Lens Element

Abstract

A lens element (10) of this invention is a lens element that receives an incident electromagnetic wave and emits a fan beam, and includes a metamaterial, and an active element (133) connected to the metamaterial. Columns formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction. A voltage applied to the active element changes in the other direction for each column of the metamaterials to change a capacitance of the metamaterial, and the fan beam is radiated while spreading in a plane perpendicular to the other direction.　This invention can thus provide a lens element capable of generating a fan beam having a high parallelism with a simple configuration.

Description

Lens Element

[0001] The present invention relates to a lens element that generates a fan beam.

[0002] From the viewpoint of resolution or sensitivity, it is important to perform wireless communication, radar, and sensing in a high-frequency band such as a millimeter wave frequency band (30 to 500 GHz) (non-patent literature 1 and 2). Also, application in the millimeter wave frequency band is important in the medical field and the security field as well because of high sensitivity or safety to a human body (non-patent literature 3).

[0003] In these applications, a normally used cone beam includes a large quantity of scattering radiation, and it is difficult to obtain a high spatial contrast resolution. On the other hand, a fan beam with a fan shape reduces scattering of an electromagnetic wave, improves correctness of sensing, can therefore reduce possible errors, and can acquire high special contrast resolution.

[0004] On the other hand, in beam forming, individual radiated electromagnetic waves are coupled, and a beam having high directivity is formed. Here, by correctly adjusting the phases of signals that enter from different portions of an array, the beam can be radiated in a specific direction.

[0005] To optimize beam generation and operation in beam forming, many characteristics such as an insertion loss, an operation angle, an operation resolution, an operation speed, complexity, a bandwidth, a phase deviation, and a size are required.

[0006] As beam forming corresponding to millimeter waves satisfying these requirements, beam forming using a metamaterial has been researched and developed. The metamaterial has an artificial structure and is configured to acquire a property from a subwavelength cell to resemble the atomic structure of a material in the natural world. By a specific configuration of metamaterial cells, an electromagnetic wave can be manipulated at a desired frequency via control of various characteristics such as the reflectance, permeability, and permittivity of the material. The electromagnetic wave and the metamaterial interfere with each other based on characteristics formed by the shape and dimensions of the metamaterial, the configuration of a periodical cell, the structure of the metamaterial, and peripheral media (a substrate, air, and the like).

[0007] In a metamaterial beam former, in a transmission-type structure using a lens and a transparent array, subwavelength metamaterial cells are arranged in the aperture of a radiation element (for example, an antenna). In a reflection-type structure, a metal is arranged on the bottom surface of the beam former to reflect an incident wave. To actively operate a beam, a capacitance element such as a varactor diode or a transistor is loaded to the metamaterial cell. The phase of a transmitted wave or a reflected wave radiated from the antenna can be changed by adjusting the capacitance or changing the permeability or permittivity of the material.

[0008] [NPL 1] M. Caris, S. Stanko, S. Palm, R. Sommer, A. Wahlen and N. Pohl, "300 GHz radar for high resolution SAR and ISAR applications", 2015 16th International Radar Symposium (IRS), Dresden, Germany, 2015, pp. 577-580, doi: 10.1109 / IRS.2015.7226313. [NPL 2] L. Daniel and M. Gashinova, "Sub-THz Radar Imagery for Automotive Application", 2022 19th European Radar Conference (EuRAD), Milan, Italy, 2022, pp. 261-264, doi: 10.23919 / EuRAD54643.2022.9924931. [NPL 3] Stryker, S., Greenberg, J.A., McCall, S.J. et al. X-ray fan beam coded aperture transmission and diffraction imaging for fast material analysis. Sci Rep 11, 10585 (2021). https: / / doi.org / 10.1038 / s41598-021-90163-0.

[0009] As described above, to acquire sensing or imaging at a high resolution and a high sensitivity, fan beam generation and beam forming in a millimeter wave frequency band, for example, a high-frequency band such as 100 to 500 GHz are necessary.

[0010] If the above-described beam forming technique using an array device configured to adjust a phase is used in a high-frequency band such as a millimeter wave band, however, a chip (element) size that is large relative to an operating wavelength, a half-wavelength antenna pitch, a large signal loss in a phase shift circuit, and the like pose problems.

[0011] Also, in a radar device, since many antennas are needed to operate a beam operation angle in a wide range, an increase of the size of a phase array radar poses a problem.

