WO2020208682A1 - Antenna device and communication apparatus - Google Patents

Abstract

An antenna device (1) is configured so as to be provided with: a conductive bottom board (11); an antenna (13) disposed, out of two surfaces (11a), (11b) of the bottom board (11), on the side of the surface (11a) on which radio waves are incident; and a dielectric permittivity variable unit (14) which is disposed between the bottom board (11) and the antenna (13) and in which the dielectric permittivity is varied in accordance with an incoming direction of the incident radio waves.

Description

Antenna device and communication device

The present invention relates to an antenna device and a communication device including a dielectric constant variable portion whose dielectric constant is variable according to the arrival direction of an incident radio wave.

The following Patent Document 1 discloses an RCS reduction device that reduces the radar cross section (RCS: Radar Cross Section) of a moving body.
In the RCS reduction device disclosed in Patent Document 1, the control device cancels the RCS from the RCS storage device based on the frequency of the radar wave detected by the radar detection device and the arrival direction of the radar wave. Information indicating each of the amplitude and phase of the radar wave required for the above is read out.
The control device disclosed in Patent Document 1 controls an amplitude phase controller that controls each of the amplitude and phase of the radar wave received by the antenna based on the read information.
Radar waves whose amplitude and phase are each controlled by the amplitude phase controller disclosed in Patent Document 1 are emitted from the antenna. The radar waves emitted from the antenna reduce the RCS.

Japanese Unexamined Patent Publication No. 2015-81787

In the RCS reduction device disclosed in Patent Document 1, RCS is reduced by radiating a radar wave for canceling RCS from the antenna.
However, there is a problem that the radar wave radiated from the antenna becomes an unnecessary wave in a direction other than the direction in which the RCS is reduced.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an antenna device and a communication device capable of reducing RCS without radiating radio waves for canceling RCS. ..

The antenna device according to the present invention is arranged between the conductive main plate, the antenna arranged on the side of the two surfaces of the main plate on which the incident radio wave hits, and the main plate and the antenna. It is provided with a dielectric constant variable portion in which the dielectric constant is variable according to the arrival direction of the incident radio wave.

According to the present invention, the antenna device is configured to include a dielectric constant variable portion which is arranged between the main plate and the antenna and whose dielectric constant is variable according to the arrival direction of the incident radio wave. Therefore, the antenna device according to the present invention can reduce the RCS without radiating radio waves for canceling the RCS.

It is a block diagram which shows the communication device including the antenna device 1 which concerns on Embodiment 1. FIG. It is a block diagram which shows the antenna device 1 which concerns on Embodiment 1. FIG. It is explanatory drawing which shows the arrival direction of the incident radio wave and the like. It is a side view which shows the positional relationship between the electric power half width region of the radio wave radiated from the antenna 13 of the antenna device 1 shown in FIG. 2 and the dielectric constant variable part 14. FIG. 5A is a side view showing the positional relationship between the power half-price range region of the radio wave radiated from the antenna 13 and the dielectric constant variable portion 14, and FIG. 5B is the power half-price width region of the radio wave radiated from the antenna 13. It is a top view which shows the positional relationship with the dielectric constant variable part 14. FIG. 6A is a side view showing the positional relationship between the power half-price range region of the radio wave radiated from the antenna 13 and the dielectric constant variable portion 14, and FIG. 6B is the power half-price width region of the radio wave radiated from the antenna 13. It is a top view which shows the positional relationship with the dielectric constant variable part 14. It is a block diagram which shows the antenna device 1 which concerns on Embodiment 2. FIG. It is an enlarged view which shows the main part of the dielectric constant variable part 30 included in the antenna device 1 which concerns on Embodiment 2. FIG. FIG. 9A is an explanatory view showing a discharge tube having a two-stage structure, and FIG. 9B is an explanatory view showing an approximate multilayer medium. FIG. 10A is an explanatory diagram showing a simulation result of the amplitude of the reflection coefficient, and FIG. 10B is an explanatory diagram showing a simulation result of the phase of the reflection coefficient. It is a block diagram which shows the antenna device 1 which concerns on Embodiment 3. It is a perspective view which shows the antenna device 1 which concerns on Embodiment 4. FIG. It is a block diagram which shows the main part of the antenna device 1 which concerns on Embodiment 5.

Hereinafter, in order to explain the present invention in more detail, a mode for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1.
FIG. 1 is a configuration diagram showing a communication device including the antenna device 1 according to the first embodiment.
In FIG. 1, the communication device includes an antenna device 1 that transmits a communication signal or receives a communication signal.

FIG. 2 is a configuration diagram showing the antenna device 1 according to the first embodiment.
As shown in FIG. 2, the antenna device 1 is arranged in the coordinate system indicated by the x-axis, y-axis, and z-axis.
In FIG. 2, the main plate 11 is a conductive plate that reflects incident radio waves.
The main plate 11 is arranged in the xy plane.
Of the two surfaces 11a and 11b of the main plate 11, the surface 11a is the surface on which the incident radio wave hits.
In the antenna device 1 shown in FIG. 2, the shape of the main plate 11 in the xy plane is a circle. However, this is only an example, and the shape of the main plate 11 in the xy plane may be, for example, a rectangle or an ellipse.

The antenna support member 12 is a member that supports the antenna 13 and is attached to the main plate 11.
The antenna support member 12 includes a support surface 12a for supporting the antenna 13 and a mounting portion 12b for the main plate 11.
Of the two surfaces 11a and 11b of the main plate 11, one end of the attachment portion 12b is attached to the main plate 11 so that the support surface 12a is arranged on the side of the surface 11a to which the incident radio wave hits.
In the antenna device 1 shown in FIG. 2, the mounting portion 12b of the antenna support member 12 is mounted on the main plate 11. However, this is only an example, and the attachment portion 12b may be attached to a member (not shown) other than the main plate 11.
The antenna 13 is arranged on the support surface 12a of the antenna support member 12, and has a plurality of antenna cells 13a for transmitting and receiving radio waves.
The plurality of antenna cells 13a have a function of radiating radio waves in addition to receiving incident radio waves. The radio wave radiated from the antenna cell 13a is not a radio wave for canceling the RCS, but a radio wave for transmitting a communication signal.
In the antenna device 1 shown in FIG. 2, the antenna cell 13a has a function of radiating radio waves. However, this is only an example, and the antenna cell 13a may not have a function of radiating radio waves.

