JPH06296110A - Triplate type plane antenna with parasitic element - Google Patents

Abstract

PURPOSE:To provide the plane antenna in which no gain reduction is caused and a side lobe level due to line spurious radiation is not increased. CONSTITUTION:In the triplate type plane antenna with parasitic element formed by a ground conductor 1, an antenna printed circuit board 3 with a radiation element 5 and a feeder 6 or the like formed on the face of the ground conductor 1 via a dielectric material 2a, a slot board 4 having a slot 7 placed on the side of the board 3 in a way that the slot 7 comes just above the radiation element 5, and a parasitic board 8 with a parasitic element 9 formed on the side of the slot board 4 via the dielectric material 2c in a way that the parasitic element 9 comes just above the radiation element 5 and the slot 7, the size L of the slot 7 is set to be a 0.9 to 1.0 times the size (a) of the radiation element 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low sidelobe planar antenna used for transmission and reception in a microwave band.

[0002]

2. Description of the Related Art As a means for improving the antenna efficiency of a plane antenna, there is a method of reducing the loss of a feed line by using a triplate line. As a method of constructing an antenna of this kind, as shown in FIG. 5, an antenna circuit board 3 having a radiation element 5 and a feed line 6 and the like formed on a surface of a ground conductor 1 via a dielectric 2a is installed, and on the surface thereof. A slot plate 4 having a slot 7 is formed on the radiating element 5 via a dielectric 2b so that the slot 7 is directly above the radiating element 5, and the dielectric 2c is formed on the surface thereof.
There is an antenna configuration in which the parasitic board 8 on which the parasitic element 9 is formed is disposed so that the parasitic element 9 is directly above the radiating element 5 and the slot 7.

In this configuration, the radiating element 5 and the parasitic element 9
Are electromagnetically coupled, and when radiating the power supply,
Compared to the configuration without the parasitic element 9, the component propagating in the lateral direction between the ground conductor 1 and the slot plate 4 is reduced, and the component radiated from the parasitic element 9 directly to the space is increased, so that the efficiency is high. A plane antenna having wide band characteristics can be realized. The details have already been reported by the authors at the 1992 IEICE Spring National Convention (Preliminary Report, B-61).

Further, in order to realize highly efficient characteristics in this structure, the thickness of the dielectrics 2a, 2b, 2c is 0.1λ ₀ or less, where λ ₀ is the free space wavelength of the utilization center frequency. The dimensions of the slots 7 have to be about 0.6λ ₀ , and the arrangement intervals have to be about 0.86λ ₀ .

[0005]

In the antenna having the configuration shown in FIG. 5, the unwanted radiation from the line 6 exposed inside the slot 7 increases as the center frequency of use increases. Further, as shown in FIG. 6, fringing of the line 6 also increases, so that the remaining metal portion of the slot plate 4 in which the slot 7 is formed deteriorates in its function as the upper ground conductor of the triplate line, and the metal from the slot is removed. Unwanted line emissions also increase. Therefore, in the conventional configuration, the gain is reduced due to the effect of unnecessary radiation on the line as the use center frequency increases, and
As shown in, there is a problem that the side lobe level rises and the low side lobe characteristic below the specified side lobe level cannot be realized.

The present invention provides a planar antenna that does not cause gain reduction and does not raise the sidelobe level due to unwanted radiation from the line.

[0007]

As shown in FIG. 1, the present invention is an antenna in which a ground conductor 1 and a radiating element 5 and a feed line 6 are formed on a surface of the ground conductor 1 with a dielectric 2a interposed therebetween. A circuit board (3) is installed, and a slot plate (4) having a slot (7) on the surface of the circuit board (3) is installed so that the slot (7) is directly above the radiating element (5) and the surface of the slot plate (4) is A triplate plate with a parasitic element configured by installing a parasitic substrate 8 on which a parasitic element 9 is formed via a dielectric 2c so that the parasitic element 9 is directly above the radiating element 5 and the slot 7. In the planar antenna, the dimension L of the slot 7 is 0.9 to the dimension a of the radiating element 5.
Set to 1.0 times.

Further, in the present invention, in the configuration shown in FIG.
Dielectric 2a, 2b, and set to 0.1 times or less of free space wavelength lambda ₀ of the use central frequency a thickness h of the 2c, yet the array antenna configuration shown in FIG. 2, the arrangement interval of the two orthogonal directions P ₁ , P ₂ is set in the range of 0.82 to 0.86 times the free space wavelength λ ₀ of the utilization center frequency.

Dielectrics 2a, 2 used in the antenna of the present invention
For b and 2c, it is desirable to use foamed polyethylene or polypropylene having a relative dielectric constant of about 1.1 or less, and the shape of the radiating element 5, the slot 7 and the parasitic element 9 is a commonly used square, rectangle or A circular patch can be used, but in the case of a square, the length a of one side of the radiating element 5 is determined by the free space wavelength λ of the used center frequency.
It is desirable to be about 0.35 to 0.4 times ₀ , and the length b of one side of the parasitic element 9 is 0.25 to 0.3 of λ ₀ .
It is desirable to be about 5 times.

