Antenna device

Abstract

An antenna device according to an embodiment of the present invention comprises: a folding-back element that includes a first line portion and a second line portion disposed so as to be oriented toward each other with a prescribed spacing therebetween and respectively having base end portions connected to each other; a plate-shaped power-feeding side element that links a power feeding line and the end portion of the first line portion on the opposite side from the base end portion; and a ground element that links a ground conductor and the end portion of the second line portion on the opposite side from the base end portion. The power-feeding side element has a first end portion linked to the power feeding line and a second end portion on the opposite side from the first end portion. The end portion of the first line portion is linked to a plate-width direction end portion of the second end portion. When the power-feeding side element is viewed in a plan view, the contours of the power-feeding side element have an inverse tapered shape of which the width increases in the direction from the first end portion side toward the second end portion side.

Description

Antenna device

[0001] The present disclosure relates to an antenna device. This application claims priority based on Japanese Application No. 2024-179864 filed on October 15, 2024, and incorporates all the descriptions described in the above Japanese application.

[0002] Conventionally, a folded antenna may be used as a multi-band antenna for a mobile station in a mobile communication system. The folded antenna has linear first and second element portions that are arranged to face each other by being folded. The folded antenna further includes an element that connects the tip of the first element portion and the feeding point, and a ground element that is connected to the tip of the second line portion (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Application Publication No. 2007-28213

[0004] The antenna device according to an embodiment includes a folded element including first and second line portions whose base ends are connected to each other and are arranged to face each other with a predetermined interval therebetween, a plate-shaped feeding-side element that connects an end portion on the opposite side of the base end portion in the first line portion and a feeding line, and a ground element that connects an end portion on the opposite side of the base end portion in the second line portion and a ground conductor. The feeding-side element has a first end portion connected to the feeding line and a second end portion opposite to the first end portion. The end portion of the first line portion is connected to the end portion in the plate width direction of the second end portion. The contour of the feeding-side element in a plan view has a tapered shape in which the width expands from the first end portion side toward the second end portion side.

[0005] Figure 1 is a perspective view showing an example of an antenna device according to the first embodiment. Figure 2 is a plan view of the antenna device according to the first embodiment. Figure 3 is a plan view of the feeding side element in the first embodiment. Figure 4 is a perspective view of an antenna device according to the second embodiment. Figure 5 is a plan view of the feeding side element in Figure 4. Figure 6 is a perspective view of an antenna device according to the third embodiment. Figure 7A is an enlarged view of the main part of the feeding side element of the antenna device according to the fourth embodiment. Figure 7B is a diagram showing the equivalent circuit of the matching circuit. Figure 8 is a perspective view of an antenna device according to the fifth embodiment. Figure 9 is a plan view of the feeding side element in the fifth embodiment. Figure 10 is a plan view of the antenna device in Figure 8. Figure 11 is an enlarged view of the main part of the plate-shaped element in Figure 8. Figure 12 is an enlarged view of the main part of the folded element in Figure 8. Figure 13 is a perspective view of an antenna device according to the sixth embodiment. Figure 14 is a perspective view of an antenna device according to the seventh embodiment. Figure 15 is a perspective view of an antenna device according to the eighth embodiment. Figure 16A shows a modified example of the feed-side element in Figure 5. Figure 16B shows another modified example of the feed-side element in Figure 5. Figure 17A is a plan view of a plate-shaped element according to a modified example of the sixth embodiment. Figure 17B is a plan view of a plate-shaped element according to a modified example of the sixth embodiment. Figure 18 is a perspective view of an antenna device according to a comparative example. Figure 19 is an example of a graph showing the frequency characteristics of the return loss for Example 1 and the comparative example. Figure 20 is an example of a graph showing the frequency characteristics of the return loss for Example 2 and the comparative example. Figure 21 is an example of a graph showing the frequency characteristics of the return loss for Example 3 and the comparative example. Figure 22 is a Smith chart showing the input impedance of the antenna device according to Example 3. Figure 23 is an example of a graph showing the frequency characteristics of the return loss for an antenna device in which an inductance element is provided before the feed-side element. Figure 24 is an example of a graph showing the frequency characteristics of the return loss for an antenna device in which an inductance element is provided before the feed-side element. Figure 25 is an example of a graph showing the frequency characteristics of the return loss for Example 4 and the comparative example. Figure 26 is an example of a graph showing the frequency characteristics of the total efficiency in Example 4.Figure 27 is an example of a graph showing the frequency characteristics of the return loss for Example 5 and the Comparative Example. Figure 28 is an example of a graph showing the frequency characteristics of the total efficiency for Example 5. Figure 29 is an example of a graph showing the frequency characteristics of the return loss for Example 4, Example 7, and Example 8.

[0006] [Problems this disclosure aims to solve] In the above-mentioned mobile communication systems, multiband operation is progressing, and there is a demand for wider bandwidth in antennas for mobile stations. However, while multiband operation is achieved with the above-mentioned folded antennas, there have been cases where a bandwidth wide enough to cover the required frequency range has not been obtained.

[0007] Therefore, this disclosure aims to provide an antenna device that supports a wide bandwidth.

[0008] [Effects of this disclosure] According to this disclosure, an antenna device that supports a wide bandwidth can be obtained.

[0009] First, the details of the embodiment will be listed and explained. [Overview of the Embodiment]

[0010] (1) The antenna device according to the embodiment includes a folded element including a first line section and a second line section, the base ends of which are connected and which are arranged opposite to each other at a predetermined distance apart; a plate-shaped feeding-side element connecting the end of the first line section opposite to the base end to the feeding line; and a grounding element connecting the end of the second line section opposite to the base end to the grounding conductor. The feeding-side element has a first end connected to the feeding line and a second end opposite to the first end. The end of the first line section is connected to the plate width end of the second end. When the feeding-side element is viewed from above, its contour has a tapered shape, widening from the first end to the second end. With the above configuration, since the contour of the feeding-side element has a tapered shape, widening from the first end to the second end, the change in the characteristic impedance of the feeding-side element from the feeding line to the folded element can be made gradual. This reduces the return loss of the antenna device for signals across a relatively wide frequency band. As a result, an antenna device that can handle a wide frequency band can be obtained.

[0011] (2) In the antenna device described in (1) above, if the contour has a side portion along the extending direction of the first line portion at the second end side, it may further include a plate-shaped element that extends from the side portion of the feeding element along a direction intersecting the extending direction and has an open end at its tip. In this case, a predetermined resonant frequency can be given to the path of the plate-shaped element and the feeding element combined. Therefore, by adjusting the length of the plate-shaped element, the resonant frequency of the path of the plate-shaped element and the feeding element combined can be adjusted, and the return loss in a band different from the resonant frequency of the folded element can be reduced. This makes it possible to widen the frequency band that the antenna device can handle.

[0012] (3) In the antenna device described in (2) above, the feeding element and the grounding element are erected on a substrate having the feeding line, and the first line portion and the second line portion are supported by the feeding element and the grounding element so as to be parallel to and opposite to the substrate surface of the substrate, the intersecting direction may be the direction in which the plate-shaped element is positioned opposite to the substrate surface. In this case, since the plate-shaped element is positioned opposite to the substrate surface, the posture (height) of the antenna device with respect to the substrate surface can be made lower.

[0013] (4) In the antenna device described in (3) above, the plate-shaped element may have through holes that penetrate in the thickness direction of the plate. In this case, when the substrate surface is viewed from the front, the portion of the substrate surface covered by the plate-shaped element can be seen through the through holes. Therefore, it is possible to prevent the plate-shaped element from interfering with the inspection of mounted components on the substrate surface when viewing the substrate surface from the front.

[0014] (5) In the antenna device of (1) above, if the plate surface of the first line section facing the second line section includes a facing surface that faces the second line section and a protruding surface that protrudes beyond the end of the second line section, the device may further include a connecting portion that connects the end of the first line section and the end of the second end in the plate width direction, such that the feeding element is positioned facing the protruding surface. In this case, the folded element can be extended to a longer length, and the adjustable range of the resonant frequency of the folded element is expanded.

