Planar Antenna

Abstract

To provide a planar antenna with shape transformation and recovery capabilities.SOLUTION: A planar antenna includes a dielectric layer having a first surface and a second surface opposite the first surface, an antenna conductor layer arranged on the first surface, and a ground conductor layer arranged on the second surface, the dielectric layer is composed primarily of a shape memory polymer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a planar antenna. [Background technology]

[0002] In antenna design, topology optimization techniques are applied to the design of radiator shapes that can efficiently transmit and receive signals over a wide frequency band or at multiple distant frequencies (see, for example, Non-Patent Document 1). For example, Non-Patent Document 2 discloses a helical antenna that can support two frequencies by incorporating the concept of an adaptive structure that changes its overall length by using a lattice structure with three structural safety points that is expandable in the radiator. Planar antennas are generally made of a single material that fills the substrate. For example, there is research that uses phase optimization to optimize the density of the substrate, improving antenna characteristics over a wide frequency band and reducing weight (see, for example, Non-Patent Document 3). For example, Non-Patent Document 4 reports that by applying phase optimization aimed at improving structural strength characteristics (minimizing compliance) to the substrate material of a planar antenna, a significant improvement in the antenna gain value can be obtained for materials with high dielectric tangents that are considered unsuitable for antennas. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] International Journal of Applied Electromagnetics and Mechanics 50 (2015) 1-4 IOS Press, Topology Optimization of Wideband ArrayAntenna for Microwave Energy Harvester

Outdoor Tool2

Outdoor Tools3

Outdoor Tools 4

[0004] However, there is a demand for a technology that allows a planar antenna to have a shape deformation and recovery function, but none of Non-Patent Documents 1 to 4 discloses such a technology.

[0005] Therefore, an object of the present invention is to provide a planar antenna having a shape deformation and recovery function. [Means for solving the problem]

[0006] A planar antenna according to one embodiment of the present invention comprises a dielectric layer having a first surface and a second surface opposite the first surface, an antenna conductor layer arranged on the first surface, and a ground conductor layer arranged on the second surface, wherein the dielectric layer is composed primarily of a shape memory polymer. Effect of the Invention

[0007] According to the above aspect, it is possible to provide a planar antenna having a shape deformation / recovery function. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a planar antenna according to an embodiment. [Diagram 2] FIG. 2 is a plan view of a planar antenna according to the embodiment. [Diagram 3]FIG. 2 is a diagram showing an example of a radiation pattern of a planar antenna according to the embodiment. [Figure 4] FIG. 2 is an explanatory diagram of topology optimization according to the embodiment. [Diagram 5] 1A to 1C are explanatory diagrams of design and analysis results of a comparative example. [Figure 6] FIG. 13 is an explanatory diagram of the design and analysis results of Example 1-2. [Figure 7] FIG. 11 is an explanatory diagram of the design and analysis results of the second embodiment. [Figure 8] FIG. 13 is an explanatory diagram of the design and analysis results of the third embodiment. [Figure 9] FIG. 13 is an explanatory diagram of the design and analysis results of the fourth embodiment. [Figure 10] FIG. 13 is an explanatory diagram of the design and analysis results of the fifth embodiment. [Figure 11] Front view of the experimental equipment. [Figure 12] Side view of the experimental equipment. [Figure 13] FIG. 4 is a plan view of a planar antenna according to an embodiment 1-2. [Figure 14] FIG. 4 is a perspective view showing a part of the radiation pattern of the planar antenna of Example 1-2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, an adaptive, highly rigid, and extremely lightweight planar antenna using a shape memory polymer (SMP) will be described as an example of a planar antenna. For example, the planar antenna of this embodiment is used in wireless energy transmission technology using microwaves or laser light, structural technology for large structures in space, and the like, toward the realization of Space Solar Power Systems (SSPS).

[0010] In the following description, expressions indicating relative or absolute arrangements, such as "parallel," "orthogonal," "center," and "coaxial," do not only mean such arrangements or states strictly, but also include arrangements or states in which there is a relative displacement with an angle or distance to the extent that the same function can be obtained with a tolerance. In the drawings used in the following description, the scale of each component may be appropriately changed to show each component with a recognizable size.

