Unit Cell and Radio Lens

Abstract

This radio wave lens comprises a plurality of unit cells (1a) which are two-dimensionally arranged on a surface of a substrate intersecting with incoming radio waves. Each of the unit cells (1a) is provided with: a dielectric layer (2) in which the dielectric constant can be controlled from the outside; dielectric layers (3, 4) formed so as to sandwich the dielectric layer (2); a conductor layer (5) formed on a surface, of the dielectric layer (3), on the dielectric layer (2) side so as to be in contact with the dielectric layer (2); and a conductor layer (6) formed on a surface, of the dielectric layer (4), on the dielectric layer (2) side so as to be in contact with the dielectric layer (2).

Description

Radio wave lens

[0001] The present invention relates to a radio wave lens that controls the transmission intensity distribution or reflection intensity distribution of radio waves.

[0002] Millimeter wave and terahertz wave bands used in fifth-generation (5G) and sixth-generation (6G) mobile communication systems have a high degree of directionality and poor tracking. As a result, they are significantly affected by obstructions, resulting in significant degradation of communication quality in areas beyond the line of sight of the base station. This degradation in communication quality also poses a problem when an outdoor base station is used to extend coverage to indoor areas through a building's windows.

[0003] Therefore, in recent years, attention has been focused on a technology that uses metasurface technology, which can design the planar scattering characteristic distribution of incoming waves, to guide radio waves in a desired direction by attaching a film or the like with a lens function to window glass (see, for example, Patent Document 1 and Non-Patent Document 1). Figure 21 shows how radio waves from a base station 103 are reflected by an outdoor metasurface pattern 100 and guided to a mobile terminal 104a, and how radio waves are reflected by a metasurface pattern 100 attached to a window glass 105 and guided to an indoor mobile terminal 104b.

[0004] In Non-Patent Document 1, a film having a metal metasurface pattern 100 as shown in Figure 22 is attached to a window glass, and a distribution of radio wave transmission and reflection is formed on the window glass surface, thereby realizing a desired planar transmission intensity distribution 101 (binary distribution of 1 (transmission) and 0 (reflection)). In addition, in Patent Document 1, in order to realize a more efficient lens function, a binary transmission phase distribution 102 of 0 and π [rad] is formed by the metasurface pattern 100, thereby realizing a radio wave lens function.

[0005] Furthermore, dynamic control of the transmission intensity distribution or phase distribution of radio waves is also being considered in order to guide the radio waves so that they follow the constantly changing position of a mobile terminal. For example, the technology disclosed in Non-Patent Document 2 uses liquid crystal as a functional material and combines it with metasurface technology to achieve dynamic control of the transmission intensity of radio waves.

[0006] However, when using liquid crystal materials primarily used for optical displays in the millimeter wave or terahertz wave bands, which have longer wavelengths than light, the required liquid crystal thickness becomes too thick. For example, the technology disclosed in Non-Patent Document 2 uses a structure in which a liquid crystal layer is sandwiched between two metasurface resonators, and controls the transmission intensity of radio waves in the 400 GHz band by controlling the hybrid resonance mode between the layers by changing the dielectric constant of the liquid crystal layer. In this case, the liquid crystal layer is approximately 50 μm thick, which is much thicker than the liquid crystal layer thickness of optical displays (around 4 μm).

[0007] A thicker liquid crystal layer leads to problems such as higher drive voltage, slower response time, and incompatibility with existing optical display manufacturing processes. Furthermore, controlling the propagation direction of the incoming wave requires two-dimensional control of the intensity distribution. Achieving this control requires vertical and horizontal matrix control signal lines. However, control signal lines with components parallel to the electric field direction of the incoming wave impede the coupling between the metasurface resonator and the incoming wave, resulting in significant loss.

[0008] JP 2019-41138 A

[0009] Daisuke Kitayama, et al., “Transparent dynamic metasurface for a visually unaffected reconfigurable intelligent surface:controlling transmission / reflection and making a window into an RF lens”, Optics Express, vol.29, No.18, pp. 29292-29307, 2021Jun Yang, et al., “Electrically tunable liquid crystal terahertz device based on double-layer plasmonic “metamaterial”, Optics Express, vol.27, No.19, pp.27039-27045, 2019

[0010] The purpose of the present invention is to dynamically control the transmission intensity distribution or reflection intensity distribution of radio waves in the millimeter wave and terahertz wave bands using a dielectric layer made of a functional material with a thickness equivalent to that of the liquid crystal used in optical displays.