[0012] If a device corresponding to a millimeter wave band at a low frequency is used in the medical field or security field, the low resolution and sensitivity pose problems.

[0013] In conventional fan beam formation, to obtain a very narrow beam, a collimator needs to be provided in addition to conventional components. Hence, an increase of the size and cost of the apparatus poses a problem.

[0014] It is difficult to implement fan beam generation or beam forming in a millimeter wave frequency band, for example, a high-frequency band such as 100 to 500 GHz using such a simple apparatus configuration.

[0015] In order to solve the above-described problems, according to the present invention, there is provided a lens element that receives an incident electromagnetic wave and emits a fan beam, comprising a metamaterial, and an active element connected to the metamaterial, wherein columns each formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction, a voltage applied to the active element changes in the other direction for each column of the metamaterials to change a capacitance of the metamaterial, and the fan beam is radiated while spreading in a plane perpendicular to the other direction.

[0016] There is also provided a lens element that receives an incident electromagnetic wave and emits a fan beam, comprising a spacer layer made of a dielectric, and a plurality of metamaterial cells periodically arranged on the spacer layer, wherein the metamaterial cell comprises a metamaterial element, a dielectric filling material that covers the metamaterial element, and an active element connected to the metamaterial cell, columns each formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction, a voltage applied to the active element changes in the other direction for each column of the metamaterials to change a capacitance of the metamaterial, and the fan beam is radiated while spreading in a plane perpendicular to the other direction.

[0017] According to the present invention, it is possible to provide a lens element capable of generating a fan beam having a high parallelism with a simple configuration. Also, it is possible to provide a lens element capable of operating a fan beam.

[0018] Fig. 1 is a schematic view showing a transmission / reception system using a lens element according to the first embodiment of the present invention;Fig. 2 is a schematic sectional view showing the configuration of the lens element according to the first embodiment of the present invention;Fig. 3 is a view for explaining the operation principle of the lens element according to the first embodiment of the present invention;Fig. 4 is a schematic view showing the configuration of a metamaterial cell in the lens element according to the first embodiment of the present invention;Fig. 5 is a schematic view showing an example of the configuration of the metamaterial cell in the lens element according to the first embodiment of the present invention;Fig. 6A is a view for explaining the operation principle of the lens element according to the first embodiment of the present invention;Fig. 6B is a view for explaining the operation principle of the lens element according to the first embodiment of the present invention;Fig. 7A is a view for explaining the operation principle of the lens element according to the first embodiment of the present invention;Fig. 7B is a view for explaining the operation principle of the lens element according to the first embodiment of the present invention;Fig. 7C is a view for explaining the operation principle of the lens element according to the first embodiment of the present invention;Fig. 8 is a view for explaining the effect of the lens element according to the first embodiment of the present invention;Fig. 9 is a view for explaining the effect of the lens element according to the first embodiment of the present invention;Fig. 10 is a view for explaining the effect of the lens element according to the first embodiment of the present invention;Fig. 11 is a schematic sectional view showing the configuration of a lens element according to the second embodiment of the present invention; andFig. 12 is a schematic view showing a transmission / reception system using the lens element according to the second embodiment of the present invention.

[0019] <First Embodiment> A lens element according to the first embodiment of the present invention will be described with reference to Figs. 1 to 10.

[0020] <Configuration of Lens Element> Fig. 1 shows a transmission / reception system using a lens element 10 according to this embodiment. A transmission / reception antenna Tx and a reception antenna Rx (not shown) are arranged adjacent to each other. A radiated wave 1 from the transmission / reception antenna Tx has a cone shape.

[0021] The lens element 10 is arranged near the front of Tx. The incident wave 1 from Tx is transmitted through the lens element 10. In the transmission, the shape of the incident cone beam is dynamically controlled to obtain a parallel fan beam strong in the x direction (in the x-y plane). The beam is not focused on the z direction (in the y-z plane). As a result, an output beam 2 is a beam (to be also referred to as a "fan beam" hereinafter) having a fan shape, as shown in Fig. 1.

[0022] Also, the lens element 10 includes a surface (to be referred to as a "metasurface" hereinafter) formed by a metamaterial, and has an active function. By the lens element 10, the fan beam 2 is generated, and the direction of wave propagation of the generated fan beam 2 can dynamically be controlled (beam forming) (an arrow in Fig. 1). As described above, the lens element 10 can implement both generation of the fan beam 2 and beam forming.

