Antenna equipment

Abstract

To enable mitigation of deterioration of performance of an antenna device even when a broadband antenna of the antenna device is used while being close to a metal body.SOLUTION: An antenna device 1 includes a broadband antenna 10, a first metal plate 21, and a second metal plate 22. The broadband antenna 10 is arranged on the first metal plate 21 and the second metal plate 22, and the first metal plate 21 and the second metal plate 22 serve as objects to which the broadband antenna 10 is attached. A slit portion 23 at which a region containing a power feeding point 12 and a power feeding point 13a is located is formed between the first metal plate 21 and the second metal plate 22. As a result, even when the broadband antenna 10 is used while being close to a metal body, deterioration in performance of the broadband antenna 10 can be mitigated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an antenna device capable of reducing deterioration of antenna performance even when used in proximity to a metal object.

Background Art

[0002] With the expansion of the IoT (Internet of Things) market, the frequency range used is expanding, and the demand for antennas with broadband characteristics is increasing. In addition, since the installation space for antennas for communication modules is limited, antennas may be used in proximity to metal objects that are not suitable as radio wave environment conditions. In that case, the metal object affects the inductive component and capacitive component of the antenna, changing the impedance of the antenna, which may cause significant deterioration of the antenna performance. Therefore, there is a need for an antenna with broadband characteristics and a need to reduce deterioration of antenna performance even when used in proximity to a metal object.

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 band to the 2000 MHz band. A front view of this conventional planar antenna 100 is shown in Figure 26 and a rear view in Figure 27. 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 elements 111 and second elements 112 formed on the front surface, one side of the insulating substrate 110. Furthermore, the feeding sections 114a, 114b and the parasitic element 113 are formed on the back surface, the other side of the insulating substrate 110. If a metal object is used in close proximity to the back surface, there is a risk that the performance of conventional planar antennas 100 will deteriorate significantly due to electrical coupling between the first elements 111, second elements 112 and the parasitic element 113, or a change in impedance. Therefore, the present invention aims to provide an antenna device that allows for a simple configuration of antenna elements and reduces performance degradation even when used in close proximity to a metal body. [Means for solving the problem]

[0006] The antenna device of the present invention comprises a metal plate and a broadband antenna disposed on the metal plate, wherein the broadband antenna comprises a flat rectangular insulating substrate and a first antenna element and a second antenna element formed of a conductive material in a planar shape on one side of the substrate, the first antenna element and the second antenna element being substantially symmetrical in shape, a feed point being formed approximately in the center of the ends of the first antenna element and the second antenna element facing each other, the first antenna element and the second antenna element being formed in a planar shape that tapers outwards from each of the feed points, and the metal plate is provided with a slit of a predetermined width, and the metal plate is positioned on the other side of the substrate in the broadband antenna such that the area including the feed point does not face the metal plate due to the slit. Furthermore, in the antenna device of the present invention, the insulating substrate in the broadband antenna is made of a transparent resin substrate, and the first antenna element and the second antenna element are formed of a mesh-like conductor that is visually transparent and transmits visible light. Furthermore, in the antenna device of the present invention, the insulating substrate in the broadband antenna is a film substrate made of transparent resin. Furthermore, in the antenna device of the present invention, when the wavelength of the center frequency in the design frequency band of the broadband antenna is λ, the width of the slit portion of the metal plate is approximately λ / 14.

[0007] Another antenna device of the present invention is an antenna device comprising a metal plate and a broadband antenna disposed on the metal plate, wherein the broadband antenna comprises a flat rectangular insulating substrate and a first antenna element and a second antenna element formed of a conductive material in a planar shape side by side on one surface of the substrate, with a feed point formed approximately in the center of the ends of the first antenna element and the second antenna element facing each other, the first antenna element and the second antenna element being formed in a planar shape that tapers outwards from each of the feed points, and protrusions extending from the tapered portion, and the first antenna element and the second antenna element being approximately symmetrical in shape, and the metal plate is provided with a slit of a predetermined width, and the metal plate is positioned on the other surface of the substrate in the broadband antenna such that the area including the feed point does not face the metal plate due to the slit. Furthermore, in another antenna device of the present invention, the insulating substrate in the broadband antenna is made of a transparent resin substrate, 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 antenna devices of the present invention, the insulating substrate in the broadband antenna 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 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 shape. Furthermore, in another antenna device of the present invention, the insulating substrate in the broadband antenna is a film substrate made of transparent resin. Furthermore, in another antenna device of the present invention, the length of the protrusions formed on the first antenna element and the second antenna element in the broadband antenna is set to a length of approximately 0.036λa to approximately 0.059λa with respect to the wavelength λa of a frequency of 0.9 GHz in the design frequency band, and to a length of approximately 0.080λb to approximately 0.130λb with respect to the wavelength λb of a frequency of 2.0 GHz. Furthermore, in another antenna device of the present invention, when the wavelength of the center frequency in the design frequency band of the broadband antenna is λ, the width of the slit portion of the metal plate is approximately λ / 14. [Effects of the Invention]

[0008] The antenna device of the present invention consists of a metal plate and a broadband antenna placed on the metal plate. The broadband antenna comprises a first antenna element and a second antenna element formed of a conductive material in a planar shape and arranged side by side on one side of the substrate. Even if the metal plate is placed on the other side of the substrate in the antenna device, the metal plate is provided with a slit of a predetermined width, so that the area including the feed point does not face the metal plate. As a result, even when the antenna device is used in close proximity to a metal body, the degradation of the performance of the broadband antenna can be reduced. Furthermore, by using a transparent resin substrate for the broadband antenna of the antenna device of the present invention, and 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 a metal body on the surface of a device that utilizes visible light without compromising the appearance while maintaining the performance of the device. Furthermore, if the substrate in the broadband antenna of the antenna device of the present invention is made of a film substrate made of transparent resin, it becomes flexible and can be installed on a curved surface of a metal body. [Brief explanation of the drawing]

[0009] [Figure 1]It is a front view showing the configuration of the antenna device according to the first embodiment of the present invention. [Figure 2] It is a rear view showing the configuration of the antenna device according to the first embodiment of the present invention. [Figure 3] It is a top view showing the configuration of the antenna device according to the first embodiment of the present invention. [Figure 4] It is a left side view and a right side view showing the configuration of the antenna device according to the first embodiment of the present invention. [Figure 5] It is a front view showing dimensions in the configuration of the antenna device according to the first embodiment of the present invention. [Figure 6] It is a front view showing the configuration of a modified example of the antenna device according to the first embodiment of the present invention. [Figure 7] It is a front view showing the configuration of the antenna device according to the second embodiment of the present invention. [Figure 8] It is a rear view showing the configuration of the antenna device according to the second embodiment of the present invention. [Figure 9] It is a top view showing the configuration of the antenna device according to the second embodiment of the present invention. [Figure 10] It is a left side view and a right side view showing the configuration of the antenna device according to the second embodiment of the present invention. [Figure 11] It is a front view showing dimensions in the configuration of the antenna device according to the second embodiment of the present invention. [Figure 12] It is a front view showing the configuration of the antenna device according to the third embodiment of the present invention. [Figure 13] It is a rear view showing the configuration of the antenna device according to the third embodiment of the present invention. [Figure 14] It is a top view showing the configuration of the antenna device according to the third embodiment of the present invention. [Figure 15] It is a left side view and a right side view showing the configuration of the antenna device according to the third embodiment of the present invention. [Figure 16] It is a front view showing the configuration of the antenna device according to the fourth embodiment of the present invention. [Figure 17] It is a rear view showing the configuration of the antenna device according to the fourth embodiment of the present invention. [Figure 18] The top view showing the configuration of the antenna device according to the fourth embodiment of the present invention. [Figure 19] The left side view and the right side view showing the configuration of the antenna device according to the fourth embodiment of the present invention. [Figure 20] The graph showing the VSWR 2.0 or less band with respect to the length of the protrusion of the antenna element in the planar antenna in the antenna device according to the second embodiment of the present invention. [Figure 21] The table showing the wavelength ratio of the length of the protrusion of the antenna element with respect to the wavelength of a predetermined design frequency in the planar antenna in the antenna device according to the second embodiment of the present invention. [Figure 22] The graph showing the VSWR 3.0 or less band with respect to the interval of the slit portions in the antenna device according to the first embodiment of the present invention. [Figure 23] The table showing the wavelength ratio of the interval of the slit portions with respect to the wavelength of a predetermined design frequency in the antenna device according to the first embodiment of the present invention. [Figure 24] The graph showing the VSWR 3.0 or less band with respect to the interval of the slit portions in the antenna device according to the second embodiment of the present invention. [Figure 25] The table showing the wavelength ratio of the interval of the slit portions with respect to the wavelength of a predetermined design frequency in the antenna device according to the second embodiment of the present invention. [Figure 26] The front view showing the configuration of the conventional planar antenna. [Figure 27] The rear view showing the configuration of the conventional planar antenna.

