JPH0746026A - Helical antenna - Google Patents

Abstract

PURPOSE:To provide a compact and high performance helical antenna which can be easily manufactured by providing a dielectric board on a conductive substrate acting as the reflecter of a helical antenna, providing the conductive substrate on it, and constituting a microstripline. CONSTITUTION:An electromagnetic wave propagated through a coaxial line 3 is inputted through a center conductor 4 to the microstrip line constituted of a stripe conductive board 1, dielectric board 6, and grand substrate 2, and propagated through the line. Then, the electromagnetic wave is radiated through a helical conductor 5 to free air as the electromagnetic wave of circular polarization. Also, at the time of receiving the electromagnetic wave of circular polarization, it is received by the helical conductor 5, inputted through the conductor 5 to the microstripline. propagated through the line, propagated through the conductor 4 in the line 3, and received. As the result, the matching of the impedance of the helical conductor 5 with that of the coaxial line 3 can be attained, a reflection loss can be sharply reduced, and miniaturization can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to performance improvement such as miniaturization of a helical antenna, and more particularly to performance improvement of a helical antenna by providing new feeding technology.

[0002]

2. Description of the Related Art Helical antennas have been put to practical use as antennas that generate circularly polarized waves.

For example, as shown in FIG. 1A, the structure is provided with a reflection plate, a helix conductor portion for generating circularly polarized waves, and a coaxial line having a center conductor connected to the helix conductor. Composed.

By the way, the input impedance of the helical antenna becomes almost constant when the length of the helix conductor, that is, the helix length exceeds about twice the wavelength of the radio wave to be transmitted and received, and its value is approximately. 100 to 15
It is known to be about 0 (ohm).

Therefore, since the characteristic impedance of a commonly used coaxial line is 50 (ohm), it is necessary to match the impedances of the two when connecting the coaxial line and the helix conductor.

Various methods have been proposed in the past for achieving such matching, and the typical ones are as follows.

First, as shown in FIG. 1 (b), a structure in which a taper portion is provided at the base of a helix conductor is used, and the impedance is gradually changed to match the impedance, or as shown in FIG. , A method of constructing a helical antenna by shortening the length (the portion indicated by d in FIG. 2) of the connecting portion of the coaxial line which is the power feeding line and the helix conductor, and bringing the helix conductor closer to the reflection plate, and further, FIG. As shown in (a), the center conductor of the coaxial line, which is the feeding point, is arranged not on the central axis of the helix conductor but on an extension line of a certain point on the circumference of the helix conductor toward the reflector. There was a way to configure.

[0008]

By the way, the above-mentioned prior art has the following problems. First of all, in the method shown in FIG. 1B in which the taper portion is provided at the base of the helix conductor, the length of the taper portion, which is originally unnecessary for transmitting and receiving circularly polarized electromagnetic waves, becomes long, As a result, there is a problem that the helical antenna becomes large as a whole.

Secondly, in the method of shortening the length of the connecting portion between the coaxial line, which is a feeder line, and the helix conductor, and bringing the helix conductor closer to the reflector, no connecting portion is provided, that is, Setting the length of the connecting portion (the portion indicated by d in FIG. 2) to "0 (mm)" is impossible in manufacturing, and the length of the connecting portion is extremely "0 (mm)". Even if it becomes possible to make the value close to, the length of the connecting portion cannot be shortened until the input impedance of the helical antenna and the impedance of the commonly used coaxial line become “50 (ohm)”. .

Further, when the center conductor of the coaxial line, which is the feeding point, is arranged not on the center axis of the helix conductor but on an extension of a certain point on the circumference of the helix conductor toward the reflector, Both the center axis of the feed line and the center axis of the helix conductor are misaligned, the center of gravity of the entire helical antenna does not exist in the center of the reflector, and the balance is poor when mounting the helical antenna. There is a problem in that workability is reduced and durability is reduced.

[0011]

In the present invention, the following means are conceivable in order to solve the above problems.

That is, the first conductor plate acting as a reflection plate, the dielectric plate provided on the conductor plate, the second conductor plate provided on the dielectric plate, and the circularly polarized wave are radiated. The configuration includes a helix conductor and a coaxial line that propagates electromagnetic waves.

A hole is formed through the first conductor plate and the dielectric plate so that the center conductor of the coaxial line is not in contact with the first conductor plate. The structure may be such that it is connected to the second conductor plate through holes provided in the first conductor plate and the dielectric plate, and further, the end points of the helix conductor are connected to the second conductor plate.