[0023] The lens element 10 is a fan lens element using a change of the characteristic of the metamaterial caused by a bias voltage. In other words, the lens element 10 is a reconfigurable fan lens element.

[0024] The lens element 10 is actively controlled by a change of the phase of metamaterial elements adjacent along the x direction.

[0025] The output fan beam is partially reflected by different targets during beam scanning (scanning). A change of a wave characteristic is received by the reception antenna Rx. For example, in an application to an automobile or a radar, Rx may be arranged adjacent to Tx.

[0026] In this embodiment, an example in which Rx is arranged adjacent to Tx has been described, but the present invention is not limited to this. For example, in an application to biomedicine or security, Rx may be arranged on the opposite side of Tx.

[0027] As shown in Fig. 2, the lens element 10 sequentially includes a spacer layer 12, a metamaterial layer formed by metamaterial cells 13 configured in a two-dimensional array, and a cap layer 14.

[0028] The lens element 10 is produced by stacking the spacer layer 12, the metamaterial layer, and the cap layer 14 on a carrier substrate 11 and then removing the carrier substrate 11.

[0029] The metamaterial layer may include a single layer or multiple layers.

[0030] The metamaterial cell 13 includes an electrically conductive metamaterial element 131, a dielectric filling material 132, and an active element 133 for controlling the lens element 10.

[0031] The metamaterial element 131 is a subwavelength resonant structure and resonates at a millimeter wave frequency designated in advance, for example, 100 to 500 GHz. The size of the resonant structure is smaller than λ / 2 of the wavelength of the operating electromagnetic wave. The metamaterial element 131 couples to the electric field component or magnetic field component of the incident electromagnetic wave.

[0032] The metamaterial element 131 is made of an electrically conductive material such as a metal, a high-conductivity polymer, a conductive oxide, a carbon nanotube, or graphene. The metamaterial element 131 may be made of a dielectric material having a permittivity higher than that of the dielectric filling material.

[0033] The dielectric filling material 132 is made of a non-conductive dielectric material. The dielectric filling material 132 may be made of a non-conductive insulating polymer, a resin, an epoxy, polyimide, benzocyclobutene, parylene, SU-8, polyethylene, or the like. As the dielectric filling material 132, a material having a low relative permittivity is preferably used.

[0034] The active element 133 is a varactor diode or a transistor. The active element 133 actively controls the lens element 10 based on a change of the capacitance of the metamaterial element 131. As the active element 133, a liquid crystal-, graphene-, or semiconductor-based device (a diode, a transistor, a resistor, or the like) may be used. The metamaterial element 131 need only control the metamaterial element 131 having a two-dimensional array structure.

[0035] The spacer layer 12 is made of a non-conductive dielectric material.

[0036] The cap layer 14 is made of a non-conductive dielectric material. The cap layer 14 is arranged to protect the lens element 10 including the metamaterial cells 13. The cap layer 14 may not be arranged.

[0037] <Operation Principle> The operation principle of the lens element 10 according to this embodiment will be described with reference to Figs. 3 to 7C.

[0038] Fig. 3 shows a side view (y-z plane) 20_1, a top view (x-y plane) 20_2, and a front view (x-z plane) 20_3 of a fan beam generated by the lens element 10.

[0039] According to the side view 20_1, in the y-z plane, the incident wave 1 from Tx, which is transmitted through the lens element 10, does not focus. According to the top view 20_2, in the x-y plane, an in-focus state is obtained, and the incident wave 1 is changed to the narrow beam 2 by strong collimation. According to the front view 20_3, the fan beam (combined beam) 2 is wide in the vertical plane (y-z plane) (for example, from 20° to 30°) and narrow in the horizontal plane (x-y plane) (for example, about 1°).

[0040] Fig. 4 is a schematic plan view of the active metamaterial cell 13, in which geometrical parameters and lumped capacitive elements are superimposed.

[0041] As described above, the metamaterial cell 13 includes the metamaterial element 131, the dielectric filling material 132, and the active element 133. The metamaterial element 131 is connected to a control line 134 connected to a bias line and a ground line 135 connected to ground.