[0015] (6) In the antenna device of (1) or (2) above, the feeding element and the grounding element are erected on a substrate having the feeding line, the first line section and the second line section are supported by the feeding element and the grounding element so as to be parallel to and facing the substrate surface of the substrate, the grounding conductor is provided on the substrate, and the antenna device further includes a branching element connecting either the first line section or the second line section to the substrate surface, the branching element may have a third end connected to either the first line section or the second line section and a fourth end capacitively coupled with the grounding conductor provided on the substrate. In this case, the resonant frequency of the folded element can be appropriately adjusted by adjusting the capacitance between the grounding conductor and the branching element. In this case, the folded element is also supported on the substrate surface by the branching element in addition to the feeding element and the grounding element. As a result, the folded element is supported on the substrate surface in a stable state.

[0016] (7) In the antenna device described in (6) above, if the folded element has a folded connection portion that connects the base ends of the two base ends, the third end may be connected to either a position in the first line section that is closer to the folded connection portion than the end of the first line section, or a position in the second line section that is closer to the folded connection portion than the end of the second line section. In this case, the distance between the branching element and the power supply element, and the distance between the branching element and the grounding element can be made relatively large, and the folded element is supported in a more stable state with respect to the substrate surface.

[0017] (8) In the antenna device of (6) or (7) above, the folded element has an element body portion and an element bending portion, which are arranged in order along the direction from the end of the first line portion and the end of the second line portion toward both base ends, and the element body portion and the element bending portion are connected so as to bend along a plane parallel to the substrate surface, the third end portion may be connected to either the portion of the first line portion included in the element bending portion or the portion of the second line portion included in the element bending portion. In this case, it becomes easy to place the antenna device 1 at the corner of the circuit board.

[0018] (9) In any one of the antenna devices described in (1) to (8) above, a signal having a frequency included in either a first frequency band or a second frequency band higher than the first frequency band is fed from the feed line, and the device further includes a matching circuit provided between the feed line and the first end, wherein the resonant frequency of the matching circuit is a frequency between the first frequency band and the second frequency band, the inductance value of the matching circuit when the frequency of the signal is higher than the resonant frequency and the inductance value of the matching circuit when the frequency of the signal is lower than the resonant frequency may be different from each other. In this case, by appropriately adjusting the inductance value of the matching circuit, even if the input impedance characteristics when a signal in the first frequency band is fed to the feed-side element are different from the input impedance characteristics when a signal in the second frequency band is fed to the feed-side element, both the signal in the first frequency band and the signal in the second frequency band can be appropriately matched.

[0019] (10) In any one of the antenna devices described in (1) to (9) above, the first line section, the second line section, and the grounding element may each have a strip shape made of conductive metal. In this case, for example, an antenna device comprising the feed-side element, the first line section, the second line section, and the grounding element can be easily obtained by cutting an intermediate processed product, which includes at least the portion of the feed-side element, the portion of the first line section, the portion of the second line section, and the portion of the grounding element, from a single conductive metal plate, and then bending the intermediate processed product.

[0020] (11) In the antenna device described in (10) above, the width dimension of the first line section may be smaller than the width dimension of the second line section. In this case, the change in the input impedance of the antenna device with respect to frequency can be suppressed, and the bandwidth of the antenna device can be easily increased.

[0021] (12) In any one of the antenna devices described in (1) to (11) above, at least one of the pairs of connected combinations of the grounding element, the first line section, the second line section, and the grounding element may be integrally formed by bending a single conductive metal plate. In this case, the antenna device can be easily obtained.

[0022] [Details of Embodiments] Preferred embodiments will be described below with reference to the drawings. At least a part of each embodiment described below may be arbitrarily combined. [About the First Embodiment] Figure 1 is a perspective view showing an example of an antenna device according to the first embodiment. Figure 2 is a plan view of the antenna device according to the first embodiment. This antenna device 1 is used, for example, in a mobile station of a mobile communication system mounted on a vehicle such as a passenger car, bus, or railway vehicle. The antenna device 1 is mounted on a circuit board of an electronic device having wireless communication functionality. The antenna device 1 can be used in a fifth-generation mobile communication system. Therefore, the antenna device 1 is a multiband antenna compatible with LTE and SUB6, etc.

[0023] In the following explanation, the three mutually orthogonal directions in each figure will be referred to as the X, Y, and Z directions. Furthermore, one direction in the X direction will be referred to as the X1 direction, and the opposite direction of the X1 direction will be referred to as the X2 direction. One direction in the Y direction will be referred to as the Y1 direction, and the opposite direction of the Y1 direction will be referred to as the Y2 direction. One direction in the Z direction will be referred to as the Z1 direction, and the opposite direction of the Z1 direction will be referred to as the Z2 direction. Figure 2 is a plan view of the antenna device 1 as seen from the Z1 direction side.

[0024] The antenna device 1 is mounted on the circuit board 2. The circuit board 2 is a substrate included in an electronic device having wireless communication capabilities. The circuit board 2 is a rectangular rigid substrate arranged along the X-Y plane. Each side of the circuit board 2 is aligned along either the X or Y direction. The circuit board 2 has a substrate surface 2a. The substrate surface 2a is the surface of the circuit board 2 facing the Z1 direction. The antenna device 1 is mounted on the substrate surface 2a side of the circuit board 2. The circuit board 2 comprises a substrate body 3 and a grounding conductor plate 4.

[0025] The substrate body 3 is a rectangular plate-shaped member formed of a dielectric material. The grounding conductor plate 4 is a conductive pattern made of copper or the like, provided on the substrate surface 2a side of the circuit board 2. The grounding conductor plate 4 is provided so as to cover almost the entire surface of the substrate body 3 facing the Z1 direction. In other words, the grounding conductor plate 4 is provided over almost the entire area of ​​the substrate surface 2a. The grounding conductor plate 4 is grounded. Note that the grounding conductor plate 4 does not have to be provided over the entire area; it is sufficient if it is provided in the necessary locations on the substrate surface 2a.

[0026] The circuit board 2 also has a power supply line 5. The power supply line 5 is a conductive pattern made of copper or the like, provided on the substrate surface 2a side. The power supply line 5 is provided inside the slit 4a of the grounding conductor plate 4. The slit 4a is a rectangular cutout provided so as to extend in the X1 direction from the side 4b of the grounding conductor plate 4. The substrate body 3 is exposed inside the slit 4a. The power supply line 5 is provided on the exposed surface of the substrate body 3 inside the slit 4a. A small gap is provided between the edge of the power supply line 5 and the edge of the grounding conductor plate 4 in the slit 4a. The power supply line 5, together with the portions of the grounding conductor plate 4 on both sides of the power supply line 5, constitutes a coplanar line. In this embodiment, a plurality of vias 6 are arranged on both sides of the slit 4a in the Y direction. The plurality of vias 6 penetrate the substrate body 3 and are connected to the grounding conductor plate 4.

[0027] The power supply line 5 has a power supply point 5a and a connection part 5b. The power supply point 5a is provided at the end of the power supply line 5 on the X1 direction side. The connection part 5b is provided at the end of the power supply line 5 on the X2 direction side. A signal source S, such as a communication module for wireless communication, is connected to the power supply point 5a. An antenna device 1 is connected to the connection part 5b.

[0028] The antenna device 1 is formed using a conductive metal plate such as copper or brass. Therefore, each part of the antenna device 1 is plate-shaped. The antenna device 1 comprises a folded element 10, a feed-side element 12, a grounding element 14, and a connection part 24. The folded element 10 is arranged to face the substrate surface 2a at a predetermined distance. In a plan view, the folded element 10 is arranged along the edge 2c (edge ​​4b) of the circuit board 2. Edge 2c is the edge of the circuit board 2 that is along the Y direction on the X2 direction side. The folded element 10 has a first line section 18, a second line section 20, and a folded connection part 22.

[0029] The first track section 18 is a strip-shaped member extending along the Y direction. The width direction of the first track section 18 is along the Z direction. In other words, the strip surface of the first track section 18 is along the Y-Z plane. The second track section 20 is a strip-shaped member extending along the Y direction. The width direction of the second track section 20 is along the Z direction. In other words, the strip surface of the second track section 20 is along the Y-Z plane.

[0030] The first track section 18 and the second track section 20 are aligned along the X direction. The first track section 18 and the second track section 20 are positioned opposite each other with a predetermined distance between them. The first track section 18 and the second track section 20 are positioned opposite each other such that their respective strip surfaces are parallel.

