Film antenna and antenna device

Abstract

This film antenna comprises a first conductor part fed with power from a power feed line. The first conductor part has a base part positioned on the power feed line side and a main body part adjacent to the base part. The outline of the base part from an end part on the power feed line side to the main body part has a shape that gradually changes.

Description

Film antenna and antenna device

[0001] The present invention relates to a film antenna and an antenna device.

[0002] Patent Document 1 describes a film antenna in which a conductor portion fed with power from a power feeder is sandwiched between films. In the film antenna described in Patent Document 1, the portion of the conductor portion facing the electrode on the power feeder side is formed in a rectangular shape.

[0003] Patent No. 5067289

[0004] However, with the film antenna described in Patent Document 1, it has been difficult to improve the characteristics over a wide band.

[0005] One example of an object of the present invention is to improve the characteristics of a film antenna over a wide band. Other objects of the present invention will become apparent from the description of this specification.

[0006] One aspect of the present invention is a film antenna comprising a first conductor portion that is fed with power from a power feed line, the first conductor portion having a root portion located on the power feed line side and a main body portion adjacent to the root portion, and the outline of the root portion from the end on the power feed line side to the main body portion having a shape that gradually changes.

[0007] According to the above aspect of the present invention, the characteristics of the film antenna can be improved over a wide band.

[0008] 1 is an explanatory diagram of an object 100A on which the antenna device 10 of the present embodiment is disposed. FIG. 2 is an explanatory diagram of an object 100B on which the antenna device 10 of the present embodiment is disposed. FIG. 3 is a plan view of the antenna device 10 of the present embodiment. FIG. 4 is an explanatory diagram showing a cross section of the antenna device 10. FIG. 5 is an explanatory diagram showing an enlarged view of a portion of a conductor 126 as viewed in the Z direction. FIG. 6 is an explanatory diagram showing a cross section of an antenna device 10A of a first modified example. FIG. 7 is a diagram explaining conditions adopted in each study case of a simulation. FIG. 8 is a plan view of an antenna device 10B in study case (1). FIG. 9 is a plan view of an antenna device 10C in study case (1). FIG. 10 is a plan view of an antenna device 10D in study case (1). FIG. 11 is a diagram showing an example of VSWR-frequency characteristics of a film antenna in study case (1). FIG. 12 is a plan view of an antenna device 10E in study case (2). FIG. 13 is a plan view of an antenna device 10F in study case (2). FIG. 14 is a plan view of an antenna device 10G in study case (2). FIG. 15 is a diagram showing an example of VSWR-frequency characteristics of a film antenna in study case (2). 1 is an explanatory diagram showing how high frequencies propagate in an overlapping portion between the conductor portion 126E and the ground portion 103. FIG. 2 is an explanatory diagram showing how high frequencies propagate in portions other than the overlapping portion between the conductor portion 126E and the ground portion 103. FIG. 3 is a graph abstractly illustrating how the characteristic impedance Z of the root portion gradually changes between Y = 0 and L. FIG. 4 is an explanatory diagram showing minute changes in the reflection coefficient Γ when the characteristic impedance Z of the root portion changes. FIG. 5 is a plan view of the antenna device 10H in study case (3). FIG. 6 is a plan view of the antenna device 10I in study case (3). FIG. 7 is a plan view of the antenna device 10J in study case (3). FIG. 8 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in study case (3). FIG. 9 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in study case (4). FIG. 10 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in study case (5). FIG. 11 is a perspective view of the antenna device 10K of the second modified example, viewed from the +Z direction. 1 is a perspective view of an antenna device 10K of a second modified example, as seen from the -Z direction side; FIG. 2 is a perspective view of an antenna device 10L of a third modified example, as seen from the +Z direction side; FIG. 3 is a perspective view of an antenna device 10L of a third modified example, as seen from the -Z direction side; and FIG. 4 is a perspective view of an antenna device 10M of a fourth modified example.Fig. 31 is an enlarged view of the dashed line portion in Fig. 30. Fig. 32 is an explanatory diagram showing a cross section of an antenna device 10M according to a fourth modified example. Fig. 33 is an explanatory diagram showing a cross section of an antenna device 10N according to a fifth modified example.

[0009] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The same or equivalent components, members, etc. shown in the drawings will be designated by the same reference numerals, and redundant explanations will be omitted where appropriate.

[0011] ==Present Embodiment== FIG. 1 is an explanatory diagram of an object 100A on which an antenna device 10 of this embodiment is disposed.

[0012] <<Definition of Directions, Etc.>> First, with reference to FIG. 1, directions, etc. in the antenna device 10 of this embodiment will be defined.

[0013] 1, directions parallel to the plane on which the power feed unit 11 (described later) of the antenna device 10 is arranged and perpendicular to each other are defined as the "+X direction" and the "+Y direction." In this embodiment, the plane on which the power feed unit 11 of the antenna device 10 is arranged is the front surface of the ground unit 103 (described later) of the antenna device 10. Furthermore, the direction perpendicular to the +X direction and the +Y direction is defined as the "+Z direction."

[0014] The +X direction, -X direction, +Y direction, -Y direction, +Z direction, and -Z direction are each directions with a fixed orientation. Rather than being directions with a fixed orientation as described above, both the +X direction and the -X direction may be simply referred to as the "X direction." Similarly, both the +Y direction and the -Y direction may be simply referred to as the "Y direction." Furthermore, both the +Z direction and the -Z direction may be simply referred to as the "Z direction." Furthermore, the Z direction may be referred to as the "vertical direction," and the direction perpendicular to the Z direction may be referred to as the "horizontal direction."

[0015] 1, the +X direction, +Y direction, and +Z direction are each represented by a line segment with an arrow to facilitate understanding of directions, etc., in the antenna device 10. Note that the intersection of these line segments with an arrow does not represent the origin of the coordinate system.

[0016] The above definitions of directions and the like are common to other embodiments in this specification unless otherwise specified.

[0017] <<Outline of Antenna Device 10 >> Next, an outline of the antenna device 10 of this embodiment will be described with reference again to FIG. 1 described above.

[0018] <Arrangement Example> As shown in Fig. 1, the antenna device 10 is an antenna device arranged on an object 100A. In the example shown in Fig. 1, the object 100A is a vehicle. Here, "vehicle" refers to a vehicle having wheels. However, the object 100A is not limited to the vehicle shown in Fig. 1, and may be a moving object that does not have wheels, such as construction machinery, agricultural machinery, a ship, an aircraft, or a drone.

[0019] The object 100A has a transparent portion 101A and an opaque portion 102A. The transparent portion 101A is a material that allows visible light or infrared light to pass through, in other words, a material that is transparent to visible light or infrared light. For example, when an internal space and an external space are separated by the transparent portion 101A, an object in the external space can be visually recognized or sensed by infrared light from the internal space through the transparent portion 101A. Conversely, an object in the internal space can be visually recognized or sensed by infrared light from the external space through the transparent portion 101A. Furthermore, the opaque portion 102A is a portion that is more difficult for visible light and infrared light to pass through than the transparent portion 101A, and is therefore more difficult for objects to be visually recognized or sensed by infrared light through the opaque portion 102A than the transparent portion 101A.

[0020] In the object 100A of this embodiment, the transmissive portion 101A is made of a material such as glass, acrylic, etc. The non-transmissive portion 102A is made of a conductive material such as metal, and is used as a ground portion of the film antenna 12 together with the external conductor side power supply portion 112 of the power supply portion 11.

[0021] In the object 100A of this embodiment, the transmissive portion 101A and the opaque portion 102A are located adjacent to each other, and the antenna device 10 of this embodiment is disposed across the transmissive portion 101A and the opaque portion 102A. In other words, the antenna device 10 of this embodiment is disposed at the boundary between the transmissive portion 101A and the opaque portion 102A.

