Antenna Lining and Antenna

Abstract

An antenna lining (13) of this invention is an antenna lining arranged on an inner wall of an antenna (10), and includes a metamaterial, and a dielectric that surrounds the metamaterial. Also, the antenna lining includes, sequentially from a side of the inner wall, a spacer layer (15) made of a dielectric, a metamaterial layer in which a metamaterial is arranged, and a cap layer (16) made of a dielectric. Thus, this invention can provide an antenna lining that can easily be manufactured and improve a gain and directivity of the antenna in a high-frequency band.

Description

Antenna Lining and Antenna

[0001] The present invention relates to an antenna lining and an antenna used for high-frequency communication.

[0002] A horn antenna is used in wireless communication or signal transmission in a variety of radar systems, particularly in signal transmission using a frequency band of 1 GHz or more. The horn antenna is formed by a waveguide, and the waveguide has a terminal spreading in a horn shape. The horn antenna implements an efficient radiating element having a high directivity and gain by the shape of its horn.

[0003] In horn antennas, an electromagnetic wave guided in the waveguide is converted into a free-space electromagnetic wave, and a free-space electromagnetic wave is converted into an electromagnetic wave guided in the waveguide. By the shape of the horn, a radiated wave can be directed in a specific direction and focused, and the directivity and gain of the antenna can thus be improved.

[0004] Recently, in the application of horn antennas, for example, in the application to a feed element of a reflector in a radar system or electromagnetic compatibility (EMC), a tapered ridge structure, a corrugation structure, and a flare structure are used on the inner surface of the horn to improve a reflection loss, impedance matching, and a radiation pattern by decreasing side lobes or increasing the band of the antenna (Non-patent literature 1 and 2). In addition, different types of mesh structures are designed inside the antenna. Also, different types of perforations and pillar structures are developed (Non-patent literature 3). The above-described structures provided inside the horn antenna are used for applications in a high-frequency band, including radio astronomy and satellite communication and also including sub-terahertz wireless communication that is rapidly developing recently.

[0005] On the other hand, a metamaterial is an artificial material not observed in nature. The metamaterial is formed by designed subwavelength cells organized like atoms in a physical material, and exhibits unique properties. The specific design (the shape, dimension, and structure of periodic metamaterial cells) of the metamaterial allows it to manipulate electromagnetic radiation by controlling various characteristics such as permeability, permittivity, and refractive index.

[0006] Metamaterials are used in various applications, focusing on interference of an electromagnetic wave in frequency bands from radio waves to optical spectra. Interference of a metamaterial with an electromagnetic wave is used in an absorber, a reflector, a lens, a phase shifter, a cloaking device, and the like. These devices are designed both as a passive structure that does not actively change the device characteristics and as an active structure that actively changes the device characteristics.

[0007] R. Elliott, "On the theory of corrugated plane surfaces," in Transactions of the IRE Professional Group on Antennas and Propagation, vol. 2, no. 2, pp. 71-81, April 1954, doi: 10.1109 / T-AP.1954.27975.C. Mentzer and L. Peters, "Properties of cutoff corrugated surfaces for corrugated horn design," in IEEE Transactions on Antennas and Propagation, vol. 22, no. 2, pp. 191-196, March 1974, doi: 10.1109 / TAP.1974.1140757.T. Hongnara, K. Schraml, S. Chaimool, P. Akkaraekthalin and D. Heberling, "Side-lobe reduction of horn antenna using circular patch mushroom-like EBG structure," 2016 German Microwave Conference (GeMiC), Bochum, Germany, 2016, pp. 413-416, doi: 10.1109 / GEMIC.2016.7461643.

[0008] As described above, in a low-frequency band, horn antennas having various structures such as corrugation and flare are used to improve the characteristics of a radiated signal. However, along with the increase of operating frequencies and size reduction of antennas, the above-described structures are difficult to manufacture in terms of accuracy in manufacturing various complex structures.