The variable dielectric constant portion 14 includes a dielectric layer 14a containing a dielectric and a dielectric layer 14b containing a dielectric.
The variable dielectric constant portion 14 is arranged between the main plate 11 and the antenna 13 in the yz plane, and the dielectric constant is variable according to the arrival direction of the incident radio wave.
The dielectric layer 14a is realized by, for example, a glass tube, and the glass tube contains, for example, a powdery dielectric.
The dielectric layer 14b is realized by, for example, a glass tube, and the glass tube contains, for example, a powdery dielectric.
A rubber tube or the like is attached to the dielectric inlet / outlet 14c. The dielectric layer 14a is connected to the pump 23a via a rubber tube or the like attached to the dielectric inlet / outlet 14c.
A rubber tube or the like is attached to the dielectric inlet / outlet 14d. The dielectric layer 14b is connected to the pump 23b via a rubber tube or the like attached to the dielectric inlet / outlet 14d.
In the antenna device 1 shown in FIG. 2, the variable dielectric constant portion 14 has a two-layer structure including a dielectric layer 14a and a dielectric layer 14b. However, this is only an example, and the variable dielectric constant portion 14 may have a single-layer structure including only the dielectric layer 14a, or the variable dielectric constant portion 14 has three layers including three or more dielectric layers. It may have the above structure.

In the antenna device 1 shown in FIG. 2, the shape of the dielectric constant variable portion 14 in the xy plane is a ring shape.
The central portion of the ring in the variable dielectric constant portion 14 is not hit by the incident radio wave because the incident radio wave is blocked by the antenna 13. In the antenna device 1 shown in FIG. 2, in order to arrange the dielectric constant variable portion 14 only at a position where the incident radio wave is not blocked by the antenna 13, the shape of the dielectric constant variable portion 14 in the xy plane is ring-shaped. It has a shape.
However, this is only an example, and the shape of the dielectric constant variable portion 14 on the xy plane may be the same as the shape of the main plate 11 on the xy plane.

The direction detection device 21 is realized by, for example, a computer having a processor and a memory, respectively.
The direction detection device 21 detects the arrival direction of the incident radio wave and outputs the detected arrival direction to the arithmetic unit 22.
The arithmetic unit 22 is realized by, for example, a computer having a processor and a memory, respectively.
The arithmetic unit 22 calculates the reflectance coefficient of the incident radio wave on the multilayer surface including the dielectric constant variable portion 14 and the main plate 11 based on the arrival direction of the incident radio wave output from the direction detection device 21.
The arithmetic unit 22 outputs the calculated reflection coefficient of the incident radio wave to the adjusting device 23.

The adjusting device 23 includes a pump 23a and a pump 23b.
The adjusting device 23 adjusts the dielectric constant of the dielectric constant variable unit 14 based on the reflection coefficient calculated by the arithmetic unit 22.
Specifically, the adjusting device 23 calculates the dielectric constant ε _a of the dielectric layer 14a and the dielectric constant ε _b of the dielectric layer 14b, which can realize the reflection coefficient calculated by the arithmetic unit 22. ..
The adjusting device 23 controls the pump 23a so that the dielectric constant of the dielectric layer 14a becomes the calculated dielectric constant ε _a, and adjusts the density of the dielectric contained in the dielectric layer 14a.
The adjusting device 23 controls the pump 23b so that the dielectric constant of the dielectric layer 14b becomes the calculated dielectric constant ε _b, and adjusts the density of the dielectric contained in the dielectric layer 14b.
In the internal memory of the adjusting device 23, the relationship between the dielectric constant ε _a of the dielectric layer 14a and the density of the dielectric contained in the dielectric layer 14a, and the dielectric constant ε _b of the dielectric layer 14b and the dielectric The relationship with the density of the dielectric contained in the layer 14b is stored. The relationship between the dielectric constant ε _a of the dielectric layer 14a and the density of the dielectric contained in the dielectric layer 14a, and the dielectric constant ε _b of the dielectric layer 14b and the dielectric contained in the dielectric layer 14b. The relationship with the density of the antenna device 1 may be given from the outside of the antenna device 1.

The pump 23a is connected to the dielectric inlet / outlet 14c via a rubber tube or the like.
The pump 23a sweeps out the powdery dielectric stored in the container (not shown) to the dielectric layer 14a or the powdery dielectric from the dielectric layer 14a according to the control signal output from the adjusting device 23. Inhale.
The pump 23b is connected to the dielectric inlet / outlet 14d via a rubber tube or the like.
The pump 23b sweeps out the powdery dielectric stored in the container (not shown) to the dielectric layer 14b according to the control signal output from the adjusting device 23, or the powdery dielectric material from the dielectric layer 14b. Inhale.

Next, the operation of the antenna device 1 shown in FIG. 2 will be described.
The radar cross section σ, which is one of the indexes for evaluating the scattering phenomenon of radio waves, is expressed by the following equation (1).

In equation (1), E ⁱ is the incident field for the scatterer, and E ^s is the scattering field radiated by the current when the current is excited to the scatterer by the incident field E ⁱ . The antenna device 1 is a scatterer. R is the distance between the unillustrated source of the incident radio wave and the antenna device 1.

FIG. 3 is an explanatory diagram showing the arrival direction of the incident radio wave and the like.
In FIG. 3, the coordinate system indicated by the x-axis, y-axis, and z-axis is the same as the coordinate system shown in FIG.
Since the variable dielectric constant portion 14 shown in FIG. 2 is arranged on the xy plane, the normal direction n hat of the variable dielectric constant portion 14 is a direction parallel to the z-axis as shown in FIG. .. In the text of the specification, the symbol "^" cannot be added above the character n due to the electronic application, so it is written as "n hat".
The direction of arrival of the incident radio wave to the dielectric constant variable portion 14 is the direction in which the angle formed by the z-axis is + θ, and the reflection direction of the reflected radio wave by the dielectric constant variable portion 14 is the direction in which the angle formed by the z-axis is −θ. Is.
Since the angle between the parallel plane, which is the plane including the arrival direction and the reflection direction, and the x-axis is φ, the arrival direction of the incident radio wave is determined by θ and φ.
e ⁱ _|| hat, unit vector parallel component of the incoming direction of the incident wave, e ⁱ _⊥ hat, unit vector of the vertical component of the incoming direction of the incident wave, e ^r _|| hat, according to the dielectric constant changing unit 14 It is a unit vector of parallel components in the reflection direction of the reflected radio wave.

First, the direction detection device 21 detects θ and φ as the arrival direction of the incident radio wave. Since the process itself for detecting the arrival direction of the incident radio wave is a known technique, detailed description thereof will be omitted.
The direction detection device 21 outputs the detected arrival directions θ and φ to the arithmetic unit 22.
Computing device 22, coming from the direction detecting device 21 direction theta, receives the phi, arrival direction theta, based on the phi, the reflection coefficient of the incident radio wave of a multilayer surface comprising a dielectric constant changing unit 14 and the ground plane 11 R _{| |} , R _⊥ is calculated.
Hereinafter, the calculation processing of the reflection coefficients R _|| and R _⊥ by the arithmetic unit 22 will be specifically described.