[0011] <Planar antenna> Fig. 1 is a perspective view of a planar antenna 1 according to an embodiment. Fig. 2 is a plan view of the planar antenna 1 according to an embodiment. Fig. 3 is a diagram showing an example of a radiation pattern of the planar antenna 1 according to an embodiment. 1 to 3, the planar antenna 1 includes a dielectric layer 2, an antenna conductor layer 3, and a ground conductor layer 4. For example, the planar antenna 1 has a planar shape when no heat or external force is acting on it, and is configured to be deformable when heat or an external force is acting on it.

[0012] Although not shown, the planar antenna 1 may further include a power feed line for feeding power to the antenna conductor layer 3. For example, the power feed line has one end (corresponding to a power feeding point) connected to the antenna conductor layer 3, and the other end serving as a power feeding end connected to an external device (not shown).

[0013] In the illustrated example, the planar antenna 1 has a rectangular shape in a planar view. For example, the planar antenna 1 is formed into a square plate shape in a planar view. Note that the planar view shape of the planar antenna 1 is not limited to the above and can be changed according to design specifications.

[0014] For example, the thickness of the planar antenna 1 is 10 mm or more and 90 mm or less. In the example shown in the figure, the thickness of the planar antenna 1 is about 30 mm. The thickness of the planar antenna 1 corresponds to the sum of the thickness of the dielectric layer 2, the thickness of the antenna conductor layer 3, and the thickness of the ground conductor layer 4. Note that the thickness of the planar antenna 1 is not limited to the above and can be changed according to the design specifications.

[0015] For example, the planar antenna 1 may have flexibility as a whole. For example, the planar antenna 1 may be configured so as to be curved as the side surface of a cylinder as a whole. For example, the planar antenna 1 may be configured so as to have flexible elastic properties so as to be foldable.

[0016] <Dielectric layer> The dielectric layer 2 is a layered substrate whose main component is a dielectric. The dielectric layer 2 has a role of keeping the distance between the antenna conductor layer 3 and the ground conductor layer 4 constant. The dielectric layer 2 has a first surface 11 and a second surface 12 opposite to the first surface 11. The first surface 11 corresponds to one surface of the dielectric layer 2 in the thickness direction. The second surface 12 corresponds to the other surface of the dielectric layer 2 in the thickness direction. The first surface 11 and the second surface 12 are parallel to each other.

[0017] The dielectric layer 2 is mainly composed of a shape memory polymer. The main component refers to a component that is 50 wt% or more based on the total mass of the material. For example, the dielectric layer 2 is preferably formed containing 80 wt% or more of the shape memory polymer, and more preferably formed containing 90 wt% or more of the shape memory polymer. The proportion of the shape memory polymer contained in the dielectric layer 2 is not limited to the above and can be changed according to the design specifications.

[0018] Shape memory polymers have the following characteristics (1) to (5). (1) It retains the shape formed at or above its melting point. (2) After molding, it becomes soft when heated above its glass transition temperature Tg. (3) Once the object becomes soft, its shape can be modified and adjusted. (4) If you cool it in its deformed state, the shape will be fixed. (5) When heated again, it softens and returns to its original shape.

[0019] For example, the shape memory polymer may be a polyurethane-based shape memory polymer. For example, the dielectric layer 2 is made of a polyurethane-based shape memory polymer. The material for forming the dielectric layer 2 is not limited to the above and can be changed according to the design specifications.

[0020] At least a portion of the dielectric layer 2 has a hollow structure 15. The hollow structure 15 is a structure formed in a state in which air is contained inside the dielectric layer 2, and corresponds to a hollowed-out portion of the dielectric layer 2. In a plan view, the dielectric layer 2 has a solid structure 16 at least in a portion overlapping with the antenna conductor layer 3. The solid structure 16 is a structure in which the dielectric layer 2 itself exists, and corresponds to a portion of the dielectric layer 2 other than the hollowed-out portion.