[0010]

The slot plate 4 of the tri-plate type planar antenna with a parasitic element of the present invention acts as an upper ground conductor of the tri-plate line constituted by the feed line 6 and the ground conductor 1, and the slot 7 is a radiating element. 5 is an opening for electromagnetically coupling the passive element 9 and the parasitic element 9. Here, by setting the dimension L of the slot 7 to 0.9 to 1.0 times the dimension a of the radiating element 5, the feed line 6 is not exposed inside the slot 7, and unnecessary radiation is suppressed. At the same time, since the remaining metal portion of the slot plate 4 in which the slots 7 are formed can be widened when arrayed, the shield effect for the feed line 6 is improved, and unnecessary radiation from the line can be suppressed. At this time, by setting the dimension of the parasitic element 9 to the radiating element 5 to an appropriate dimension, the power fed to the radiating element 5 is efficiently transmitted to the parasitic element 9 and radiated into the space, so that the slot 7 The gain does not decrease even if the size of is reduced. Further, by setting the thickness of the dielectrics 2a, 2b, 2c to be 0.1 times or less the free space wavelength λ ₀ of the utilization center frequency, fringing of the line can be suppressed,
Further, by setting the arrangement interval to be about 0.84 times λ ₀ ,
Since the component propagating in the lateral direction between the slot plate 4 and the ground conductor 1 can be utilized, high efficiency can be achieved, and an increase in side lobe level due to unnecessary radiation can be suppressed.

[0011]

FIG. 3 shows an embodiment of the present invention. The antenna configuration is as shown in FIG. 2, and the ground conductor 1 has a thickness of 1 m.
An aluminum plate having a thickness of 0.5 mm was used as the slot plate 4. Dielectrics 2a, 2
As b and 2c, polypropylene foam having a thickness of 1 mm and a relative dielectric constant of about 1.1 was used. Also, the antenna circuit board 3
Also, as the parasitic substrate 8, a substrate in which a PET film having a thickness of 25 μm and a copper foil having a thickness of 35 μm are attached is used, and the radiating element 5, the feeding line 6 and the parasitic element 9 are removed by etching unnecessary portions of the copper foil. Formed. The slot plate 4 was formed by pressing the slot 7. With the above structure, as shown in FIG. 3, the radiating elements 5, the slots 7, and the parasitic elements 9 are arranged in a vertical array of 4 rows and a horizontal array of 24 rows, and are arranged in two orthogonal directions.
The antennas were manufactured with the arrangement intervals in the direction being equal to 0.84 times the free space wavelength λ ₀ of the center frequency used. Here, the radiating element 5 is a square whose one side length a is 0.373 times λ ₀ and the one side length L of the slot 7 is equal to a, and the parasitic element 9 has one side length b of λ _0. Of 0.284
Doubled square. As a result of measuring the directivity at the utilization center frequency with this antenna, it was confirmed that low sidelobe characteristics below the required sidelobe level could be realized as shown in FIG. The gain at this time is about 28 dB and the efficiency is 70%.
The result was good. Further, the band of VSWR <1.5 was also about 10%, and a wide band characteristic could be obtained.

[0012]

As described above, according to the present invention, unnecessary radiation from the feed line due to an increase in the use center frequency can be suppressed, so that the low side lobe characteristic can be obtained over a wide band without causing the gain reduction. It is possible to provide a good planar antenna having the same.

[Brief description of drawings]

FIG. 1A is a plan view showing the basic structure of an embodiment of the present invention, and FIG. 1B is a sectional view showing the basic structure of the embodiment of the present invention.

FIG. 2 is a perspective view showing an array configuration of an antenna according to an embodiment of the present invention.

FIG. 3 is a plan view of an embodiment of the present invention.

FIG. 4 is a diagram showing a directional characteristic of an embodiment of the present invention.

5A is a plan view showing a conventional example, and FIG. 5B is a sectional view showing the conventional example.

FIG. 6 is a cross-sectional view for explaining the problems of the conventional example.

FIG. 7 is a diagram showing the characteristics of FIG.

[Explanation of symbols]

1. Ground conductors 2a, 2b, 2
c. Dielectric 3. Antenna circuit board 4. Slot plate 5. Radiating element 6. Power supply line 7. Slot 8. Parasitic board 9. Parasitic element

Claims (3)

[Claims] 1. A ground conductor (1) and a dielectric on the surface of this ground conductor (1).
Install the antenna circuit board (3) on which multiple radiating elements (5) and feed lines (6) are formed via (2a), and place the dielectric (2
The slot plate (4) having a plurality of slots (7) via b) is installed so that each slot (7) is directly above each radiating element (5), and the surface of the slot plate (4) is A parasitic board (8) with a plurality of parasitic elements (9) formed on top of it with a dielectric (2c) is attached to each radiating element (5) and each slot (7). In the triplate type planar antenna with a parasitic element installed so as to come to the top, the slot (7)
Is a dimension of 0.9 times to 1.0 times the dimension of the radiating element (5), a triplate type planar antenna with a parasitic element. 2. The dielectric according to claim 1, wherein the thickness of the dielectrics (2a), (2b), (2c) is 0.1 times or less of the free space wavelength λ ₀ of the utilization center frequency. Tri-plate type planar antenna with feeding element. 3. An array antenna in which elements comprising the radiating element (5), a slot (7) and a parasitic element (9) are arrayed in a matrix, and the array spacing in two orthogonal directions is defined as the center frequency of utilization. The triplate type planar antenna with a parasitic element according to claim 1 or 2, wherein the triplate type planar antenna is set in a range of 0.82 to 0.86 times a free space wavelength.