JP7234732B2 - antenna device - Google Patents

Description

The present invention relates to an antenna device, and more particularly to an antenna device capable of transmitting and receiving radio waves of multiple types of polarized waves.

Patent Literature 1 discloses an antenna device capable of receiving circularly polarized waves and linearly polarized waves. The antenna device disclosed in Patent Document 1 includes a patch antenna for receiving circularly polarized satellite waves from the zenith direction and a patch antenna for receiving horizontally polarized terrestrial waves. there is It also has a vertical antenna element section for terrestrial waves.

JP-A-2003-347838

Since Patent Document 1 includes a vertical antenna element section for terrestrial waves, the height of the antenna device may increase.

The present disclosure has been made based on this situation, and its object is to provide an antenna device that can transmit and receive multiple types of linearly polarized waves with different planes of polarization and that can be miniaturized. to do.

The above objects are achieved by the combination of features stated in the independent claims, and the sub-claims define further advantageous embodiments. The symbols in parentheses described in the claims indicate the corresponding relationship with specific means described in the embodiments described later as one aspect, and do not limit the disclosed technical scope.

One disclosure for achieving the above objectives is
a flat base plate (10);
a conductive conductor plate (30) spaced apart from the ground plane;
a feeder (40) connected to the conductor plate;
An antenna device comprising a short-circuit portion (50) that electrically connects a ground plane and a conductor plate ,
The ground plane includes a facing ground plane (11) including a portion facing the conductor plate and having a short-circuit portion arranged in the center, and a non-facing ground plate (12) not facing the conductor plate,
The non-opposing ground plate is arranged next to the opposing ground plate with a predetermined spacing from the opposing ground plate ,
The opposing ground plane and the non-opposing ground plane are connected via a switch (60) that switches between a state in which the opposing ground plane and the non-opposing ground plane are electrically connected and a state in which they are electrically disconnected.

In this antenna device, when the switch is off, parallel resonance occurs at a frequency corresponding to the capacitance and the inductance due to the capacitance formed between the opposing ground plane and the conductor plate and the inductance of the short circuit. give rise to Due to the vertical electric field generated between the conductor plate and the opposing ground plane due to the parallel resonance, radio waves are transmitted and received in the direction along the conductor plate and the opposing ground plane and in the plane of polarization perpendicular to the conductor plate and the opposing ground plane. This radio wave is a vertically polarized radio wave if the direction from the opposing ground plane to the conductor plate is vertical.

Further, since the non-opposing ground plane is arranged asymmetrically with respect to the opposing ground plane, when the opposing ground plane and the non-opposing ground plane are connected by the switch, the ground planes become asymmetric when viewed from the short-circuit portion. When the ground plane becomes asymmetrical as viewed from the short circuit, the degree to which the current flowing through the ground plane is canceled between one side and the other side of the short circuit is reduced. As the current flowing through the ground plane remains without being canceled, the electric field generated by the current propagates in space. That is, radio waves are radiated from the ground plane. At this time, the ground plane operates as a pole-type antenna element. Therefore, the radio wave radiated from the ground plane is a linearly polarized wave whose plane of polarization is parallel to the antenna element. When the ground plane is arranged horizontally, the radio waves radiated from the ground plane, which is the antenna element, are horizontally polarized waves.

Thus, this antenna device can transmit and receive a plurality of types of linearly polarized waves with different planes of polarization. When the ground plane is arranged horizontally, the antenna device can transmit and receive vertically polarized waves and horizontally polarized waves.

Moreover, the vertically polarized wave is generated by causing parallel resonance due to the capacitance formed between the opposing ground plane and the conductor plate and the inductance of the short-circuit portion. Therefore, the size of the antenna device in the height direction can be reduced.

In addition, in this antenna device, when the switch is turned on, the ground plane operates as an antenna element for horizontally polarized waves to transmit and receive horizontally polarized waves. In order to operate the ground plane as an antenna element for horizontal polarization, the non-facing ground plane should be arranged adjacent to the opposing ground plane and a switch should be provided. Therefore, the size of the antenna device in the planar direction of the ground plane can be made smaller than when the antenna for horizontal polarization is provided separately from the antenna for vertical polarization.