[0009] One of the most general structures used in horn antennas is a corrugation provided on the inner wall of a horn antenna. By the design of the corrugation or grooves along the inner surface of the horn, impedance matching and the radiation pattern of the antenna can be improved. An antenna of this type is used in an application in which very high directivity is required. However, the depth of a typical corrugation is λ / 2 to λ / 4 of the operating frequency, and in a 300-GHz band (λ = 1 mm), the depth needs to be correctly controlled within the range of 250 to 500 μm.

[0010] Also, a corrugation having a period shorter than the wavelength is required, and the linear distribution of the inner wall of the horn antenna is replaced with a more complex distribution such as an axial direction distribution or a Gaussian distribution. It is difficult to manufacture such a structure.

[0011] Another generally used structure is a ridge structure formed in the horn antenna. By the ridge structure, a gain can be improved in a wide-band operation, and a voltage standing wave ratio (VSWR) can be reduced. A ridge horn antenna having the ridge structure can radiate a linearly polarized wave with minimum cross-polarization. Furthermore, excitation of a higher-order mode in the aperture of the antenna can be suppressed. However, considering a small shape and high accuracy in the distribution of the ridge structure, it is difficult to correctly manufacture the ridge structure in a sub-THz band.

[0012] As described above, the ridge structure or the corrugation structure can be manufactured relatively easily in a relatively large antenna used in the low-frequency band, but cannot easily be manufactured in an antenna used in sub-THz and THz bands because of a problem of scalability.

[0013] Hence, in the antenna, it is difficult to improve the characteristics (gain, directivity, impedance matching, radiation pattern, and side lobe) in a high-frequency band such as a sub-THz or THz band.

[0014] In order to solve the above-described problem, an antenna lining according to the present invention is an antenna lining arranged on an inner wall of an antenna, comprising a metamaterial, and a dielectric that surrounds the metamaterial.

[0015] In addition, an antenna lining according to the present invention is an antenna lining arranged on an inner wall of an antenna, comprising, sequentially from a side of the inner wall, a spacer layer made of a dielectric, a metamaterial layer in which a metamaterial is arranged, and a cap layer made of a dielectric.

[0016] According to the present invention, it is possible to provide an antenna lining and an antenna which can easily be manufactured and improve a gain and directivity of the antenna in a high-frequency band.

[0017] Fig. 1A is a schematic view for explaining the configuration and operation of an antenna according to the first embodiment of the present invention;Fig. 1B is a schematic view for explaining the configuration and operation of a conventional antenna;Fig. 2A is a schematic view showing the configuration of an antenna lining and an antenna according to the first embodiment of the present invention;Fig. 2B is a schematic view showing the configuration of the antenna lining and the antenna according to the first embodiment of the present invention;Fig. 3 is a schematic view showing examples of the configuration of a metamaterial element in the antenna lining according to the first embodiment of the present invention;Fig. 4 is a schematic sectional view showing the configuration of the antenna lining according to the first embodiment of the present invention;Fig. 5A is a schematic view for explaining the configuration of the antenna lining according to the first embodiment of the present invention;Fig. 5B is a schematic view for explaining the configuration of the antenna lining according to the first embodiment of the present invention;Fig. 6 is a schematic view for explaining the configuration of the antenna lining according to the first embodiment of the present invention;Fig. 7 is a schematic view for explaining an example of the configuration of the antenna lining according to the first embodiment of the present invention;Fig. 8A is a view for explaining a method of manufacturing the antenna lining according to the first embodiment of the present invention;Fig. 8B is a view for explaining the method of manufacturing the antenna lining according to the first embodiment of the present invention;Fig. 9A is a schematic view showing the configuration of an antenna and an antenna according to the second embodiment of the present invention;Fig. 9B is a schematic view showing the configuration of the antenna and the antenna according to the second embodiment of the present invention; andFig. 10 is a view for explaining a method of manufacturing the antenna lining according to the second embodiment of the present invention.