[0022] In the example shown in Fig. 1, the transmissive portion 101A is, for example, a vehicle windshield, and the opaque portion 102A is a pillar adjacent to the windshield, for example, an A-pillar (front pillar). Alternatively, the transmissive portion 101A may be a side glass of the vehicle, and the opaque portion 102A may be a pillar adjacent to the side glass, for example, an A-pillar (front pillar) or a B-pillar (center pillar). Furthermore, for example, if the roof of the vehicle is made of glass, the transmissive portion 101A may be a roof made of glass, and the opaque portion 102A may be a vehicle body frame that supports the roof.

[0023] The object 100A on which the antenna device 10 is disposed in the above-described embodiment is a vehicle. However, the object on which the antenna device 10 is disposed may be an object other than a vehicle, as shown in FIG. 2 to be described later.

[0024] FIG. 2 is an explanatory diagram of an object 100B on which the antenna device 10 of this embodiment is disposed.

[0025] 2, the object 100B is a vending machine. The transparent portion 101B of the object 100B is, for example, an acrylic plate on the front of the vending machine, and a user of the vending machine can see product samples and the like placed inside through the acrylic plate on the front. The non-transparent portion 102B is a housing portion adjacent to the acrylic plate on the front.

[0026] <Configuration> Fig. 3 is a plan view of the antenna device 10 of this embodiment. Fig. 4 is an explanatory diagram showing a cross section of the antenna device 10. Fig. 5 is an explanatory diagram showing an enlarged view of a part of the conductor portion 126 when viewed in the Z direction.

[0027] In the following description, the object on which the antenna device 10 is placed is referred to as "object 100" to represent the above-described objects 100A and 100B. Furthermore, the transparent portion of the object 100 is referred to as "transparent portion 101" to represent the above-described transparent portion 101A and transparent portion 101B, and the non-transparent portion of the object 100 is referred to as "non-transparent portion 102" to represent the above-described non-transparent portion 102A and non-transparent portion 102B.

[0028] The antenna device 10 includes a power supply unit 11 and a film antenna 12 .

[0029] As shown in Figures 3 and 4, the power supply unit 11 is a component that includes a power supply point of the film antenna 12. When viewed in the Z direction (the normal direction to the front surface of the film antenna 12), the power supply unit 11 overlaps with the opaque portion 102. In the antenna device 10 of this embodiment, when viewed in the Z direction, the entire power supply unit 11 overlaps with the opaque portion 102. However, a portion of the power supply unit 11 may overlap with the opaque portion 102. In other words, it is sufficient that at least a portion of the power supply unit 11 overlaps with the opaque portion 102 when viewed in the Z direction. Furthermore, a portion of the film antenna 12, which will be described later, may overlap with the opaque portion 102.

[0030] The power supply unit 11 is formed of, for example, a conductor, and if it is disposed in the transmissive portion 101, it may affect the transmittance of visible light and infrared rays in the transmissive portion 101. Here, as described above, the antenna device 10 is disposed across the transmissive portion 101 and the opaque portion 102. However, by positioning at least a portion of the power supply unit 11 in the antenna device 10 so that it overlaps with the opaque portion 102, it is possible to reduce the area where the power supply unit 11 overlaps with the transmissive portion 101. In other words, it is possible to reduce the effect of the power supply unit 11 on the transmittance of visible light and infrared rays in the transmissive portion 101. Therefore, when the antenna device 10 is disposed in an object 100 having a transmissive portion 101 (for example, the vehicle or vending machine described above), it is possible to reduce the effect of the antenna device 10 on the transmittance of the transmissive portion 101 of the object 100.

[0031] Furthermore, when the object 100 on which the antenna device 10 is placed is viewed from the +Z direction side, at least a part of the power supply unit 11 can be hidden on the −Z direction side of the opaque portion 102. This makes it possible to prevent the power supply unit 11 from being visible, thereby preventing deterioration in the aesthetic appearance of the object 100 on which the antenna device 10 is placed.

[0032] The power feed unit 11 has an inner conductor side power feed unit 111 and an outer conductor side power feed unit 112. The inner conductor side power feed unit 111 is connected to the inner conductor 91 (e.g., core wire) of the coaxial cable 90. Here, the inner conductor 91 of the coaxial cable 90 is sometimes referred to as a power feed line. The outer conductor side power feed unit 112 is connected to the outer conductor 92 (e.g., ground wire) of the coaxial cable 90. When the antenna device 10 is installed in an opaque portion 102 of an object 100, which is the installation target, the outer conductor side power feed unit 112 of the power feed unit 11 is connected to the opaque portion 102 of the object 100 with adhesive or tape. In this embodiment, the power feed structure of the antenna device 10 is described as a power feed structure using the coaxial cable 90. However, the power supply structure of the antenna device 10 may be a power supply structure other than the power supply structure using the coaxial cable 90, for example, a power supply structure using a transmission line or a power supply structure using a microstrip line.

[0033] The film antenna 12 is an antenna that can be attached to the object 100. The film antenna 12 has a conductor portion 126 and a film portion 127 in the cross-sectional view shown in FIG.

[0034] The conductor portion 126 is a portion that includes a radiating element of the film antenna 12 and has a shape that corresponds to the desired frequency band of the film antenna 12. In this embodiment, the conductor portion 126 is formed with a mesh structure made of conductor wires. Furthermore, in this embodiment, the conductor portion 126 is capacitively coupled to the internal conductor side feed portion 111 of the feed portion 11 at the portion on the -Y direction side (specifically, the base portion 122, which will be described later). This allows the conductor portion 126 and the internal conductor side feed portion 111 to be electrically connected without being directly connected by solder or the like. Therefore, deformation of the film antenna 12 due to the heat of soldering or the like can be suppressed compared to when the film antenna 12 and the feed portion 11 are directly connected by solder or pressure from the pressing of a soldering iron or the like.

[0035] In this embodiment, the mesh structure of the conductor portion 126 is composed of, for example, conductor lines 128 extending in the Y direction and conductor lines 129 extending in the X direction, as shown in FIG. 5 . A plurality of conductor lines 128 are arranged in the X direction, and a plurality of conductor lines 129 are arranged in the Y direction. The area surrounded by the conductor lines 128 and 129 forms the opening 130. Here, the width W of the conductor lines 128 and 129 is preferably, for example, 30 μm. The pitch P at which the plurality of conductor lines 128 and 129 are arranged is preferably, for example, 300 μm. In this case, the size of the opening 130 surrounded by the conductor lines 128 and 129 in the X and Y directions is larger than the width W of the conductor lines 128 and 129. Conversely, the width W of the conductor lines 128 and 129 is smaller than the size of the opening 130 in the X and Y directions. Therefore, the influence of the conductor lines 128 and 129 on the transparency of the transmissive portion 101 can be reduced.

[0036] This makes it possible to suppress the influence on the transparency of the transparent portion 101 even when the film antenna 12 is placed in the transparent portion 101 of the object 100. However, the extending direction, arranging direction, pitch P, and width W of the conductor wires 128 and 129 are not limited to those shown in Fig. 5. Furthermore, the conductor portion 126 may be formed in a structure other than a mesh structure using conductor wires, as long as the influence on the transparency of the transparent portion 101 can be suppressed.

[0037] The film portion 127 is a member that covers the conductor portion 126 and is located on the +Z direction side and the −Z direction side of the conductor portion 126. In this embodiment, the film portion 127 is formed of an insulating film that is transparent to visible light or infrared light. However, the film portion 127 may also be, for example, a rust-proof coating placed on the conductor portion 126. Even in this case, the internal conductor side power supply portion 111 of the power supply unit 11 and the conductor portion 126 are not directly connected, and the internal conductor side power supply portion 111 of the power supply unit 11 and the conductor portion 126 (specifically, the base portion 122 described below) are capacitively coupled. Furthermore, the film portion 127 does not necessarily need to cover the entire conductor portion 126; a portion of the conductor portion 126 may be exposed.