[0031] The width dimension (width dimension in the Z direction) of the first transmission line section 18 and the width dimension of the second transmission line section 20 are different from each other. More specifically, the width dimension of the first transmission line section 18 is smaller than the width dimension of the second transmission line section 20. By adjusting the relationship between the width dimensions of the first transmission line section 18 and the second transmission line section 20, it is possible to adjust the frequency characteristics of the input impedance of the antenna device 1. For example, if the width dimensions of the first transmission line section 18 and the second transmission line section 20 are set so that the frequency characteristics of the input impedance of the antenna device 1 on the Smith chart have a kink, the change in the input impedance of the antenna device 1 with respect to frequency can be suppressed, and it becomes easy to adjust the characteristics to be able to handle a wide bandwidth using a matching circuit.

[0032] The folded connection portion 22 is a plate-shaped member that lies along the X-Z plane. The folded connection portion 22 connects the base end portion 18a of the first line portion 18 and the base end portion 20a of the second line portion 20. The base end portion 18a is the Y1 direction end of the first line portion 18. The base end portion 20a is the Y1 direction end of the second line portion 20. The folded element 10 has a folded shape by including the first line portion 18, the second line portion 20, and the folded connection portion 22.

[0033] Furthermore, the length dimension of the first track section 18 in the Y direction is longer than the length dimension of the second track section 20 in the Y direction. Therefore, the end 18b of the first track section 18 is located on the Y2 direction side than the end 20b of the second track section 20. End 18b is the Y2 direction side end of the first track section 18. End 20b is the Y2 direction side end of the second track section 20. Also, the plate surface 18c of the first track section 18 includes an opposing surface 18c1 and a protruding surface 18c2. The plate surface 18c is the surface of the first track section 18 facing the X1 direction. The opposing surface 18c1 is the part of the plate surface 18c that faces the second track section 20. The protruding surface 18c2 is the surface of the plate surface 18c that protrudes on the Y2 direction side than the end 20b of the second track section 20.

[0034] The grounding element 14 is connected to the end 20b of the second line section 20. The grounding element 14 is a strip-shaped member made of conductive metal. The longitudinal direction of the grounding element 14 is along the Z direction. The width direction of the grounding element 14 is along the Y direction. The grounding element 14 is integrally connected to the second line section 20. The strip surface of the grounding element 14 is along the Y-Z plane. Therefore, the grounding element 14 and the second line section 20 are located on the same Y-Z plane. The grounding element 14 has a first end 14a on the Z1 direction side and a second end 14b on the Z2 direction side. The first end 14a is connected to the end 20b of the second line section 20. The second end 14b is connected to the grounding conductor plate 4 of the circuit board 2. Therefore, the grounding element 14 grounds the end 20b of the second line section 20 to the grounding conductor plate 4. Furthermore, when we say that the second end 14b and the grounding conductor plate 4 are connected, we mean that the second end 14b and the grounding conductor plate 4 are in direct contact with each other or are electrically connected via other conductors. The same applies to the "connection" of conductors in the following explanation.

[0035] The power supply element 12 connects the end 18b of the first line section 18 to the power supply line 5. The power supply element 12 is a plate-shaped member made of conductive metal. The plate surface of the power supply element 12 is aligned with the Y-Z plane. Therefore, the plate surface of the power supply element 12 is parallel to the strip surface of the first line section 18, the strip surface of the second line section 20, and the strip surface of the grounding element 14. Note that the power supply element 12 and the second line section 20 (grounding element 14) may be located on the same Y-Z plane. The power supply element 12 has a first end 12a and a second end 12b. The first end 12a is the Z2 direction end of the power supply element 12 and is connected to the power supply line 5. The second end 12b is the end opposite to the first end 12a and is the Z1 direction end of the power supply element 12.

[0036] The power supply element 12 is positioned opposite the protruding surface 18c2 of the first line section 18. The power supply element 12 and the first line section 18 are positioned opposite each other such that the plate surface 12c and the protruding surface 18c2 are parallel to each other.

[0037] The power supply element 12 and the end 18b of the first line section 18 are connected via a connecting portion 24. The connecting portion 24 is a strip-shaped member made of conductive metal. The connecting portion 24 connects the end 18b of the first line section 18 and the first plate width direction end 12b1 of the second end 12b. The first plate width direction end 12b1 is the Y2 direction side end of the second end 12b of the power supply element 12.

[0038] The connecting portion 24 has a first plate-like portion 24a and a second plate-like portion 24b. The first plate-like portion 24a and the second plate-like portion 24b are connected so as to be bent relative to each other. The first plate-like portion 24a is connected to the first plate widthwise end 12b1. The second plate-like portion 24b is connected to the end 18b of the first track portion 18. Thus, the connecting portion 24 connects the end 18b of the first track portion 18 to the first plate widthwise end 12b1.

[0039] The power supply element 12 is erected on the circuit board 2 by being connected to the power supply line 5 on the circuit board 2. The grounding element 14 is also erected on the circuit board 2 by being connected to the grounding conductor plate 4. Therefore, the first line portion 18 and the second line portion 20 of the folded element 10 are supported by the power supply element 12 and the grounding element 14 so as to be parallel to and facing the board surface 2a.

[0040] Figure 3 is a plan view of the power supply element 12 in the first embodiment. Figure 3 shows the power supply element 12 as seen from the X1 direction. A projection 26 is provided at the first end 12a of the power supply element 12. The projection 26 is connected to the power supply line 5. A connecting portion 24 is connected to the first plate width direction end 12b1 of the second end 12b. In Figure 3, the connecting portion 24 is shown with a dashed line.

[0041] As shown in Figure 3, the contour 30 of the power supply element 12 when viewed from above has a tapered shape that widens from the first end 12a to the second end 12b. The contour 30 includes a side portion 30a, a first edge portion 30b, and a second edge portion 30c. The side portion 30a is the edge on the second end 12b side. The side portion 30a is aligned in the Y direction. Therefore, the side portion 30a is parallel to the extending direction of the first line portion 18 and the second line portion 20. The first edge portion 30b and the second edge portion 30c represent the contours of the edges on both sides of the power supply element 12 in the Y direction. The first edge portion 30b has a convex curve shape connecting the projection 26 and the first plate width direction end portion 12b1. The second edge portion 30c has a convex curve shape connecting the projection 26 and the second plate width direction end portion 12b2. The second plate widthwise end portion 12b2 is the Y1 direction end portion of the second end portion 12b of the power supply element 12. The first edge portion 30b and the second edge portion 30c are symmetrical with respect to a center line C parallel to the Z direction that passes through the projection 26.

[0042] According to the above configuration, since the contour 30 of the power supply side element 12 has a tapered shape with a widening width from the first end portion 12a side toward the second end portion 12b side, the change in the characteristic impedance of the power supply side element 12 from the power supply line 5 to the folded element 10 can be moderated. As a result, the return loss of the antenna device 1 with respect to signals in a relatively wide frequency band can be reduced. As a result, an antenna device 1 corresponding to a wide frequency band can be obtained.

[0043] Further, in the present embodiment, since the connection portion 24 that connects the end portion 18b of the first line portion and the first plate width direction end portion 12b1 of the second end portion 12b is provided so that the power supply side element 12 is disposed to face the protruding surface 18c2 of the first line portion 18, the first line portion 18 can be extended longer, and the adjustable range of the resonance frequency of the folded element 10 is expanded.

[0044] Further, in the present embodiment, the first line portion 18, the second line portion 20, and the ground element 14 are each made of brass, which is a conductive metal, and have a strip shape parallel to the plate surface of the power supply side element 12. Therefore, at least an intermediate workpiece including the portion of the power supply side element 12, the portion of the folded element 10 (the first line portion 18 and the second line portion 20), and the portion of the ground element 14 is cut out from a single conductive metal plate, and the intermediate workpiece is bent to easily obtain the antenna device 1 including the power supply side element 12, the folded element 10, and the ground element 14. The same applies to the following embodiments, and the antenna device 1 can be obtained by cutting out an intermediate workpiece from a single conductive metal plate and bending the intermediate workpiece.

[0045] In the antenna device 1, it is sufficient that at least one of a pair of combinations that are connected to each other among the ground element 14, the first line portion 18, the second line portion 20, and the ground element 14 is integrally formed by bending a single conductive metal plate. Also in this case, the antenna device 1 can be easily obtained.

[0046] [Regarding the Second Embodiment] FIG. 4 is a perspective view of the antenna device 1 according to the second embodiment. FIG. 5 is a view of the power supply side element 12 in FIG. 4 when viewed in plan. This embodiment is different from the first embodiment in that the antenna device 1 has a plate-like element 34.