[0018] <First Embodiment> An antenna lining and an antenna according to the first embodiment of the present invention will be described with reference to Figs. 1A to 5B.

[0019] <Configuration of Antenna Lining and Antenna> Fig. 1A is a schematic view of an antenna 10 according to this embodiment. The antenna 10 is a pyramidal horn antenna, and includes a waveguide 11 and a flare 12. A lining having a metasurface (to be referred to as a "metasurface lining" hereinafter) 13 is arranged on the inner wall of the flare 12. The metasurface lining corresponds to the "antenna lining" 13 according to the present invention. The "metasurface" is a surface with metamaterial elements 14 formed thereon.

[0020] An incident electromagnetic wave (EM wave) 1 propagates to the flare 12 of the antenna 10 via the waveguide. In the aperture of the flare 12 of the antenna 10, the electromagnetic wave is radiated in a form of a free-space electromagnetic wave that propagates through a space. The radiated electromagnetic wave includes a main beam 2 and side lobes 3.

[0021] For the sake of comparison, Fig. 1B shows a schematic view of a conventional antenna. In an antenna having no metasurface, radiation parameters such as the directivity and gain of the horn antenna are determined by the shape of a flare 120. The larger the angle of the flare 120 is, the wider the radiation pattern is, and the lower the directivity is. The smaller the angle of the flare 120 is, the narrower the radiation pattern is, and the higher the directivity is.

[0022] The size of the aperture of the flare 120 influences the gain of the antenna and the beam width. The larger the aperture is, the larger the gain is, and the narrower the beam width is. The length of the flare (horn) 120 influences impedance matching and radiation efficiency. The longer the flare (horn) 120 is, the more the impedance matching improves, and the higher the radiation efficiency is. If no metasurface exists, the side lobes 3 increase.

[0023] On the other hand, in the antenna 10 having the metasurface, the incident electromagnetic wave 1 propagates to the flare 12 of the horn antenna 10 via the waveguide 11, and the directivity and gain of the radiated beam are improved by the metasurface provided in the flare 12, and the side lobes 3 decrease (Fig. 1A).

[0024] The metasurface lining 13 is inserted into the flare 12 of the horn antenna (Fig. 2A) and attached to the inner surface (Fig. 2B). The metasurface lining 13 is designed in the shape of the horn antenna 10 having a pyramidal shape in accordance with the radiation characteristic of the antenna 10. The metasurface lining 13 is attached to the inner surface of the horn antenna 10 using a resin, an epoxy, a synthetic glue, or the like. The metasurface lining 13 is formed by four sections such that these are attached to the four inner walls of the flare 12.

[0025] The metasurface lining 13 includes a low-permittivity dielectric film made of an epoxy, a polymer, a resin, or the like, and the metamaterial elements 14 organized into a two-dimensional surface (metasurface) and arranged in the dielectric.

[0026] Fig. 3 shows examples of the shape of the resonant metamaterial element 14. The metamaterial element 14 is made of an electrically conductive material such as a metal, a high-conductivity polymer, or a conductive oxide, or a high-electric conductivity material such as a carbon nanotube or graphene. Alternatively, the metamaterial element 14 may be made of a dielectric material having a high permittivity, such as TiO2or BaTiO3. To obtain resonance, the dielectric material used for the metamaterial element 14 needs to have a permittivity higher by at least one or more orders of magnitude than that of an epoxy, a polymer, or a resin used as a dielectric film in the metasurface lining 13.

[0027] An electromagnetic wave can be controlled by using the two-dimensional flat metamaterial elements 14 in the metasurface lining 13. Also, for the metasurface lining 13, a three-dimensional structure, for example, various combinations of metamaterial elements 14 of multiple layers and vias for connecting the metamaterial elements 14 between the layers may be used. By the three-dimensional structure, generated resonance or interference with an electromagnetic wave can be controlled more correctly.