[0038] The film antenna 12 and the internal conductor side power feeding portion 111 of the power feeding unit 11 are positioned so that the +Z direction surface of the film portion 127 located on the +Z direction side of the conductor portion 126 comes into contact with the −Z direction surface of the internal conductor side power feeding portion 111. Even in this case, the internal conductor side power feeding portion 111 of the power feeding unit 11 and the conductor portion 126 are not directly conductive, and the internal conductor side power feeding portion 111 of the power feeding unit 11 and the conductor portion 126 are capacitively coupled. However, the film antenna 12 and the internal conductor side power feeding portion 111 of the power feeding unit 11 may be positioned so that the +Z direction surface of the film portion 127 located on the +Z direction side of the conductor portion 126 is spaced apart from the −Z direction surface of the internal conductor side power feeding portion 111.

[0039] Film portion 127 may be arranged on only one of the +Z direction side and the −Z direction side of conductor portion 126. In this embodiment, conductor portion 126 is capacitively coupled to internal conductor side power supply portion 111 of power supply unit 11, as described above. Therefore, if film portion 127 is not arranged on the +Z direction side of conductor portion 126, internal conductor side power supply portion 111 of power supply unit 11 may be spaced apart from conductor portion 126 so that direct conduction between internal conductor side power supply portion 111 of power supply unit 11 and conductor portion 126 is not established.

[0040] 3 and 4 , the conductor portion 126 has a main body portion 121 and a root portion 122. The main body portion 121 is the main body part of the conductor portion 126 and is located adjacent to the root portion 122 on the +Y direction side. The root portion 122 is located closer to the coaxial cable 90 (feeder line side) than the main body portion 121.

[0041] As shown in Fig. 4, the main body 121 and the root portion 122 of the film antenna 12 both extend parallel to the XY plane (a plane parallel to the X and Y directions). Furthermore, the main body 121 and the root portion 122 of the film antenna 12 extend parallel to the surface on the +Z direction side of the opaque portion 102. However, the main body 121 and the root portion 122 may extend at a predetermined angle inclined with respect to the XY plane (or the surface on the +Z direction side of the opaque portion 102). Furthermore, as will be explained in a modified example described later, the boundary portion between the root portion 122 and the main body 121 may be bent.

[0042] As described above, the opaque portion 102 in this embodiment is used as a ground portion of the film antenna 12 together with the outer conductor side feeding portion 112 of the feeding unit 11. Therefore, hereinafter, the opaque portion 102 used as a ground portion may be referred to as a "ground portion 103." Here, as shown in FIG. 4 , the root portion 122 is located between the inner conductor side feeding portion 111 of the feeding unit 11 and the opaque portion 102. In this embodiment, the root portion 122 is located so as to be sandwiched between the inner conductor side feeding portion 111 of the feeding unit 11 and the opaque portion 102. In other words, in this embodiment, when viewed in the Z direction (the normal direction to the front surface of the ground portion 103), the root portion 122 of the film antenna 12 overlaps with the ground portion 103.

[0043] However, the root portion 122 of the film antenna 12 does not have to be located between the internal conductor side power supply portion 111 of the power supply portion 11 and the opaque portion 102. In other words, when viewed in the Z direction (the normal direction to the front surface of the ground portion 103), the root portion 122 of the film antenna 12 does not have to overlap (may not overlap) with the ground portion 103. Also, the conductor portion 126 may be directly powered (electrically conductive) rather than capacitively coupled. Direct power supply allows electricity to be supplied to the film antenna 12 efficiently.

[0044] As described above, in the antenna device 10 of this embodiment, for example, when the power supply portion 11 overlaps the opaque portion 102 (ground portion 103), the root portion 122 can also be positioned so as to overlap with the ground portion 103. Even in such a case, the characteristics of the film antenna 12 can be improved over a wide band, as will be described later. Therefore, by increasing the degree of freedom in the position of the root portion 122 relative to the position of the ground portion 103, the degree of freedom in the design of the antenna device 10 can be increased.

[0045] <Modifications Regarding Film Antenna Position and Power Supply Method> FIG. 6 is an explanatory diagram showing a cross section of an antenna device 10A of a first modification.

[0046] 6, in the film antenna 12A of the antenna device 10A, the end of the opaque portion 102 on the +Y direction side and the end of the root portion 122 of the conductor portion 126 on the -Y direction side are located at approximately the same position in the Y direction. In other words, when viewed in the Z direction (the normal direction to the front surface of the ground portion 103), the root portion 122 of the conductor portion 126 does not overlap with the ground portion 103. Furthermore, in the film antenna 12A of the antenna device 10A, the end of the root portion 122 of the conductor portion 126 on the -Y direction side is connected to the end of the internal conductor side feeding portion 111A of the feeding portion 11A on the +Y direction side. In other words, in the film antenna 12A of the antenna device 10A, the conductor portion 126 is directly fed (electrically conducted).

[0047] <<Outer Shape of Conductor 126>> The inventors conducted extensive research into film antennas that can achieve a wider bandwidth, and focused on the outer shape of the conductor of the film antenna. In the film antenna 12 of this embodiment, the outer shape of the base portion 122 of the conductor 126, from the end of the power supply unit 11 on the internal conductor side power supply unit 111 side (the power supply line side) to the main body 121, has a shape that gradually changes. This makes it possible to improve the characteristics of the film antenna 12 over a wide bandwidth. Details of the outer shape of the base portion 122 (details of the gradually changing shape) will be described below, along with simulation results.

[0048] In the film antenna 12 of this embodiment, the conductor portion 126 including the base portion 122 has a self-similar shape, as shown in Fig. 3 for example. Here, a self-similar shape is a shape that remains similar even when the scale (size ratio) is changed. This allows the length and width to be set in various ways according to the wavelength used in the radio wave frequency band supported by the film antenna 12, making it possible to achieve a wider bandwidth. However, the conductor portion 126 does not have to have a self-similar shape.

[0049] <<Study Case>> When the inventors considered a film antenna 12 that could achieve a wider bandwidth, in addition to consideration item 1 regarding the outer shape of the conductor portion 126, as described below, they also set consideration items 2 and 3 that took into account the aspects of the antenna device 10A of the first variant described above.

[0050] (Study item 1) Convexity of the outer contour of the conductor part Condition A: The convexity of the outer contour of the main body part and the outer contour of the base part does not change Condition B: The convexity of the outer contour of the main body part and the outer contour of the base part changes (Study item 2) Positional relationship between the ground part and the conductor part Condition C: The ground part and the conductor part do not overlap Condition D: The ground part and the conductor part overlap (Study item 3) Mode of power supply from the power supply part to the conductor part Condition E: Direct power supply (electrical conduction) Condition F: Power supply via capacitive coupling

[0051] The "convexity" of the outline in the above-mentioned study item 1 will be explained in detail in the simulation results to be described later.

[0052] Next, the inventors performed simulations by setting up multiple study cases in which the conditions for the above-mentioned study items 1 to 3 were variously changed. The conditions used in each study case and the simulation results are described below.

[0053] FIG. 7 is a diagram illustrating the conditions adopted in each study case of the simulation.

[0054] In this simulation, a total of five study cases were set: study cases (1) to (5). Regarding study item 1 (convexity of the outline of the conductor), study case (1) adopted condition A (the convexity of the outline of the main body and the outline of the base remains unchanged), while study cases (2) to (5) adopted condition B (the convexity of the outline of the main body and the outline of the base changes). Regarding study item 2 (the positional relationship between the ground and conductor), study cases (1), (3), and (5) adopted condition C (the ground and conductor do not overlap), while study cases (2) and (4) adopted condition D (the ground and conductor overlap). Regarding the above-mentioned study item 3 (mode of power supply from the power supply part to the conductor part), condition E (direct power supply (electrically conductive)) was adopted in study cases (1), (4), and (5), and condition F (power supply via capacitive coupling) was adopted in study cases (2) and (3).

