JP2000114847A - Array antenna and directional characteristic varying method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily change the directional characteristics. SOLUTION: Concerning an array antenna having plural antenna elements 12, this antenna element is divided into plural array groups A, B and C and a point 15 for feeding power to the antenna elements of each array group is separately set for each array group. By selecting the array group to feed power, the directional characteristics can be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array antenna and a method for changing the directivity of the array antenna.
In particular, the directional characteristics can be easily changed.

[0002]

2. Description of the Related Art Conventionally, a patch antenna used in a band higher than UHF has been known as a typical planar antenna. In this patch antenna, as shown in FIG. 5, a patch antenna element 62 made of a conductive thin plate is provided on a surface of a dielectric substrate 61, and a feeder 63 made of a microstrip line is provided on the patch antenna element 62. Connected.

This patch antenna has radiation directivity only on the side of the dielectric substrate 61 where the patch antenna element 62 exists.

[0004] In addition to feeding power to the patch antenna element 62, a method of feeding power from the back surface of the dielectric substrate 61 by a coaxial line through the dielectric substrate 61 or a microstrip line opposed to the dielectric substrate 61 with the dielectric substrate 61 interposed therebetween is used. There is also a method of feeding power by electromagnetic coupling with the antenna. However, as shown in FIG. 5, when the feeder 63 is provided on the same surface as the patch antenna element 62, the feeder is formed by etching simultaneously with the pattern formation of the patch antenna element. And it is easy to manufacture.

In this planar antenna, a plurality of patch antenna elements are formed on a substrate to form an array,
The directional characteristics can be narrowed down. FIG. 6 shows an example of an array antenna in which a plurality of patch antenna elements 52 and a feed line 53 for feeding power to each patch antenna element 52 are formed on a dielectric substrate 51.

[0006] Such an array antenna is, for example, an automatic toll collection system (Electronic Toll Collec) for toll roads.
(ETC).

The ETC system automatically communicates necessary information between an antenna installed above a lane of a tollgate and a vehicle-mounted device mounted on a vehicle, and automatically performs a toll charging process. With the introduction of this system, vehicles can pass through tollgates without stopping, and congestion at tollgates on toll roads can be eliminated.

However, vehicles traveling on toll roads include non-ETC vehicles that do not have an on-board device.
At the tollgate, ETC vehicles and non-ETC vehicles are distinguished in a mixed lane where ETC vehicles and non-ETC vehicles enter, and ET
Car C is automatically charged by wireless communication, while non-E
For TC vehicles, it is necessary to temporarily stop at a toll collection booth on the road side and collect the toll by the collection staff.

FIG. 7 shows an outline of a conventional ETC system. A first vehicle sensor 91 and a second vehicle sensor 92 for detecting passage of a vehicle by blocking light beams are arranged at a side of the lane at an interval of about 4 m.
An array antenna 93 for wireless communication with a TC vehicle is installed. Based on detection information from the first vehicle sensor 91, the second vehicle sensor 92, and the antenna 93, an ETC for a passing vehicle 95 is performed.
A roadside machine 94 that identifies whether the vehicle is a vehicle or a non-ETC vehicle and performs necessary processing is installed beside the lane.

In this system, when the vehicle 95 passes through the lane, the first vehicle detector 91 detects the passing vehicle, and transmits the detection information to the roadside device 94. The roadside device 94 transmits radio transmission from the antenna 93. Start.

When the vehicle 95 is an ETC vehicle, a vehicle-mounted device is installed on a dashboard inside the vehicle. When receiving the wireless signal from the antenna 93, the vehicle-mounted device transmits the stored information such as the departure place and the passage place. This information is received by the antenna 93 and sent to the roadside device 94. If there is a wireless response from the passing vehicle, the roadside machine 94 identifies this vehicle as an ETC vehicle and executes an automatic toll collection process. When the passing vehicle reaches the position of the second vehicle sensor 92, the second vehicle sensor 92 transmits the detection information to the roadside device 94, and the roadside device 94 stops the wireless communication by the antenna 93.

When the vehicle 95 is a non-ETC vehicle, there is no response from the passing vehicle even if radio waves are transmitted from the antenna 93. If there is no wireless response from the vehicle 95 before the second vehicle sensor 92 detects the passing vehicle, the roadside machine 94 identifies the passing vehicle as a non-ETC vehicle, and sets the vehicle at the toll collection booth. Instruct stop.

