JPH05145319A - On-vehicle non-grounding planar antenna - Google Patents

Abstract

PURPOSE:To install movably an antenna to the prescribed location of a vehicle without needing a hole making process or new installation of a ground plate or the like on a vehicle body by setting a distance between opposite sides of a ground plate to an electric length of lambda/2 so as to form a non-ground flat plate antenna. CONSTITUTION:A distance between opposite sides of a rectangular ground plate 11 is set to an electric length of lambda/2, where lambda is a wavelength of the operating frequency band at the center frequency. Antenna components such as a ground plate 11, a planar antenna element 13 and an exciter 14 or the like of a non-ground planar antenna are housed in a case 17 installed movably freely to the prescribed location of a vehicle. The distance between the power feeding point O of a circular conductor plate 13 and one side of the ground plate 11 is equal to an electric length of lambda/4. Thus, the impedance of the part is infinite, the flowing of an unbalanced current is interrupted to obtain the non-grounding type antenna. Thus, it is not required to make a hole on a vehicle body and provide a special ground connection plate, and the entire case 17 housing the components is freely moved and installed to an optional location on the vehicle body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle non-grounded flat plate antenna suitable as a mobile communication antenna.

[0002]

2. Description of the Related Art In recent years, a flat plate antenna has been attracting attention as a mobile communication antenna. The reason is that when the antenna is attached to the car, the style of the car is not significantly impaired, damage is less likely to occur during car wash or garage insertion, and wind noise during running is less likely to occur. Because it has.

By the way, the conventional flat-plate antenna of this type is required to use a wide ground plate (ideally having an infinite size) as an antenna. Therefore, when the flat plate antenna is used for an automobile, it is attached on the assumption that a part of the vehicle body is used as a ground plate.

That is, the flat antenna is usually attached to, for example, the roof top portion or the trunk lid of an automobile. However, mounting on the outside of the vehicle body will slightly impair the appearance of the vehicle. In addition, it is necessary to perforate the vehicle body. For this reason, recently, it has been attempted to mount a flat antenna inside the vehicle compartment or inside the trunk.

When the flat antenna is mounted inside the passenger compartment or inside the trunk, it is necessary to newly provide a ground connecting plate for grounding the antenna to the vehicle body. As a result, the structure of the vehicle body is complicated, the weight is increased, and the internal space of the vehicle body is narrowed. Therefore, vehicle manufacturers are reluctant to newly install a ground connecting plate inside the vehicle body. Even so, the flat antenna
It is almost unusable to use in the vehicle body without using the ground connecting plate because the characteristics are significantly deteriorated.

[0006]

As described above, since the conventional flat plate antenna is a so-called grounded antenna, it is necessary to use a part of the vehicle body as a ground plate when used for an automobile. However, there is a drawback that it requires a lot of work to make holes in the vehicle body and a new grounding connecting plate is required. Also, since it is a grounded antenna, the radiation pattern in the vertical plane is upward. Therefore, the gain in the horizontal direction is 0
-6 dBd, the gain changes drastically with respect to the elevation angle,
Transmission and reception characteristics were unstable.

The object of the present invention is that there is no need to make holes in the vehicle body, new installation of the ground connection plate, etc., and there is no fear of an increase in vehicle body weight or a decrease in vehicle body strength. It is an object of the present invention to provide an ungrounded flat plate antenna for a vehicle, which can be freely moved and installed at a location, has a stable radiation pattern in terms of characteristics, and can be expected to perform good transmission and reception.

[0008]

In order to solve the above problems and achieve the object, the following measures were taken in the present invention.

The ground plane, the flat antenna element supported in parallel by a plurality of ground pins on the ground plane, and the central portion of the flat antenna element are opposed to each other so that a capacitor electrode provided in the central portion is electrostatically coupled. An exciter, which is arranged and has a predetermined inter-ground plate capacitance and a line length so as to resonate at a predetermined frequency, and a feeder line having one end connected to a predetermined position of the exciter. ..

