Planar antenna

Abstract

Provided is a planar antenna that can radiate and receive radio waves in opposite directions without requiring a change in posture. 【Solution means】The planar antenna includes a ground conductor layer, a dielectric layer including a first layer and a second layer disposed outside the ground conductor layer via the ground conductor layer, a first antenna conductor layer disposed on a first surface of the first layer opposite to the ground conductor layer and having a first radiation surface, and a second antenna conductor layer disposed on a second surface of the second layer opposite to the ground conductor layer and having a second radiation surface facing opposite to the first radiation surface.

Description

Technical Field

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

Background Art

[0002] For example, Non-Patent Document 1 discloses a helical antenna that can adopt a lattice structure with a stretchable radiator having three structural safety points and can change the overall length, incorporating the concept of an adaptive structure, and can respond to two frequencies. As an ultra-lightweight planar patch antenna, an array antenna in which a patch pattern is directly printed on a foldable and deployable Kapton film is known (see, for example, Non-Patent Document 2).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, planar antennas are required to have a technology that can radiate and receive radio waves in opposite directions without the need to change the attitude. However, neither Non-Patent Document 1 nor Non-Patent Document 2 discloses the above technology.

[0005] Therefore, an object of the present invention is to provide a planar antenna that can radiate and receive radio waves in opposite directions without the need to change the attitude.

Means for Solving the Problems

[0006] The planar antenna according to one aspect of the present invention includes a ground conductor layer, a dielectric layer including a first layer and a second layer disposed outside the ground conductor layer via the ground conductor layer, a first antenna conductor layer disposed on a first surface of the first layer opposite to the ground conductor layer and having a first radiation surface, and a second antenna conductor layer disposed on a second surface of the second layer opposite to the ground conductor layer and having a second radiation surface facing opposite to the first radiation surface. , at least a part of the dielectric layer has a hollow structure, in a plan view, a part of the dielectric layer is square, and in the plan view, at least a part of the hollow structure is arranged at a position that is four-fold symmetric with the center of the square portion of the dielectric layer as the axis of symmetry. .

Effects of the Invention

[0007] According to the above aspect, it is possible to provide a planar antenna that can radiate and receive radio waves in opposite directions without requiring a change in posture.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, as an example of a planar antenna, an example of a deployable two-panel patch antenna for space with switchable observation directions using different resonance frequencies will be described. For example, the planar antenna of the present embodiment is used for realizing a space solar power system (SSPS), wireless energy transmission technology using microwaves or laser light, structural technology of large structures in space, and the like.

[0010] In the following description, expressions indicating relative or absolute arrangements such as "parallel", "orthogonal", "center", "coaxial", etc. not only strictly mean such arrangements and states, but also include arrangements and states that are relatively displaced with tolerances and angles or distances that can obtain the same function. In the drawings used in the following description, the scales of the respective members may be appropriately changed in order to make the respective members recognizable in size.

[0011] <Planar Antenna> FIG. 1 is a perspective view of a planar antenna 1 according to the first embodiment. FIG. 2 is a plan view of the planar antenna 1 according to the first embodiment as viewed from the first radiation surface 4a side. FIG. 3 is a plan view of the planar antenna 1 according to the first embodiment as viewed from the second radiation surface 5a side. FIG. 4 is a view including the IV-IV cross section of FIG. 2. Referring to FIGS. 1 to 4 together, the planar antenna 1 includes a dielectric layer 2, a ground conductor layer 3, a first antenna conductor layer 4, and a second antenna conductor layer 5. For example, the planar antenna 1 is configured such that its shape is fixed when no heat or external force is acting, and it can return to the stored initial shape when heat or external force acts.

[0012] In the following description, the orthogonal coordinate system of x, y, and z will be used as necessary. The x direction corresponds to the left-right direction (width direction) of the planar antenna 1. The y direction corresponds to the up-down direction (height direction) of the planar antenna 1. The z direction corresponds to the front-back direction (thickness direction) of the planar antenna 1 that is orthogonal to each of the x direction and the y direction. In the following description, among the x direction, the y direction, and the z direction, the side of the arrow in the figure is taken as the plus (+) side, and the side opposite to the arrow is taken as the minus (-) side for explanation. The +z side corresponds to the front side (the first radiation surface 4a side), and the -z side corresponds to the rear side (the second radiation surface 5a side).

[0013] In the example of the figure, the planar antenna 1 has a rectangular shape in plan view (a rectangular shape that is long in the x direction). For example, the planar antenna 1 is formed in a plate shape of a rectangle in plan 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.

[0014] For example, the thickness of the planar antenna 1 is 1 mm or more and 10 mm or less. In the example of the figure, the thickness of the planar antenna 1 is about 6.4 mm. The thickness of the planar antenna 1 corresponds to the sum of the thickness of the dielectric layer 2, the thickness of the ground conductor layer 3, the thickness of the first antenna conductor layer 4, and the thickness of the second antenna conductor layer 5. 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 to be curved like the side surface of a cylinder as a whole. For example, the planar antenna 1 may be configured to have flexible elastic characteristics that allow it to be folded.

