JP7652443B2 - Planar Antenna - Google Patents

Description

The present invention relates to a planar antenna.

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 accommodate two frequencies by incorporating the concept of an adaptive structure that changes its overall length by using a lattice structure with an expandable radiator and three structural safety points.
In general, planar antennas are made of a single material that covers the entire 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 the 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.

International Journal of Applied Electromagnetics and Mechanics 50 (2015) 1-4 IOS Press, Topology Optimization of Wideband ArrayAntenna for Microwave Energy Harvester, Takuya Mori and Hajime Igarashi, The final publication is available at IOS Press through http://dx.doi.org/10.3233/JAE-162057 AIAA SciTech Forum January 3-7, 2022, San Diego, CA & Virtual AIAA SCITECH 2022 Forum, 10.2514/6.2022-0923, Enhancing multi-stability in helical lattices for adaptive structures, Maria Sakovsky, Rosette Maria Bichara, Youssef Tawk and Joseph Costantine IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 10, OCTOBER 2003, Topology Design Optimization of Dielectric Substrates for Bandwidth Improvement of a Patch Antenna, Gullu Kiziltas, Dimitris Psychoudakis, John L. Volakis and Noboru Kikuchi AIAA SciTech Forum, 11-15 &

There is a demand for technology that allows planar antennas to have the ability to deform and recover their shape. However, none of Non-Patent Documents 1 to 4 discloses the above technology.

The present invention aims to provide a planar antenna that has the ability to deform and recover its shape.

A planar antenna according to one aspect of the present invention includes a dielectric layer having a first surface and a second surface opposite to the first surface, an antenna conductor layer disposed on the first surface, and a ground conductor layer disposed on the second surface, and the dielectric layer is composed primarily of a shape memory polymer.

The above aspect makes it possible to provide a planar antenna that has the ability to deform and recover its shape.

FIG. 1 is a perspective view of a planar antenna according to an embodiment. FIG. 2 is a plan view of a planar antenna according to the embodiment. FIG. 2 is a diagram showing an example of a radiation pattern of a planar antenna according to the embodiment. FIG. 2 is an explanatory diagram of topology optimization according to the embodiment. 1A to 1C are explanatory diagrams of design and analysis results of a comparative example. FIG. 11 is an explanatory diagram of the design and analysis results of Example 1-2. FIG. 11 is an explanatory diagram of the design and analysis results of the second embodiment. FIG. 13 is an explanatory diagram of the design and analysis results of the third embodiment. FIG. 13 is an explanatory diagram of the design and analysis results of the fourth embodiment. FIG. 13 is an explanatory diagram of the design and analysis results of the fifth embodiment. Front view of the experimental equipment. Side view of the experimental equipment. FIG. 4 is a plan view of a planar antenna according to an embodiment 1-2. FIG. 13 is a perspective view showing a portion of the radiation pattern of the planar antenna according to the embodiment 1-2.

Embodiments of the present invention will be described below with reference to the drawings. In the embodiments, 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 can be 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).

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 that allows tolerance or the same function to be obtained. In the drawings used in the following description, the scale of each component may be changed as appropriate to make each component recognizable.

<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.

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 feed point) connected to the antenna conductor layer 3, and the other end which is a power feed end connected to an external device (not shown).

In the example shown in the figure, 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 shape of the planar antenna 1 is not limited to the above and can be changed according to the design specifications.

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.

For example, the planar antenna 1 may have flexibility as a whole. For example, the planar antenna 1 may be configured so that it can be curved as the side of a cylinder as a whole. For example, the planar antenna 1 may be configured so that it has flexible elastic properties so that it can be folded.

<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 a constant distance between the antenna conductor layer 3 and the ground conductor layer 4. 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.

The dielectric layer 2 is composed mainly of a shape memory polymer. The term "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 shape memory polymer, and more preferably containing 90 wt% or more of shape memory polymer. The proportion of shape memory polymer contained in the dielectric layer 2 is not limited to the above and can be changed according to the design specifications.

Shape memory polymers have the following characteristics (1) to (5).
(1) The shape molded at or above the melting point is memorized.
(2) After shaping, it becomes soft when heated above its glass transition temperature Tg.
(3) Once the object has softened, its shape can be modified and adjusted.
(4) When cooled in the deformed state, the shape is fixed.
(5) When heated again, it softens and returns to its original shape.