With respect to the main plate, when the wavelength at the center frequency of the used frequency band is λ, the distance between the opposite sides is set to the electrical length λ / 2, and the square or the diameter is set to the electrical length λ / 2. It is formed to have a round shape.

The flat plate-shaped antenna is mounted on a main plate inside a case provided so as to be movable and installed at a predetermined position of the vehicle.
It is preferable that the antenna constituent elements such as a flat plate antenna element and an exciter are housed, and the feeder line is led out from the case.

[0012]

As a result of taking the above measures, the following effects occur. Since the flat antenna is a non-ground type, it is not necessary to use a part of the vehicle body as a ground plate. As a result, there is no need to perforate the vehicle body or to provide a special ground connecting plate, and there is no risk of increasing the weight of the vehicle body or reducing the vehicle body strength. Then, it becomes possible to freely move and set it to an arbitrary place in the vehicle body, such as a rear tray or a dashboard. Further, since it is a non-grounded type, the vertical in-plane radiation pattern is an 8-shaped radiation pattern along the horizontal line of the same shape as the dipole antenna, and the gain variation with respect to the elevation angle is small, and a stable radiation pattern is exhibited. Therefore, good transmission and reception can be expected.

[0013]

FIG. 1 is a diagram showing a vehicle non-grounded flat plate antenna 10 according to an embodiment of the present invention. FIG. 1 (a) is a perspective view schematically showing the structure of a main part, and FIG. The side surface sectional view which shows the whole structure of the non-grounded planar antenna 10, (c) is a figure which shows the connection part to the non-grounded planar antenna 10 of the feeder 16 which consists of a coaxial cable, and C part of (b). It is the figure which expanded and showed.

In FIG. 1, reference numeral 11 is a base plate made of a rectangular conductive plate, and a plurality of (four in this embodiment) ground pins 12 are provided on the base plate 11 to form a flat antenna element made of a circular conductive plate. 13 are supported in parallel.
The radius R of the circular conductive plate forming the flat plate antenna element 13, the distance r from the center O of the circular conductive plate to each ground pin 12, the thickness d of each ground pin 12, the height H of each ground pin 12, etc. Dimensions of each part are flat antenna element 1
When the power is fed from the central part of 3, the antenna element 13 resonates at a predetermined frequency, and the impedance at resonance is
It is set to a value necessary to obtain the required band.

Reference numeral 14 is an exciter composed of a strip line. The exciter 14 has a capacitor electrode 15 at the center thereof that is electrostatically coupled to the central portion of the flat plate antenna element 13, and both ends thereof are connected to the ground plate 11. The exciter 14 has a predetermined inter-ground plate capacitance and a line length L so as to resonate at a predetermined frequency. One end of a feed line 16 made of a coaxial cable is connected to a predetermined position (best matching point position) near the right end of the exciter 14 in the figure. In the rectangular base plate 11, the distance between the opposite sides is set to an electrical length λ / 2, where λ is the wavelength at the center frequency of the used frequency band.

The non-grounded flat plate antenna 10 is shown in FIG.
As shown in (b) of FIG. 3, antenna components such as the main plate 11, the flat plate-shaped antenna element 13, and the exciter 14 are housed inside a case 17 provided so as to be movably installed at a predetermined location of the vehicle, and The power supply line 16 is provided so as to be led out from the case 17 to the outside.

In the antenna of this embodiment, since the distance between the opposite sides of the main plate 11 is set to the electrical length λ / 2, the distance from the feeding point (center O of the circular conductive plate) to one side of the main plate 11 is large. Is an electrical length of λ / 4. Therefore, the impedance of this portion becomes infinite and the flow of unbalanced current is blocked. That is, a non-grounded antenna is realized. Thus, it is not necessary to use a part of the vehicle body as a ground plate as in the conventional case. As a result, it is not necessary to perforate the vehicle body or provide a special ground connecting plate. Therefore, there is no possibility of increasing the weight of the vehicle body or reducing the vehicle body strength. And with case 17,
It is possible to freely move and set it to any place in the vehicle body, such as a rear tray or a dashboard.
On the other hand, since it is a non-grounded antenna, the vertical in-plane radiation pattern exhibits a stable figure-eight radiation pattern.

