and the magnetic sheet.

9. The antenna device according to claim 8, wherein the resonant frequency is lower than a central frequency of a to-be-used frequency band in a state in which the conductor layer is not present and is equal or substantially equal to the central frequency of the to-be-used frequency band in a state in which the antenna coil module has been mounted inside the casing of the electronic appliance.

10. A method of setting a resonant frequency of an antenna device, the antenna device being configured by mounting, inside a casing of an electronic appliance, an antenna coil module that is formed by stacking a substrate on which a loop-shaped or spiral-shaped coil conductor, in which a winding center portion defines a coil opening, has been formed, on a magnetic sheet, the method comprising the steps of:

arranging a conductor layer in the casing on a side that is closer to an antenna of a communication partner side than a location of the coil conductor; and

providing a conductor opening and a slit in the conductor layer, the slit connecting the conductor opening and an outer edge of the conductor layer;

wherein

when the substrate is viewed in plan view, the coil conductor and the conductor layer are superposed one on top of the other; and

the resonant frequency is set to be lower than a central frequency of a to-be-used frequency band when the conductor layer is not present and is set to be equal or substantially equal to the central frequency of the to-be-used frequency band when the antenna coil module has been mounted inside the casing of the electronic appliance.