[0021] The dielectric layer 2 includes a first layer 21 having a first surface 11, a second layer 22 having a second surface 12, and an intermediate layer 23 disposed between the first layer 21 and the second layer 22. In a plan view, the first layer 21 and the second layer 22 are rectangular and of the same size. In a plan view, the intermediate layer 23 has a solid structure 16 at least in a portion that overlaps with the antenna conductor layer 3. In a plan view, the intermediate layer 23 has a hollow structure 15 in a portion that does not overlap with the antenna conductor layer 3.

[0022] In the illustrated example, the dielectric layer 2 is square in plan view. For example, each of the first layer 21 and the second layer 22 constituting the dielectric layer 2 is formed in a sheet shape that is square in plan view. For example, at least a part of the hollow structure 15 is disposed at a position that is four-fold symmetrical with the center of the dielectric layer 2 as the axis of symmetry.

[0023] The thickness of the dielectric layer 2 is 10 mm or more and 30 mm or less. The thickness of the dielectric layer 2 corresponds to the distance between the first surface 11 of the first layer 21 and the second surface 12 of the second layer 22. For example, the thickness of the dielectric layer 2 is more preferably 15 mm or more and 25 mm or less. The thickness of the dielectric layer 2 is not limited to the above and can be changed according to the design specifications as long as the planar antenna 1 can function as an antenna.

[0024] For example, the dielectric layer 2 is formed by a 3D printer using a filament of a shape memory polymer. For example, the dielectric layer 2 may be formed by laser sintering using a powder of a shape memory polymer. The method of forming the dielectric layer 2 is not limited to the above and can be changed according to the design specifications.

[0025] <Antenna conductor layer> The antenna conductor layer 3 has the role of converting radio waves irradiated from the outside into electric current, or converting a supplied electric current into radio waves that are radiated to the outside. The antenna conductor layer 3 is disposed on the first surface 11 of the dielectric layer 2. In a plan view, the antenna conductor layer 3 is disposed in the center of the first surface 11. In a plan view, the antenna conductor layer 3 has a rectangular shape smaller than the first layer 21.

[0026] For example, the antenna conductor layer 3 is formed of a metal (an example of a conductor) such as copper. The antenna conductor layer 3 is not limited to the above, and may be formed of gold, silver, aluminum, platinum, chromium, etc. For example, the material forming the antenna conductor layer 3 can be changed according to design specifications.

[0027] The thickness of the antenna conductor layer 3 is 10 μm or more and 30 μm or less. For example, the thickness of the antenna conductor layer 3 is more preferably 15 μm or more and 25 μm or less. The thickness of the antenna conductor layer 3 is not limited to the above and can be changed according to the design specifications as long as the planar antenna 1 can function as an antenna.

[0028] For example, the antenna conductor layer 3 is formed by a method such as plating or printing on the first surface 11 of the dielectric layer 2. The method of forming the antenna conductor layer 3 is not limited to the above and can be changed according to design specifications.

[0029] <Ground conductor layer> The ground conductor layer 4 is disposed on the second surface 12 of the dielectric layer 2. The ground conductor layer 4 is disposed opposite the antenna conductor layer 3 via the dielectric layer 2. The ground conductor layer 4 functions as a ground (GND) when the antenna conductor layer 3 operates. In a plan view, the ground conductor layer 4 has a rectangular shape with the same size as the second layer 22.

[0030] For example, the ground conductor layer 4 is made of a metal (an example of a conductor) such as copper. The ground conductor layer 4 may be made of gold, silver, aluminum, platinum, chromium, etc. For example, the material of the ground conductor layer 4 can be changed according to design specifications.

[0031] The thickness of the ground conductor layer 4 is 10 μm or more and 30 μm or less. For example, the thickness of the ground conductor layer 4 is more preferably 15 μm or more and 25 μm or less. The thickness of the ground conductor layer 4 is not limited to the above and can be changed according to the design specifications as long as the planar antenna 1 can function as an antenna.

[0032] For example, the ground conductor layer 4 is formed by attaching a copper foil film to the second surface 12 of the dielectric layer 2. For example, the ground conductor layer 4 may be formed on the second surface 12 of the dielectric layer 2 by a method such as plating or printing. Note that the method of forming the ground conductor layer 4 is not limited to the above and can be changed according to design specifications.

