JP2004214863A - Antenna system and communication terminal equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna system which controls a radiation pattern within a perpendicular plane even in a low elevating angle direction, a radiation pattern within a horizontal plane, and also a radiation pattern within the vertical plane at the same time, and also to provide communication terminal equipment provided with the antenna system. <P>SOLUTION: The antenna system is provided with a plate ground conductor 2, a radiation element as an antenna element placed nearly vertically to the plate ground conductor 2 and parasitic conductors 3a, 3b tilted from an outer circumferential edge of the ground conductor 2 to a side of the ground conductor 2 opposite to the side of the ground conductor 2 to which the radiation element 1 is provided, and switch elements 4a, 4b are respectively mounted between the ground conductor 2 and the parasitic conductor 3a and between the parasitic conductors 3a, 3b. Switching the switch elements 4a, 4b controls the radiation pattern within the vertical plane. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an antenna device used in a mobile communication system and the like and a communication terminal device including the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a monopole antenna having a finite ground conductor is provided in, for example, a communication terminal device in a mobile communication system. FIG. 7 shows an example of the configuration. In FIG. 7, the ground conductor 2 has a disk shape, and a radiating element 1 extending in a direction perpendicular to the ground conductor 2 is provided at the center thereof.
[0003]
In a monopole antenna having such a ground conductor, if the ground conductor has an infinite size, the gain in the vertical plane is maximum in the horizontal direction, but the ground conductor is actually finite, Due to the edge effect, the radiation pattern in the vertical plane is upward from the horizontal. The elevation angle at which the maximum gain of the radiation pattern is obtained depends on the size and structure of the ground conductor.
[0004]
In an antenna device used for a wireless LAN or the like, not only a radiation pattern in a horizontal plane but also a radiation pattern in a vertical plane is generally important in securing a predetermined communication quality. Patent Document 1 discloses an antenna device that controls a radiation pattern in a vertical plane. Patent Document 2 discloses that the elevation angle of the maximum gain in the vertical plane is reduced to improve the gain in the horizontal plane.
On the other hand, as a device for controlling a radiation pattern in a horizontal plane, a radiation element is provided in a direction perpendicular to a ground conductor plate, and an electronically controlled waveguide array (ESPAR) in which a plurality of waveguide elements are arranged around the radiation element. An antenna is disclosed in Patent Document 3.
[0005]
[Patent Document 1]
JP-A-2001-53530
[Patent Document 2]
JP-A-2002-16427
[Patent Document 3]
JP 2001-24431A
[0006]
[Problems to be solved by the invention]
However, in the antenna device having the structure disclosed in Patent Document 1, when the monopole antenna is excited at different frequencies using the same ground conductor, the elevation angle at which the maximum gain in the vertical plane is obtained according to each frequency is increased. In order to solve the problem of change, the size of the ground conductor extending on the plane is merely electrically switched. Therefore, even if the area of the grounding conductor is increased to a certain extent or more, there is a problem that the radiation pattern in the vertical plane cannot be largely changed to a low elevation angle. Further, in the conventional ESPAR antenna disclosed in Patent Document 3, the gain in the vertical plane cannot be controlled.
[0007]
An object of the present invention is to provide an antenna device capable of controlling a radiation pattern in a vertical plane even in a lower elevation angle direction and a communication terminal device including the same.
It is another object of the present invention to provide an antenna device capable of controlling a radiation pattern in a horizontal plane and simultaneously controlling a radiation pattern in a vertical plane, and a communication terminal device including the antenna device.
[0008]
[Means for Solving the Problems]
An antenna device according to the present invention includes a plate-like ground conductor, an antenna element disposed substantially perpendicular to the plate-like ground conductor, and a side opposite to a side where the antenna element is provided from an outer peripheral edge of the plate-like ground conductor. A parasitic conductor inclined to the side, a variable impedance circuit for changing impedance between the plate-shaped ground conductor and the parasitic conductor, and a unit for controlling the variable impedance circuit.
[0009]
As described above, since the normal direction of the parasitic conductor inclined to the opposite side from the side where the antenna element is provided is directed to the low elevation angle direction, by connecting this parasitic conductor, the radiation pattern in the vertical plane is reduced. It can be directed to a lower elevation angle direction. Then, by changing the impedance of the variable impedance circuit provided between the parasitic conductor and the outer peripheral edge of the plate-like ground conductor, it becomes possible to control the radiation pattern in the vertical plane in a lower elevation angle direction.