First, the arithmetic unit 22 calculates the complex scattering field E ₁ ^S of the antenna 13 based on the arrival directions θ and φ of the incident radio wave. The complex scattering field E ₁ ^S of the antenna 13 is generated by the radio waves reflected by the antenna 13.
If the complex scattering field E ₁ ^S corresponding to the arrival directions θ and φ is recorded in the internal memory of the arithmetic unit 22, the arithmetic unit 22 will move from the internal memory the complex scattering field E corresponding to the arrival directions θ and φ. ₁ Read ^S.
The arithmetic unit 22 may calculate the complex scattering field E ₁ ^S corresponding to the arrival directions θ and φ by performing an electromagnetic field simulation or the like.

Table entire complex scattered field E ^S of the antenna device 1, as shown in the following equation (2), the complex scattered field E ₁ ^S antenna 13, by the complex scattered field E ₂ ^S in the dielectric constant changing unit 14 Will be done. The complex scattering field E ₂ ^S of the variable dielectric constant unit 14 is generated by the reflected radio wave of the variable dielectric constant unit 14.

If the whole of the complex scattered field E ^S is zero the antenna device 1 can eliminate the radiation of unnecessary reflected waves from the antenna device 1.
In order to make the entire complex scattering field E ^S of the antenna device 1 zero, the amplitude of the complex scattering field E ₂ ^S of the dielectric constant variable unit 14 is set to the same amplitude as the amplitude of the complex scattering field E ₁ ^S of the antenna 13. the phase of the complex scattered field E ₂ ^S, may be the complex scattered field E ₁ ^S phase and antiphase.

Assuming that an observation point (not shown) exists in the reflection direction shown in FIG. 3, the direction in which the observation point exists is s hat, and the distance from the antenna device 1 to the observation point is r, the complex scattering field E ₂ ^S is calculated by the following equation (3).

In equations (3) to (5), j is an imaginary unit, ω is an angular frequency, μ is a vacuum magnetic permeability, ε is a vacuum dielectric constant, η is a vacuum impedance, and k is a wave number. is there.
The respective integration ranges in A _e and _Am are the ranges of the surfaces on which the incident radio waves are reflected in the dielectric constant variable unit 14.

If the reflecting surface of the incident radio wave in the variable dielectric constant portion 14 is larger than the wavelength of the incident radio wave and has a smooth shape, _Ie in the equation (4) is expressed as the following equation (6). , _{M e} in the formula (5) is expressed by the following equation (7).

In the formulas (6) and (7), E _{2 ||} ⁱ is a directional component of the parallel plane shown in FIG. 3 in the incident field E ⁱ . Direction component parallel surface shown in FIG. 3 is a component in the direction indicated by e ⁱ _|| hat.
E 2 _⊥ ⁱ is a directional component of the plane of the incident field E ⁱ that is perpendicular to each of the parallel plane and the normal n hat shown in FIG. Direction component of the vertical plane respectively is the component in the direction indicated by e ⁱ _⊥ hat.
Reflection coefficient R _||, the reflection coefficient in the direction indicated by e ⁱ _|| hat in a multilayer surface comprising a dielectric constant changing unit 14 and the ground plane 11, the reflection coefficient R _⊥, and a dielectric constant changing unit 14 and the ground plane 11 a reflection coefficient in the direction indicated by e ⁱ _⊥ hat in a multi-layer surface.

The arithmetic unit 22 repeatedly calculates the complex scattering field E ₂ ^S shown in the equation (3) while adjusting the reflection coefficients R _|| and R _⊥ described in the equations (6) and (7), and the entire complex is calculated. Search for reflection coefficients R _|| and R _⊥ that give the complex scattering field E ₂ ^S where the scattering field E ^S becomes zero.
The arithmetic unit 22 outputs the searched reflection coefficients R _|| and R _⊥ to the adjusting device 23.

The adjusting device 23 acquires the reflection coefficients R _|| and R _⊥ output from the arithmetic unit 22.
Adjustment device 23, the obtained reflection coefficient R _||, as the dielectric constant of the dielectric constant changing unit 14 to realize the R _⊥ epsilon, and the dielectric constant epsilon _a dielectric layer 14a, and the dielectric constant epsilon _b of the dielectric layer 14b Is calculated.
Since the variable dielectric constant portion 14 has a two-layer structure including the dielectric layer 14a and the dielectric layer 14b, the multilayer surface including the variable dielectric constant portion 14 and the main plate 11 includes the dielectric layer 14a and the dielectric layer. It can be regarded as a multilayer medium of 14b and the main plate 11. The relationship between the reflectance coefficient and the dielectric constant of each layer in the multilayer medium is disclosed in, for example, Non-Patent Document 1 below.
Thus, the reflection coefficient R _||, and the dielectric constant of the dielectric layer 14a that realizes the R _⊥ epsilon _a, the reflection coefficient R _||, processing to calculate the dielectric constant of the dielectric layer 14b to achieve the R _⊥ epsilon _b itself Is a known technique, and therefore detailed description thereof will be omitted.
[Non-Patent Document 1] Yoshio Hosoya. “Radio Propagation Handbook.” Realize Science and Technology Center, Tokyo (1999): 65.

The adjusting device 23 controls the pump 23a so that the dielectric constant of the dielectric layer 14a becomes the calculated dielectric constant ε _a, and adjusts the density of the dielectric contained in the dielectric layer 14a.
Specifically, the adjusting device 23 acquires, for example, the density of the dielectric corresponding to the calculated dielectric constant ε _a from the internal memory.
The adjusting device 23 controls the pump 23a so that the density of the dielectric contained in the dielectric layer 14a becomes the density of the acquired dielectric.
The adjusting device 23 controls the pump 23b so that the dielectric constant of the dielectric layer 14b becomes the calculated dielectric constant ε _b, and adjusts the density of the dielectric contained in the dielectric layer 14b.
Specifically, the adjusting device 23 acquires, for example, the density of the dielectric corresponding to the calculated dielectric constant ε _b from the internal memory.
The adjusting device 23 controls the pump 23b so that the density of the dielectric contained in the dielectric layer 14b becomes the density of the acquired dielectric.

In the first embodiment described above, the antenna device 1 is configured to include a dielectric constant variable portion 14 which is arranged between the main plate 11 and the antenna 13 and whose dielectric constant is variable according to the arrival direction of the incident radio wave. did. Therefore, the antenna device 1 can reduce the RCS without radiating radio waves for canceling the RCS.