[0055] <Study Case (1)> Fig. 8 is a plan view of the antenna device 10B in Study Case (1). Fig. 9 is a plan view of the antenna device 10C in Study Case (1). Fig. 10 is a plan view of the antenna device 10D in Study Case (1). Note that the reference numerals of the elements constituting the antenna device 10B are marked with B, and the reference numerals of the elements constituting the antenna device 10C are marked with C. The same applies to the other embodiments and modified examples below.

[0056] In the conductor section in study example (1), the outline of the base section from the end of the power supply section 11 on the inner conductor side power supply section 111 side (the power supply line side) to the main body section has a shape that gradually changes, and simulations were performed under the following conditions for study items 1 to 3 described above.

[0057] (Study item 1) Convexity of the outline of the conductor part Condition A: The convexity of the outline of the main body part and the outline of the base part does not change (Study item 2) Positional relationship between the ground part and the conductor part Condition C: The ground part and the conductor part do not overlap (Study item 3) Power supply mode from the power supply part to the conductor part Condition E: Direct power supply (electrical conduction)

[0058] 8, 9, and 10 show examples in which the outer shape of the conductor portion 126 in the study case (1) is changed in various ways. The antenna devices shown in Fig. 8 and 10 have in common that the convexity of the outer shape of the conductor portion 126 does not change from the end E of the conductor portion 126 on the feeder line side to the end (point P1 or point P2) on the +Y direction side (condition A of study item 1), but the manner of the convexity of the outer shape of the conductor portion 126 differs.

[0059] Here, the "convexity" of the outline of the conductor portion 126 (main body portion 121 and base portion 122) refers to the orientation of the convex portion when the outline of the conductor portion 126 is formed as a convex curve. Specifically, in the case of the conductor portion 126B shown in FIG. 8 , when a line segment (dashed line) connecting any two points (Q1 and Q2) on the outline of the conductor portion 126B is compared with the outline of the conductor portion 126B between those two points, the orientation of the convex portion is determined by the side on which the outline of the conductor portion 126B between those two points is located relative to the line segment (dashed line). In the following description, the line passing through the feeder line-side end E of the conductor portion 126 and the geometric center of the conductor portion 126 is referred to as axis A. Furthermore, the line passing through the feeder line-side end E of the conductor portion 126 and parallel to the X direction is referred to as dashed line C, and the line passing through the end of the ground portion 103 in the +Y direction and parallel to the X direction is referred to as dashed line G.

[0060] 8, the outer contour of the conductor 126B of the film antenna 12B is formed as a convex curve. In this case, when a line segment connecting any two points (Q1 and Q2) on the outer contour of the conductor 126B is compared with the outer contour of the conductor 126B itself, the outer contour of the conductor 126B is located on the side closer to the axis A with respect to the line segment. In this case, the outer contour of the conductor 126B includes a convex curve in the direction closer to the axis A.

[0061] 8 , the center of curvature CE of the circle of curvature CU of the outline of the conductor 126B is located outside the outline of the conductor 126B (i.e., on the side away from the axis A). In this case, the outline of the conductor 126B includes a curve that is convex toward the axis A.

[0062] In the antenna device 10B, the convexity of the outline of the conductor 126B does not change from the end E of the conductor 126B on the feeder line side to the end on the +Y direction side (point P1 or point P2). That is, the outline of the conductor 126B is formed as a convex curve that approaches the axis A from the end E of the conductor 126B on the feeder line side to the end on the +Y direction side (point P1 or point P2).

[0063] 9, the outer contour of the conductor portion 126C of the film antenna 12C is formed as a straight line from the end E of the conductor portion 126C on the feeder line side to the end (point P1 or point P2) on the +Y direction side. In this case, the outer contour of the conductor portion 126C does not have convexity. However, in the antenna device 10C, the convexity of the outer contour of the conductor portion 126C does not change in that the conductor portion 126C does not have convexity over its entirety.

[0064] 10 , the outer contour of the conductor 126D of the film antenna 12D is formed as a convex curve. In this case, when a line segment connecting any two points (Q1 and Q2) on the outer contour of the conductor 126D is compared with the outer contour of the conductor 126D between those two points, the outer contour of the conductor 126D between those two points is located on the side away from the axis A with respect to the line segment. In this case, the outer contour of the conductor 126D includes a convex curve in the direction away from the axis A.

[0065] 10 , the center of curvature CE of the circle of curvature CU of the outline of the conductor 126D is located inside (i.e., closer to the axis A) than the outline of the conductor 126D. In this case, the outline of the conductor 126D includes a curve that is convex in the direction away from the axis A.

[0066] In the antenna device 10D, the convexity of the outline of the conductor 126D does not change from the end E of the conductor 126D on the feeder line side to the end on the +Y direction side (point P1 or point P2). That is, the outline of the conductor 126D is formed as a curve that convexly curves in a direction away from the axis A from the end E of the conductor 126D on the feeder line side to the end on the +Y direction side (point P1 or point P2).

[0067] In the study example (1), the outline of the conductor portion, which connects the end E of the conductor portion on the power supply line side with point P1 shown in Figures 8, 9, and 10, was set using predetermined parameters, and a simulation was performed. The parameters are expressed by the following equation 1. Note that d in equation 1 corresponds to the distance from the ground portion 103 to the outline of the conductor portion in the direction along axis A, as shown in Figures 8, 9, and 10.

[0068]

[0069] In this simulation, A and C are determined so that the outline of the conductor portion 126 passes through points P1 and P2 shown in Figures 8, 9, and 10. However, in this simulation, the sizes of the conductor portion 126 in the X and Y directions, i.e., points P1 and P2, are fixed, and A > 0 and N ≥ 0. C is a constant, and variable x, which has the intersection of the feeder line side end E of the conductor portion 126 and the axis A as the origin, represents the absolute value of the distance from the origin to a point on the outline of the conductor portion 126 in a direction perpendicular to the axis A.

[0070] FIG. 11 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in the study example (1).

[0071] In Figure 11, the horizontal axis represents frequency, and the vertical axis represents voltage standing wave ratio (VSWR). The VSWR results for various variations in N in Equation 1 (N = 0.5, 1, 1.5, 2, and 5) are shown for each line type. Note that a lower VSWR indicates better antenna characteristics. In Figure 11, the film antenna 12B shown in Figure 8 represents a case where N = 0.5, the film antenna 12C shown in Figure 9 represents a case where N = 1, and the film antenna 12D shown in Figure 10 represents a case where N = 2.

[0072] As shown in Figure 11, when N is in the range of 0.5 to 2, the larger N is, the lower the VSWR value and the better the antenna characteristics are. In other words, the more the outline of the conductor part of the film antenna changes from a convex curve approaching axis A to a convex curve moving away from axis A, the better the antenna characteristics are. Furthermore, the VSWR is particularly good when N = 2. However, when N > 2, if the value of N is made too large, the outline of the conductor part of the antenna approaches a shape that does not gradually change, and the antenna characteristics deteriorate.

[0073] <Study Case (2)> Fig. 12 is a plan view of an antenna device 10E in study case (2). Fig. 13 is a plan view of an antenna device 10F in study case (2). Fig. 14 is a plan view of an antenna device 10G in study case (2). Here, dashed line B indicates a line that passes through the boundary between the base portion 122 and the main body portion 121 and is parallel to the X direction. When viewed from the +Z direction, dashed line B and dashed line G overlap, and dashed line C is located in the -Y direction with respect to dashed line B and dashed line G.

[0074] In the study example (2), simulations were performed for the above-mentioned study items 1 to 3 under the following conditions.

