Composite antenna

• US 8,179,329 B2
• Filed: 07/29/2010
• Issued: 05/15/2012
• Est. Priority Date: 03/03/2008
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Kato, Noboru
• Primary Examiner(s): Nguyen, Hoang V
• Application Number:
  US12/845,846
• Publication Number:
  US 20100283694A1
• Time in Patent Office: 656 Days
• Field of Search: 343725-730, 343/700.MS, 340/572.1, 340/572.7
• US Class Current: 343/726
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies
• CPC Class Codes: G06K 19/07777 the antenna being of the inductive type
• CPC Class Codes: G06K 19/07779 the inductive antenna being a coil
• CPC Class Codes: G06K 19/07786 the antenna being of the HF type, such as a dipole
• 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 1/38 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 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 9/16 with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole H01Q9/44 takes precedence
• CPC Class Codes: H01Q 9/26 with folded element or elements, the folded parts being spaced apart a small fraction of operating wavelength resonant loop antennas H01Q7/00
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407

Abstract

A composite antenna achieves favorable radiation characteristics and favorable communication performance, and can be used in short distance communication as well as long distance communication. The composite antenna includes a dipole antenna having an elongated shape, a loop antenna including at least one pair of opposing end portions, and a connection portion arranged to connect the dipole antenna and a point of the loop antenna at which the amplitude of a current flowing in the loop antenna has a maximum value. The dipole antenna performs long distance communication utilizing an electric field, and the loop antenna performs short distance communication utilizing a magnetic field. This composite antenna may be used as a wireless IC device in RFID systems.

Claims

1. A composite antenna, comprising:

a dipole antenna having an elongated shape;

a loop antenna including at least one pair of opposing end portions; and

a connection portion arranged to connect the dipole antenna and a point of the loop antenna at which an amplitude of a current flowing in the loop antenna has a maximum value;

wherein

an electrical length of the loop antenna in a stand-alone state is greater than an electrical length of the dipole antenna in a stand-alone state.

2. The composite antenna according to claim 1, wherein the connection portion is connected to a point of the dipole antenna at which an amplitude of a current flowing in the dipole antenna has a maximum value.

3. The composite antenna according to claim 1, wherein the dipole antenna and the loop antenna are arranged such that an electric field generated around the dipole antenna and a magnetic field generated around the loop antenna are perpendicular or substantially perpendicular to each other.

4. The composite antenna according to claim 1, wherein end portions of the dipole antenna are arranged such that the loop antenna is disposed between the end portions of the dipole antenna at both sides of the loop antenna in plan view.

5. The composite antenna according to claim 1, wherein the dipole antenna and the loop antenna are electrically connected at respective approximate center portions thereof in respective longitudinal directions.

6. The composite antenna according to claim 1, wherein a resonant frequency of the loop antenna in the stand-alone state is higher than a resonant frequency of the dipole antenna in the stand-alone state.

7. The composite antenna according to claim 1, wherein the loop antenna has a substantially rectangular shape.

8. The composite antenna according to claim 7, wherein the loop antenna is electromagnetic coupled with the dipole antenna at three sides of the substantially rectangular shape.

9. The composite antenna according to claim 1, wherein both ends of the dipole antenna are provided with wide portions that are wider than a line width of the approximate center portion of the dipole antenna in the longitudinal direction.

10. The composite antenna according to claim 1, wherein the pair of end portions of the loop antenna are arranged so as to be located toward the inside of the loop antenna.

11. The composite antenna according to claim 1, wherein a plurality of the connection portions are provided.

12. The composite antenna according to claim 1, wherein the loop antenna, the dipole antenna, and the connection portion are provided on a single common substrate.

13. The composite antenna according to claim 1, wherein the loop antenna is provided on a first main surface of a substrate and the dipole antenna is provided on a second main surface of the substrate opposite to the first main surface, and the loop antenna and the dipole antenna are connected by a via hole conductor provided in the substrate.