In the antenna device 1 shown in FIG. 2, the variable dielectric constant portion 14 is arranged between the main plate 11 and the antenna 13. Therefore, in the antenna device 1 shown in FIG. 2, as shown in FIG. 4, in a region where the power in the directivity direction of the radio wave radiated from the antenna 13 is at least half the value (hereinafter, referred to as “power half width region”). The variable dielectric constants 14 do not overlap.
FIG. 4 is a side view showing the positional relationship between the power half width region of the radio wave radiated from the antenna 13 of the antenna device 1 shown in FIG. 2 and the dielectric constant variable portion 14.
Here, the antenna 13 has a function of radiating radio waves.

When the variable dielectric constant portion 14 is arranged not between the main plate 11 and the antenna 13 but on the radiation source side of the incident radio wave from the antenna 13, the variable dielectric constant portion 14 is as shown in FIGS. 5A and 5B. Part of the power may overlap with the half-price range of power. When a part of the variable dielectric constant portion 14 overlaps with the half-price range of power, a part of the radio wave radiated from the antenna 13 is blocked by the variable dielectric constant portion 14, so that the radio wave is higher than that of the antenna device 1 shown in FIG. The radiation performance of the antenna deteriorates.
FIG. 5A is a side view showing the positional relationship between the power half width region of the radio wave radiated from the antenna 13 and the dielectric constant variable portion 14.
FIG. 5B is a top view showing the positional relationship between the power half width region of the radio wave radiated from the antenna 13 and the dielectric constant variable portion 14. The variable dielectric constant portion 14 shown in FIG. 5B is viewed from the + z direction.

If it is necessary to prevent deterioration of the radiation performance of the radio wave even if the dielectric constant variable unit 14 is arranged on the radiation source side of the incident radio wave from the antenna 13, as shown in FIGS. 6A and 6B, the dielectric constant variable unit 14 Must be located in an area that does not overlap the half-price range of power.
FIG. 6A is a side view showing the positional relationship between the power half width region of the radio wave radiated from the antenna 13 and the dielectric constant variable portion 14.
FIG. 6B is a top view showing the positional relationship between the power half width region of the radio wave radiated from the antenna 13 and the dielectric constant variable portion 14. The variable dielectric constant portion 14 shown in FIG. 6B is viewed from the + z direction.
In the antenna device 1 in which the variable dielectric constant portion 14 is arranged in a region that does not overlap with the half-price width region of the electric power, a part of the radio waves radiated from the antenna 13 is not blocked by the variable dielectric constant portion 14, so that FIG. Radio wave radiation performance equivalent to that of the antenna device 1 shown can be obtained.

Embodiment 2.
In the antenna device 1 shown in FIG. 2, the variable dielectric constant unit 14 incorporates a dielectric whose dielectric constant is variable according to the arrival direction of the incident radio wave.
In the second embodiment, the antenna device 1 in which the variable dielectric constant portion 30 includes the discharge tubes 30a and 30b will be described.

FIG. 7 is a configuration diagram showing the antenna device 1 according to the second embodiment. In FIG. 7, the same reference numerals as those in FIG. 2 indicate the same or corresponding parts, and thus the description thereof will be omitted.
FIG. 8 is an enlarged view showing a main part of the dielectric constant variable portion 30 included in the antenna device 1 according to the second embodiment. The main part of the variable dielectric constant portion 30 is a portion surrounded by a broken line in FIG. 7.
The communication device shown in FIG. 1 includes the antenna device 1 shown in FIG. 7.
The variable dielectric constant portion 30 includes a plurality of discharge tubes 30a, a plurality of discharge tubes 30b, an electrode 30c, and an electrode 30d.
The variable dielectric constant portion 30 is arranged between the main plate 11 and the antenna 13 in the yz plane, and the dielectric constant is variable according to the arrival direction of the incident radio wave.
The discharge tube 30a is arranged in a direction parallel to the y-axis in the xy plane, and is filled with gas.
The discharge tube 30b is arranged in a direction parallel to the x-axis in the xy plane, and is filled with gas.
An ionizing gas is used as the gas filled in each of the inside of the discharge pipe 30a and the inside of the discharge pipe 30b. Specifically, argon, xenon, a mixed gas of argon and xenon, or the like is used.

When a current is applied to the electrodes 30c and 30d of the discharge tube 30a by the adjusting device 31, the gas filled therein is ionized and the gas is changed to a plasma state.
When a current is applied to the electrodes 30c and 30d of the discharge tube 30b by the adjusting device 31, the gas filled therein is ionized and the gas is changed to a plasma state.
As the material of the discharge tubes 30a and 30b, for example, glass is used. The discharge tubes 30a and 30b may be made of a material other than glass as long as the gas can be sealed, but a material having a low dielectric loss tangent is more preferable.
The set of the electrode 30c and the electrode 30d is provided for each one discharge tube 30a, and is provided for each one discharge tube 30b. Alternatively, a pair of electrodes 30c and 30d is provided as an electrode common to all the discharge tubes 30a and all the discharge tubes 30b.

The adjusting device 31 adjusts the dielectric constant of the dielectric constant variable unit 30 based on the reflection coefficient calculated by the arithmetic unit 22.
Specifically, the adjusting device 31 calculates the dielectric constant of the plasma inside the discharge tubes 30a and 30b, respectively, based on the reflection coefficient calculated by the arithmetic unit 22.
The adjusting device 31 adjusts the currents applied to the electrodes 30c and 30d so that the calculated dielectric constants of the plasma can be obtained.

Next, the operation of the antenna device 1 shown in FIG. 7 will be described.
When the gas filled in the discharge tube 30a is ionized, it changes to a plasma state. As a parameter representing the electrical properties of the plasma, the plasma frequency omega _p, there is a collision frequency v _m. The plasma frequency omega _p and collision frequency v _m, are disclosed in the following Non-Patent Documents 2 and 3.
[Non-Patent Document 2]
R. J. Vidmar, “On the use of Atmospheric Pressure Plasmas as Electromagnetic Reflections and Absorbers,” IEEE Trans. Plasma Sci., Vol. 18, No. 4, 1990
[Non-Patent Document 3]
Francis F. Chen, Translated by Ijiro Uchida, "Introduction to Plasma Physics", Maruzen, 1977

Plasma frequency omega _p, the electrodes 30c, is determined by the electron density _{n e} generated by giving current to 30d.
The collision frequency v _m is the average number of times per second that free electrons disappear when they collide with other particles, and the collision frequency v _m is determined by the type of gas and the density of the gas. The movement of free electrons is determined by the applied voltage to the electrodes 30c and 30d.

Plasma frequency omega _p is represented by the following equation (8), the collision frequency v _m is expressed by the following equation (9).

In the formula (8), _me is the electron mass, e is the charge, _ne is the electron density, and ε ₀ is the permittivity of the vacuum.
In the formula (9), n _n is the particle density, v is the particle velocity, and σ is the equivalent cross-sectional area when the particles collide elastically. The “-” symbol above σv represents the temporal mean value.
The collision frequency v _m is increased by increasing the size or density of the gas particles.

