JPH09199935A - Coplaner slot antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a coplaner slot antenna with excellent performance without employing a semispherical lens. SOLUTION: Slots 1a, 1b are formed by providing a ground conductor 3 on a multi-layer dielectric board formed by stacking boards 4a, 4b, 4c or the like with different dielectric constant and thickness equivalent to a 1/4 wavelength of a signal in the dielectric material and slots 1a, 1b are formed, and a coplaner waveguide 2 provided on the same face as the slots is used for an antenna input output transmission line. In the slot 1a or 1b formed in this way, only a signal in the TM0 mode is propagated in the lateral direction of the slot. Thus, the interval between the two slots 1a, 1b is adjusted to cancel the signal in the TM0 mode with each other so as to realize the slot antenna with very small surface wave loss. Furthermore, spurious radiation backward is suppressed up to a required level by selecting properly number of the dielectric boards and the dielectric constant, the radiation pattern is controlled to realize the objective antenna performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plane antenna mainly used for communication in a millimeter wave band or radar.

[0002]

2. Description of the Related Art FIG. 6 shows, for example, "A Uniplane 90
Giga Schottky Diode Millimeter Wave Receiver ", (IEE Transactions on Microwave Theory and Technics July 1995) [" A Uniplanar
90-GHz Schottky-Diode Mi
llimeter-Wave Receiver ",
(IEEE TRANSACTIONS ON MIC
ROWAVE THEORY AND TECHNIQ
UES, JULY 1995)], page 1669 of the coplanar slot antenna. In the figure, a ground conductor 3 is provided on the top surface of a dielectric substrate 4, and rectangular slots 1a, 1
b and the coplanar waveguide 2 are formed. Also, 5
Is an air bridge for the ground conductors on both sides of the coplanar waveguide 2 to maintain the same potential even at high frequencies, and 6 is a detector element.

In the conventional coplanar slot antenna of FIG. 6, a hemispherical lens 8 made of the same material is attached to the back side of the dielectric substrate 4 so that the thickness of the substrate is not extremely reduced and the substrate mode is reduced. It is possible to eliminate the surface wave loss due to. Further, the radiation effect can be narrowed by the lens effect, and the antenna gain can be improved.

[0004]

However, in the above-mentioned conventional coplanar slot antenna with a lens, the diameter of the lens 8 must be made considerably larger than the size of the slot itself in order to reduce the influence of aberration. For example, in the 90 GHz band design, the length of the slot is only 1.09 mm and the diameter of the lens is 12.7 mm.
Therefore, not only the advantage of the small size and light weight of the planar antenna is impaired, but also the loss of the millimeter wave signal due to the material of the lens becomes a problem.

In the conventional coplanar slot antenna with a lens shown in FIG. 6, it is desired to use a material having a high dielectric constant in order to reduce unnecessary radiation toward the rear air side. Surface reflection becomes a problem and it is required to attach a matching cap 9 made of another dielectric material, which complicates the structure and increases the manufacturing cost.

The present invention has been made to solve the above problems, and is a coplanar slot antenna that can achieve the same or better performance without using a hemispherical lens having a large volume and a high cost. The purpose is to realize.

[0007]

A coplanar slot antenna according to the present invention has two multi-layered dielectric substrates which are made by stacking dielectric substrates having different permittivities and predetermined thicknesses and which are parallel to each other. And a coplanar waveguide provided on the same surface is used as an antenna input / output transmission line.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In a slot provided on a substrate having a thickness corresponding to a quarter wavelength in a dielectric,
All substrate modes except 0 mode are shut off. Therefore, by arranging the two slots in parallel at a constant interval, it is possible to cancel the propagation of the TM0 mode, so that it is possible to realize a slot antenna with extremely small surface wave loss.

In a slot antenna formed on a multi-layer dielectric substrate made by stacking substrates having different dielectric constants and a thickness corresponding to ¼ wavelength in the dielectric, the number of dielectric substrates and the value of the dielectric constant are used. By appropriately selecting, it is possible to suppress unnecessary radiation to the rear, and it is also possible to control the radiation pattern according to the purpose.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (First embodiment)

FIG. 1 is a perspective view showing a coplanar slot antenna according to an embodiment of the present invention. In this embodiment, the dielectric substrates 4a and 4c have the same relative permittivity of 11.7.
As the silicon 4b, quartz having a relative dielectric constant of 3.8 is used. The thickness of each substrate is 1/4 wavelength of each dielectric period.
The two one-wavelength slots 1a and 1b are formed in the ground conductor 3 on the substrate 4a and are serially fed by a coplanar waveguide 2 having a characteristic impedance of 50Ω, and a transmitter or a receiver (illustrated in the figure) is provided through the coplanar waveguide 2. No)).

