broadband antenna

Abstract

To simplify the configuration of antenna elements constituting a broadband antenna while using the back face of a substrate as a mounting surface.SOLUTION: A broadband antenna 2 includes a first antenna element 21 and a second antenna element 22 which are arranged on one side of a substrate 20 and formed of a conductor in a planar shape. Feeding points 21a, 22a each are formed approximately at the center of an edge where the first antenna element 21 and the second antenna element 22 face each other. In the first antenna element 21 and the second antenna element 22, there are formed protrusions 21b, 22b which are formed in a plane expanding in a tapered shape from the feeding points 21a, 22a, respectively, and extend from a portion of the tapered shape. The first antenna element 21 and the second antenna element 22 are formed in an almost line-symmetrical shape.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a broadband antenna that can be attached in a limited space.

Background Art

[0002] With the expansion of the IoT (Internet of Things) market, the frequencies used are expanding, and the demand for antennas with broadband characteristics is increasing. In recent years, terminal devices such as communication modules support global frequencies, and it is necessary to follow the electrical performance of the antenna. In addition, the space for attaching the antenna is limited, and it is required to maintain the appearance even when the antenna is installed. Also, it is required that the antenna has flexibility and can be installed on a curved surface, or that the antenna can be made broadband.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 discloses a conventional small planar antenna capable of covering the 800 MHz to 2000 MHz band. A front view of this conventional planar antenna 100 is shown in Figure 19, and a rear view is shown in Figure 20. As shown in these figures, the conventional planar antenna 100 has an insulating substrate 110 which is a flat rectangular plate, and an element section consisting of a first element 111 and a second element 112 formed on one surface of the insulating substrate 110. The first element 111 consists of a first loop element 111a which is formed in a loop shape that tapers out from the feed point, and a first T-shaped element 111b which is formed inside the first loop element 111a. The second element 112 consists of a second loop element 112a which is formed in a loop shape that tapers out from the feed point, and a second T-shaped element 112b which is formed inside the second loop element 112a. The first element 111 and the second element 112 are approximately symmetrical in shape. Furthermore, power supply sections 114a and 114b are formed on the other side of the insulating substrate 110, and a powerless element 113 of a predetermined length is also formed thereon.

[0005] Conventional planar antennas 100 have a complex configuration of first element 111 and second element 112 formed on the front surface, one side of the insulating substrate 110. Furthermore, the feeding sections 114a, 114b and the passive element 113 are formed on the back surface, the other side of the insulating substrate 110, making it difficult to use the back surface as a mounting surface for conventional planar antennas 100. Therefore, the present invention aims to provide a broadband antenna with a simple antenna element configuration, the ability to use one side of the substrate as a mounting surface, and a wide bandwidth. It also aims to provide a broadband antenna that can be made transparent. [Means for solving the problem]

[0006] The broadband antenna of the present invention comprises an insulating film substrate made of a rectangular transparent resin, and a first antenna element and a second antenna element formed of a conductive material in a planar shape adjacent to one side of the film substrate, wherein the first antenna element and the second antenna element are substantially symmetrical in shape, and a feed point is formed approximately in the center of the ends of the first antenna element and the second antenna element facing each other, and the first antenna element and the second antenna element are formed in a planar shape that tapers outwards from each of the feed points, which is a key feature of the present invention. Furthermore, in the broadband antenna of the present invention, the first antenna element and the second antenna element are formed of a mesh-like conductor that is visually transparent and transmits visible light.

[0007] Another broadband antenna of the present invention is characterized by comprising an insulating substrate which is a flat rectangular plate, and a first antenna element and a second antenna element which are formed of a conductive material in a planar shape arranged side by side on one surface of the substrate, wherein a feed point is formed approximately in the center of the ends of the first antenna element and the second antenna element which face each other, and the first antenna element and the second antenna element are formed in a planar shape which tapers outwards from each of the feed points, and a projection is formed which extends from the tapered portion, and the first antenna element and the second antenna element are substantially symmetrical in shape to each other. Furthermore, in another broadband antenna of the present invention, the insulating substrate is a film substrate made of transparent resin, and the first antenna element and the second antenna element on which the protrusions are formed are made of a mesh-like conductor that is visually transparent and transmits visible light, and the feed points of the first antenna element and the second antenna element are formed in a solid shape. Furthermore, in other broadband antennas of the present invention, the insulating substrate is a film substrate made of transparent resin, and the first antenna element and the second antenna element on which the protrusions are formed are formed of a mesh-like conductor consisting of triangular, square or polygonal, circular or elliptical meshes that are visually transparent and transmit visible light, and the feed points of the first antenna element and the second antenna element are formed in a solid form. Furthermore, in another broadband antenna of the present invention, the length of the protrusions formed on the first antenna element and the second antenna element is set to be approximately 0.036λa to approximately 0.059λa with respect to the wavelength λa at a frequency of 0.9 GHz in the design frequency band, and approximately 0.080λb to approximately 0.130λb with respect to the wavelength λb at a frequency of 2.0 GHz. [Effects of the Invention]