[0016] <Dielectric layer> The dielectric layer 2 is a layered base material mainly composed of a dielectric. The dielectric layer 2 has the role of keeping the intervals between the ground conductor layer 3 and the first antenna conductor layer 4, and between the ground conductor layer 3 and the second antenna conductor layer 5 constant. The dielectric layer 2 includes a first layer 21 and a second layer 22 disposed outside the ground conductor layer 3 via the ground conductor layer 3. The first layer 21 has a first surface 21a on the side opposite to the ground conductor layer 3 in the z direction. The second layer 22 has a second surface 22a on the side opposite to the ground conductor layer 3 in the z direction. The first surface 21a corresponds to one side surface in the thickness direction of the first layer 21 constituting the dielectric layer 2 (the front side surface of the dielectric layer 2). The second surface 22a corresponds to the other side surface in the thickness direction of the second layer 22 constituting the dielectric layer 2 (the rear side surface of the dielectric layer 2). The first surface 21a and the second surface 22a are parallel to each other.

[0017] The dielectric layer 2 is composed mainly of a shape memory polymer (SMP). 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 to contain 80 wt% or more of the shape memory polymer, and more preferably 90 wt% or more of the shape memory polymer. Note that the ratio 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] The shape memory polymer has the following characteristics (1) to (5). (1) It remembers the shape formed above the melting point. (2) After shaping, it becomes soft when warmed above the glass transition temperature Tg. (3) The softened shaped article can be deformed and adjusted in shape. (4) When cooled in the deformed state, the shape is fixed. (5) By warming again, it becomes soft and returns to the original shape it remembered.

[0019] For example, as the shape memory polymer, a polyurethane-based shape memory polymer can be mentioned. For example, the dielectric layer 2 is formed of a polyurethane-based shape memory polymer. Note that the forming material of the dielectric layer 2 is not limited to the above and can be changed according to the design specifications.

[0020] In the example of the figure, in plan view, the dielectric layer 2 is rectangular (a rectangular shape long in the x direction). 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 rectangular in plan view. In plan view, the first layer 21 and the second layer 22 are rectangular shapes of the same size as each other.

[0021] For example, the thickness of the first layer 21 is 1 mm or more and 5 mm or less. In the example of the figure, the thickness of the first layer 21 is about 3 mm. For example, the thickness of the second layer 22 is 1 mm or more and 5 mm or less. In the example of the figure, the thickness of the second layer 22 is about 3 mm. For example, the thicknesses of the first layer 21 and the second layer 22 may be the same as each other. Note that the thicknesses of the first layer 21 and the second layer 22 are not limited to the above and can be changed according to the design specifications within the range in which the planar antenna 1 can function as an antenna.

[0022] For example, the first layer 21 and the second layer 22 are formed by a 3D printer using filaments of a shape memory polymer. For example, the first layer 21 and the second layer 22 may be formed by laser sintering using powders of a shape memory polymer. Note that the forming methods of the first layer 21 and the second layer 22 are not limited to the above and can be changed according to the design specifications.

[0023] <Ground conductor layer> The ground conductor layer 3 is disposed between the first layer 21 and the second layer 22. The ground conductor layer 3 is disposed to face the first antenna conductor layer 4 via the first layer 21. The ground conductor layer 3 is disposed to face the second antenna conductor layer 5 via the second layer 22. The ground conductor layer 3 functions as a ground (GND) when the first antenna conductor layer 4 and / or the second antenna conductor layer 5 operates. In plan view, the ground conductor layer 3 is a rectangular shape of the same size as the first layer 21.

[0024] For example, the ground conductor layer 3 is formed of a metal such as copper (an example of a conductor). Note that the ground conductor layer 3 is not limited to the above, and may be formed of gold, silver, aluminum, platinum, chromium, or the like. For example, the material for forming the ground conductor layer 3 can be changed according to the design specifications.

[0025] For example, the thickness of the ground conductor layer 3 is 0.01 mm or more and 0.05 mm or less. In the example of the figure, the thickness of the ground conductor layer 3 is about 0.03 mm. Note that the thickness of the ground conductor layer 3 is not limited to the above, and can be changed according to the design specifications within the range in which the planar antenna 1 can function as an antenna.

[0026] For example, the ground conductor layer 3 is formed by attaching a copper foil film to the surface on the side opposite to the first surface 21a of the first layer 21 (the surface on the -Z side). For example, the ground conductor layer 3 may be formed by a method such as plating or printing on the surface on the side opposite to the first surface 21a of the first layer 21. For example, the first layer 21 and the second layer 22 may be adhered sharing the ground conductor layer 3. For example, it is desirable that the ground conductor layer 3 is formed by vapor deposition. Note that the method for forming the ground conductor layer 3 is not limited to the above, and can be changed according to the design specifications.