As described above, in the ETC system, a vehicle detection area is set by the two pairs of vehicle sensors 91 and 92, and a vehicle traveling in the detection area is wirelessly communicated. Cars and non-ETC vehicles are distinguished. Since the distance between the vehicle detector 91 and the vehicle detector 92 is set to a length that allows only one vehicle to enter, the ETC is applied to each vehicle traveling in the vehicle detection area.
It becomes possible to distinguish between a car and a non-ETC car.

However, in this ETC system, if the range of the radio wave from the antenna 93 is considerably larger than the vehicle detection area set by the vehicle sensors 91 and 92,
When a plurality of traveling vehicles enter the lane in a row,
An error may occur in the discrimination between the TC vehicle and the non-ETC vehicle.

For example, as shown in FIG.
5. In the case where vehicles enter the lane successively in the order of the ETC vehicle 96, when the preceding non-ETC vehicle 95 is detected by the vehicle detector 91 and communication from the antenna 93 is started, the following ETC vehicle 96 When the vehicle enters the range where the radio wave from the antenna 93 reaches, the vehicle-mounted device of the ETC vehicle 96 starts up and starts wireless communication with the antenna 93. As a result, the roadside machine 94 erroneously identifies the non-ETC vehicle 95 as a passing vehicle as an ETC vehicle.

In order to avoid such a misperception, it is necessary to narrow down the directional characteristics of the antenna 93 so that only the vehicle detection area becomes a communicable area as shown in FIG. 8A. An increase in the number of elements, adjustment of an element interval, and an amount of power supply to each element are performed.

[0017]

In this ETC system, it is necessary to set the interval between the two vehicle sensors 91 and 92 to be substantially the same as the vehicle length. Therefore, the approach lane for a large car and the approach lane for a small car are required. When provided separately, the distance between the two vehicle sensors 91 and 92 is set to be about the same as the length of a large car in the approach lane of a large car and about the same as the length of a small car in the approach lane of a small car. .

In this case, the directional characteristics of the array antenna
It is necessary to switch between the one installed on the approach lane of a large car and the one installed on the approach lane of a small car, and there is a demand for an array antenna that can easily change such directional characteristics.

An object of the present invention is to provide an array antenna capable of easily changing the directivity, and to provide a method of changing the directivity.

[0020]

Therefore, according to the present invention, a plurality of antenna elements of an array antenna are divided into a plurality of array groups, and feed points for the antenna elements of each array group are separately set for each array group. The directivity of the array antenna is changed by switching the array group to be set and fed.

Therefore, the directional characteristics of the array antenna can be easily changed.

[0022]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, in an array antenna having a plurality of antenna elements, the antenna elements are divided into a plurality of array groups, and a feeding point for the antenna elements of each array group is provided. Are set separately for each array group, and the directional characteristics can be changed by selecting the array group to which power is supplied.

According to a second aspect of the present invention, one or a plurality of antenna elements are included in the array group, and different directional characteristics can be obtained when each array group is selected. , The number of antenna elements, the element spacing, and the amount of power supplied to each element are set.

According to a third aspect of the present invention, there is provided a switching means for selecting a connection between the power supply point of each array group and the radio, and the directional characteristics can be changed by switching the switching means.

According to a fourth aspect of the present invention, the first aspect of the present invention is applied to an array antenna having a patch antenna element formed on a dielectric substrate.

According to a fifth aspect of the present invention, in the method of varying the directivity characteristics of an array antenna having a plurality of antenna elements, the antenna elements are divided into a plurality of array groups, and the directivity is changed by switching an array group to be fed. The characteristic is changed, and the directional characteristic of the array antenna can be easily changed.

According to a sixth aspect of the present invention, one or a plurality of antenna elements are included in the array group so that different directional characteristics can be obtained when each array group is selected. , The number of antenna elements, the element spacing, and the amount of power supplied to each element are set.

According to a seventh aspect of the present invention, the directivity changing method according to the fifth aspect is applied to an array antenna having a patch antenna element formed on a dielectric substrate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the array antenna of the embodiment has a plurality of patch antenna elements 12 on the surface of a dielectric substrate 11, and these patch antenna elements 12 are denoted by A, B and C are divided into three array groups. The patch antenna elements 12 of each array group are connected by a feeder 14 to a distribution circuit 13 provided one by one in each array group, and the distribution circuit 13 has a feed point 15 provided separately for each array group. Connected to

The power supply point 15 of each array group
Is a changeover switch 23 of the changeover circuit 22, as shown in FIG.
Connected to radio 27 via 24, 25, changeover switch
ON / OFF of 23, 24, 25 is instructed by the switching instructing means 26.