[0047] The plate-like element 34 is a rectangular plate-like member made of a conductive metal. The plate surface of the plate-like element 34 is along the X - Y plane. Therefore, the plate surface of the plate-like element 34 is parallel to the substrate surface 2a of the circuit board 2. The long side of the plate-like element 34 is along the Y direction. The short side of the plate-like element 34 is along the X direction. The plate-like element 34 is connected to the side portion 30a of the second end portion 12b of the power supply side element 12. The plate-like element 34 extends from the side portion 30a of the power supply side element 12 along the X1 direction. In other words, the plate-like element 34 extends along a direction intersecting the extending direction (Y direction) of the first line portion 18. The plate-like element 34 is provided so as to be bent in an L shape starting from the side portion 30a of the power supply side element 12.

[0048] The tip 34a of the plate-like element 34 is an open end. The edge of the tip 34a is linear along the Y direction. The end portion 34b of the plate-like element 34 is connected to the side portion 30a. The end portion 34b is the end portion on the opposite side of the tip 34a and is the end portion on the X2 direction side. The position of the first side edge portion 34c of the plate-like element 34 in the Y direction coincides with the position of the edge portion on the Y1 direction side of the second plate width direction end portion 12b2. The first side edge portion 34c is the edge portion on the Y1 direction side of the plate-like element 34. The position of the second side edge portion 34d of the plate-like element 34 in the Y direction coincides with the position of the edge portion on the Y2 direction side of the first plate-like portion 24a of the connection portion 24. The second side edge portion 34d is the edge portion on the Y2 direction side of the plate-like element 34.

[0049] In this embodiment, a predetermined resonance frequency can be given to the combined path of the plate-like element 34 and the power supply side element 12. Therefore, by adjusting the length of the plate-like element 34, the resonance frequency of the combined path of the plate-like element 34 and the power supply side element 12 can be adjusted, and the return loss in a band different from the resonance frequency of the folded element 10 can be reduced. As a result, the frequency band that the antenna device 1 can support can be made wider.

[0050] Furthermore, the plate-shaped element 34 extends from the edge 30a of the power supply element 12 along the X1 direction. Therefore, the plate-shaped element 34 is positioned opposite the substrate surface 2a. Note that the plate-shaped element 34 only needs to extend along the intersecting direction that intersects the extending direction (Y direction) of the first line portion 18. Therefore, the plate-shaped element 34 may extend in the Z direction. In this case, the plate-shaped element 34 and the power supply element 12 are flush with each other. However, when the plate-shaped element 34 extends from the edge 30a of the power supply element 12 along the X1 direction, as in this embodiment, the posture (height) of the antenna device 1 with respect to the substrate surface 2a can be lowered compared to when the plate-shaped element 34 extends in the Z direction. Also, the plate-shaped element 34 may have a shape that bends in a direction that intersects the Y direction in the middle. Therefore, the plate-shaped element 34 may extend flush with the power supply element 12 up to a certain point and then bend in the middle.

[0051] [Regarding the Third Embodiment] Figure 6 is a perspective view of the antenna device 1 according to the third embodiment. This embodiment differs from the second embodiment in that the antenna device 1 has a branching element 38. Other aspects of the antenna device 1 of this embodiment are the same as those of the second embodiment.

[0052] The branching element 38 connects the base end 20a of the second line section 20 to the substrate surface 2a. The branching element 38 is a strip-shaped member made of conductive metal. The longitudinal direction of the branching element 38 is along the Z direction. The width direction of the grounding element 14 is along the Y direction. The branching element 38 is integrally connected to the base end 20a. The strip surface of the branching element 38 is along the Y-Z plane. Therefore, the branching element 38, the second line section 20, and the grounding element 14 are all located on the same Y-Z plane.

[0053] The branching element 38 has a third end 38a on the Z1 direction side and a fourth end 38b on the Z2 direction side. The third end 38a is connected to the base end 20a of the second line section 20. The fourth end 38b is connected to the main board 3 of the circuit board 2. The grounding conductor plate 4 of the circuit board 2 has a rectangular notch 4c at the corner where the edge on the Y1 direction side and the edge on the X2 direction side intersect. Therefore, the main board 3 has an exposed portion 3a at the notch 4c. The fourth end 38b is connected to the exposed portion 3a. Therefore, the fourth end 38b is not connected to the grounding conductor plate 4. However, the fourth end 38b and the grounding conductor plate 4 are capacitively coupled. In other words, an air layer or the substrate body 3 is interposed between the fourth end portion 38b and the edge portion 4c1 of the notch 4c, and capacitive coupling occurs between the fourth end portion 38b and the ground conductor plate 4. The distance between the fourth end portion 38b and the edge portion 4c1 of the notch 4c is set to a predetermined value. The predetermined value is the value that causes capacitive coupling between the fourth end portion 38b and the edge portion 4c1.

[0054] In this embodiment, the resonant frequency of the folded element 10 can be appropriately adjusted by adjusting the capacitance between the grounding conductor plate 4 and the branching element 38. This makes it possible to adjust the frequency characteristics of the antenna device 1 to cover a wider bandwidth. The capacitance generated between the grounding conductor plate 4 and the branching element 38 is adjusted by the distance between the fourth end portion 38b and the edge portion 4c1. For example, the narrower the distance between the fourth end portion 38b and the edge portion 4c1, the lower the resonant frequency of the folded element 10 can be shifted to a lower frequency band.

[0055] Furthermore, in this embodiment, the branching element 38 is erected on the circuit board 2 and connected to the second line section 20. Therefore, the folding element 10 is supported on the board surface 2a not only by the power supply element 12 and the grounding element 14, but also by the branching element 38. As a result, the folding element 10 is supported on the board surface 2a in a stable state.

[0056] [Regarding the fourth embodiment] Figure 7A is an enlarged view of the main part of the feed-side element 12 of the antenna device 1 according to the fourth embodiment. This embodiment differs from the third embodiment in that the antenna device 1 has a matching circuit 40. Other aspects of the antenna device 1 of this embodiment are the same as those of the third embodiment.

[0057] In Figure 7A, the matching circuit 40 is provided between the power supply line 5 and the projection 26 of the first end 12a. The matching circuit 40 includes a capacitance element 42, a first inductance element 44, a second inductance element 46, a first land portion 48, and a second land portion 50. The first land portion 48 and the second land portion 50 are conductive patterns made of copper or the like, provided on the substrate body 3. The first land portion 48 and the second land portion 50 are provided on the exposed surface of the substrate body 3 inside the slit 4a. The first land portion 48 and the second land portion 50 are arranged at intervals in the X direction on the X2 direction side of the connection portion 5b of the power supply line 5.

[0058] The projection 26 of the power supply element 12 is connected to the second land portion 50. The capacitance element 42 and the first inductance element 44 are provided in parallel between the connection portion 5b and the first land portion 48. The second inductance element 46 is provided between the first land portion 48 and the second land portion 50.

[0059] Figure 7B shows the equivalent circuit of the matching circuit 40. As shown in the figure, the capacitance element 42 and the first inductance element 44 are connected in parallel between the connection part 5b (power supply line 5) and the first land part 48, forming an LC parallel circuit 52. The second inductance element 46 is connected between the first land part 48 and the second land part 50 (power supply side element 12). Therefore, the second inductance element 46 is connected in series with the LC parallel circuit 52.

[0060] Here, it is assumed that the power supply line 5 is supplied with a signal having a frequency that falls within either the first frequency band or the second frequency band which is higher than the first frequency band. In this case, the resonant frequency of the matching circuit 40 is set to a frequency between the first frequency band and the second frequency band.

[0061] In this case, when the frequency of the supplied signal is lower than the resonant frequency, the matching circuit 40 becomes inductive (L-type). Similarly, when the frequency of the supplied signal is higher than the resonant frequency, the matching circuit 40 also becomes inductive (L-type). However, the first inductance value of the matching circuit 40 when the frequency of the supplied signal is lower than the resonant frequency and the second inductance value of the matching circuit 40 when the frequency of the supplied signal is higher than the resonant frequency are different from each other.

[0062] Therefore, by appropriately adjusting the first inductance value and the second inductance value, even when the input impedance characteristics when a signal in the first frequency band is supplied to the power supply element 12 are different from the input impedance characteristics when a signal in the second frequency band is supplied to the power supply element 12, both the signal in the first frequency band and the signal in the second frequency band can be appropriately matched.