[0075] (Study item 1) Convexity of the outer contour of the conductor part Condition B: Convexity of the outer contour of the main body part and the outer contour of the base part changes (Study item 2) Positional relationship between the ground part and the conductor part Condition D: The ground part and the conductor part overlap (Study item 3) Power supply mode from the power supply part to the conductor part Condition F: Power is supplied via capacitive coupling

[0076] In the case study (2), when viewed in the normal direction (Z direction) of the front surface of the ground portion 103, at least a part of the base portion has an overlapping portion that overlaps with the ground portion 103. In this case, the overlapping portion functions as a transmission line that feeds power to the conductor portion. For this reason, in the overlapping portion, the gradualness of the shape of the outline of the base portion is taken into consideration in the direction along the Y direction (transmission direction).

[0077] 12 shows a comparative example in which the contour of the base portion 122E is substantially rectangular. In this case, there is a discontinuity between points (white circles) on the contour L1 in the +Y direction and points (white circles) on the contour L2 in the -Y direction. In other words, in the comparative example shown in FIG. 12, the contour of the base portion 122E does not change gradually.

[0078] On the other hand, Figures 13 and 14 show examples in which the outline of the base portion changes gradually. In the film antenna 12F of the antenna device 10F shown in Figure 13, the outline of the base portion 122F includes a convex curve in the direction away from the axis A. In the film antenna 12G of the antenna device 10G shown in Figure 14, the outline of the base portion 122G includes a convex curve in the direction approaching the axis A. Details of the parameters of the outline of the base portion shown in Figures 12 to 14 will be described later.

[0079] In study example (2), the outline of the main body is kept constant while the outline of the base is varied. That is, the outline of the main body is fixed at N = 2 in the above-mentioned formula 1, and the parameter of the outline of the base is redefined to be M = 1 / N, and a simulation was performed. The parameters in study example (2) are expressed by the following formula 2. Note that w in formula 2 corresponds to the distance between the intersection of the outline and a line that passes through a point on the outline and is perpendicular to axis A, as shown by the dashed double-headed arrows in Figures 12, 13, and 14.

[0080]

[0081] In Equation 2, A>0 and M≧0. C is a constant, and variable y represents the absolute value of the distance from the origin, which is the intersection of the feeder line side end E of the conductor portion 126 and the axis A, to a point on the outline in the direction of the axis A.

[0082] FIG. 15 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in the study example (2).

[0083] In Fig. 15, the horizontal axis represents frequency, and the vertical axis represents voltage standing wave ratio (VSWR). The VSWR results for various values ​​of M (M = 0, 0.3, 0.5, 1, 2, 5) are shown for each line type. In Fig. 15, the film antenna 12E shown in Fig. 12 represents a case where M = 0, the film antenna 12F shown in Fig. 13 represents a case where M = 0.5, and the film antenna 12G shown in Fig. 14 represents a case where M = 2.

[0084] As shown in Figure 15, the VSWR value is lower and the antenna characteristics are improved when M>0 than when M=0. In other words, when the outline of the base of the film antenna has a shape that gradually changes, the antenna characteristics are improved. Furthermore, the VSWR improves as M increases, and the antenna characteristics are improved when M>1 (e.g., film antenna 12G with M=2) than when M<1 (e.g., film antenna 12F with M=0.5). In other words, when the outline of the base of the film antenna is convex on the side approaching axis A, the antenna characteristics are improved.

[0085] However, when M>2, if the value of M is set too large, the external contour of the base of the film antenna will have a shape that does not change gradually, and the antenna characteristics will deteriorate.

[0086] Below, we will explain how high-frequency waves propagate when part of the conductor overlaps with the ground, as in the film antenna in study case (2), and then use mathematical formulas to explain how the outline of the conductor affects the antenna characteristics of the film antenna.

[0087] Fig. 16 is an explanatory diagram showing how high frequency waves propagate in the overlapping portion between the conductor portion 126E and the ground portion 103. Fig. 17 is an explanatory diagram showing how high frequency waves propagate in portions other than the overlapping portion between the conductor portion 126E and the ground portion 103.

[0088] 16 and 17 show the propagation of high-frequency waves using the above-mentioned film antenna 12E (see FIG. 12) as an example. Note that FIG. 16 is a view from the X direction, and FIG. 17 is a view from the Z direction, with the transmission direction TR indicated by a hollow arrow and the vibration direction EF of the electric field during high-frequency wave propagation indicated by a double-headed arrow.

[0089] As shown in FIG. 16 , in the overlapping portion between the conductor portion 126E and the ground portion 103, an electric field propagates while oscillating in the Z direction (the direction connecting the conductor portion 126E and the ground portion 103) between the conductor portion 126E and the ground portion 103. This propagation behavior is similar to that of a transmission line such as a microstrip line. On the other hand, as shown in FIG. 17 , in the portion other than the overlapping portion between the conductor portion 126E and the ground portion 103, the positional relationship between the outline of the conductor portion 126E and the ground portion 103 changes, so that the electric field propagates along the gap defined by the distance d between the outline of the conductor portion 126E and the ground portion 103, approximately in the XY plane. This propagation is similar to that in a radiating element of an antenna, since the electric field radiates while propagating along the gap. As such, the propagation behavior of high-frequency waves in the overlapping portion between the conductor portion 126E and the ground portion 103 and the portion other than the overlapping portion between the conductor portion 126E and the ground portion 103 exhibits different characteristics.

[0090] Fig. 18 is a graph that abstractly shows how the characteristic impedance Z of the base portion gradually changes between Y = 0 and L. Fig. 19 is an explanatory diagram that shows the minute changes in the reflection coefficient Γ when the characteristic impedance Z of the base portion changes.

[0091] 18 and 19 are graphs abstracted from the perspective of characteristic impedance to explain the behavior of each study case, including the above-mentioned study case (2). In FIG. 18, Z0 represents the characteristic impedance of the power supply section, ZL represents the load impedance of the main body at the conductor section, and the characteristic impedance of the root section is shown as gradually changing between Y = 0 and L. In FIG. 19, the minute change between Y = 0 and L is shown, and the minute change in the reflection coefficient Γ when the characteristic impedance changes from Z to Z + ΔZ in the minute section from y to y + Δy is represented as ΔΓ. Here, the minute change ΔΓ in the reflection coefficient Γ can be expressed as Equation 3 below. Equation 3 shows that the minute change ΔΓ in the reflection coefficient Γ is inversely proportional to the characteristic impedance Z within the minute section and proportional to the change in the characteristic impedance ΔZ.

[0092]

[0093] 12, 13, and 14, consider the change ΔZ in the characteristic impedance of the base portion 122 near the above-mentioned dashed line B. When the conductor portion 126 and the ground portion 103 overlap, the distance w on the main body portion 121 side has a certain magnitude near the dashed line B, and in order to reduce the change ΔZ in the characteristic impedance, the base portion 122 must also be connected at the same distance w. Here, the general equation expressing the relationship between the characteristic impedance Z, inductance L, and capacitance C is expressed as the following Equation 4, and the general equation expressing the relationship between the dielectric constant ε, area S, and spacing d of capacitance C is expressed as the following Equation 5.

[0094]

[0095]

[0096] In this case, the area S is the area of ​​the overlapping portion between the root portion 122 and the ground portion 103, and when the change is approximated by a triangle, the change ΔS in the area S is expressed by the following equation 6 using the above-mentioned equation 2.

[0097]

[0098] From the above, the amount of change in characteristic impedance ΔZ can be expressed as in the following Equation 7. Note that the above-mentioned Equations 2, 4, 5, and 6 are used in the calculation process.

[0099]

[0100] Furthermore, near the broken line B, y is considered to be sufficiently large with respect to Δy, and the change in characteristic impedance ΔZ asymptotically approaches the function expressed by the following equation 8.

[0101]

[0102] According to the function expressed by Equation 8, M is related to the degree of y, and for the same value of y, the larger M is, the smaller ΔZ becomes. For example, when y is sufficiently large, y^-2 is smaller than y^-1. Furthermore, if ΔZ is small, the minute change ΔΓ in the reflection coefficient Γ also becomes small.