[0011] The radio wave lens of the present invention comprises a plurality of unit cells arranged two-dimensionally on a surface of a substrate that intersects with an incident radio wave, and each unit cell comprises: a first dielectric layer whose dielectric constant is externally controllable; second and third dielectric layers formed so as to sandwich the first dielectric layer; a first conductor layer formed on the surface of the second dielectric layer facing the first dielectric layer so as to be in contact with the first dielectric layer; and a second conductor layer formed on the surface of the third dielectric layer facing the first dielectric layer so as to be in contact with the first dielectric layer.

[0012] According to the present invention, by forming the unit cell of the radio wave lens into a laminated structure of the first, second, and third dielectric layers and the first and second conductor layers, it is possible to realize a large change in the resonance frequency of the resonator even with a change in the dielectric constant of the thin first dielectric layer, and it is possible to control the transmission intensity distribution or reflection intensity distribution of the radio wave and guide the radio wave in a desired direction.

[0013] FIGS. 1A and 1B are cross-sectional views illustrating a method for forming a capacitive component in a structure in which a functional material is sandwiched between two dielectric substrates. FIGS. 2A and 2B are diagrams illustrating the effect of changes in the dielectric constant of the functional material on the resonance characteristics of a resonator. FIG. 3 is a cross-sectional view of a unit cell of a radio wave lens according to a first embodiment of the present invention. FIG. 4 is a plan view of a unit cell of a radio wave lens according to a first embodiment of the present invention. FIG. 5 is a plan view showing the pattern of the conductor layers of the unit cell according to the first embodiment of the present invention. FIG. 6 is a plan view showing the pattern of the conductor layers of the unit cell according to the first embodiment of the present invention. FIG. 7 is a plan view of a unit cell of a radio wave lens according to a second embodiment of the present invention. FIG. 8 is a plan view showing the pattern of the conductor layers of the unit cell according to a second embodiment of the present invention. FIG. 9 is a plan view showing the pattern of the conductor layers of the unit cell according to the second embodiment of the present invention. FIG. 10 is a plan view of a radio wave lens according to a third embodiment of the present invention. FIG. 11 is a diagram illustrating a method for determining the state of a unit cell according to a third embodiment of the present invention. FIG. 12 is a diagram illustrating a method for determining the state of a unit cell according to a fourth embodiment of the present invention. FIG. 13 is a cross-sectional view of a unit cell according to a fifth embodiment of the present invention. FIG. 14 is a plan view of a unit cell according to the fifth embodiment of the present invention. FIG. 15 is a plan view showing the pattern of conductor layers and control signal lines of a unit cell according to the fifth embodiment of the present invention. FIG. 16 is a plan view showing the pattern of conductor layers and control signal lines of a unit cell according to the fifth embodiment of the present invention. FIG. 17 is a perspective view showing a model of a unit cell 1a used in an electromagnetic field analysis simulation. FIG. 18 is a diagram showing the transmitted wave intensity characteristics of a unit cell without a control signal line. FIG. 19 is a diagram showing the transmitted wave intensity characteristics of a unit cell when a control signal line made of copper is formed. FIG. 20 is a diagram showing the transmitted wave intensity characteristics of a unit cell when a control signal line made of ITO is formed. FIG. 21 is a diagram explaining an example of the use of a technology for guiding radio waves in a desired direction. FIG. 22 is a diagram explaining a conventional transmission intensity distribution type radio wave lens and a transmission phase distribution type radio wave lens.

[0014] [Principle of the invention] This invention proposes a structure in which a liquid crystal layer is sandwiched between two metasurface resonators, but in which a liquid crystal layer is sandwiched between the capacitive component forming portion of a single resonator structure, which allows for large changes in resonance characteristics even with changes in the dielectric constant of a thin liquid crystal layer.

[0015] In addition, the metasurface structure is constructed from two types of conductive materials, and the control signal line is formed from a material with a higher resistance than the part where the RF (Radio Frequency) signal is desired to flow. This makes it possible to efficiently control the planar transmission intensity distribution of radio waves, even if a control signal line with a component parallel to the electric field direction is formed.

[0016] [First Example] Consider using a metal resonator as a unit cell that constitutes a metasurface, which is a two-dimensional periodic structure. The structure of the resonator forms an inductive component L and a capacitive component C. In the present invention, the capacitive component C is changed by changing the dielectric constant of a functional material whose dielectric constant can be controlled externally. The resonant frequency f of the resonator can be controlled by changing the capacitive component C. ｒ It is possible to control the scattering characteristics of radio waves arriving at the metasurface.