[0028] The design (selection) guideline of the metamaterial element 14 is based on a condition that causes the main body of the metamaterial element 14 to couple with an external electric field or magnetic field radiated from the horn antenna 10. In this embodiment, the size, the shape, and the period of the metamaterial elements 14 are selected such that a desired operating frequency range in a millimeter-wave band can be implemented. To implement excitation of resonance of the metamaterial elements 14, the size of the metamaterial element 14 is less than λ / 2 of the operating frequency that is 30 to 500 GHz. The metamaterial element 14 couples with at least one of an electric field component and a magnetic field component of the incident electromagnetic wave. To generate resonance on both the E surface and the H surface of the horn antenna 10, cells of different types may be used in different parts of the metasurface lining 13.

[0029] Fig. 4 shows the configuration of the metasurface lining 13 and the vicinity of the inner wall of the antenna 10. The metasurface lining 13 is attached to the inner wall of the antenna 10 (the flare 12) via a fixing material 17.

[0030] The metasurface lining 13 includes a spacer layer 15, a metamaterial layer in which the metamaterial elements 14 are arranged, and a cap layer 16 sequentially from the antenna inner wall side.

[0031] The metamaterial layer is formed by a single-layer or multiple-layer metasurface or a three-dimensional structure. In the metasurface or the three-dimensional structure, the metamaterial elements 14 made of a metal or a dielectric are arranged. Parameters such as the number of layers and the shape of the metasurface are arbitrarily selected based on the desired characteristics of a metasurface lining device.

[0032] The spacer layer 15 is a film made of a dielectric such as an epoxy, a polymer, or a resin. A dielectric such as polyimide (PI), SU-8, benzocyclobutene (BCB), or parylene may be used. The thickness of the dielectric spacer is adjusted based on a relative permittivity for controlling the surface impedance of the structure of the dielectric filling layer that interferes with an electromagnetic wave.

[0033] The cap layer 16 is made of a dielectric. As the dielectric, the above-described dielectric materials may be used. The same material as the dielectric spacer may be used, or a different material may be used. The cap layer 16 protects the metamaterial pattern from an environment or handling damage.

[0034] As the fixing material 17, a resin, an epoxy, a synthetic glue, or the like is used. The layer of the fixing material 17 may be included in the design of the metasurface lining 13 or calculation of the thickness of the dielectric spacer.

[0035] The function of the metasurface lining 13 is based on a metamaterial structure including an absorption layer and a reflecting layer shown in Fig. 4. If the electromagnetic wave guided in the horn antenna 10 is affected by the metamaterial structure, the side lobes of the radiated wave decrease, and the directivity of the antenna increases.

[0036] In the above-described configuration (Fig. 4), the inner wall of the horn antenna 10 (the flare 12) behaves as a reflecting layer. The reflecting layer is thicker than a minimum skin depth δ at an operating frequency indicated by equation (1).

[0037]

[0038] where ρ is the resistivity of the used material, μ0is the permeability (μ0= 4π× 10-7N・A-2) of a free space, μris the relative permeability of the used material, and f0is the frequency of the electromagnetic wave.

[0039] If it is assumed that a typical horn antenna is made of a metal, the metal thickness is larger than the skin depth by a few orders.

[0040] To control the directivity, the gain, and the side lobes of the horn antenna, the surface impedance of the inner wall of the horn antenna 10 needs to be adjusted. The impedance of the structure of the metasurface lining 13 is calculated based on reflection R and transmission T of a single metamaterial cell. The reflection R and the transmission T are calculated from a parameter S depending on the frequency in accordance with equations (2) and (3).

[0041]

[0042]

[0043] where S11(ω) is a reflection coefficient, and S21(ω) is a transmission coefficient.

[0044] Absorption A(ω) of the electromagnetic wave that passes through the antenna 10 is calculated by equation (4).

[0045]

[0046] Since the transmission of the electromagnetic wave is removed by the inner wall (reflecting layer) of the antenna 10, which is thicker than the skin depth indicated by equation (1), the value of transmission in the whole designed (calculated) frequency range is 0. Hence, equation (4) of absorption is simplified into equation (5).