[0063] [Regarding the Fifth Embodiment] Figure 8 is a perspective view of the antenna device 1 according to the fifth embodiment. This embodiment differs from the fourth embodiment in that the end portion 18b of the first line portion 18 is connected to the second plate width direction end portion 12b2 of the power supply side element 12, and the folded element 10 has an element body portion 10a and an element bent portion 10b.

[0064] Figure 9 is a plan view of the feed-side element 12 in the fifth embodiment. In Figure 9, the feed-side element 12 is shown as viewed from the X2 direction. As shown in Figure 9, the end 18b of the first line section 18 is connected to the second plate width direction end 12b2 of the feed-side element 12. Therefore, the antenna device 1 of this embodiment does not have a configuration equivalent to the connection section 24 (Figure 1) of the first embodiment. Note that in Figure 9, the end 18b of the first line section 18 is shown with a dashed line. Also, as shown in Figure 9, the contour 30 of the feed-side element 12 when viewed from above has a tapered shape that widens from the first end 12a to the second end 12b, and has the same configuration as the other embodiments. Therefore, as with the other embodiments, the return loss of the antenna device 1 for signals in a relatively wide frequency band can be reduced, and an antenna device 1 that can handle a wide frequency band can be obtained.

[0065] Figure 10 is a plan view of the antenna device 1 shown in Figure 8. Figure 10 shows the antenna device 1 as viewed from the Z1 direction. In other words, Figure 10 shows a front view of the substrate surface 2a. As shown in Figures 10 and 8, the folded element 10 has an element body portion 10a and an element bending portion 10b. The element body portion 10a and the element bending portion 10b are connected so as to bend along a plane parallel to the substrate surface 2a. Therefore, the folded element 10 of this embodiment has a shape that bends in the middle of its longitudinal direction. In a plan view, the element body portion 10a is arranged along the edge 2c of the circuit board 2. The element bending portion 10b is also arranged along the edge 2d of the circuit board 2. Edge 2d is the edge of the circuit board 2 that is in the X direction on the Y1 direction side.

[0066] The first line section 18 has a main body section 53 and a bent section 54. The main body section 53 is a straight portion of the first line section 18 that includes the end portion 18b. The main body section 53 is a portion included in the element main body section 10a. The main body section 53 is along side 2c. The bent section 54 is a straight portion of the first line section 18 that includes the base end portion 18a. The bent section 54 is a portion included in the element bent section 10b. The bent section 54 is along side 2d. The main body section 53 and the bent section 54 are connected so as to bend in the middle portion between the end portion 18b and the base end portion 18a. The main body section 53 and the bent section 54 are connected near the corner where side 2c and side 2d intersect.

[0067] The second transmission line 20 has a main body 55 and a bent portion 56. The main body 55 is a straight portion of the second transmission line 20 including the end 20b. The main body 55 is a portion included in the element main body 10a. The main body 55 is positioned opposite the main body 53 of the first transmission line 18. The bent portion 56 is a straight portion of the second transmission line 20 including the base end 20a. The bent portion 56 is a portion included in the element bent portion 10b. The bent portion 56 is positioned opposite the bent portion 54 of the first transmission line 18. The main body 55 and the bent portion 56 are connected so as to bend in the middle portion between the end 20b and the base end 20a. In this embodiment, since the folded element 10 has a shape that bends in the middle portion in the longitudinal direction, it becomes easy to position the antenna device 1 at the corner of the circuit board 2.

[0068] The branching element 38 is connected to the bent portion 56 of the second line section 20. The branching element 38 is connected to approximately the center of the bent portion 56 in the X direction. The notch 4c of the grounding conductor plate 4 is provided at a position corresponding to the position of the branching element 38. Furthermore, the width dimension (width dimension in the Z direction) of the main body portion 53 of the first line section 18, the width dimension of the main body portion 55 of the second line section 20, and the width dimension of the bent portion 56 of the second line section 20 are the same. The width dimension of the bent portion 54 of the first line section 18 is smaller than these width dimensions. In this embodiment, by adjusting the relationship between the width dimension of the bent portion 54, which is part of the first line section 18, and the width dimension of the second line section 20, it is possible to adjust the frequency characteristics of the input impedance of the antenna device 1. In other words, as in the first embodiment, by adjusting not only the relationship between the overall width dimension of the first line section 18 and the overall width dimension of the second line section 20, but also the relationship between the overall width dimension of a part of the first line section 18 and the overall width dimension of the second line section 20, the frequency characteristics of the input impedance of the antenna device 1 can be adjusted.

[0069] Figure 11 is an enlarged view of the main part of the plate-shaped element 34 in Figure 8. As shown in Figure 11, the end portion 34b of the plate-shaped element 34 is connected to the feed-side element 12 via a bent portion 60. The bent portion 60 is formed by bending. Before bending, the plate-shaped element 34 and the feed-side element 12 are flush. The bent portion 60 is formed by bending the plate-shaped element 34 so that it is perpendicular to the feed-side element 12. In other words, the antenna device 1 of this embodiment is obtained by cutting out an intermediate processed product, including the portion of the feed-side element 12, the portion of the plate-shaped element 34, the portion of the folded element 10, the portion of the branching element 38, and the portion of the grounding element 14, from a single conductive metal plate and bending the intermediate processed product. Therefore, the two parts that are connected to each other include a portion connected by a bent portion formed by bending.

[0070] A slit 62 is provided on the Y1 direction side of the bent portion 60. The slit 62 is provided so as to cut out a part of the second end 12b of the power supply element 12. The slit 62 is provided along the side surface 60a of the bent portion 60 at the second end 12b of the power supply element 12. The width dimension of the slit 62 in the Y direction is set to a value greater than or equal to the plate thickness of the power supply element 12, for example.

[0071] The slit 62 is formed before bending. Therefore, the slit 62 is provided along the side surface 34c1 of the plate-shaped element 34 before bending, on a part of the second end 12b. When bending is performed to form the plate-shaped element 34, the resistance force to bending that occurs between the first side edge 34c and the second end 12b is mitigated by the slit 62. As a result, deformation due to resistance force can be suppressed, and each part of the plate-shaped element 34, etc., can be obtained according to the design value. This suppresses a decrease in the performance of the antenna device 1.

[0072] Figure 12 is an enlarged view of the main part of the folded element 10 in Figure 8. As shown in Figure 12, the base end 18a of the first line section 18 is connected to the folded connection section 22 via a bent section 64. The bent section 64 is formed by bending. Before bending, the folded connection section 22 and the first line section 18 (folded section 54) are flush. The bent section 64 is formed by bending the folded connection section 22 and the first line section 18 so that they are perpendicular to each other.

[0073] A slit 66 is provided on the Z2 direction side of the bent portion 64. The slit 66 is provided so as to cut out a part of the end portion 22a of the folded connection portion 22. At the end portion 22a, the slit 66 is provided along the side surface 64a of the bent portion 64. The width dimension of the slit 66 in the Z direction is set to a value greater than or equal to the plate thickness of the power supply side element 12, for example.

[0074] The slit 66 is formed before bending. Therefore, the slit 66 is provided on a part of the end portion 22a along the side surface 54a of the bent portion 54 before bending. When bending is performed, the resistance force to bending that occurs between the bent portion 54 and the end portion 22a is mitigated by the slit 66. As a result, deformation due to resistance force can be suppressed, and the deterioration of the performance of the antenna device 1 is suppressed.

[0075] These slits 62 and 66 can be provided not only in the fifth embodiment but also in other embodiments.

[0076] [Regarding the Sixth Embodiment] Figure 13 is a perspective view of the antenna device 1 according to the sixth embodiment. This embodiment differs from the fifth embodiment in that the plate-shaped element 34 has a through hole 70. Other aspects of the antenna device 1 of this embodiment are the same as those of the fifth embodiment. As shown in Figure 13, the through hole 70 has a rectangular shape. Therefore, the plate-shaped element 34 has a frame shape along its periphery.

[0077] In this case, if the plate-shaped element 34 does not have a through-hole 70, as shown in Figure 10, when the substrate surface 2a is viewed from the front, the portion of the substrate surface 2a covered by the plate-shaped element 34 cannot be seen. In contrast, in this embodiment, the portion of the substrate surface 2a corresponding to the plate-shaped element 34 can be seen through the through-hole 70. Therefore, it is possible to prevent the plate-shaped element 34 from interfering with the inspection of mounted components on the substrate surface 2a when viewing the substrate surface 2a from the front.