[0033] <Shape transformation and recovery function> The planar antenna 1 of this embodiment has a shape deformation / recovery function. As described above, the dielectric layer 2 is composed mainly of a shape memory polymer. Therefore, the planar antenna 1 can be deformed into any shape by heating to a temperature transition point or higher of the shape memory polymer and applying an external force. In addition, the planar antenna 1 can be restored to its original shape by heating to a temperature transition point or higher of the shape memory polymer.

[0034] The temperature transition point of a shape memory polymer corresponds to the glass transition temperature (Tg) of the shape memory polymer. The elastic modulus of a shape memory polymer is significantly different at temperatures before and after the glass transition temperature (Tg). The elastic modulus of a shape memory polymer is relatively high at temperatures below Tg and relatively low at temperatures below Tg. The elastic modulus of a shape memory polymer depends on temperature.

[0035] Shape memory polymers are easily deformed by small stress at high temperatures above a certain temperature relative to Tg. In this case, if the maximum strain is held constant and the polymer is cooled to a temperature below a certain temperature relative to Tg, the stress increases as a resistance to thermal contraction (recovery stress). If the polymer is unloaded from this state while still at a low temperature, a residual strain substantially equal to the maximum strain is obtained due to the high elastic modulus (shape fixity). On the other hand, if the polymer is heated from the low-temperature unloaded state to a temperature above a certain temperature relative to Tg under no load, the strain disappears and the polymer returns to its original shape (shape recovery).

[0036] Thus, shape memory polymers have shape fixity and shape recovery properties. That is, when a shape memory polymer is cooled below its Tg while retaining the shape it has been deformed into at a temperature above its Tg, it solidifies in that shape. When it is heated again above its Tg, it returns to the memorized shape.

[0037] <Topology optimization> The following is an overview of topology optimization. The basic idea of ​​topology optimization is to formulate a structural design problem as a material distribution problem within a fixed design domain. In other words, unlike size and shape problems, it is possible to drill holes in the design space.

[0038] FIG. 4 is an explanatory diagram of topology optimization according to the embodiment. In the example shown in the figure, the objective function is the average compliance, the design variable is the volume density, and the constraint condition is the volume. In the figure, D is the design domain, Ωd is the design domain, and Χ Ω denotes the design variable, and Γ denotes the boundary.

[0039] In this case, the extended fixed design domain D includes the original design domain Ωd obtained as the optimal structure, and the characteristic function Χ, which has discretized values ​​of 0 and 1 as shown in the following equation (1), is Ω Introduce (X).

[0040]

number

[0041] The problem of defining the objective function that determines this characteristic function and minimizing (or maximizing) it under arbitrary constraints is expressed by the following equation (2). In equation (2), u is the displacement vector, K is the stiffness matrix, ρ is the material density of the dielectric, F is the load, M C denotes the constrained mass, respectively.

[0042]

number

[0043] This makes it possible to express the optimal shape and form. In some cases, the optimal structure represented by the characteristic function may result in a checkerboard pattern of alternating 0s and 1s, which is difficult to manufacture.

[0044] For this reason, it is necessary to relax the design space. For example, the homogenization method is proposed in the following Non-Patent Document 5, and the density method is proposed in the following Non-Patent Document 6.

[0045] [Non-Patent Document 5] Bendsoee, MP and Kikuchi, N., Generating optimal topologies in structural design using a homogenization method, Computer Methods in Applied Mechanics and Engineering, Vol.71, No.2 (1988), pp.197-224.

[0046] [Non-Patent Document 6] Bendsoee, MP, Optimal shape design as a material distribution problem, Structural and Multidisciplinary Optimization, Vol.1, No.4 (1989), pp.193-202.

[0047] In the density method, the characteristic function is relaxed to a design variable that takes continuous values. For example, in the SIMP method, which is one of the density methods, a clear material distribution structure is obtained using the elastic modulus E before relaxation, the design variable ρ, and the penalty coefficient p, and the material distribution is expressed by assuming elasticity. The elastic modulus E after relaxation H is expressed by the following equation (3).