[0008] The broadband antenna of the present invention comprises a first antenna element and a second antenna element formed in a planar shape on one side of a transparent resin film substrate, thereby providing flexibility and enabling installation on curved surfaces. In this case, since the antenna elements constituting the broadband antenna are formed only on one side of the film substrate, the other side of the film substrate can be used as a mounting surface. Furthermore, by forming the first and second antenna elements from a mesh-like conductive material that is visually transparent and transmits visible light, the broadband antenna can be made transparent. This allows the broadband antenna to be installed on the surface of a device that utilizes visible light without compromising the device's appearance while maintaining the device's performance. Furthermore, other broadband antennas of the present invention have protrusions extending from the tapered portion between the first and second antenna elements, thereby achieving an even wider bandwidth. Moreover, by using a substrate made of transparent resin and forming the first and second antenna elements from a mesh-like conductor that is visually transparent and transmits visible light, the broadband antenna can be made transparent. This allows a broadband antenna to be installed on the surface of a device that utilizes visible light without compromising the device's appearance while maintaining the device's performance. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view showing the configuration of a planar antenna according to the first embodiment of the present invention. [Figure 2] This is a rear view showing the configuration of a planar antenna according to the first embodiment of the present invention. [Figure 3] This is a top view showing the configuration of a planar antenna according to the first embodiment of the present invention. [Figure 4] These are a left side view and a right side view showing the configuration of a planar antenna according to the first embodiment of the present invention. [Figure 5] This is a front view showing the configuration of a planar antenna according to a second embodiment of the present invention. [Figure 6] This is a rear view showing the configuration of a planar antenna according to a second embodiment of the present invention. [Figure 7] This is a top view showing the configuration of a planar antenna according to a second embodiment of the present invention. [Figure 8] These are left and right side views showing the configuration of a planar antenna according to a second embodiment of the present invention. [Figure 9] This is a front view showing the configuration of a planar antenna according to a third embodiment of the present invention. [Figure 10] This is a rear view showing the configuration of a planar antenna according to a third embodiment of the present invention. [Figure 11] This is a top view showing the configuration of a planar antenna according to a third embodiment of the present invention. [Figure 12]It is a left side view and a right side view showing the configuration of the planar antenna of the third embodiment according to the present invention. [Figure 13] It is a front view showing the configuration of the planar antenna of the fourth embodiment according to the present invention. [Figure 14] It is a rear view showing the configuration of the planar antenna of the fourth embodiment according to the present invention. [Figure 15] It is a top view showing the configuration of the planar antenna of the fourth embodiment according to the present invention. [Figure 16] It is a left side view and a right side view showing the configuration of the planar antenna of the fourth embodiment according to the present invention. [Figure 17] In the planar antenna of the second embodiment according to the present invention, it is a graph showing the VSWR 2.0 or less band with respect to the length of the protrusion of the antenna element. [Figure 18] In the planar antenna of the second embodiment according to the present invention, it is a table showing the wavelength ratio of the length of the protrusion of the antenna element with respect to the wavelength of the frequency in the designed frequency band. [Figure 19] It is a front view showing the configuration of a conventional planar antenna. [Figure 20] It is a rear view showing the configuration of a conventional planar antenna.

Embodiments for Carrying Out the Invention

[0010] <The Wideband Antenna of the First Embodiment of the Present Invention> The configuration of the wideband antenna 1 according to the first embodiment of the present invention is shown in FIGS. 1 to 4. FIG. 1 is a front view showing the configuration of the wideband antenna 1 of the first embodiment, FIG. 2 is a rear view showing the configuration of the wideband antenna 1 of the first embodiment, FIG. 3 is a top view showing the configuration of the wideband antenna 1 of the first embodiment, and FIG. 4 is a left side view and a right side view showing the configuration of the wideband antenna 1 of the first embodiment. As shown in these figures, the broadband antenna 1 of the first embodiment of the present invention comprises a rectangular flat film substrate 10, which is made of a flexible, insulating transparent resin with good high-frequency characteristics, such as polyethylene terephthalate (PET) film or Teflon® film. Two patterns, a first antenna element 11 and a second antenna element 12, are formed side by side on one surface of the film substrate 10. The patterns of the first antenna element 11 and the second antenna element 12 are planar in shape and are formed on one surface of the film substrate 10 by vapor deposition, printing, bonding, etching, or the like. The materials for the first antenna element 11 and the second antenna element 12 are preferably conductive materials with low electrical resistance, such as copper or silver paste. The illustrated film substrate 10 is a vertically elongated rectangle, with the first antenna element 11 formed on the upper half and the second antenna element 12 formed on the lower half. The first antenna element 11 and the second antenna element 12 are formed in a shape that is almost symmetrical to the first antenna element 11 and the second antenna element 12, with feed points 11a and 12a formed approximately in the center of the ends of the first antenna element 11 and the second antenna element 12 facing each other. The first antenna element 11 consists of a tapered portion that widens from the feed point 11a to the periphery of the film substrate 10, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the film substrate 10. The second antenna element 12 is formed in a shape that is almost symmetrical to the first antenna element 11, and consists of a tapered portion that widens from the feed point 12a to the periphery of the film substrate 10, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the film substrate 10.

