JPH09298418A - High gain planar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the antenna with a high radiation efficiency and with a narrow radiation beam and a high radiation gain with respect to the high gain planar antenna advantageous in a radio communication system using a microwave or a millimeter wave. SOLUTION: A ground conductor plate 2 is formed on one side of a 1st dielectric layer with a thickness equivalent to a half propagation wavelength and a 2nd dielectric layer 3 having a higher dielectric constant with a thickness equivalent to a 1/4 propagation wavelength is formed on the other side. Furthermore, an open resonator consisting of a 3rd dielectric layer 4 and a metallic patch 5 is formed in the middle of a bottom side of the 1st dielectric layer 1 in contact with the ground conductor plate 2. A leakage wave excited by the open resonator is emitted while being propagated through the 1st and 2nd dielectric layers to attain a narrow radiation beam and a high radiation gain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high gain plane antenna used in a radio communication system such as a microwave and a millimeter wave.

[0002]

2. Description of the Related Art Parabolic antennas are widely used to realize a transmitting / receiving antenna with a narrow radiation beam and high radiation gain. However, the parabolic antenna is large and heavy,
In addition, it is necessary to firmly attach the parabola and the feeding antenna element so as not to be affected by wind and snow, and there is a drawback that the cost becomes high.

Therefore, conventionally, a planar antenna having a patch antenna element formed on the surface of a thin dielectric layer has attracted attention because of its features such as thin shape, low cost and light weight. FIG. 4 shows a microstrip patch array antenna in which a plurality of antenna elements are arranged and connected between them by a feed line.

A plurality of patch antenna elements 10 are arranged at predetermined intervals on the surface of the dielectric layer 12 having the back surface on which the ground conductor plate 15 is formed. The four patch antenna elements 10 adjacent to each other are connected through a feed line 11 to form a sub array antenna 14. Further, these sub array antennas 14 are connected by a distributor 13. By feeding each patch antenna element 10 through the distributor 13 and the feeding line 11, a high radiation gain is achieved with a narrow radiation beam.

[0005]

In the conventional microstrip patch array antenna described above, the number of patch antenna elements must be significantly increased in order to improve the radiation gain. However, if the number of elements is increased,
In order to reduce electromagnetic coupling and leakage waves between the power feed lines, between the patch antenna elements, and between the power feed line and the patch antenna elements, the shape of the power feed lines becomes complicated and it takes time to design. Also, in a long feed line from the feed point to each patch antenna element, dielectric loss, conductor loss, radiation loss, and transmission loss due to electromagnetic coupling between the lines become large.
There is a limit to achieving high radiation efficiency.

Further, since the conductor of the feed line is on the same plane as the patch antenna element, parasitic radiation generated from the feed line is added to the radio wave radiated from the antenna element, which makes it difficult to realize an intended radiation pattern. .

[0007]

In order to solve the above problems, a high gain planar antenna according to the present invention propagates a leaky wave radiated from an open type resonator by using a multilayer dielectric structure having different permittivity. However, by concentrating the radio waves radiated at this time in the maximum radiation direction and effectively using them to increase the gain of the power of the leaky waves, excellent radiation characteristics can be easily realized without the design effort. To do so.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention propagates electric power supplied from an open type resonator while being reflected in multiple dielectric layers having different permittivities,
The feature is that the leaky waves radiated at this time are concentrated and combined in the maximum radiating direction, and the power of the leaky waves is effectively used for high gain. To achieve.

According to a second aspect of the present invention, the first dielectric layer having a thickness of ½ of the propagation wavelength and the first dielectric layer are formed on one surface of the first dielectric layer. Propagation wavelength 1
Second dielectric layer having a thickness of / 4 and a dielectric constant higher than that of the first dielectric layer, and a ground conductor plate formed on the other surface of the first dielectric layer. And an open type resonator provided in the first dielectric layer in the vicinity of the ground conductor plate, which allows multiple reflection along the interface between the first and second dielectric layers while propagating. The radiations of the leaky waves are concentrated and combined in the maximum radiation direction to achieve a narrow radiation beam and a high radiation gain.

