JPH027704A - Plane antenna - Google Patents

Abstract

PURPOSE:To improve the antenna efficiency by providing a feeder between two ground conductor plates so as to prevent the radiation loss due to undesired radiation from the feeder and to prevent the increase in the line loss. CONSTITUTION:A 1st ground conductor plate 3 is formed on the upper face different from the forming face of the antenna element 1 of the dielectric board 2 supporting the antenna element 1, the conductor is removed by a hole 3a with respect to the region of the antenna element 1 and the surrounding base is covered. Then a 2nd ground conductor plate 5 is arranged at an interval with respect to the dielectric board 2 with the 1st ground conductor plate 3 formed thereupon. The feeder 4 forms a microstrip line with the 1st ground conductor plates 3 while putting the dielectric base 2 between them and in this case, the 2nd ground conductor plate 5 acts like a shield plate. Thus, the antenna with a comparatively broad band characteristic, less feeder loss and a high efficiency is obtained.

Description

[Detailed description of the invention] Two chestnuts! The present invention relates to a microwave band flat antenna used for applications such as satellite broadcast reception.

Conventional ■ Chivalry Street In recent years, satellite broadcasting has been put into practical use in Japan, and several countries are also planning satellite broadcasting. These satellite broadcasts mainly use SHF radio waves in the 12GH2 band. As receiving antennas for receiving these SHF radio waves, high-gain pencil beam antennas such as parabolic antennas and planar antennas have been put into practical use. Among them, planar antennas have attracted attention in recent years because of their thinness, flat shape, good wind and snow resistance, and easy installation.

An example of a conventional planar antenna is shown in FIG. This figure shows a part of a conventional batch antenna array.
10 represents an antenna element, 10 represents a feed line, 11 represents a dielectric substrate, and 12 represents a ground conductor. Antenna element 9 constitutes a microstrip antenna together with dielectric substrate 11 and ground conductor 12. Note that the antenna Q value of the microstrip antenna changes depending on the thickness of the dielectric substrate 11. The feed line 10 is a dielectric substrate 11. The ground conductor 12 constitutes a microstrip line. Since the feed line 10 is connected to the antenna element 9, the signal received by the microstrip antenna is transmitted to the microstrip line, and the received signal is extracted from the microstrip line.

Conventional patch antenna arrays, such as those mentioned above, have good input VSWR (standing wave ratio) and a relatively narrow band. In order to overcome these disadvantages and achieve a wider band, it may be possible to increase the thickness of the dielectric substrate to lower the Q value of the antenna, but in this case, the line loss in the microstrip line increases and it becomes difficult to achieve high efficiency. The problem is that it cannot be done.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a planar antenna that has a simple structure and can achieve high efficiency.

In the present invention, a first ground conductor plate is provided on a dielectric substrate on which an antenna element and a feed line connected to the antenna element are formed, covering at least the periphery of the substrate except for the surface on which the antenna element is formed. A planar antenna is constructed by arranging a second ground conductor plate at a distance from the dielectric substrate on which the first ground conductor plate is formed.

With the above-described configuration, the second ground conductor plate spaced apart from the dielectric substrate forms a microstrip antenna together with the antenna element on the dielectric substrate, and the antenna element covers the antenna element area. Since the first ground conductor plate is located at the periphery, it receives radio waves as a microstrip antenna.

With this type of antenna structure, there is no need to thicken the dielectric substrate itself in order to widen the band, and since the feed line is sandwiched between two ground conductor plates, radiation loss due to unnecessary radiation from the feed line is reduced. This prevents line losses from increasing and improves antenna efficiency. In addition, in a microstrip antenna, the Q value of the antenna decreases as the dielectric constant between the antenna element and the second ground conductor plate decreases, but in the present invention, since the air layer is formed, the Q value of the microstrip antenna
The value becomes smaller, and it is possible to create a broadband antenna. In addition, the distance between the antenna element and the second ground conductor plate and the thickness of the dielectric substrate between the feed line and the first ground conductor plate can be designed separately, so the antenna can be designed to optimize the microstrip antenna and the feed line, respectively. The distance between the element and the second ground conductor plate and the thickness of the dielectric substrate can be selected.

Tsuke” L plate Examples of the present invention will be described in detail below.

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, in which 1 represents a conductor serving as an antenna element, 2 represents a dielectric substrate supporting the antenna element 1, and 3 represents the antenna element 1 of the dielectric substrate 2. The conductor is formed on an upper surface different from the surface on which the antenna element is formed, and the conductor is removed from the hole 3a in the region of the antenna element l,
This is a first ground conductor plate formed to cover the peripheral board portion. 4 is a conductor that becomes a feed line connected to the antenna element l, 5 is a second ground conductor plate on the lower side of the dielectric substrate 2, and 6 is a conductor that connects the second ground conductor plate 5 from the dielectric substrate 2. A spacer for separation is shown.

The conductor patterns of the antenna element 1, the upper first ground conductor plate 3, and the feed line 4 are fabricated by etching copper foil formed on both sides of the dielectric substrate 3. Further, the spacer 6 is made of a dielectric or a conductive material, and in the case of a conductor, it is provided at a position away from the antenna element 1 and the feed line 4 to such an extent that it does not have a large effect on the electromagnetic field thereof. When the spacer 6 is a conductor, it can also be manufactured integrally with the second ground conductor plate 5. antenna element 1
The shape is an antenna element used in a known microstrip antenna, and forms an unbalanced resonant circuit with the second ground conductor plate 5.

