JPH0669718A - Stack type microstrip antenna - Google Patents

Abstract

PURPOSE:To obtain a high gain even if a main beam is formed in the direction of a small elevation angle by laminating a non-feeding patch, a two-points feeding excitation patch and a ground surface and exciting a two-points feeding patch at a secondary mode. CONSTITUTION:A dielectric substrate 22 where the non-feeding patch 21 is formed and a dielectric substrate 24 where the two-points feeding excitation patch 23 is formed on the upper surface and the ground surface 25 is formed on a lower surface are stack-supported by a spacer 26 with a prescribed space, and a hybrid circuit 28 is connected to the two-points feeding excitation patch 23 through a coaxial cable 27. An angle that the two feeding points of the two-points feeding excitation patch 23 and the center of an antenna patch makes is set to be 130 deg. or 45 deg.. Thus, the two-points feeding excitation patch 23 is excited at the secondary mode. Thus, the high gain can be obtained without deteriorating the gain in the antenna forming the main beam in the small elevation angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip antenna, and more particularly to a stack type microstrip antenna having a radiation pattern oriented in a low elevation angle direction.

[0002]

2. Description of the Related Art In recent years, a system using an artificial satellite as a relay station has been put into practical use in order to secure a communication line between a fixed station on the ground and a moving body such as an automobile or an aircraft. Considering the communication between terrestrial mobile stations, its operating range is limited to a certain range compared to aircraft, so the vertical directivity of the antenna to be used should match the elevation angle of the relay satellite. The variable range may be small.

In the case of using Inmarsat of the maritime communication satellite system, for example, considering Japan, the elevation angle for looking up Inmarsat from the ground is 35 to 55 degrees. Therefore, at least in Japan, the antenna has an elevation angle within this range. Is sufficient and no gain in the direction perpendicular to the antenna plane is required.

Generally, a microstrip antenna having characteristics such as thin shape, light weight, low profile, etc. is most suitable as an antenna used on the side of a moving body, and circular polarization which does not require tracking of polarization plane is effective. Further, the excitation modes of the microstrip antenna include fundamental mode excitation and secondary mode excitation. In the fundamental mode excitation, as shown in FIG. 1,
That is, the main beam 2 is formed in the front direction, whereas in the secondary mode excitation, the vertical section is divided into two in a heart shape as shown by the dotted line 3 and the elevation angle is low. Therefore, when relaying the above-mentioned ground-based mobile station communication by satellite, the secondary mode excitation is advantageous.

In order to construct a circularly polarized wave secondary mode excitation microstrip antenna as a mobile station antenna of the above system using the microstrip antenna, the conventional ones shown in FIGS. 3A and 3B are known. There is. The microstrip antenna shown in this figure has a dielectric substrate 4
Is provided with a ground conductor 5 on the back surface and a circular conductor patch 6 with a required diameter on the front surface. The patch 6 is transmitted by two coaxial lines 7 and 8 penetrating the ground conductor 5 and the dielectric substrate 4. A high-frequency signal that is supplied with or induces in the antenna patch is derived. Further, the two coaxial lines 7 and 8 are connected via a hybrid circuit 9 to a wireless transceiver (not shown), and the isolation terminal 10 of the hybrid circuit 9 is terminated by a resistor having a specified value. is there.

The connection points 12 and 13 of the two coaxial lines 7 and 8 to the antenna patch 6 form an angle of 135 degrees or 45 degrees between the two points and the center point 14 of the antenna patch 6.
In this configuration, the directivity of the antenna has a secondary mode excitation characteristic as shown by a dotted line 3 in FIG. In this configuration, the operation will be described by taking the case of transmission as an example. The high frequency signal from the transmitter is divided by the hybrid circuit 9 into two signals having a phase difference of 90 degrees, and two feeding points of the antenna patch 6 are provided. 12 and 13 are applied. It has already been explained that the angle between the two feeding points 12 and 13 and the center point 14 of the antenna patch 6 is about 135 degrees, but if the excitation is performed in the basic mode, this angle is usually 90 degrees.
Is generally set, and it is common to perform control for distinguishing between fundamental mode excitation and secondary mode excitation depending on the position of the feeding point. At this time, the patch diameter is larger than that in the basic mode.

However, in the basic mode excitation microstrip antenna, the frontal direction of the antenna has the maximum level and the gain is about 7 dB as described above.
In the vicinity of 55 °, the antenna gain becomes 0 dB or less, which is not applicable to the above system.

In addition, the microstrip antenna for secondary mode excitation has a peak value in the vicinity of an angle of elevation of 45 °, but even the original fundamental mode excitation does not have a sufficient gain, and the secondary mode excitation is performed. However, since the basic mode excitation pattern is divided into two patterns, the gain is further reduced, and it becomes impossible to satisfy the required value from the system. Therefore, it has been conventionally desired to develop an antenna gain increasing measure in this method.

[0009]

The present invention has been made in view of the above circumstances, and even when a main beam is formed in a small elevation angle direction, a stack-type micro that can be used as a high-gain antenna without lowering the gain. It is intended to provide a strip antenna.