[0042] A control signal applied to the metamaterial cell 13 via the control line 134 connected to the bias line changes the capacitance (to be referred to as a "lumped capacitance" hereinafter) of the lumped coupling element (active element) 133 and changes the transmission characteristics (the transmission intensity and the transmission phase).

[0043] The resonance frequency of the metamaterial cell 13 is calculated by

[0044]

[0045] where L is the equivalent inductance, and Ceqis the equivalent capacitance of the metamaterial cell 13. The equivalent inductance L is represented by

[0046]

[0047] where μ0is the permeability in a free space, a and b are the lengths of the sides of the metamaterial cell 13, representing the size of the metamaterial cell 13, and t is the thickness of the metal that forms the metamaterial cell 13. The equivalent capacitance Ceqis the sum of a capacitance (to be referred to as a "gap capacitance" hereinafter) Cgof the gap of the metamaterial element 131 and a lumped capacitance CLof the active element 133. The equivalent capacitance Ceqand the gap capacitance Cgare respectively given by

[0048]

[0049]

[0050] where ε0is the permittivity in the free space, εcis the relative permittivity of the material (for example, the dielectric filling material) that forms the gap, w is the width of a band-shaped structure that forms the metamaterial element 131, and g is the length (width) of the gap of the metamaterial element 131.

[0051] Ceqand L are proportional to the size of the metamaterial cell 13, and the resonance frequency is inversely proportional to the size.

[0052] The metamaterial cell 13 is arranged in a direction of coupling to an incident external electric field for inducing a current in the conductive metamaterial cell. Parameters such as the size, the shape, and the distance between cells, are optimized to implement coupling in the millimeter wave frequency band.

[0053] An example the configuration shown in Fig. 4 is used as the metamaterial cell 13 has been described. However, other configurations, for example, configuration examples 30_1 to 30_6 shown in Fig. 5 may be used. In Fig. 5, a hatched region indicates the metamaterial element 131. The metamaterial cell 13 has a gap g in the metamaterial element 131, and includes the control line 134 and the ground line 135 necessary for control of the active element 133. An example in which two-dimensional metamaterial elements are used has been described. Three-dimensional metamaterial elements may be used in a range where the operation principle is maintained.

[0054] Fig. 6A shows the configuration of the lens element 10 and the forms of control signals V1to Vnapplied to the lens element 10. In the lens element 10, to induce a phase change Δφ in transmission of the incident wave, the control signal is changed in the x direction for each column of the metamaterial cells 13. The control signals V1to Vnare applied.

[0055] Thus, in the x-z plane, columns each formed by metamaterials arranged periodically in the z direction are arranged periodically in the x direction, and a voltage applied to the active element connected to each metamaterial changes in the x direction for each column of metamaterials.

[0056] The control signal is applied such that a phase pattern is generated in the x direction based on the Fresnel zone plate (FZP) theory. The control signal is applied to change the capacitance of the lumped coupling active element 133 embedded in the metamaterial cell 13 in the lens element 10.

[0057] Fig. 6B shows examples of the focus pattern of the phase in the x direction, which is used to generate and operate a fan beam having a high parallelism. In Fig. 6B, a dotted line indicates the center of the metamaterial cell. In Fig. 6B, an arrow indicates a fan beam emitting direction. The generated phase pattern causes an incident beam to focus in the x-y plane and leaves the y-z plane without focusing.

[0058] By dynamic change of the control signal, the angle of the combined output fan beam is controlled, and a fan beam is formed (beam forming). The fan-shaped beam (fan beam) is operated in various directions along the x-y plane. For example, in Fig. 6B, a pattern 40_1 is a phase pattern formed at the control voltage V1= 0 V, and the fan beam is emitted at an operation angle of 0°. In patterns 40_2 to 40_4, as the control voltage increases, the fan beam is emitted at operation angles of 10°, 20°, and 40°.

[0059] The Fresnel zone plate is used as a focusing device in various spectral ranges. The operation principle is based on the interference of electromagnetic wave rays passing through a series of alternating transmitting and blocking circular regions. The thickness of the circular region in the radial direction decreases along with the increase of the radius.

[0060] When the thickness in the radial direction decreases along with the increase of the distance in the radial direction from the center of the pattern, the phase of a flat surface annular pattern generated successively to a previously generated flat surface annular pattern can be shifted by 180° with respect to the phase of the previously generated flat surface annular pattern. In other words, the phase difference between the annular patterns adjacent to each other is 180°.

