JP3242131B2 - Directional planar antenna for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional flat plate antenna for a vehicle, which is suitable as a mobile communication antenna.

[0002]

2. Description of the Related Art In recent years, a flat antenna has been receiving attention as an antenna for mobile communication. The reason is that when the antenna is mounted on the car, the style of the car does not have to be significantly impaired, it is difficult for damage to occur when washing or entering the garage, wind noise during running is unlikely to occur, This is because it has an advantage that it can be mounted inside the vehicle body in response. Generally, this type of flat antenna is configured such that the radiation pattern in the horizontal plane is non-directional. That is, usually, a circular table-shaped antenna element is used as the planar antenna element, and the ground pin supporting the planar antenna element is point-symmetric with respect to the center of the circular table-shaped planar antenna element. And the current flowing on the outer periphery of the flat antenna element is configured to have a constant distribution.

[0003] On the other hand, in recent mobile communication systems, adoption of a diversity reception system is being studied and promoted along with digitization of communication information. In the diversity receiving method, for example, a sub-antenna is mounted at a predetermined distance in addition to the main antenna in order to eliminate characteristic deterioration caused by so-called fading, and a so-called diversity effect (effect of removing adverse effects due to fading) is provided by these two antennas. )
It is a method that gives out.

In order to realize a diversity receiving type antenna device mounted inside a vehicle body using a flat antenna as at least one antenna, the flat antenna and other antennas (flat antenna, rod antenna, etc.) have been developed. And inside the dashboard near the driver's seat of the vehicle,
Considering that the antenna is mounted on the rear tray at the rear of the vehicle or between the inside of the trunk and the like, it is necessary to provide the flat antenna with a predetermined directivity. That is, if an omnidirectional flat plate antenna is attached to such a location, radio waves radiated toward the inside of the vehicle body are attenuated, resulting in a reduction in overall radiation efficiency.
Therefore, in the flat antenna used in the above-described embodiment, at least the radiation pattern in the horizontal plane is directional, which is a necessary condition for increasing the overall radiation efficiency.

[0005]

As described above, the conventional flat antenna is an omnidirectional antenna. Therefore, for example, in order to realize an antenna device mounted inside a vehicle body, which is compatible with a diversity receiving system, the flat antenna is used. When the antenna is installed inside the dashboard near the driver's seat of the vehicle, on the rear tray at the rear of the vehicle, inside the trunk, etc., the radio wave radiated to the inside of the vehicle body is attenuated, reducing the overall radiation efficiency. was there.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiation pattern in a horizontal plane which is directional, minimizes radio waves radiated toward the inside of the vehicle body, and achieves efficient transmission and reception without lowering the overall radiation efficiency. on expected, antenna directivity orientation, bi-
It is possible to easily adjust and set the beam width etc. to the desired state according to the surrounding situation, and it is possible to move and install it at any place in the vehicle body in the required state, and to achieve stable and good transmission and reception It is therefore an object of the present invention to provide a directional plate antenna for a vehicle which is extremely preferable for realizing an antenna device mounted inside a vehicle body which is compatible with a diversity receiving system.

[0007]

Means for Solving the Problems In order to solve the above problems and achieve the object, the present invention has taken the following measures.

A ground plate, a plate-like antenna element supported in parallel by a plurality of ground pins on the ground plate, and a capacitor electrode provided at the center of the plate-like antenna element so as to be electrostatically coupled to the center of the plate-like antenna element An exciter comprising a strip line having a predetermined inter-base-plate capacitance and a line length so as to resonate at a predetermined frequency is provided, and a feeder line having one end connected to a predetermined position of the exciter. .
At least one of the ground pin and the flat antenna element is provided in a non-point-symmetric state with the feeding point of the flat antenna element as a center of symmetry.

The ground pins are arranged such that the number of ground pins located at the other end of the planar antenna element is larger than the number of ground pins located at one end of the planar antenna element. Is preferably provided such that directivity having a beam width corresponding to the ratio of the number of ground pins located at the other end to the number of ground pins located at the other end is generated at the one end.

When the wavelength at the center frequency of the used frequency band is λ, the ground plane is a square in which the distance between the opposite sides is set to the electric length λ / 2, or the diameter is the electric length λ.
It is preferably formed so as to form a circle set to / 2.