[0027] <First Antenna Conductor Layer> The first antenna conductor layer 4 has the role of converting radio waves irradiated from the outside into an electric current, or converting the supplied electric current into radio waves radiated to the outside. The first antenna conductor layer 4 is disposed on the first surface 21a of the dielectric layer 2 (the first layer 21). The first antenna conductor layer 4 has a first radiation surface 4a that radiates radio waves.

[0028] For example, the first antenna conductor layer 4 is formed of a metal such as copper (an example of a conductor). Note that the first antenna conductor layer 4 is not limited to the above, and may be formed of gold, silver, aluminum, platinum, chromium, or the like. For example, the material for forming the first antenna conductor layer 4 can be changed according to the design specifications.

[0029] The thickness of the first antenna conductor layer 4 is 0.01 mm or more and 0.3 mm or less. In the example of the figure, the thickness of the first antenna conductor layer 4 is about 0.05 mm. Note that the thickness of the first antenna conductor layer 4 is not limited to the above, and can be changed according to the design specifications within the range in which the planar antenna 1 can function as an antenna.

[0030] For example, the first antenna conductor layer 4 is formed on the first surface 21a of the first layer 21 by a method such as vapor deposition, plating, or printing. Note that the formation method of the first antenna conductor layer 4 is not limited to the above, and can be changed according to the design specifications.

[0031] <Second Antenna Conductor Layer> The second antenna conductor layer 5 has the role of converting the radio waves irradiated from the outside into an electric current, or converting the supplied electric current into radio waves radiated to the outside. The second antenna conductor layer 5 is disposed on the second surface 22a of the dielectric layer 2 (second layer 22). The second antenna conductor layer 5 has a second radiation surface 5a that radiates radio waves. The second radiation surface 5a faces the opposite direction to the first radiation surface 4a.

[0032] For example, the second antenna conductor layer 5 is formed of a metal such as copper (an example of a conductor). Note that the second antenna conductor layer 5 is not limited to the above, and may be formed of gold, silver, aluminum, platinum, chromium, or the like. For example, the second antenna conductor layer 5 may be formed of the same metal as the first antenna conductor layer 4. For example, the formation material of the second antenna conductor layer 5 can be changed according to the design specifications.

[0033] The thickness of the second antenna conductor layer 5 is 0.01 mm or more and 0.3 mm or less. In the example of the figure, the thickness of the second antenna conductor layer 5 is about 0.05 mm. For example, the thickness of the second antenna conductor layer 5 may be the same as the thickness of the first antenna conductor layer 4. Note that the thickness of the first antenna conductor layer 4 is not limited to the above, and can be changed according to the design specifications within the range in which the planar antenna 1 can function as an antenna.

[0034] For example, the second antenna conductor layer 5 is formed on the second surface 22a of the second layer 22 by a method such as vapor deposition, plating, or printing. Note that the formation method of the second antenna conductor layer 5 is not limited to the above and can be changed according to the design specifications.

[0035] <Relationship between Frequency and Gain (Antenna Gain) of Planar Antenna> FIG. 5 is a diagram showing the relationship between the frequency and the gain (antenna gain) of the planar antenna 1 according to the first embodiment. In FIG. 5, the frequency f f is the resonance frequency (Front active) when the gain on the first radiation surface 4a side (front side) of the planar antenna 1 is maximized, and the frequency f b represents the resonance frequency (Back active) when the gain on the second radiation surface 5a side (rear side) of the planar antenna 1 is maximized, respectively. The first radiation surface 4a and the second radiation surface 5a can switch their respective radiation patterns by changing the frequency. The first antenna conductor layer 4 and the second antenna conductor layer 5 have different resonance frequencies from each other.

[0036] <Power Feeding Unit> Referring to FIGS. 1 to 4 together, the first antenna conductor layer 4 and the second antenna conductor layer 5 are connected to a common power feeding unit 6. Although not shown, one end (corresponding to the power feeding point) of a power feeding line for feeding power to the first antenna conductor layer 4 and the second antenna conductor layer 5 is connected to the power feeding unit 6. The other end of the power feeding line is connected to an external device (not shown). For example, a switching signal of the operating frequency may be sent from the external device to the power feeding unit 6.

[0037] <Branch Circuit Unit> The planar antenna 1 further includes a branch circuit section 7 that distributes the current from the power feeding section 6. The branch circuit section 7 has a common section, a first end branched from the common section to one side, and a second end branched from the common section to the other side. The common section corresponds to the portion connected to the power feeding section 6 in the branch circuit section 7. The branch circuit section 7 is formed in a T shape in plan view. The branch circuit section 7 is formed in a shape that extends from the center in the x direction of the +y end edge of the first surface 21a of the first layer 21 to the -y side in plan view and then branches and extends to both sides in the x direction. In the branch circuit section 7, the portions that branch and extend to both sides in the x direction in plan view gradually increase in width in the y direction from the center side in the x direction toward the outside in the x direction.

