JPH09238018A - Helical antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact helical antenna with an excellent antenna characteristics immune to the effect of a human body suitable for a small sized portable radio equipment. SOLUTION: This helical antenna is composed of n-sets of helical antenna elements 1a, 2a, 3a,... whose cores are made of cylindrical resin pipes 1, 2, 3,... with different diameter and the elements are connected electrically, and a helical winding diameter of the (n-1)th helical antenna element is formed nearly the same as the inner diameter of the core of the n-th helical antenna element.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a helical antenna. More specifically, the present invention relates to a helical antenna for reducing the size and increasing the band of an antenna of a portable wireless device (handy wireless device).

[0002]

2. Description of the Related Art In recent years, portable radios have been widely used. About 1 / one of the frequency used in a portable radio
A 4-wavelength electric length rod antenna is widely used. In this case, the wavelength is about 2 m especially in the VHF band used, and the total length is 50 cm in the 1/4 wavelength antenna. The size of the portable wireless device is as small as about 20 cm or less, and even if the metal case of the wireless device is used as the ground of the antenna, it does not fully function as a ground, and the 1/4 wavelength antenna can be used as a portable wireless device. Even if it was set, it was not possible to obtain sufficient antenna performance. In addition, this antenna is particularly susceptible to the human body (particularly the hand), and a person having a portable wireless device has a large effect on the antenna gain and directivity.
This is because a high-frequency current flows through the human body, causing a shift in the resonance frequency of the antenna and a change in the directional characteristics. In addition, a voltage-fed rod antenna having an electric length of λ / 2 is known as an antenna that is less likely to be affected by the human body. FIG. 8 is a perspective view of a conventional λ / 2 antenna for a portable wireless device. Reference numeral 9 denotes a portable wireless device body, and 10 denotes a λ / 2 wavelength antenna attached to the portable wireless device body 9.

[0003]

However, in the antenna of the above-mentioned conventional portable radio device, in the VHF band,
Since the total length is about 1 m, which is more than 5 times the size of the portable wireless device, there is a problem that the portable type is too long and difficult to handle. Further, both the quarter-wave antenna and the half-wave antenna have a problem that the frequency bandwidth is narrow as shown in the frequency characteristic diagram of the conventional λ / 2 antenna for portable radio equipment of FIG.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a helical antenna suitable for a compact and small portable wireless device which is excellent in antenna characteristics and is not easily affected by the human body.

[0005]

In order to solve this problem, the present invention has a structure in which the antenna element is helical and a plurality of antenna elements having different helical winding diameters are used for widening the frequency band. ing. As a result, the antenna can be electrically resonated at λ / 2, the antenna can be further downsized, and the helical antenna having excellent antenna characteristics can be obtained which is less likely to be affected by the human body.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A helical antenna according to claim 1 of the present invention has a structure in which a plurality of helical antenna elements having different helical winding diameters are electrically connected.

Here, as the helical antenna, a metal tape, carbon fiber, metal wire, conductive paint, is provided on the outer peripheral portion of a plurality of cylindrical resin pipes having winding diameters sufficiently smaller than the wavelength and having different outer diameters. It is configured by helically winding a conductive foil such as. In the helical antenna, these plural helical antenna elements may be arranged in the same straight line,
Alternatively, the helical antenna element may be arranged coaxially. With this configuration, it is possible to reduce the size of the λ / 2 wavelength antenna that is less likely to be affected by the human body and to achieve a wider frequency band characteristic.

According to a second aspect of the present invention, in the helical antenna according to the first aspect, the helical antenna elements having different helical winding diameters, each having a core formed of n synthetic resin hollow pipes having different diameters, are electrically connected. In the helical antenna, the helical winding diameter of the n-1th helical antenna element is formed to be substantially the same as the inner diameter of the core of the nth helical antenna element.
Here, the helical antenna is formed by connecting so as to feed power to each helical antenna element in series with the antenna extended. With this configuration, each helical antenna element has a plurality of helical winding diameters, so that each helical antenna element resonates at different frequencies, and the overall frequency band characteristic can be broadened.