[0010]
Further, the antenna device according to the present invention is configured such that the antenna element includes at least one radiator and at least one parasitic element disposed around the radiator, and that the effective element length of the parasitic element is set to an electric value. It is characterized in that control means for changing the temperature is provided. With this structure, the pattern in the horizontal plane can be controlled together by the radiating element and the parasitic element.
[0011]
Further, in the antenna device of the present invention, the parasitic conductor is a cylindrical conductor provided along an outer peripheral edge of the plate-like ground conductor. With this structure, the formation of the parasitic conductor is facilitated, and the maximum gain direction of the radiation pattern in the vertical plane can be effectively directed to a lower elevation angle (horizontal direction).
[0012]
Further, the antenna device of the present invention is characterized in that the plate-like ground conductor is made substantially circular. As a result, the radiation pattern in the horizontal plane can be made rotationally symmetric, and the elevation angle of the maximum gain in the vertical plane can be reduced in all directions.
[0013]
The antenna device according to the present invention may further include an antenna element including a radiating element and at least one parasitic element disposed around the radiating element, provided on the plate-shaped ground conductor, causing the parasitic conductor to be adjacent to the plate-shaped ground conductor, and It is characterized in that it is provided on substantially the same plane as the conductor. With this structure, creation of a parasitic conductor and mounting of an impedance circuit can be facilitated.
[0014]
Further, the antenna device according to the present invention is characterized in that the variable impedance circuit is configured by a MEMS element that controls a switch between electrodes by a control voltage. This facilitates miniaturization of the variable impedance circuit mounting portion and application to the millimeter wave band region and the submillimeter wave band region.
[0015]
Further, a communication terminal device according to the present invention is characterized by comprising an antenna device having any one of the above configurations and a communication means for transmitting / receiving a signal for a wireless LAN using the antenna device.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
An antenna device according to a first embodiment will be described with reference to FIGS.
FIG. 1A is an external perspective view of the antenna device. Here, 2 is a disk-shaped ground conductor. At the center of the ground conductor 2, a radiating element 1 extending in a direction perpendicular to the ground conductor 2 is provided. A cylindrical parasitic conductor 3 a is provided along the outer peripheral edge of the ground conductor 2. Further, another cylindrical parasitic conductor 3b is arranged along the lower peripheral edge of the parasitic conductor 3a. In this example, the inclination angle of the parasitic conductor 3 with respect to the ground conductor 2 is set to 90 °. A switching element 4a is mounted between the ground conductor 2 and the parasitic conductor 3a, and a switching element 4b is mounted between the parasitic conductors 3a and 3b. The switch elements 4a and 4b constitute an impedance circuit.
[0017]
FIG. 1B shows this antenna device as a circuit diagram. A feeding circuit 5 for the radiating element 1 and a control circuit 6 for the switching elements 4a and 4b are provided inside the cylindrical shape formed by the parasitic conductors 3a and 3b. The switches 4a and 4b are composed of MEMS (Micro Electro Mechanical Systems) elements, and switch between the electrodes by applying a control voltage. The control circuit 6 supplies a control voltage to these switch elements 4a and 4b. When the switching elements 4a and 4b are turned on, the impedance at both ends becomes very small.
[0018]
FIG. 2 shows an example of a radiation pattern in a vertical plane of the antenna device shown in FIG. Here, P1 is a radiation pattern when both the switch elements 4a and 4b are turned off, that is, when only the ground conductor 2 acts as an original ground conductor.
P2 is a radiation pattern when the switching element 4a is turned on and the switching element 4b is turned off, and the parasitic conductor 3a acts as a conductor extending from the ground conductor 2. P3 is a radiation pattern when the switch elements 4a and 4b are both turned on and the parasitic conductors 3a and 3b act as ground conductors extending from the ground conductor 2. Further, θ1 indicates the elevation angle at which the maximum gain of the radiation pattern P1 is obtained, θ2 indicates the elevation angle at which the maximum gain of the radiation pattern P2 is obtained, and θ3 indicates the elevation angle at which the maximum gain of the radiation pattern P3 is obtained. As described above, the elevation angle of the maximum gain decreases from θ1 to θ2 by operating the parasitic conductor 3a as the ground conductor, and the elevation angle of the maximum gain decreases to θ3 by operating the parasitic conductor 3b as the ground conductor. be able to. In the example shown in FIG. 1, the switch elements 4a and 4b are arranged in a symmetrical positional relationship with respect to the center of the ground conductor 2 between the ground conductor 2 and the parasitic conductor 3a and between the parasitic conductors 3a and 3b. Is mounted, but three or more switch elements may be mounted at equal angular intervals or non-equiangular intervals. Further, a single switch element may be mounted.