Embodiments for Carrying Out the Invention

[0010] <The antenna device according to the first embodiment of the present invention> The configuration of the antenna device 1 according to the first embodiment of the present invention is shown in Figures 1 to 4. Figure 1 is a front view showing the configuration of the antenna device 1 of the first embodiment, Figure 2 is a rear view showing the configuration of the antenna device 1 of the first embodiment, Figure 3 is a top view showing the configuration of the antenna device 1 of the first embodiment, Figure 4 is a left side view and a right side view showing the configuration of the antenna device 1 of the first embodiment, and Figure 5 is a front view showing the dimensions of the configuration of the antenna device 1 of the first embodiment. As shown in these figures, the antenna device 1 of the first embodiment of the present invention consists of a broadband antenna 10 and a first metal plate 21 and a second metal plate 22. In this case, the broadband antenna 10 is placed on the first metal plate 21 and the second metal plate 22, and the first metal plate 21 and the second metal plate 22 are the mounting bodies for the broadband antenna 10. The broadband antenna 10 in the antenna device 1 of the first embodiment includes a rectangular flat substrate 11, 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 12 and a second antenna element 13, are formed side by side on one surface of this substrate 11. The patterns of the first antenna element 12 and the second antenna element 13 are in a planar shape and are formed on one surface of the substrate 11 by vapor deposition, printing, bonding, etching, or the like. In this case, the substrate 11 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 12 and the second antenna element 13 are preferably conductive materials with low electrical resistance such as copper or silver paste. The illustrated substrate 11 is a vertically elongated rectangle, with the first antenna element 12 formed on the upper half and the second antenna element 13 formed on the lower half. The first antenna element 12 and the second antenna element 13 are formed in a shape that is almost symmetrical to the first antenna element 12 and the second antenna element 13, with feed points 12a and 13a formed approximately in the center of the ends of the first antenna element 12 and the second antenna element 13 facing each other. The first antenna element 12 consists of a tapered portion that widens from the feed point 12a to the periphery of the substrate 11 and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 11. The second antenna element 13 is formed in a shape that is almost symmetrical to the first antenna element 12 and consists of a tapered portion that widens from the feed point 13a to the periphery of the substrate 11 and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 11.

[0011] In the broadband antenna 10 of the antenna device 1 according to the first embodiment, the feed point 12a of the first antenna element 12 and the feed point 13a of the second antenna element 13 are formed in a thick rectangular shape, the tip of the central conductor 14a of the feed cable 14 which is a coaxial cable is soldered to the feed point 12a, and the outer conductor 14b of the feed cable 14 is soldered to the feed point 13a. In the antenna device 1 according to the first embodiment, the first metal plate 21 and the second metal plate 22 serve as mounting bodies for the broadband antenna 10, and the broadband antenna 10 is attached to the first metal plate 21 and the second metal plate 22 by adhesive or the like. The first metal plate 21 and the second metal plate 22 shown in the figure are rectangular in shape with a horizontally elongated shape and a predetermined width in the vertical direction, and a slit portion 23 is formed between the first metal plate 21 and the second metal plate 22. The region including the feed point 12a and the feed point 13a of the broadband antenna 10 is located within the spacing of this slit portion 23, so that the region including the feed point 12a and the feed point 13a does not face the first metal plate 21 and the second metal plate 22. As a result, even if the broadband antenna 10 of the antenna device 1 according to the first embodiment is used in close proximity to the first metal plate 21 and the second metal plate 22, the degradation of performance can be reduced. As shown in Figure 5, the dimensions of the first metal plate 21 and the second metal plate 22 are such that the lateral lengths of the illustrated first metal plate 21 and the second metal plate 22 are La1 and Lb1, respectively, the vertical widths are Wa1 and Wb1, respectively, and the spacing of the slit portion 23 is S. Also, as shown in Figure 5, the vertical dimension of the illustrated broadband antenna 10 is L2, and the horizontal dimension is W2.

[0012] The design frequency band of the antenna device 1 according to the first embodiment is, for example, 650 MHz to 2750 MHz, and an example of the dimensions of the broadband antenna 10 and the first metal plate 21 and second metal plate 22 is given. In this example, the broadband antenna 10 is made to resonate at the center frequency of the design frequency band to cover the design frequency band. In this case, when the wavelength of the center frequency of the design frequency band is λ, the length L2 of the broadband antenna 10 is set to approximately 1 / 2λ and the width W2 is set to approximately 1 / 4λ, so that the broadband antenna 10 functions as a dipole antenna that is centrally fed from the feed cable 14 and resonates at the aforementioned center frequency. In addition, the lengths La1 and Lb1 of the first metal plate 21 and the second metal plate 22 are approximately 3 / 4λ, the widths Wa1 and Wb1 of the first metal plate 21 and the second metal plate 22 are approximately 1 / 4λ, and the spacing S of the slits is approximately 1 / 14λ. Note that the lengths La1 and Lb1 are not limited to the dimensions above and can be any length, and the widths Wa1 and Wb1 are not limited to the dimensions above and can be wider. However, if the widths Wa1 and Wb1 are made wider, the resonant frequency of the broadband antenna 10 will shift. Another example involves resonating the broadband antenna 10 at a low frequency within the design frequency band, for example, 650 MHz, to cover the lower frequencies of the design frequency band. Regarding the specific dimensions of the broadband antenna 10 in this case, the wavelength is shortened on the substrate 11 due to the influence of the relative permittivity εr of the substrate 11. For example, if the substrate 11 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the substrate 11 is approximately 57.8%. Then, while half a wavelength of 650 MHz is approximately 231 mm in free space, on the substrate 11 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L2 of the broadband antenna 10 formed on the substrate 11 is approximately 135 mm, the resonant frequency of the broadband antenna 10 will be approximately 650 MHz. Therefore, when the relative permittivity εr of the substrate 11 of the broadband antenna 10 is set to approximately 3, the approximate dimensions of the broadband antenna 10 that covers the low frequencies of the design frequency band are, for example, a dimension L2 of approximately 135 mm and a width W2 of approximately 50 mm. In addition, the thickness of the substrate 11 can be approximately 100 μm. Thus, the broadband antenna 10 of the first embodiment is compact. The dimensions of the long side of the substrate 11 are approximately the same as L1, and the dimensions of the short side of the substrate 11 are approximately the same as W1.

[0013] Here, we explain the basis for the range of the spacing L3 of the slit portion 23 in the antenna device 1 of the first embodiment. In the antenna device 1 of the first embodiment of the present invention, the VSWR characteristics when the spacing S of the slit portion 23 between the first metal plate 21 and the second metal plate 22 is changed are shown in the graph in Figure 21. In this case, the horizontal axis is the spacing S of the slit portion 23 from 0 [mm] to 20 [mm], and the vertical axis is the VSWR 3.0 or less bandwidth. In the VSWR characteristics of the antenna device 1 of the first embodiment shown in Figure 21, the design frequency is set to 650MHz to 2750MHz. Referring to the VSWR characteristics shown in Figure 22, when the gap S of the slit portion 23 between the first metal plate 21 and the second metal plate 22 is 0mm, only a relative bandwidth of about 5% is obtained in the VSWR 3.0 or less band. This is thought to be because, since the slit portion 23 is not formed with a gap of 0mm, the performance of the antenna device 1 of the first embodiment deteriorates significantly due to the influence of the first metal plate 21 and the second metal plate 22. Next, when the gap S is changed to 2mm, a large relative bandwidth of about 84% is obtained in the VSWR 3.0 or less band. This is thought to be because the feed points 12a and 13a of the broadband antenna 10 are located in the slit portion 23, making them less susceptible to the influence of the first metal plate 21 and the second metal plate 22. Furthermore, when the interval S is varied from 2 mm to 20 mm, it can be seen that a large relative bandwidth of over 70% (approximately 72% to 85%) is obtained in the range of interval S from 2.0 mm to 20 mm, where the VSWR is below 3.0. As shown in the table in Figure 23, a spacing S of 2.0 mm corresponds to 0.006 λa if the wavelength at 900 MHz is λa, and to 0.013 λb if the wavelength at 2 GHz is λb. Furthermore, if the wavelength at the center frequency of the design frequency band is λ, the spacing S, which is approximately 1 / 14 λ, is approximately 12 mm.