[0014]

As described in the above means, by providing a dielectric plate on a conductive substrate acting as a reflection plate of a helical antenna, and by providing a conductive substrate on the dielectric plate, this portion is a microstrip line. Make up.

The microstrip line has a predetermined impedance and a function of propagating an electromagnetic wave.

Therefore, when the electromagnetic wave is supplied from the coaxial line, the electromagnetic wave propagates through the microstrip line and is further circularly polarized into the free space through the helix conductor connected to the microstrip line. Electromagnetic waves will be emitted.

On the contrary, the circularly polarized electromagnetic wave propagating in the free space is received by the helix conductor, the received electromagnetic wave propagates through the microstrip line, and further,
Electromagnetic waves propagate to the coaxial line.

As described above, in the above structure, a helical antenna that receives all circularly polarized electromagnetic waves is formed.

Further, in the microstrip line, the impedance is determined by the width and length of the conductive substrate, the dielectric constant of the intervening dielectric material, the thickness thereof, and the like. Then, the impedance of the coaxial line and the impedance of the helix conductor may be matched.

Further, since the conductive substrate forming the ground plane of the microstrip line is used as the reflection plate of the helical antenna, the connection between the helix conductor and the center conductor of the coaxial line is also the second conductive substrate. This can be done more easily than before because it can be done via. That is, the central conductor of the coaxial line and the conductive substrate forming the ground plane are completely insulated by providing the dielectric plate.

With the above structure, it is possible to provide a small and inexpensive helical antenna which is easy to manufacture.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is an external view of one embodiment according to the present invention, and FIG. 5 is a sectional view of one embodiment according to the present invention.

In both drawings, 1 is a strip conductor plate and 2 is a strip conductor plate.
Is a ground board, 3 is a coaxial line, 4 is a center conductor,
5 is a helix conductor, and 6 is a dielectric plate.

The strip conductor plate 1 and the ground substrate 2 are
It may be made of a material having conductivity, for example,
It can be realized with a copper plate or the like.

The coaxial line 3 has a center conductor 4 at the center thereof.
The electromagnetic wave transmission means having the above, and a commercially available one may be used. In addition, the impedance of the coaxial line that is usually often used is often 50 (ohm).

The helix conductor 5 is a material having conductivity,
For example, it can be realized by winding a required number of copper wires.

The dielectric plate 6 may be any one as long as it is manufactured using a dielectric material. For example, it can be realized by quartz glass, lithium niobate (also referred to as “lithium niobate”), various synthetic resins, and the like.

The configuration will be described with reference to FIG.

The dielectric plate 6 is provided on the ground substrate 2, and the strip conductor plate 1 is further provided on the dielectric plate 6.

As can be seen from the drawings, it can be seen that the ground substrate 2, the dielectric plate 6 and the strip conductor plate 1 constitute a microstrip line.

In the embodiment shown in FIG. 3, the strip conductor plate 1 has a constant line width, but the line width is gradually narrowed, that is, the strip conductor plate 1 is formed in a tapered shape. Is also preferable.

Further, one end of the helix conductor 5 for generating the circularly polarized wave is connected to the strip conductor 1, and the center conductor 4 of the coaxial line 3 is provided on the ground substrate 2. The strip conductor 1 is connected to the strip conductor 1 through the opening and the dielectric plate 6.

It is also possible to make the opening provided in the ground substrate 2 larger than the cross-sectional shape of the coaxial line 3 and connect the tip end of the coaxial line 3 to the dielectric plate 6 by directly contacting it. The coaxial line 3 may be fixed by fixing the outer conductor of the coaxial line 3 to the ground substrate 2 so that the outer conductor is conductive.

Now, transmission / reception of circularly polarized electromagnetic waves by the helical antenna in this embodiment will be described.

First, transmission of circularly polarized electromagnetic waves will be described with reference to FIG.

The electromagnetic wave propagating through the coaxial line 3 enters the microstrip line through the center conductor 4 and is in the line (consisting of the strip conductor plate 1, the dielectric plate 6 and the ground substrate 2). Propagate.

The electromagnetic wave that has finished propagating in the microstrip line is radiated to the free space as a circularly polarized electromagnetic wave through the helix conductor 5.

Next, reception of circularly polarized electromagnetic waves will be described.

The incoming circularly polarized wave is received by the helix conductor 5, enters the microstrip line through the helix conductor 5, and propagates in the line.

The electromagnetic wave which has finished propagating in the microstrip line propagates in the coaxial line 3 through the central conductor 4, and the circularly polarized electromagnetic wave is received.