[0047]

[0048] One of absorption and reflection occurs in accordance with equation (5).

[0049] Defining S21(ω) = 0, an effective impedance is calculated by equation (6) based on the reflection coefficient S11(ω).

[0050]

[0051] Based on the surface impedance of the metamaterial cell, the metasurface on which the characteristic of the metamaterial gradually changes is designed such that the impedance of the electromagnetic wave incident from the waveguide 11 of the antenna 10 and the impedance of the electromagnetic wave in the aperture match. In other words, the metasurface having a gradient in the change of the characteristic of the metamaterial is designed such that impedance matching is obtained between the connecting portion (boundary) between the waveguide 11 and the flare 12 of the antenna 10 and the aperture of the flare 12.

[0052] In a pyramidal horn antenna having a corrugation, which is an example of a conventional horn antenna, the capacitive surface on which the tangent component of a magnetic field parallel to the inner wall edge is zero reduces diffraction and removes a surface wave, thereby improving the directivity and the gain.

[0053] A surface of this type needs a corrugation having a height of λ0 / 4 to λ0 / 2, a corrugation having a width not more than λ0, and a corrugation having a thickness smaller than 1 / 10 the corrugation width. Here, λ0is a free-space wavelength. As described above, in the conventional horn antenna for the sub-THz band, a small structure needs to be formed with a very high aspect ratio.

[0054] According to this corrugation, the electric field distribution can be changed on the E surface. In propagation from the waveguide to the horn, a homogeneous electric field changes to the cosine of the electric field in the aperture of the horn antenna.

[0055] On the other hand, in the antenna 10 according to this embodiment, as shown in Figs. 5A and 5B, the size or shape of the metamaterial element 14 is changed, thereby changing the impedance in the metasurface lining 13 in the direction from the waveguide side to the aperture of the flare (indicated by arrows in the drawings). In other words, the impedance is changed in a direction of guiding the electromagnetic wave. The impedance may be changed gradually. The electric field distribution of the electromagnetic wave propagating in the antenna 10 can be changed by changing the parameters of the metamaterial element 14. The real part and the imaginary part of a relative wave impedance change. By the changes of the electric field and the relative wave impedance, the impedance between the input and the output of the flare 12 changes.

[0056] For example, as shown in Fig. 5B, the size of the metamaterial element 14 may be increased from the waveguide side to the aperture of the flare. Alternatively, the period of the arrangement of the metamaterial elements 14 may be decreased, or the shape of the metamaterial element 14 may be changed.

[0057] Impedance matching between the input and the output of the flare 12 of the horn antenna 10 depends on the relative surface impedance of the metamaterial element 14.

[0058] If the real part of the relative wave impedance is about 1, and the imaginary part is about 0 when averaged in the antenna operating frequency range, the input wave is absorbed. If the real part of the relative wave impedance is much larger than 1, and the imaginary part is larger than 0 in the same antenna operating frequency range, the input wave is completely reflected. Here, the value of the relative surface impedance may be taken into consideration.

[0059] Impedance matching is obtained by arranging the metasurface lining such that only the electric field distribution on the E surface of the antenna 10 is changed. To improve the characteristic of the antenna 10, the metasurface lining that interferes with a magnetic field H may be arranged on an inner wall perpendicular to the H surface of the antenna.

[0060] According to this embodiment, it is possible to provide an antenna having a high gain and high directivity in a high-frequency band, particularly, in a sub-terahertz or terahertz band. In addition, the operating band of the antenna can be increased, and the side lobes of the radiated electromagnetic wave can be decreased.

[0061] <First Example> An antenna lining and an antenna according to the first example of the present invention will be described with reference to Figs. 6 to 8B.

[0062] <Configuration of Antenna Lining and Antenna> Fig. 6 is a schematic view of the flare of the antenna according to this example.