[0038] <Configuration of the First Antenna Conductor Layer> The first antenna conductor layer 4 includes a first patch portion 40 and a first transmission line portion 41 that connects the first end of the branch circuit section 7 and the first patch portion 40.

[0039] In the example of the figure, for as long as there is the first transmission line portion 41, in plan view, the first patch portion 40 is arranged at a position shifted to the -y side from the center of the first surface 21a. Note that the arrangement of the first patch portion 40 is not limited to the above and can be changed according to the design specifications. The first patch portion 40 is in a shape smaller in size than the first layer 21 in plan view.

[0040] In plan view, the first transmission line portion 41 is arranged at a position on the +y side and the -x side rather than the center of the first surface 21a. In plan view, the first transmission line portion 41 extends from the first end on the -x end side of the branch circuit section 7 to the -x side, then extends to the -y side so as to curve toward the -x side, and then extends to the +x side toward the center side in the x direction, and then extends to the +y end side of the first patch portion 40. The first transmission line portion 41 extends with a uniform width from the first end on the -x end side of the branch circuit section 7 to the +y end side of the first patch portion 40 in plan view.

[0041] <Configuration of the Second Antenna Conductor Layer> The second antenna conductor layer 5 includes a second patch portion 50 and a second transmission line portion 51 that connects the second end, which is different from the first end of the branch circuit section 7, and the second patch portion 50.

[0042] In the example of the figure, as long as there is the second transmission line portion 51, in plan view, the second patch portion 50 is disposed at a position shifted from the center of the second surface 22a toward the -y side. Note that the arrangement of the second patch portion 50 is not limited to the above, and can be changed according to the design specifications. The second patch portion 50 is rectangular in shape and smaller in size than the second layer 22 in plan view.

[0043] In plan view, the second transmission line portion 51 is disposed at a position on the +y side and +x side from the center of the second surface 22a. In plan view, the second transmission line portion 51 extends from the second end on the +x end side of the branch circuit portion 7 toward the +x side, then extends toward the -y side so as to curve toward the +x side, and then extends toward the -x side toward the center side in the x direction, and then extends to the +y end side of the second patch portion 50. The second transmission line portion 51 extends with a uniform width from the second end on the +x end side of the branch circuit portion 7 to the +y end side of the second patch portion 50 in plan view.

[0044] <Notch> At least one of the first patch portion 40 and the second patch portion 50 is formed with a notch 42 for shifting the resonance frequency. The notch 42 is formed in the first patch portion 40. In the example of the figure, the notch 42 is formed on both sides in the x direction of the portion where the first transmission line portion 41 is connected in the first patch portion 40. No notch for shifting the resonance frequency is formed in the second patch portion 50. Note that the formation mode of the notch for shifting the resonance frequency is not limited to the above, and can be changed according to the design specifications.

[0045] <Through hole> A through hole 8 passing through a part of the branch circuit portion 7 is formed in the planar antenna 1. In plan view, the through hole 8 is disposed at a position shifted to the +y side and +x side from the center of the planar antenna 1. The through hole 8 is formed so as to penetrate the first layer 21, the ground conductor layer 3, and the second layer 22. The through hole 8 is formed in a rectangular shape in plan view. In plan view, the inner edge of the through hole 8 is separated from the outer edge of the branch circuit portion 7.

[0046] <Design example of planar antenna> FIG. 6 is a diagram showing an example of dimensions including a plan view and two side views of the planar antenna 1 according to the first embodiment as viewed from the first radiation surface 4a side. FIG. 7 is a diagram showing an example of dimensions including a plan view of the planar antenna 1 according to the first embodiment as viewed from the second radiation surface 5a side. FIG. 8 is a diagram showing an example of dimensions including a plan view of the branch circuit portion 7 according to the first embodiment. Hereinafter, a design example of the planar antenna 1 according to the first embodiment will be described. In FIGS. 6 to 8 and the following equations, A: calculation variable, B: calculation variable, d: patch notch length (corresponding to the y-direction dimension of the notch 42 of the patch), e: T-branch notch length (corresponding to the y-direction dimension of the notch of the branch circuit portion 7), g: patch notch width (corresponding to the x-direction dimension of the notch 42 of the patch), W: normal microstrip line width (corresponding to the width dimension orthogonal to the direction in which the transmission line portion extends in plan view), W’: microstrip line width immediately after the T-branch (corresponding to the y-direction dimension on the center side in the x-direction of the portions that branch and extend on both sides in the x-direction in plan view of the branch circuit portion 7), W p : patch width (corresponding to the x-direction dimension of the patch portions 40, 50), L: width of the hole for conduction (corresponding to the x-direction dimension of the through hole 8), L p : patch length (corresponding to the y-direction dimension of the patch portions 40, 50), ΔL: calculation variable, ε reff : effective dielectric constant, ε r : relative dielectric constant of the dielectric layer 2, t: thickness of the dielectric layer 2 (corresponding to the z-direction dimension of each of the first layer 21 and the second layer 22) are shown respectively.

[0047] First, variables A and B necessary for calculation are obtained from the following equations (1) and (2).

