JP2007027982A - Antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna system for mounting a directivity variable antenna operable even at a several GHz band with nearly the same size as that of an omnidirectional antenna by using a low-cost and easy-mount method and the characteristic of which can be enhanced by eliminating the need for a wire connection part. <P>SOLUTION: The antenna system provided with: the ominidirectional antenna comprising a radiation element 3 and a ground plate 5; a coaxial line 1 provided continuously to the omnidirectional antenna; a dielectric film 15 comprising a dielectric body provided on the ground plate 5; a short-circuit line 11 formed with a conductor pattern on the dielectric film 15 for the purpose of short-circuiting an inner conductor and an outer conductor of the coaxial line; a switch 9 provided to the midway of the short-circuit line 11 to switch a short-circuit state and no short-circuit state; and a capacitor 13 for grounding the short-circuit line 11 to the ground plate 5 in terms of a high frequency is provided and the dielectric layer of the capacitor 13 is configured of the dielectric film 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a directivity variable antenna apparatus capable of switching the directivity of an antenna, and in particular, a low-cost directivity variable antenna that can operate in a few GHz band and is as large as an omnidirectional antenna. The present invention relates to an antenna device capable of improving characteristics by eliminating a wire connecting portion while using an easy mounting method.

With the rapid development of wireless communication technology in recent years, products using wireless technology have started to spread widely, and great expectations are placed on expanding the transmission capacity of wireless communication paths. In recent years, research has been actively conducted to increase the transmission capacity by multiplexing multi-dimensional signals such as time, space, polarization, and code.
Multiplexing by space is considered to be realized by an adaptive array antenna consisting of a plurality of omnidirectional antennas and a circuit that synthesizes the signal, but the size and spacing of each antenna increases. It was the cause that limited the application destination. In particular, for use in a mobile communication terminal, it is desired that the size of the antenna be as small as possible.
The directivity variable antenna can usually be made smaller than an adaptive array antenna because its directivity can be changed by a pair of antennas and a feeding circuit, and as a candidate for a small antenna that realizes multiplexing by space Although it is expected, there are few examples of research on the miniaturization of the variable directivity antenna, and its development has been expected.

As an example of a conventional variable directivity antenna, one shown in FIG. 6 is known (Patent Document 1). As shown in FIG. 6, since this antenna is configured such that the reflecting element 103 can mechanically circulate around the radiating element 101, the directivity of the antenna can be easily changed. In the case of this antenna, the size of the antenna is remarkably large due to the addition of the reflective element.
In addition, FIG. 7 discloses an example of an antenna whose directivity can be switched electrically (Patent Document 2). As shown in FIG. 7, in this antenna, a central driving element 113 and a parasitic element 115 are arranged on a circular ground conductor 110 in a position that surrounds the central driving element 113 radially, and an impedance load is placed below the parasitic element 115. 117 is provided, and the directivity is switched by switching the impedance. The distance between the central driving element 113 and the parasitic element 115 is about λ / 4, and the entire antenna has a size of 2λ or more.
FIG. 8 discloses a similar example of a conventional directional variable antenna (Patent Document 3). As shown in FIG. 8, in this antenna, the feed antenna element A0 and the parasitic variable reactance elements A1 to A6 are arranged on a circular ground conductor 120 at positions radially surrounding it. The distance d between the feeding antenna element and the parasitic variable reactance element has a value of about λ / 4, and the whole antenna has a size of about λ.
As described above, the size of the conventional directional variable antenna is larger than that of the omnidirectional antenna. On the other hand, a directivity variable antenna having the same size as an omnidirectional antenna has been proposed (Patent Document 4).
The detailed characteristics of one implementation form of this antenna are disclosed in Non-Patent Document 1, and it is shown that the directivity can be changed in the same size as the omnidirectional antenna over a wide frequency band.

Also, Non-Patent Document 2 reports an example in which the variation in directivity shape is reduced by flip-chip mounting the diode of the antenna and eliminating the wire connection portion to improve the shape reproducibility of the short-circuit portion. Has been. FIG. 9 is a diagram of a directional variable antenna disclosed in Non-Patent Document 2. This directivity variable antenna has a short-circuit line 131 for short-circuiting the inner conductor 130a and the outer conductor 130b of the coaxial line to the coaxial line 130 of the antenna feeding section, and for switching a short-circuit / non-short-circuit state in the middle of the short-circuit line. A switch 133 and a capacitor 135 for grounding the short-circuit line 131 to the ground plane at a high frequency are provided on the ground plane 137.
10 shows a state with the conventional wire connection portion in the directivity variable antenna of FIG. 9, and FIG. 11 shows a state without the wire connection portion in the directivity variable antenna of FIG.
Japanese Patent Laid-Open No. 06-350334 Japanese Patent Laid-Open No. 10-154911 JP 2001-24431 A JP 2004-304785 A Sakakibara, Hoshi, Sugai, Sato, “Proposal of antenna directivity control technology using coaxial short-circuit structure”, IEICE Tech. Bulletin, AP2003-274., 2004 Hagiwara, Hoshi, Aoi, “Directive Variable Antenna Using Coaxial Short-Circuited Structure”, UEC, B-1-146., 2004