Dielectric constant epsilon _r of the plasma, as shown in the following equation (10) is determined by the plasma frequency omega _p and collision frequency v _m.

Therefore, the dielectric constant ε _{r of the} plasma can be adjusted by changing either the type of gas, the density of the gas, or the current applied to the electrodes 30c and 30d.

When the arithmetic unit 22 receives the arrival directions θ and φ from the direction detection device 21, the arithmetic unit 22 has a multilayer surface including the dielectric constant variable portion 30 and the main plate 11 based on the arrival directions θ and φ, as in the first embodiment. Calculate the reflectance coefficients R _|| and R _⊥ of the incident radio waves.
The arithmetic unit 22 outputs the calculated reflection coefficients R _|| and R _⊥ to the adjusting device 31.

When the adjusting device 31 receives the reflection coefficients R _|| , R _⊥ from the arithmetic device 22, the adjusting device 31 is filled in the discharge tube 30a as the dielectric constant ε of the dielectric constant variable portion 30 that realizes the reflection coefficients R _|| , R _⊥. The permittivity ε _ra of the existing plasma and the permittivity ε _{rb of the} plasma filled in the discharge tube 30b are calculated.
Reflection coefficient R _||, and the dielectric constant of the plasma to achieve a R _⊥ epsilon _ra, the reflection coefficient R _||, since the process itself of calculating the dielectric constant epsilon _rb of the plasma to achieve a R _⊥ is a known technique , Detailed description is omitted.

Adjusting device 31, the dielectric constant epsilon _ra plasma filled in the discharge tube 30a is as a dielectric constant epsilon _r of the left-hand side of equation (10), the electronic plasma dielectric constant is epsilon _ra density n _e Is calculated.
Further, in the adjusting device 31, assuming that the permittivity ε _{rb of the} plasma filled in the discharge tube 30b is the permittivity ε _r on the left side of the equation (10), the density of electrons at which the permittivity of the plasma becomes ε _rb. to calculate the n _e.
Here, the type of gas filled in the discharge tube 30a and the type of gas filled in the discharge tube 30b are the same, and the density of the plasma filled in the discharge tube 30a and the discharge tube 30b It is assumed that the density of the charged plasma is the same. If a is the same type and the plasma density of the gas, and the electron density n _e of the plasma of the dielectric constant is epsilon _ra, the density n _e of electrons plasma dielectric constant is epsilon _rb, the same And.

The internal memory of the adjusting device 31, the electron density n _e and the electrode 30c, the relationship between the current applied to 30d are stored. Electron density n _e and the electrode 30c, the relationship between the current applied to 30d, or may be given from the outside of the antenna device 1.
Adjustment device 31, as the value of current for realizing the electron density n _e, acquires from the internal memory, the value of current corresponding to the electron density n _e.
The adjusting device 31 adjusts the dielectric constant ε of the dielectric constant variable unit 30 by controlling the value of the current applied to the electrodes 30c and 30d to be the value of the acquired current.

In the antenna device 1 shown in FIG. 7, the variable dielectric constant portion 30 includes a discharge tube 30a and a discharge tube 30b as a two-stage discharge tube as shown in FIG. 9A.
As shown in FIG. 9B, the pair of the two-stage discharge tube and the main plate 11 can be approximated to a multilayer medium including three glass portions, two plasmas, and one main plate 11.
FIG. 9A is an explanatory diagram showing a discharge tube having a two-stage structure, and FIG. 9B is an explanatory diagram showing an approximate multilayer medium.
For example, _assume that the permittivity ε _r of the three glass portions is 4.0, which corresponds to the permittivity of the glass. It is assumed that the thickness of the plasma is 5 mm and the thickness of the glass portion is 2 mm. However, the thickness of the glass portion of the portion where the discharge pipe 30a and the discharge pipe 30b face each other is 4 mm.
10GHz frequency of the incident wave is, as the direction of arrival of the incident wave is a normal direction n hat, each plasma frequency omega _p and collision frequency _{v m,} in the range of 5 ~ 30 GHz, by changing the increments of 5 GHz, Examine the amplitude and phase of the reflection coefficients R _|| and R _⊥ .

FIG. 10A is an explanatory diagram showing a simulation result of the amplitude of the reflection coefficient, and FIG. 10B is an explanatory diagram showing a simulation result of the phase of the reflection coefficient.
The horizontal axis in FIGS. 10A and 10B, is a plasma frequency omega _p, the vertical axis in FIGS. 10A and 10B are collision frequency _{v m.}
In the example of FIG. 9B, since the incident radio wave is incident so as to be orthogonal to the multilayer medium, the reflection coefficient R _|| and the reflection coefficient R _⊥ have the same value.
The simulation result of the amplitude of the reflection coefficient shown in FIG. 10A shows that the amplitude of the reflection coefficient can be adjusted in the range of about -10 to 0 dB.
The simulation result of the phase of the reflection coefficient shown in FIG. 10B shows that the phase of the reflection coefficient can be adjusted in the range of −180 to 180 degrees.
Therefore, if the amplitude of the complex scattering field E ₁ ^S of the antenna 13 is in the range of about -10 to 0 dB with respect to the amplitude of the complex scattering field E ₂ ^S of the dielectric constant variable portion 30, the complex scattering field of the antenna 13 It can be seen that the entire complex scattering field E ^S of the antenna device 1 can be set to zero regardless of the phase of E ₁ ^S.

In the second embodiment described above, when a current is applied to the electrodes 30c and 30d, the variable dielectric constant portion 30 ionizes the filled gas to change the gas into a plasma state. The antenna device 1 shown in FIG. 7 is configured so that the adjusting device 31 adjusts the dielectric constants ε _ra and ε _rb of the plasma by adjusting the currents applied to the electrodes 30c and 30d. Therefore, the antenna device 1 shown in FIG. 7 can reduce the RCS without radiating radio waves for canceling the RCS, similarly to the antenna device 1 shown in FIG.

Embodiment 3.
In the third embodiment, the antenna device 1 in which the adjusting device 40 adjusts the dielectric constants ε _ra and ε _rb of the plasma by changing the type of gas filled in the discharge tubes 30a and 30b will be described.

FIG. 11 is a configuration diagram showing the antenna device 1 according to the third embodiment. In FIG. 11, the same reference numerals as those in FIGS. 2 and 7 indicate the same or corresponding portions, and thus the description thereof will be omitted.
The communication device shown in FIG. 1 includes the antenna device 1 shown in FIG.
The variable dielectric constant portion 30 includes a plurality of discharge tubes 30a, a plurality of discharge tubes 30b, and electrodes 30c and 30d.
Each of the discharge pipe 30a and the discharge pipe 30b is connected to the pump 40a of the adjusting device 40 via a rubber tube or the like. In FIG. 11, the description of the rubber tube or the like connecting each of the discharge pipe 30a and the discharge pipe 30b to the pump 40a is omitted.