The Q of a microstrip antenna in which an antenna element and a ground conductor plate are respectively arranged on both sides of a dielectric substrate having a thickness and a relative dielectric constant ε can generally be expressed by the following equation.

However, C6i speed of light in free space f1; resonant frequency In the structure of this embodiment, there is an air layer between the antenna element 1 and the second ground conductor plate 5, and the equivalent dielectric constant corresponding to ε in the above equation is It becomes l. Generally, the dielectric constant of dielectric substrate is 2~
Since it is about 10, the microstrip antenna of this embodiment sandwiching an air layer has a lower Q than the conventional microstrip antenna. In other words, it becomes a broadband microstrip antenna. By the way, as described above, the first ground conductor plate 3 is provided in a shape excluding the area of the antenna element 1 on the surface of the dielectric substrate, so it does not have a large effect on the directivity of the microstrip antenna. Power feed line 4
forms a microstrip line with the first ground conductor plate 3 with the dielectric substrate 2 in between, and at this time the second ground conductor plate 5 functions as a shielding plate. Further, when the height between the second ground conductor plate 5 and the feed line 4 is approximately the same as the thickness of the dielectric substrate 2, the feed line 4 is connected to the first ground conductor plate 3. It can be considered that a stripline line is formed between the second ground conductor plates 5.

When a feed line configured as in this embodiment is compared with a conventional microstrip line, the relative dielectric constant between the line and the ground conductor plate is small, so there is no radiation loss from the line, and the line loss is small. When creating a large-area array like a satellite broadcasting antenna, discontinuities such as curved lines and impedance conversion sections are avoided, and there is a problem in that the radiation loss from these discontinuities becomes particularly large. The feed line configured as in the embodiment described above is effective in reducing line loss.

Note that FIG. 2 is a diagram of the dielectric substrate 2 viewed from the antenna element 1 side. In the figure, the position of the hole 3a provided in the first ground conductor plate 3 is indicated by a broken line. As shown in FIG. 2, in a structure in which the antenna element 1 and the feed line 4 are connected on the same plane, the radio waves passing through the hole 3a of the first ground conductor plate 3 are received by the antenna element, The signal is guided to the feed line 4 and taken out from the end of the feed line 4 as a received signal. At this time, since this embodiment uses a wideband antenna and has a low-loss feed line configuration as described above, the received signal can be extracted efficiently.

FIG. 3 is a sectional view showing another embodiment of the present invention.
The same parts as in the figure are indicated by the same reference numerals. In this embodiment, the antenna element 1 is formed on the same surface as the first ground conductor plate 3 on the dielectric substrate 2, the feed line 4 is formed on the opposite surface of the dielectric substrate 2, and the antenna element 1 is formed on the same surface as the first ground conductor plate 3. and the feed line 4 are connected by a conductor bottle or through hole 7 penetrating the substrate 2.

In the case of this embodiment, the equivalent dielectric constant between the antenna element 1 and the second ground conductor plate 5 arranged at a distance has a value larger than 1 due to the presence of the dielectric substrate 2. . However, the thickness between the antenna element 1 and the second ground conductor plate 5 is increased by the thickness of the substrate compared to the structure shown in FIG. In general, as the distance between the antenna element and the ground conductor plate increases, the Q value decreases, and even if the dielectric constant becomes greater than 1 as in this example, the Q value as an antenna decreases because the distance increases. It won't be that expensive. Furthermore, since there is no dielectric material on the top surface of the antenna element 1, there is no loss that occurs when radio waves pass through the dielectric substrate.

FIG. 4 is a diagram showing a third embodiment of the present invention, in which the same parts as in the first embodiment are designated by the same reference numerals. In this embodiment, a conductor plate formed by press working or the like is used as the first ground conductor plate 3, and a hole 3a provided in the ground conductor plate 3 is inserted between the dielectric substrate 2 and the first ground conductor plate 3. It is constructed by arranging spacers 8 with holes 8a formed at the same position.

In the case of this embodiment, the dielectric substrate 2 is formed of a thin film-like sheet to reduce the thickness of the dielectric above the antenna element 1, thereby reducing loss when radio waves pass through the dielectric portion, and By setting the thickness between the feed line 4 and the first ground conductor plate 3 so that the line loss is minimized, a more efficient antenna can be obtained.

As explained above, the planar antenna of the present invention can be a highly efficient antenna with low feed line loss while having relatively wide band characteristics as an antenna element. Therefore, if a large number of antennas according to the present invention are arranged in a plane to form an array antenna, a highly efficient satellite broadcast receiving antenna can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is a plan view of a conductor pattern made on a dielectric substrate in the same embodiment, and FIG. 3 is a cross-sectional view showing another embodiment of the present invention. 4 are sectional views showing still another embodiment of the present invention, and FIG. 5 is a perspective view showing a conventional example. 1-Antenna element. 2...-dielectric substrate. 3--First ground conductor plate. 4-Feed line. 5--Second ground conductor plate. 6...-Spacer. 7.-Conductor pin. 8.--Spacer. Embedded by applicant Sharp Co., Ltd.

Claims (1)

[Claims] (1) An antenna element formed on one surface of a dielectric substrate, a first ground conductor plate formed to cover a peripheral portion of the dielectric substrate surface excluding the antenna element area, and a first ground conductor plate formed on the dielectric substrate surface. a feed line formed in the antenna element and connected to the antenna element;
A planar antenna comprising: a second ground conductor plate disposed at a distance from the dielectric substrate.