JP2001326523A - Helical antenna structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strengthen a structure by altering the helical member of a helical antenna. SOLUTION: A cylinder 1, a center shaft 2 and eight ribs 3 are molded integrally with plastic. The eight ribs 3 are formed symmetrically and radially around the shaft 2 and connect the shaft 2 to the inner circumferential surface of the cylinder 1. The shaft 2 and the respective ribs 3 are formed over the entire length of the cylinder 1 from one end to the other. The outer circumferential surface is wrapped with an antenna pattern film 4. The film 4 is constituted so that a plurality of conductor patterns 6 are printed on an insulation sheet 5 helically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention receives digital radio broadcasts by receiving radio waves from artificial satellites (hereinafter also referred to as "satellite waves") or radio waves on the ground (hereinafter also referred to as "terrestrial waves"). And more particularly to an antenna used in a digital radio receiver.

[0002]

2. Description of the Related Art Recently, a digital radio receiver capable of receiving a satellite wave or a terrestrial wave so as to listen to a digital radio broadcast has been developed and is being put to practical use in the United States. This digital radio receiver is mounted on a mobile station such as an automobile, and is capable of receiving radio waves having a frequency of about 2.3 GHz and listening to radio broadcasts. That is, the digital radio receiver is a radio receiver that can listen to mobile broadcasts. The terrestrial wave is a signal obtained by temporarily receiving a satellite wave at an earth station and then slightly shifting the frequency.

In order to receive such a radio wave of a frequency of about 2.3 GHz, it is necessary to install an antenna outside the automobile. As such an antenna, various antennas can be considered, but a stick type is generally used instead of a flat type (flat type). Also, as is well known, an electromagnetic wave radiated in free space is a transverse wave having an electric field and a magnetic field oscillating in a plane perpendicular to the traveling direction of the wave, and the electric field and the magnetic field change in intensity in the plane. However, this is called polarization. Satellite waves are circularly polarized waves, whereas terrestrial waves are linearly polarized waves. Therefore, in order to receive both the satellite wave and the terrestrial wave, a dedicated antenna is required for each.

Hereinafter, an antenna for receiving a satellite wave will be mainly described. A helical antenna is known as one of the stick antennas. The helical antenna has a structure in which a plurality of conductive wires are wound around a cylindrical member in a helical shape (spiral shape), and can efficiently receive the above-described circularly polarized waves. As a material of the cylindrical member, an insulating material such as plastic is used. Also,
As the number of conductive wires, for example, four wires are used. On the other hand, it is actually extremely difficult to wind a plurality of conducting wires around a cylindrical member in a helical manner. Therefore, instead, there has been proposed a helical antenna in which an antenna pattern film formed by printing a plurality of conductor patterns on an insulating sheet is wound around a cylindrical member.

[0005]

The helical antenna of this type has a low strength because the inside of the cylindrical member is hollow.

Accordingly, the present invention is to improve the structure of the helical antenna by modifying the cylindrical member.

[0007]

The present invention employs the following means to solve the above-mentioned problems.

[0008] 1. In a helical antenna composed of a tubular member made of an insulator and an antenna pattern film wound around the tubular member, a central axis of the tubular member is provided. A helical antenna structure in which at least three ribs (3) are formed symmetrically and radially between (2) and the inner peripheral surface.

[0009] 2. 2. The helical antenna structure according to claim 1, wherein the tubular member (1), the center shaft (2), and the rib (3) are integrally formed of plastic.

[0010] 3. The helical antenna structure according to claim 1, wherein the central axis (2) and the rib (3) are formed over the entire length from one end to the other end of the tubular member (1).

4. The central shaft (2) and the rib (3) are formed on the cylindrical member (1) and partially formed on the cylindrical member (1).
The helical antenna structure as described.

Note that the reference numerals in the parentheses are given for easy understanding of the present invention, and therefore are merely examples, and the present invention is not limited to the members provided with these reference numerals. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A helical antenna structure according to an embodiment of the present invention will be described with reference to FIG.

The cylinder 1, the central shaft 2 and the eight ribs 3 are integrally formed of plastic. The eight ribs 3 are
Are formed symmetrically and radially around the inner periphery of the cylinder 1 and connect the central axis 2 and the inner peripheral surface of the cylinder 1. The central shaft 2 and each rib 3 are formed over the entire length from one end to the other end of the cylinder 1.

An antenna pattern film 4 is wound around the outer peripheral surface of the cylinder 1. The antenna pattern film 4 is configured by printing a plurality of conductor patterns 6 on an insulating sheet 5 in a helical manner.

In consideration of strength retention, weight restrictions, material cost savings, and ease of molding, the cylinder 1 has a thickness (dimension between the inner and outer peripheral surfaces) of 0.5 to 0.5 mm. 4 mm and an inner diameter of about 12 mm are appropriate.

Although the number of the ribs 3 is eight in the present embodiment, three or more ribs are appropriately selected according to the required strength of the cylinder 1. Further, when the ribs 3 are formed radially symmetrically around the central axis 2, the strength of the cylinder 1 is improved, and the molding can be easily performed. Furthermore, the center shaft 2 and each rib 3
Are formed over the entire length from one end to the other end of the cylinder 1 in the present embodiment, but the design is changed so as to be partially formed at at least one of the vicinity of one end or the other end of the cylinder 1. can do. Further, the design of the cylinder can be changed to a rectangular cylinder.

[0018]

As is apparent from the above description, according to the present invention, at least three ribs are formed symmetrically and radially between the central axis of the cylindrical member and the inner peripheral surface. The strength of the member can be improved. Therefore, the helical antenna is less likely to be deformed or damaged, and has increased durability.

[Brief description of the drawings]

FIGS. 1A and 1B show a main part of a helical antenna structure according to an embodiment of the present invention, wherein FIG. 1A is a perspective view, and FIG. 1B is an end view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Center axis 3 Rib 4 Antenna pattern film 5 Insulating sheet 6 Conductor pattern

Claims (4)

[Claims] 1. A helical antenna comprising a cylindrical member made of an insulator and an antenna pattern film wound around the cylindrical member, wherein a helical antenna is provided between a central axis of the cylindrical member and an inner peripheral surface. At least 3
A helical antenna structure in which the ribs of the book are formed symmetrically and radially. 2. The helical antenna structure according to claim 1, wherein said tubular member, said central axis, and said rib are integrally formed of plastic. 3. The helical antenna structure according to claim 1, wherein the center axis and the rib are formed over the entire length from one end to the other end of the tubular member. 4. The helical antenna structure according to claim 1, wherein said central axis and said rib are partially formed in said tubular member.