[0014] As described above, in the antenna device 1 of the first embodiment of the present invention, the first antenna element 12 and the second antenna element 13 of the broadband antenna 10 are formed of a conductive material in a planar shape, and thus function as a broadband antenna. Furthermore, in the antenna device 1 of the first embodiment, by making the substrate 11 a substrate made of a flexible resin, such as a film, and forming the patterns of the first antenna element 12, the second antenna element 13 and the feed points 12a and 13a on one surface of the substrate 11, the broadband antenna 10 according to the antenna device 1 of the first embodiment of the present invention becomes flexible, and by providing an adhesive layer on the other surface of the substrate 31, the antenna device 1 can be made such that the broadband antenna 10 can be attached to the curved first metal plate 21 and the second metal plate 22. Furthermore, in the antenna device 1 of the first embodiment, the substrate 11 is made of a transparent resin, and the first antenna element 12 and the second antenna element 13 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 12 and the second antenna element 13 visually transparent and transmit visible light in a mesh-like form, the broadband antenna 10 in the antenna device 1 of the first embodiment can be made transparent. This makes it possible to install the broadband antenna 10 on the surface of a device having a metal body that utilizes visible light, such as a solar panel, by adhesive or the like without compromising the appearance while maintaining the performance of the power generation function. In this case, the solar panel has electrodes that are made of metal, and these electrodes correspond to the first metal plate 21 and the second metal plate 22, with a slit portion 23 provided between the electrodes of the first metal plate 21 and the second metal plate 22.

[0015] <Modified example of the antenna device of the first embodiment of the present invention> Next, an antenna device 2, which is a modified version of the antenna device 1 of the first embodiment of the present invention, will be described. The modified antenna device 2 is a modified version of the antenna device 1 of the first embodiment of the present invention in which the number of metal plates has been increased. Figure 6 shows the configuration of an antenna device 2, which is a modified version of the antenna device 1 of the first embodiment of the present invention. Figure 6 is a front view showing the configuration of the modified antenna device 2. As shown in Figure 6, the antenna device 2, which is a modified version of the antenna device 1 of the first embodiment, consists of a broadband antenna 10 and a first metal plate 21 and a second metal plate 22. In this case, the broadband antenna 10 has a third metal plate 24 and a fourth metal plate 25 in addition to the first metal plate 21 and the second metal plate 22. The broadband antenna 10 is placed on the first metal plate 21 and the second metal plate 22. The first to fourth metal plates 21 to 4 metal plates 25 are metal bodies provided in a single device, and the first to fourth metal plates 21 to 4 metal plates 25 are the mounting bodies for the broadband antenna 10. Furthermore, a slit portion 23a is formed between the first metal plate 21 and the second metal plate 22, a slit portion 23b is formed between the first metal plate 21 and the third metal plate 24, a slit portion 23c is formed between the second metal plate 22 and the fourth metal plate 25, and slit portions 23a to 23c are formed between adjacent metal plates of the first metal plate 21 to the fourth metal plate 25.

[0016] In the modified antenna device 2, the configuration of the broadband antenna 10 is as described in the description of antenna device 1 of the first embodiment, so the description is omitted here. The first metal plate 21 to the fourth metal plate 25 are the same shape and dimensions, and the spacing of the slit portions 23a to 23c is also the same. That is, the lateral length of the first metal plate 21 to the fourth metal plate 25 shown in the figure is L10, the vertical width of the first metal plate 21 to the fourth metal plate 25 is W10, and the spacing of the slit portions 23a to 23c is S10. In the modified antenna device, which is a modified version of the antenna device 1 of the first embodiment, the design frequency band is, for example, 650MHz to 2750MHz. As an example of the dimensions of the first metal plate 21 to the fourth metal plate 25 in this case, when the wavelength of the center frequency of the design frequency band is λ, the length L10 of the first metal plate 21 to the fourth metal plate 25 is approximately 3 / 4λ, the width W10 of the first metal plate 21 to the fourth metal plate 25 is approximately 1 / 4λ, and the spacing S10 of the slit portions 23a to 23c is approximately 1 / 14λ. Note that the length L10 is not limited to the above dimensions and can be any length, and the width W10 is not limited to the above dimensions and can be wider. However, if the width W10 is wider, the resonant frequency of the broadband antenna 10 will shift. Note that the dimensions of the broadband antenna 10 are as described in the description of the antenna device 1 of the first embodiment, so that description is omitted here. In the antenna device 2, which is a modified version of the antenna device 1 of the first embodiment of the present invention, the VSWR characteristics when the spacing S of the slit portions 23a to 23c between adjacent metal plates of the first metal plate 21 to the fourth metal plate 25 is changed are as shown in the graph in Figure 21 described above. Also, as shown in the table in Figure 22, a spacing S of 2.0 mm corresponds to 0.006 λa if the wavelength at 900 MHz is λa, and corresponds to 0.013 λb if the wavelength at 2 GHz is λb.

[0017] <Antenna device according to a second embodiment of the present invention> Next, an antenna device 3 according to a second embodiment of the present invention will be described. The antenna device 3 of the second embodiment improves the broadband performance of the antenna device 1 of the first embodiment by providing protrusions 32b and 33b on the first antenna element 32 and the second antenna element 33 of the broadband antenna 30. The configuration of the antenna device 3 of the second embodiment of the present invention is shown in Figures 7 to 10. Figure 7 is a front view showing the configuration of the antenna device 3 of the second embodiment, Figure 8 is a rear view showing the configuration of the antenna device 3 of the second embodiment, Figure 9 is a top view showing the configuration of the antenna device 3 of the second embodiment, and Figure 10 is a left side view and a right side view showing the configuration of the antenna device 3 of the second embodiment. As shown in these figures, the antenna device 3 of the second embodiment of the present invention consists of a broadband antenna 30 and a first metal plate 21 and a second metal plate 22. In this case, the broadband antenna 30 is placed on the first metal plate 21 and the second metal plate 22, and the first metal plate 21 and the second metal plate 22 are the mounting parts for the broadband antenna 30. The first metal plate 21 and the second metal plate 22 can be electrodes, for example, electrodes of a solar panel, in which case a slit portion 23 will be provided between the electrodes of the first metal plate 21 and the second metal plate 22.

[0018] The broadband antenna 30 in the antenna device 3 of the second embodiment includes a rectangular flat substrate 31, 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 32 and a second antenna element 33, are formed side by side on one surface of this substrate 31. The patterns of the first antenna element 32 and the second antenna element 33 are in a planar shape and are formed on one surface of the substrate 31 by vapor deposition, printing, bonding, etching, or the like. In this case, the substrate 31 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 32 and the second antenna element 33 are preferably conductive materials with low electrical resistance such as copper or silver paste. The illustrated substrate 31 is a vertically elongated rectangle, with the first antenna element 32 formed on the upper half and the second antenna element 33 formed on the lower half. The first antenna element 32 and the second antenna element 33 are formed in a shape that is almost symmetrical to the first antenna element 32, and feed points 32a and 33a are formed approximately in the center of the ends of the first antenna element 32 and the second antenna element 33 that face each other. The first antenna element 32 is composed of a tapered portion that widens from the feed point 32a to the periphery of the substrate 31, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 31. The second antenna element 33 is formed in a shape that is almost symmetrical to the first antenna element 32, and is composed of a tapered portion that widens from the feed point 33a to the periphery of the substrate 31, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 31. Furthermore, two elongated protrusions 32b are formed on one of the tapered portions of the first antenna element 32, extending from the starting end near the feed point 32a and from the end that reaches the periphery of the substrate 31. Similarly, in the second antenna element 33, two elongated protrusions 33b are formed, extending from the starting end near the feed point 33a in one of the tapered portions of the second antenna element 33 and from the end reaching the periphery of the substrate 31.

[0019] In the broadband antenna 30 of the second embodiment, the feed point 32a of the second antenna element 32 and the feed point 33a of the second antenna element 33 are formed with a thick, rectangular solid pattern and are solderable. The tip of the central conductor 34a of the feed cable 34, which is a coaxial cable, is soldered to the feed point 32a, and the outer conductor 34b of the feed cable 34 is soldered to the feed point 33a. In the second embodiment of the antenna device 3, the first metal plate 21 and the second metal plate 22 serve as mounting bodies for the broadband antenna 30, with the broadband antenna 30 attached to the first metal plate 21 and the second metal plate 22 by adhesive or the like. The illustrated first metal plate 21 and the second metal plate 22 are rectangular in shape with a horizontally elongated shape and a predetermined vertical width, and a slit portion 23 is formed between the first metal plate 21 and the second metal plate 22. The area that substantially includes the feed points 32a and 33a of the broadband antenna 30, and the two protrusions 32b of the first antenna element 32 and the two protrusions 33b of the second antenna element 33 is located within the spacing of this slit portion 23, so that the area substantially including the feed points 32a and 33a and the two protrusions 32b and 33b does not face the first metal plate 21 and the second metal plate 22. As a result, even if the broadband antenna 30 of the antenna device 3 according to the second embodiment is used in close proximity to the first metal plate 21 and the second metal plate 22, the degradation of performance can be reduced.