According to a third aspect of the present invention, in the helical antenna according to the first aspect, the helical antenna elements having different helical winding diameters, each having a core formed of n synthetic resin hollow pipes having different diameters, are electrically connected. A helical antenna connected to a line with n-1 helical antenna elements
It has a configuration in which it is smaller than the core inner diameter of the individual helical antenna element and is coaxially fitted and connected. Here, the helical antenna, by making the outer diameter of the second cylinder slightly smaller than the inner diameter of the first cylinder,
It is formed by accommodating the second cylinder in the center hole of the first cylinder and similarly accommodating the (n-1) th cylinder in the nth cylinder. With this configuration, by feeding power to the individual antennas in parallel with all the antennas housed, the individual antennas operate at each frequency even when the antennas are housed.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a perspective view of a helical antenna according to Embodiment 1 of the present invention, and FIG. 2 is a side view showing its divided state. In FIGS. 1 and 2, reference numerals 1, 2, and 3 are cylindrical resin pipes having first, second, and third outer diameters having winding diameters sufficiently small with respect to the wavelength. Here, as the resin, ABS resin, cross-linked polyethylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin and the like are preferably used. In particular, a crosslinked polyethylene resin is preferable from the viewpoints of low dielectric loss, electrical characteristics and moldability. By making the outer diameter of the second cylinder slightly smaller than the inner diameter of the first cylinder, the second cylinder is housed in the hole at the center of the first cylinder, and similarly, the n-1st cylinder and the Held by winding a conductive foil such as metal tape, carbon fiber, metal wire, conductive paint, etc. around the outer circumference of a plurality of cylindrical resin pipes with different outer diameters so that it can be stored in the nth cylinder. And helical antenna elements 1a, 2a, 3a
Is configured. Each helical antenna element 1a, 2
a and 3a are helical antenna lengths Lλ / 8 to λ / 10 so that the antenna is tuned to desired frequencies f1, f2, and f3.
(Λ: wavelength), and n helical antenna elements, each having a predetermined number of turns of a conductive foil so that the electrical length becomes λ / 2 electrically, are arranged in the same straight line. In this case, coupling plates 1d, 2d, 3d and 1e, 2e, 3e are provided on the tip portions 1b, 2b, 3b and the termination portions 1c, 2c, 3c of the individual helical antenna elements, and the 1d portion, the 2e portion and the 2d portion are provided.
The portion and the 3e portion are electrically capacitively coupled to each other through the thickness of the resin pipe with the antenna extended. With this configuration, the helical antenna elements 1a, 2a, 3a are electrically connected in series.

The frequency characteristics of the present embodiment configured as described above will be described below.

FIG. 3 is a frequency characteristic diagram of each helical antenna element in the helical antenna according to the first embodiment of the present invention, showing respective resonance frequencies f1, f2 and f3 of each helical antenna element. FIG. 4 shows frequency characteristics of the helical antenna according to the first embodiment. In the figure, fD is a desired center frequency, | -Δf1 | = | f2-f1 |, |
+ Δf3-f2 |.

As is apparent from FIGS. 3 and 4, according to the present embodiment, the total resonance frequency can be broadened by the action of combining the individual resonance frequencies f1, f2 and f3. Furthermore, it can be seen that the antenna can be made compact while maintaining the antenna characteristics.