[0103] From the above explanation, when the root portion 126 and the ground portion 103 overlap, the larger the parameter M, the smaller the minute change ΔΓ in the reflection coefficient Γ near the dashed line B becomes, and the smaller the VSWR can also be made, and this tendency is also shown in the results of FIG. 15.

[0104] <Study Case (3)> Fig. 20 is a plan view of an antenna device 10H in study case (3). Fig. 21 is a plan view of an antenna device 10I in study case (3). Fig. 22 is a plan view of an antenna device 10J in study case (3). When viewed from the +Z direction, dashed line B overlaps, and dashed lines C and G overlap and are located in the -Y direction with respect to dashed line B.

[0105] In the study example (3), simulations were performed for the above-mentioned study items 1 to 3 under the following conditions.

[0106] (Study item 1) Convexity of the outline of the conductor part Condition B: Convexity of the outline of the main body part and the outline of the base part changes (Study item 2) Positional relationship between the ground part and the conductor part Condition C: The ground part and the conductor part do not overlap (Study item 3) Power supply mode from the power supply part to the conductor part Condition F: Power is supplied via capacitive coupling

[0107] In the case of study (3), when viewed in the normal direction (Z direction) of the front surface of the ground portion 103, the base portion does not overlap with the ground portion 103. In this case, the base portion functions as a radiating element of the film antenna together with the main body portion. For this reason, the gradualness of the shape of the outline of the base portion is considered in the direction along the X direction.

[0108] 20 shows a comparative example in which the shape of the base portion 122H is substantially rectangular. In this case, there is a discontinuity between a point (shown as a white circle) on the outline L3 in the −X direction and a point (shown as a white circle) on the outline L4 in the +X direction. In other words, in this comparative example, the outline of the base portion 122H does not change gradually.

[0109] On the other hand, Figures 21 and 22 show examples in which the outline of the base portion changes gradually. In the film antenna 12I of the antenna device 10I shown in Figure 21, the outline of the base portion 122I includes a convex curve in the direction away from the axis A. In the film antenna 12J of the antenna device 10J shown in Figure 22, the outline of the base portion 122J includes a convex curve in the direction approaching the axis A. Details of the parameters of the outline of the base portions shown in Figures 20 to 22 will be described later.

[0110] In study example (3), the outline of the main body is kept constant while the outline of the base is varied. That is, the outline of the main body is fixed at N = 2, and the parameters of the outline of the base are redefined to M = 1 / N, and a simulation is performed. The parameters in study example (3), like study example (2), are expressed by Equation 2. Note that w in Equation 2 corresponds to the distance between the intersection of the outline and a line that passes through a point on the outline and is perpendicular to axis A, as shown by the dashed double-headed arrows in Figures 20, 21, and 22.

[0111] FIG. 23 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in the study example (3).

[0112] In Fig. 23, the horizontal axis represents frequency, and the vertical axis represents voltage standing wave ratio (VSWR). The VSWR results for various values ​​of M (M = 0, 0.3, 0.5, 1, 2, 5) are shown for each line type. In Fig. 23, the film antenna 12H shown in Fig. 20 represents a case where M = 0, the film antenna 12I shown in Fig. 21 represents a case where M = 0.5, and the film antenna 12J shown in Fig. 22 represents a case where M = 2.

[0113] As shown in Figure 23, the VSWR value is lower and the antenna characteristics are improved when M>0 than when M=0. In other words, when the outline of the base of the film antenna has a shape that gradually changes, the antenna characteristics are improved. In the study example (3), the VSWR is generally good when M>0, but the VSWR is better when M<1 (e.g., film antenna 12I with N=0.5) than when M>1 (e.g., film antenna 12J with N=2). In other words, when the outline of the base of the film antenna is convex on the side away from axis A, the antenna characteristics are improved.

[0114] However, when M>2, if the value of M is set too large, the contour of the base of the film antenna will have a shape that does not change gradually, and the VSWR will deteriorate.

[0115] <Study Case (4)> In Study Case (4), simulations were performed under the following conditions for Study Items 1 to 3 described above. Note that, compared to Study Case (2), Study Case (4) shares Study Item 1 (convexity of the outer shape of the conductor) and Study Item 2 (positional relationship between the ground portion and the conductor portion), and Study Item 3 (mode of power supply from the power supply portion to the conductor portion) is a direct power supply (electrical conduction). For this reason, illustrations of specific film antennas are omitted.

[0116] (Study item 1) Convexity of the outline of the conductor part Condition B: Change in convexity between the outline of the main body part and the outline of the base part (Study item 2) Positional relationship between the ground part and the conductor part Condition D: The ground part and the conductor part overlap (Study item 3) Power supply mode from the power supply part to the conductor part Condition E: Direct power supply (electrical conduction)

[0117] In the case study (4), when viewed in the normal direction (Z direction) of the front surface of the ground portion 103, at least a part of the base portion has an overlapping portion that overlaps with the ground portion 103. In this case, the overlapping portion functions as a transmission line that feeds power to the conductor portion, similar to the case study (2). For this reason, in the overlapping portion, the gradualness of the shape of the outline of the base portion is taken into consideration in the direction along the Y direction (transmission direction).

[0118] FIG. 24 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in the study example (4).

[0119] 24, the horizontal axis represents frequency and the vertical axis represents voltage standing wave ratio (VSWR). The results of VSWR when M is changed variously (M=0, 0.3, 0.5, 1, 2, 5) are shown for each line type.

[0120] As shown in Figure 24, the VSWR is improved when M>0 than when M=0. In other words, the VSWR is improved when the outline of the base of the film antenna has a shape that gradually changes. Furthermore, the VSWR is improved as M increases, and the VSWR is improved when M>1 (e.g., M=2) than when N<1 (e.g., M=0.5). In other words, the VSWR is improved when the outline of the base of the film antenna is convex on the side approaching the axis A.

[0121] However, when M>2, if the value of M is set too large, the contour of the base of the film antenna will have a shape that does not change gradually, and the VSWR will deteriorate.

[0122] <Study Case (5)> In Study Case (5), simulations were performed under the following conditions for Study Items 1 to 3 described above. Note that, compared to Study Case (3), Study Case (5) shares Study Item 1 (convexity of the outer shape of the conductor) and Study Item 2 (positional relationship between the ground portion and the conductor portion), and Study Item 3 (mode of power supply from the power supply portion to the conductor portion) is a direct power supply (electrical conduction). For this reason, illustrations of specific film antennas are omitted.

[0123] (Study item 1) Convexity of the outline of the conductor part Condition B: Change in convexity between the outline of the main body part and the outline of the base part (Study item 2) Positional relationship between the ground part and the conductor part Condition C: The ground part and the conductor part do not overlap (Study item 3) Power supply mode from the power supply part to the conductor part Condition E: Direct power supply (electrical conduction)

[0124] In the case of study (5), when viewed in the normal direction (Z direction) of the front surface of the ground portion 103, the base portion does not overlap with the ground portion 103. In this case, the base portion functions as a radiating element of the film antenna together with the main body portion, as in the case of study (3). For this reason, the gradualness of the shape of the outline of the base portion is considered in the direction along the X direction.

[0125] FIG. 25 is a diagram showing an example of the VSWR frequency characteristics of the film antenna in the study case (5).

[0126] 25, the horizontal axis represents frequency and the vertical axis represents voltage standing wave ratio (VSWR). The results of VSWR when M is changed variously (M=0, 0.3, 0.5, 1, 2, 5) are shown for each line type.

[0127] As shown in Figure 25, the VSWR is improved when M>0 than when M=0. In other words, the VSWR is improved when the outline of the base of the film antenna is a shape that gradually changes. In the study example (5), the VSWR is generally good when M>0, but the VSWR is better when M<1 (e.g., film antenna 12I with M=0.5) than when M>1 (e.g., film antenna 12J with M=2). In other words, the VSWR is improved when the outline of the base of the film antenna is convex on the side away from axis A.