[0048]

Equation

[0049] Next, the following equations (3) and (4) are calculated, and an appropriate equation is selected from the values of W / t to determine the microstrip line width W.

[0050]

Equation

[0051] In the case of a two-sided patch antenna where one power supply is branched to the front and back surfaces, when the microstrip line is branched in three directions including the original line, it is preferable that all three directions are not affected by reflections from the other two directions. As one of the means, there is a branch circuit that distributes power by adjusting the line width called a T-branch (see Fig. 8).

[0052] Let the total power be P all Then, the power supplied to the left and right of the T-branch circuit is expressed by the following formula (5) using the distribution coefficient K.

[0053]

Equation

[0054] When distributing power, the impedances Z1 and Z2 corresponding to the line widths W1 and W2 immediately after the branch are calculated by the following formula (6).

[0055]

Equation

[0056] When distributing power evenly, K = 0.5, and it is expressed by the following formula (7).

[0057]

Equation

[0058] In order to obtain the microstrip line width in a two-sided patch antenna, by substituting the design values of the antenna into formulas (1) and (3) and performing calculations, the following formula (8) is obtained.

[0059]

Equation

[0060] Next, by substituting into Eqs. (2) and (4) and performing calculations, the following Eq. (9) is obtained.

[0061]

Equation

[0062] From this result, Eq. (9) is adopted to obtain W. The width W’ immediately after the T-branch is similarly obtained using Eqs. (5), (6), and (7).

[0063] Regarding the patch portion, first, the horizontal width W p of the patch is obtained by the following Eq. (10).

[0064]

Equation

[0065] Next, the effective dielectric constant ε reff is obtained by the following Eq. (11).

[0066]

Equation

[0067] Then, the variable ΔL for calculation is obtained by the following Eq. (12).

[0068]

Equation

[0069] And the vertical width L p of the patch is obtained by the following Eq. (13).

[0070]

Equation

[0071] The width g of the notch of the patch is the same as W and is expressed by the following Eq. (14).

[0072]

Number

[0073] The length d of the notch for adjusting the impedance of the patch portion is obtained by the following formula (15).

[0074]

Number

[0075] <Shape deformation and recovery function> The planar antenna 1 of this embodiment has a shape deformation and 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 an arbitrary 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.

[0076] The temperature transition point of the shape memory polymer corresponds to the glass transition temperature Tg of the shape memory polymer. The elastic modulus of the shape memory polymer varies greatly at temperatures around the glass transition temperature Tg. The elastic modulus of the shape memory polymer is relatively high at temperatures below Tg and relatively low at temperatures above Tg. The elastic modulus of the shape memory polymer depends on temperature.

[0077] The shape memory polymer easily deforms with a small stress at a high temperature exceeding a predetermined temperature with respect to Tg. In this case, when the maximum strain is constrained to be constant and cooled to a low temperature below the predetermined temperature with respect to Tg, the stress increases as resistance to thermal shrinkage (recovery stress). When unloading is performed while maintaining the 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, when heated from the state of low-temperature unloading to a high temperature exceeding the predetermined temperature with respect to Tg under no load, the strain disappears and returns to the original shape (shape recoverability).

[0078] In this way, the shape memory polymer has shape fixability and shape recoverability. That is, when the shape memory polymer is cooled below Tg while maintaining the shape deformed at a temperature exceeding Tg, it solidifies in that shape. When heated again to a temperature exceeding Tg, it returns to the memorized shape.

[0079] <Function and Effect> As described above, the planar antenna 1 of the present embodiment includes a ground conductor layer 3, a dielectric layer 2 including a first layer 21 and a second layer 22 disposed outside the ground conductor layer 3 via the ground conductor layer 3, a first antenna conductor layer 4 disposed on a first surface 21a of the first layer 21 opposite to the ground conductor layer 3 and having a first radiation surface 4a, and a second antenna conductor layer 5 disposed on a second surface 22a of the second layer 22 opposite to the ground conductor layer 3 and having a second radiation surface 5a facing opposite to the first radiation surface 4a. According to this configuration, since the first radiation surface 4a and the second radiation surface 5a are arranged to face each other, the radiation and reception of radio waves at the first radiation surface 4a and / or the radiation and reception of radio waves at the second radiation surface 5a can be performed without changing the posture. Therefore, it is possible to provide the planar antenna 1 that can radiate and receive radio waves in opposite directions without the need to change the posture.

[0080] In the present embodiment, the first antenna conductor layer 4 and the second antenna conductor layer 5 have different resonance frequencies from each other. According to this configuration, no actuation (operating a machine by electricity, magnetism, etc.) for changing the posture is required. In the present embodiment, the radiation patterns of the first radiation surface 4a and the second radiation surface 5a can be switched by changing the frequency. Therefore, compared with the case of providing the above actuation, the radiation patterns of the first radiation surface 4a and the second radiation surface 5a can be switched in a short time.