1 is a perspective view of an antenna device 1; FIG. FIG. 2 is a sectional view taken along the line II-II of FIG. 1; It is the figure which looked at the antenna apparatus 1 from the back surface. 3A and 3B are diagrams for explaining a current distribution, a voltage distribution, and an electric field distribution in the vicinity of a conductor plate 30; FIG. FIG. 4 is a diagram for explaining the current distribution flowing through the opposing ground plane 11 when the switch 60 is off; FIG. 4 is a diagram for explaining current distributions flowing through an opposing ground plane 11 and a non-opposing ground plane 12 when a switch 60 is on; FIG. 10 is a diagram showing a configuration of an antenna device 100 of Modified Example 3;

Hereinafter, embodiments will be described based on the drawings. FIG. 1 is a perspective view of an antenna device 1 of this embodiment. Antenna device 1 is used in a vehicle, for example, and is mounted on the roof of the vehicle. The antenna device 1 performs one or both of radio wave transmission and reception. The antenna device 1 is connected to a wireless device (not shown) via, for example, a coaxial cable, and signals received by the antenna device 1 are sequentially output to the wireless device.

The wireless device uses the signal received by the antenna device 1 and supplies the antenna device 1 with high-frequency power according to the transmission signal. In addition to the coaxial cable, other feeder lines such as a feeder line may be used as the feeder line to the antenna device 1 . A specific configuration of the antenna device 1 will be described below.

The antenna device 1 includes a planar base plate 10 . More specifically, the ground plate 10 has a configuration including an opposed ground plate 11 and a non-opposed ground plate 12 . The opposing ground plane 11 is electrically connected to the outer conductor of the coaxial cable and forms a ground potential in the antenna device 1 . Both the opposing ground plate 11 and the non-facing ground plate 12 are flat. The plate also includes a thin thickness such as a foil.

The base plate 10 is attached to the back surface 21 of the support plate 20 . The support plate 20 is made of an insulating material such as glass epoxy resin. The support plate 20 is a member for arranging the ground plate 10 and the conductor plate 30 with a predetermined gap so that their planar portions face each other. The support plate 20 has a rectangular flat plate shape, and the size of the support plate 20 is substantially the same as that of the main plate 10 in plan view.

Further, in the present embodiment, the space between the ground plate 10 and the conductor plate 30 is filled with resin (that is, the support plate 20), but the present invention is not limited to this. The space between the ground plane 10 and the conductor plate 30 may be hollow or may be filled with a dielectric having a predetermined dielectric ratio.

A conductor plate 30 is arranged on the surface 22 of the support plate 20 at a position facing the opposing ground plate 11 with the support plate 20 interposed therebetween. The conductor plate 30 is parallel to the ground plane 10 with the support plate 20 interposed therebetween. The material of the conductor plate 30 is a conductor such as copper. The shape of the conductor plate 30 is a square plate. The shape of the conductor plate 30 may be a rotationally symmetrical plane figure other than a square (for example, a circle, a regular hexagon). Also, the shape of the conductor plate 30 may be a shape (for example, a rectangle) that is symmetrical with respect to two straight lines that pass through the center and are perpendicular to each other. In addition, the shape of the conductor plate 30 may be a non-symmetrical shape. The size of the conductor plate 30 is the same size as the opposing ground plate 11 or smaller than the opposing ground plate 11 .

FIG. 2 is a sectional view taken along line II-II of FIG. As shown in FIGS. 2 and 1 , the antenna device 1 also includes a feeding section 40 and a short circuit section 50 . The power feeding section 40 is a section that electrically connects the conductor plate 30 and the coaxial cable, and feeds power to the conductor plate 30 via the coaxial cable. In the present embodiment, the position where the power supply portion 40 is arranged is on a line that passes through the center of the conductor plate 30 and divides the conductor plate 30 in half.

The short-circuit portion 50 electrically connects the conductor plate 30 and the opposing ground plate 11 . The short circuit portion 50 is connected to the central portion of the conductor plate 30 . The central portion means the center of the conductor plate 30 and its vicinity. The short 50 can be realized with a conductive pin. The inductance of the short-circuit portion 50 can be adjusted by the thickness of the pin.

By facing each other, the conductor plate 30 and the counter ground plate 11 can be regarded as a capacitor that forms a capacitance corresponding to the area of the conductor plate 30 . The area of the conductor plate 30 is set to an area that forms the inductance component of the short-circuit portion 50 and the capacitance that resonates in parallel at a predetermined frequency. This frequency may be appropriately designed. Examples of this frequency include 2.45 GHz, which is the ISM band, and frequencies used in vehicle-to-vehicle and road-to-vehicle communications (such as 760 MHz).

FIG. 3 is a view of the antenna device 1 viewed from the rear surface 21 side of the support plate 20. As shown in FIG. As shown in FIG. 3, the shape of the opposing ground plate 11 is rectangular in this embodiment. However, the shape of the opposing ground plate 11 is not limited to a rectangular shape. For example, the shape of the opposing ground plate 11 may be a square or a polygon other than a quadrangle. The conductor plate 30 is arranged at a position where its center is the central portion of the opposing ground plate 11 .