[0017]

[0018] Possible methods for forming the capacitance component C include forming it between metals formed on one of the two dielectric substrates sandwiching the functional material, or forming it between metals formed on each of the two dielectric substrates. Fig. 1A is a cross-sectional view of a structure in which metal layers 203 and 204 are formed on one substrate 201 of two dielectric substrates 201 and 202 sandwiching a dielectric layer 200 made of a functional material. Fig. 1B is a cross-sectional view of a structure in which metal layers 205 and 206 are formed on each of the two dielectric substrates 201 and 202.

[0019] In the case of the structure of FIG. 1A, the capacitance component C formed between the metal layers 203 and 204 is the capacitance C formed through the dielectric substrates 201 and 202 whose dielectric constants do not change. Ｈ =C Ｈ１ +C Ｈ２ and a capacitance C formed via the dielectric layer 200 whose dielectric constant changes. ｖIn this case, the resonant frequency f ｒ is expressed as equation (2).

[0020]

[0021] According to equation (2), the capacitance C ｖ The resonance frequency f due to the change ｒ The change in capacitance C Ｈ Therefore, as shown in FIG. 2A, when the dielectric constant of the dielectric layer 200 is ε ｖ１ From ε ｖ２ Even if the temperature changes to , the resonance characteristics of the resonator do not change significantly.

[0022] On the other hand, in the case of the structure of FIG. 1B, the capacitance component C formed between the metal layers 205 and 206 is the capacitance C formed via the dielectric layer 200. ｖ and the resonant frequency f ｒ In the case of the structure of FIG. 1B, the dielectric constant of the dielectric layer 200 is ε ｖ１ From ε ｖ２ Therefore, even if the dielectric layer 200 is thin, the resonant frequency f ｒ can achieve a big change.

[0023]

[0024] Fig. 3 is a cross-sectional view of a unit cell of the radio wave lens of this embodiment, and Fig. 4 is a plan view of the unit cell. Fig. 4 shows a see-through view of the top surface of the unit cell. The unit cell 1a is a resonator whose resonance frequency changes depending on the capacitance component. It is composed of a dielectric layer 2 made of a functional material such as liquid crystal, two dielectric layers 3 and 4 made of, for example, glass, which are formed to sandwich the dielectric layer 2, a conductor layer 5 made of metal and formed on the surface of the dielectric layer 3 facing the dielectric layer 2 so as to be in contact with the dielectric layer 2, and a conductor layer 6 made of metal and formed on the surface of the dielectric layer 4 facing the dielectric layer 2 so as to be in contact with the dielectric layer 2.

[0025] FIG. 5 is a plan view showing the pattern of conductor layer 5, and FIG. 6 is a plan view showing the pattern of conductor layer 6. In this embodiment, the metasurface pattern is formed by conductor layers 5 and 6. The capacitance component of the resonator is formed in the overlapping portion (part 7 in FIG. 4) where the pattern of conductor layer 5 and the pattern of conductor layer 6 face each other with the dielectric layer 2 sandwiched therebetween. The unit cell 1a has a four-fold rotational symmetry structure with respect to the rotation axis (S in FIG. 4) perpendicular to the stacked structure in FIG. 3. This allows it to function as a radio wave lens regardless of the polarization of the incoming radio waves.

[0026] When radio waves (arriving waves) are incident from a direction intersecting the surface on which the metasurface pattern is formed (the plane of the paper in Figure 4), the arriving waves with frequencies near the resonant frequency of the unit cell 1a are reflected without passing through the unit cell 1a. On the other hand, the arriving waves in a frequency range other than the resonant frequency are transmitted through the unit cell 1a. By changing the permittivity of the dielectric layer 2 depending on the position of the unit cell 1a, i.e., by changing the resonant frequency of the unit cell 1a, it is possible to change the intensity distribution of the transmitted wave and the intensity distribution of the reflected wave near the resonant frequency. Changing the permittivity of the dielectric layer 2 requires a control signal line, which will be described later.

[0027] Second Example This example shows an example of a metasurface pattern different from that of the first example. Figure 7 is a plan view of a unit cell 1b of this example. As with Figure 4, Figure 7 shows a perspective view of the top surface of unit cell 1b. Figure 8 is a plan view showing the pattern of conductor layer 5, and Figure 9 is a plan view showing the pattern of conductor layer 6. Since the stacked structure of unit cell 1b is the same as that of unit cell 1a, the same reference numerals as those of unit cell 1a are used for each component of unit cell 1b. A metasurface pattern such as that of this example can achieve the same effects as those of the first example.

