JPH06112721A - Antenna device containing matching conductor for dielectric 1/4 wavelength exciting antenna - Google Patents

Abstract

PURPOSE:To ensure the matching between a dielectric 1/4 wavelength exciting antenna and a feeder cable in a wide band range. CONSTITUTION:A dielectric 1/4 wavelength exciting antenna ANT is provided with a 1st conductor 5 which is extending at a prescribed angle kept to the ANT and has an earth potential, a 2nd conductor 6 which is extending in the direction opposite to the conductor 5 against the ANT and also has an earth potential, a matching conductor 8 containing an inverse T-shaped conductor 7 which includes a 1st conductor element 71 that is electrically connected to the conductor 6 within a plane vertical to the ANT and a 2nd conductor element 72 that is electrically connected to the conductor 6 and extending in the same direction as the ANT and also in parallel to the ANT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of radiation directivity of a compact dielectric quarter-wave excitation antenna particularly suitable for transmission / reception in UHF band.

[0002]

2. Description of the Related Art The present applicant has filed Japanese Patent Application No.
The new dielectric quarter-wave excitation antenna shown in (
Called antenna ANT). This antenna AN
T is a dielectric cylinder 1 having an appropriate length and inner and outer diameters.
With 01. An outer peripheral surface electrode 102 is formed on a part of the upper peripheral surface of the cylindrical body 101 by an appropriate method such as silver metallization. The outer peripheral surface electrode 102 is provided on the upper end surface of the cylindrical body 101.
And an outer peripheral edge thereof are connected to each other to form one end surface electrode 103, and further, an inner peripheral surface electrode 104 is formed on the entire inner peripheral surface of the cylindrical body 101, and an inner peripheral edge of the one end surface electrode 103 is connected to the inner peripheral surface electrode 104. To be done. In this way, the outer peripheral surface of the cylindrical body 101 is divided into the portion where the outer peripheral surface electrode 102 is formed and the remaining dielectric portion 105, and by appropriately selecting the area ratio between the outer peripheral surface electrode 102 and the dielectric portion 105, A desired antenna characteristic can be obtained.

A feeding conductor 106 having an appropriate diameter is inserted coaxially with the tubular body 101 in which the electrode is formed in this manner, and the lower end of the tubular body 101 is fixed to a connection plug 107. The center conductor 08 of the connection plug 107 is electrically and mechanically connected to the power feeding conductor 106. On the other hand, the upper end of the power supply conductor 106 is in contact with the inner peripheral surface electrode 104.
It is fixed by the fixing metal fitting 110 having 9 and thus the feeding conductor 106 is held coaxially with the inner peripheral surface electrode 104.

This antenna ATT differs from the conventional standing wave type antenna in the process of radiating radio waves. Conventional stationary antennas generate a magnetic field on the antenna surface by passing a high-frequency current through the antenna, and the electric field → magnetic field → electric field →
The electric wave is generated by the chained state of ... on the other hand,
Since the antenna ANT of FIG. 15 is provided with an electrode on the high dielectric constant cylinder 101 and is excited by ¼ wavelength compressed in the TEM mode, the periphery of the cylinder 101 is a resonance energy layer, that is, a strong electric field layer. Wrapped up. This antenna ANT is considered to be a point-wave source antenna, and like the conventional imaginary isotropic antenna, since the equiphase surfaces of the radio waves are on the same spherical surface within the effective radiation range, the antenna ANT is almost completely in the air. It was found that when it was installed floating, there was no vertical or horizontal wavefront, and its radiation was spherical.

FIG. 16 is a diagram showing the radiation pattern (solid line) of the antenna ANT of FIG. 15 together with the radiation pattern of the conventional standard dipole (dotted line) and the radiation pattern of the 1/2 wavelength whip antenna (dashed line). In addition, in FIG. 16, since the antenna ANT is supported by the metal supporting column, a null is generated in the axial direction of the supporting column. From FIG. 16, it can be seen that the radiation pattern of the antenna spreads vertically and its cross-sectional area is about 1 to 3 times that of a dipole or whip. Further, when the antenna ANT receives vertical polarization, 45-degree polarization, and horizontal polarization, the reception sensitivities are 70 each.
It was experimentally confirmed that they are dB, 75 dB, and 70 dB, and are not related to the plane of polarization.