The non-facing ground plane 12 is a ground plane that does not have a portion facing the conductor plate 30 . The non-opposed ground plate 12 is arranged adjacent to one side of the opposed ground plate 11 . Therefore, the non-opposing ground plate 12 is arranged asymmetrically with respect to the opposing ground plate 11 . The shape of the non-opposing base plate 12 is also rectangular. The length in the longitudinal direction of the non-opposing ground plate 12 is half the wavelength of the radio wave with which the antenna device 1 operates in this embodiment. Note that the length in this specification is the electrical length unless otherwise specified. In addition, all lengths are used not only to refer to those that completely match the length of the notation, but also to include those that are substantially the length of the notation.

The switch 60 switches between a state in which the opposing ground plane 11 and the non-opposing ground plane 12 are electrically connected and a state in which they are electrically disconnected. The switch 60 is on/off controlled by the radio.

In this embodiment, the switch 60 connects the edges of the opposing ground plate 11 and the non-facing ground plate 12 . The edge portion means a portion through which a relatively large amount of current flows compared to the central portion of the opposing ground plate 11 when current flows through the opposing ground plate 11 . For example, two portions at both ends of the widthwise side of the opposed base plate 11 divided into four can be used as edge portions.

[Description of operation]
The operation of the antenna device 1 configured in this manner will be described. The antenna device 1 operates differently when the switch 60 is off and when the switch 60 is on. In the following description, it is assumed that the base plate 10 is arranged horizontally for convenience of description. However, when the antenna device 1 is actually used, the angle of the ground plane 10 can be appropriately adjusted according to the usage environment and the like.

[When the switch 60 is off]
First, the operation of the antenna device 1 when the switch 60 is off will be described. The conductor plate 30 is short-circuited to the opposing ground plate 11 at the short-circuit portion 50 provided in its central portion, and the area of the conductor plate 30 forms a capacitance that resonates in parallel with the inductance of the short-circuit portion 50 at the frequency. It is the area to do.

Therefore, parallel resonance occurs due to energy exchange between the inductance and the capacitance, and an electric field perpendicular to the ground plane 10 and the conductor plate 30 is generated between the opposed ground plane 11 and the conductor plane 30 . This vertical electric field propagates from the short-circuit portion 50 toward the edge of the conductor plate 30 , and at the edge of the conductor plate 30 , the vertical electric field becomes a vertically polarized electric field and propagates through space.

More specifically, in the conductor plate 30, the current flows in the direction from the edges of the conductor plate 30 toward the central portion where the short circuit portion 50 is provided. That is, as shown in FIG. 4, the current concentrates in the central portion of the conductor plate 30, and the amplitude of the current standing wave is maximum at the central portion of the conductor plate 30 and 0 at both ends.

Further, since the short-circuit portion 50 is provided in the central portion of the conductor plate 30, the voltage standing wave has the maximum amplitude at both ends of the conductor plate 30 and has zero amplitude near the central portion. Both regions have the same sign (positive state in the figure) in the vertical direction.

Since the vertical electric field generated between the conductor plate 30 and the opposing ground plane 11 is proportional to the voltage distribution, the traveling direction of the electric field is the same in any region when viewed from the short circuit portion 50 . In addition, the strength is 0 near the central portion and is maximum at the outer edge of the conductor plate 30 . In other words, the electric field intensity increases from the short-circuit portion 50 toward the outer edge of the conductor plate 30 , and is radiated as a linearly polarized wave perpendicular to the planes of the opposing ground plate 11 and the conductor plate 30 at the edge. This linear polarization is vertical polarization when the opposing ground plane 11 is horizontally installed.

In other words, the antenna device 1 has directivity of vertically polarized waves in all directions in the horizontal direction. In addition, since the propagation direction of the electric field is symmetrical with respect to the short-circuit portion 50, the same level of gain is obtained in all directions on the horizontal plane.

[When the switch 60 is on]
Next, the operation when the switch 60 is on will be described. FIG. 5 conceptually shows the current flowing through the opposing ground plane 11 when the switch 60 is off. The size of the arrow in FIG. 5 indicates the amplitude of the current. The current that flows from the conductor plate 30 through the short-circuit portion 50 and into the opposing ground plane 11 flows from the short-circuit portion 50 to both sides of the opposing ground plane 11 in the longitudinal direction. Since the short-circuiting portion 50 is connected to the center of the opposing ground plate 11 in the longitudinal direction, when the switch 60 is turned off, when viewed from the short-circuiting portion 50, the length to one end in the longitudinal direction of the opposing ground plate 11 is , the length to the other end in the longitudinal direction of the opposing ground plate 11 is equal.