[0028] In the first and second embodiments, an alignment layer may be inserted between the dielectric layer 2 and the conductor layer 5 or between the dielectric layer 2 and the conductor layer 6.

[0029] In the first and second embodiments, the structure of the unit cell of the radio wave lens has been described, but by arranging unit cells 1a two-dimensionally on a substrate 11 made of a dielectric material such as glass, as shown in Fig. 10, a radio wave lens 10 can be realized. The substrate 11 is either the dielectric layer 3 or the dielectric layer 4.

[0030] 11 is a diagram for explaining a method for determining the state of each unit cell 1a of the radio wave lens 10. Let N (N is an integer of 2 or more) be the total number of unit cells 1a constituting the radio wave lens 10, and let P be the wave source of the incoming wave incident on the radio wave lens 10. １ , the receiving point where energy is to be guided through the radio wave lens 10 is P ２ , the position of the nth unit cell 1a is p ｎ (n is an integer from 1 to N), and P １ The distance from the point to an arbitrary reference point on the substrate 11 (the center point of the substrate 11 in the example of FIG. 11) is D １ , P ２ The distance from the reference point to ２ , P １ From p ｎ The distance to １ｎ , P ２ From p ｎ The distance to ２ｎ Receiving point P ２ The phase difference G of the radio wave due to the difference in the optical path length per unit cell ｎ is expressed as follows: G ｎ = 2π((d １ｎ -D １ ) + (d ２ｎ -D ２ )) / λ...(4)

[0031] Here, the phase difference G ｎ That is, the wave source P １ , the receiving point P ２ λ is the wavelength of the incoming wave. By controlling the transmission or reflection state of each unit cell 1a, the radio wave transmitted through the radio wave lens 10 is directed to the receiving point P ２ can be guided to.

[0032] For example, the phase difference G ｎThe n-th unit cell 1a located on the substrate 11 at a position where the remainder when dividing π by 2π is equal to or greater than 0 and less than π may be in a transmissive state with respect to the incoming wave, and the n-th unit cell 1a located at a position where the remainder is equal to or greater than 0 and less than 2π may be in a reflective state with respect to the incoming wave. Conversely, the n-th unit cell 1a located at a position where the remainder is equal to or greater than 0 and less than π may be in a reflective state, and the n-th unit cell 1a located at a position where the remainder is equal to or greater than π and less than 2π may be in a transmissive state.

[0033] Also, the distance D １ is calculated to be sufficiently long compared to the size of the radio wave lens 10, １ It is possible to determine the transmission state or reflection state of the unit cell 1a assuming a plane wave arriving from the direction of the distance D. ２ is calculated to be sufficiently long compared to the size of the radio wave lens 10, ２ It is possible to realize the function of deflecting the transmitted wave in the direction of the arrow.

[0034] [Fourth embodiment] In the third embodiment, the receiving point P ２ The wave is projected through the radio wave lens 10. １ In this embodiment, as shown in FIG. １ Receiving point P ２ When the transmission state or reflection state of each unit cell 1a is determined in the same manner as in the third embodiment, the reflected wave from the radio wave lens 10 is set at the reception point P ２ can be guided to.

[0035] In the third and fourth embodiments, the unit cells 1a are arranged on the substrate, but the unit cells 1b may be arranged instead.

[0036] [Fifth Embodiment] In the first to fourth embodiments, in order to change the state by changing the capacitance component of the unit cells 1a and 1b, it is necessary to apply a voltage to the region where the capacitance component is formed in order to change the dielectric constant of the dielectric layer 2.

[0037] Fig. 13 is a cross-sectional view of a structure in which the control signal lines 8 and 9 are arranged in the unit cell 1a described in the first to fourth embodiments, and Fig. 14 is a plan view of a structure in which the control signal lines 8 and 9 are arranged in the unit cell 1a. Fig. 15 is a plan view showing the pattern of the conductor layer 5 and the control signal line 8, and Fig. 16 is a plan view showing the pattern of the conductor layer 6 and the control signal line 9.

[0038] Control signal lines 8 and 9 made of a conductor such as metal or ITO (Indium Tin Oxide) are formed in the dielectric layers 3 and 4 and connected to the conductor layers 5 and 6. By applying a voltage between the conductor layers 5 and 6 via the control signal lines 8 and 9, a voltage is applied to the dielectric layer 2 in the region where a capacitance component is formed between the conductor layers 5 and 6. This allows the dielectric constant of the dielectric layer 2 to be changed by the voltage. The control signal lines 8 and 9 can be arranged in a similar manner in the case of the unit cell 1b.