[0048]

number

[0049] The design variable here is the normalized temporary material density, which takes continuous values ​​from 0 to 1. The closer the value is to 0, the lower the density of the material. The closer the value is to 1, the higher the density of the material. Here, the average compliance, which is the ease with which an object deforms, is adopted as the objective function. Then, by minimizing the average compliance, a structural distribution that maximizes static stiffness is obtained. The sensitivity of the objective function with respect to the design variables is expressed by the following equation (4). In equation (4), "d" in K(d) indicates that K is differentiable.

[0050]

number

[0051] <Action and effect> As described above, the planar antenna 1 of this embodiment includes the dielectric layer 2 having the first surface 11 and the second surface 12 opposite to the first surface 11, the antenna conductor layer 3 arranged on the first surface 11, and the ground conductor layer 4 arranged on the second surface 12. The dielectric layer 2 is composed mainly of a shape memory polymer. According to this configuration, since the dielectric layer 2 is mainly composed of a shape memory polymer, the planar antenna 1 can be deformed into any shape by heating above the temperature transition point of the shape memory polymer and applying an external force. In addition, the planar antenna 1 can be restored to its original shape by heating above the temperature transition point of the shape memory polymer. Therefore, it is possible to provide a planar antenna 1 with shape deformation and recovery functions.

[0052] In this embodiment, at least a portion of the dielectric layer 2 has a hollow structure 15 . This configuration allows for a reduction in weight compared to a case in which the dielectric layer 2 is entirely solid.

[0053] In this embodiment, the dielectric layer 2 has a solid structure 16 at least in a portion overlapping with the antenna conductor layer 3 in plan view. Generally, topology optimization is a method that basically reduces rigidity. According to this configuration, since the dielectric layer 2 has a solid structure 16 at the portion where the dielectric layer 2 overlaps with the antenna conductor layer 3 in a plan view, it is possible to significantly reduce the mass while accepting a slight decrease in rigidity.

[0054] In this embodiment, the dielectric layer 2 includes a first layer 21 having a first surface 11, a second layer 22 having a second surface 12, and an intermediate layer 23 disposed between the first layer 21 and the second layer 22. According to this configuration, the dielectric layer 2 has a laminated structure including the first layer 21, the second layer 22 and the intermediate layer .

[0055] In this embodiment, the intermediate layer 23 has a solid structure 16 in a portion overlapping with the antenna conductor layer 3 and has a hollow structure 15 in a portion not overlapping with the antenna conductor layer 3 in a plan view. According to this configuration, deformation of the antenna conductor layer 3 can be suppressed while achieving weight reduction.

[0056] In this embodiment, the first layer 21 and the second layer 22 are rectangular and of the same size in a plan view. The antenna conductor layer 3 is disposed in the center of the first surface 11 and is rectangular and of a smaller size than the first layer 21 in a plan view. The ground conductor layer 4 is rectangular and of the same size as the second layer 22 in a plan view. According to this configuration, it is possible to realize a shape suitable for achieving high rigidity and light weight for the planar antenna 1.

[0057] In this embodiment, the dielectric layer 2 is square in plan view. At least some of the hollow structures 15 are arranged at positions that are four-fold symmetric with respect to the center of the dielectric layer 2. According to this configuration, it is possible to realize a shape that is more suitable for achieving high rigidity and light weight for the planar antenna 1.

[0058] In this embodiment, the antenna conductor layer 3 and the ground conductor layer 4 each have a thickness of 10 μm or more and 30 μm or less. According to this configuration, it is possible to realize a shape that is more suitable for achieving high rigidity and light weight for the planar antenna 1.