[0081] In the present embodiment, the first antenna conductor layer 4 and the second antenna conductor layer 5 are electrically connected to each other. According to this configuration, the structure of the planar antenna 1 can be simplified. In the present embodiment, the first antenna conductor layer 4 and the second antenna conductor layer 5 are connected to a common power feeding portion 6. Therefore, it is easier to simplify as compared with the case where the first antenna conductor layer 4 and the second antenna conductor layer 5 are each connected to a separate power feeding portion 6 (when two power feeding portions 6 are provided).

[0082] In the present embodiment, the planar antenna 1 further includes a branch circuit portion 7 having a common portion, a first end branched from the common portion to one side, and a second end branched from the common portion to the other side. The first antenna conductor layer 4 includes a first patch portion 40 and a first transmission line portion 41 that connects the first end of the branch circuit portion 7 and the first patch portion 40. The second antenna conductor layer 5 includes a second patch portion 50 and a second transmission line portion 51 that connects the second end of the branch circuit portion 7 and the second patch portion 50. According to this configuration, the current from the power feeding portion 6 can be guided to the first patch portion 40 through the branch circuit portion 7 and the first transmission line portion 41, and can also be guided to the second patch portion 50 through the branch circuit portion 7 and the second transmission line portion 51.

[0083] In the present embodiment, the branch circuit portion 7 is formed in a T shape in plan view. According to this configuration, when the branch circuit portion 7 branches the microstrip line in three directions including the original line, it is possible to prevent the influence of reflection from the other two directions in all three directions.

[0084] In the present embodiment, a notch 42 for shifting the resonance frequency is formed in the first patch portion 40. According to this configuration, by shifting the resonance frequency by the notch 42, it is possible to realize switching of the operating frequency.

[0085] In the present embodiment, a through hole 8 through which a part of the branch circuit portion 7 passes is formed in the planar antenna 1. According to this configuration, a part of the branch circuit portion 7 can be guided from the side of the first transmission line portion 41 to the side of the second transmission line portion 51 through the through hole 8.

[0086] In this embodiment, the dielectric layer 2 is composed mainly of a shape memory polymer. According to this configuration, the planar antenna 1 can be deformed into an arbitrary shape by heating and an external force above the temperature transition point of the shape memory polymer. 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, a planar antenna 1 having a shape deformation / recovery function can be provided.

[0087] Since the planar antenna 1 of this embodiment has a shape deformation / recovery function because the dielectric layer 2 is composed mainly of a shape memory polymer, it is possible to obtain resistance to deformation, which is a problem with lightweight antennas, and to avoid instability of the antenna gain. The change in the antenna gain due to this deformation becomes more significant at higher frequencies, so it is effective for antenna design, which is a basic tool in research fields such as Society 5.0 and 6.0. Also, by making it two-sided, switching of the radiation surface in the 180-degree to 360-degree direction can be realized simply by switching the frequency without any actuation. As a result, in the case of space observation, the time required for changing the attitude and stabilizing the attitude of the observation satellite (for example, a time of the order of 1 week) can be omitted. This means that the number of observations in a year can be increased, leading to a significant reduction in the waiting time for space physicists.

[0088] <Second Embodiment> FIG. 9 is a plan view of the planar antenna 201 according to the second embodiment as viewed from the first radiation surface 4a side. FIG. 10 is a plan view of the planar antenna 201 according to the second embodiment as viewed from the second radiation surface 5a side. Hereinafter, the planar antenna 201 according to the second embodiment will be described with reference to FIGS. 9 and 10. In the configurations shown in FIGS. 9 and 10, the same components as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0089] At least a part of the dielectric layer 202 has a hollow structure 225. The hollow structure 225 is a structure formed with air inside the dielectric layer 202 and corresponds to the hollowed-out portion of the dielectric layer 202.

[0090] In plan view, the dielectric layer 202 has a solid structure 226 at least at a portion overlapping with the first patch portion 40 of the first antenna conductor layer 4. The solid structure 226 is a structure where the dielectric layer 202 itself exists and corresponds to the portion of the dielectric layer 202 other than the hollowed-out portion.

[0091] In plan view, a part of the dielectric layer 202 is square. Specifically, the dielectric layer 202 includes a square portion 202A formed in a square shape in plan view and a rectangular portion 202B formed in a rectangular shape in plan view. The first patch portion 40 is formed in the square portion 202A. The rectangular portion 202B is connected to the +y edge of the square portion 202A in plan view. The rectangular portion 202B is longer than the square portion 202A in both outer sides in the x direction in plan view. The branch circuit portion 7 is formed in the rectangular portion 202B. In plan view, at least a part of the hollow structure 225 is arranged at positions that are four-fold symmetric with the center of the square portion 202A of the dielectric layer 202 as the axis of symmetry.

[0092] As described above, in the present embodiment, at least a part of the dielectric layer 202 has a hollow structure 225. According to this configuration, it is possible to reduce the weight as compared with the case where the entire dielectric layer 202 is solid.