The following are claims 1 and 2 of the present invention.
Embodiments of the invention described in 1) will be described with reference to the drawings. 1 (a) and 1 (b) are a cross-sectional view and a plan view, respectively, of an embodiment of a high gain planar antenna of the present invention. A ground conductor plate 2 is formed on one surface of the first dielectric layer 1 having a thickness h1 of ½ propagation wavelength, and a dielectric constant of the first dielectric layer 1 is formed on the other surface. Also has a large dielectric constant, and has a thickness h of 1/4 propagation wavelength.
A second dielectric layer 3 having 2 is formed. Also the first
In the center of the lower surface of the dielectric layer 1 of, in contact with the ground conductor plate 2,
A third dielectric layer 4 is provided whose dimensions are much smaller than those of the first dielectric layer 1 and the second dielectric layer 3.

The material of these dielectric layers is, for example, the first
The dielectric layer 1 is a high frequency low dielectric constant material typified by Teflon, and the second dielectric layer 3 is a high frequency high dielectric material typified by a ceramic containing barium titanate as a main component. As the third dielectric layer 4, a high frequency material having glass as a main component and having a dielectric constant intermediate between those of the first and second dielectric layers can be used as the index material.

A metal patch 5 having an area smaller than that of the third dielectric layer 4 is provided on the third dielectric layer 4, and the ground conductor plate 2, the third dielectric layer 4, and the metal patch 5 are provided. Due to
An open type resonator for sending electric power is formed in the two-layer structure of the first dielectric layer 1 and the second dielectric layer 3. Then, a small slot 7 is opened in the ground conductor plate 2 below the metal patch 5, and the central conductor of the coaxial wire 6 is passed through the third dielectric layer 4 and brought into contact with the metal patch 5, so that the open type Powering the resonator.

Next, the characteristics of the high-gain planar antenna having the above structure will be described with reference to FIG. FIG.
(A) is a schematic diagram which shows the radiation state of the electric wave of the said antenna. In the figure, the electric power supplied from the coaxial line is excited most in the vicinity of the resonance frequency of the open type resonator, and the main electric power is sent out to the two first and second dielectric layers.

Only a small part of the delivered electric power is radiated directly into the space, as indicated by arrow A. However, most of the rest is multiple-reflected between the ground conductor plate 2 and the second dielectric layer 3 having a high dielectric constant and converted into a leaky wave propagating along the first dielectric layer 1. And this leaky wave is
While propagating, it is radiated as a radio wave in the space (arrow B).

Here, the leaky wave repeats multiple reflections, and the first
The operating principle of radiation while propagating along the boundary between the dielectric layer 1 and the second dielectric layer 3 will be described in detail with reference to FIG. As shown in FIG. 3A, a part of the radio wave input to the first dielectric layer 1 is reflected by an interface between the first and second dielectric layers (arrow A), and a part of the radio wave is reflected. It penetrates and enters the second dielectric layer 3 (arrow B). Then, a part of the transmitted electric wave is reflected at the boundary surface between the second dielectric layer 3 and the air, and a part of the electric wave is transmitted and becomes a leak wave (arrow C).

As shown in FIG. 3B, the leaky wave propagates along the direction indicated by the arrow D and radiates radio waves in the direction indicated by the arrow E. The arrow F shows the radiation pattern of the leaky wave. The direction of the main beam to be emitted is determined by the ratio of the propagation velocity at the boundary surface to the speed of light in free space, and the shape of the main beam to be emitted is It is determined by the ratio between the attenuation coefficient of electric power due to the radiation amount of leaked waves and the propagation velocity.

FIG. 2B shows the power distribution on the equivalent radiation surface of the high gain planar antenna according to the present embodiment and the conventional microstrip patch array antenna shown in FIG. 4, respectively. In the conventional type shown by B in the figure,
The current density flowing into the patch has a half-period sinusoidal distribution, and the electric power component on the radiation surface is concentrated near the metal patch, and suddenly decreases with distance from the metal patch.