[0061] This can shift the phase by 360° for every other annular pattern.

[0062] Normally, the FZP has a binary pattern (to be referred to as a "0-1 pattern" hereinafter) formed from "0" and "1", in which 0 is a blocking (opaque) region, and 1 is a transparent region. The radius of the annular zone (the length from the center of the annular zone) changes such that the path length difference between the regions is the wavelength λ of the operating frequency. The alternating 0-1 pattern of the zone plate is represented by two phase values having a π (180°) step corresponding to opaque and transparent. These are called phase-reversal FZPs. In both cases, incident waves perpendicularly enter the zone plate surface, are diffracted by the zone, and enhance each other at the focal point.

[0063] For a predetermined designed focal length f, a radius rnnecessary for each zone is given by

[0064]

[0065] The designed focal length f is longer than any path length difference in the device, and is given by

[0066]

[0067] The radius rnof the nth zone is given by

[0068]

[0069] Based on the binary plate zones, phase patterns of multiple steps can be designed. Here, the step of the 0-1 pattern may be converted into a larger number of steps. For example, as shown in Figs. 7A to 7C, it is possible to design patterns of two steps (0, π), four steps (0, π / 2, π, 3π / 2), and eight steps (0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, 7π / 4). Here, Figs. 7A, 7B and 7C show the patterns of two steps, four steps and eight steps, respectively. In Figs. 7A to 7C, tones of colors represent the steps of a phase. For example, in the 2-step configuration, black indicates "0" (block), and white indicates "1(π)" (transparent). In the 4- and 8-step configurations, the phase increases as the color becomes light.

[0070] The increase of the steps in the design can increase in the transmission efficiency of the lens element 10. The transmission efficiently increases to 40% in the 2-step configuration, and increases to 95% or more in the 8-step configuration.

[0071] As an ideal lens element, a lens element that does not have a phase step and continuously changes the phase is assumed. On the other hand, the lens element 10 has a plurality of discrete phase steps. When an electromagnetic wave passes through the lens element 10, the phase of the electromagnetic wave is assigned to one of the plurality of phase steps. This changes the phase and lowers the transmission efficiency of the lens element 10. Hence, as described above, if the phase steps are increased in the lens element 10, and the phase distribution of the lens element 10 is made close to the phase distribution in the ideal lens element, the transmission efficiency of the lens element can be improved.

[0072] To apply a circular pattern to the lens element, additional conversion is necessary. As shown in Figs. 7A to 7C, the circular patterns (the left views of Figs. 7A to 7C) are converted into a linear pattern (the right views of Figs. 7A to 7C) based on extraction of the phase distribution in a portion of the circular pattern along the radial direction. In the linear patterns shown in Figs. 7A to 7C, focusing is obtained (the beam is focused) in the lateral direction (a solid line arrow) in Figs. 7A to 7C, and focusing is not obtained (the beam is not focused) in the vertical direction (a dotted line arrow) in Figs. 7A to 7C. The extracted phase distribution is dynamically controlled by an active metasurface. This enables beam forming of a fan beam at various angles.

[0073] <Effects> The effects of the lens element 10 according to this embodiment will be described with reference to Figs. 8 to 10.

[0074] The lens element 10 is an active transmission type fan lens.

[0075] Fig. 8 is a schematic view of the simulated active metamaterial cell 13 adjusted to a 300-GHz frequency band. The dielectric used in the simulation was polyimide, and the relative permittivity εr= 2.86 and the tangent loss tanδ = 0.003 were set. These are typical values of a polyimide material in the millimeter wave band. A total thickness of 0.4 mm was used. The metallic pattern of the metamaterial element 131 was made of gold. The lumped capacitance was based on the values of integrated varactor diodes.

[0076] In Fig. 8, the metamaterial cell 13 is arranged horizontally. That is, the metamaterial cell 13 is arranged horizontally with respect to an incident electromagnetic wave that is radiated from port 1 and received by port 2. The metamaterial cell 13 is arranged along the x direction such that the electric field component of the electromagnetic wave couples to the metamaterial cell main body and induces resonance.

[0077] Concerning the active metamaterial cell 13 used in the lens element 10, a simulation was conducted by time-domain solution using the electric field component of the electromagnetic wave, a vertical incidence condition, and a periodical boundary condition along the x-axis.