In FIG. 1, two single wavelength slots 1
In order to cancel the TM0 modes of a and 1b, the interval is set to a half wavelength of the TM0 mode. Further, in order to excite the two slots in the same phase, the length of the coplanar waveguide between the slots 1a and 1b is set to one wavelength in the coplanar waveguide 2 by bending as necessary.

Regarding the reflection loss at the input end of the above coplanar slot antenna, the finite difference time domain (FDT)
The results of analysis using the D) method are shown in FIG. At the center frequency (60 GHz in this design), the level of reflection loss is -30 dB or less and the relative bandwidth (standing wave ratio is defined as 2 or less) is about 13%, which is a very wide frequency for a planar antenna. Bandwidth can be realized.

(Second Embodiment) Next, another embodiment of the present invention will be described with reference to FIG. In this example,
A detector element 6 such as a Schottky diode is provided between the two one-wavelength slots 1a and 1b, and the slot 1a
The millimeter wave signals received by the signals 1 and 1b are detected by the detection element 6, and the obtained intermediate frequency signal is taken out through the low pass filter 7. In this way, the slot antenna and the receiver are integrated, and the problem that the loss of the millimeter-wave band transmission line is large can be solved, and at the same time, a very compact millimeter-wave band receiver can be realized. it can.

FIG. 4 shows the result obtained by an experiment at 60 GHz regarding the relationship between the H-plane directivity of the coplanar slot antenna and the number of dielectric substrates in the embodiment of FIG. In the dielectric substrate used in this experiment, 4a and 4c were alumina having a relative dielectric constant of 10.0, and 4b was quartz having a relative dielectric constant of 3.8. The thickness of each substrate is 1/4 of each dielectric
Wavelength. In addition, when increasing the number of dielectric layers,
These two types of substrates may be alternately stacked. From the experimental results shown in FIG. 4, it can be seen that the radiation beam width of the coplanar slot antenna can be narrowed by making the layers multi-layered, and the radiation pattern can be controlled to some extent by the number of dielectric layers.

FIG. 4 shows the H of the slot antenna.
The same tendency was confirmed for the E-plane as well, although it is the plane directional characteristic. FIG. 5 is a diagram also showing the experimental results of the E-plane and H-plane directional characteristics in the case of five layers. With the slot antenna using this 5-layer structure, a gain improvement of about 6 dB could be realized as compared with the 1-layer structure in which the dielectric substrate was only 4a.

In the coplanar slot antenna using the hemispherical lens shown in FIG. 6, the theoretical unnecessary emission to the rear air side is about -10 dB. On the other hand, as can be seen from the experimental results of FIG. 5, if the dielectric substrate in Example 2 has five layers, the unnecessary radiation toward the rear can be suppressed to the same degree. If you increase the number of boards,
It is possible to further reduce the level of the back lobe as compared with the conventional coplanar slot antenna of FIG.

Further, while the thickness of the conventional coplanar slot antenna shown in FIG. 6 including the lens is 8.65 mm, in the embodiment of FIG. 3, even when the dielectric substrate has five layers, Its total thickness is only 2.5 mm. In practical applications, such slot antennas are often used in the form of an array. In the conventional structure of FIG. 6, the lens diameter must be increased as the number of arrays increases. On the other hand, in the embodiment shown in FIG.
There is no need to increase the thickness of the substrate even if the number of arrays increases.

[0019]

As described above in detail, according to the present invention,
The antenna performance can be prevented from deteriorating due to surface waves without using a hemispherical lens, which has a large volume and is costly, and unnecessary radiation to the rear can be prevented by selecting the number of dielectric substrates and permittivity appropriately. Can be suppressed to the required level,
The beam width can be controlled, and it is possible to realize a highly efficient planar antenna that is extremely small and lightweight in the millimeter wave band.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a coplanar slot antenna according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an analysis result of a reflection loss at an input end of the coplanar slot antenna of FIG.

FIG. 3 is a perspective view showing a configuration of a coplanar slot antenna according to a second exemplary embodiment of the present invention.

FIG. 4 is a diagram showing an experimental result of directivity characteristics of the coplanar slot antenna of FIG.

5 is a diagram showing an experimental result of directivity characteristics of the coplanar slot antenna of FIG.

6A is a plan view showing a configuration of a conventional coplanar slot antenna, and FIG. 6B is a sectional view of the same.

[Explanation of symbols]

 1, 1a, 1b Slot 2 Coplanar waveguide 3 Ground conductor 4, 4a, 4b, 4c Dielectric substrate 5 Air bridge 6 Detection element 7 Low-pass filter 8 Hemispherical lens 9 Matching cap

Claims (1)

[Claims] 1. A coplanar structure in which two slots parallel to each other are provided on a ground conductor formed on a multi-layered dielectric substrate made by stacking substrates having different permittivities and predetermined thicknesses, and further provided on the same surface. A coplanar slot antenna characterized by using a waveguide as a transmission line for antenna input / output.