[0093] In the present embodiment, in plan view, the dielectric layer 202 has a solid structure 226 at least at a portion overlapping with the first patch portion 40 of the first antenna conductor layer 4. According to this configuration, since the dielectric layer 202 has a solid structure 226 at the portion overlapping with the first patch portion 40 of the first antenna conductor layer 4 in plan view, it is possible to significantly reduce the mass while accepting a slight sacrifice in rigidity.

[0094] In this embodiment, in a plan view, a part of the dielectric layer 202 is square. In a plan view, at least a part of the hollow structure 225 is arranged at a position that is rotationally symmetric four times about the center of the square portion 202A of the dielectric layer 202 as the axis of symmetry. According to this configuration, a more suitable shape can be realized in achieving high rigidity and weight reduction of the planar antenna 201.

[0095] <Modification Example> In the above-described embodiment, an example in which the first antenna conductor layer and the second antenna conductor layer have different resonance frequencies from each other has been described, but the present invention is not limited to this. For example, the first radiation surface and the second radiation surface may not be configured such that their respective radiation patterns can be switched by changing the frequency. For example, the radiation patterns of the first radiation surface and the second radiation surface may be configured to be switchable by an actuation for changing the posture (operating a machine by electricity, magnetism, etc.). The switching mode of the radiation pattern can be changed according to the design specifications.

[0096] In the above-described embodiment, an example in which the first antenna conductor layer and the second antenna conductor layer are electrically connected to each other has been described, but the present invention is not limited to this. For example, the first antenna conductor layer and the second antenna conductor layer may not be connected to a common power supply unit. For example, the first antenna conductor layer and the second antenna conductor layer may be connected to separate power supply units. For example, the planar antenna may include two power supply units. The connection mode of the first antenna conductor layer and the second antenna conductor layer to the power supply unit can be changed according to the design specifications.

[0097] In the above-described embodiments, the planar antenna further includes a branching circuit portion having a common portion, a first end branched from the common portion to one side, and a second end branched from the common portion to the other side. The first antenna conductor layer includes a first patch portion and a first transmission line portion connecting the first end of the branching circuit portion and the first patch portion. The second antenna conductor layer includes a second patch portion and a second transmission line portion connecting the second end of the branching circuit portion and the second patch portion. An example has been described, but the present invention is not limited thereto. For example, the first antenna conductor layer and the second antenna conductor layer may be directly connected to the power supply portion. For example, the planar antenna may not include a branching circuit portion. The installation mode of the branching circuit portion can be changed according to the design specifications.

[0098] In the above-described embodiments, an example in which the branching circuit portion is formed in a T shape in plan view has been described, but the present invention is not limited thereto. For example, the branching circuit portion may be formed in a shape other than a T shape in plan view. For example, the branching circuit portion may be formed in a U shape in plan view. The shape of the branching circuit portion in plan view can be changed according to the design specifications.

[0099] In the above-described embodiments, an example in which a notch for shifting the resonance frequency is formed in at least one of the first patch portion and the second patch portion has been described, but the present invention is not limited thereto. For example, notches may not be formed in the first patch portion and the second patch portion. The formation mode of the notch can be changed according to the design specifications.

[0100] In the above-described embodiments, an example in which a through hole passing through a part of the branching circuit portion is formed in the planar antenna has been described, but the present invention is not limited thereto. For example, a part of the branching circuit portion may be provided so as to bypass the planar antenna (such as a dielectric layer). For example, a through hole may not be formed in the planar antenna. The formation mode of the through hole can be changed according to the design specifications.

[0101] In the above-described embodiments, the dielectric layer has been described by taking an example in which it is composed mainly of a shape memory polymer, but it is not limited thereto. For example, the dielectric layer may not be composed mainly of a shape memory polymer. The configuration mode of the dielectric layer can be changed according to the design specifications.

[0102] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to these, and additions, omissions, substitutions, and other changes can be made without departing from the spirit of the present invention, and it is also possible to appropriately combine the above-described embodiments.

[0103] (Appendix 1) A ground conductor layer, A dielectric layer including a first layer and a second layer disposed outside the ground conductor layer via the ground conductor layer, A first antenna conductor layer disposed on a first surface of the first layer opposite to the ground conductor layer and having a first radiation surface, A second antenna conductor layer disposed on a second surface of the second layer opposite to the ground conductor layer and having a second radiation surface facing opposite to the first radiation surface, A planar antenna.

[0104] (Appendix 2) The first antenna conductor layer and the second antenna conductor layer have different resonance frequencies from each other, The planar antenna according to Appendix 1.

[0105] (Appendix 3) The first antenna conductor layer and the second antenna conductor layer are electrically connected to each other, The planar antenna according to Appendix 1 or 2.

[0106] (Appendix 4) Further comprising a branching circuit portion having a common portion, a first end branched from the common portion to one side, and a second end branched from the common portion to the other side, The first antenna conductor layer is A first patch portion, A first transmission line section that connects the first end of the branch circuit section to the first patch section, The second antenna conductor layer, A second patch section, A second transmission line section that connects the second end of the branch circuit section to the second patch section, The planar antenna according to Appendix 2 or 3.