However, in order to realize the configuration of FIG. 6, it is necessary to use a capacitor having a thickness about the dielectric film, and the mounting method has become complicated.
A directional variable antenna with the same size as an omnidirectional antenna with improved characteristics by eliminating wire connections in this way requires the use of a capacitor with a dielectric film thickness. The method was also complicated. For this reason, it is difficult to reduce costs because the degree of freedom in selecting capacitors is low and mounting is difficult. For this reason, it is difficult to use the variable directivity antenna in a communication terminal or the like.
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to reduce the cost of a directional variable antenna that can operate in a few GHz band and is as large as an omnidirectional antenna. It is an object of the present invention to provide an antenna device capable of improving characteristics by eliminating a wire connecting portion while using an easy mounting method.

In order to achieve the above object, an invention according to claim 1 is directed to an omnidirectional antenna including a radiating element and a ground plane, a coaxial line continuously provided on the omnidirectional antenna, and a ground plane. A dielectric film made of a provided dielectric, a short-circuit line formed of a conductor pattern on the dielectric film to short-circuit the inner conductor and the outer conductor of the coaxial line, and a short circuit in the middle of the short-circuit line, An antenna device comprising a switch provided for switching a non-short-circuit state and a capacitor for grounding the short-circuit line to the ground plane in a high-frequency manner, wherein the dielectric layer of the capacitor is the dielectric film. It is characterized by comprising.
According to a second aspect of the present invention, one of the electrodes constituting the capacitor is composed of a conductor pattern formed in the same process as the short-circuit line, and the other electrode is on the opposite surface of the dielectric film. It consists of the formed counter electrode.
The invention according to claim 3 is characterized in that the counter electrode comprises a part of the ground plane.
The invention according to claim 4 is characterized in that the ground plate is formed by extending the counter electrode.
The invention according to claim 5 includes an omnidirectional antenna including a radiating element and a ground plane, a coaxial line provided continuously to the omnidirectional antenna, and a dielectric provided on the ground plane. In order to switch between a short-circuited state and a non-short-circuited state in the middle of the short-circuited line formed with a conductor pattern on the dielectric film and a short-circuit between the dielectric film, the inner conductor and the outer conductor of the coaxial line An antenna device comprising a provided switch and a capacitor for grounding the short-circuit line to the ground plane in a high-frequency manner, wherein a dielectric layer of the capacitor is formed of a dielectric thin film thinner than the dielectric film It is characterized by that.

  According to the present invention, since the dielectric layer of the capacitor is composed of the dielectric film, the directional variable antenna having the same size as the omnidirectional antenna can be operated even in a few GHz band. While using a low-cost and easy mounting method, it is possible to improve the characteristics by eliminating the wire connection portion, and it becomes possible to use the directivity variable antenna in a communication terminal or the like.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
<Example>
FIG. 1 is a configuration diagram of a first embodiment relating to a main part of an antenna device according to the present invention, in which (a) is a perspective view and (b) is a cross-sectional view.
As shown in FIG. 1, this antenna device is a discone antenna composed of a radiating element 3 and a ground plane 5 as a non-directional antenna fed by a coaxial line 1, and is made of a dielectric provided on the ground plane 5. A short-circuit wire 11 formed of a conductor pattern on the dielectric film 15 in order to short-circuit the inner conductor 1a and the outer conductor 1b of the coaxial line 1; The switch 9 provided for switching the state and a capacitor 13 for grounding the short-circuit wire 11 to the ground plane 5 at a high frequency are provided.
That is, a dielectric film 15 on which a bias wire 7, a switch 9, a short-circuit wire 11, and one electrode 13 a of a capacitor 13 are formed as a connection portion between the coaxial line 1 and the radiating element 3 is attached on the ground plane 5. Therefore, the short circuit can be electrically turned ON / OFF in four directions within the surface of the main plate 5.
The capacitor 13 includes an electrode 13a, a dielectric film 15, and a counter electrode 17, and both the electrodes 13a and 17 are formed of a metal pattern on the dielectric film 15. That is, one electrode 13 a constituting the capacitor 13 is composed of a conductor pattern electrode 13 a formed in the same process as the short-circuit line 11.
The outer edge shape of the capacitor 13 is composed of an arc portion 13b centered on the coaxial line 1 and a linear shape portion 13c along the radial direction, and obstructs the ground current that contributes to antenna radiation while being close to the coaxial line 1. It has become difficult. That is, in the first embodiment, the dielectric layer of the capacitor 13 is constituted by the dielectric film 15.
In the first embodiment, a PIN diode is used as the switch 9, and the ON / OFF state can be controlled electrically using the bias line 7 from the outside of the antenna. If all the switches 9 are turned OFF, the electric field distribution of the coaxial line 1 is not disturbed, and the radiation pattern of the antenna remains omnidirectional.
On the other hand, when only one switch 9 is inserted, the electric field in the coaxial line 1 is disturbed, and the radiation pattern of the antenna has directivity. It is also possible to change the directivity of the antenna by switching the switch to be turned on.