[0039] In order to arbitrarily control the planar transmission intensity distribution or reflection intensity distribution of radio waves using a radio wave lens 10 in which unit cells 1a and 1b are arranged two-dimensionally as shown in Fig. 10, it is necessary to form the control signal lines 8 and 9 that apply voltage to each unit cell 1a and 1b in a matrix. If the control signal lines 8 and 9 are formed in a matrix, the control signal lines having components parallel to the electric field components of the incoming waves will inhibit the coupling of the incoming waves with the unit cells 1a and 1b, making it impossible to form the intended transmission intensity distribution.

[0040] Therefore, in this embodiment, the control signal lines 8 and 9 are formed from a conductive material having a higher resistance than the material of the conductor layers 5 and 6 that constitute the unit cells 1 a and 1 b. As a result, high-frequency radio waves that arrive at the radio wave lens are mainly coupled to the unit cells 1 a and 1 b formed from a low-resistance material, and are not coupled to the high-resistance control signal lines 8 and 9. Therefore, it becomes possible to arbitrarily control the planar transmission intensity distribution of the radio waves using the control signal lines 8 and 9.

[0041] The effects of this embodiment were confirmed by electromagnetic field analysis, and the results are shown below. FIG. 17 is a perspective view showing a model of unit cell 1a used in the electromagnetic field analysis simulation. Here, alkali-free glass was used as the material for dielectric layers 3 and 4, copper was used as the material for conductor layers 5 and 6, and copper or ITO was used as the material for control signal lines 8 and 9. The sheet resistance of the control signal lines 8 and 9 made of ITO is 10 Ω·□ or more. Furthermore, liquid crystal with a relative permittivity that changes over a range of 2.5 to 3.5 with respect to the applied voltage was used for dielectric layer 2.

[0042] Fig. 18 is a diagram showing the transmitted wave intensity characteristics of the unit cell 1a when the control signal lines 8 and 9 are not provided, Fig. 19 is a diagram showing the transmitted wave intensity characteristics of the unit cell 1a when the control signal lines 8 and 9 made of copper are provided, and Fig. 20 is a diagram showing the transmitted wave intensity characteristics of the unit cell 1a when the control signal lines 8 and 9 made of ITO are provided. The vertical axis of Figs. 18 to 20 indicates the transmitted wave intensity (S21). 300 in Figs. 18 to 20 indicates the relative dielectric constant ε of the dielectric layer 2. ｒ is 2.5, and 301 is the relative dielectric constant ε ｒ The graph shows the characteristics when the value is 3.5.

[0043] FIG. 18 shows the characteristics when the control signal lines 8 and 9 are not present, so the relative dielectric constant ε ｒ On the other hand, when the control signal lines 8 and 9 are made of the same copper as the conductor layers 5 and 6, the relative dielectric constant ε of the dielectric layer 2 changes depending on the voltage applied to the control signal lines 8 and 9. ｒ On the other hand, when the control signal lines 8 and 9 are made of high-resistance ITO, the relative dielectric constant ε of the dielectric layer 2 is ｒ Therefore, according to this embodiment, even when the control signal lines 8 and 9 are formed in a matrix, it is possible to control the transmitted wave intensity by the voltage applied to the control signal lines 8 and 9.

[0044] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0045] (Supplementary Note 1) A radio wave lens of the present invention comprises a plurality of unit cells arranged two-dimensionally on a surface of a substrate that intersects with an incident radio wave, and each unit cell comprises a first dielectric layer whose dielectric constant is externally controllable, second and third dielectric layers formed so as to sandwich the first dielectric layer therebetween, a first conductor layer formed on the surface of the second dielectric layer facing the first dielectric layer so as to be in contact with the first dielectric layer, and a second conductor layer formed on the surface of the third dielectric layer facing the first dielectric layer so as to be in contact with the first dielectric layer.

[0046] (Supplementary Note 2) In the radio wave lens described in Supplementary Note 1, each unit cell further includes a first control signal line formed in the second dielectric layer and connected to the first conductor layer, and a second control signal line formed in the third dielectric layer and connected to the second conductor layer.

[0047] (Supplementary Note 3) In the radio wave lens described in Supplementary Note 2, the transmission state or reflection state of each unit cell with respect to the incident radio wave is set by the voltages applied to the first and second control signal lines, based on the phase difference of the radio wave caused by the difference in optical path length for each unit cell at the receiving point where the radio wave that has passed through the radio wave lens or the radio wave that has been reflected by the radio wave lens arrives.