[0078] Furthermore, since the signals propagating through the plate-shaped element 34 are mainly concentrated at the edges of the plate-shaped element 34, providing a through-hole 70 does not hinder the function of the antenna device 1. Therefore, although this embodiment illustrates the case where the through-hole 70 has a rectangular shape, the shape of the through-hole 70 is not limited to this.

[0079] [Regarding the Seventh Embodiment] Figure 14 is a perspective view of the antenna device 1 according to the seventh embodiment. This embodiment differs from the third embodiment in that the branching element 38 is provided in the second line section 20 at a position between the end 20b and the base end 20a. Other aspects of the antenna device 1 of this embodiment are the same as those of the third embodiment.

[0080] In this embodiment, the third end 38a of the branching element 38 is positioned at a predetermined distance from both the end 20b and the folded connection portion 22. Furthermore, the third end 38a of the branching element 38 is connected to the second line portion 20 at a position closer to the folded connection portion 22 than to the end 20b. Capacitive coupling occurs between the fourth end 38b and the grounding conductor plate 4. Therefore, in this embodiment as well, similar to the fourth embodiment, the resonant frequency of the folded element 10 can be appropriately adjusted by adjusting the capacitance between the grounding conductor plate 4 and the branching element 38. In addition, the folded element 10 is supported on the substrate surface 2a by the branching element 38, in addition to the power supply side element 12 and the grounding element 14. As a result, the folded element 10 is supported on the substrate surface 2a in a stable state.

[0081] [Regarding the Eighth Embodiment] Figure 15 is a perspective view of the antenna device 1 according to the eighth embodiment. This embodiment differs from the third embodiment in that the branching element 38 is provided in the first line section 18. Other aspects of the antenna device 1 of this embodiment are the same as those of the third embodiment.

[0082] In this embodiment, the third end 38a of the branching element 38 is positioned at a predetermined distance from both the end 18b and the folded connection portion 22. Furthermore, the third end 38a of the branching element 38 is connected to the first line portion 18 at a position closer to the folded connection portion 22 than to the end 18b. In this embodiment as well, similar to the third and seventh embodiments, the resonant frequency of the folded element 10 can be appropriately adjusted by adjusting the capacitance between the grounding conductor plate 4 and the branching element 38. In addition, the folded element 10 is supported on the substrate surface 2a by the branching element 38, in addition to the power supply side element 12 and the grounding element 14. As a result, the folded element 10 is supported on the substrate surface 2a in a stable state.

[0083] [Regarding Modifications] In the above embodiments, examples were given in which the first edge 30b and the second edge 30c included in the contour 30 of the power supply element 12 are convex curve shapes. The convex curve shape of the first edge 30b and the second edge 30c includes a part of a circle, a part of an ellipse, a part of a quadratic curve, a part of an exponential curve, etc., or a combination thereof. The first edge 30b and the second edge 30c of the contour 30 only need to have a tapered shape that widens from the first end 12a to the second end 12b. For example, the first edge 30b and the second edge 30c may be stepped in shape, widening in stages from the projection 26 to the plate width direction ends 12b1 and 12b2.

[0084] Furthermore, as shown in Figure 16A, the first edge 30b and the second edge 30c may have a shape that linearly connects the projection 26 and the plate width direction ends 12b1 and 12b2. In addition, as shown in Figure 16B, there may be a constriction 31 on the second end 12b side of the feeding element 12. However, the constriction 31 is provided within a range of 80% or more of the total length in the Z direction from the first end 12a of the feeding element 12. Even if the feeding element 12 has a constriction 31, the constriction 31 will not degrade the performance of the antenna device 1. Note that the constriction 31 may be provided on the plate width direction end 12b1 side. Figures 16A and 16B show modified examples of the feeding element 12 (Figure 3) of the first embodiment, but they are also applicable to other embodiments.

[0085] Figures 17A and 17B are plan views of a modified plate-shaped element 34 according to the sixth embodiment. In Figure 17A, the through-hole 70 of the plate-shaped element 34 is circular in shape. In Figure 17B, the through-hole 70 of the plate-shaped element 34 is elliptical in shape. Thus, the shape of the through-hole 70 is not particularly limited as long as it allows the mounted components on the substrate surface 2a to be visible.

[0086] Furthermore, in this specification, "parallel" does not have to be strictly parallel, but also includes being approximately parallel. Furthermore, in this specification, "strip-shaped" includes not only a shape that is long and narrow with a constant width, but also a shape that is long and narrow but has an inconsistent width. Furthermore, in this specification, "along a direction or edge" includes not only a shape that is approximately parallel to a direction or edge, but also a shape that is slightly inclined with respect to a direction or edge.

[0087] [Verification Test] Next, we will explain the verification test conducted on the effects of antenna device 1. As for the test method, multiple models of antenna device 1 were constructed, and the frequency characteristics of the return loss and the frequency characteristics of the total efficiency were determined for these models by computer simulation. The effects of antenna device 1 were verified by comparing the obtained simulation results with each other.

[0088] Models were constructed for the following eight embodiments and one comparative example. (Embodiment 1) In Embodiment 1, the antenna device 1 shown in the first embodiment is used. The folded element 10, the feed-side element 12, and the grounding element 14 are made of brass with a thickness of 0.3 mm.

[0089] The dimensions of each part of the antenna device 1 are as follows: - Length dimension L1 of the first line section 18: 90 mm (Figure 2) - Length dimension L2 of the second line section 20: 46 mm (Figure 2) - Width dimension W1 of the folded element 10 determined by the first line section 18 and the second line section 20: 3.8 mm (Figure 2) - Width dimension W2 of the folded element 10 determined by the first line section 18 and the power supply side element 12: 2.3 mm (Figure 2) - Width dimension W3 from the outer surface of the connection section 24 in the Y2 direction to the edge of the second plate width direction end 12b2 of the power supply side element 12: 40 mm (Figure 2) - Distance g1 between the first line section 18 and the second line section 20: 3.2 mm (Figure 2) - Distance g2 between the first line section 18 and the power supply side element 12: 1.7 mm (Figure 2) - Width dimension W4 of the first line section 18: 3.0 mm (Figure 1) - Width dimension W5 of the second line section 20: 5.0 mm (Figure 1) - Width dimension W6 of the grounding element 14: 5.0 mm (Figure 1) - Height H1 of the antenna device 1 (folded element 10 and the second end 12b of the feed-side element 12) relative to the substrate surface 2a: 20 mm (Figure 1)

[0090] (Example 2) Example 2 uses the antenna device 1 shown in the second embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 1, except for the dimensions described below. - Dimension L3 from the outer surface of the first line section 18 in the X2 direction to the edge of the tip 34a of the plate-shaped element 34: 17 mm (Figure 4) - Width dimension W7 of the plate-shaped element 34 in the Y direction: 40 mm (Figure 4)

[0091] (Example 3) Example 3 uses the antenna device 1 shown in the third embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 2, except for the dimensions described below. - Width dimension W8 in the X direction of the exposed part 3a: 9 mm (Figure 6) - Width dimension W9 in the Y direction of the exposed part 3a: 10 mm (Figure 6) - Distance g3 in the Y direction between the branching element 38 and the grounding conductor plate 4 in the exposed part 3a: 5.0 mm (Figure 6) - Distance g4 in the Y direction between the branching element 38 and the grounding conductor plate 4 in the exposed part 3a: 5.0 mm (Figure 6)

[0092] (Example 4) Example 4 uses the antenna device 1 shown in the fourth embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 3. The elements of the matching circuit 40 are set as follows: - Capacitance value of capacitance element 42: 2.2 pF - Inductance value of first inductance element 44: 8.0 nH - Inductance value of second inductance element 46: 2.2 nH

[0093] (Example 5) Example 5 uses the antenna device 1 shown in the fifth embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 3, except for the dimensions described below. Also, each element of the matching circuit 40 is the same as in Example 4. - Length L4 from the Y2-direction edge of the power supply element 12 to the Y1-direction outer surface of the bent portion 54: 64.8 mm (Figure 10) - Length L5 from the X2-direction outer surface of the first line portion 18 to the X1-direction outer surface of the folded connection portion 22: 39.5 mm (Figure 10) - Length L6 from the bent portion 56 to the end 20b of the main body portion 55: 29 mm (Figure 10) - Length L7 of the plate-shaped element 34 in the X direction: 15 mm (Figure 10) - Width W10 of the plate-shaped element 34 in the Y direction: 32.5 mm (Figure 10) - Y-direction spacing g5 between the branch element 38 and the grounding conductor plate 4 in the exposed portion 3a: 5.0 mm (Figure 8) - X-direction spacing g6 between the branch element 38 and the grounding conductor plate 4 in the exposed portion 3a: 5.0 mm (Figure 8)

[0094] (Example 6) Example 6 uses the antenna device 1 shown in the sixth embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 5, except for the dimensions described below. Also, each element of the matching circuit 40 is the same as in Example 4. - Dimension of the through hole 70 in the Y direction: 27.5 mm - Dimension of the through hole 70 in the X direction: 12.0 mm The through hole 70 is provided approximately in the center of the plate-shaped element 34.