Therefore, the current flowing from the short circuit portion 50 in one longitudinal direction of the opposing ground plate 11 and the current flowing from the short circuit portion 50 in the other longitudinal direction of the opposing ground plate 11 are opposite in direction and equal in magnitude. When the current flows through the opposing ground plane 11 in this manner, the electric field generated by the current is cancelled. Therefore, radio waves are not radiated from the opposing ground plate 11 .

However, when the switch 60 is on, as shown in FIG. 6, current flows from the end of the opposed ground plane 11 to the non-opposed ground plane 12 via the switch 60 . Since the non-opposing ground plane 12 is arranged asymmetrically with respect to the opposing ground plane 11 , when the opposing ground plane 11 and the non-opposing ground plane 12 are connected by the switch 60 , the ground plane 10 becomes asymmetrical when viewed from the short circuit portion 50 . Become. When the ground plane 10 becomes asymmetrical when viewed from the short-circuit portion 50, the degree to which the current flowing through the ground plane 10 is canceled between one side and the other side viewed from the short-circuit portion 50 is reduced. Since the current flowing through the ground plane 10 remains without being canceled, the electric field generated by the current propagates in space. That is, radio waves are radiated from the ground plane 10 . At this time, the ground plane 10 operates as a pole-type antenna element. Therefore, the radio wave radiated from the ground plane 10 is a linearly polarized wave having a plane of polarization parallel to the ground plane 10 which operates as an antenna element. When the ground plane 10 is horizontally arranged, horizontally polarized waves are transmitted and received by the ground plane 10 .

[Summary of embodiment]
The antenna device 1 can transmit and receive vertically polarized waves in all horizontal directions when the switch 60 is off. On the other hand, when the switch 60 is on, horizontally polarized waves can be transmitted and received. Thus, the antenna device 1 can transmit and receive vertically polarized waves and horizontally polarized waves by turning the switch 60 on and off.

Moreover, the antenna device 1 generates a vertically polarized wave by causing parallel resonance due to the capacitance formed between the opposing ground plane 11 and the conductor plate 30 and the inductance of the short-circuit portion 50 . A pole-type antenna element requires an electrical length of 1/4 wavelength to transmit and receive vertically polarized waves, whereas the antenna device 1 can achieve a height of 1/100 wavelength. Therefore, the size of the antenna device 1 in the height direction can be reduced.

In addition, in this antenna device 1, when the switch 60 is turned on, the ground plane 10 operates as an antenna element for horizontally polarized waves to transmit and receive horizontally polarized waves. In order to operate the ground plane 10 as an antenna element for horizontally polarized waves, the non-facing ground plane 12 should be arranged adjacent to the opposing ground plane and the switch 60 should be provided. Therefore, the size of the ground plane 10 in the planar direction of the antenna device 1 can be made smaller than when the antenna for horizontal polarization is provided separately from the antenna for vertical polarization.

Further, in this embodiment, the switches 60 are arranged at the edges of the opposed ground plate 11 and the non-opposed ground plate 12 . A large amount of current flows in the edge portion. Therefore, a large amount of current flows from the opposed ground plane 11 to the non-opposed ground plane 12 . This improves the output when the non-opposing base plate 12 operates as a pole-type element.

Further, in the antenna device 1, the length of the non-opposing ground plane 12 is the length of 1/2 wavelength determined based on the operating frequency when the ground plane 10 operates as an antenna element. On the other hand, the current flowing through the opposing ground plane 11 is canceled. Therefore, as conceptually shown in FIG. 6, the non-opposing ground plane 12 resonates at the operating frequency. This improves the transmission/reception performance of horizontally polarized waves.

In addition, if the length of the non-opposing ground plane 12 in the longitudinal direction is half the wavelength, the switch 60 is arranged at the node of the current. Even when the switch 60 is off, current, which is of high frequency, can flow into the switch 60 . If the switch 60 is arranged at a current node, the current flowing from the opposed ground plane 11 to the non-opposed ground plane 12 via the switch 60 can be reduced when the switch 60 is off. As a result, the isolation between the opposed ground plate 11 and the non-opposed ground plate 12 can be increased when the switch 60 is off. Higher isolation can improve antenna performance when switch 60 is off.

Although the embodiments have been described above, the disclosed technology is not limited to the above-described embodiments, and the following modifications are also included in the disclosed scope. Various modifications can be made. In the following description, the elements having the same reference numerals as the reference numerals used so far are the same as the elements having the same reference numerals in the previous embodiments unless otherwise specified. Moreover, when only part of the configuration is described, the previously described embodiments can be applied to the other portions of the configuration.