[0059] In the planar antenna 1 of this embodiment, the dielectric layer 2 is mainly composed of a shape memory polymer, and therefore it can be deformed into any shape by heating above the temperature transition point of the shape memory polymer and by external force, and can be restored to its original shape by heating above the temperature transition point of the shape memory polymer. Therefore, for example, the planar antenna 1 can be deformed by heating to fit into a narrow space inside a rocket, and folded and stored. For example, it is possible to use the folded planar antenna 1 by heating it at a necessary place after orbital insertion. Furthermore, the shape recovery action of the planar antenna 1 itself plays the role of an actuator, which makes it possible to remove the constraints such as size restrictions and restrictions on the mounting position for mounting on a deployment support part.

[0060] For example, a large space structure carrying space systems such as a power generation system and a wireless transmission system is mainly composed of a microwave array antenna spread over the entire surface of the structure. Therefore, by configuring the entire surface with the planar antenna 1 of this embodiment, it is possible to reduce the total weight of the large space structure.

[0061] Generally, the dielectric material constituting the planar antenna accounts for a large part of the structural mass of the entire planar antenna. In contrast, according to this embodiment, the dielectric layer 2 has a hollow structure 15, which is highly effective in reducing the total weight of the planar antenna 1.

[0062] On the other hand, since the system requires planar accuracy, it is necessary to prevent the rigidity of the structure from being impaired as much as possible. According to this embodiment, by applying the planar antenna 1 in which the topology of the dielectric is optimized, it is possible to maintain the rigidity of the structure while reducing the weight.

[0063] For example, when a planar antenna is mounted on a satellite structure, there is a high possibility that the antenna gain will be reduced due to reflection from surrounding structures. Therefore, it is necessary to maximize the antenna gain, and it is required to increase the gain of the antenna itself as much as possible. According to this embodiment, by applying the planar antenna 1 in which the above-mentioned topology has been optimized, it is possible to maximize the antenna gain while maintaining the rigidity of the structure and reducing the weight.

[0064] <Modification> In the above-described embodiment, an example has been described in which at least a part of the dielectric layer has a hollow structure, but this is not limited thereto. For example, the entire dielectric layer may have a solid structure. For example, the configuration of the dielectric layer may be changed according to design specifications.

[0065] In the above-described embodiment, an example has been described in which the dielectric layer has a solid structure at least in the portion overlapping with the antenna conductor layer in a plan view, but this is not limited thereto. For example, the dielectric layer may have a hollow structure in the entire portion overlapping with the antenna conductor layer in a plan view. For example, the configuration of the portion where the dielectric layer overlaps with the antenna conductor layer in a plan view can be changed according to design specifications.

[0066] In the above-mentioned embodiment, the dielectric layer includes a first layer having a first surface, a second layer having a second surface, and an intermediate layer disposed between the first layer and the second layer, but is not limited thereto. For example, the dielectric layer may not include any of the first layer, the second layer, and the intermediate layer. For example, the dielectric layer may have a single-layer structure. For example, the layer structure of the dielectric layer may be changed according to the design specifications.

[0067] In the above-described embodiment, an example has been described in which the intermediate layer has a solid structure in a portion overlapping with the antenna conductor layer in a plan view and a hollow structure in a portion not overlapping with the antenna conductor layer, but this is not limited thereto. For example, the intermediate layer may have a hollow structure in a portion overlapping with the antenna conductor layer in a plan view. For example, the configuration of the portion where the intermediate layer overlaps with the antenna conductor layer in a plan view can be changed according to design specifications.

[0068] In the above embodiment, the first layer and the second layer are rectangular in shape and of the same size in plan view, but this is not limited to the above. For example, the first layer and the second layer may be rectangular in shape and of different sizes in plan view, or may be different shapes (e.g., shapes other than a rectangle, such as circles). For example, the size and shape of the first layer and the second layer in plan view can be changed according to the design specifications.

[0069] In the above-described embodiment, an example has been described in which the antenna conductor layer is disposed at the center of the first surface and has a rectangular shape smaller than the first layer in plan view, but this is not limited thereto. For example, the antenna conductor layer may be disposed at a position shifted from the center of the first surface in plan view. For example, the antenna conductor layer may be rectangular and of the same size as the first layer in plan view, or may have a different shape from the first layer (for example, a shape other than a rectangle, such as a circle). For example, the planar arrangement and shape of the antenna conductor layer can be changed according to design specifications.