On the other hand, in the embodiment of the present invention shown by A in the figure, as described above, the main radio wave emitted from the open type resonator is changed into a leaky wave and propagates in the dielectric layer. Since it arrives far away, the power distribution is much slower than in the past. Therefore, the effective radiation area of the planar antenna in this embodiment is much wider than that of the conventional one.

FIG. 2 (c) shows the radiation pattern of the planar antenna of this embodiment and the radiation pattern of the conventional antenna shown in FIG. Whereas the conventional radiation pattern shown by B in the figure is a wide radiation beam consisting of direct radiation waves as described above, the radiation pattern of the present embodiment shown by A in the figure is radiation of a leaky wave. It is a narrow radiation beam consisting of.

FIG. 2 (d) shows the relationship between the radiation gain of the planar antenna and the thickness of the first dielectric layer 1 in this embodiment. The main beam of radiated radio waves is
The increase in the thickness h1 of the dielectric layer 1 causes the propagation velocity of the leaky wave propagating to the interface between the first and second dielectric layers as shown in the radiation pattern shown in FIG. 2 (c). It can be understood that it gradually approaches the direction perpendicular to the surface of the dielectric because it gradually slows down. Further, the main beam is such that the thickness of the first dielectric layer 1 is 1/2 the frequency.
At the propagation wavelength, as shown in FIG. 2C, the propagation velocity of the leaky wave becomes zero, and the power distributions on the radiation aperture plane become in-phase and vertical, resulting in high radiation gain. I understand.

It should be noted that the thickness h2 of the second dielectric layer 3 is such that the attenuation coefficient of electric power due to the radiation amount of the leaky wave is made small so that the effective radiation area of the antenna is maximized, and the thickness h2 of the radiation port surface is reduced. For the reason that the power distribution needs to be gentle, it is desirable to set the wavelength to 1/4 propagation wavelength.

As described above, according to this embodiment, the effective radiation area of the antenna is widened, and the vertical radiation beam is narrowed, so that the radiation gain can be increased.

In the above embodiments, the open type resonator is fed by the coaxial line, but a microstrip line composed of a metal conductor and a thin dielectric layer is formed on the ground conductor plate. It may be provided and configured to supply power by the electromagnetic coupling effect. Further, although the open type resonator is composed of the metal patch and the dielectric layer, it may be composed of other open type dielectric resonators or open type metal waveguide resonators.

[0024]

As described above, the high-gain planar antenna of the present invention excites a leaky wave with a two-layer dielectric structure by an open type resonator, and the leaky wave propagates through the dielectric layer in the space. By utilizing the characteristic of radiating radio waves to the antenna, it is possible to obtain an excellent radiation pattern with a narrow radiation beam and high radiation gain in the direction perpendicular to the dielectric surface. In addition, since there are no complicated feed lines for distributing power and many antenna elements for radiating radio waves into the space, transmission loss is very small, radiation efficiency is very high, and antennas are It can be miniaturized.

[Brief description of drawings]

FIG. 1 is a sectional view and a plan view showing a high-gain planar antenna according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing characteristics of the high gain planar antenna.

FIG. 3 is an explanatory diagram showing characteristics of the high gain planar antenna.

FIG. 4 is a perspective view of a conventional microstrip patch array antenna.

[Explanation of symbols]

 1 1st dielectric layer 2 ground conductor board 3 2nd dielectric layer 4 3rd dielectric layer 5 metal patch 6 coaxial line 7 slot

Claims (2)

[Claims] 1. An electric power supplied from an open-type resonator is propagated while being reflected in multiple dielectric layers having different permittivities, and leakage waves radiated at this time are concentrated and combined in the maximum radiation direction. A high-gain planar antenna characterized by effectively utilizing the power of leaky waves for high gain. 2. A first dielectric layer having a thickness of ½ of the propagation wavelength and a thickness of ¼ of the propagation wavelength formed on one surface of the first dielectric layer. Together with the first
Second dielectric layer having a higher dielectric constant than that of the dielectric layer, a ground conductor plate formed on the other surface of the first dielectric layer, and a first dielectric layer near the ground conductor plate. A high gain planar antenna having an open resonator provided in a body layer.