<Modification 1>
In the embodiment, the longitudinal length of the non-opposing base plate 12 is 1/2 wavelength. As a result, the ground plane 10 mainly operates the non-facing ground plane 12 as a pole-type antenna element. However, the length of the non-opposing ground plane 12 is set so that the total longitudinal length of the opposing ground plane 11 and the non-opposing ground plane 12, which are mutually connected when the switch 60 is turned on, is 1/2 wavelength. may In this way, when switch 60 is on, ground plane 10 as a whole resonates at the operating frequency. That is, the entire ground plane 10 operates as a pole-type antenna element.

<Modification 2>
Further, regardless of whether the non-opposing ground plane 12 of the ground plane 10 mainly operates as an antenna element or the entire ground plane 10 operates as an antenna element, the longitudinal length of the ground plane 10 is not limited to 1/2 wavelength. . If the length of the ground plane 10 in the longitudinal direction is an integer multiple of a quarter wavelength, the ground plane 10 can operate as a pole-type antenna element when the switch 60 is on.

<Modification 3>
As in the antenna device 100 shown in FIG. 7 , the non-opposing ground plane 12 may be divided into two small non-opposing ground plane portions 121 and 122 . The antenna device 100 also includes a polarization ratio control switch 61 in addition to the switch 60 .

The electrical length of the portion acting as the pole antenna element differs between when only the switch 60 is on and when both the switch 60 and the polarization ratio control switch 61 are on. By doing so, the electrical length of the antenna element that operates as a horizontally polarized wave can be switched among a plurality of types. A change in the electrical length changes the output of the horizontally polarized wave. Therefore, by doing so, it is possible to control the output of the horizontally polarized wave and the polarization ratio between the vertically polarized wave and the horizontally polarized wave. The number of small non-opposing ground plate portions 121 and 122 is not limited to two, and may be three or more.

<Modification 4>
The number of switches 60 is not limited to one. Two switches 60 may be arranged so as to connect both longitudinal sides of the opposed ground plate 11 and the non-opposed ground plate 12, respectively. Also, three or more switches 60 may be arranged.

1: Antenna Device 10: Ground Plate 11: Opposed Ground Plate 12: Non-opposed Ground Plate 20: Support Plate 21: Back Side 22: Front Side 30: Conductor Plate 40: Feeding Part 50: Short Circuit Part 60: Switch 61: Polarization Ratio Control Switch 100: Antenna device 121: small non-opposing ground plane part 122: small non-opposing ground plane part

Claims (6)

a flat base plate (10);
a conductive conductor plate (30) spaced apart from the ground plane;
a feeder (40) connected to the conductor plate;
An antenna device comprising a short-circuit portion (50) electrically connecting the ground plate and the conductor plate ,
The ground plane includes a facing ground plane (11) including a portion facing the conductor plate and having the short-circuit portion arranged in the center , and a non-opposing ground plate (12) not facing the conductor plate. equipped with
The non-opposing ground plate is arranged next to the opposing ground plate with a predetermined gap from the opposing ground plate ,
The opposed ground plate and the non-opposed ground plate are connected via a switch (60) that switches between a state in which the opposed ground plate and the non-opposed ground plate are electrically connected and a state in which the opposed ground plate and the non-opposed ground plate are electrically disconnected. , antenna device. 2. The antenna device according to claim 1, wherein said opposing ground plane is rectangular or square. The opposing ground plate is rectangular,
The opposing ground plate and the non-facing ground plate are arranged side by side in the longitudinal direction of the opposing ground plate,
The switch has, as states, an OFF state in which the opposing ground plate and the non-opposing ground plate are not electrically connected, and an ON state in which the opposing ground plate and the non-opposing ground plate are electrically connected,
When the switch is in the off state, the ground plane has symmetry in the longitudinal direction viewed from the short-circuit portion,
2. The antenna device according to claim 1, wherein when said switch is in said ON state, said ground plane is asymmetrical in said longitudinal direction when viewed from said short-circuit portion. 4. The antenna device according to any one of claims 1 to 3 , wherein said switch is arranged at an edge portion of said ground plane. 5. The antenna device according to any one of claims 1 to 4 , wherein the switch is arranged at a node of the current. The non-opposing ground plate is divided into a plurality of small non-opposing ground plate portions (121, 122),
6. A polarization ratio control switch (61) for switching between an electrically connected state and an electrically disconnected state of the small non-opposing ground plane portions adjacent to each other is provided. The antenna device according to .

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