However, this antenna ANT has the following drawbacks. (1) Even if the matching between the antenna ANT and the feeding coaxial cable is good and the SWR value is the minimum,
The lower radiation from the antenna ANT lowers the radiation efficiency of the antenna because it does not have its own plane of polarization. (2) The matching of the antenna itself is disrupted by the reflecting and absorbing objects around the antenna ANT, and the SWR value increases. (3) Since the antenna ANT is small, it is difficult to adjust the inside of the antenna from the outside.
(4) If the antenna is installed at a position where the lower radiation from the antenna ANT is reflected and absorbed by surrounding objects (for example, on the roof of a vehicle or on a steel pole), the launch angle becomes large and the radiation is not spherical. Hemispherical radiation will be emitted.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention has been made to solve the above problems, and a dielectric 1 which can be easily externally matched with a power feeding conductor.
It is an object to provide a / 4 wavelength excitation type antenna.

[0008]

In order to achieve the above object, an antenna device of the present invention comprises a dielectric 1/4 wavelength excitation antenna and a dielectric 1/4 wavelength excitation antenna at a predetermined angle. A first conductor extending at a ground potential, a second conductor extending in a direction opposite to the first conductor with respect to the dielectric quarter-wave excitation antenna and at a ground potential, and a second conductor Is electrically connected to the conductor of
A first conductor element lying in a plane perpendicular to the four-wavelength excitation antenna and a second conductor electrically connected to the second conductor and extending in the same direction as and parallel to the dielectric quarter-wave excitation antenna. And an inverted T-shaped conductor having a conductor element of
The dielectric quarter-wave excitation antenna is matched by adjusting the length of the first conductor.

In one embodiment, the antenna device of the present invention is made of Teflon for fixing the dielectric quarter-wave excitation antenna, the first conductor, the second conductor and the inverted T-shaped conductor. Equipped with a stand.

[0010]

[Operation] The first conductor, the second conductor, and the inverted T-shaped conductor 3
The two conductors function as matching conductors of the dielectric quarter-wave excitation antenna over a wide band by adjusting their lengths.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of one embodiment of a dielectric quarter-wave excitation antenna with a matching conductor according to the present invention will be described below with reference to the drawings.

FIG. 1a is a diagram schematically showing the structure of an embodiment of a dielectric quarter-wave excitation antenna with a matching conductor according to the present invention, and FIG. 1b is a view of the coaxial tube support in FIG. 1a. It is a figure which shows a structure. Hereinafter, the configuration will be described assuming that the dielectric quarter-wave excitation antenna with a matching conductor is vertically installed. 1A and 1B, a P-type plug 2 is provided at the lower end of the coaxial tube body 1, and a J-type plug 3 is provided at the upper end thereof. The J-type plug 3 has the antenna ANT described in FIG. It is installed. That is, the inner conductor 4 of the coaxial tube body 1 and the feeding conductor 106 of the antenna ANT are electrically connected.

The J-shaped plug 3 is fitted with a straight horizontal conductor 5 of an appropriate length which is electrically connected to the outer conductor 4'of the coaxial tube body 1 and extends horizontally from the coaxial tube body 1. Further, with respect to the antenna ANT, on the side opposite to the first horizontal conductor 5,
A second horizontal conductor 6 is provided which is collinear with the first horizontal conductor 5 and electrically connected to the outer conductor 4'of the coaxial tube body 1. Further, the second horizontal conductor 6 includes the second horizontal conductor 6
The inverted T-shaped conductor 7 has a horizontal side 7 ₁ which is perpendicular to the horizontal direction and which extends in the horizontal direction, and a vertical side 7 ₂ which is erected upward from the second horizontal conductor 6 in parallel with the antenna ANT. Mechanically connected. These first and second horizontal conductors 5 and 6
The inverted T-shaped conductor 7 constitutes a matching conductor 8 of the antenna ATT. The lengths of the conductors 5, 6, and 7 will be described in detail later.