FIG. 2C is an equivalent circuit diagram showing an example of the switch 9 in FIGS. 1A and 1B. In FIG. 2C, A, B, E are terminals, D is a PIN diode, C is a capacitor, L is an inductor, R is a resistance, terminal A is a signal line of coaxial line 1, and terminal B Is connected to the ground conductor of the coaxial line 1, and the terminal E is connected to the bias line 7 on the dielectric film 15. The PIN diode D is grounded at a high frequency by the capacitor C, and by changing the value of the DC bias applied to the terminal E, the resistance value of the PIN diode D changes greatly, so that it can be operated as a switch. It has become.
FIG. 2D is a characteristic diagram for explaining the directivity of the directivity variable antenna according to the first embodiment. FIG. 2D shows the antenna gain at an elevation angle of 45 degrees from the ground plane 5 for 360 degrees with the switch 9 to be turned on as the reference (0 degree) with the radiator as the center.
In FIG. 2D, the solid line indicates the gain when one switch 9 in the direction of the angle of 0 degrees is turned ON, and the dotted line indicates the gain when all the switches 9 are turned OFF. As can be seen from the figure, when all the switches 9 are turned OFF, a constant gain is obtained at any angle, and omnidirectionality is obtained. Further, it is shown that the directivity changes by turning on the switch, and the radiation intensity in the direction opposite to the switch that is turned on becomes stronger.
As is apparent from the first embodiment, the directivity variable antenna according to the present invention has the same size as a normal omnidirectional antenna and can switch the directivity. Further, the characteristics are improved by eliminating the wire connection portion of the coaxial short-circuit portion 1, but the capacitor 13 is realized by the dielectric film 15, so that the cost of the capacitor 13 is reduced and the mounting is simplified.

Next, a second embodiment of the present invention will be described with reference to FIG.
3A and 3B are configuration diagrams of a second embodiment relating to the main part of the antenna device according to the present invention, in which FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view.
As shown in FIG. 3, the antenna device of the second embodiment is a discone antenna including a radiating element 3 and a ground plane 5 as a non-directional antenna fed by a coaxial line 1, and is provided on the ground plane 5. A dielectric film 15 made of a dielectric material, a short-circuit wire 11 formed of a conductor pattern on the dielectric film 15 in order to short-circuit the inner conductor 1a and the outer conductor 1b of the coaxial line 1; The switch 9 is provided for switching between the short-circuited state and the non-short-circuited state, and the capacitor 13 for grounding the short-circuited wire 11 to the ground plane 5 at a high frequency.
That is, a dielectric film 15 on which a bias wire 7, a switch 9, a short-circuit wire 11, and one electrode 13 a of a capacitor 13 are formed as a connection portion between the coaxial line 1 and the radiating element 3 is attached on the ground plane 5. Therefore, the short circuit can be electrically turned ON / OFF in four directions within the surface of the main plate 5.
In the second embodiment, the capacitor 13 is composed of an electrode 13 a, a dielectric film 15, and a part of the ground plane 5, and the electrode 13 a is formed by a metal pattern on the dielectric film 15. That is, one of the electrodes constituting the capacitor 13 is composed of a conductor pattern electrode 13a formed in the same process as the short-circuit wire 11, and the other counter electrode is an electrode composed of a part of the ground plane 5 of the antenna. It is composed.
The outer edge shape of the capacitor 13 is composed of an arc portion 13b centered on the coaxial line 1 and a linear shape portion 13c along the radial direction, and obstructs the ground current that contributes to antenna radiation while being close to the coaxial line 1. It has become difficult. That is, the dielectric layer of the capacitor 13 is composed of the dielectric film 15.
Here, a PIN diode is used as the switch 9, and the ON / OFF state can be electrically controlled from the outside of the antenna using the bias line 7.
If all the switches 9 are turned OFF, the electric field distribution of the coaxial line is not disturbed, and the radiation pattern of the antenna remains omnidirectional. On the other hand, when only one switch 9 is inserted, the electric field in the coaxial line 1 is disturbed, and the radiation pattern of the antenna has directivity. It is also possible to switch the directivity of the antenna by switching the switch 9 to be turned on.