[0063] In this example, a metasurface lining 13 is designed for a pyramidal horn antenna.

[0064] The metasurface lining 13 is designed divisionally for each inner wall of a flare 12 and attached to the flare 12 of the pyramidal horn antenna. As shown in Fig. 6, a set including four sheet-shaped metasurface linings (to be referred to as "metasurface lining sheets" hereinafter) 131 to 134 is necessary for the upper side, the lower side, the left side, and the right side of the antenna. The structure of metamaterial patterns on the metasurface lining sheets 131 to 134 depends on a desired antenna characteristic after the metasurface linings are attached.

[0065] Each of the metasurface lining sheets 131 to 134 includes metamaterial elements 14 of a single layer, which are configured in a periodical matrix.

[0066] The metamaterial elements 14 are formed on a spacer layer 15 (a resin, an epoxy, a polymer, or the like) having a thickness h. The thickness h is selected based on desired impedance matching.

[0067] The metamaterial elements 14 are covered with a cap layer 16 to protect the metamaterial pattern from an environment or handling damage.

[0068] In the metasurface lining 13, the metamaterial elements 14 of the single layer may be replaced with a multilayered structure, as shown in Fig. 7. This can improve the matching characteristic or an electromagnetic wave guided to the flare 12 of the horn antenna.

[0069] <Method of Manufacturing Antenna Lining> A method of manufacturing the antenna lining according to this example will be described below.

[0070] When forming the metasurface lining sheets 131 to 134, a carrier substrate 18 having a sacrificial layer is used. The carrier substrate 18 is a polished substrate of glass, silicon, a metal, or the like. When wet etching is used, the sacrificial layer is necessary in a step (to be described later) of separating a metasurface lining section from the carrier substrate 18.

[0071] First, a resin, an epoxy, or a polymer having a height h is stacked as a spacer layer 15 on the carrier substrate 18. Subsequently, the resin, epoxy, or polymer is cured at a temperature specific to the material.

[0072] Next, the periodical pattern of the metamaterial elements 14 is formed using a normal manufacturing process such as photolithography, electron beam vapor deposition, plating, or sputtering.

[0073] To further stack a layer of the metamaterial elements 14, the stacking and pattern formation steps are repeated.

[0074] Next, after formation of the layer of the metamaterial elements 14, a cap layer 16 is formed (Fig. 8A).

[0075] Next, a metasurface lining section is cut into a desired shape by a dicing apparatus.

[0076] Finally, the metasurface lining sheets (chips) 131 to 134 are separated from the carrier substrate 18 by mechanical peeling or wet etching (Fig. 8B). To separate the chips of the metasurface lining 13, another method of separating the chips from a substrate may be used.

[0077] Thus, the antenna lining according to this example is miniatured.

[0078] According to this example, it is possible to easily manufacture an antenna lining and an antenna improving a gain and directivity corresponding to a high frequency, particularly, a sub-terahertz or terahertz band.

[0079] <Second Embodiment> An antenna lining and an antenna according to the second embodiment of the present invention will be described with reference to Figs. 9A to 10.

[0080] <Configuration of Antenna Lining and Antenna> An antenna 20 according to this embodiment is designed for a conical horn antenna, as shown in Figs. 9A and 9B. The antenna 20 includes a cylindrical waveguide 21, and a flare 22 having a truncated cone shape. A metasurface lining 23 having a metasurface with metamaterial elements 24 formed thereon is arranged on the inner wall of the flare 22. The metasurface lining 23 is designed to improve the performance of the conical horn antenna.

[0081] The shape of the metasurface lining 23 is designed based on an inner diameter R1 of the bottom surface of the flare 22 of the conical horn antenna, which has a truncated cone shape, and an inner diameter R2 at the distal end.

[0082] A flat metasurface lining sheet 231 is produced in a desired shape, cut, and rolled into a truncated cone shape, as shown in Fig. 10. As in the first embodiment, the rolled metasurface is inserted into the conical horn antenna, and attached to the surface by a resin or a glue.

