Antenna and wireless IC device

• US 9,444,143 B2
• Filed: 03/14/2012
• Issued: 09/13/2016
• Est. Priority Date: 10/16/2009
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Nomura, Masato, Kato, Noboru, Dokai, Yuya
• Primary Examiner(s): Levi, Dameon E
• Assistant Examiner(s): LINDGREN BALTZELL, ANDREA J
• Application Number:
  US13/419,454
• Publication Number:
  US 20120169553A1
• Time in Patent Office: 1,644 Days
• Field of Search: 343/741
• US Class Current: 1/1
• 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 5/371 Branching current paths
• 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 includes two feeding points, and includes a loop-shaped loop electrode and an auxiliary electrode electrically connected to the loop electrode and located at a position along the outer circumference of the loop electrode. The first end portion of the auxiliary electrode is electrically connected to the vicinity of one feeding point of the loop electrode. The second end portion of the auxiliary electrode is open. A resonant circuit is defined by the auxiliary electrode and the loop electrode to enhance the impedance of the antenna, compared with a case in which the antenna is configured using the simple loop electrode, and it is easy to achieve impedance matching with the wireless IC.

Claims

1. An antenna comprising:

a loop electrode including two feeding points and arranged in a loop shape; and

an auxiliary electrode that is electrically connected to the loop electrode and located at a position along the loop electrode;

wherein

the auxiliary electrode extends in a same direction as the loop electrode in relation to at least one of the two feeding points;

the auxiliary electrode includes a first end connected to the loop electrode and a second end that is open;

the first end of the auxiliary electrode is directly physically and electrically connected to the loop electrode at an area of a first one of the two feeding points, and the auxiliary electrode is arranged to extend along the loop electrode towards a second one of the two feeding points;

a width of the auxiliary electrode is thinner than a width of the loop electrode;

a capacitance is produced between the loop electrode and the auxiliary electrode; and

a parallel resonance is produced by an inductance of the auxiliary electrode, an inductance of the loop electrode, and the capacitance produced between the loop electrode and the auxiliary electrode.

2. The antenna according to claim 1, wherein the auxiliary electrode is located at a position along an outer circumference of the loop electrode.

3. The antenna according to claim 1, wherein the auxiliary electrode is the only auxiliary electrode provided in the antenna and is connected to an area of at least one of the two feeding points.

4. The antenna according to claim 1, wherein the auxiliary electrode includes two auxiliary electrodes having different lengths from each other.

5. The antenna according to claim 1, wherein the auxiliary electrode includes a meander pattern configuration in at least a portion thereof.

6. The antenna according to claim 1, wherein a resonance frequency of a circuit including the loop electrode and the auxiliary electrode is deviated from a communication frequency.

7. The antenna according to claim 1, wherein a resonance frequency of a circuit including the loop electrode and the auxiliary electrode is a frequency of a UHF band.

8. The antenna according to claim 6, wherein the communication frequency is a UHF band, and the resonance frequency of the circuit including the loop electrode and the auxiliary electrode is deviated to a frequency of about 30 MHz or more lower than the communication frequency.

9. A wireless IC device including the antenna according to claim 1, the wireless IC device comprising:

a wireless IC configured to perform power feeding on at least one of the two feeding points of the antenna.

10. The wireless IC device according to claim 9, wherein the wireless IC includes a feed circuit arranged to perform power feeding on the at least one of the two feeding points of the antenna and an IC chip arranged to perform power feeding on the at least one of the two feeding points of the antenna through the feed circuit.

11. The wireless IC device according to claim 10, wherein the feed circuit includes a resonant circuit whose resonance frequency substantially corresponds to a communication frequency.

12. The wireless IC device according to claim 10, wherein the feed circuit is provided in a feed circuit substrate and the IC chip is mounted in the feed circuit substrate.