[0011] In the broadband antenna 1 of the first embodiment, the feed point 11a of the first antenna element 11 and the feed point 12a of the second antenna element 12 are formed in a thick rectangular pattern. The tip of the central conductor 13a of the coaxial feed cable 13 is soldered to the feed point 11a, and the outer conductor 13b of the feed cable 13 is soldered to the feed point 12a. The design frequency band of the broadband antenna 1 is, for example, 650MHz to 2750MHz. The vertical dimension L1 of the broadband antenna 1 is approximately 1 / 2λ, where λ is the wavelength of the center frequency of the design frequency band. The horizontal dimension W1 of the broadband antenna 1 is approximately 1 / 4λ. The broadband antenna 1 functions as a dipole antenna that is centrally fed from the feed cable 13. In this case, the first antenna element 11 is the hot element, and the second antenna element 12 is the cold element. The broadband antenna 1 of the first embodiment has a design frequency band of 650 MHz to 2750 MHz. In the broadband antenna 1 of the first embodiment, the resonant frequency of the broadband antenna 1 is set to approximately 650 MHz to cover the lower end of the design frequency band. Here, the wavelength is shortened due to the influence of the relative permittivity εr of the film substrate 10. For example, if the film substrate 10 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the film substrate 10 is approximately 57.8%. Then, 1 / 2λ of 650 MHz is approximately 231 mm in free space, but on the film substrate 10 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L1 of the broadband antenna 1 formed on the film substrate 10 is approximately 135 mm, the resonant frequency of the broadband antenna 1 will be approximately 650 MHz. Here, as an example of approximate dimensions when the relative permittivity εr of the film substrate 10 of the broadband antenna 1 is approximately 3 and the design frequency band is 650MHz to 2750MHz, the dimension L1 is approximately 135mm, the width W1 is approximately 50mm, and the thickness of the film substrate 10 can be approximately 100μm. In this way, the broadband antenna 1 of the first embodiment is compact. The dimension of the long side of the film substrate 10 is approximately the same as L1, and the dimension of the short side of the film substrate 10 is approximately the same as W1.

[0012] As described above, the broadband antenna 1 of the first embodiment of the present invention functions as a broadband antenna because the first antenna element 11 and the second antenna element 12 are formed in a planar shape from a conductor. Furthermore, since the broadband antenna 1 of the first embodiment comprises the first antenna element 11 and the second antenna element 12 formed on one surface of a flexible transparent resin film substrate 10, it is flexible and can be installed on a curved surface using the other surface of the film substrate 10. In addition, the first antenna element 11 and the second antenna element 12 can be formed from a mesh-like conductor that is visually transparent and transmits visible light (not shown). That is, by making the first antenna element 11 and the second antenna element 12 a mesh that is visually transparent and transmits visible light, the broadband antenna 1 of the first embodiment can be made transparent. This makes it possible to install the broadband antenna 1 of the first embodiment on the surface of a device that utilizes visible light, such as a solar panel, without compromising its appearance while maintaining the performance of its power generation function.

[0013] <Broadband antenna according to a second embodiment of the present invention> Next, a broadband antenna 2 according to a second embodiment of the present invention will be described. The broadband antenna 2 of the second embodiment is provided with protrusions 21b and 22b on the first antenna element 21 and the second antenna element 22, thereby improving the broadband performance of the broadband antenna 1 of the first embodiment. The configuration of the broadband antenna 2 of the second embodiment of the present invention is shown in Figures 5 to 8. Figure 5 is a front view showing the configuration of the broadband antenna 2 of the second embodiment, Figure 6 is a rear view showing the configuration of the broadband antenna 2 of the second embodiment, Figure 7 is a top view showing the configuration of the broadband antenna 2 of the second embodiment, and Figure 8 is a left side view and a right side view showing the configuration of the broadband antenna 2 of the second embodiment. As shown in these figures, the broadband antenna 2 of the second embodiment of the present invention comprises a rectangular flat substrate 20, which is made of an insulating material with good high-frequency characteristics such as polyethylene terephthalate (PET), Teflon®, or glass epoxy. Two patterns, a first antenna element 21 and a second antenna element 22, are formed side by side on one surface of the substrate 20. The patterns of the first antenna element 21 and the second antenna element 22 are in a planar shape and are formed on one surface of the substrate 20 by vapor deposition, printing, bonding, etching, or the like. In this case, the substrate 20 may be made of a flat plate or film made of a flexible transparent resin with good high-frequency characteristics such as PET or Teflon®. Furthermore, the materials for the first antenna element 21 and the second antenna element 22 are preferably conductive materials with low electrical resistance such as copper or silver paste. The illustrated substrate 20 is a vertically elongated rectangle, with the first antenna element 21 formed on the upper half and the second antenna element 22 formed on the lower half. The first antenna element 21 and the second antenna element 22 are formed in a shape that is almost symmetrical to the first antenna element 21 and the second antenna element 22, with feed points 21a and 22a formed approximately in the center of the ends of the first antenna element 21 and the second antenna element 22 facing each other. The first antenna element 21 is composed of a tapered portion that widens from the feed point 21a to the periphery of the substrate 20 and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 20. The second antenna element 22 is formed in a shape that is almost symmetrical to the first antenna element 21 and is composed of a tapered portion that widens from the feed point 22a to the periphery of the substrate 20 and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 20.

[0014] In the broadband antenna 2 of the second embodiment, the feed point 21a of the second antenna element 21 and the feed point 22a of the second antenna element 22 are formed with a thick rectangular solid pattern and are solderable. The tip of the central conductor 23a of the feed cable 23, which is a coaxial cable, is soldered to the feed point 21a, and the outer conductor 23b of the feed cable 23 is soldered to the feed point 22a. The design frequency band of the broadband antenna 2 is, for example, 650MHz to 2750MHz, the vertical dimension L1 of the broadband antenna 2 is approximately 1 / 2λ, where λ is the wavelength of the center frequency of the design frequency band, and the horizontal dimension W1 of the broadband antenna 2 is approximately 1 / 4λ, so that the broadband antenna 2 functions as a dipole antenna that is centrally fed from the feed cable 23. In this case, the first antenna element 21 is the hot element, and the second antenna element 22 is the cold element.