[0128] However, when M>2, if the value of M is set too large, the contour of the base of the film antenna will have a shape that does not change gradually, and the VSWR will deteriorate.

[0129] <<Modifications Related to the Shape of Film Antenna>> <Second Modification> Fig. 26 is a perspective view of an antenna device 10K of a second modification, as viewed from the +Z direction side. Fig. 27 is a perspective view of an antenna device 10K of the second modification, as viewed from the -Z direction side.

[0130] 26 and 27, in the antenna device 10K of the second modification, the power supply portion 11 and the root portion 122K of the conductor portion 126K are disposed on the −Z direction side of the ground portion 103, and are bent in the +Z direction at the boundary between the root portion 122K and the main body portion 121K. As a result, the main body portion 121K is disposed on the +Z direction side through the opening 104 of the ground portion 103. Furthermore, as shown in FIG. 27, the root portion 122K extends parallel to the XY plane, and the main body portion 121K extends parallel to the ZX plane.

[0131] In the film antenna 12K of the second modification, the outer shape of the base portion 122K of the conductor portion 126K from the end portion on the internal conductor side feed portion 111 side (feeder line side) of the feed portion 11 to the main body portion 121K is also shaped so as to gradually change, thereby improving the characteristics of the film antenna 12K over a wide band.

[0132] In the antenna device 10 of the present embodiment described above, the entire conductor portion 126 of the film antenna 12 extends parallel to the surface on the +Z direction side of the ground portion 103. However, in the antenna device 10K of the second modified example, the main body portion 121K of the conductor portion 126K can be disposed upright relative to the surface on the +Z direction side of the ground portion 103. In this way, the shape of the film antenna can be modified according to conditions such as the installation location and the desired frequency band.

[0133] Furthermore, in the antenna device 10 of the present embodiment described above, the coaxial cable 90 was arranged on the surface on the +Z direction side of the ground portion 103. However, in the antenna device 10K of the second modified example, the root portion 122K is arranged on the −Z direction side of the ground portion 103, and therefore the coaxial cable 90 connected to the root portion 122K via the power supply portion 11 can also be arranged on the −Z direction side of the ground portion 103. In this way, the arrangement location of the coaxial cable 90 can be flexibly changed, for example, the coaxial cable 90 can be arranged in a location that is not visible for the purpose of improving the appearance, etc.

[0134] <Third Modification> Fig. 28 is a perspective view of an antenna device 10L of a third modification, as viewed from the +Z direction side. Fig. 29 is a perspective view of an antenna device 10L of the third modification, as viewed from the -Z direction side.

[0135] In the antenna device 10L of the third modification, the feeder 11 is disposed on the −Z direction side of the ground portion 103, similarly to the antenna device 10K of the second modification. However, unlike the antenna device 10K of the second modification, the antenna device 10L of the third modification has the entire conductor 126L (main body 121L and root portion 122L) disposed on the +Z direction side of the ground portion 103, as shown in FIGS. 28 and 29 . The root portion 122L of the conductor 126L is connected to the internal conductor side feeder 111 at an end of the feeder 11 on the internal conductor side feeder 111 side (feed line side). Here, the internal conductor side feeder 111 is disposed on the −Z direction side of the ground portion 103, and the boundary between the internal conductor side feeder 111 and the root portion 122L is bent. As a result, the main body 121L and the root portion 122L are disposed on the +Z direction side through the opening 104 of the ground portion 103. Furthermore, as shown in FIG. 28 , the main body 121L and the root portion 122L both extend parallel to the ZX plane.

[0136] In the film antenna 12L of the third modification, the conductor 126L has a root 122L whose outline gradually changes from the end of the feeder 11 on the internal conductor feeder 111 side (feeder line side) to the main body 121L, thereby improving the characteristics of the film antenna 12L over a wide band.

[0137] In the antenna device 10 of the present embodiment described above, the entire conductor portion 126 of the film antenna 12 extends parallel to the surface on the +Z direction side of the ground portion 103. However, in the antenna device 10L of the third modified example, the entire conductor portion 126L can be disposed upright relative to the surface on the +Z direction side of the ground portion 103. In this way, the shape of the film antenna can be modified depending on conditions such as the installation location and the desired frequency band.

[0138] Furthermore, in the antenna device 10 of the present embodiment described above, the coaxial cable 90 was arranged on the surface on the +Z direction side of the ground portion 103. However, in the antenna device 10L of the third modified example, the internal conductor side feed portion 111 is arranged on the −Z direction side of the ground portion 103, and therefore the coaxial cable 90 connected to the internal conductor side feed portion 111 can also be arranged on the −Z direction side of the ground portion 103. In this way, the arrangement location of the coaxial cable 90 can be flexibly changed, for example, the coaxial cable 90 can be arranged in a location that is not visible for the purpose of improving the appearance, etc.

[0139] <Fourth Modification> Fig. 30 is a perspective view of an antenna device 10M according to a fourth modification. Fig. 31 is an enlarged view of the dashed line portion in Fig. 30. Fig. 32 is an explanatory diagram showing a cross section of the antenna device 10M according to the fourth modification.

[0140] The object 100M on which the antenna device 10M of the fourth modified example is disposed differs from the object 100 on which the antenna device 10 of the present embodiment described above is disposed. Specifically, a step is formed at the boundary between the transmissive portion 101M and the opaque portion 102M of the object 100M. As shown in FIG. 32 , the upper surface of the transmissive portion 101M is located on the −Z direction side of the upper surface of the opaque portion 102M. In the fourth modified example, for example, the transmissive portion 101M is a window glass portion of a building, and the opaque portion 102M is a window frame portion of the building. However, the transmissive portion 101M and the opaque portion 102M are not limited to the example of a building and can also be applied to the other objects described above. For example, the transmissive portion 101M may be, for example, a vehicle windshield or side window, and the opaque portion 102M may be a pillar adjacent to the windshield or side window. Furthermore, the transmissive portion 101M may be a roof formed of glass of the vehicle, and the opaque portion 102M may be a vehicle frame supporting the roof.

[0141] The antenna device 10M of the fourth modified example is disposed across the transmissive portion 101M and the opaque portion 102M, which have a step formed at the boundary portion as described above. The main body portion 121M of the film antenna 12M is in contact with the transmissive portion 101M and is supported by the transmissive portion 101M, as shown in Fig. 32 . Meanwhile, the base portion 122M of the film antenna 12M is bent and directly connected to the internal conductor side feeding portion 111 of the feeding portion 11. This allows the film antenna 12M to be disposed along the step that is the boundary portion between the transmissive portion 101M and the opaque portion 102M.

[0142] In the film antenna 12M in the fourth modification, the convexity of the outline of the main body 121M is different from the convexity of the outline of the root 122M. In other words, by aligning the portion of the film antenna 12M with the opposite convexity (i.e., the root 122M) along the step, the portion along the non-transparent portion 102M (ground portion 103M) (i.e., the root 122M) overlaps with the ground portion 103M. Therefore, in the film antenna 12M, even if there is a step at the boundary between the transparent portion 101M and the non-transparent portion 102M, deterioration of the antenna characteristics can be suppressed.

[0143] In addition, in the fourth modified example, a support member (not shown) may be disposed between the film antenna 12M and the object 100M (the transparent portion 101M and the non-transparent portion 102M). The support member is formed of, for example, resin. By disposing the support member between the film antenna 12M and the object 100M, the film antenna 12M can be stably held. Furthermore, in the fourth modified example, by disposing the support member between the film antenna 12M and the object 100M, the bent root portion 122M can be separated from the transparent portion 101M and the non-transparent portion 102M.

