Antenna, method for manufacturing the antenna, and communication apparatus including the antenna

• US 20050099337A1
• Filed: 07/30/2004
• Published: 05/12/2005
• Est. Priority Date: 11/12/2003
• Status: Active Grant

• Current Assignee: Hitachi, Ltd., Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi, Ltd., Hitachi Metals (Thailand) Ltd.
• Inventors: Aoyama, Hiroyuki, Takei, Ken
• Granted Patent: US 7,015,862 B2
• Time in Patent Office: Days
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 1/243 with built-in antennas
• 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 9/30 with feed to end of elongated active element, e.g. unipole H01Q9/44 takes precedence

Abstract

The invention provides a small multimode antenna capable of commonly using a single feeding point at a plurality of frequencies. The antenna includes a radiating conductor 1 disposed above a ground conductor 6 and distributed-constant circuits 2 and 3 coupled to the radiating conductor. Each of the distributed-constant circuits is constructed by a transmission line and has a branch. One end of the radiating conductor and one end of the distributed-constant circuit 2 are connected to each other to be a connection point and, further, the other end of the radiating conductor and one end of the distributed-constant circuit 3 are connected to each other. The connection point is a single feeding point 9 using the ground conductor as an earth. The distributed-constant circuits 2 and 3 are designed as an equivalent circuit in which different stubs are connected in parallel with a transmission line, and impedance matching at a plurality of frequencies is realized at the feeding point.

Claims

1. An antenna comprising:

a radiating conductor disposed above a ground conductor; and

first and second distributed-constant circuits coupled to said radiating conductor,

wherein each of said first and second distributed-constant circuits is constructed by a transmission line and has a branch,

wherein one end of said radiating conductor and one end of said first distributed-constant circuit are connected to each other and, further, the other end of said radiating conductor and one end of said second distributed-constant circuit are connected to each other, and

wherein a connection point of one end of said radiating conductor and one end of said first distributed-constant circuit is a single feeding point using said ground conductor as an earth.

2. The antenna according to claim 1, wherein different stubs are connected to said first and second distributed-constant circuits respectively.

3. The antenna according to claim 1, wherein said first and second distributed-constant circuits are disposed below said radiating conductor between said radiating conductor and said ground conductor.

4. The antenna according to claim 3, wherein each of said first and second distributed-constant circuits is made of striplines.

5. The antenna according to claim 1, wherein each of said first and second distributed-constant circuits is made of coaxial lines.

6. The antenna according to claim 4, wherein a conductor having an earth is disposed between said radiating conductor and said first and second distributed-constant circuits.

7. The antenna according to claim 4, wherein a first dielectric substrate is disposed between said radiating conductor and said first and second distributed-constant circuits and a second dielectric substrate is disposed between said first and second distributed-constant circuits and said ground conductor.

8. The antenna according to claim 7, wherein said radiating conductor is constructed by a radiating conductor pattern formed on the top face of said first dielectric substrate, said first and second distributed-constant circuits are constructed by stripline patterns formed on the top face of said second dielectric substrate, said ground conductor is constructed by a ground conductor pattern formed on the rear face of said second dielectric substrate, and a multilayer substrate structure is formed by said first and second dielectric substrates.

9. A method for manufacturing an antenna,

wherein said antenna comprises:

a radiating conductor disposed above a ground conductor; and

first and second distributed-constant circuits coupled to said radiating conductor,

wherein each of said first and second distributed-constant circuits is constructed by a transmission line and has a branch,

wherein one end of said radiating conductor and one end of said first distributed-constant circuit are connected to each other and, further, the other end of said radiating conductor and one end of said second distributed-constant circuit are connected to each other,

wherein a connection point of one end of said radiating conductor and one end of said first distributed-constant circuit is a single feeding point using said ground conductor as an earth,

the method comprising the steps of;

forming a radiating conductor pattern as said radiating conductor on the top face of a first dielectric substrate;

forming a stripline pattern as said first and second distributed-constant circuits on the top face of a second dielectric substrate, and forming a ground conductor pattern as said ground conductor on the rear face of said second dielectric substrate;

joining said first and second dielectric substrates on which said conductor patterns are formed; and

forming a first side conductor for connecting one end of said radiating conductor and one end of said first distributed-constant circuit and forming a second side conductor for connecting the other end of said radiating conductor and one end of the second distributed-constant circuit, on each of facing side surfaces of said joined first and second dielectric substrates.

10. A communication apparatus comprising:

an RF circuit for generating a transmission signal to be transmitted by radio and processing a signal received by radio;

an antenna connected to an input-output point of said RF circuit;

a circuit board on which said RF circuit and said antenna are mounted; and

a body for housing said circuit board,

wherein said antenna comprises;

a radiating conductor disposed above a ground conductor; and

first and second distributed-constant circuits coupled to said radiating conductor,

wherein each of said first and second distributed-constant circuits is constructed by a transmission line and has a branch,

wherein one end of said radiating conductor and one end of said first distributed-constant circuit are connected to each other and, further, the other end of said radiating conductor and one end of said second distributed-constant circuit are connected to each other, and

wherein a connection point of one end of said radiating conductor and one end of said first distributed-constant circuit is a single feeding point using said ground conductor as an earth.