[0048] (Supplementary Note 4) In the radio wave lens according to Supplementary Note 3, the number of the unit cells constituting the radio wave lens is N (N is an integer of 2 or more), and the distance from the wave source of the radio wave incident on the radio wave lens to the reference point on the substrate is D １ , the distance from the receiving point to the reference point is D ２ , the distance from the wave source to the nth unit cell (n is an integer from 1 to N) is d １ｎ , the distance from the receiving point to the nth unit cell is d ２ｎ , the wavelength of the radio wave incident on the radio wave lens is λ, the phase difference of the radio wave that has passed through the n-th unit cell and reached the receiving point or the radio wave that has been reflected by the n-th unit cell and reached the receiving point is G ｎ = 2π((d １ｎ -D １ ) + (d ２ｎ -D ２ )) / λ, the phase difference G ｎThe n-th unit cell located at a position where the remainder when divided by 2π is equal to or greater than 0 and less than π is set to a first state, which is either a transmission state or a reflection state, with respect to the incident radio wave, and the n-th unit cell located at a position where the remainder is equal to or greater than π and less than 2π is set to a second state, which is different from the first state, which is either a transmission state or a reflection state with respect to the incident radio wave.

[0049] (Supplementary Note 5) In the radio wave lens described in any one of Supplementary Notes 2 to 4, the first and second control signal lines are made of a conductive material having a higher resistance than the material of the first and second conductor layers.

[0050] (Appendix 6) In the radio wave lens described in Appendix 5, the first dielectric layer is made of liquid crystal, the second and third dielectric layers are made of alkali-free glass, the first and second conductor layers are made of copper, and the first and second control signal lines are made of ITO.

[0051] (Supplementary Note 7) In the radio wave lens according to Supplementary Note 1, the first and second conductor layers have portions that face each other with the first dielectric layer sandwiched therebetween.

[0052] (Supplementary Note 8) In the radio wave lens described in Supplementary Note 1, the unit cell has a shape that is rotationally symmetric about a rotation axis that is perpendicular to the laminated structure of the first, second, and third dielectric layers and the first and second conductor layers.

[0053] The present invention can be applied to a technique for controlling the transmission intensity distribution or reflection intensity distribution of radio waves.

[0054] 1a, 1b... unit cell, 2, 3, 4... dielectric layer, 5, 6... conductor layer, 8, 9... control signal line, 10... radio wave lens, 11... substrate.

Claims

1. A first dielectric layer whose dielectric constant is externally controllable; second and third dielectric layers formed so as to sandwich the first dielectric layer therebetween; a first conductor layer formed on a surface of the second dielectric layer facing the first dielectric layer so as to be in contact with the first dielectric layer; a second conductor layer formed on the surface of the third dielectric layer facing the first dielectric layer so as to be in contact with the first dielectric layer.

2. 2. The unit cell of claim 1 , The unit cell is characterized in that the first and second conductor layers have different patterns in a plane perpendicular to the stacking direction of the layers constituting the unit cell.

3. 3. The unit cell according to claim 1 or 2, a unit cell characterized in that the first and second conductor layers are formed with a planar pattern perpendicular to the stacking direction of each layer so that, when the layers constituting the unit cell are viewed from above, a ring-shaped portion is present in the shape of the overlapping first and second conductor layers.

4. 4. The unit cell according to claim 1, The first and second conductor layers have portions that face each other with the first dielectric layer sandwiched therebetween.

5. 5. The unit cell according to claim 1, The unit cell is characterized in that the first dielectric layer is made of liquid crystal.

6. 6. The unit cell according to claim 1, The unit cell is characterized in that the first and second conductor layers have a planar pattern shape that is rotationally symmetric about a rotation axis that is parallel to the stacking direction of the layers that constitute the unit cell.

7. A radio wave lens characterized in that a plurality of unit cells described in any one of claims 1 to 6 are arranged two-dimensionally on the surface of a substrate that intersects with the incident radio waves.

8. 8. The radio wave lens according to claim 7, Each unit cell is a first control signal line formed in the second dielectric layer and connected to the first conductor layer; a second control signal line formed in the third dielectric layer and connected to the second conductor layer;

9. The radio wave lens according to claim 8, 10. A radio wave lens according to claim 9, wherein the first and second control signal lines are made of a conductive material having a higher resistance than the material of the first and second conductor layers.