(Second Embodiment) FIG. 5 shows a perspective view of a helical antenna according to a second embodiment of the present invention, and FIG. 6 is a sectional view of the central portion thereof. In FIGS. 5 and 6, 1, 2, 3
Is a cylindrical resin pipe having a first, second, and third outer diameters having a sufficiently small winding diameter with respect to the wavelength. By accommodating the outer diameter of the second cylinder slightly smaller than the inner diameter of the first cylinder, the second cylinder is stored in the center hole of the first cylinder,
Similarly, the configuration is such that the (n-1) th cylinder can be housed in the nth cylinder, and a metal tape, carbon fiber, metal wire, conductive paint, Helical antenna elements 1a, 2a, 3a are formed by helically winding a conductive foil such as. The helical antenna elements 1a, 2a, 3a have a desired frequency f1,
The helical antenna length L λ / 8 to λ / 10 (λ: wavelength) is set so that the antenna is tuned to f2 and f3, and the conductive foil has a predetermined number of turns so that the electrical length becomes λ / 2 electrically. The n helical antenna elements are arranged coaxially.

The tip portion 1 of each helical antenna element
b, 2b, 3b and terminating portions 1c, 2c, 3c are provided with coupling plates 1d, 2d, 3d and 1e, 2e, 3e, and from the power combiner 4 provided in the antenna base 8 with the antenna accommodated. In the contact plates 4b, 5b, 6b at the tips of the plurality of branch terminals 4a, 5a, 6a, the helical antenna element 1c and the contact plates 4b, 2c and 5b, 3c and 6b electrically and mechanically contact each other. Helical antennas are fed in parallel so that signals output from the individual antennas are combined and output from the output terminal 7 of the power combiner.

The frequency characteristic of the helical antenna of the present embodiment configured as described above will be described.

FIG. 7 is a frequency characteristic diagram of the helical antenna according to the second embodiment of the present invention. As is clear from FIG. 7, according to the present embodiment, it is possible to combine the individual resonance frequencies and to broaden the total resonance frequency to a wide band.

[0018]

As described above, according to the present invention, it is possible to realize a helical antenna which is not easily affected by the human body, is small in size, and has excellent frequency characteristics, which is particularly suitable for an antenna of a portable wireless device.

[Brief description of drawings]

FIG. 1 is a perspective view of a helical antenna according to a first embodiment of the present invention.

FIG. 2 is a side view showing a split state of the helical antenna according to the first embodiment of the present invention.

FIG. 3 is a frequency characteristic diagram of each helical antenna element in the helical antenna according to the first embodiment of the present invention.

FIG. 4 is a frequency characteristic diagram of the helical antenna according to the first embodiment of the present invention.

FIG. 5 is a perspective view of a helical antenna according to a second embodiment of the present invention.

FIG. 6 is a central cross-sectional view of a helical antenna according to a second embodiment of the present invention.

FIG. 7 is a frequency characteristic diagram of the helical antenna according to the second embodiment of the present invention.

FIG. 8 is a perspective view of a conventional λ / 2 antenna for a portable wireless device.

FIG. 9 is a frequency characteristic diagram of a λ / 2 antenna for a conventional portable wireless device.

[Explanation of symbols]

 1,2,3 Cylindrical resin pipes 1a, 2a, 3a Helical antenna element 1b, 2b, 3b Tip of helical antenna element 1c, 2c, 3c Termination of helical antenna element 1d, 2d, 3d, 1e, 2e, 3e coupling plate 4 power combiner 4a, 5a, 6a branching terminal 4b, 5b, 6b contact plate 7 output terminal 8 antenna base 9 portable radio 10 λ / 2 rod antenna

Claims (3)

[Claims] 1. A helical antenna characterized in that a plurality of helical antenna elements having different helical winding diameters are electrically connected to each other. 2. A helical antenna in which cores are formed of n synthetic resin hollow pipes having different diameters, and helical antenna elements having different helical winding diameters are electrically connected to each other, and the n-1th helical antenna is provided. The helical antenna according to claim 1, wherein the helical winding diameter of the antenna element is formed to be substantially the same as the inner diameter of the core of the nth helical antenna element. 3. A helical antenna in which n helical antennas each having a different helical winding diameter and having cores formed of synthetic resin hollow pipes having different diameters are electrically connected to each other, wherein n-1 helical antennas are provided. The helical antenna according to claim 1, wherein the element is smaller than the core inner diameter of the nth helical antenna element and is coaxially fitted and connected.