[0019]
In the example shown in FIG. 1, the double parasitic conductors 3a and 3b are provided so that the radiation pattern in the vertical plane can be switched in two stages. However, the radiation pattern in the vertical plane can be switched in one stage. If appropriate, only the parasitic conductor 3a may be used.
[0020]
FIG. 3 is a perspective view illustrating the configuration of the antenna device according to the second embodiment. In FIG. 3, reference numeral 2 denotes a disc-shaped grounding conductor, and 1 denotes a radiating element which extends in the center of the grounding conductor 2 in a direction perpendicular to the grounding conductor 2. A parasitic conductor 3 is provided which is inclined from the outer peripheral edge of the ground conductor 2 to the side opposite to the side on which the radiation element 1 is provided. A switch element 4 that is electrically intermittent is mounted between the parasitic conductor 3 and the ground conductor 2. As described above, even if the inclination angle of the parasitic conductor 3 with respect to the ground conductor 2 is not 90 °, if the parasitic conductor 3 is inclined on the side opposite to the side on which the radiating element 1 is provided, the switch element 4 is turned on. When the parasitic conductor 3 acts as a ground conductor continuous from the parasitic conductor 2, the maximum gain of the radiation pattern in the vertical plane can be reduced to a low elevation angle.
[0021]
Next, the configuration of the antenna device according to the third embodiment will be described with reference to FIG.
In the example shown in FIG. 4A, a radiating element 11 and parasitic elements 12a to 12f extending in a direction perpendicular to the disc-shaped ground conductor 2 are provided. A feeding circuit is provided at the lower end of the radiating element 11. Variable reactance circuits are provided at lower ends of the parasitic elements 12a to 12f. By controlling these variable reactance circuits, the equivalent electrical lengths of the parasitic elements 12a to 12f change, and selectively act as a director or a reflector. This constitutes an electronically controlled director array (ESPAR) antenna. For example, if the parasitic element 12d acts as a reflector and the parasitic element 12a acts as a director, the center of the radiation pattern in the horizontal plane is directed from the radiating element 11 to the parasitic element 12a. The relationship between the parasitic conductor 3 and the switch element 4 with respect to the ground conductor 2 is the same as in the first embodiment.
[0022]
In FIG. 4A, a single parasitic conductor 3 is provided as a parasitic conductor, and in the example of FIG. 4B, two parasitic conductors 3a and 3b are provided as in the case of the first embodiment. .
By selectively controlling these parasitic conductors 3 or 3a, 3b as ground conductors by controlling the switch elements 4, 4a, 4b, the radiation pattern in the vertical plane can be controlled at the same time.
[0023]
In the example shown in FIG. 4, a plurality of parasitic elements 12a to 12f are provided, but at least one parasitic element is provided, and the radiation pattern in the horizontal plane is controlled by controlling the electrical length of the parasitic element. You may make it.
[0024]
FIG. 5 is a perspective view showing the configuration of the antenna device according to the fourth embodiment. In this example, the parasitic conductor 3 is disposed on the same plane as the ground conductor 2 on the outer periphery of the disk-shaped ground conductor 2, and the switch element 4 is mounted between the ground conductor 2 and the parasitic conductor 3. The radiating element 11 and the parasitic elements 12a to 12f are arranged on the ground conductor 2. The configuration of the ground conductor 2, the radiating element 11, and the parasitic elements 12a to 12f is the same as that of the antenna device shown in FIG. In this example, since the parasitic conductor 3 is on the same plane as the ground conductor 2, its manufacture and mounting of the switch element 4 are easy, and the overall cost can be reduced.
[0025]
Next, a configuration of a communication terminal device according to the fifth embodiment is shown in FIG. 6 as a block diagram. Here, 100 is the antenna device shown in the first to fourth embodiments. The transmission / reception circuit 101 performs transmission / reception in a predetermined frequency band using the antenna device 100. The control circuit 102 performs data transmission with the transmission / reception circuit 101 and controls the directivity of the antenna device 100. That is, the control of the switch elements 4, 4a, 4b is performed. When a radiating element and at least one parasitic element are used, the control of the parasitic element is also performed to control the radiation pattern in the horizontal plane and the vertical plane. The LAN interface circuit 103 controls data communication with devices connected to the LAN.
[0026]
In the embodiment described above, the MEMS element is used as an impedance circuit mounted between the ground conductor and the parasitic conductor and between the parasitic conductors. However, since it is only necessary that the two components are connected with a predetermined reactance component in terms of high frequency and that the reactance changes, the high frequency switch circuit may be configured using a diode, for example.