The adjusting device 40 includes a pump 40a.
The pump 40a is connected to N (N is an integer of 2 or more) gas reservoirs 41-1 to 41-N via a rubber tube or the like.
The pump 40a is connected to each of the discharge pipe 30a and the discharge pipe 30b via a rubber tube or the like.
The internal memory of the adjusting device 40 stores the relationship between the reflection coefficients R _|| and R _⊥ calculated by the arithmetic unit 22 and the type of gas. The relationship between the reflection coefficients R _|| , R _⊥ and the type of gas may be given from the outside of the antenna device 1.

The adjusting device 40 uses the pump 40a to suck the gas filled in each of the discharge pipe 30a and the discharge pipe 30b. The adjusting device 40 uses the pump 40a to discharge the sucked gas to the gas storages 41-1 to 41-N that store the same type of gas as the sucked gas. ..
The adjusting device 40 selects a gas corresponding to the reflection coefficients R _|| and R _⊥ calculated by the arithmetic unit 22 from among N types of gases. The adjusting device 40 sucks the selected gas from the gas reservoir 41-n storing the selected gas from the gas reservoirs 41-1 to 41-N by using the pump 40a. The adjusting device 40 uses the pump 40a to fill each of the discharge pipe 30a and the discharge pipe 30b with the sucked gas.

The gas reservoirs 41-1 to 41-N store different types of gas.
The gas reservoirs 41-1 to 41-N are connected to the pump 40a of the adjusting device 40 via a rubber tube or the like.

Next, the operation of the antenna device 1 shown in FIG. 11 will be described.
When the adjusting device 40 receives the reflection coefficients R _|| , R _⊥ from the arithmetic unit 22, the adjusting device 40 refers to the internal memory and among the N types of gases, the gas corresponding to the reflection coefficients R _|| , R _⊥. Select.
If the type of gas filled in each of the discharge pipe 30a and the discharge pipe 30b is different from the selected gas type, the adjusting device 40 uses the pump 40a to use the pump 40a, respectively, in the discharge pipe 30a and the discharge pipe 30b. Aspirate the gas filled in.
The adjusting device 40 uses the pump 40a to discharge the sucked gas to the gas reservoirs 41-1 to 41-N that store the same type of gas as the sucked gas. ..

Next, the adjusting device 40 sucks the selected gas from the gas reservoir 41-n storing the selected gas from the gas reservoirs 41-1 to 41-N by using the pump 40a.
The adjusting device 40 uses the pump 40a to fill each of the discharge pipe 30a and the discharge pipe 30b with the sucked gas.
Collision frequency v _m, in order to change the type of gas, the adjustment device 40, by changing the kind of gas, it is possible to adjust plasma permittivity epsilon _ra, the epsilon _rb.
Therefore, even in the antenna device 1 shown in FIG. 11, the RCS can be reduced without radiating radio waves for canceling the RCS, similarly to the antenna device 1 shown in FIG.

In the antenna device 1 shown in FIG. 11, the adjusting device 40 adjusts the dielectric constants ε _ra and ε _rb of the plasma by changing the type of gas. However, this is only an example, and the adjusting device 40 may adjust the dielectric constants ε _ra and ε _rb of the plasma by changing the density of the gas filled in the discharge tubes 30a and 30b.
Collision frequency v _m, in order to vary the density of the gas, the adjusting device 40, by varying the density of the gas, it is possible to adjust plasma permittivity epsilon _ra, the epsilon _rb.
The density of the gas filled in the discharge pipes 30a and 30b can be adjusted by the adjusting device 40 sucking the gas filled in the discharge pipes 30a and 30b using the pump 40a. ..
Further, the adjusting device 40 uses the pump 40a from the gas reservoirs 41-1 to 41-N that store the same type of gas as the gas filled in the discharge pipes 30a and 30b. And suck the gas. Then, the adjusting device 40 can adjust the density of the gas by filling the discharge pipes 30a and 30b with the sucked gas by using the pump 40a.

Also in the antenna device 1 shown in FIG. 11, the adjusting device 40 adjusts the dielectric constants ε _ra and ε _rb of the plasma by adjusting the current applied to the electrodes 30c and 30d in the same manner as the adjusting device 31 shown in FIG. You may do so.

Embodiment 4.
In the fourth embodiment, the antenna device 1 in which the variable dielectric constant unit 50 includes a plurality of variable dielectric constant cells 50a will be described.

FIG. 12 is a perspective view showing the antenna device 1 according to the fourth embodiment. In FIG. 12, the same reference numerals as those in FIGS. 2, 7 and 11 indicate the same or corresponding portions, and thus the description thereof will be omitted.
The communication device shown in FIG. 1 includes the antenna device 1 shown in FIG.
In FIG. 12, the shape of the antenna 13 is cylindrical for the sake of simplification of the drawing. As shown in FIG. 2, the antenna 13 has a structure in which a plurality of antenna cells 13a are provided, and the plurality of antenna cells 13a are arranged on a support surface 12a of the antenna support member 12. Therefore, the actual shape of the antenna 13 is not cylindrical.

The variable dielectric constant section 50 includes a plurality of variable dielectric constant cells 50a.
The dielectric constant of the variable dielectric constant cell 50a is variable according to the direction of arrival of the incident radio wave.
The variable dielectric constant cell 50a may include the dielectric layers 14a and 14b like the variable dielectric constant portion 14 shown in FIG. 2, and like the variable dielectric constant portion 30 shown in FIGS. 7 and 11. The discharge tubes 30a and 30b may be provided.

The shielded area calculation device 61 is realized by, for example, a computer having a processor and a memory, respectively.
The internal memory of the shielding area calculation device 61 stores shape data indicating the shape of the antenna 13 and position data indicating the positional relationship between the antenna 13 and the variable dielectric constant 50. The shape data and the position data may be given from the outside of the antenna device 1.
The shielding area calculation device 61 acquires the arrival direction of the incident radio wave from the direction detection device 21.
The shielding area calculation device 61 is a region in which the incident radio wave is shielded by the antenna 13 in the dielectric constant variable unit 50 based on the shape data, the position data, and the arrival direction of the incident radio wave, and the incident radio wave does not hit. The shielding area is calculated.
The shielding area calculation device 61 outputs data indicating the calculated shielding area to the arithmetic unit 62.

