Antenna device and method of setting resonant frequency of antenna device

Patent metadata

Field	Value
Publication number	US-9825353-B2
Application number	US-201514921185-A
Country	US
Kind code	B2
Filing date	Oct 23, 2015
Priority date	Apr 21, 2009
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

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.

First claim

What is claimed is:

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 including a slit and a conductor opening; wherein
the slit connects the conductor opening to an outer edge of the conductor layer;
when the coil conductor is viewed in plan view, a portion of the coil conductor overlaps the conductor layer and a portion of the conductor opening overlaps the coil opening;
the conductor opening includes a portion that does not overlap with either the coil conductor or the coil opening; and
a width of all portions of the slit in the conductor layer is smaller than a width of the conductor opening.

2. The antenna device according to claim 1 , wherein the coil conductor is offset from a center of the conductor opening when the coil conductor is viewed in plan view.

3. The antenna device according to claim 1 , further comprising a magnetic layer arranged farther from an outside of a casing in which the antenna device is disposed than the coil conductor.

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

5. The antenna device according to claim 1 , wherein the conductor layer is located on an inner surface or an outer surface of a casing in which the antenna device is disposed.

6. The antenna device 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 coil conductor has been mounted inside a casing.

7. An electronic appliance comprising:
the antenna device according to claim 1 ; and
a metal casing in which the antenna device is disposed; wherein
the antenna device is provided on a surface of the metal casing; and
the metal casing defines the conductor layer.

Assignees

• Murata Manufacturing Co

Inventors

• Kato Noboru
• Taniguchi Katsumi
• Sasaki Jun
• Gochi Naoki

Classifications

• H01Q19/062

  for focusing · CPC title

• H01Q7/06

  with core of ferromagnetic material (H01Q7/02 takes precedence) · CPC title

• H01Q1/38 Primary

  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 title

• H01Q1/48

  Earthing means; Earth screens; Counterpoises · CPC title

• H01Q1/243 Primary

  with built-in antennas · CPC title