Antenna device and wireless communication device

Abstract

An antenna device according to an embodiment of the present invention includes: a circuit board having a first surface; and an antenna element provided on the circuit board. The antenna element includes: a columnar part which extends from a power supply part provided on the first surface along a first direction intersecting with the circuit board; a first element part which is connected to the columnar part and extends along a second direction parallel to the first surface; and a second element part which is connected to the columnar part and is located closer to the circuit board than the first element part. The second element part includes: a first line portion which extends from the columnar part along a direction parallel to the first surface and is disposed to face a ground conductor plate provided on the first surface; and a connection portion which connects the leading end of the first line portion and the ground conductor plate.

Description

Antenna device and wireless communication device

[0001] The present disclosure relates to an antenna device and a wireless communication device. This application claims priority based on Japanese Patent Application No. 2025-009850 filed on January 23, 2025, 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 a pair of strip-shaped element parts arranged to face each other through a folded part (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2007-28213

[0004] The antenna device according to an embodiment includes a circuit board having a first surface, and an antenna element provided on the circuit board. The antenna element includes a columnar part extending along a first direction intersecting the circuit board from a power feeding part provided on the first surface, a first element part connected to the columnar part and extending along a second direction parallel to the first surface, and a second element part connected to the columnar part and located closer to the circuit board side than the first element part. The second element part includes a first line part extending from the columnar part along a direction parallel to the first surface and disposed opposite to a ground conductor plate provided on the first surface, a tip of the first line part, and a connection part connecting the tip and the ground conductor plate.

[0005] Figure 1 is a perspective view showing an example of an antenna device according to the first embodiment. Figure 2 is a diagram showing the main part of the circuit board. Figure 3 is a cross-sectional view taken along the line III-III in Figure 2. Figure 4 is a perspective view showing an example of an antenna device according to the second embodiment. Figure 5 is a perspective view showing an antenna device according to the third embodiment. Figure 6 is a perspective view showing an antenna device according to a modified example of the third embodiment. Figure 7 is a schematic diagram showing an antenna device according to another embodiment. Figure 8 is a schematic diagram showing an antenna device according to another embodiment. Figure 9 is a diagram for explaining the dimensions of the antenna element. Figure 10 is a perspective view of an antenna device according to a comparative example. Figure 11 is an example of a graph showing the frequency characteristics of the return loss of Examples 1 to 4 and the comparative example. Figure 12 is an example of a graph showing the frequency characteristics of the total efficiency of Examples 1 to 4 and the comparative example. Figure 13 is a Smith chart showing the input impedance of Example 1 and the comparative example. Figure 14 is a graph showing the frequency characteristics of the return loss of the antenna device when the interval g1 is changed in Example 3. Figure 15 is a diagram showing an example of the current distribution in the Y-Z plane in Example 3.

[0006] [Problems this disclosure aims to solve] In the folded antenna described above, miniaturization can be achieved while ensuring the length of the element lines by folding the antenna. The pair of element sections of the folded antenna are connected by the folded portion. Therefore, there is a risk that the pair of element sections may come into contact with each other due to vibrations during movement. To address this, it is conceivable to widen the distance between the pair of element sections. In this case, contact between the pair of element sections can be suppressed. However, this may lead to an increase in the size of the antenna.

[0007] Thus, in the case of multiband antennas for mobile stations, it is necessary to ensure a certain length of transmission line, which may be a disadvantage from the perspective of miniaturizing the antenna.

[0008] Therefore, this disclosure aims to provide a multiband and miniaturized antenna device.

[0009] [Effects of this disclosure] According to this disclosure, it is possible to obtain a multiband and miniaturized antenna device.

[0010] [Description of Embodiments in this Disclosure] First, the contents of the embodiments will be listed and described. [Summary of Embodiments]

[0011] (1) An embodiment of the antenna device comprises a circuit board having a first surface and an antenna element provided on the circuit board. The antenna element comprises a columnar portion extending from a power supply portion provided on the first surface along a first direction intersecting the circuit board, a first element portion connected to the columnar portion and extending along a second direction parallel to the first surface, and a second element portion connected to the columnar portion and located closer to the circuit board than the first element portion. The second element portion comprises a first line portion extending from the columnar portion along a direction parallel to the first surface and positioned opposite a grounding conductor plate provided on the first surface, and a connecting portion connecting the tip of the first line portion and the grounding conductor plate. With the above configuration, by providing the second element portion, the frequency band that can be transmitted and received by the antenna device can be shifted to the lower frequency side compared to the case where the second element portion is not provided. As a result, the line length (electrical length) of the antenna element when normalized by the wavelength of the transmittable and receiveable signals is shortened, and a multiband and miniaturized antenna device can be obtained.