2 (a) and 2 (b) are diagrams showing the vertical in-plane radiation pattern of the non-grounded flat plate-shaped antenna 10 of this embodiment in comparison with the vertical in-plane radiation pattern of the conventional antenna. is there. As shown in (a), the vertical in-plane radiation pattern of the non-grounded flat plate-shaped antenna 10 of this embodiment is an 8-shaped radiation pattern along the horizontal line of the same shape as the dipole antenna. As a result, the gain in the horizontal direction is 0 to -1 dBd.
Becomes It shows a stable gain curve with little change in elevation angle. Therefore, good transmission and reception can be expected. On the other hand, the conventional antenna is upward at an elevation angle of about 30 ° as shown in (b), and the gain in the horizontal direction is about 0 to -6 dBd, which is an unstable gain curve as shown in the figure. Is becoming

3 (a) and 3 (b) are diagrams showing the VSWR characteristics of the antenna of this embodiment, FIG. 3 (a) is a diagram showing the results of actual measurement of the antenna 10, and FIG. It is a figure which shows the result of having measured 11 in the state which brought close to the grounding board which has a large area, such as a vehicle body wall. Figure 2 (a)
As is clear from the comparison of (b), the antenna of the present embodiment shows a slight change in impedance even if it is brought close to a ground plate having a large area, and practically causes no trouble. .. Although not shown, it was observed that the vertical in-plane radiation pattern was directed upward as it approached a large-area ground plate.

The present invention is not limited to the above embodiment. For example, although the quadrangular base plate 11 is shown in the above embodiment, a circular base plate may be used. When a circular ground plane is used, a non-grounded antenna can be obtained by setting its diameter to λ / 2. Of course, various modifications can be made without departing from the scope of the present invention.

[0021]

According to the present invention, since a so-called non-grounded flat plate antenna is realized and adopted, it is not necessary to make a hole in the vehicle body or newly install a grounding plate, thereby increasing vehicle body weight and vehicle body strength. Of course, it can be freely moved and installed at any place in the vehicle body, and has a stable radiation pattern in terms of characteristics, and good transmission / reception can be expected for vehicles. It is possible to provide a grounded flat plate antenna.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a vehicle non-grounded flat plate antenna according to an embodiment of the present invention.

FIG. 2 is a diagram showing a vertical in-plane radiation pattern of a vehicle non-grounded flat plate-shaped antenna according to the above embodiment in comparison with a vertical in-plane radiation pattern of a conventional antenna.

FIG. 3 is a diagram showing a VSWR characteristic of the non-grounded flat plate antenna for a vehicle according to the above embodiment.

[Explanation of Codes] 10 ... Non-grounded flat plate antenna for vehicle, 11 ... Ground plate, 1
2 ... Ground pin, 13 ... Flat plate antenna element, 14 ... Exciter consisting of strip line, 15 ... Capacitor electrode,
16 ... A power supply line composed of a coaxial cable, 17 ... a case.

Claims (2)

[Claims] 1. A ground plane, a plate-shaped antenna element supported in parallel by a plurality of ground pins on the ground plane, and a capacitor electrode provided in the central portion of the flat plate-shaped antenna element is electrostatically coupled to the central portion. An exciter, which is arranged so as to face each other and has a predetermined inter-ground plane capacitance and a line length so as to resonate at a predetermined frequency, and a power supply line whose one end is connected to a predetermined position of the exciter, The ground plate has a square or a square having a distance between the opposite sides set to an electrical length of λ / 2 or a diameter set to an electrical length of λ / 2, where λ is a wavelength at a center frequency of a used frequency band. An ungrounded flat plate antenna for a vehicle, which is formed in a circular shape. 2. A ground plane, a flat plate antenna element, and a case provided inside a case provided so as to be movable and installed at a predetermined location of a vehicle.
The non-grounded flat plate antenna for a vehicle according to claim 1, wherein an antenna constituent element such as an exciter is housed and a feeder line is led out from the case.