[0015] A characteristic feature of the broadband antenna 2 of the second embodiment is that two elongated protrusions 21b are formed on one tapered portion of the first antenna element 21, extending from the starting end near the feed point 21a and from the end reaching the periphery of the substrate 20. Similarly, in the second antenna element 22, two elongated protrusions 22b are formed on one tapered portion of the second antenna element 22, extending from the starting end near the feed point 22a and from the end reaching the periphery of the substrate 20. The lengths L2 of each of the two protrusions 21b and the two protrusions 22b may be the same or different. The two protrusions 21b formed on the first antenna element 21 and the two protrusions 22b formed on the second antenna element 22 allow for adjustment of the inductive (L) component and capacitive (C) component in the first antenna element 21 and the second antenna element 22. By making this adjustment, the broadband performance of the broadband antenna 2 of the second embodiment can be improved, resulting in a broader bandwidth. The adjustment of the L and C components can be done by changing the length L2 and width of the two protrusions 21b and 22b. The number of protrusions 21b and 22b is not limited to two; there may be one or three or more. The protrusions 21b and 22b may be provided symmetrically or asymmetrically. In other words, the protruding positions of the protrusions 21b and 22b are not limited to those shown in the figure. The protruding positions of the protrusions 21b and 22b can be set to any position, as long as they can be positioned in the space formed between the tapered portion between the first antenna element 21 and the second antenna element 22, which are arranged facing each other.

[0016] The broadband antenna 2 of the second embodiment has a design frequency band of 650 MHz to 2750 MHz. In the broadband antenna 2 of the second embodiment, the resonant frequency of the broadband antenna 2 is set to approximately 650 MHz to cover the lower end of the design frequency band. Here, the wavelength is shortened due to the influence of the relative permittivity εr of the substrate 20. For example, if the substrate 20 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the substrate 20 is approximately 57.8%. Then, 1 / 2λ of 650 MHz is approximately 231 mm in free space, but on the substrate 20 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L1 of the broadband antenna 2 formed on the substrate 20 is approximately 135 mm, the resonant frequency of the broadband antenna 2 will be approximately 650 MHz. Here, as an example of approximate dimensions when the relative permittivity εr of the substrate 20 of the broadband antenna 2 is approximately 3 and the design frequency band is 650MHz to 2750MHz, the dimension L1 is approximately 135mm, the width W1 is approximately 50mm, and the thickness of the substrate 20 can be approximately 100μm. In this way, the broadband antenna 2 of the second embodiment is compact. The dimension of the long side of the substrate 20 is approximately the same as L1, and the dimension of the short side of the substrate 20 is approximately the same as W1. Furthermore, the length L2 of the protrusions 21b and 22b is preferably approximately 12mm to approximately 19.5mm, and the width of the protrusions 21b and 22b is, for example, approximately 2mm.

[0017] As described above, the broadband antenna 2 of the second embodiment of the present invention functions as a broadband antenna 2 with improved broadband performance because the first antenna element 21 and the second antenna element 22 are formed of a conductive material in a planar shape, and two protrusions 21b are formed on the first antenna element 21 and two protrusions 22b are formed on the second antenna element 22. Furthermore, in the broadband antenna 2 of the second embodiment, by using a substrate 20 made of a flexible resin and forming the first antenna element 21 and the second antenna element 22 on one surface of the substrate 20, the substrate becomes flexible and can be installed on a curved surface using the other surface of the substrate 20.

[0018] <Broadband antenna according to the third embodiment of the present invention> Next, a broadband antenna 3 according to a third embodiment of the present invention will be described. In the broadband antenna 3 of the third embodiment, the first antenna element 31 and the second antenna element 32 are formed from a mesh-like conductive material, thereby making the broadband antenna 3 transparent. Next, the configuration of the broadband antenna 3 of the third embodiment of the present invention is shown in Figures 9 to 12. Figure 9 is a front view showing the configuration of the broadband antenna 3 of the third embodiment, Figure 10 is a rear view showing the configuration of the broadband antenna 3 of the third embodiment, Figure 11 is a top view showing the configuration of the broadband antenna 3 of the third embodiment, and Figure 12 is a left side view and a right side view showing the configuration of the broadband antenna 3 of the third embodiment. As shown in these figures, the broadband antenna 3 of the third embodiment of the present invention comprises a rectangular flat substrate 30, which is made of an insulating material with good high-frequency characteristics such as polyethylene terephthalate (PET), Teflon®, or glass epoxy. Two patterns, a first antenna element 31 and a second antenna element 32, are formed side by side on one surface of the substrate 30. The patterns of the first antenna element 31 and the second antenna element 32 are in a planar shape and are formed on one surface of the substrate 30 by vapor deposition, printing, bonding, etching, or the like. In this case, the substrate 30 may be made of a flat plate or film made of a flexible transparent resin with good high-frequency characteristics such as PET or Teflon®. Furthermore, the first antenna element 31 and the second antenna element 32 are formed from a mesh-like conductor, and the material of the conductor is preferably a conductor with low electrical resistance such as copper or silver paste. The illustrated substrate 30 is a vertically elongated rectangle, with a mesh-like first antenna element 31 formed on the upper half and a mesh-like second antenna element 32 formed on the lower half. The first antenna element 31 and the second antenna element 32 are approximately symmetrical in shape, and feed points 31a and 32a are formed approximately in the center of the ends of the first antenna element 31 and the second antenna element 32 facing each other. The first antenna element 31 consists of a tapered portion that widens from the feed point 31a to the periphery of the substrate 30, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 30. The second antenna element 32 is formed in a shape that is approximately symmetrical to the first antenna element 31, and consists of a tapered portion that widens from the feed point 32a to the periphery of the substrate 30, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 30.