Here, the difference in operation between the dielectric quarter wave excitation antenna with a matching conductor according to the present invention and the conventional standing wave antenna with a ground wire will be described. It should be noted here that although the conventional antenna with a ground wire and the dielectric quarter wave excitation antenna with a matching conductor according to the present invention have similar outer shapes, they differ in the excitation method of the antenna itself. Therefore, the operation is completely different.

In the conventional standing wave type antenna, a standing wave of high frequency current is placed on a metal conductor to generate a magnetic field on the antenna surface, and electromagnetic waves are generated in a chain of electric field → magnetic field → electric field → magnetic field. . An example of this is a dipole antenna, which is a donut (8-shaped) having a plane of polarization in its length direction.
It is well known to have a pattern of radiation patterns,
To make this a ground wire, the inner conductor of the coaxial cable is extended by 1/4 wavelength to form a radiating element, and two or four ground wires are provided in the open part of the outer conductor of the coaxial cable for feeding. Are usually arranged radially (FIG. 2a). If the ground wire is not provided, the return current flows to the outside of the outer peripheral surface conductor of the coaxial cable, and irregular radiation is generated. Therefore, a ground conductor is arranged to prevent this return current. In this way, when the ground wire conductors are installed, currents in opposite directions flow in the ground wires facing each other on the same line. Therefore, there is almost no radiation from the ground conductor. Moreover, the length of the ground conductor is about 1
Since it is / 4 wavelength, the impedance seen from the contact point with the outer conductor of the coaxial cable is very low (theoretical 0.8
The ground wire (which is -j2.8Ω) is equivalent to being directly grounded.

However, since the impedance at the feeding point of this radiating element is a small value of 20.4 + j4.1Ω, the radiating element does not match a normal coaxial cable having a characteristic impedance of 50Ω. Therefore, conventionally, in order to match the radiating element with the coaxial cable, the radiating element may be formed into a folded dipole (Fig. 2b), the position of the feeding point may be changed (Fig. 2c), or the respective ground conductors may be coaxial cables. It has been devised to point downward (Fig. 2d) so as to form an angle smaller than 90 degrees. However, since the ground wire affects the resonance of the radiating element, the standing wave antenna with the ground wire has a fatal drawback in that it cannot have wide-band characteristics.

On the other hand, the antenna AN shown in FIG.
As described above, T is excited by the ¼ wavelength compressed in the TEM mode, so that the antenna is surrounded by a layer of resonance energy, that is, a layer of strong electric field. Therefore, the antenna ANT is regarded as a point wave source and radiates a spherical shape. This is a point that is decisively different from the conventional standing wave antenna. However, there is a drawback in that a high-frequency current flows into the power feeding coaxial cable due to the radiation from the lower portion, and the radiation efficiency of the antenna ANT is reduced. Therefore, the inventor
In an attempt to overcome these drawbacks by using a conventional ground wire, an antenna ANT supported by a coaxial plug is provided with four conductors S _{1 having} a length of ¼ wavelength as usual as shown in FIG.
Radiating S ₂ , L ₁ and L ₂ to adjust the lower radiation,
An attempt was made to block high-frequency current flowing on the outer surface of the outer conductor of the coaxial plug. However, since the reflected wave was large and the SWR value was high, the antenna ANT and the coaxial plug could not be matched. As shown in FIG. 3b, two conductors L having a quarter wavelength are used.
_The results were the same when ₁ and L ₂ were provided.

However, it has been found that the antenna ANT and the coaxial connector can be almost completely matched with each other by combining the conductors having a structure completely different from the conventional ground wire. That is, as shown in FIG. 3c, the pair of horizontal conductors S ₁ and S ₂ facing each other is set to 0.2346 wavelength, and the remaining pair of horizontal conductors L ₁ and L ₂ is set to 1/4 wavelength. As the wavelength becomes longer, the antenna ANT near 0.2837 wavelength
It was possible to match the coaxial connector with the coaxial connector almost completely and in a wide band.