Next, a third embodiment of the present invention will be described with reference to FIG.
4A and 4B are configuration diagrams of a third embodiment relating to the main part of the antenna device according to the present invention, in which FIG. 4A is a perspective view and FIG. 4B is a cross-sectional view.
As shown in FIG. 4, the antenna device of the third embodiment is a discone antenna including a radiating element 3 and a ground plane 23 as an omnidirectional antenna fed by a coaxial line 1, and is provided on the ground plane 23. A dielectric film 15 made of a dielectric material, a short-circuit wire 11 formed of a conductor pattern on the dielectric film 15 in order to short-circuit the inner conductor 1a and the outer conductor 1b of the coaxial line 1; The switch 9 is provided for switching between a short-circuited state and a non-short-circuited state, and a capacitor 13 for grounding the short-circuited wire 11 to the ground plane 23 at a high frequency.
That is, on the support plate 21 made of a dielectric material, the dielectric film 15 is formed with the bias line 7, the switch 9, the short-circuit line 11, and the ground plate 23 extending from one electrode 13 a and the counter electrode 23 a of the capacitor 13. Is attached so that the short circuit can be electrically turned ON / OFF in four directions in the plane of the ground plane 5 at the connection portion between the coaxial line 1 and the radiating element 3. That is, in the third embodiment, the ground plane 23 is obtained by extending the counter electrode 23a.

The capacitor 13 includes an electrode 13a, a dielectric film 15, and a counter electrode 23a. Both the electrodes 13a and 23a are formed of a metal pattern on the dielectric film. That is, one of the electrodes 13 constituting the capacitor is constituted by an electrode 13a having a conductor pattern formed in the same process as the short-circuit line 11, and the other electrode (counter electrode) 23a is provided on the opposite surface of the dielectric film 15. It is the structure formed in.
The outer edge shape of the capacitor 13 is composed of a circular arc portion 13b centered on the coaxial line and a linear shape portion 13c along the radial direction, and is close to the coaxial line 1 and hardly interferes with the ground plane current contributing to antenna radiation. It has become. In the third embodiment, the length of the arc portion 13b of the capacitor 13 is longer than that in the first and second embodiments.
Here, a PIN diode is used as the switch 9, and the ON / OFF state can be electrically controlled from the outside of the antenna using the bias line 7.
If all the switches 9 are turned off, the electric field distribution of the coaxial line 1 is not disturbed, and the radiation pattern of the antenna remains omnidirectional.
On the other hand, when only one switch 9 is inserted, the electric field in the coaxial line 1 is disturbed, and the radiation pattern of the antenna has directivity. It is also possible to switch the directivity of the antenna by switching the switch 9 to be turned on.