[0019] In the broadband antenna 3 of the third embodiment, the mesh of the mesh-like conductor, which is the first antenna element 31 and the second antenna element 32, is square, and the mesh spacing is S. For example, the mesh spacing S is approximately 400 μm, and the width of the lines forming the mesh is approximately 8 μm, resulting in a mesh-like conductor that is visually transparent and transmits visible light. In other words, the first antenna element 31 and the second antenna element 32 become transparent. Note that the dimensions of the mesh spacing S and the width of the lines forming the mesh are not limited to the above values, but are acceptable as long as they result in a mesh that is visually transparent and transmits visible light.

[0020] Furthermore, in the broadband antenna 3 of the third embodiment, the feed point 31a of the first antenna element 31 and the feed point 32a of the second antenna element 32 are formed with a thick rectangular solid pattern and are solderable. The tip of the central conductor 33a of the feed cable 33, which is a coaxial cable, is soldered to the feed point 31a, and the outer conductor 33b of the feed cable 33 is soldered to the feed point 32a. The design frequency band of the broadband antenna 3 is, for example, 650MHz to 2750MHz, the vertical dimension L1 of the broadband antenna 3 is approximately 1 / 2λ, where λ is the wavelength of the center frequency of the design frequency band, and the horizontal dimension W1 of the broadband antenna 3 is approximately 1 / 4λ, so that the broadband antenna 3 functions as a dipole antenna that is centrally fed from the feed cable 33. In this case, the first antenna element 31 is the hot element, and the second antenna element 32 is the cold element.

[0021] Furthermore, two elongated mesh-like protrusions 31b are formed on the first antenna element 31, extending from the starting end near the feed point 31a on one tapered portion and from the end reaching the periphery of the substrate 30. Similarly, on the second antenna element 32, two elongated mesh-like protrusions 32b are formed, extending from the starting end near the feed point 32a on one tapered portion and from the end reaching the periphery of the substrate 30. The lengths L2 of each of the two protrusions 31b and 32b may be the same or different. The two protrusions 31b formed on the first antenna element 31 and the two protrusions 32b formed on the second antenna element 32 allow for adjustment of the L component and C component in the first antenna element 31 and the second antenna element 32, and by making this adjustment, the broadband performance of the broadband antenna 3 of the third embodiment is improved and the bandwidth is increased. The L and C components described above can be adjusted by changing the length L2 and width of the two protrusions 31b and 32b. The number of protrusions 31b and 32b is not limited to two; there may be one or three or more. The protrusions 31b and 32b may be arranged symmetrically or asymmetrically. In other words, the protruding positions of the protrusions 31b and 32b are not limited to the positions shown in the figure. As long as they can be positioned in the space formed between the tapered portion between the first antenna element 31 and the second antenna element 32 which are arranged facing each other, the protruding positions of the protrusions 31b and 32b can be any position.

[0022] In the broadband antenna 3 of the third embodiment of the present invention, the VSWR characteristics of the broadband antenna 3 of the third embodiment are shown in the graph in Figure 17 when the lengths L2 of the four protrusions, two protrusions 31b on the first antenna element 31 and two protrusions 32b on the second antenna element 32, are simultaneously changed by the same dimension. In this case, the horizontal axis represents the length L2 of the protrusions 31b and 32b from 0 [mm] to 20 [mm], and the vertical axis represents the VSWR 2.0 or less bandwidth. In this case, the width of the protrusions 31b and 32b is approximately 2 mm. In the VSWR characteristics of the broadband antenna 3 shown in Figure 17, the design frequency is set to 650MHz to 2750MHz. Referring to the VSWR characteristics shown in Figure 17, when the length L2 of the protrusions 31b and 32b of the first antenna element 31 and the second antenna element 32 is 0mm, the protrusions 31b and 32b are not formed, which corresponds to the case in the broadband antenna 1 of the first embodiment where the first antenna element 11 and the second antenna element 12 are in a mesh shape. When the length L2 of these protrusions 31b and 32b is 0mm, a broadband relative bandwidth of approximately 39% is obtained, which is the bandwidth in which the VSWR is 2.0 or less. When the length L2 of the protrusions 31b and 32b of the first antenna element 31 and the second antenna element 32 is 20 mm, a wider relative bandwidth of approximately 66% is obtained as the bandwidth for which the VSWR is 2.0 or less, demonstrating the effect of providing the protrusions 31b and 32b. Furthermore, referring to the VSWR characteristics shown in Figure 17, the length L2 of the protrusions 31b and 32b that result in a relative bandwidth of 70% or more with a VSWR of 2.0 or less is approximately 12 mm to 19.5 mm. Thus, the achievement of a relative bandwidth BW of 70% or more with a VSWR of 2.0 or less is due to the effect of providing the protrusions 31b and 32b. As shown in the table in Figure 18, 12 mm corresponds to 0.036 λa if the wavelength at 900 MHz is λa, and to 0.08 λb if the wavelength at 2 GHz is λb. Similarly, 19.5 mm corresponds to 0.059 λa for the wavelength at 900 MHz and to 0.130 λb for the wavelength at 2 GHz. Note that the VSWR characteristics shown in the graph in Figure 17 are those of the broadband antenna 3 of the third embodiment, but the VSWR characteristics of the broadband antenna 2 of the second embodiment are the same as those shown in the graph in Figure 17.