[0095] (Example 7) Example 7 uses the antenna device 1 shown in the seventh embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 4, except for the dimensions described below. - Dimension L8 from the outer surface of the folded connection part 22 on the Y1 direction side to the branching element 38: 10 mm (Figure 14)

[0096] (Example 8) Example 8 uses the antenna device 1 shown in the eighth embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 4, except for the dimensions described below. - Dimension L9 from the outer surface of the folded connection part 22 on the Y1 direction side to the branching element 38: 10 mm (Figure 15)

[0097] (Comparative Example) Figure 18 is a perspective view of the antenna device 100 according to the comparative example. The comparative example uses a configuration in which the feed-side element 12 of Example 1 is made into a strip-shaped portion 102 extending in the Z direction. The folded element 101 and grounding element 104 of the antenna device 100 have the same dimensions as the folded element 10 and grounding element 14 of Example 1. Therefore, the length dimension L20 of the folded element 101 (first line portion) is 90 mm. Also, the height H2 is 20 mm.

[0098] (Comparison between Example 1 and Comparative Example 1) Figure 19 is an example of a graph showing the frequency characteristics of the return loss for Example 1 and Comparative Example. The horizontal axis of Figure 19 represents frequency. The vertical axis of Figure 19 shows the S-parameter S11 as the return loss when the first end 12a of the power supply element 12 is used as the input terminal.

[0099] Furthermore, in Figure 19, the areas with vertical hatching represent examples of frequency bands expected to be used by mobile communication systems (LTE and SUB6), indicating a range where the return loss is -5 dB or greater. If the return loss of antenna device 1 is -5 dB or less, then that frequency band can be determined to be a usable frequency band for antenna device 1. In other words, within the areas with vertical hatching, the areas where the graph passes below can be determined to be a usable frequency band for antenna device 1. The areas with vertical hatching in the graphs showing the frequency characteristics of return loss shown in Figure 19 and later are the same as the hatched areas in Figure 19.

[0100] In Figure 19, the comparative example shows a return loss of -5 dB or less across multiple frequency bands, but exhibits relatively narrow bandwidth characteristics. In contrast, in Example 1, the return loss is continuously -5 dB or less across frequency bands of 2.2 GHz and above. From these results, it can be seen that Example 1, which has a tapered feed-side element 12, is capable of handling a wider frequency band than the comparative example.

[0101] (Comparison between Example 2 and the Comparative Example) Figure 20 is an example of a graph showing the frequency characteristics of the return loss for Example 2 and the Comparative Example. The horizontal axis of Figure 20 represents frequency. The vertical axis of Figure 20 represents S11. Figure 20 also shows the graph for Example 1.

[0102] In Figure 20, in Example 2, the return loss in the frequency band above 1.6 GHz is continuously -5 dB or less. From this result, it can be seen that Example 2 is capable of handling a wider frequency band than the comparative example.

[0103] Furthermore, comparing Example 1 and Example 2, in Example 1, the return loss can exceed -5 dB in the frequency band from 1.6 GHz to 2.2 GHz. In contrast, in Example 2, the return loss remains continuously below -5 dB in the frequency band from 1.6 GHz to 2.2 GHz. Therefore, Example 2 is capable of handling a wider bandwidth compared to Example 1.

[0104] (Comparison of Example 3 with the Comparative Example) Figure 21 is an example of a graph showing the frequency characteristics of the return loss for Example 3 and the Comparative Example. The horizontal axis of Figure 21 represents frequency. The vertical axis of Figure 21 represents S11. Figure 21 also shows the graph for Example 2. In Figure 21, as with Example 2, the return loss in the frequency band of 1.6 GHz and above is continuously -5 dB or less.

[0105] Furthermore, in the graph of Example 2, the peak appearing at approximately 1.12 GHz corresponds to the resonant frequency of the folded element 10. Similarly, in the graph of Example 3, the peak appearing at approximately 0.9 GHz corresponds to the resonant frequency of the folded element 10. Thus, in Example 3, the resonant frequency of the folded element 10 is shifted to a lower frequency. From this result, it can be seen that the resonant frequency of the folded element 10 is adjusted by the branching element 38.

[0106] Furthermore, the height H1 of Example 2 and the height H1 of Example 3 are the same at 20 mm. Therefore, when comparing the height of Example 2 and the height of Example 3 based on the resonant frequency (wavelength), the relative lower height is achieved in Example 3, where the resonant frequency of the folded element 10 is lower.

[0107] (Regarding the matching circuit 40 of Example 4) Figure 22 is a Smith chart showing the input impedance of the antenna device 1 according to Example 3. In Figure 22, the dashed line shows the impedance between 0.7 GHz and 0.96 GHz. The solid line shows the impedance between 1.7 GHz and 5.0 GHz. Looking at Figure 22, the impedance in the high-frequency band from 1.7 GHz to 5.0 GHz is centered at Z ０ It is located near the ) point. Furthermore, the impedance in the low-frequency band from 0.7 GHz to 0.96 GHz is located in the capacitive region, which is the lower half of the Smith chart. From these results, it can be seen that by setting the characteristics of the matching circuit 40 to be inductive in the low-frequency band and through or less inductive in the high-frequency band, the impedance of the antenna device 1 as seen from the feed line 5 can be appropriately matched in both the low-frequency and high-frequency bands.

[0108] Figure 23 is an example of a graph showing the frequency characteristics of the return loss of an antenna device 1 in which an inductance element is provided before the feed-side element 12. The horizontal axis of Figure 23 represents frequency. The vertical axis of Figure 23 represents S11. Figure 23 shows the low-frequency band. The inductance values ​​of the inductance elements were set to 0.1 nH, 5 nH, 6 nH, 16 nH, and 20 nH, and the frequency characteristics of the return loss were determined when inductance elements of each inductance value were provided.

[0109] Figure 23 shows that if the minimum value near 0.81 GHz decreases, broadbanding in the low-frequency range can be achieved. Furthermore, if the inductance value of the inductance element is set to 6 nH or higher, the minimum value near 0.81 GHz will be -5 dB or lower. From this result, it can be seen that setting the inductance value to 6 nH or higher is sufficient for the low-frequency range.

[0110] Figure 24 is an example of a graph showing the frequency characteristics of the return loss of an antenna device 1 in which an inductance element is provided before the feed-side element 12. The horizontal axis of Figure 24 represents frequency. The vertical axis of Figure 24 represents S11. Figure 24 shows the high-frequency band. The inductance values ​​of the inductance elements were set to 0.1 nH, 2 nH, and 3 nH, and the frequency characteristics of the return loss were determined when inductance elements of each inductance value were provided.

[0111] As shown in Figure 24, setting the inductance value to 2 nH or less results in a level of -5 dB or less across almost the entire high-frequency band. From this result, it can be seen that setting the inductance value to 2 nH or less is sufficient for the high-frequency band.

[0112] Based on these results, the capacitance value of the capacitance element 42, the inductance value of the first inductance element 44, and the inductance value of the second inductance element 46 of the matching circuit 40 in Example 4 were set as described above. With the above settings, the resonant frequency of the matching circuit 40 is 1.2 GHz. The inductance value of the matching circuit 40 in the low-frequency band lower than the resonant frequency is 16.6 nH. The inductance value of the matching circuit 40 in the high-frequency band higher than the resonant frequency is 1.4 nH. Thus, according to Example 4, the inductance value of the matching circuit 40 in the low-frequency band and the inductance value of the matching circuit 40 in the high-frequency band are appropriately set, and both signals are appropriately matched regardless of whether they are supplied in the low-frequency band or the high-frequency band.