This is because the antenna ANT is a point wave source antenna, and the periphery of the antenna is surrounded by a layer of resonance energy, that is, a layer of strong electric field, so that the layers of electric field of equal phase are shown in FIGS. 3a, 3b and 3c. Magnetic field is generated on the surface of each conductor, and the generated magnetic fields interfere with each other to cancel the reactance of each conductor, so that the electrical length of each conductor is extremely shortened. result,
It is considered that the resonance frequency (tuning frequency) of the antenna ANT has increased. For this reason, the antenna ANT could not be matched in the case of FIGS. 3a and 3b in which the same ground wire as the conventional one is provided. On the other hand, in the case of FIG. 3c, it is considered that the area is related to the magnetic field due to the arrangement of the conductors S ₁ , S ₂ , L ₁ and L ₂ , so that it is found that the matching can be achieved almost completely in the wide band. did. This corresponds to the conductors S ₁ , S ₂ , L of FIG. 3c.
₁ , ₁ and ₂ indicate that the antenna ANT has a different action from the conventional ground wire.

The combination of conductors S ₁ , S ₂ , L ₁ and L ₂ is critical. This is shown in Table 1.

[0021]

[Table 1] Table 1 shows the SWR values measured for the cases of FIGS. 3a, 3b and 3c. according to this,
It can be seen that when the lengths of L ₁ and L ₂ are 0.2837 wavelengths and the lengths of S ₁ and S ₂ are 0,2346 wavelengths, matching is achieved over a wide band. The reason for this is as described above. On the other hand, in the case of only the horizontal conductors L ₁ and L ₂ and the horizontal conductor S
_In the case of only ₁ and S ₂ , mutual interference is reduced by the reduction of one set of horizontal conductors, and the area occupied by the magnetic field of each horizontal conductor is also related, resulting in a narrow band resonance. Furthermore, when all four antennas have the same length, the resonance frequency of the antenna ANT becomes high, which indicates that matching cannot be achieved.

Therefore, while keeping the lengths of the horizontal conductors L ₁ and L ₂ of one set constant, the lengths of the horizontal conductors S ₁ and S ₂ of the other set are set to 0. The SWR value was measured when the value was changed by 5 mm.
The results are shown in Table 2.

[0023]

[Table 2] From this, it can be seen that good matching can be achieved over a wide band when the horizontal conductors S ₁ and S ₂ are shortened to some extent.

However, mounting the horizontal conductor as shown in FIG. 3C has a disadvantage that the space occupied by the entire antenna is large. Therefore, as shown in FIG. 4a, the inventor leaves only _one horizontal conductor L ₁ and attaches a T-shaped conductor T to the opposite side of the horizontal conductor L ₁ with respect to the antenna ANT (these conductors L ₁ and T are Of course, it is electrically connected to the outer conductor of the coaxial plug C), and further, a vertical conductor U is provided downward along the coaxial plug C from the intersection of two conductors forming the T-shaped conductor T. (Fig. 4b). Table 3 below shows measured values of SWR values when the length of the vertical conductor U is fixed and the length of the horizontal conductor L ₁ is changed.

[0025]

[Table 3] In this case, the conductors L ₁ , T and U are connected to the antenna A.
Placed in the layer of the electric field of the bottom radiation of NT,
It can be seen that the magnetic fields generated by the respective conductors interfere with each other to cancel the reactances of the conductors, resulting in resonance at the target frequency. However, since the vertical conductor U is parallel to the coaxial plug C, stray capacitance occurs between them and increases the capacitive reactance. Therefore, the horizontal conductor L ₁ is lengthened to increase the inductive reactance and cancel the capacitive reactance. Must be and the matching conductor is not miniaturized.

Therefore, instead of the downward vertical conductor U,
As shown in FIG. 5, by providing the upward vertical conductor V, the stray capacitance between the coaxial plug C and the vertical conductor V can be eliminated, and the influence from the coaxial plug C can be eliminated. It was confirmed that the horizontal conductor L ₁ was also short.
In this way, the dielectric 1/4 with the matching conductor shown in FIG.
A wavelength-excited antenna was devised.

Now, returning to the dielectric quarter-wave excitation antenna with a matching conductor shown in FIG. 1, its characteristics will be described below based on various experimental results.

Table 4 shows that the length A of the first horizontal conductor 5 and the length B of the vertical side 7 ₂ of the inverted T-shaped conductor 7 are kept constant.
3 shows the SWR value when the length of the horizontal conductor 6 and thus the distance X between the antenna ANT and the vertical side 7 ₂ is changed.