In this array antenna 21, switching instruction means is provided.
When 26 turns on the changeover switch 24 of the changeover circuit 22 and turns off the changeover switches 23 and 25, power is supplied from the radio 27 only to the patch antenna element 12 of the array group B.
The directional characteristics of the array antenna 21 at this time are schematically shown in FIG.
Indicated by 30.

When the switching instruction means 26 turns on the changeover switches 23, 24 and 25 of the changeover circuit 22, the radio 27
, Power is supplied to all the patch antenna elements 12 of the array group A, the array group B and the array group C. The directional characteristics of the array antenna 21 at this time are schematically indicated by 31 in FIG.

As described above, in this array antenna, the directional characteristics of the array antenna can be changed by switching the array group to which power is supplied. Therefore, when different directional characteristics are required, it is possible to respond by switching the array group to which power is supplied without replacing the antenna.

FIG. 4 shows experimental data showing changes in directional characteristics due to switching of antenna elements to be fed. 4A shows the directivity in the vertical direction when power is supplied to four antenna elements, and FIG. 4B shows the directivity in the vertical direction when power is supplied to eight elements. It can be seen that the directivity is improved when power is supplied to eight elements.

The feed line 14 of the array antenna may be connected to the patch antenna element 12 from the back surface of the dielectric substrate 11 through the dielectric substrate 11. Also, feed line 14
May be provided on the back surface of the dielectric substrate 11 to supply power to the patch antenna element 12 by electromagnetic coupling.

Further, the present invention can be applied to array antennas other than antennas in which patch antenna elements are arrayed.

Further, the array antenna of the present invention has an ETC
The present invention can be used not only in systems but also in various fields that require changes in directional characteristics.

[0039]

As is clear from the above description, the array antenna of the present invention can easily change its directional characteristics. Therefore, there is no need to replace the installed antenna in accordance with the directional characteristics.

[Brief description of the drawings]

FIG. 1 is a plan view of an array antenna according to an embodiment of the present invention;

FIG. 2 is a circuit for switching an array antenna according to the embodiment;

FIG. 3 is a diagram showing how the directional characteristics are changed by the array antenna according to the embodiment;

FIG. 4 is experimental data showing a change in directional characteristics of the array antenna according to the embodiment,

FIG. 5 is a diagram showing a conventional patch antenna;

FIG. 6 is a plan view of an array antenna in which patch antenna elements are arrayed.

FIG. 7 is a diagram showing a conventional ETC system;

FIG. 8 is a diagram illustrating an erroneous recognition operation that occurs in a conventional ETC system.

[Explanation of symbols]

 A, B, C Array group 11, 51, 61 Dielectric substrate 12, 52, 62 Patch antenna element 13 Distribution circuit 14, 53, 63 Feeding line 15 Feeding point 22 Switching circuit 23, 24, 25 Switching switch 26 Switching instruction means 27 Radio 91 First vehicle detector 92 Second vehicle detector 93 Array antenna 94 Roadside unit 95 Passing vehicle 96 ETC vehicle

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Morisaki 3-1, Tsunashimahigashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 5J021 AA09 AB06 CA06 DB05 EA01 GA04 JA10

Claims (7)

[Claims] 1. An array antenna having a plurality of antenna elements, wherein the antenna elements are divided into a plurality of array groups, and feed points for the antenna elements of each array group are separately set for each array group. Array antenna. 2. The array antenna according to claim 1, wherein the array group includes one or more antenna elements. 3. The array antenna according to claim 1, further comprising switching means for selecting a connection between a power supply point of each of the array groups and a wireless device. 4. The array antenna according to claim 1, wherein the antenna element comprises a patch antenna element, and the patch antenna element is formed on a dielectric substrate. 5. A method for varying the directional characteristics of an array antenna having a plurality of antenna elements, wherein the directional characteristics are changed by dividing the antenna elements into a plurality of array groups and switching an array group to which power is supplied. Directional characteristics variable method. 6. The method of claim 5, wherein the array group includes one or more antenna elements. 7. The method according to claim 5, wherein the array antenna is an array antenna having a plurality of patch antenna elements formed on a dielectric substrate.