Antenna device and method of setting resonant frequency of antenna device

• US 9,564,678 B2
• Filed: 09/06/2012
• Issued: 02/07/2017
• Est. Priority Date: 04/21/2009
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Kato, Noboru, Taniguchi, Katsumi, Sasaki, Jun, Gochi, Naoki
• Primary Examiner(s): Purvis, Sue A
• Assistant Examiner(s): PATEL, AMAL A
• Application Number:
  US13/604,801
• Publication Number:
  US 20130234905A1
• Time in Patent Office: 1,615 Days
• Field of Search: 343/788, 343/895, 343867-868, 343/870, 343/741, 343/842
• US Class Current: 1/1
• 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 to block a magnetic field generated by a current flowing in the coil conductor. A current 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. As a result, the magnetic flux generates large loops that link the inside and the outside of a coil conductor of an antenna on a reader/writer side to couple an antenna device and the antenna on the reader/writer side.

Claims

1. An electronic appliance comprising:

a casing;

an antenna device disposed in the casing, the antenna device including;

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;

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;

when the coil conductor is viewed in plan view, at least a portion of the coil conductor overlaps with the conductor layer;

the conductor layer is arranged to function as a radiator to radiate a magnetic field; and

the electronic appliance is configured such that the magnetic field is radiated towards an outside of the casing and communication between the antenna device and a communication partner is performed with the communication partner being disposed outside of the casing;

the communication between the antenna device and the communication partner is performed using inductive coupling;

the conductor layer is located on an inner surface, on an outer surface, or on an internal component of the casing of the electronic appliance; and

an end portion of the coil opening at least partially overlaps with the conductor layer when viewed in plan view.

2. The electronic appliance according to claim 1, wherein the slit in the conductor layer is provided in a portion of the conductor layer at which a distance from the conductor opening to the edge surface of the casing is less than half of a length or width of the casing.

3. The electronic appliance according to claim 1, wherein the slit in the conductor layer is provided in a portion of the conductor layer which is adjacent to the edge surface of the casing.

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

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

6. The electronic appliance 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 electronic appliance 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 spaced from the antenna on the communication partner side, and an antenna coil module includes the substrate and the magnetic sheet.

8. The electronic appliance according to claim 1, wherein a resonant frequency of the antenna device 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.

9. The electronic appliance according to claim 1, wherein the communication partner is a reader/writer.

10. The electronic appliance according to claim 1, further comprising a magnetic layer.

11. The electronic appliance according to claim 1, wherein the communication between the antenna device and the communication partner is performed in the HF frequency band.

12. The electronic appliance according to claim 2, wherein an area of the conductor layer is larger than an area of a region in which the coil conductor is disposed.

13. The electronic appliance according to claim 1, further comprising a magnetic layer arranged on a side farther from an antenna on a communication partner side than the coil conductor is relative to the antenna on the communication partner side.

14. The electronic appliance according to claim 13, wherein when the conductor layer is viewed in plan view, an outer peripheral edge of the magnetic layer is located inside of an outer peripheral edge of the conductor layer.

15. An electronic appliance comprising:

a metal casing;

an antenna device disposed in the casing, the antenna device including;

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;

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;

when the coil conductor is viewed in plan view, at least a portion of the coil conductor overlaps with the conductor layer;

the conductor layer is arranged to function as a radiator to radiate a magnetic field; and

the electronic appliance is configured such that the magnetic field is radiated towards an outside of the casing and communication between the antenna device and a communication partner is performed with the communication partner being disposed outside of the casing;

the communication between the antenna device and the communication partner is performed using inductive coupling;

the conductor layer is defined by at least a portion of the metal casing of the electronic appliance; and

an end portion of the coil opening at least partially overlaps with the conductor layer when viewed in plan view.