[0020] The dimensions of each part of the antenna device 3 of the second embodiment are the same as those of the antenna device 1 of the first embodiment, and a diagram showing the dimensions of the antenna device 3 of the second embodiment is shown in Figure 11. As shown in Figure 11, the dimensions of the first metal plate 21 and the second metal plate 22 are La1 and Lb1 in the horizontal direction, respectively, and Wa1 and Wb1 in the vertical direction, respectively, and the spacing of the slit portion 23 is S. In addition, as shown in Figure 11, the dimensions of the broadband antenna 30 are L2 in the vertical direction and W2 in the horizontal direction. Furthermore, the length in the extension direction of the two protrusions 32b and the two protrusions 33b is L3, and the width in the direction perpendicular to the extension direction is a predetermined width. The lengths L3 of the two protrusions 32b and 33b may be the same or different. The two protrusions 32b formed on the first antenna element 32 and the two protrusions 33b formed on the second antenna element 33 allow for adjustment of the inductive (L) component and capacitive (C) component in the first antenna element 32 and the second antenna element 33. By making this adjustment, the broadband capability of the broadband antenna 30 of the antenna device 3 of the second embodiment is improved, and the antenna device 3 of the second embodiment can be made even broader. The adjustment of the L and C components can be done by changing the lengths L3 and widths of the two protrusions 32b and 33b. The number of protrusions 32b and 33b is not limited to two; there may be one or three or more. The protrusions 32b and 33b may be provided symmetrically or asymmetrically. In other words, the shape and position of the protrusions 32b and 33b are not limited to those shown in the illustration. As long as they can be positioned in the space formed between the tapered portion between the first antenna element 32 and the second antenna element 33, which are arranged facing each other, the shape and position of the protrusions 32b and 33b can be any shape and position.

[0021] The design frequency band of the antenna device 3 according to the second embodiment is, for example, 650 MHz to 2750 MHz, and an example of the dimensions of the broadband antenna 30 and the first metal plate 21 and second metal plate 22 is given. In this example, the broadband antenna 30 is made to resonate at the center frequency of the design frequency band to cover the design frequency band. In this case, when the wavelength of the center frequency of the design frequency band is λ, the length L2 of the broadband antenna 30 is set to approximately 1 / 2λ and the width W2 is set to approximately 1 / 4λ, so that the broadband antenna 30 functions as a dipole antenna that is centrally fed from the feed cable 34 and resonates at the aforementioned center frequency. In this case, the dimensions of the substrate 31 are approximately the same as the length L2 and width W2 of the broadband antenna 30. Furthermore, the lengths La1 and Lb1 of the first metal plate 21 and the second metal plate 22 are approximately 3 / 4λ, the widths Wa1 and Wb1 of the first metal plate 21 and the second metal plate 22 are approximately 1 / 4λ, and the spacing S of the slit portion 23 is approximately 1 / 14λ. Note that the lengths La1 and Lb1 are not limited to the above dimensions and can be any length, and the widths Wa1 and Wb1 are not limited to the above dimensions and can be wider. However, if the widths Wa1 and Wb1 are widened, the resonant frequency of the broadband antenna 30 will shift. Another example involves resonating the broadband antenna 30 at a low frequency within the design frequency band, for example, 650 MHz, to cover the lower frequencies of the design frequency band. Regarding the specific dimensions of the broadband antenna 30 in this case, the wavelength is shortened on the substrate 31 due to the influence of the relative permittivity εr of the substrate 31. For example, if the substrate 31 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the substrate 31 is approximately 57.8%. Then, while half a wavelength of 650 MHz is approximately 231 mm in free space, on the substrate 31 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L2 of the broadband antenna 30 formed on the substrate 31 is approximately 135 mm, the resonant frequency of the broadband antenna 30 will be approximately 650 MHz. Therefore, when the relative permittivity εr of the substrate 31 of the broadband antenna 30 is set to approximately 3, the approximate dimensions of the broadband antenna 30 that covers the low frequencies of the design frequency band are, for example, a dimension L2 of approximately 135 mm and a width W2 of approximately 50 mm. In addition, the thickness of the substrate 31 can be approximately 100 μm. Thus, the broadband antenna 30 in the antenna device 3 of the second embodiment is compact. The dimension of the long side of the substrate 31 is approximately the same as L2, and the dimension of the short side of the substrate 31 is approximately the same as W2. The length L3 of the protrusions 32b and 33b is approximately 12 mm to approximately 19.5 mm, and the width of the protrusions 32b and 33b is, for example, approximately 2 mm.

[0022] Here, we show the basis for the range of length L3 of the protrusions 32b and 33b in the broadband antenna 30 of the antenna device 3 of the second embodiment. In the antenna device 3 of the second embodiment of the present invention, with a design frequency band of 650MHz to 2750MHz and the above dimensions excluding the protrusions 32b and 33b, the VSWR characteristics of the antenna device 3 of the second embodiment are shown in the graph in Figure 20 when the length L3 of the total of four protrusions, the two protrusions 32b of the first antenna element 32 and the two protrusions 33b of the second antenna element 33, is changed simultaneously by the same dimension. In this case, the horizontal axis is the length L3 of the protrusions 32b and 33b from 0 [mm] to 20 [mm], and the vertical axis is the VSWR 2.0 or less band. In this case, the width of the protrusions 32b and 33b is approximately 2 mm. Referring to the VSWR characteristics shown in Figure 20, when the length L3 of the protrusions 32b and 33b of the first antenna element 32 and the second antenna element 33 is 0 mm, the protrusions 32b and 33b are not formed, which corresponds to the VSWR characteristics of the antenna device 1 of the first embodiment, and a wide bandwidth of approximately 39% is obtained as the bandwidth in which the VSWR is 2.0 or less. Next, when the length L3 of the protrusions 32b and 33b of the first antenna element 32 and the second antenna element 33 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 32b and 33b. Furthermore, referring to the VSWR characteristics shown in Figure 20, the length L3 of the protrusions 32b and 33b that result in a relative bandwidth of 70% or more with a VSWR of 2.0 or less is approximately 12 mm to approximately 19.5 mm, and a relative bandwidth of approximately 70% to approximately 90% is obtained within this range of length L3. Thus, the fact that a relative bandwidth of 70% or more with a VSWR of 2.0 or less can be obtained is due to the effect of providing the protrusions 32b and 33b. As shown in the table in Figure 21, 12 mm corresponds to 0.036 λa when the wavelength at 900 MHz is λa, and to 0.08 λb when the wavelength at 2 GHz is λb. Similarly, 19.5 mm corresponds to 0.059 λa when the wavelength at 900 MHz is λa, and to 0.130 λb when the wavelength at 2 GHz is λb.

[0023] Next, the basis for the range of spacing L3 of the slit portion 23 spacing S in the antenna device 3 of the second embodiment will be shown. In the antenna device 3 of the second embodiment of the present invention, with a design frequency band of 650MHz to 2750MHz and the above dimensions except for the slit portion 23 spacing S, the VSWR characteristics when the spacing S of the slit portion 23 between the first metal plate 21 and the second metal plate 22 is changed are shown in the graph in Figure 24. In this case, the horizontal axis is the spacing S of the slit portion 23 from 0 [mm] to 20 [mm], and the vertical axis is the VSWR 3.0 or less band. In this case, the length L3 of the protrusions 32b and 33b of the first antenna element 32 and the second antenna element 33 is approximately 12 mm, and the width of the protrusions 32b and 33b is approximately 2 mm. In the VSWR characteristics of the antenna device 3 of the second embodiment shown in Figure 24, the design frequency is set to 650MHz to 2750MHz. Referring to the VSWR characteristics shown in Figure 24, when the gap S of the slit portion 23 between the first metal plate 21 and the second metal plate 22 is 0mm, only a relative bandwidth of about 10% is obtained in the VSWR 3.0 or less band. This is thought to be because, since the slit portion 23 is not formed with a gap of 0mm, the performance of the antenna device 3 of the second embodiment deteriorates significantly due to the influence of the first metal plate 21 and the second metal plate 22. Next, as the gap S is increased beyond 0mm, the relative bandwidth increases as the gap increases, and when the gap S reaches about 7.5mm, a large relative bandwidth of about 70% is obtained. This is thought to be because the feed points 32a, 33a and most of the protrusions 32b, 33b of the broadband antenna 30 are located in the slit portion 23, making them less susceptible to the influence of the first metal plate 21 and the second metal plate 22. Furthermore, as the spacing S is increased beyond 7.5 mm, the relative bandwidth continues to rise, and when the spacing S reaches slightly over 10 mm, a relative bandwidth of approximately 100% is obtained. As the spacing S is further increased, the relative bandwidth gradually decreases, but when the spacing S reaches 20 mm, a large relative bandwidth of approximately 80% is obtained. In other words, within the range of spacing S of the slit section 23 from 7.5 mm to 20 mm, a large relative bandwidth of approximately 70% to approximately 100% can be obtained, exceeding approximately 70%. As shown in the table in Figure 25, a spacing S of 8.0 mm corresponds to 0.024λa if the wavelength at 900 MHz is λa, and to 0.053λb if the wavelength at 2 GHz is λb. Furthermore, if the wavelength at the center frequency of the design frequency band is λ, the spacing S, which is approximately 1 / 14λ, is approximately 12 mm.