[0078] Assuming that the period of the metamaterial cells 13 is constant, the shape parameters of the metamaterial such as a gap size, a cell size, and a width are optimized such that the phase greatly changes with respect to different capacitance values in the simulation within the range of transmission coefficients higher than -3 dB.

[0079] In the simulated metamaterial cell 13, the relative permittivity of polyimide is εr1= 2.86, and the relative permeability is μ = 1. The thickness of the substrate is ts= 0.4 mm. The tangent loss is tanδ = 0.002. The characteristics used in the simulation are based on the characteristics of commercially available products oriented to the millimeter wave frequency band.

[0080] The metamaterial element 131 is formed by a thin gold film having a thickness of 300 nm, and may be formed directly on a polyimide film using various commercially available thin films formed by a normal photolithography process and electron beam vapor deposition or magnetron sputtering.

[0081] As for the parameters of the metamaterial element 131, the gap size is g = 60 μm, the width of the band-shaped structure that forms the metamaterial element 131 is w = 30 μm, the period of the metamaterial cell 13 is px= py= 300 μm, the distance between the layers of the multilayered metamaterial beam former is 75 μm, and the thickness of each of the upper layer (surface layer) and the lower layer (bottom layer) of the additional dielectric is 50 μm. The total thickness is 0.4 mm. Furthermore, the size of an impedance patch is 70 × 80 μm.

[0082] The above-described parameters were optimized such that a high transmission phase shift of 360° or more occurred at 300 GHz, with a relatively high transmission coefficient S21, with respect to different values of the lumped capacitance in the lens element 10.

[0083] Fig. 9 shows the change of the whole transmission phase with respect to the change of the lumped capacitance in the metamaterial cell 13. Fig. 9 shows a calculation result for five layers of transmission-type metamaterial cells.

[0084] In the metamaterial cell 13, when the lumped capacitance is changed from 0 to 3 fF, the whole transmission phase changes from 130 to 120 degrees. The total change 370 degrees.

[0085] In the capacitance operation region, the metamaterial cell 13 is optimized to exhibit a phase change of about 360° (2π) in a transmission region higher than -3 dB.

[0086] By applying a control voltage signal to the embedded active element 133, the value of the capacitance can be changed such that the transmission phase of the metamaterial cell 13 is set like the above-described pattern of the FZP base of a plurality of steps.

[0087] A desired device characteristic can be obtained by correctly applying a control voltage to the optimized metamaterial cell 13 coupled to the lens element 10. As shown in Fig. 10, the radiated wave 1 from the antenna Tx is transmitted through the lens element 10 and changes to the collimated fan beam 2. In Fig. 10, regions indicated by different tone patterns represent phase steps induced by active control in the lens element 10.

[0088] The emitted fan beam 2 obtains an in-focus state in the x-y plane, changes to the narrow beam 2 by strong collimation, and changes to a beam spreading in a fan shape in the vertical plane (y-z plane) (an alternate long and short dashed line arrow in Fig. 10). Also, the emitted fan beam 2 can change the operation angle (beam forming) in the x-y plane (a dotted line arrow in Fig. 10). In Fig. 10, for example, a beam that perpendicularly enters the lens element 10 is directly transmitted and emitted without a phase change (a solid line arrow in Fig. 10).

[0089] In the lens element 10, to change the phase pattern of the incident electromagnetic wave to a desired phase pattern, the voltage applied to the active elements in each column formed by metamaterials arranged in the x-z plane is changed in the x direction, thereby changing the capacitance of the metamaterials. Accordingly, the fan beam focuses in the x-y plane and spreads to be radiated in the y-z plane.

[0090] According to the lens element of this embodiment, it is possible to generate a fan beam having a high parallelism and scan the fan beam in the x-y plane of the device.

[0091] <Second Embodiment> A lens element according to the second embodiment of the present invention will be described with reference to Figs. 11 and 12.

[0092] <Configuration of Lens Element> A lens element 50 according to this embodiment is a reflection-type lens element. In the lens element 50, a reflection-type metamaterial cell is used as a metamaterial cell 53.

[0093] As shown in Fig. 11, the lens element 50 sequentially includes a substrate 51, a reflecting layer 54, a dielectric spacer 52, and a metamaterial layer formed by the metamaterial cells 53.

[0094] The substrate 51 is a polished substrate of glass, silicon, a metal, or the like.