[0070] In the above-described embodiment, the ground conductor layer has a rectangular shape of the same size as the second layer in a plan view, but this is not limited thereto. For example, the ground conductor layer may have a rectangular shape of a different size from the second layer in a plan view, or may have a different shape from the second layer (for example, a shape other than a rectangle, such as a circle). For example, the size and shape of the ground conductor layer in a plan view can be changed according to design specifications.

[0071] In the above-described embodiment, an example has been described in which the dielectric layer is square in plan view, and at least a part of the hollow structure is arranged at a position with four-fold symmetry with the center of the dielectric layer as the axis of symmetry, but this is not limited thereto. For example, the dielectric layer may be rectangular, or may be a polygon other than a rectangle, or may be circular in plan view. For example, at least a part of the hollow structure may be arranged at a position with n-fold symmetry (n is an integer of 2 or more) other than four-fold symmetry with the center of the dielectric layer as the axis of symmetry. For example, the plan view shape of the dielectric layer and the plan view arrangement of the hollow structure can be changed according to design specifications.

[0072] In the above-described embodiment, the thickness of each of the antenna conductor layer and the ground conductor layer is 10 μm or more and 30 μm or less, but the present invention is not limited to this. For example, the thickness of at least one of the antenna conductor layer and the ground conductor layer may be less than 10 μm or more than 30 μm. For example, the thickness of each of the antenna conductor layer and the ground conductor layer may be changed according to the design specifications. For example, when the conductor layer is formed of copper foil or the like, this part does not need to be on the order of μm. For example, when the conductor layer is formed by vapor deposition, this part may be on the order of nm or Å.

[0073] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and additions, omissions, substitutions, and other modifications of the configuration are possible without departing from the spirit of the present invention, and the above-described embodiments can also be combined as appropriate.

[0074] (Appendix 1) a dielectric layer having a first surface and a second surface opposite the first surface; an antenna conductor layer disposed on the first surface; a ground conductor layer disposed on the second surface, The dielectric layer is mainly composed of a shape memory polymer. Flat antenna.

[0075] (Appendix 2) At least a portion of the dielectric layer has a hollow structure. 2. A planar antenna as defined in claim 1.

[0076] (Appendix 3) In a plan view, the dielectric layer has a solid structure at least in a portion overlapping the antenna conductor layer. 3. A planar antenna as claimed in claim 1 or 2.

[0077] (Appendix 4) The dielectric layer is a first layer having the first surface; a second layer having the second surface; and an intermediate layer disposed between the first layer and the second layer, 4. A planar antenna according to any one of claims 1 to 3.

[0078] (Appendix 5) In a plan view, the intermediate layer has a solid structure in a portion overlapping with the antenna conductor layer and a hollow structure in a portion not overlapping with the antenna conductor layer. 5. A planar antenna as defined in claim 4.

[0079] (Appendix 6) In the plan view, the first layer and the second layer are rectangular and have the same size, In the plan view, the antenna conductor layer is disposed at the center of the first surface and has a rectangular shape smaller than the first layer; In the plan view, the ground conductor layer has a rectangular shape having the same size as the second layer. 6. A planar antenna as defined in claim 5.

[0080] (Appendix 7) In the plan view, the dielectric layer has a square shape, At least a part of the hollow structure is disposed at a position that is four-fold symmetrical with respect to the center of the dielectric layer. 7. A planar antenna as defined in claim 6.

[0081] (Appendix 8) The antenna conductor layer and the ground conductor layer each have a thickness of 10 μm or more and 30 μm or less. 8. A planar antenna according to any one of claims 1 to 7. EXAMPLES

[0082] The planar antenna according to the above embodiment of the present invention will be specifically described below by showing examples. Note that the following examples are specific examples to which the present invention is applied, and do not limit the present invention.

[0083] FIG. 5 is an explanatory diagram of the design and analysis results of the comparative example. FIG. 6 is an explanatory diagram of the design and analysis results of Examples 1-2. FIG. 7 is an explanatory diagram of the design and analysis results of Example 2. FIG. 8 is an explanatory diagram of the design and analysis results of Example 3. FIG. 9 is an explanatory diagram of the design and analysis results of Example 4. FIG. 10 is an explanatory diagram of the design and analysis results of Example 5.