[0083] In the cylindrical waveguide 21 functioning as a feed to the conical horn antenna, a circular single waveguide mode TE11is the dominant propagation mode. An electric field distribution and a surface impedance are changed by the metasurface lining 23, and the mode TE11of an input wave can be made to match a mode HE11of the radiated wave.

[0084] The radiated wave is a radiation pattern of high requirement for various applications to satellite communication or radar systems.

[0085] The pattern (the size, the period, the configuration, and the like) of the metamaterial elements 24 on the metasurface lining sheet is changed along the propagation direction, thereby impedance matching and electromagnetic wave conversion can be implemented.

[0086] According to this embodiment, it is possible to provide an antenna having a high gain and high directivity in a high-frequency band, particularly, in a sub-terahertz or terahertz band. In addition, the operating band of the antenna can be increased, and the side lobes of the radiated electromagnetic wave can be decreased.

[0087] Also, the antenna lining and the antenna can easily be manufactured.

[0088] <Third Embodiment> An antenna lining and an antenna according to the third embodiment of the present invention will be described below.

[0089] <Configuration of Antenna Lining and Antenna> The antenna according to this embodiment includes a waveguide and a flare, and the antenna lining (metasurface lining) is arranged on the inner wall of the flare, as described in the first or second embodiment. The antenna lining according to this embodiment has a function of an electromagnetic wave filter.

[0090] The operation principle of the antenna according to this embodiment is the same as that of a conventional patch antenna having a filter function at a low frequency. The additional filter function is introduced in designing the antenna.

[0091] The same structure (a metamaterial layer, a dielectric spacer layer including a resin for adhesion, a reflecting layer, and an antenna inner wall) as the basic structure of the metasurface lining shown in Fig. 4 is used.

[0092] The structure of a metamaterial element 14 such as the shape, the size, and the period is set in accordance with equation (5) such that absorption increases in a predetermined frequency band. In this case, the structure of the metamaterial element 14 is optimized such that the real part of a relative wave impedance is about 1, and the imaginary part is about 0 when averaged in the frequency band of absorption.

[0093] The metasurface lining according to this embodiment can be manufactured in the same way as the first or second embodiment.

[0094] According to this embodiment, it is possible to suppress radiation outside a band and improve bandwidth controllability and a high-frequency sensitivity by the metasurface lining filter. In addition, the antenna can easily be manufactured.

[0095] In this embodiment, concerning the configuration of the antenna lining and the antenna and the method of manufacturing the same, an example of the structure, the dimension, and the material of each constituent part has been described, but the present invention is not limited to this. The antenna lining and the antenna need only exhibit their functions and provide effects.

[0096] 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. For example, the third embodiment may be combined with the first or second embodiment.

[0097] 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 followings.

[0098] (Supplementary Note 1) There is provided an antenna lining arranged on an inner wall of an antenna, comprising a metamaterial, and a dielectric that surrounds the metamaterial.

[0099] (Supplementary Note 2) There is provided an antenna lining arranged on an inner wall of an antenna, comprising, sequentially from a side of the inner wall, a spacer layer made of a dielectric, a metamaterial layer in which a metamaterial is arranged, and a cap layer made of a dielectric.

[0100] (Supplementary Note 3) In the antenna lining according to Supplementary Note 1 or 2, a characteristic of the metamaterial changes in a direction of guiding an electromagnetic wave in the antenna.

[0101] (Supplementary Note 4) There is provided an antenna comprising an antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 14.

[0102] (Supplementary Note 5) In the antenna lining according to any one of Supplementary Notes 1 to 3, the antenna includes a waveguide and a flare connected to the waveguide, an electromagnetic wave enters the waveguide and is radiated from an aperture of the flare, and the characteristic of the metamaterial changes in a direction from an end portion of the flare on a side of the waveguide to the aperture.