[0113] (Comparison of Example 4 with the Comparative Example) Figure 25 is an example of a graph showing the frequency characteristics of the return loss for Example 4 and the Comparative Example. The horizontal axis of Figure 25 represents frequency. The vertical axis of Figure 25 represents S11. Figure 25 also shows the graph for Example 3. In Figure 25, in Example 4, the return loss in the high-frequency band is continuously -5 dB or less. In addition, in Example 4, the frequency band in which the return loss is -5 dB or less is expanded compared to Example 3.

[0114] Furthermore, the resonant frequency of the folded element 10 in Example 4 is approximately 0.8 GHz, which represents an even lower profile compared to Example 3.

[0115] Figure 26 is an example of a graph showing the frequency characteristics of the total efficiency of Example 4. The horizontal axis of Figure 26 represents frequency. The vertical axis of Figure 26 represents total efficiency. Total efficiency is the ratio of radiated power to input power of antenna device 1. As shown in Figure 26, it can be seen that good total efficiency can be obtained in both the low-frequency and high-frequency bands according to Example 4.

[0116] (Comparison of Example 5 with the Comparative Example) Figure 27 is an example of a graph showing the frequency characteristics of the return loss for Example 5 and the Comparative Example. The horizontal axis of Figure 27 represents frequency. The vertical axis of Figure 27 represents S11. Figure 27 also shows the graph for Example 4. In Figure 27, Example 5, like Example 4, has a return loss of -5 dB or less continuously in the high-frequency band. Furthermore, in Example 5, the return loss is reduced even further in the low-frequency band compared to Example 4.

[0117] Figure 28 is an example of a graph showing the frequency characteristics of the total efficiency of Example 5. The horizontal axis of Figure 28 represents frequency. The vertical axis of Figure 28 represents total efficiency. As shown in Figure 28, it can be seen that, similar to Example 4, good total efficiency is obtained in both the low-frequency and high-frequency bands in Example 5.

[0118] (Regarding the position of the branching element) Figure 29 is an example of a graph showing the frequency characteristics of the return loss for each of the following examples: Example 4, Example 7, and Example 8. The horizontal axis of Figure 29 represents frequency. The vertical axis of Figure 29 represents S11.

[0119] Examples 4, 7, and 8 have similar configurations except for the part to which the branching element 38 is connected. In Example 4, the branching element 38 is connected to the base end 20a of the second line section 20. In Example 7, the branching element 38 is connected to a position offset by 10 mm toward the end 20b side from the base end 20a of the second line section 20. In Example 8, the branching element 38 is connected to the first line section 18. In Example 8, the branching element 38 is connected to a position offset by 10 mm toward the end 18b side from the base end 18a of the first line section 18.

[0120] As can be seen in Figure 29, in all of Examples 4, 7, and 8, the return loss in the low-frequency band and the return loss in the high-frequency band are generally -5 dB or less. From this result, it can be seen that the position where the branching element 38 is connected has little effect on the frequency characteristics of the antenna device 1, and that the frequency characteristics of the antenna device 1 can be appropriately adjusted by providing the branching element 38 on the folded element 10.

[0121] [Other] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not in the sense described above, and is intended to include the meaning and scope of equivalences of the claims, and all modifications within that scope.

[0122] 1 Antenna device 2 Circuit board 2a Board surface 2c Side 2d Side 3 Board body 3a Exposed part 4 Grounding conductor plate 4a Slit 4b Side 4c Notch 4c1 Edge 5 Feed line 5a Feed point 5b Connection part 6 Via 10 Folded element 10a Element body part 10b Element bent part 12 Feed side element 12a First end 12b Second end 12b1 First end in board width direction 12b2 Second end in board width direction 12c Board surface 14 Grounding element 14a First end 14b Second end 18 First line section 18a Base end 18b End 18c Board surface 18c1 Opposing surface 18c2 Protruding surface 20 Second line section 20a Base end 20b End portion 22 Folded connection portion 22a End portion 24 Connection portion 24a First plate-shaped portion 24b Second plate-shaped portion 26 Projection 30 Contour 30a Edge portion 30b First edge portion 30c Second edge portion 34 Plate-shaped element 34a Tip 34b End portion 34c First side edge portion 34c1 Side surface 34d Second side edge portion 38 Branching element 38a Third end portion 38b Fourth end portion 40 Matching circuit 42 Capacitance element 44 First inductance element 46 Second inductance element 48 First land portion 50 Second land portion 52 LC parallel circuit 53 Main body portion 54 Bent portion 54a Side surface 55 Main body portion 56 Bent portion 60 Bent portion 60a Side surface 62 Slit 64 Bent portion 64a Side view 66 Slit 70 Through hole 100 Antenna device 101 Folded element 102 Strip portion 104 Grounding element C Center line S Signal source

Claims

1. An antenna device comprising: a folded element including a first line section and a second line section, the base ends of which are connected and which are arranged opposite to each other at a predetermined distance apart; a plate-shaped feeding-side element connecting the end of the first line section opposite to the base end to a feeding line; and a grounding element connecting the end of the second line section opposite to the base end to a grounding conductor, wherein the feeding-side element has a first end connected to the feeding line and a second end opposite to the first end, the end of the first line section is connected to the plate width end of the second end, and the outline of the feeding-side element when viewed from above has a tapered shape that widens from the first end side to the second end side.

2. The antenna device according to claim 1, further comprising a plate-shaped element having a side portion along the extending direction of the first line portion at the second end side, and extending along a crossing direction intersecting the extending direction from the side portion of the power supply side element, with its tip being an open end.

3. The antenna device according to claim 2, wherein the power supply element and the grounding element are erected on a substrate having the power supply line, the first line portion and the second line portion are supported by the power supply element and the grounding element so as to be parallel to and facing the substrate surface of the substrate, and the intersecting direction is the direction in which the plate-shaped element is positioned facing the substrate surface.

4. The antenna device according to claim 3, wherein the plate-shaped element has a through hole that penetrates in the thickness direction of the plate.

5. The antenna device according to claim 1, wherein the plate surface of the first line section facing the second line section includes a facing surface facing the second line section and a protruding surface that protrudes beyond the end of the second line section, and further comprises a connecting portion that connects the end of the first line section and the plate width direction end of the second end, such that the power supply side element is positioned facing the protruding surface.

6. The antenna device according to claim 1 or 2, wherein the power supply element and the grounding element are erected on a substrate having the power supply line, the first line portion and the second line portion are supported by the power supply element and the grounding element so as to be parallel to and opposite to the substrate surface of the substrate, the grounding conductor is provided on the substrate and further comprises a branching element connecting either the first line portion or the second line portion to the substrate surface, the branching element having a third end connected to either the first line portion or the second line portion and a fourth end capacitively coupled with the grounding conductor provided on the substrate.

7. The antenna device according to claim 6, wherein the folded element has a folded connection portion that connects the base ends of the elements, and the third end is connected to either a position in the first line portion that is closer to the folded connection portion than the end of the first line portion, or a position in the second line portion that is closer to the folded connection portion than the end of the second line portion.

8. The folded element has an element body portion and an element bending portion, which are arranged in order along the direction from the end of the first line portion and the end of the second line portion toward both base ends, the element body portion and the element bending portion are connected so as to bend along a plane parallel to the substrate surface, and the third end is connected to either the portion of the first line portion included in the element bending portion or the portion of the second line portion included in the element bending portion, the antenna device according to claim 6.

9. The antenna device according to any one of claims 1 to 8, wherein a signal having a frequency included in either a first frequency band or a second frequency band higher than the first frequency band is supplied from the feed line, and the device further comprises a matching circuit provided between the feed line and the first end, the resonant frequency of the matching circuit being a frequency between the first frequency band and the second frequency band, and the inductance value of the matching circuit when the frequency of the signal is higher than the resonant frequency and the inductance value of the matching circuit when the frequency of the signal is lower than the resonant frequency are different from each other.

10. The antenna device according to any one of claims 1 to 9, wherein the first line section, the second line section, and the grounding element each have a strip shape made of a conductive metal.

11. The antenna device according to claim 10, wherein the width dimension of the first line section is smaller than the width dimension of the second line section.

12. The antenna device according to any one of claims 1 to 11, wherein at least one of the pairs of combinations of the grounding element, the first line section, the second line section, and the grounding element that are connected to each other is integrally formed by bending a single conductive metal plate.

Images