[0084] (Example) The planar antenna of the embodiment includes a dielectric layer having a first surface and a second surface opposite to the first surface, an antenna conductor layer arranged on the first surface, and a ground conductor layer arranged on the second surface, the dielectric layer being composed primarily of a shape memory polymer, and at least a portion of the dielectric layer having a hollow structure (corresponding to the configuration shown in Figure 1). As examples, as shown in Figs. 6 to 10, examples 1-2 to 5 were prepared in which the design of the planar antenna (shape, size, pattern, etc. of the components) was changed.

[0085] (Comparative Example) As the comparative planar antenna, a normal planar antenna in which the dielectric layer does not have a hollow structure was prepared. As the comparative example, the one shown in FIG.

[0086] (Experimental Equipment) Figure 11 is a front view of the experimental equipment, and Figure 12 is a side view of the experimental equipment. The experimental equipment used in the examples and comparative examples was as shown in Figures 11 and 12. Each planar antenna was installed on this experimental equipment, and the radiation pattern was obtained.

[0087] (Example 1-2) As an example, the radiation pattern of the planar antenna of Example 1-2 will be described. Fig. 13 is a plan view of the planar antenna of Example 1-2, and Fig. 14 is a perspective view showing a part of the radiation pattern of the planar antenna of Example 1-2. 13 to 14, it was confirmed that the radiation pattern of the planar antenna of Example 1-2 has a circular shape that is long on the left and right sides of the paper when viewed from the front, and a shape that bulges out toward the left side of the paper when viewed from the side. Note that FIG. 14 corresponds to a perspective view of the upper half of the radiation pattern.

[0088] (Evaluation Results) The gain (antenna gain) of each planar antenna was measured through analytical experiments. The evaluation results are shown in Figures 5 to 10.

[0089] 5 to 10, it was confirmed that the planar antennas of the examples had a larger antenna gain than the planar antennas of the comparative examples, except for Example 2. This shows that the planar antennas of the examples can maintain the rigidity of the structure while reducing the weight, and maximize the antenna gain. [Explanation of symbols]

[0090] Reference Signs List 1...planar antenna, 2...dielectric layer, 3...antenna conductor layer, 4...ground conductor layer, 11...first surface, 12...second surface, 15...hollow structure, 16...solid structure, 21...first layer, 22...second layer, 23...middle layer

Claims

1. a dielectric layer having a first surface and a second surface opposite the first surface; an antenna conductor layer disposed on the first surface; a ground conductor layer disposed on the second surface, The dielectric layer is mainly composed of a shape memory polymer. Flat antenna.

2. At least a portion of the dielectric layer has a hollow structure.

2. A planar antenna as claimed in claim 1.

3. In a plan view, the dielectric layer has a solid structure at least in a portion overlapping the antenna conductor layer.

3. A planar antenna according to claim 1 or 2.

4. The dielectric layer is a first layer having the first surface; a second layer having the second surface; and an intermediate layer disposed between the first layer and the second layer, 3. A planar antenna according to claim 1 or 2.

5. In a plan view, the intermediate layer has a solid structure in a portion overlapping with the antenna conductor layer and a hollow structure in a portion not overlapping with the antenna conductor layer.

5. A planar antenna according to claim 4.

6. In the plan view, the first layer and the second layer have a rectangular shape of the same size, In the plan view, the antenna conductor layer is disposed at the center of the first surface and has a rectangular shape smaller than the first layer; In the plan view, the ground conductor layer has a rectangular shape having the same size as the second layer.

6. A planar antenna as claimed in claim 5.

7. In the plan view, the dielectric layer has a square shape, At least a part of the hollow structure is disposed at a position that is four-fold symmetrical with respect to the center of the dielectric layer.

7. A planar antenna according to claim 6.

8. The antenna conductor layer and the ground conductor layer each have a thickness of 10 μm or more and 30 μm or less.

3. A planar antenna according to claim 1 or 2.

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