[0023] The broadband antenna 3 of the third embodiment has a design frequency band of 650 MHz to 2750 MHz. In the broadband antenna 3 of the third embodiment, the resonant frequency of the broadband antenna 3 is set to approximately 650 MHz to cover the lower end of the design frequency band. Here, the wavelength is shortened due to the influence of the relative permittivity εr of the substrate 30. For example, if the substrate 30 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the substrate 30 is approximately 57.8%. Then, 1 / 2λ of 650 MHz is approximately 231 mm in free space, but on the substrate 30 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L1 of the broadband antenna 3 formed on the substrate 30 is approximately 135 mm, the resonant frequency of the broadband antenna 3 will be approximately 650 MHz. Here, as an example of approximate dimensions when the relative permittivity εr of the substrate 30 of the broadband antenna 3 is approximately 3 and the design frequency band is 650MHz to 2750MHz, the dimension L1 is approximately 135mm, the width W1 is approximately 50mm, and the thickness of the substrate 30 can be approximately 100μm. In this way, the broadband antenna 3 of the third embodiment is compact. The dimension of the long side of the substrate 30 is approximately the same as L1, and the dimension of the short side of the substrate 30 is approximately the same as W1. The length L2 of the protrusions 31b and 32b is preferably approximately 12mm to approximately 19.5mm, and the width of the protrusions 31b and 32b is, for example, approximately 2mm.

[0024] As described above, the broadband antenna 3 of the third embodiment of the present invention functions as a broadband antenna 3 with improved broadband performance because the first antenna element 31 and the second antenna element 32 are formed of a mesh-like conductive material in a planar shape, and two protrusions 31b are formed on the first antenna element 31 and two protrusions 32b are formed on the second antenna element 32. Furthermore, in the broadband antenna 3 of the third embodiment, the substrate 30 is a transparent substrate, and the first antenna element 31 and the second antenna element 32 are made of a mesh-like material that is visually transparent and transmits visible light, so the broadband antenna 3 of the third embodiment is transparent. As a result, the broadband antenna 3 of the third embodiment can be installed on the surface of a solar panel, for example, on a device that uses visible light, without compromising the appearance while maintaining the performance of the power generation function. Furthermore, by using a substrate such as a film made of a flexible resin as the substrate 30, and forming the first antenna element 31 and the second antenna element 32 on one surface of the substrate 30, it becomes flexible, allowing it to be installed on a curved surface of the mounting surface using the other surface of the substrate 30.

[0025] Next, a broadband antenna 4 according to the fourth embodiment of the present invention will be described. The broadband antenna 4 according to the fourth embodiment is a modified version of the broadband antenna 3 according to the third embodiment of the present invention. Specifically, the shape of the conductive mesh forming the first antenna element 41 and the second antenna element 42 has been changed. Next, the configuration of the broadband antenna 4 of the fourth embodiment of the present invention is shown in Figures 13 to 16. Figure 13 is a front view showing the configuration of the broadband antenna 4 of the fourth embodiment, Figure 14 is a rear view showing the configuration of the broadband antenna 4 of the fourth embodiment, Figure 15 is a top view showing the configuration of the broadband antenna 4 of the fourth embodiment, and Figure 16 is a left side view and a right side view showing the configuration of the broadband antenna 4 of the fourth embodiment. As shown in these figures, the broadband antenna 4 of the fourth embodiment of the present invention comprises a rectangular flat substrate 40, which is made of an insulating material with good high-frequency characteristics such as polyethylene terephthalate (PET), Teflon®, or glass epoxy. Two patterns, a first antenna element 41 and a second antenna element 42, are formed side by side on one surface of the substrate 40. The patterns of the first antenna element 41 and the second antenna element 42 are in a planar shape and are formed on one surface of the substrate 40 by vapor deposition, printing, bonding, etching, or the like. In this case, the substrate 40 may be made of a flat plate or film made of a flexible transparent resin with good high-frequency characteristics such as PET or Teflon®. Furthermore, the first antenna element 41 and the second antenna element 42 are formed from a mesh-like conductor, and the material of the conductor is preferably a conductor with low electrical resistance such as copper or silver paste. The illustrated substrate 40 is a vertically elongated rectangle, with a mesh-like first antenna element 41 formed on the upper half and a mesh-like second antenna element 42 formed on the lower half. The first antenna element 41 and the second antenna element 42 are approximately symmetrical in shape, and feed points 41a and 42a are formed approximately in the center of the ends of the first antenna element 41 and the second antenna element 42 facing each other. The first antenna element 41 consists of a tapered portion that widens from the feed point 41a to the periphery of the substrate 40, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 40. The second antenna element 42 is formed in a shape that is approximately symmetrical to the first antenna element 41, and consists of a tapered portion that widens from the feed point 42a to the periphery of the substrate 40, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 30.

[0026] In the broadband antenna 4 of the fourth embodiment, the mesh in the mesh-like conductor that forms the first antenna element 41 and the second antenna element 42 is triangular. The spacing of the mesh and the width of the lines forming the mesh are set to dimensions that result in a mesh that is visually transparent and transmits visible light. Furthermore, the shape of the mesh is not limited to a triangle, but can be a polygon, a combination of polygons, a circle, an ellipse, or any other shape that results in a mesh that is visually transparent and transmits visible light. As a result, the first antenna element 41 and the second antenna element 42 become transparent.