[0103] (Supplementary Note 6) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Note 5, the antenna includes a waveguide and a flare connected to the waveguide, an electromagnetic wave enters the waveguide and is radiated from an aperture of the flare, and the antenna lining is configured such that an impedance of the electromagnetic wave in an end portion of the flare on a side of the waveguide matches an impedance of the electromagnetic wave in the aperture.

[0104] (Supplementary Note 7) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 and 6, the metamaterial has a subwavelength resonant structure, and a size of the metamaterial is λ / 2 of a wavelength of the electromagnetic wave guided in the antenna.

[0105] (Supplementary Note 8) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 7, the metamaterial couples with at least one of an electric field component and a magnetic field component of the electromagnetic wave guided in the antenna.

[0106] (Supplementary Note 9) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 8, the metamaterial is made of an electrically conductive material.

[0107] (Supplementary Note 10) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 9, the metamaterial is made of at least one of a metal, a conductive polymer, a carbon nanotube, and graphene.

[0108] (Supplementary Note 11) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 9, the metamaterial is made of a dielectric material having a permittivity higher than a permittivity of the dielectric.

[0109] (Supplementary Note 12) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 11, the dielectric is at least one material selected from the group consisting of a non-conductive insulating polymer, a resin, an epoxy, polyimide, benzocyclobutene, parylene, SU-8, and polyethylene.

[0110] (Supplementary Note 13) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 12, the antenna corresponds to one of a sub-terahertz band and a terahertz band.

[0111] (Supplementary Note 14) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 13, the antenna is one of a pyramidal horn antenna and a conical horn antenna.

[0112] (Supplementary Note 15) In the antenna lining according to any one of Supplementary Notes 1 to 3 or Supplementary Notes 5 to 14, the antenna lining has a function of an electromagnetic wave filter.

[0113] (Supplementary Note 16) There is provided a method of manufacturing an antenna lining including a spacer layer, a metamaterial element, and a cap layer, comprising a step of forming the spacer layer made of a dielectric on a carrier substrate including a sacrificial layer, a step of periodically forming the metamaterial element on the spacer layer, a step of stacking the cap layer made of a dielectric to surround the metamaterial element, a step of cutting the carrier substrate on which the spacer layer, the metamaterial element, and the cap layer are stacked into a desired shape, and a step of separating the antenna lining from the carrier substrate using the sacrificial layer.

[0114] (Supplementary Note 17) There is provided a method of manufacturing an antenna lining including a spacer layer, a metamaterial element, and a cap layer and attached to an inner wall of a flare of a conical horn antenna, comprising a step of forming the spacer layer made of a dielectric on a carrier substrate including a sacrificial layer, a step of periodically forming the metamaterial element on the spacer layer, a step of stacking the cap layer made of a dielectric to surround the metamaterial element, a step of separating, in a desired shape, a stacked structure formed by the spacer layer, the metamaterial element, and the cap layer from the carrier substrate using the sacrificial layer, and a step of rolling the stacked structure into a shape conforming to the inner wall of the flare of the conical horn antenna.

[0115] The present invention is related to an antenna lining and an antenna, and can be applied to communication systems, wireless communication, and a variety of radar systems in a high-frequency band, particularly, in a sub-terahertz band or a terahertz band.

[0116] 10...antenna 13...antenna lining (metasurface lining)

Claims

1. An antenna lining arranged on an inner wall of an antenna, comprising: 　　　　a metamaterial; and 　　　　a dielectric that surrounds the metamaterial.

2. An antenna lining arranged on an inner wall of an antenna, comprising: 　　　　sequentially from a side of the inner wall, a spacer layer made of a dielectric; 　　　　a metamaterial layer in which a metamaterial is arranged; and 　　　　a cap layer made of a dielectric.

3. The antenna lining according to claim 1 or 2, wherein a characteristic of the metamaterial changes in a direction of guiding an electromagnetic wave in the antenna.

4. An antenna comprising an antenna lining according to claim 1 or 2.

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