For example, an example of a shape memory polymer is a polyurethane-based shape memory polymer. For example, the dielectric layer 2 is formed of a polyurethane-based shape memory polymer. Note that the material for forming the dielectric layer 2 is not limited to the above and can be changed according to the design specifications.

At least a portion of the dielectric layer 2 has a hollow structure 15. The hollow structure 15 is a structure formed with air contained inside the dielectric layer 2, and corresponds to the hollowed-out portion of the dielectric layer 2. In a plan view, the dielectric layer 2 has a solid structure 16 at least in the 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 the portion of the dielectric layer 2 other than the hollowed-out portion.

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.

In the example shown in the figure, 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 portion of the hollow structure 15 is disposed in a position that is four-fold symmetrical with the center of the dielectric layer 2 as the axis of symmetry.

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, it is more preferable that the thickness of the dielectric layer 2 is 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.

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. Note that the method of forming the dielectric layer 2 is not limited to the above and can be changed according to the design specifications.

<Antenna conductor layer>
The antenna conductor layer 3 has a role of converting radio waves irradiated from the outside into electric current, or converting a current that is fed 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.

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 the design specifications.

The thickness of the antenna conductor layer 3 is 10 μm or more and 30 μm or less. For example, it is more preferable that the thickness of the antenna conductor layer 3 is 15 μm or more and 25 μm or less. Note that 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.

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

<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 having the same size as the second layer 22.

For example, the ground conductor layer 4 is formed of a metal (an example of a conductor) such as copper. Note that the ground conductor layer 4 is not limited to the above, and may be formed of gold, silver, aluminum, platinum, chromium, etc. For example, the material forming the ground conductor layer 4 can be changed according to the design specifications.

The thickness of the ground conductor layer 4 is 10 μm or more and 30 μm or less. For example, it is more preferable that the thickness of the ground conductor layer 4 is 15 μm or more and 25 μm or less. Note that 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.

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 the design specifications.

<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 mainly composed 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.

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 differs greatly 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.

Shape memory polymers are easily deformed by small stresses at high temperatures above the Tg. In this case, if the maximum strain is held constant and the polymer is cooled to a low temperature below the 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 high temperature above the Tg under no load, the strain disappears and the polymer returns to its original shape (shape recovery).

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

<Topology optimization>
Below 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.

4 is an explanatory diagram of topology optimization according to an 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 indicates the design domain, Ωd indicates the design domain, _XΩ indicates the design variable, and Γ indicates the boundary.

In this case, an extended fixed design domain D including the original design domain Ωd obtained as the optimal structure and a characteristic function X _Ω (X) having discretized values of 0 and 1 shown in the following equation (1) are introduced.

The problem of defining an 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 a displacement vector, K is a stiffness matrix, ρ is the material density of the dielectric material, F is a load, and _M is a constrained mass.

This allows for the expression of optimal shapes and forms.
In some cases, the optimum structure represented by the characteristic function may result in a checkerboard pattern of alternating 0s and 1s, which is difficult to manufacture.

For this reason, it is necessary to relax the design space; for example, the homogenization method is proposed in the non-patent literature 5 below, and the density method is proposed in the non-patent literature 6 below.

[Non-patent Document 5] Bendsoee, M. P. 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.

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

In the density method, the characteristic function is relaxed to a design variable that takes a continuous value. 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 ^EH after relaxation is expressed by the following formula (3).

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 variable is expressed by the following equation (4). In equation (4), "d" in K(d) indicates that K is differentiable.

<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 disposed on the first surface 11, and the ground conductor layer 4 disposed on the second surface 12. The dielectric layer 2 is mainly composed 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 that has a shape deformation and recovery function.

In this embodiment, at least a portion of the dielectric layer 2 has a hollow structure 15 .
This configuration can reduce the weight compared to a case where the dielectric layer 2 is entirely solid.

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 a plan view.
Generally, topology optimization is a technique that basically reduces rigidity. According to this configuration, since the dielectric layer 2 has the 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 sacrifice of reduced rigidity.

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 23.

In this embodiment, the intermediate layer 23 has a solid structure 16 in a portion overlapping with the antenna conductor layer 3 and a hollow structure 15 in a portion not overlapping with the antenna conductor layer 3 in a plan view.
According to this configuration, it is possible to suppress deformation of the antenna conductor layer 3 and achieve weight reduction.