The arithmetic unit 62 is realized, for example, by a computer having a processor and a memory, respectively.
The arithmetic unit 62 selects one or more variable dielectric constant cells 50a arranged in an area other than the shielding area calculated by the shielding area calculation device 61 from the plurality of variable dielectric constant cells 50a.
The arithmetic unit 62 calculates the reflectance coefficients R _|| and R _⊥ of the incident radio waves on the multilayer surface including the selected variable dielectric constant cell 50a and the main plate 11 based on the arrival direction of the incident radio waves.
The arithmetic unit 62 outputs the calculated reflection coefficients R _|| and R _⊥ of the incident radio wave to the adjusting device 63.
If the configuration of the variable dielectric constant cell 50a is the same as that of the variable dielectric constant portion 14 shown in FIG. 2, the adjusting device 63 has a reflection coefficient calculated by the arithmetic unit 62, similarly to the adjusting device 23 shown in FIG. The permittivity of the selected variable permittivity cell 50a is adjusted based on R _|| and R _⊥ .
If the configuration of the variable dielectric constant cell 50a is the same as the configuration of the variable dielectric constant portion 30 shown in FIG. 7 or 11, the adjusting device 63 may be the adjusting device 31 shown in FIG. 7 or the adjusting device shown in FIG. Similarly to 40, the permittivity of the selected variable permittivity cell 50a is adjusted based on the reflection coefficients R _|| and R _⊥ calculated by the arithmetic unit 62.

Next, the operation of the antenna device 1 shown in FIG. 12 will be described.
The shielding area calculation device 61 acquires shape data indicating the shape of the antenna 13 and position data indicating the positional relationship between the antenna 13 and the variable dielectric constant 50 from the internal memory.
The shielding area calculation device 61 acquires the arrival direction of the incident radio wave from the direction detection device 21.
The shielding area calculation device 61 is a region in which the incident radio wave is shielded by the antenna 13 in the dielectric constant variable unit 50 based on the shape data, the position data, and the arrival direction of the incident radio wave, and the incident radio wave does not hit. The shielding area is calculated.
The shielding area calculation device 61 outputs data indicating the calculated shielding area to the arithmetic unit 62.
Since the process itself of calculating the shielded area not hit by the incident radio wave is a known technique, detailed description thereof will be omitted.

When the arithmetic unit 62 receives data indicating the shielding area from the shielding area calculation device 61, G (G is an integer of 1 or more) arranged in an area other than the shielding area from among the plurality of variable dielectric constant cells 50a. ) Number of variable dielectric constant cells 50a are selected.
The complex scattering field E ₂ ^S of the G variable dielectric constant cells 50a is expressed by the following equation (11).

In equation (11), E _2i ^S is the complex scattering field of the i-th variable permittivity cell 50a, and k in bold is the wave vector in the arrival direction. In the text of the specification, the characters cannot be written in bold because of the electronic application, so they are written as "k in bold".
Bold r _i is the position vector of the space in the center of the i-th dielectric constant variable cell 50a.
To zero the entire complex scattered field E ^S of the antenna device 1, the amplitude of the complex scattering field E ₂ ^S, the same amplitude as the amplitude of the complex scattering field E ₁ ^S antenna 13, the complex scattered field E ₂ ^S the phase may be the complex scattered field E ₁ ^S phase and antiphase.

The arithmetic unit 62 repeatedly calculates the complex scattering field E ₂ ^S shown in the equation (11) while adjusting the reflection coefficients R _|| and R _⊥ described in the equations (6) and (7), and the entire complex is calculated. Search for reflection coefficients R _|| and R _⊥ that give the complex scattering field E ₂ ^S where the scattering field E ^S becomes zero.
The arithmetic unit 62 outputs the searched reflection coefficients R _|| and R _⊥ to the adjusting device 63.

The adjusting device 63 acquires the reflection coefficients R _|| and R _⊥ output from the arithmetic unit 62.
If the configuration of the variable dielectric constant cell 50a is the same as the configuration of the variable dielectric constant portion 14 shown in FIG. 2, the adjusting device 63 has acquired reflection coefficients R _|| , R as in the adjusting device 23 shown in FIG. Based on _⊥ , the permittivity of the selected G variable permittivity cells 50a is adjusted.
If the configuration of the variable dielectric constant cell 50a is the same as the configuration of the variable dielectric constant portion 30 shown in FIG. 7 or 11, the adjusting device 63 may be the adjusting device 31 shown in FIG. 7 or the adjusting device 40 shown in FIG. In the same manner as in the above, the permittivity of the selected G variable permittivity cells 50a is adjusted based on the acquired reflection coefficients R _|| and R _⊥ .

In the fourth embodiment, the variable permittivity unit 50 includes a plurality of variable permittivity cells 50a whose permittivity is variable according to the arrival direction of the incident radio wave, and is based on the arrival direction of the incident radio wave. In the dielectric constant variable unit 50, a shielding area calculation device 61 is provided for calculating an area where the incident radio wave is shielded by the antenna 13 and the incident radio wave does not hit. Then, the arithmetic unit 62 selects one or more variable dielectric constant cells 50a arranged in a region other than the region calculated by the shielding region calculation device 61 from the plurality of variable dielectric constant cells 50a, and causes the incident. Based on the arrival direction of the radio wave, the reflectance coefficient of the incident radio wave on the multilayer surface including the selected variable dielectric constant cell 50a and the main plate 11 is calculated. Then, the antenna device 1 shown in FIG. 12 is configured so that the adjusting device 63 adjusts the dielectric constant of the selected dielectric constant variable cell 50a based on the reflection coefficient calculated by the arithmetic unit 62. Therefore, the antenna device 1 shown in FIG. 12 can reduce the RCS without emitting radio waves for canceling the RCS, similarly to the antenna device 1 shown in FIG. Further, the antenna device 1 shown in FIG. 12 can enhance the effect of reducing RCS as compared with the antenna device 1 shown in FIG. 2 when there is a shielded region not exposed to the incident radio wave.

Embodiment 5.
In the fifth embodiment, the antenna device 1 including the loss-reducing members 71 and 72 that suppress the reflection of the incident radio wave will be described.
FIG. 13 is a configuration diagram showing a main part of the antenna device 1 according to the fifth embodiment. In FIG. 13, the same reference numerals as those in FIG. 2 indicate the same or corresponding parts, and thus the description thereof will be omitted.
Although the description is omitted in the antenna device 1 shown in FIG. 13, the antenna device 1 includes a direction detection device 21, an arithmetic device 22, and an adjustment device 23, similarly to the antenna device 1 shown in FIG.
In the antenna device 1 shown in FIG. 13, the variable dielectric constant portion 14 has a single-layer structure. However, this is only an example, and the variable dielectric constant portion 14 may have a structure of two or more layers.
In the antenna device 1 shown in FIG. 13, the variable dielectric constant portion 14 has, for example, a dielectric layer 14a. However, this is only an example, and as shown in FIGS. 7 and 11, the variable dielectric constant portion 30 including the discharge tubes 30a and 30b may be used. Further, as shown in FIG. 12, the variable dielectric constant section 50 may include the variable dielectric constant cell 50a.