[0029]

[Table 4] Table 4 shows that the distance X between the antenna ANT and the vertical side 7 ₂ slightly affects the matching of the antenna.
Vertical edge 7 placed in the mid-radiation of antenna ANT
_{The second} magnetic field is the first and second placed in the lower radiation
It is considered that this is because the magnetic field is stronger than the magnetic fields generated by the horizontal conductors 5 and 6.

Table 5 shows the length A and the interval X of the first horizontal conductor 5 which was confirmed to have a good SWR value in Table 4.
₂ shows the SWR value when the length B of the vertical side 7 ₂ is changed while keeping the constants.

[0031]

[Table 5] It can be seen from Table 5 that good matching is achieved over the range of 1260 to 1300 MHz.

Table 6 shows SWR values when the length A of the first horizontal conductor 5 is changed while keeping the length B of the vertical side 7 ₂ and the interval X constant.

[0033]

[Table 6] According to Table 6, good matching is possible in the range of 1260 to 1300 MHz, and even if the length of the first horizontal conductor 5 is changed to some extent, the SWR value can be maintained at 1.10 or less, for example. .

Next, parts for actually assembling the dielectric 1/4 wavelength excitation antenna with a matching conductor according to the present invention will be described with reference to FIGS. 6a, b, c
Antenna ANT, first horizontal conductor 5, second horizontal conductor 6
And a base 9 made of Teflon for fixing the inverted T-shaped conductor 7.
Is shown. The pedestal 9 has a through hole 10 for inserting the antenna ANT, a hole 11 for screwing a screw for fixing the antenna ANT, a hole 12 for screwing the first horizontal conductor 5, Hole 13 for screwing in the two horizontal conductors 6.

FIG. 7 shows the first horizontal conductor 5,
A screw 14 screwed into the hole 12 is formed at one end thereof. By screwing the first horizontal conductor 5 into the hole 12, the first horizontal conductor 5 is fixed and the coaxial connector 1 is connected to the outer conductor.

The second horizontal conductor 6 is, as shown in FIG.
Actually, it is a metal screw that also serves to fix the inverted T-shaped conductor 7 (FIG. 9). Inverse T by the second horizontal conductor 6
By screwing the rear surface of the one side 7 ₁ a mount 9 of the shaped conductor 7, connected also performed between the second horizontal conductor 6 and coaxial connector 1 of the outer conductor.

FIG. 10 shows a state in which a dielectric quarter-wave excitation antenna with a matching conductor is assembled using the above components. The antenna ANT is fixed to the base 9 with a screw 15, and the first horizontal conductor 5 is screwed into a hole 12 on the front surface of the base 9 and fixed. The second horizontal conductor 6 is screwed into the hole 13 of the base 9, whereby the inverted T-shaped conductor 7 is fixed. Further, both ends of the horizontal side 7 ₁ of the inverted T-shaped conductor 7 are provided with screws 16
It is fixed to the stand 9 by.

Various modifications of the dielectric quarter-wave excitation antenna with a matching conductor according to the present invention will be described below.
In FIG. 11, a circular conductor 16 is horizontally provided near the upper end of the antenna ANT, and the circular conductor 16 is provided on the vertical side 7 _{2 of the} inverted T-shaped conductor 7.
Is electrically and mechanically connected to the upper end of the. As a result, upward radiation from the antenna ANT is suppressed, and lower radiation is increased accordingly. Therefore, it is useful when used for an antenna of a fixed station of mobile radio, for example. 12
Is an example in which a rectangular flat reflector 17 is attached to the vertical side 7 ₂ of the inverted T-shaped conductor 7. Thereby, the radiation toward the rear can be suppressed and the radiation toward the front can be increased. Furthermore, FIG.
Shows an example in which a flat reflector 18 inclined from the upper end of the vertical side 7 ₂ toward the antenna ATT is provided to suppress backward and upward radiation. FIG. 14 is an example in which a reflector 19 having a corner reflector that covers the rear of the antenna ATT and a plane reflector that obliquely covers the antenna ATT is provided. Thereby, the radiation characteristic to the front of the antenna ANT can be improved.