[0024] As described above, the antenna device 3 of the second embodiment of the present invention functions as an antenna device 3 with improved broadband performance because the first antenna element 32 and the second antenna element 33 are formed of a conductive material in a planar shape, and two protrusions 32b are formed on the first antenna element 32 and two protrusions 33b are formed on the second antenna element 33. Furthermore, in the antenna device 3 of the second embodiment, by using a substrate 31 made of a flexible resin, and forming a pattern of the first antenna element 32, the second antenna element 33 and feed points 32a, 33a on one surface of the substrate 31, the broadband antenna 30 of the antenna device 3 of the second embodiment of the present invention becomes flexible, and by providing an adhesive layer on the other surface of the substrate 31, the antenna device 3 can be made capable of attaching the broadband antenna 30 to the curved first metal plate 21 and the second metal plate 22.

[0025] <Broadband antenna according to the third embodiment of the present invention> Next, an antenna device 4 according to a third embodiment of the present invention will be described. In the antenna device 4 of the third embodiment, the broadband antenna 40 of the antenna device 4 of the third embodiment is made transparent by forming the first antenna element 42 and the second antenna element 43 from a mesh-like conductive material. Next, the configuration of the antenna device 4 of the third embodiment of the present invention is shown in Figures 12 to 15. Figure 12 is a front view showing the configuration of the antenna device 4 of the third embodiment, Figure 13 is a rear view showing the configuration of the antenna device 4 of the third embodiment, Figure 14 is a top view showing the configuration of the antenna device 4 of the third embodiment, and Figure 15 is a left side view and a right side view showing the configuration of the antenna device 4 of the third embodiment. As shown in these figures, the antenna device 4 of the third embodiment of the present invention consists of a broadband antenna 40 and a first metal plate 21 and a second metal plate 22. In this case, the broadband antenna 40 is placed on the first metal plate 21 and the second metal plate 22, and the first metal plate 21 and the second metal plate 22 are the mounting parts for the broadband antenna 40. The first metal plate 21 and the second metal plate 22 can be electrodes, for example, electrodes of a solar panel, in which case a slit portion 23 will be provided between the electrodes of the first metal plate 21 and the second metal plate 22.

[0026] The broadband antenna 40 in the antenna device 4 of the third embodiment includes a rectangular flat substrate 41, 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 42 and a second antenna element 43, are formed side by side on one surface of this substrate 41. The patterns of the first antenna element 42 and the second antenna element 43 are in a planar shape and are formed on one surface of the substrate 41 by vapor deposition, printing, bonding, etching, or the like. In this case, the substrate 41 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 42 and the second antenna element 43 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 41 is a vertically elongated rectangle, with a mesh-like first antenna element 42 formed on the upper half and a mesh-like second antenna element 43 formed on the lower half. The first antenna element 42 and the second antenna element 43 are approximately symmetrical in shape, and feed points 42a and 43a are formed approximately in the center of the ends of the first antenna element 42 and the second antenna element 43 facing each other. The first antenna element 42 consists of a tapered portion that widens from the feed point 42a to the periphery of the substrate 41, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 41. The second antenna element 43 is formed in a shape that is approximately symmetrical to the first antenna element 42, and consists of a tapered portion that widens from the feed point 43a to the periphery of the substrate 41, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 41. Furthermore, two elongated protrusions 42b are formed on the first antenna element 42, extending from the starting end near the feed point 42a on one tapered portion and from the end reaching the periphery of the substrate 41. Similarly, on the second antenna element 43, two elongated protrusions 43b are formed, extending from the starting end near the feed point 43a on one tapered portion and from the end reaching the periphery of the substrate 41. The two protrusions 42b and the two protrusions 43b can be formed in a mesh pattern.

[0027] In the antenna device 4 of the third embodiment, the first antenna element 42 and the second antenna element 43 are formed from a mesh-like conductor, where the mesh is square and the spacing between the mesh in both the vertical and horizontal directions is D. For example, the mesh spacing D 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 42 and the second antenna element 43 become transparent. Note that the dimensions of the mesh spacing D 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.

[0028] Furthermore, in the antenna device 4 of the third embodiment, the feed point 42a of the first antenna element 42 and the feed point 43a of the second antenna element 43 are formed with a thick rectangular solid pattern and are solderable. The tip of the central conductor 44a of the feed cable 44, which is a coaxial cable, is soldered to the feed point 42a, and the outer conductor 44b of the feed cable 44 is soldered to the feed point 43a. In the third embodiment of the antenna device 4, the first metal plate 21 and the second metal plate 22 serve as mounting bodies for the broadband antenna 40, with the broadband antenna 40 attached to the first metal plate 21 and the second metal plate 22 by adhesive or the like. The illustrated first metal plate 21 and the second metal plate 22 are rectangular in shape with a horizontally elongated shape and a predetermined vertical width, and a slit portion 23 is formed between the first metal plate 21 and the second metal plate 22. The area that substantially includes the feed points 42a and 43a of the broadband antenna 40, and the two protrusions 42b of the first antenna element 42 and the two protrusions 43b of the second antenna element 43 is located within the spacing of this slit portion 23, so that the area substantially including the feed points 42a and 43a and the two protrusions 42b and 43b does not face the first metal plate 21 and the second metal plate 22. As a result, even if the broadband antenna 40 of the antenna device 4 according to the third embodiment is used in close proximity to the first metal plate 21 and the second metal plate 22, the degradation of performance can be reduced.

[0029] The dimensions of each part of the antenna device 4 in the third embodiment are the same as those of the antenna device 5 in the second embodiment. Although not shown, the lateral lengths of the first metal plate 21 and the second metal plate 22 are La1 and Lb1, respectively, and the vertical widths are Wa1 and Wb1, respectively, and the spacing of the slit portion 23 is S. The dimensions of the broadband antenna 40 are L2 in the vertical direction and W2 in the horizontal direction. Furthermore, the length in the extension direction of the two protrusions 42b and the two protrusions 43b is L3, and the width in the direction perpendicular to the extension direction is a predetermined width. The lengths L3 of the two protrusions 42b and 53b may be the same or different. The two protrusions 42b formed on the first antenna element 42 and the two protrusions 43b formed on the second antenna element 43 allow for adjustment of the L and C components in the first antenna element 42 and the second antenna element 43. By making this adjustment, the broadband performance of the broadband antenna 40 of the antenna device 4 of the third embodiment is improved, and the antenna device 4 of the third embodiment can be made even broader. The above adjustment of the L and C components can be done by changing the lengths L3 and widths of the two protrusions 42b and 43b. The number of protrusions 42b and 43b is not limited to two; there may be one or three or more. The protrusions 42b and 43b may be provided symmetrically or asymmetrically. In other words, the shape and protruding position of the protrusions 42b and 43b are not limited to those shown in the figures. If they can be placed in the space formed between the tapered portion between the first antenna element 42 and the second antenna element 43 which are positioned facing each other, the shape and position of the protrusions 42b and 43b can be any shape and position.