[0095] The reflecting layer 54 is made of a metal.

[0096] For the dielectric spacer 52, a dielectric material is used.

[0097] In the metamaterial layer, the metamaterial cells 53 are arranged in a two-dimensional array. The metamaterial cell 53 includes a metamaterial element, a dielectric filling material, and an active element for controlling the lens element 50.

[0098] The active element is a lumped active element such as a diode or a transistor. A control voltage signal is applied to the active element, thereby changing the capacitance of the metamaterial cell 53.

[0099] The lens element 50 may further include a cap layer on the metamaterial cell 53 layer. The metamaterial layer can be protected by the cap layer.

[0100] Fig. 12 shows the operation state of the lens element 50. An incident electromagnetic wave 1 from an antenna Tx is reflected by the lens element 50 in a predetermined direction. A change of a wave characteristic actively controlled is applied to reflection of the incident wave 1 from the lens element 50. As a result, a fan beam 3 having a high parallelism is formed along the x-axis of the lens element 50. On the other hand, the propagation direction of reflection is further controlled by a multistage (multistep) pattern of the lens element 50 (an arrow in Fig. 12). Like the device according to the first embodiment, a phase-controllable metamaterial cell is defined, and the phase of the reflected wave is controlled by the lumped capacitance element.

[0101] In application to security or biomedicine, the reflection-type device can perform more specific sensing or imaging from various planes or directions with respect to the position of a target.

[0102] According to the lens element of this embodiment, it is possible to generate a fan beam having a high parallelism and reflect and scan the fan beam in the x-y plane of the device.

[0103] In this embodiment, an example in which a substrate is provided has been described. However, the present invention is not limited to this, and the substrate may not be provided. In this case, on the lower surface of the reflecting layer, a dielectric layer is arranged in place of the substrate.

[0104] According to the lens element of the embodiments of the present invention, it is possible to implement the generation of a parallel fan beam and beam forming.

[0105] Accordingly, in the transmission / reception system, a conventionally used phased array antenna can be removed and replaced with a single transmission / reception antenna and a reconfigurable fan lens. As a result, a complex beam forming system is unnecessary, and the device and system can be made compact using a simple configuration.

[0106] In the embodiments of the present invention, the lens element may actively be controlled based on a change of the capacitance of the metamaterial element and a change of the relative permittivity of the material around the metamaterial element.

[0107] In the embodiments of the present invention, the characteristics of the active element may be controlled by a change of a control voltage, a control current, a control electric field, or the like. The characteristics of the active element may be changed by changing the transmission phase or reflection phase of the embedded metamaterial cell or changing the transmission intensity or reflection intensity.

[0108] In the embodiments of the present invention, examples of the structure, dimensions, material, and the like of the constituent parts have been described concerning the configuration and the manufacturing method of the lens element. However, the present invention is not limited to these, and the lens element need only exhibit its functions and provide effects.

[0109] Note that the present invention is not limited to the above-described embodiments, and it is obvious that a person who has normal knowledge in this field can make many modifications and combinations within the technical scope of the present invention.

[0110] Some or all of the above-described embodiments or examples can also be described as in the following supplementary notes but are not limited to the following.

[0111] (Supplementary Note 1) There is provided a lens element that receives an incident electromagnetic wave and emits a fan beam, comprising a metamaterial, and an active element connected to the metamaterial, wherein columns each formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction, a voltage applied to the active element changes in the other direction for each column of the metamaterials to change a capacitance of the metamaterial, and the fan beam is radiated while spreading in a plane perpendicular to the other direction.

[0112] (Supplementary Note 2) There is provided a lens element that receives an incident electromagnetic wave and emits a fan beam, comprising a spacer layer made of a dielectric, and a plurality of metamaterial cells periodically arranged on the spacer layer, wherein the metamaterial cell comprises a metamaterial element, a dielectric filling material that covers the metamaterial element, and an active element connected to the metamaterial cell, columns each formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction, a voltage applied to the active element changes in the other direction for each column of the metamaterials to change a capacitance of the metamaterial, and the fan beam is radiated while spreading in a plane perpendicular to the other direction.

[0113] (Supplementary Note 3) In the lens element according to Supplementary Note 1 or 2, a phase of the electromagnetic wave is changed by changing the capacitance.