As described above, the helical antenna provided with the microstrip line constituted by the strip conductor plate 1, the dielectric plate 6, and the ground substrate 2 transmits and receives circularly polarized electromagnetic waves.

Next, the impedance matching method, which is the main part of the present invention, will be described.

In FIG. 4, the impedance of the coaxial line 3 is 50 (ohm), and the impedance of the helix conductor is approximately 100 to 150 (ohm). If this is left as it is, impedance mismatching causes reflection of electromagnetic waves, resulting in a helical antenna with large loss.

Therefore, the thickness and material of the dielectric material that constitutes the microstrip line through which electromagnetic waves propagate may be appropriately selected so that the impedance value of the microstrip line becomes a desired value. In the present embodiment, impedance matching can be achieved by selecting the thickness of the dielectric material and the material of the dielectric material so that the impedance value of the microstrip line is about 50 to 100 (ohm). , First of all considered.

It should be noted that setting the impedance of the microstrip line to a predetermined value by selecting the thickness and material of the dielectric is a well-known and publicly known technique, and this may be applied.

Secondly, the width of the strip conductor plate 1 is
As shown in FIG. 3, when the impedance is constant, the impedance of the microstrip line also has a constant value. Therefore, the impedance of the strip conductor plate 1 is gradually changed by tapering the impedance. Can also be considered. It is known that the impedance of the microstrip line having such a tapered strip conductor plate 1 gradually changes.

Therefore, at the connection portion with the central conductor, the impedance of the microstrip line is 50 (ohm), and at the connection portion with the helix conductor 5, the impedance of the microstrip line is about 100 (ohm). A configuration in which the width of the conductor plate 1 is gradually changed is preferable. It is a well-known technique that the impedance of the microstrip line is uniquely determined according to the width of the strip conductor plate 1, and if the width of the strip conductor plate 1 is determined using this technique. good.

As described above, it is possible to provide a small helical antenna in which impedance matching is performed by selecting the thickness and material of the dielectric plate and setting the width of the strip conductor plate 1. Of course, the use of such a matched antenna reduces the reflection loss of electromagnetic waves during transmission and reception, and enables transmission and reception of weak electromagnetic waves.

The length of the helical antenna provided with two turns of the tapered portion at the base of the helix is 55 (mm), whereas in the prototype of the helical antenna according to the present invention, the length is 40 (mm). And the total is 15 (m
m) has also become shorter.

Further, in the configuration according to the present invention, the upper and lower limits of the sending and receiving frequencies are not limited due to manufacturing reasons. The lower value is greater than 0 (Hz) and the upper value is several. Design up to the desired frequency band is possible up to 10 GHz (of course, higher frequencies are possible if necessary).

Further, the manufactured helical antenna is
It is provided and used in a system using circular polarization such as a BS broadcasting antenna. Of course, a system using circular polarization can be applied not only to the BS broadcast antenna but also to any system.

As described above, the power supply to the helix conductor is
By using a microstrip line, impedance matching between the helix conductor and the coaxial line can be achieved, reflection loss can be greatly reduced, and a helical antenna that can be downsized can be realized. .

[0054]

According to the present invention, it is possible to provide a helical antenna which is small in size, high in performance, and easy to manufacture.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a conventional helical antenna.

FIG. 2 is an explanatory diagram of a conventional helical antenna.

FIG. 3 is an external view of a helical antenna according to the present invention.

FIG. 4 is a sectional view of a helical antenna according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Strip conductor plate, 2 ... Ground substrate, 3 ... Coaxial line, 4 ... Center conductor wire, 5 ... Helix conductor, 6 ... Dielectric plate

Claims (2)

[Claims] 1. A first conductor plate acting as a reflector, a dielectric plate provided on the conductor plate, a second conductor plate provided on the dielectric plate, and a circularly polarized wave. A helix conductor and a coaxial line for propagating electromagnetic waves are provided, the first conductor plate and the dielectric plate are provided with holes penetrating them, and the center conductor of the coaxial line is
The second conductor plate is connected to the second conductor plate through a hole provided in the first conductor plate and the dielectric plate without contacting the first conductor plate, and the end point of the helix conductor is connected to the second conductor plate. A helical antenna characterized by being connected to a conductor plate. 2. The second conductor plate according to claim 1, wherein
A helical antenna having a taper shape in which a width is wide on a side connected to the central conductor and a width is narrow on a side connected to the helix conductor.