[0030] The design frequency band of the antenna device 4 according to the third embodiment is, for example, 650 MHz to 2750 MHz, and an example of the dimensions of the broadband antenna 40 and the first metal plate 21 and second metal plate 22 is given. In this example, the broadband antenna 40 is made to resonate at the center frequency of the design frequency band to cover the design frequency band. In this case, when the wavelength of the center frequency of the design frequency band is λ, the length L2 of the broadband antenna 40 is set to approximately 1 / 2λ and the width W2 is set to approximately 1 / 4λ, so that the broadband antenna 40 functions as a dipole antenna that is centrally fed from the feed cable 44 and resonates at the aforementioned center frequency. In this case, the dimensions of the substrate 41 are approximately the same as the length L2 and width W2 of the broadband antenna 40. Furthermore, the lengths La1 and Lb1 of the first metal plate 21 and the second metal plate 22 are approximately 3 / 4λ, the widths Wa1 and Wb1 of the first metal plate 21 and the second metal plate 22 are approximately 1 / 4λ, and the spacing S of the slit portion 23 is approximately 1 / 14λ. Note that the lengths La1 and Lb1 are not limited to the above dimensions and can be any length, and the widths Wa1 and Wb1 are not limited to the above dimensions and can be wider. However, if the widths Wa1 and Wb1 are widened, the resonant frequency of the broadband antenna 30 will shift. Another example involves resonating the broadband antenna 40 at a low frequency within the design frequency band, for example, 650 MHz, to cover the lower frequencies of the design frequency band. Regarding the specific dimensions of the broadband antenna 40 in this case, the wavelength is shortened on the substrate 41 due to the influence of the relative permittivity εr of the substrate 41. For example, if the substrate 41 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the substrate 31 is approximately 57.8%. Then, while half a wavelength of 650 MHz is approximately 231 mm in free space, on the substrate 41 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L2 of the broadband antenna 40 formed on the substrate 41 is approximately 135 mm, the resonant frequency of the broadband antenna 40 will be approximately 650 MHz. Therefore, when the relative permittivity εr of the substrate 41 of the broadband antenna 40 is set to approximately 3, the approximate dimensions of the broadband antenna 40 that covers the lower frequencies of the design frequency band are, for example, a dimension L2 of approximately 135 mm and a width W2 of approximately 50 mm. In addition, the thickness of the substrate 41 can be approximately 100 μm. Thus, the broadband antenna 40 in the antenna device 4 of the third embodiment is compact. The dimension of the long side of the substrate 41 is approximately the same as L2, and the dimension of the short side of the substrate 41 is approximately the same as W2. The length L3 of the protrusions 42b and 43b is approximately 12 mm to approximately 19.5 mm, and the width of the protrusions 42b and 43b is, for example, approximately 2 mm.

[0031] Here, the basis for the range of lengths L3 of the protrusions 42b and 43b in the broadband antenna 40 of the antenna device 4 of the third embodiment is the same as that for the antenna device 3 of the second embodiment. In the antenna device 4 of the third embodiment of the present invention, where the design frequency band of the antenna device 4 of the third embodiment is 650MHz to 2750MHz and the above dimensions are set excluding the protrusions 42b and 43b, the VSWR characteristics when the lengths L3 of the four protrusions, the two protrusions 42b of the first antenna element 42 and the two protrusions 43b of the second antenna element 43, are simultaneously changed by the same dimension are as shown in the graph in Figure 20. In this case, the width of the protrusions 42b and 43b is approximately 2mm. As shown in the graph in Figure 20, the length L3 of the protrusions 42b and 43b that result in a relative bandwidth of 70% or more with a VSWR of 2.0 or less is approximately 12mm to approximately 19.5mm, and a relative bandwidth of approximately 70% to approximately 90% can be obtained within this range of length L3. The fact that a relative bandwidth of 70% or more can be obtained with a VSWR of 2.0 or less is due to the effect of providing protrusions 42b and 43b.

[0032] Next, the basis for the range of the spacing L3 of the slit portion 23 in the antenna device 4 of the third embodiment is the same as that for the antenna device 3 of the second embodiment. In the antenna device 4 of the third embodiment of the present invention, where the design frequency band of the antenna device 4 of the third embodiment is 650MHz to 2750MHz and the dimensions are as described above except for the spacing S of the slit portion 23, the VSWR characteristics when the spacing S of the slit portion 23 between the first metal plate 21 and the second metal plate 22 is changed are as shown in the graph in Figure 24 above. In this case, the length L3 of the protrusions 42b and 43b of the first antenna element 42 and the second antenna element 43 is approximately 12mm, and the width of the protrusions 32b and 33b is approximately 2mm. Although a detailed explanation will be omitted, in the antenna device 4 of the third embodiment of the present invention, when the spacing S of the slit portion 23 is changed from more than 7.5 mm to 20 mm, a large relative bandwidth of 70% or more can be obtained in the VSWR 3.0 or less band, ranging from approximately 70% to approximately 100%, in the range of spacing S from 7.5 mm to 20 mm. This is thought to be because the feed points 42a, 43a and most of the protrusions 42b, 43b of the broadband antenna 40 are located in the slit portion 23, making them less susceptible to the influence of the first metal plate 21 and the second metal plate 22. If the wavelength of the center frequency of the design frequency band is λ, the spacing S, which is approximately 1 / 14λ, is approximately 12 mm.

[0033] As described above, the antenna device 4 of the third embodiment of the present invention functions as an antenna device 4 with improved broadband performance, as the first antenna element 42 and the second antenna element 43 are formed of a mesh-like conductor that is visually transparent in a planar shape and transmits visible light, and two protrusions 42b are formed on the first antenna element 42 and two protrusions 43b are formed on the second antenna element 43. Furthermore, in the antenna device 4 of the third embodiment, by using a substrate 41 made of a flexible resin, such as a film, and forming a pattern of the first antenna element 42, the second antenna element 43 and feed points 42a, 43a on one surface of the substrate 41, the broadband antenna 40 of the antenna device 4 of the third embodiment of the present invention becomes flexible, and by providing an adhesive layer on the other surface of the substrate 41, the antenna device 4 can be made capable of attaching the broadband antenna 40 to the curved first metal plate 21 and the second metal plate 22. Furthermore, in the antenna device 4 of the third embodiment, the substrate 41 is made of a transparent resin substrate, and the first antenna element 42 and the second antenna element 43 are formed of a mesh-like conductor that is visually transparent and transmits visible light, so that the broadband antenna 40 in the antenna device 4 of the third embodiment can be made transparent. As a result, the broadband antenna 40 can be attached by adhesive or the like to the surface of a device having a metal body that utilizes visible light, such as a solar panel, without compromising the appearance while maintaining the performance of the power generation function. In this case, the solar panel has electrodes that are made of metal, and these electrodes correspond to the first metal plate 21 and the second metal plate 22, with a slit portion 23 provided between the electrodes of the first metal plate 21 and the second metal plate 22.

[0034] Next, the antenna device 5 of the fourth embodiment of the present invention will be described. The antenna device 5 of the fourth embodiment is a modified version of the antenna device 4 of the third embodiment of the present invention. Specifically, the shape of the conductive mesh forming the first antenna element 52 and the second antenna element 53 has been changed. Next, the configuration of the antenna device 5 of the fourth embodiment of the present invention is shown in Figures 16 to 19. Figure 16 is a front view showing the configuration of the antenna device 5 of the fourth embodiment, Figure 17 is a rear view showing the configuration of the antenna device 5 of the fourth embodiment, Figure 18 is a top view showing the configuration of the antenna device 5 of the fourth embodiment, and Figure 19 is a left side view and a right side view showing the configuration of the antenna device 5 of the fourth embodiment. As shown in these figures, the antenna device 5 of the fourth embodiment of the present invention consists of a broadband antenna 50 and a first metal plate 21 and a second metal plate 22. In this case, the broadband antenna 50 is placed on the first metal plate 21 and the second metal plate 22, and the first metal plate 21 and the second metal plate 22 are the mounting parts for the broadband antenna 50. The first metal plate 21 and the second metal plate 22 can be electrodes, for example, electrodes of a solar panel, in which case a slit portion 23 will be provided between the electrodes of the first metal plate 21 and the second metal plate 22.

[0035] The broadband antenna 50 in the antenna device 5 of the fourth embodiment includes a rectangular flat substrate 51, 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 52 and a second antenna element 53, are formed side by side on one surface of this substrate 51. The patterns of the first antenna element 52 and the second antenna element 53 are in a planar shape and are formed on one surface of the substrate 51 by vapor deposition, printing, bonding, etching, or the like. In this case, the substrate 51 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 52 and the second antenna element 53 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 51 is a vertically elongated rectangle, with a mesh-like first antenna element 52 formed on the upper half and a mesh-like second antenna element 53 formed on the lower half. The first antenna element 52 and the second antenna element 53 are approximately symmetrical in shape, and feed points 52a and 53a are formed approximately in the center of the ends of the first antenna element 52 and the second antenna element 53 facing each other. The first antenna element 52 consists of a tapered portion that widens from the feed point 52a to the periphery of the substrate 51, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 51. The second antenna element 53 is formed in a shape that is approximately symmetrical to the first antenna element 52, and consists of a tapered portion that widens from the feed point 53a to the periphery of the substrate 51, and a rectangular portion that follows the tapered portion and is approximately along the periphery of the substrate 51. Furthermore, two elongated protrusions 52b are formed on the first antenna element 52, extending from the starting end near the feed point 52a on one tapered portion and from the end reaching the periphery of the substrate 51. Similarly, on the second antenna element 53, two elongated protrusions 53b are formed, extending from the starting end near the feed point 53a on one tapered portion and from the end reaching the periphery of the substrate 51. The two protrusions 52b and the two protrusions 53b can be formed in a mesh pattern.