[0011]

The following effects are obtained as a result of taking the above measures. First, since the flat antenna is directional, if this flat antenna is mounted on the vehicle body, if the direction of the directivity is mounted toward the outside of the vehicle body, radio waves radiated toward the inside of the vehicle body will be minimized. Can be suppressed. As a result, it is possible to expect efficient transmission and reception without a decrease in overall radiation efficiency.

Also, since the antenna is configured to have directivity by the arrangement of the ground pins, the azimuth of the directivity, the beam width, etc. can be easily adjusted and set to a required state according to the surrounding situation only by changing the arrangement of the ground pins. it can.

Further, since the directional plate antenna can be a non-grounded antenna, it is not necessary to use a part of the vehicle body as a ground plate. As a result, there is no need to perform perforation processing on the vehicle body or provide a special grounding connection plate, and the vehicle body can be freely moved and installed at any point in the vehicle body, such as a rear tray or a dashboard. It becomes possible. Further, since the antenna is of the non-ground type, the vertical plane radiation pattern becomes an 8-shaped radiation pattern along a horizontal line having the same shape as that of the dipole antenna, and the gain variation with respect to the elevation angle is small, and a stable radiation pattern is exhibited. Therefore, stable and good transmission and reception can be performed.

Thus, a very useful flat antenna can be obtained, for example, when the flat antenna is mounted at a predetermined position inside the vehicle body in order to realize an antenna device mounted inside the vehicle body which is compatible with the diversity receiving method.

[0015]

FIG. 1 is a view showing a directional plate antenna 10 for a vehicle according to an embodiment of the present invention. FIG. 1A shows a configuration of a main part of a non-grounded directional plate antenna 10. Is a plan view showing a case portion by a virtual line (two-dot chain line), (b) is a side view showing the entire configuration of the same antenna 10 and a case portion is also shown by a virtual line (two-dot chain line), and (c) is a coaxial line. It is a figure which shows the connection part of the feeder line 16 which consists of a cable to the same antenna 10, and is the figure which expanded and showed C part of (b).

In FIG. 1, reference numeral 11 denotes a ground plate made of a substantially square conductive plate whose periphery is slightly rounded. This ground plate 1
A flat antenna element 13 made of a substantially rectangular conductive plate is supported in parallel on one by a plurality (three in this embodiment) of ground pins 12 (12a to 12c).
The distance from the center O of the conductive plate constituting the flat antenna element 13 to each of the ground pins 12a, 12b, 12c, the thickness of each of the ground pins 12a, 12b, 12c, and the height of each of the ground pins 12a, 12b, 12c. When the power is supplied from the central portion O of the planar antenna element 13, the dimensions of each part such as the antenna element 13 resonate at a predetermined frequency, and the impedance at the resonance becomes a value necessary for obtaining a required band. It is set as follows.

Reference numeral 14 denotes an exciter formed of a strip line. The exciter 14 has a capacitor electrode 15 at the center thereof, which is electrostatically coupled to the center of the flat antenna element 13, and legs at both ends are connected to the ground plane 11. The exciter 14 has a predetermined capacitance between the ground planes and a line length so as to resonate at a predetermined frequency. A feed line 16 made of a coaxial cable is provided at a predetermined position (best matching point position) near the right end of the exciter 14 in the drawing.
Are connected at one end.

The above-described substantially square base plate 11 having a slightly rounded periphery has a distance between opposite sides in electrical length of λ / λ, where λ is the wavelength at the center frequency of the used frequency band.
It is set to 2.

The ground pins 12a, 12b,
Numeral 12c is provided at a non-point-symmetric state, that is, at each vertex of an equilateral triangle in this embodiment, with the feeding point (center O) of the flat antenna element 13 as the "center of symmetry".
The ground pins 12a, 12b, and 12c are connected to one end (the upper end in FIG. 1A) of the flat antenna element 13 with respect to the number "1" of the ground pins 12c. Ground pins 12a located at the ends (lower ends in FIG.
The number of 12b is “2”. That is, the number of ground pins 12a and 12b located at the other end is smaller than the number of ground pins 12c located at one end of the planar antenna element 13.
Are arranged in such a way that the number is larger. Thus, as shown by the arrow D, on one end side of the plate-shaped antenna element 13, a directivity having a beam width corresponding to the ratio between the number of earth pins on the one end side and the number of earth pins on the other end side is obtained. Is provided.