FIG. 5 is a configuration diagram of a fourth embodiment relating to the main part of the antenna device according to the present invention, wherein (a) is a perspective view and (b) is a cross-sectional view.
As shown in FIG. 5, the antenna device of the fourth embodiment is a discone antenna including a radiating element 3 and a ground plane 5 as an omnidirectional antenna fed by a coaxial line 1, and is provided on the ground plane 5. A dielectric film 15 made of a dielectric material, a short-circuit wire 11 formed in a conductor pattern on the dielectric film 15 in order to short-circuit the inner conductor 1a and the outer conductor 1b of the coaxial line 1; The switch 9 is provided for switching between a short-circuited state and a non-short-circuited state, and a capacitor 13 for grounding the short-circuited wire 11 to the ground plane 5 at a high frequency.
That is, a dielectric film 15 on which a bias line 7 and a switch 9, a short-circuit line 11 and a capacitor 13 are formed is affixed on the ground plane 5. It is possible to electrically turn on / off the short circuit in the four directions.
The capacitor 13 includes a conductor pattern electrode 13 a formed in the same process as the short-circuit line 11 formed on the dielectric film 15, a metal pattern 17 serving as a counter electrode, and a dielectric thin film 25 thinner than the dielectric film 15. As compared with the case where a dielectric film is used as a capacitor, a large capacity can be realized with an equivalent electrode area.
That is, the dielectric layer of the capacitor 13 is composed of a dielectric thin film 25 thinner than the dielectric film 15.
The outer edge shape of the capacitor 13 is composed of an arc portion 13b centered on the coaxial line 1 and a linear shape portion 13c along the radial direction, and obstructs the ground current that contributes to antenna radiation while being close to the coaxial line 1. Here, a PIN diode is used as the switch 9, and the ON / OFF state can be electrically controlled from the outside of the antenna using the bias line 7. If all the switches 9 are turned OFF, the electric field distribution of the coaxial line is not disturbed, and the radiation pattern of the antenna remains omnidirectional.
On the other hand, when only one switch 9 is inserted, the electric field in the coaxial line 1 is disturbed, and the radiation pattern of the antenna has directivity. It is also possible to switch the directivity of the antenna by switching the switch to be turned on.
Although the present invention has been described based on the embodiments, the present invention is by no means limited to the requirements shown here, such as the shapes raised in the above embodiments and combinations with other elements. With respect to these points, the present invention can be changed within a range that does not detract from the gist of the present invention, and can be appropriately determined according to the application form.

It is a block diagram of 1st Embodiment regarding the principal part of the antenna device by this invention, (a) is a perspective view, (b) is sectional drawing. It is explanatory drawing of 1st Embodiment, (c) is an equivalent circuit schematic which shows an example of the switch in FIG. 1 (a), (b), (d) is the directivity of the directivity variable antenna in 1st Embodiment. The characteristic view for demonstrating property. It is a block diagram of 2nd Embodiment regarding the principal part of the antenna apparatus by this invention, (a) is a perspective view, (b) is sectional drawing. It is a block diagram of 3rd Embodiment regarding the principal part of the antenna device by this invention, (a) is a perspective view, (b) is sectional drawing. It is a block diagram of 4th Embodiment regarding the principal part of the antenna device by this invention, (a) is a perspective view, (b) is sectional drawing. The figure which shows an example of the conventional directivity variable antenna. The figure which shows an example of the conventional directivity variable antenna. The figure which shows an example of the conventional directivity variable antenna. The figure which shows an example of the conventional directivity variable antenna. The figure which shows an example of the conventional directivity variable antenna. The figure which shows an example of the conventional directivity variable antenna.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a ... Inner conductor, 1b ... Outer conductor, 1 ... Coaxial line, 3 ... Radiation element, 5 ... Ground plane, 7 ... Bias line, 9 ... Switch, 11 ... Short circuit wire, 13a ... Electrode, 13b ... Arc part, 13c ... Straight line Shape part, 13 ... Capacitor, 15 ... Dielectric film, 17 ... Counter electrode, 21 ... Support plate, 23a ... Counter electrode, 23 ... Ground plate, 25 ... Dielectric thin film

Claims (5)

An omnidirectional antenna comprising a radiating element and a ground plane; a coaxial line continuously provided on the omnidirectional antenna; a dielectric film comprising a dielectric provided on the ground plane; A short-circuit line formed of a conductor pattern on the dielectric film to short-circuit the conductor and the outer conductor, a switch provided to switch between a short circuit and a non-short circuit state in the middle of the short-circuit line, and the short-circuit line An antenna device comprising a capacitor for grounding to the ground plane at a high frequency,
An antenna device, wherein a dielectric layer of the capacitor is formed of the dielectric film.   One of the electrodes constituting the capacitor is composed of a conductor pattern formed in the same process as the short-circuit line, and the other electrode is composed of a counter electrode formed on the opposite surface of the dielectric film. The antenna device according to claim 1.   The antenna device according to claim 2, wherein the counter electrode is a part of the ground plane.   The antenna device according to claim 2, wherein the ground plane is formed by extending the counter electrode. An omnidirectional antenna comprising a radiating element and a ground plane; a coaxial line continuously provided on the omnidirectional antenna; a dielectric film comprising a dielectric provided on the ground plane; A short-circuit line formed of a conductor pattern on the dielectric film to short-circuit the conductor and the outer conductor, a switch provided to switch between a short circuit and a non-short circuit state in the middle of the short-circuit line, and the short-circuit line An antenna device comprising a capacitor for grounding to the ground plane at a high frequency,
An antenna device, wherein a dielectric layer of the capacitor is formed of a dielectric thin film thinner than the dielectric film.

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