[0036] In the antenna device 5 of the fourth embodiment, the first antenna element 52 having two protrusions 52b and the second antenna element 53 having two protrusions 53b are formed from a mesh-like conductor, but the mesh in the mesh-like conductor is triangular instead of square. The dimensions of the mesh spacing and the width of the lines forming the mesh are such that a mesh that is visually transparent and transmits visible light is obtained. Furthermore, the shape of the mesh is not limited to triangles, but can be polygonal, a combination of polygons, a circle, an ellipse, or any other shape that is visually transparent and transmits visible light. As a result, the first antenna element 52 and the second antenna element 53 become transparent.

[0037] Furthermore, in the antenna device 5 of the fourth embodiment, the feed point 52a of the first antenna element 52 and the feed point 53a of the second antenna element 53 are formed with a thick rectangular solid pattern and are solderable. The tip of the central conductor 54a of the feed cable 54, which is a coaxial cable, is soldered to the feed point 52a, and the outer conductor 54b of the feed cable 54 is soldered to the feed point 53a. In the antenna device 5 according to the fourth embodiment, the first metal plate 21 and the second metal plate 22 serve as mounting bodies for the broadband antenna 50, and the broadband antenna 50 is attached to the first metal plate 21 and the second metal plate 22 by adhesive or the like. The first metal plate 21 and the second metal plate 22 shown in the figure are rectangular in shape with a horizontally elongated shape and a predetermined width in the vertical direction, and a slit portion 23 is formed between the first metal plate 21 and the second metal plate 22. The area that substantially includes the feed points 52a and 53a of the broadband antenna 50, and the two protrusions 52b of the first antenna element 52 and the two protrusions 53b of the second antenna element 53 is located within the spacing of this slit portion 23, so that the area that substantially includes the feed points 52a and 53a and the two protrusions 52b and 53b does not face the first metal plate 21 and the second metal plate 22. As a result, even if the broadband antenna 50 of the antenna device 5 according to the fourth embodiment is used in close proximity to the first metal plate 21 and the second metal plate 22, the degradation of performance can be reduced.

[0038] The dimensions of each part of the antenna device 5 in the fourth embodiment are the same as those of the antenna device 4 in the third embodiment. Although not shown, the lateral lengths of the first metal plate 21 and the second metal plate 22 are La1 and Lb1, respectively, and their vertical widths are Wa1 and Wb1, respectively, and the spacing of the slit portion 23 is S. The dimensions of the broadband antenna 50 are L2 in the vertical direction and W2 in the horizontal direction. Furthermore, the length in the extension direction of the two protrusions 52b and the two protrusions 53b is L3, and the width in the direction perpendicular to the extension direction is a predetermined width. The lengths L3 of the two protrusions 52b and 53b may be the same or different. The two protrusions 52b formed on the first antenna element 52 and the two protrusions 53b formed on the second antenna element 53 allow for adjustment of the L and C components in the first antenna element 52 and the second antenna element 53. By making this adjustment, the broadband performance of the broadband antenna 50 of the antenna device 5 of the fourth embodiment is improved, and the antenna device 5 of the fourth embodiment can be made even broader. The above adjustment of the L and C components can be done by changing the lengths L3 and widths of the two protrusions 52b and 53b. The number of protrusions 52b and 53b is not limited to two; there may be one or three or more. The protrusions 52b and 53b may be provided symmetrically or asymmetrically. In other words, the shape and protruding position of the protrusions 52b and 53b are not limited to those shown in the figures. If they can be placed in the space formed between the tapered portion between the first antenna element 52 and the second antenna element 53 which are positioned facing each other, the shape and position of the protrusions 52b and 53b can be any shape and position.

[0039] The design frequency band of the antenna device 5 according to the fourth embodiment is, for example, 650 MHz to 2750 MHz, and an example of the dimensions of the broadband antenna 50 and the first metal plate 21 and second metal plate 22 is given. In this example, the broadband antenna 50 is made to resonate at the center frequency of the design frequency band to cover the design frequency band. In this case, when the wavelength of the center frequency of the design frequency band is λ, the length L2 of the broadband antenna 50 is set to approximately 1 / 2λ and the width W2 is set to approximately 1 / 4λ, so that the broadband antenna 50 functions as a dipole antenna that is centrally fed from the feed cable 54 and resonates at the aforementioned center frequency. In this case, the dimensions of the substrate 51 are approximately the same as the length L2 and width W2 of the broadband antenna 50. Furthermore, the lengths La1 and Lb1 of the first metal plate 21 and the second metal plate 22 are approximately 3 / 4λ, the widths Wa1 and Wb1 of the first metal plate 21 and the second metal plate 22 are approximately 1 / 4λ, and the spacing S of the slit portion 23 is approximately 1 / 14λ. Note that the lengths La1 and Lb1 are not limited to the above dimensions and can be any length, and the widths Wa1 and Wb1 are not limited to the above dimensions and can be wider. However, if the widths Wa1 and Wb1 are widened, the resonant frequency of the broadband antenna 30 will shift. Another example involves resonating the broadband antenna 50 at a low frequency within the design frequency band, for example, 650 MHz, to cover the lower frequencies of the design frequency band. Regarding the specific dimensions of the broadband antenna 50 in this case, the wavelength is shortened on the substrate 51 due to the influence of the relative permittivity εr of the substrate 51. For example, if the substrate 51 is made of PET with a relative permittivity εr of approximately 3, the wavelength shortening rate of the substrate 51 is approximately 57.8%. Then, while half a wavelength of 650 MHz is approximately 231 mm in free space, on the substrate 51 with a relative permittivity εr of approximately 3, the wavelength is shortened to approximately 133.5 mm. Therefore, if the dimension L2 of the broadband antenna 50 formed on the substrate 51 is approximately 135 mm, the resonant frequency of the broadband antenna 50 will be approximately 650 MHz. Therefore, when the relative permittivity εr of the substrate 51 of the broadband antenna 50 is set to approximately 3, the approximate dimensions of the broadband antenna 50 that covers the low frequencies of the design frequency band are, for example, a dimension L2 of approximately 135 mm and a width W2 of approximately 50 mm. In addition, the thickness of the substrate 51 can be approximately 100 μm. Thus, the broadband antenna 50 in the antenna device 5 of the fourth embodiment is compact. The dimension of the long side of the substrate 51 is approximately the same as L2, and the dimension of the short side of the substrate 51 is approximately the same as W2. The length L3 of the protrusions 52b and 53b is approximately 12 mm to approximately 19.5 mm, and the width of the protrusions 52b and 53b is, for example, approximately 2 mm.

[0040] Here, the basis for the range of lengths L3 of the protrusions 52b and 53b in the broadband antenna 50 of the antenna device 5 of the fourth embodiment is the same as that for the antenna device 3 of the second embodiment. In the antenna device 5 of the fourth embodiment of the present invention, where the design frequency band of the antenna device 5 of the fourth embodiment is 650MHz to 2750MHz and the dimensions are as described above except for the protrusions 52b and 53b, the VSWR characteristics when the lengths L3 of the four protrusions, the two protrusions 52b of the first antenna element 52 and the two protrusions 53b of the second antenna element 53, are simultaneously changed by the same dimension are as shown in the graph in Figure 20. In this case, the width of the protrusions 52b and 53b is approximately 2mm. As shown in the graph in Figure 20, the length L3 of the protrusions 52b and 53b that result in a relative bandwidth of 70% or more with a VSWR of 2.0 or less is approximately 12mm to approximately 19.5mm, and a relative bandwidth of approximately 70% to approximately 90% can be obtained within this range of length L3. The fact that a relative bandwidth of 70% or more can be obtained with a VSWR of 2.0 or less is due to the effect of providing protrusions 52b and 53b.