Even when various reflecting plates are provided as in the case of FIGS. 11 to 14, the antenna ANT and the coaxial connector 1 are matched by adjusting the length of the matching conductor. be able to.

[0040]

As is clear from the detailed description of the dielectric quarter wave excitation antenna with a matching conductor according to the present invention as described above with reference to Examples and Experimental Examples, the present invention has the following special effects. Play.

(1) Even if the impedance of the dielectric 1/4 wavelength excitation type antenna changes depending on the installation conditions, the length of the conductor forming the matching conductor is adjusted so that the matching with the feeding cable can be performed externally. , Can be taken almost completely over a wide band.

(2) Since the conductor forming the matching conductor is shorter than the wavelength used, and the dielectric quarter-wave excitation antenna itself is also small, even if the matching conductor is mounted, the entire antenna will not be large. Instead, it is useful for small radios such as transceivers.

(3) Since the antenna does not depend on the plane of polarization, its sensitivity is hardly affected by fading even in a complicated plane of polarization such as a valley of a building, and stable operation can be performed.

(4) The structure is simple and can be manufactured at low cost.

[Brief description of drawings]

FIG. 1a is a dielectric 1 / with a matching conductor according to the present invention.
It is a figure which shows the whole structure of one Example of a 4-wavelength excitation type antenna, b is a figure which shows the coaxial connector used there.

2A, 2B, 2C and 2D are views for explaining the antenna of FIG.

3A, 3B and 3C are diagrams for explaining the antenna of FIG. 1, respectively.

4A and 4B are diagrams for explaining the antenna of FIG. 1 respectively.

5 is a diagram showing a prototype of the antenna of FIG. 1. FIG.

6A, 6B and 6C are a plan view, a side view and a rear view of a Teflon base used for the antenna of FIG. 1, respectively.

7 is a diagram showing a first horizontal conductor used in the antenna of FIG. 1. FIG.

8 is a diagram showing a second horizontal conductor used in the antenna of FIG. 1. FIG.

9 is a diagram showing an inverted T-shaped conductor used in the antenna of FIG. 1. FIG.

FIG. 10 is a plan view showing an actual structure of a dielectric quarter-wave excitation antenna according to the present invention.

11A, 11B and 11C are a front view, a side view, and a plan view, respectively, showing a modification of the present invention in which the antenna of FIG. 10 is provided with a circular conductor.

12A and 12B are a front view and a side view, respectively, showing another modification of the present invention in which the antenna of FIG. 10 is provided with a flat reflector.

13A and 13B are a front view and a side view, respectively, showing another modification of the present invention in which the antenna of FIG. 10 is obliquely provided with a flat reflector.

14A and 14B are a front view and a side view, respectively, showing a further modification of the present invention in which the antenna of FIG. 10 is provided with a corner reflector and an oblique flat reflector.

FIG. 15 is a diagram showing the structure of a dielectric quarter-wave excitation antenna.

16 is a diagram showing a radiation pattern of the antenna of FIG.

[Explanation of symbols]

1: coaxial plug, ANT: dielectric 1/4 wavelength excitation antenna, 5: first horizontal conductor, 6: second horizontal conductor,
7: Inverted T-shaped conductor 8: Matching conductor 9: Teflon base

Claims (2)

[Claims] 1. A dielectric quarter-wave excitation antenna, a first conductor extending at a predetermined angle from the dielectric quarter-wave excitation antenna and at ground potential, and the dielectric 1 / Regarding the four-wavelength excitation antenna, the first
Second conductor extending in a direction opposite to that of the second conductor and having a ground potential, and a first conductor electrically connected to the second conductor and in a plane perpendicular to the dielectric quarter-wave excitation antenna. An element and the dielectric 1 / that is electrically connected to the second conductor
A four-wavelength excitation antenna and an inverted T-shaped conductor having a second conductor element extending in the same direction and in parallel, and adjusting the length of the first conductor to make the dielectric 1 /
An antenna device characterized by matching a four-wavelength excitation antenna. 2. The dielectric quarter-wave excitation antenna,
The antenna device according to claim 1, further comprising a table made of Teflon (registered trademark) for fixing the first conductor, the second conductor, and the inverted T-shaped conductor.