[0027] Furthermore, in the broadband antenna 4 of the fourth embodiment, the feed point 41a of the first antenna element 41 and the feed point 42a of the second antenna element 42 are formed with a thick rectangular solid pattern and are solderable. The tip of the central conductor 43a of the feed cable 43, which is a coaxial cable, is soldered to the feed point 41a, and the outer conductor 43b of the feed cable 43 is soldered to the feed point 42a. The design frequency band of the broadband antenna 4 is, for example, 650MHz to 2750MHz, the vertical dimension L1 of the broadband antenna 4 is approximately 1 / 2λ, where λ is the wavelength of the center frequency of the design frequency band, and the horizontal dimension W1 of the broadband antenna 4 is approximately 1 / 4λ, so that the broadband antenna 4 functions as a dipole antenna that is centrally fed from the feed cable 43. In this case, the first antenna element 41 is the hot element, and the second antenna element 42 is the cold element.

[0028] Furthermore, two elongated mesh-like protrusions 41b are formed on the first antenna element 41, extending from the starting end near the feed point 41a on one tapered portion and from the end reaching the periphery of the substrate 40. Similarly, on the second antenna element 42, two elongated mesh-like protrusions 42b are formed, extending from the starting end near the feed point 42a on one tapered portion and from the end reaching the periphery of the substrate 40. The lengths L2 of each of the two protrusions 41b and 42b may be the same or different. The two protrusions 41b formed on the first antenna element 41 and the two protrusions 42b formed on the second antenna element 42 allow for adjustment of the L component and C component in the first antenna element 41 and the second antenna element 42, and by making this adjustment, the broadband performance of the broadband antenna 4 of the fourth embodiment is improved and the bandwidth is increased. The L and C components described above can be adjusted by changing the length L2 and width of the two protrusions 41b and 42b. The number of protrusions 41b and 42b is not limited to two; there may be one or three or more. The protrusions 41b and 42b may be arranged symmetrically or asymmetrically. In other words, the protruding positions of the protrusions 41b and 42b are not limited to the positions shown in the figure. The protruding positions of the protrusions 41b and 42b can be any position as long as they can be positioned in the space formed between the tapered portion between the first antenna element 41 and the second antenna element 42, which are arranged facing each other.

[0029] In the broadband antenna 4 of the fourth embodiment of the present invention, when the lengths L2 of the four protrusions L2 of the two protrusions 41b of the first antenna element 41 and the two protrusions 42b of the second antenna element 42 are simultaneously changed by the same dimension, the VSWR characteristics of the broadband antenna 4 of the fourth embodiment are the same as the VSWR characteristics shown in the graph of Figure 17 described above. The explanation is omitted.

[0030] The broadband antenna 4 of the fourth embodiment has a design frequency band of 650 MHz to 2750 MHz. In the broadband antenna 4 of the fourth embodiment, the resonant frequency of the broadband antenna 4 is set to approximately 650 MHz to cover the lower end of the design frequency band. Here, the wavelength is shortened due to the influence of the relative permittivity εr of the substrate 40. For example, if the substrate 40 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the substrate 40 is approximately 57.8%. Then, 1 / 2λ of 650 MHz is approximately 231 mm in free space, but on the substrate 40 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L1 of the broadband antenna 4 formed on the substrate 40 is approximately 135 mm, the resonant frequency of the broadband antenna 4 will be approximately 650 MHz. Here, as an example of approximate dimensions when the relative permittivity εr of the substrate 20 of the broadband antenna 4 is approximately 3 and the design frequency band is 650MHz to 2750MHz, the dimension L1 is approximately 135mm, the width W1 is approximately 50mm, and the thickness of the substrate 20 can be approximately 100μm. In this way, the broadband antenna 4 of the fourth embodiment is compact. The dimension of the long side of the substrate 40 is approximately the same as L1, and the dimension of the short side of the substrate 40 is approximately the same as W1. Furthermore, the length L2 of the protrusions 41b and 42b is preferably approximately 12mm to approximately 19.5mm, and the width of the protrusions 41b and 42b is, for example, approximately 2mm.

[0031] As described above, the broadband antenna 4 of the fourth embodiment of the present invention functions as a broadband antenna 4 with improved broadband performance because the first antenna element 41 and the second antenna element 42 are formed of a mesh-like conductive material in a planar shape, and two protrusions 41b are formed on the first antenna element 41 and two protrusions 42b are formed on the second antenna element 42. Furthermore, in the broadband antenna 4 of the fourth embodiment, the substrate 40 is a transparent substrate, and the first antenna element 41 and the second antenna element 42 are made of a mesh-like material that is visually transparent and transmits visible light, so the broadband antenna 4 of the fourth embodiment is transparent. As a result, the broadband antenna 4 of the fourth embodiment can be installed on the surface of a solar panel, for example, on a device that uses visible light, without compromising the appearance while maintaining the performance of the power generation function. Furthermore, by using a substrate such as a film made of a flexible resin as the substrate 40, and forming the first antenna element 41 and the second antenna element 42 on one surface of the substrate 40, it becomes flexible, allowing it to be installed on a curved surface of the mounting surface using the other surface of the substrate 40. [Industrial applicability]