The loss-reducing members 71 and 72 are highly dielectric loss tangent members capable of suppressing reflection of incident radio waves, and are realized by, for example, a ceramic containing carbon.
The loss-reducing member 71 is arranged on the side of the reflecting surface on which the incident radio wave hits, out of the two surfaces of the variable dielectric constant portion 14.
The loss-reducing member 72 is arranged between the variable dielectric constant portion 14 and the main plate 11.
The antenna device 1 shown in FIG. 13 includes both a loss-loss member 71 and a loss-loss member 72. However, this is only an example, and the antenna device 1 may include only one of the loss-loss member 71 and the loss-loss member 72.

Since the antenna devices 1 of the first to fourth embodiments include the variable dielectric constant section 14, the variable dielectric constant section 30, or the variable dielectric constant section 50, the RCS can be performed without radiating radio waves for canceling the RCS. It can be reduced. However, when the discharge tube 30a, a large reflecting surface of the incident wave in the dielectric constant changing unit 30 comprising 30b, measures to increase the thickness of the plasma, or, it is necessary to apply measures such as raising the plasma frequency omega _p.
Since the antenna device 1 shown in FIG. 13 includes loss-reducing members 71 and 72 that suppress the reflection of the incident radio wave, the plasma frequency ω _p is increased even when the reflecting surface of the incident radio wave in the dielectric constant variable unit 30 is large. RCS can be reduced without taking any measures.

In the antenna devices 1 of the first to fifth embodiments, the adjusting device 23, the adjusting device 31, the adjusting device 40 or the adjusting device 63 (hereinafter referred to as “adjusting device 23 or the like”) has a dielectric constant of the dielectric constant variable unit 14. The permittivity of the variable permittivity section 30 or the permittivity of the variable permittivity section 50 (hereinafter referred to as "the permittivity of the variable permittivity section 14 and the like") is adjusted.
The adjusting device 23 or the like may adjust the dielectric constant of the dielectric constant variable unit 14 or the like in real time, but the adjusting device 23 or the like adjusts the dielectric constant of the dielectric constant variable unit 14 or the like at each preset time interval. May be adjusted.
Further, the adjusting device 23 or the like may adjust the dielectric constant of the dielectric constant variable unit 14 or the like each time the directivity direction of the antenna 13 is switched.

In the present invention, within the scope of the invention, it is possible to freely combine the embodiments, modify any component of each embodiment, or omit any component in each embodiment. ..

The present invention is suitable for an antenna device and a communication device including a dielectric constant variable portion in which the dielectric constant is variable according to the arrival direction of radio waves.

1 antenna device, 11 main plate, 11a, 11b surface, 12 antenna support member, 12a support surface, 12b mounting part, 13 antenna, 13a antenna cell, 14 variable permittivity part, 14a, 14b dielectric layer, 14c, 14d dielectric In / out, 21 direction detector, 22 arithmetic device, 23 adjustment device, 23a, 23b pump, 30 dielectric constant variable part, 30a discharge tube, 30b discharge tube, 30c, 30d electrode, 31 adjustment device, 40 adjustment device, 40a pump , 41-1 to 41-N gas storage, 50 dielectric constant variable part, 50a dielectric constant variable cell, 61 shielding area calculation device, 62 calculation device, 63 adjustment device, 71, 72 loss-reducing member.

Claims (12)

1. With a conductive base plate
   Of the two surfaces of the main plate, the antenna arranged on the side where the incident radio waves hit and
   An antenna device provided between the main plate and the antenna and having a dielectric constant variable portion whose dielectric constant is variable according to the arrival direction of the incident radio wave.
2. The variable dielectric constant is arranged on the radiation source side of the incident radio wave with respect to the antenna instead of being arranged between the main plate and the antenna.
   The antenna device according to claim 1, wherein the variable permittivity unit is arranged in a region that does not overlap with a region in which the electric power in the directivity direction of the radio wave radiated from the antenna is at least half the value.
3. The antenna device according to claim 1, further comprising an adjusting device for adjusting the dielectric constant of the variable dielectric constant portion according to the direction of arrival of the incident radio wave.
4. An arithmetic unit for calculating the reflection coefficient of the incident radio wave on a multilayer surface including the variable dielectric constant and the main plate based on the arrival direction of the incident radio wave is provided.
   The antenna device according to claim 3, wherein the adjusting device adjusts the dielectric constant of the dielectric constant variable portion based on the reflection coefficient calculated by the arithmetic unit.
5. The antenna device according to claim 4, further comprising a direction detection device that detects the arrival direction of the incident radio wave and outputs the detected arrival direction to the arithmetic unit.
6. The antenna device according to claim 1, wherein the variable dielectric constant includes a dielectric whose dielectric constant is variable according to the direction of arrival of the incident radio wave.
7. The variable dielectric constant includes a discharge tube in which when an electric current is applied to the electrode, the filled gas is ionized and the gas is changed to a plasma state.
   The antenna device according to claim 3, wherein the adjusting device adjusts the dielectric constant of the plasma by adjusting the current applied to the electrodes.
8. The variable dielectric constant includes a discharge tube in which when an electric current is applied to the electrode, the filled gas is ionized and the gas is changed to a plasma state.
   The antenna device according to claim 3, wherein the adjusting device adjusts the dielectric constant of the plasma by changing the type of gas filled in the discharge tube.
9. The variable dielectric constant includes a discharge tube in which when an electric current is applied to the electrode, the filled gas is ionized and the gas is changed to a plasma state.
   The antenna device according to claim 3, wherein the adjusting device adjusts the dielectric constant of the plasma by adjusting the density of the gas filled in the discharge tube.
10. The variable permittivity unit includes a plurality of variable permittivity cells whose permittivity is variable according to the arrival direction of the incident radio wave.
    A shielding area calculation device for calculating a region in which the incident radio wave is shielded by the antenna and the incident radio wave does not hit is provided in the dielectric constant variable portion based on the arrival direction of the incident radio wave.
    The computing device selects one or more variable permittivity cells arranged in a region other than the region calculated by the shielding region calculation device from the plurality of variable dielectric constant cells, and receives the incident radio wave. Based on the direction of arrival, the reflectance coefficient of the incident radio wave on the multilayer surface including the selected variable dielectric constant cell and the main plate is calculated.
    The antenna device according to claim 4, wherein the adjusting device adjusts the dielectric constant of the selected dielectric constant variable cell based on the reflection coefficient calculated by the arithmetic unit.
11. The antenna according to claim 1, wherein the antenna is arranged on the surface on the side where the antenna is arranged among the two surfaces of the main plate, and is provided with a loss-reducing member that suppresses reflection of the incident radio wave. apparatus.
12. A communication device including the antenna device according to any one of claims 1 to 11.

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