The planar antenna 10 accommodates antenna components such as a ground plane 11, a planar antenna element 13, and an exciter 14 in a case 17 which is movably provided at a predetermined location in a vehicle. In addition, the power supply line 16 is provided so as to extend to the outside from the case 17.

In the flat antenna 10 according to the present embodiment having the above-described configuration, the ground pins 12a, 12b, and 12c are
The feeding point (central portion O) of the flat antenna element 13 is provided as a “center of symmetry” and is not point-symmetric. In the case of this embodiment, one ground pin 12c is provided at one end of the flat antenna element 13, and two ground pins 1c are provided at the other end of the flat antenna element 13.
2a and 12b are provided. Therefore, the flat antenna 10 has directivity in the direction indicated by the arrow D on the one end side. In this case, the number of ground pins 12c located at one end is "1", while the number of ground pins 12a and 12b located at the other end is "2". This results in a directivity having an increased beam width .

FIGS. 2A, 2B, and 2C show the radiation pattern in (b) of the ungrounded / horizontal plane and the radiation pattern of (c) in the ungrounded / vertical plane with respect to the arrangement state of the ground pins in (a). It is a figure showing a change situation of a pattern. As shown in [1] of FIG. 2A, when the four ground pins 12 are arranged point-symmetrically, the radiation pattern in the horizontal plane and the radiation pattern in the vertical plane are as shown in FIG. As shown in [1] of FIG. 2 and [1] of FIG. Further, as shown in [2] and [3] of FIG. 2A, when the plurality of ground pins 12 are not arranged point-symmetrically, the ground pins 12 of FIG. [2]
As shown in [3] and [2] and [3] of FIG. 2C, the radiation pattern in the horizontal plane and the radiation pattern in the vertical plane have directivity, respectively. As is clear from the comparison between [2] and [3] in FIGS. 2B and 2C, the number of ground pins 12 located at one end (the right end in the drawing) is reduced to “1”. On the other hand, the number of the ground pins 12 located on the other end side (the left end side in the figure) is “2”.
As the number increases from "3" to "3", that is, as the ratio of the number of the ground pins 12 increases, the radiation pattern gradually narrows the beam width and increases the directivity.

FIGS. 3 (a) and 3 (b) show two directional plate antennas 1 having the above-described configuration in order to realize an antenna device mounted inside a vehicle body which is compatible with the diversity receiving system.
It is a figure which shows (a) the radiation pattern in a horizontal plane, and (b) the radiation pattern in a vertical plane when 0A and 10B are each mounted to the dashboard and rear tray of the vehicle body 20. In this case, the flat antenna 10A is mounted with the directivity direction facing the front of the vehicle, and the flat antenna 10B is mounted with the directivity direction facing rear of the car.

Therefore, as indicated by the two-dot chain line in FIG. 1, the radio waves are mainly radiated to the outside of the vehicle body, and the radio waves radiated to the inside of the vehicle body are minimized. As a result, a decrease in overall radiation efficiency is suppressed, and efficient transmission and reception can be performed.

In the case of this embodiment, the directivity can be set to a required state by changing the arrangement of the ground pins 12. Therefore, it is possible to adjust and set the directionality, beam width, and the like of the directivity to a desired state according to the situation around the antenna.

On the other hand, the flat antenna 10 of the present embodiment
Since the distance between the opposite sides of the base plate 11 is set to the electrical length λ / 2, the base plate 1 is viewed from the feeding point (the center O of the conductive plate).
The distance to one side is λ / 4 in electrical length. Therefore, the impedance of this portion becomes infinite, and the flow of the unbalanced current is prevented. That is, a non-grounded directional flat plate antenna is realized. Thus, it is not necessary to use a part of the vehicle body 20 as a ground plate as in the related art. As a result, there is no need to make a hole in the vehicle body 20 or to provide a special ground connection plate. Therefore, there is no possibility of increasing the weight of the vehicle body or reducing the strength of the vehicle body. Then, it is possible to freely move and install the entire case 17 at an arbitrary place in the vehicle body, for example, a rear tray or a dashboard. Since the antenna is a non-grounded antenna, the radiation pattern in the vertical plane is as shown in FIG.
As shown in FIG. 5, a stable radiation pattern having a figure eight shape is exhibited. Therefore, stable and good transmission and reception can be expected.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the directivity is given to the antenna 10 by the arrangement of the ground pins 12 is exemplified. However, the special directivity may be given by changing the shape of the flat antenna element 13. Good. For example, a modification may be made such that one side of a substantially quadrangular member is protruded in a triangular shape so as to have a bimodal directivity. Of course, the combination of the shape of the flat antenna element 13 and the arrangement of the ground pins allows the antenna 1
0 may have a desired directivity. Further, in the above-described embodiment, the substantially square ground plate 11 is shown as the ground plate, but a circular ground plate may be used. When a circular ground plate is used, an ungrounded antenna can be obtained by setting the diameter to λ / 2. In addition, it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0028]