[0032] The broadband antenna of the present invention has a broadband frequency characteristic, making it suitable for application to IoT devices where frequency ranges are expanding. In such cases, IoT devices may be installed in environments where commercial power is unavailable, and the communication modules built into IoT devices are often powered by secondary batteries. Solar panels are often provided to charge these secondary batteries. In this case, solar panels are usually installed on the exterior of the IoT device, but if the antenna required for the communication module, such as a broadband antenna, is installed inside the IoT device, the broadband antenna will be affected by the solar panel and will not be able to perform as required. That is, it is desirable to install the broadband antenna on top of the solar panel installed on the exterior of the IoT device, but if it is installed on top of the solar panel, the broadband antenna will block the sunlight, making it difficult for the solar panel to generate power to its full potential. Therefore, if the transparent broadband antenna of the present invention is installed on top of the solar panel, the solar panel will be sufficiently irradiated with sunlight, and the solar panel will be able to generate power to its full potential. Furthermore, the transparent broadband antenna of the present invention is visually transparent and transmits visible light, so it can be installed on the outer surface of IoT devices without compromising the design of the IoT devices. Even if the outer surface of the IoT device that is to be attached is curved, the broadband antenna of the present invention, which has a substrate made of a flexible and insulating transparent resin film, can be attached to the curved surface. In this case, since the patterns of the first antenna element, second antenna element, etc. that constitute the broadband antenna are formed on only one side of the substrate of the broadband antenna of the present invention, the other side of the substrate can be used as an adhesive layer to attach it to the mounting surface of the IoT device. Furthermore, the broadband antenna of the present invention can be applied not only to IoT devices but also to devices that have a built-in communication module. [Explanation of symbols]

[0033] 1 Broadband antenna, 2 Broadband antenna, 3 Broadband antenna, 4 Broadband antenna, 10 Film substrate, 11 First antenna element, 11a, 12a Feed point, 12 Second antenna element, 13 Feed cable, 13a Center conductor, 13b Outer conductor, 20 Substrate, 21 First antenna element, 21a, 22a Feed point, 21b, 22b Protrusion, 22 Second antenna element, 23 Feed cable, 23a Center conductor, 23b Outer conductor, 30 Substrate, 31 First antenna element, 31a, 32a Feed point, 31b, 32b Protrusion, 32 Second antenna element, 33 Feed cable, 33a Center conductor, 33b Outer conductor, 40 Substrate, 41 First antenna element, 41a, 42a Feed point, 41b, 42b Protrusion, 42 Second antenna element, 43 Feed cable, 43a Center conductor, 43b Outer conductor, 100 Planar antenna, 110 Insulating substrate, 111 First element, 111a First loop element, 111b First T-type element, 112 Second element, 112a Second loop element, 112b Second T-type element, 113 Unpowered element, 114a, 114b Feed section

Claims

1. An insulating substrate which is a flat, rectangular shape, The substrate comprises a first antenna element and a second antenna element, which are formed in a planar shape from a conductive material and arranged side by side on one side of the substrate. The first antenna element and the second antenna element are composed of a tapered portion that widens in a tapered shape and a rectangular portion that follows the tapered portion, and feed points are formed at the ends of the tapered portions where the first antenna element and the second antenna element face each other, and the tapered portion is formed to widen in a tapered shape from each of the feed points, and a plurality of protrusions are formed extending from the tapered portion, characterized in that the broadband antenna is characterized in this way.

2. The broadband antenna according to Claim 1, characterized in that the plurality of protrusions are two protrusions, formed at the start and end of the tapered portion, respectively.

3. The broadband antenna according to claim 2, characterized in that the lengths of the two protrusions formed on the first antenna element and the second antenna element are approximately 0.036λa to approximately 0.059λa with respect to the wavelength λa of free space at a frequency of 0.9 GHz in the design frequency band, and approximately 0.080λb to approximately 0.130λb with respect to the wavelength λb of free space at a frequency of 2.0 GHz.

4. A substrate made of an insulating transparent resin which is in the shape of a flat rectangular plate, The substrate comprises a first antenna element and a second antenna element formed in a planar manner on one side of the substrate, The first antenna element and the second antenna element are composed of a tapered portion that widens in a tapered shape and a rectangular portion that continues from the tapered portion, with feed points formed at the ends of the tapered portions where the first antenna element and the second antenna element face each other, and the tapered portion is formed to widen in a tapered shape from each of the feed points, and a projection is formed extending from the tapered portion. A broadband antenna characterized in that the first antenna element and the second antenna element, on which the protrusions are formed, are made of a mesh-like conductor that is visually transparent and transmits visible light except for the feed point, and the feed points of the first antenna element and the second antenna element are formed in a solid shape.

5. A film substrate made of an insulating transparent resin which is in the shape of a flat rectangular plate, The film substrate comprises a first antenna element and a second antenna element formed in a planar manner side by side on one surface. The first antenna element and the second antenna element are composed of a tapered portion that widens in a tapered shape and a rectangular portion that continues from the tapered portion, with feed points formed at the ends of the tapered portions where the first antenna element and the second antenna element face each other, and the tapered portion is formed to widen in a tapered shape from each of the feed points, and a projection is formed extending from the tapered portion. A broadband antenna characterized in that the first antenna element and the second antenna element, on which the protrusions are formed, are made of a mesh-like conductor consisting of triangular, square, polygonal, circular, or elliptical meshes that are visually transparent and transmit visible light except for the feed point, and the feed points of the first antenna element and the second antenna element are formed in a solid shape.

6. The broadband antenna according to claim 4 or 5, characterized in that the length of the protrusions formed on the first antenna element and the second antenna element is approximately 0.036λa to approximately 0.059λa with respect to the wavelength λa of free space at a frequency of 0.9 GHz in the design frequency band, and approximately 0.080λb to approximately 0.130λb with respect to the wavelength λb of free space at a frequency of 2.0 GHz.

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