[0107] (Appendix 5) At least one of the first patch section and the second patch section is formed with a notch for shifting the resonance frequency, The planar antenna according to Appendix 4.

[0108] (Appendix 6) The dielectric layer is composed mainly of a shape memory polymer, The planar antenna according to any one of Appendices 1 to 5.

Example

[0109] Hereinafter, the planar antenna according to the above embodiment of the present invention will be specifically described with reference to examples. Note that the following examples are specific examples to which the present invention is applied and do not limit the present invention.

[0110] FIG. 11 is a perspective view of the planar antenna of the example. FIG. 12 is a side view showing the radiation pattern of the planar antenna of the example at frequency f f FIG. 13 is a side view showing the radiation pattern of the planar antenna of the example at frequency f b FIG. 14 is a diagram showing the analysis result of the relationship between the frequency and gain of the planar antenna of the example.

[0111] (Example) As shown in FIG. 11, the planar antenna of the embodiment includes a ground conductor layer, a dielectric layer including a first layer and a second layer disposed outside the ground conductor layer via the ground conductor layer, a first antenna conductor layer disposed on a first surface opposite to the ground conductor layer of the first layer and having a first radiation surface, and a second antenna conductor layer disposed on a second surface opposite to the ground conductor layer of the second layer and having a second radiation surface facing opposite to the first radiation surface. The first radiation surface and the second radiation surface are each configured such that their radiation patterns can be switched by changing the frequency. The first antenna conductor layer and the second antenna conductor layer are connected to a common feeding portion. The planar antenna further includes a branch circuit portion for distributing the current from the feeding portion. The first antenna conductor layer includes a first patch portion and a first transmission line portion connecting the first end of the branch circuit portion and the first patch portion. The second antenna conductor layer includes a second patch portion and a second transmission line portion connecting a second end different from the first end of the branch circuit portion and the second patch portion. The branch circuit portion is formed in a T shape in plan view. A notch for shifting the resonance frequency is formed in the first patch portion, and no notch for shifting the resonance frequency is formed in the second patch portion. A through hole passing through a part of the branch circuit portion is formed in the planar antenna. A dielectric layer composed mainly of a shape memory polymer (corresponding to the configuration shown in FIG. 1) was prepared.

[0112] (Evaluation Results) The gain (antenna gain) of the planar antenna was measured by an analysis experiment. The evaluation results and the like are shown in FIGS. 12 to 14.

[0113] Referring together to FIGS. 12 to 14, according to the planar antenna of the embodiment, it was confirmed that the first radiation surface and the second radiation surface can switch their respective radiation patterns by changing the frequency. And it was confirmed that the pattern is biased toward the y-direction plus (+) side (feeding point side) in each radiation pattern.

Description of Reference Numerals

[0114] 1,201... planar antenna, 2,202... dielectric layer, 3... ground conductor layer, 4... first antenna conductor layer, 4a... first radiation surface, 5... second antenna conductor layer, 5a... second radiation surface, 6... feeding section, 7... branch circuit section, 8... through hole, 21... first layer, 21a... first surface, 22... second layer, 22a... second surface, 40... first patch section, 41... first transmission line section, 42... notch, 50... second patch section, 51... second transmission line section

Claims

1. A ground conductor layer; a dielectric layer including a first layer and a second layer disposed on an outer side of the ground conductor layer with the ground conductor layer interposed therebetween; a first antenna conductor layer disposed on a first surface of the first layer opposite to the ground conductor layer, the first antenna conductor layer having a first radiation surface; a second antenna conductor layer disposed on a second surface of the second layer opposite to the ground conductor layer and having a second radiation surface facing away from the first radiation surface; At least a portion of the dielectric layer has a hollow structure, In a plan view, the portion of the dielectric layer is square; In the plan view, at least a part of the hollow structure is disposed at a position that is four-fold symmetrical with respect to a center of the square portion of the dielectric layer as an axis of symmetry. Flat antenna.

2. the first antenna conductor layer and the second antenna conductor layer have mutually different resonant frequencies; 2. A planar antenna as claimed in claim 1.

3. the first antenna conductor layer and the second antenna conductor layer are electrically connected to each other; 3. A planar antenna according to claim 1 or 2.

4. a branch circuit section having a common section, a first end branched from the common section in one direction, and a second end branched from the common section in the other direction; The first antenna conductor layer is A first patch unit; a first transmission line section connecting the first end of the branch circuit section and the first patch section, The second antenna conductor layer is A second patch unit; a second transmission line section connecting the second end of the branch circuit section and the second patch section, 3. A planar antenna as claimed in claim 2.

5. At least one of the first patch portion and the second patch portion is formed with a notch for shifting a resonance frequency.

5. A planar antenna according to claim 4.

6. The dielectric layer is mainly composed of a shape memory polymer.

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

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