In this embodiment, the first layer 21 and the second layer 22 are rectangular and of the same size in a plan view. 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.
According to this configuration, it is possible to realize a shape suitable for achieving high rigidity and light weight for the planar antenna 1.

In this embodiment, the dielectric layer 2 has a square shape in a 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 .

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.

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 the narrow space inside a rocket, and then folded and stored. For example, it can be used by deploying the folded planar antenna 1 by heating it in 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.

For example, large space structures that carry space systems such as power generation systems and wireless transmission systems are mainly composed of microwave array antennas spread across the entire surface of the structure. Therefore, by constructing the entire surface with the planar antenna 1 of this embodiment, it is possible to reduce the total weight of the large space structure.

In general, the dielectric material that constitutes a planar antenna accounts for a large portion 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 beneficial in reducing the total weight of the planar antenna 1.

On the other hand, because the system requires planar precision, it is necessary to prevent the structural rigidity from being impaired as much as possible. According to this embodiment, by applying a planar antenna 1 in which the topology of the dielectric has been optimized, it is possible to maintain the structural rigidity while reducing the weight.

For example, if a planar antenna is mounted on a satellite structure, there is a high possibility that the antenna gain will decrease due to reflections from surrounding structures. For this reason, 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 that has undergone the above-mentioned topology optimization, it is possible to maximize the antenna gain while maintaining the rigidity of the structure and reducing the weight.

<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.

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

In the above-described 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 the present invention is not limited to this. 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 can be changed according to the design specifications.

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

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

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 offset 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 the design specifications.

In the above-described embodiment, an example has been described in which the ground conductor layer has a rectangular shape of the same size as the second layer in a planar view, but this is not limited to the above. For example, the ground conductor layer may have a rectangular shape of a different size from the second layer in a planar 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 planar size and shape of the ground conductor layer can be changed according to the design specifications.

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 in 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, in a plan view, the dielectric layer may be rectangular, or may be a polygon other than a rectangle, or may be circular. For example, in a plan view, at least a part of the hollow structure may be arranged in 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 the design specifications.

In the above-described embodiment, the thickness of each of the antenna conductor layer and the ground conductor layer is described as being 10 μm or more and 30 μm or less, but this is not limited to the above. 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 can be changed according to the design specifications. For example, if 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, if the conductor layer is formed by vapor deposition, this part may be on the order of nm or Å.

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-mentioned embodiments can also be combined as appropriate.

(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.

(Appendix 2)
At least a portion of the dielectric layer has a hollow structure.
2. The planar antenna of claim 1.

(Appendix 3)
In a plan view, the dielectric layer has a solid structure at least in a portion overlapping the antenna conductor layer.
3. The planar antenna according to claim 1 or 2.

(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 as claimed in any one of claims 1 to 3.

(Appendix 5)
In a plan view, the intermediate layer has a solid structure in a portion overlapping with the antenna conductor layer and has a hollow structure in a portion not overlapping with the antenna conductor layer.
5. The planar antenna of claim 4.

(Appendix 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. The planar antenna of claim 5.

(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. The planar antenna of claim 6.

(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 as claimed in any one of claims 1 to 7.

The planar antenna according to the above embodiment of the present invention will be specifically described below with reference to examples. Note that the following examples are specific examples in which the present invention is applied, and do not limit the present invention.

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

(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.

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 shown in FIG.

(Experimental equipment)
11 and 12 are front and side views 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.

(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 and 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.

(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.

Referring to Figures 5 to 10 together, it was confirmed that the planar antennas of the examples, except for Example 2, had a larger antenna gain than the planar antennas of the comparative examples. This shows that the planar antennas of the examples can be made lighter while maintaining the rigidity of the structure and maximizing the antenna gain.

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... Intermediate layer

Claims (8)

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. At least a portion of the dielectric layer has a hollow structure.
2. A planar antenna as claimed in claim 1. 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. 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. In a plan view, the intermediate layer has a solid structure in a portion overlapping with the antenna conductor layer and has a hollow structure in a portion not overlapping with the antenna conductor layer.
5. A planar antenna according to claim 4. 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. 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. 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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