[0010]

[Outline] In order to achieve the above object, the first invention of the present application is
In a stack type microstrip antenna in which a parasitic patch, a two-point feeding excitation patch, and a ground plane are sequentially laminated at a predetermined interval, the two-point feeding patch is excited in a secondary mode. The second invention of the present application is characterized in that each feeding point is arranged at a point where the feeding point isolation of the two-point feeding excitation patch is equal to or more than a predetermined value.

[0011]

The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a side sectional view showing an embodiment of the present invention. In the figure, 21 is a parasitic patch, which is formed on the upper surface of the dielectric substrate 22. Two
Reference numeral 3 denotes a two-point feeding excitation patch, which is formed on the upper surface of the dielectric substrate 24, and the ground surface 25 is formed on the lower surface of the substrate 24.
The stack 4 is supported by the spacer 26 at a predetermined interval. Further, a hybrid circuit (HYB) 28 is connected to the two-point feed excitation patch 23 via a coaxial cable.

Explaining the operation of this antenna, the HYB
From 28 to the two-point feed excitation patch 23, it operates as described in the prior art, but the parasitic patch 21 installed above the two-point feed excitation patch 23 acts like the director of the Yagi antenna, When the fundamental mode is excited, the beam width of the radiation pattern becomes narrower than the conventional mode of the antenna patch alone shown in FIG. 3, resulting in a gain of 8-9d.
It is known that B becomes 1 to 2 dB higher than the conventional value of 7 dB. This is referred to in References, Hori, Nakajima, "Broadband Coplanar Fed Circularly Polarized Microstrip Antenna," IEICE Transactions '85 / 4 Vol. J6
Since it is detailed in 8-BNo. 4, its explanation is omitted.

Therefore, the present invention is characterized in that the second mode is excited by this structure. As a result, the radiation pattern of the present invention has a higher gain of the fundamental mode than that of the conventional one as shown in FIG. Even if this basic mode pattern is divided into two, the gain is improved as compared with the conventional one, and the system requirement can be satisfied.

Here, in order to excite the antenna in the secondary mode, the feeding position for the excitation patch 23 is set as follows. That is, as in the conventional case, the angle formed by the two feeding points and the center point of the antenna patch is set to 90 degrees for excitation in the fundamental mode, but this angle is set to 135 degrees for the secondary mode excitation. Or 45 degrees. With this configuration, it is possible to obtain a high gain in the elevation angle direction, which is smaller than that of the conventional microstrip antenna, as described above.

The present invention has the following modifications.
Further, gain and isolation can be improved. FIG. 2 is a plan view for explaining a modified embodiment of the present invention. The feature of this embodiment is that the angle formed between two feeding points and a patch center point in a feeding patch is changed, Set the feed point isolation to the best one.
That is, in the conventional case, in the case of the fundamental mode excitation, the feeding angle is 9
The 0 degree, secondary excitation mode was 135 degrees or 45 degrees, but the applicant of the present application found that there is an angle at which the feeding point isolation is optimum by changing this angle variously. Therefore, if this idea is applied, the performance of the strip antenna can be further improved.

[0016] For example, the embodiment shown in FIG. 2 1600MH the use frequency _Z, diameter about 110mm parasitic antenna patch 21 and the excitation antenna patch 23, when the distance between them and 4 mm, about the feeding point angle The best isolation was obtained at 150 degrees. At this time, the dielectric substrates 22 and 24 were Teflon substrates having a dielectric constant of about 2.6. Furthermore, by using this means, it is possible to improve the isolation while maintaining the good gain and directional characteristics even if the distance between the excitation patch and the parasitic patch is narrowed, so that it is very effective in downsizing the antenna. is there. It should be noted that if the parameters of the antenna are different, the feeding point angle has an optimum angle according to the parameter, so the best point may be appropriately found.

Further, it is obvious that the above-mentioned antennas may be arranged and applied to an array antenna for controlling the beam direction by controlling the feeding phase shift of each of them.

[0018]

Since the present invention is configured as described above, it is possible to suppress a decrease in gain and a decrease in feeding point isolation in an antenna that forms a main beam in a direction with a small elevation angle.
It is effective in achieving excellent characteristics.

[Brief description of drawings]

FIG. 1 is a sectional configuration diagram showing an embodiment of the present invention.

FIG. 2 is a plan view showing a modified embodiment of the present invention.

3A and 3B are views showing a conventional microstrip antenna, in which FIG. 3A is a side sectional view and FIG. 3B is a plan view.

[Explanation of symbols]

1 ... Perpendicular line, 2 ... Main beam perpendicular to the antenna plane, 3 ... Beam with an elevation angle of 45 degrees, 4, 22, 2
4 ... Dielectric substrate, 5, 25 ... Ground plate, 6 ... Antenna patch, 21 ...
..Wireless antenna patches, 7, 8, 27 ...
Coaxial cable for power supply, 9, 28 ... HYB (hybrid circuit)

Claims (2)

[Claims] 1. A stack type microstrip antenna in which a parasitic patch, a two-point feeding excitation patch, and a ground plane are sequentially stacked at a predetermined interval, wherein the two-point feeding patch is excited in a secondary mode. Stacked microstrip antenna. 2. The stack type microstrip antenna according to claim 1, wherein each feeding point is arranged at a point where the feeding point isolation of the two-point feeding excitation patch is equal to or more than a predetermined value.