[0144] Furthermore, the support member disposed between the film antenna 12M and the transmission portion 101M is preferably formed of a transparent material. This makes it possible to suppress the influence of the support member on the transmission of visible light and infrared light through the transmission portion 101M. The support member disposed between the film antenna 12M and the object 100M may be composed of multiple members, or may be integrally formed. The support member may be applied not only to the antenna device 10M of the fourth modified example, but also to the antenna devices described in the other examples and embodiments.

[0145] The antenna device may also include a substrate (not shown). The substrate is a member on which electronic circuits configured with conductor patterns and electronic components are arranged, such as a printed circuit board (PCB) or a flexible printed circuit (FPC). The substrate is supported by a support member.

[0146] Furthermore, even in an installation location where there is no step at the boundary between the transparent and non-transparent portions and the base does not overlap with the ground portion, good antenna characteristics are achieved, as in the above-mentioned study example (5). As such, the antenna device 10 of this embodiment can be installed in a variety of installation locations, and by having good antenna characteristics in all cases, it is possible to realize an antenna device with fewer restrictions on installation location.

[0147] <<Fifth Modification>> FIG. 33 is an explanatory diagram showing a cross section of an antenna device 10N of a fifth modification.

[0148] As described above, in the antenna device 10 of this embodiment, when the antenna device 10 is installed on the opaque portion 102 of the object 100, which is the installation target side, the external conductor side feeding portion 112 of the feeding portion 11 is connected to the opaque portion 102 of the object 100 with adhesive or tape. At this time, depending on the thickness of the adhesive or tape used to connect the external conductor side feeding portion 112 and the opaque portion 102, the separation distance between the conductor portion 126 of the film antenna 12 and the opaque portion 102 may differ from the desired separation distance. As a result, when the antenna device 10 is installed on the object 100, which is the installation target side, additional adjustment may be required to ensure desired antenna characteristics.

[0149] Therefore, in the antenna device 10N of the fifth modified example, the power supply unit 11 has a conductive member 113 on the −Z direction side of the outer conductor side power supply unit 112 in the antenna device 10 of the present embodiment. Like the outer conductor side power supply unit 112, the conductive member 113 is a portion to which the outer conductor 92 of the coaxial cable 90 is electrically connected. In the antenna device 10N of the fifth modified example, the conductive member 113 is formed of a conductive material such as metal, and is electrically connected to the opaque portion 102 via capacitive coupling. In the antenna device 10N, the conductive member 113 is disposed so that the distance between the conductive member 113 and the conductor portion 126 of the film antenna 12 is constant. This makes it easy to ensure the desired antenna characteristics of the antenna device 10N when installing the antenna device 10N on the object 100 to which it is to be installed.

[0150] <<Other Modifications of the Antenna Device 10>> In the antenna devices of the present embodiment and the modifications described above, a film antenna has been used as an example to explain how the characteristics of the film antenna can be improved over a wide frequency band. However, the antenna of the antenna device is not limited to a film antenna, and may be an antenna formed from a metal plate. Alternatively, it may be an antenna formed from a conductor pattern on a substrate, or an antenna made of a molded integrated circuit device (MID) formed from a conductor pattern on a resin molded product. This also makes it possible to improve the characteristics of the metal plate antenna over a wide frequency band.

[0151] In the above-described embodiment, examples have been described in which the antenna device 10 is installed in a vehicle, a vending machine, or a building as examples of the object 100. However, the object 100 on which the antenna device 10 is installed is not limited to the above-described examples. The antenna device 10 may also be installed in, for example, a PC, a mobile terminal (such as a smartphone, tablet, or POS device), or a home appliance (such as a refrigerator, air conditioner, or rice cooker).

[0152] Summary According to the present specification, the following film antenna is provided.

[0153] (Aspect 1) Aspect 1 is a film antenna including a first conductor portion that receives power from a power feed line, the first conductor portion having a root portion located on the power feed line side and a main body portion adjacent to the root portion, and the outer shape of the root portion from the end on the power feed line side to the main body portion gradually changes.

[0154] According to the above-described aspect, the characteristics of the film antenna can be improved over a wide band.

[0155] (Aspect 2) In aspect 2, when a line passing through the end of the first conductor on the power supply line side and the geometric center of the first conductor is taken as an axis, the distance from the axis to the outline gradually increases or decreases.

[0156] According to the above-described aspect, the characteristics of the film antenna can be improved over a wide band.

[0157] (Aspect 3) In aspect 3, the outline of the base portion from the end on the power supply line side to the main body portion and the outline of the main body portion extending from the base portion each include a convex curve extending in a direction away from the axis.

[0158] According to the above-described aspect, the characteristics of the film antenna can be improved over a wide band.

[0159] (Aspect 4) In aspect 4, the outline of the base portion from the end on the power supply line side to the main body portion includes a convex curve toward the axis, and the outline of the main body portion extending from the base portion includes a convex curve away from the axis.

[0160] According to the above-described aspect, the characteristics of the film antenna can be improved over a wide band.

[0161] (Aspect 5) In aspect 5, a second conductor portion is provided that is connected to the power supply line and supplies power to the first conductor portion via capacitive coupling.

[0162] According to the above-described embodiment, the characteristics of the film antenna can be improved over a wide frequency range. Furthermore, since the film antenna is connected to the power supply part by capacitive coupling, deformation of the film antenna can be suppressed compared to when the film antenna is directly connected to the power supply part by soldering or the like.

[0163] According to the present specification, there is provided an antenna device having the following aspects.

[0164] (Aspect 6) Aspect 6 is an antenna device comprising a film antenna according to any one of the above aspects and a ground section, wherein when viewed in the normal direction of the front surface of the ground section, at least a portion of the base section has an overlapping section that overlaps with the ground section.

[0165] According to the above-described aspect, even when at least a portion of the base portion overlaps with the ground portion, deterioration of the characteristics of the film antenna can be suppressed and the characteristics of the film antenna can be improved over a wide band.

[0166] (Aspect 7) In aspect 7, the overlapping portion serves as a transmission line that feeds power to the first conductor portion.

[0167] According to the above-described aspect, the characteristics of the film antenna can be improved over a wide band.

[0168] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof.

[0169] 10, 10A to 10L Antenna device 12, 12A to 12L Film antenna 91 Inner conductor 103 Ground portion 111, 111A Inner conductor side power feeding portion (second conductor portion) 112 Outer conductor side power feeding portion 121, 121E to 121L Main body portion 122, 122E to 122L Base portion 126, 126B to 126L Conductor portion (first conductor portion)

Claims

1. A film antenna comprising a first conductor portion fed from a feeder line, the first conductor portion having a base portion located on the feeder line side and a main body portion adjacent to the base portion, and the outline of the base portion from the end on the feeder line side to the main body portion having a shape that gradually changes.

2. A film antenna as described in claim 1, wherein, when a line passing through the end of the first conductor portion on the feeder line side and the geometric center of the first conductor portion is taken as an axis, the distance from the axis to the outline gradually increases or decreases.

3. A film antenna as described in claim 2, wherein the outline of the base portion from the end on the feeder line side to the main body portion and the outline of the main body portion extending from the base portion each include a convex curve extending in a direction away from the axis.

4. A film antenna as described in claim 2, wherein the outline of the base portion from the end on the feeder line side to the main body portion includes a convex curve in a direction approaching the axis, and the outline of the main body portion extending from the base portion includes a convex curve in a direction away from the axis.

5. The film antenna according to claim 1, further comprising a second conductor portion connected to the power feed line and supplying power to the first conductor portion via capacitive coupling.

6. An antenna device comprising: the film antenna according to any one of claims 1 to 5; and a ground section, wherein when viewed in the normal direction to the front surface of the ground section, at least a part of the base section has an overlapping section that overlaps with the ground section.

7. The antenna device according to claim 6, wherein the overlapping portion serves as a transmission line that feeds power to the first conductor portion.

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