[0027]
【The invention's effect】
According to the present invention, the parasitic conductor inclined to the opposite side from the side on which the antenna element is provided has a normal line directed to a low elevation angle direction. The pattern can be directed to a lower elevation direction, and by controlling the impedance of a variable impedance circuit provided between the parasitic conductor and the outer peripheral edge of the plate-like ground conductor, the radiation pattern in the vertical plane in the lower elevation direction Can be controlled. As a result, high communication quality can be obtained in a communication environment in which electromagnetic waves are emitted / incident in a substantially horizontal direction.
[0028]
Further, according to the present invention, the antenna element includes at least one radiator and at least one parasitic element disposed around the radiator, and the effective element length of the parasitic element is set to an electrical value. With the provision of the control means, the pattern in the horizontal plane can also be controlled by the radiating element and the parasitic element.
[0029]
Further, according to the present invention, by forming the parasitic conductor as a cylindrical conductor provided along the outer peripheral edge of the plate-shaped ground conductor, it becomes easy to create the parasitic conductor, and the radiation pattern in a vertical plane is formed. Can be effectively directed to a lower elevation angle (horizontal direction).
[0030]
Further, according to the present invention, by making the plate-like ground conductor substantially circular, the radiation pattern in the horizontal plane can be made rotationally symmetric, and the elevation angle of the maximum gain in the vertical plane in all azimuth directions can be increased. You can lower it.
[0031]
According to the invention, an antenna element including a radiation element and at least one parasitic element disposed around the radiation element is provided on the plate-shaped ground conductor, the parasitic conductor is adjacent to the plate-shaped ground conductor, and the plate-shaped ground conductor is provided. By providing them on substantially the same plane, it is possible to easily create a parasitic conductor and mount a variable impedance circuit.
[0032]
Further, according to the present invention, the variable impedance element is a MEMS element that performs switch control between electrodes by a control voltage, so that the variable impedance circuit mounting portion can be downsized and can be used in a millimeter wave band region or a submillimeter wave region. Can be easily applied.
[0033]
Further, according to the present invention, by providing the antenna device of any one of the above configurations and the communication means for transmitting / receiving a signal for wireless LAN using the antenna device, radiation / incidence of electromagnetic waves is performed in the horizontal direction. A communication terminal device that can obtain high communication quality in a communication environment can be configured.
[Brief description of the drawings]
FIG. 1 is an external perspective view and a circuit diagram of an antenna device according to a first embodiment. FIG. 2 is a diagram showing an example of a radiation pattern in a vertical plane of the antenna device. FIG. FIG. 4 is an external perspective view of an antenna device according to a third embodiment. FIG. 5 is an external perspective view of an antenna device according to a fourth embodiment. FIG. 6 is a fifth embodiment. FIG. 7 is a block diagram showing the configuration of such a communication terminal device. FIG. 7 is an external perspective view of a conventional antenna device.
1-radiating element 2-ground conductor 3-parasitic conductor 4-switching element 11-radiating element 12-parasitic element 100-antenna device

Claims (7)

A plate-like ground conductor, an antenna element disposed substantially perpendicular to the plate-like ground conductor, and a parasitic conductor inclined from the outer peripheral edge of the plate-like ground conductor to a side opposite to the side on which the antenna element is provided. An antenna device comprising: a variable impedance circuit that changes impedance between the plate-shaped ground conductor and the parasitic conductor; and a unit that controls the variable impedance circuit. The antenna element includes at least one radiating element and at least one parasitic element disposed around the radiating element, and control means for electrically changing an effective element length of the parasitic element is provided. The antenna device according to claim 1. The antenna device according to claim 1, wherein the parasitic conductor is a cylindrical conductor provided along an outer peripheral edge of the plate-like ground conductor. The antenna device according to claim 1, 2 or 3, wherein the plate-like ground conductor has a substantially circular shape. A plate-shaped ground conductor, an antenna element including at least one radiating element provided in a direction substantially perpendicular to the plate-shaped ground conductor, and at least one parasitic element disposed around the radiating element, Control means for electrically changing the effective element length of the parasitic element; a parasitic conductor adjacent to the plate-like ground conductor and extending substantially on the same plane as the plate-like ground conductor; An antenna device comprising: a variable impedance circuit that changes impedance between a parasitic conductor and a unit that controls the variable impedance circuit. The antenna device according to any one of claims 1 to 5, wherein the variable impedance circuit includes a MEMS element that performs switch control between electrodes by a control voltage. A communication terminal device comprising: the antenna device according to any one of claims 1 to 6; and communication means for transmitting / receiving a signal for a wireless LAN using the antenna device.

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