[0041] Next, the basis for the range of the spacing L3 of the slit portion 23 in the antenna device 5 of the fourth embodiment is the same as that for the antenna device 3 of the second embodiment. In the antenna device 5 of the fourth embodiment of the present invention, where the design frequency band of the antenna device 5 of the fourth embodiment is 650MHz to 2750MHz and the dimensions are as described above except for the spacing S of the slit portion 23, the VSWR characteristics when the spacing S of the slit portion 23 between the first metal plate 21 and the second metal plate 22 is changed are as shown in the graph in Figure 24 above. In this case, the length L3 of the protrusions 52b and 53b of the first antenna element 52 and the second antenna element 53 is approximately 12mm, and the width of the protrusions 52b and 53b is approximately 2mm. Although a detailed explanation will be omitted, in the antenna device 5 of the fourth embodiment of the present invention, when the spacing S of the slit portion 23 is changed from more than 7.5 mm to 20 mm, a large relative bandwidth of 70% or more can be obtained in the VSWR 3.0 or less band, ranging from approximately 70% to approximately 100%, in the range of spacing S from 7.5 mm to 20 mm. This is thought to be because the feed points 52a, 53a and most of the protrusions 52b, 53b of the broadband antenna 50 are located in the slit portion 23, making them less susceptible to the influence of the first metal plate 21 and the second metal plate 22. If the wavelength of the center frequency of the design frequency band is λ, the spacing S, which is approximately 1 / 14λ, is approximately 12 mm.

[0042] As described above, in the antenna device 5 of the fourth embodiment of the present invention, the first antenna element 52 and the second antenna element 53 are formed of a mesh-like conductor that is visually transparent in a planar shape and transmits visible light, and two protrusions 52b are formed on the first antenna element 52 and two protrusions 53b are formed on the second antenna element 53, so that the antenna device 5 functions as an antenna device 5 with improved broadband performance. Furthermore, in the antenna device 5 of the fourth embodiment, by making the substrate 51 a substrate made of a flexible resin, for example a film, and forming the patterns of the first antenna element 52, the second antenna element 53 and the feed points 52a, 53a on one surface of the substrate 51, the broadband antenna 50 according to the antenna device 5 of the fourth embodiment of the present invention becomes flexible, and by providing an adhesive layer on the other surface of the substrate 51, the antenna device 5 can be made such that the broadband antenna 50 can be attached to the curved first metal plate 21 and the second metal plate 22. Furthermore, in the antenna device 5 of the fourth embodiment, the substrate 51 is made of a transparent resin substrate, and the first antenna element 52 and the second antenna element 53 are formed of a mesh-like conductor that is visually transparent and transmits visible light, so that the broadband antenna 50 in the antenna device 5 of the fourth embodiment can be made transparent. As a result, the broadband antenna 50 can be attached by adhesive or the like to the surface of a device having a metal body that utilizes visible light, such as a solar panel, without compromising the appearance while maintaining the performance of the power generation function. In this case, the solar panel has electrodes that are made of metal, and these electrodes correspond to the first metal plate 21 and the second metal plate 22, with a slit portion 23 provided between the electrodes of the first metal plate 21 and the second metal plate 22. [Industrial applicability]

[0043] The antenna device of the embodiment of the present invention described above is configured to have a broadband antenna mounted on two metal bodies, but it is not limited to this configuration, and the broadband antenna may be mounted on more than two metal bodies. In this case, the region including the feed point of the broadband antenna is located in a slit provided between the metal plates. The antenna device according to the embodiment of the present invention is suitable for application to IoT devices where frequency expansion is progressing, as it allows a broadband antenna to be mounted on a metal body and has broadband frequency characteristics. In such cases, IoT devices may be installed in environments where commercial power is unavailable, and the communication module built into the IoT device is often powered by a secondary battery. Furthermore, a solar panel is often provided to charge the secondary battery. In this case, the solar panel is usually installed on the outside 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 not be able to perform as required due to the influence of the solar panel. In addition, since solar panels have electrodes and electrodes are conductors, the performance of the broadband antenna will deteriorate if it is installed on top of a solar panel. However, since the antenna device according to the embodiment of the present invention allows a broadband antenna to be mounted on a metal body, by applying the antenna device according to the embodiment of the invention, the broadband antenna can be installed on top of a solar panel installed on the outside of the IoT device. In this case, by making the broadband antenna in the antenna device of the embodiment of the present invention transparent, it is possible to prevent the solar panel from being unable to generate power to its full potential due to the obstruction of sunlight. That is, by applying the antenna device of the present invention and installing the transparent broadband antenna on top of the solar panel, the solar panel will be sufficiently illuminated by sunlight, allowing it to generate power to its full potential. Furthermore, since the antenna device of the present invention is equipped with a transparent broadband antenna, and the broadband antenna is visually transparent and transmits visible light, it can be installed on the exterior surface of an IoT device without compromising the design of the IoT device. Moreover, even if the exterior surface on which the IoT device is 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 even to a curved surface.In this case, since the broadband antenna according to the present invention has patterns of first antenna elements, second antenna elements, etc., constituting the broadband antenna formed on only one surface of the substrate, the other surface of the substrate can be used as an adhesive layer to attach it to the mounting surface of an IoT device. Furthermore, the antenna device of the present invention can be applied not only to IoT devices but also to devices that incorporate communication modules, especially devices having a metal body. [Explanation of symbols]

[0044] 1 Antenna device, 2 Antenna device, 3 Antenna device, 4 Antenna device, 5 Antenna device, 10 Broadband antenna, 11 Substrate, 12 First antenna element, 12a, 13a Feed point, 13 Second antenna element, 14 Feed cable, 14a Center conductor, 14b Outer conductor, 21 First metal plate, 22 Second metal plate, 23 Slit section, 23a~23c Slit section, 24 First metal plate, 25 Second metal plate, 30 Broadband antenna, 31 Substrate, 32 First antenna element, 32a, 33a Feed point, 32b, 33b Protrusion, 33 Second antenna element, 34 Feed cable, 34a Center conductor, 34b Outer conductor, 40 Broadband antenna, 41 Substrate, 42 First antenna element, 42a, 43a Feed point, 42b, 43b Protrusion, 43 44 Second antenna element, 44 feed cable, 44a center conductor, 44b outer conductor, 50 broadband antenna, 51 substrate, 52 first antenna element, 52a, 53a feed point, 52b, 53b protrusion, 53 second antenna element, 54 feed cable, 54a center conductor, 54b 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 point

Claims

1. An antenna device comprising a metal plate and a broadband antenna placed on the metal plate, The aforementioned broadband antenna is An insulating substrate which is a flat, rectangular plate, It consists of a first antenna element and a second antenna element formed of a conductive material in a planar shape and arranged side by side on one surface 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, 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. An antenna device characterized in that the metal plate is provided with slits at predetermined intervals, the feed point is located within the predetermined intervals of the slits so that the feed point does not face the metal plate, and the metal plate is arranged on the other side of the substrate in the broadband antenna.

2. The antenna device according to claim 1, characterized in that the insulating substrate in the broadband antenna is made of a transparent resin substrate, and further, the first antenna element and the second antenna element are formed of a mesh-like conductor that is visually transparent and transmits visible light.

3. The antenna device according to claim 2, characterized in that the insulating substrate in the broadband antenna is a film substrate made of transparent resin.

4. The antenna device according to any one of claims 1 to 3, characterized in that, when the wavelength of the center frequency in the design frequency band of the antenna device is λ, the predetermined spacing of the slit portion provided in the metal plate is approximately λ / 14.

5. An antenna device comprising a metal plate and a broadband antenna placed on the metal plate, The aforementioned broadband antenna is An insulating substrate which is a flat, rectangular plate, It consists of a first antenna element and a second antenna element formed of a conductive material in a planar shape and arranged side by side on one surface 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 first antenna element and the second antenna element facing 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. An antenna device characterized in that the metal plate is provided with slits at predetermined intervals, the feed point and the protrusion are located within the predetermined intervals of the slits so that the feed point and the protrusion do not face each other on the metal plate, and the metal plate is arranged on the other side of the substrate in the broadband antenna.

6. The antenna device according to claim 5, characterized in that the insulating substrate in the broadband antenna is a substrate made of transparent resin, and further, 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.

7. The antenna device according to claim 6, characterized in that the insulating substrate in the broadband antenna is a film substrate made of transparent resin.

8. The antenna device according to claim 5, characterized in that the insulating substrate in the broadband antenna is a substrate made of transparent resin, and further, 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 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 shape.

9. The antenna device according to claim 8, characterized in that the insulating substrate in the broadband antenna is a film substrate made of transparent resin.

10. The antenna device according to any one of claims 5 to 9, characterized in that the length of the protrusions formed on the first antenna element and the second antenna element in the broadband antenna is approximately 0.036λa to approximately 0.059λa with respect to the wavelength λa of 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 a frequency of 2.0 GHz.

11. The antenna device according to any one of claims 5 to 9, characterized in that, when the wavelength of the center frequency in the design frequency band of the broadband antenna is λ, the predetermined spacing of the slit portions provided in the metal plate is approximately λ / 14.

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