According to the present invention, the following effects can be obtained.

First, at least one of the ground pin and the flat antenna element is provided in a non-point-symmetric state with respect to the feeding point of the flat antenna element as a center of symmetry, so that the radiation pattern in the horizontal plane is directional. Thus, radio waves radiated toward the inside of the vehicle body can be suppressed to a minimum, and efficient transmission and reception can be expected without a decrease in overall radiation efficiency.

Further, the number of ground pins located at the other end of the flat antenna element is arranged to be larger than the number of ground pins located at one end of the flat antenna element, and the ground pin is directed toward the one end. Therefore, only by changing the pin arrangement, it is possible to easily adjust and set the directionality, beam width, and the like of the directivity of the antenna to a required state according to the surrounding situation.

Further, since the distance between the opposite sides of the substantially square ground plate or the diameter of the circular ground plate is set to λ / 2 in electrical length, a non-grounded directional flat plate antenna can be realized. Thus, it is no longer necessary to use a part of the vehicle body as a ground plate as in the conventional case, and it is possible to move and install the vehicle at an arbitrary place in the vehicle body in a required manner, and in addition, a stable vertical radiation pattern can be obtained. Stable and good transmission and reception.

Thus, it is possible to provide a directional plate antenna for a vehicle which is extremely preferable for realizing an antenna device mounted inside a vehicle body which is compatible with, for example, a diversity reception system .

[Brief description of the drawings]

FIG. 1 is a diagram showing a directional plate antenna for a vehicle according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change state of a non-grounded / horizontal plane radiation pattern and a non-grounded / vertical plane radiation pattern with respect to a ground pin arrangement state of the directional plate antenna for a vehicle according to the embodiment.

FIG. 3 is a diagram showing a radiation pattern in a horizontal plane and a radiation pattern in a vertical plane when the directional plate antenna for a vehicle according to the embodiment is mounted on a dashboard and a rear tray of a vehicle body, respectively.

[Explanation of symbols]

10: directional plate antenna for vehicle, 11: ground plane, 1
2 (12a, 12b, 12c): ground pin, 13: flat antenna element, 14: exciter composed of strip line, 15: capacitor electrode, 16: feed line composed of coaxial cable, 17: case.

Continuation of the front page (56) References JP-A-2-308604 (JP, A) JP-A-1-272303 (JP, A) IEICE Transactions B, Vol. J71-B, No. 11, 1988, pp. 1281 -1286 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 13/08 H01Q 1/32

Claims (3)

(57) [Claims] 1. A ground plate, a planar antenna element supported in parallel by a plurality of ground pins on the ground plate, and a capacitor electrode provided at a central portion with respect to a central portion of the planar antenna element are electrostatically coupled. An exciter composed of a strip line having a predetermined inter-ground plate capacitance and a line length so as to be opposed to each other and resonate at a predetermined frequency as described above, and a feeder line having one end connected to a predetermined position of the exciter, Wherein at least one of the ground pin and the flat antenna element is provided in a non-point-symmetric state with respect to a feed point of the flat antenna element as a center of symmetry. Flat antenna. The ground pins are arranged such that the number of ground pins located at the other end of the flat antenna element is larger than the number of ground pins located at one end of the flat antenna element. The directivity having a beam width corresponding to a ratio of the number of ground pins located at one end to the number of ground pins located at the other end is provided so as to be generated at the one end side. 2. The directional plate antenna for vehicles according to 1. 3. A base plate having a square or a diameter having an electrical length of λ / 2 where a distance between opposite sides is set to an electrical length of λ / 2, where λ is a wavelength at a center frequency of a used frequency band.
The directional plate antenna for a vehicle according to claim 1, wherein the antenna is formed so as to have a circular shape set as follows.