[0114] (Supplementary Note 4) In the lens element according to Supplementary Note 1 or 2, the lens element further comprises a reflecting layer on a surface on an opposite side of an emitting surface.

[0115] (Supplementary Note 5) In the lens element according to Supplementary Note 3, a distribution pattern of the phase on an emitting surface is extracted from a portion of a circular pattern along a radial direction, the circular pattern is formed by N annular patterns arranged in the radial direction, and a difference between a phase of the annular pattern and a phase of an annular pattern adjacent to the annular pattern is 2π / N.

[0116] (Supplementary Note 6) In the lens element according to any one of Supplementary Notes 2 to 5, the metamaterial element has a gap, a capacitance of the active element is changed by a change of the voltage, and a capacitance generated from the gap changes.

[0117] (Supplementary Note 7) In the lens element according to any one of Supplementary Notes 1 to 6, the metamaterial has a subwavelength resonant structure, and a size of the metamaterial is λ / 2 of a wavelength of the electromagnetic wave.

[0118] (Supplementary Note 8) In the lens element according to any one of Supplementary Notes 1 to 7, the metamaterial couples to at least one of an electric field component and a magnetic field component of the electromagnetic wave.

[0119] (Supplementary Note 9) In the lens element according to any one of Supplementary Notes 1 to 8, the metamaterial is made of an electrically conductive material.

[0120] (Supplementary Note 10) In the lens element according to any one of Supplementary Notes 1 to 9, the metamaterial is made of at least one of a metal, a conductive polymer, a carbon nanotube, and graphene.

[0121] (Supplementary Note 11) In the lens element according to any one of Supplementary Notes 2 to 10, the metamaterial is made of a dielectric material having a permittivity higher than a permittivity of the dielectric.

[0122] (Supplementary Note 12) In the lens element according to any one of Supplementary Notes 1 to 11, the dielectric is at least one of a non-conductive insulating polymer, a resin, an epoxy, polyimide, benzocyclobutene, parylene, SU-8, and polyethylene.

[0123] (Supplementary Note 13) In the lens element according to any one of Supplementary Notes 1 to 12, the electromagnetic wave has a frequency in a millimeter wave band.

[0124] (Supplementary Note 14) In the lens element according to any one of Supplementary Notes 1 to 13, an emitting angle changes.

[0125] (Supplementary Note 15) There is also provided a lens element that receives an incident electromagnetic wave and emits a fan beam, comprising a metamaterial, and an active element connected to the metamaterial, wherein columns each formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction, a voltage applied to the active element for each column of the metamaterials changes, and a capacitance of the metamaterial changes such that a phase pattern of the electromagnetic wave changes to a desired phase pattern, and the fan beam is radiated while spreading in a plane perpendicular to the other direction.

[0126] The present invention is related to a lens element configured to generate a fan beam, and can be applied to wireless communication, a radar or sensing system, a medical field, a security field, and the like.

[0127] 10...lens element, 131...metamaterial element, 133...active element

Claims

1. A lens element that receives an incident electromagnetic wave and emits a fan beam, comprising: 　　　　a metamaterial; and 　　　　an active element connected to the metamaterial, 　　　　wherein columns each formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction, 　　　　a voltage applied to the active element changes in the other direction for each column of the metamaterials to change a capacitance of the metamaterial, and 　　　　the fan beam is radiated while spreading in a plane perpendicular to the other direction.

2. A lens element that receives an incident electromagnetic wave and emits a fan beam, comprising: 　　　　a spacer layer made of a dielectric; and 　　　　a plurality of metamaterial cells periodically arranged on the spacer layer, 　　　　wherein the metamaterial cell comprises: 　　　　a metamaterial element; 　　　　a dielectric filling material that covers the metamaterial element; and 　　　　an active element connected to the metamaterial cell, 　　　　columns each formed by the metamaterials arranged periodically in one direction are arranged periodically in another direction perpendicular to the one direction, 　　　　a voltage applied to the active element changes in the other direction for each column of the metamaterials to change a capacitance of the metamaterial, and 　　　　the fan beam is radiated while spreading in a plane perpendicular to the other direction.

3. The lens element according to claim 1 or 2, wherein a phase of the electromagnetic wave is changed by changing the capacitance.

4. The lens element according to claim 1 or 2, further comprising a reflecting layer on a surface on an opposite side of an emitting surface.

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