[0012] (2) In the antenna device described in (1) above, the first line section may extend along the second direction and be positioned opposite to the first element section. In this case, the first element section and the first line section are arranged side by side along the first direction. Therefore, the size of the antenna element can be made smaller compared to the case in which the first element section and the first line section are not arranged side by side along the first direction.

[0013] (3) In the antenna device of (1) or (2) above, the distance between the first line section and the first element section may be greater than the distance between the first line section and the grounding conductor plate. In this case, the grounded first line section and the first element section can be separated, and deterioration of the characteristics of the antenna element is suppressed.

[0014] (4) In any one of the antenna devices described in (1) to (3) above, the first element portion may have a second line portion extending from the columnar portion along the second direction, a third line portion extending from the tip of the second line portion in a third direction opposite to the first direction, and a fourth line portion extending from the tip of the third line portion in a fourth direction opposite to the second direction. In this case, the first element portion has a bent shape. This makes it possible to secure a large length for the first element portion without significantly extending the length of the first element portion in the second direction.

[0015] (5) In the antenna device described in (4) above, if a third element is further provided that is connected to the columnar part and extends along the second direction, the third element may be located between the second line section and the fourth line section. In this case, by providing the third element, the frequency band that the antenna device can transmit and receive can be shifted to an even lower frequency. In addition, by providing the third element in the space enclosed by the first element, the impact of providing the third element on the size of the antenna device is suppressed. Furthermore, by making the length of the line including the third element different from the length of the line including the first element, the antenna device can be made multiband.

[0016] (6) In any one of the antenna devices described in (1) to (4) above, if a third element portion is further provided that is connected to the columnar portion and extends along the second direction, the third element portion may be located between the first line portion and the first element portion. In this case as well, it is possible to make the antenna device multiband while suppressing the impact on the size of the antenna device.

[0017] (7) In any one of the antenna devices described in (1) to (6) above, the tip of the first transmission line may be located closer to the columnar portion than the tip of the first element portion. In this case, the length of the first transmission line can be reduced, and the influence of the second element portion on the size of the antenna element can be reduced.

[0018] (8) Any one of the antenna devices described in (1) to (7) above may further include an additional element connected to the columnar portion. In this case as well, the additional element can enable the antenna device to be multiband.

[0019] (9) In any one of the antenna devices described in (1) to (8) above, the antenna element may be a component obtained by punching out a conductive metal plate. In this case, the antenna element can be easily obtained.

[0020] (10) A wireless communication device, which is an embodiment from another perspective, comprises one of the antenna devices described in (1) to (9) above, and a communication module that transmits and receives using the antenna device.

[0021] [Details of Embodiments] Preferred embodiments will be described below with reference to the drawings. At least some of the embodiments described below may be combined as desired. [About the First Embodiment] Figure 1 is a perspective view showing an example of an antenna device according to the first embodiment. This antenna device 1 is used, for example, in a mobile station of a mobile communication system. The antenna device 1 is installed on electronic equipment having wireless communication functions. 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.

[0022] In the following explanation, the three mutually orthogonal directions in each diagram will be referred to as the X, Y, and Z directions. Furthermore, one direction within the X direction will be designated as the X1 direction, and the opposite direction will be designated as the X2 direction. One direction within the Y direction will be designated as the Y1 direction, and the opposite direction will be designated as the Y2 direction. One direction within the Z direction will be designated as the Z1 direction, and the opposite direction will be designated as the Z2 direction.

[0023] The antenna device 1 comprises a circuit board 2 and an antenna element 10. The circuit board 2 is a substrate included in electronic equipment. Various electronic components for realizing wireless communication functions are mounted on the circuit board 2. The circuit board 2 is a rectangular rigid substrate arranged along the X-Y plane. In addition, each side of the circuit board 2 is aligned along the X direction or the Y direction. The circuit board 2 has a first surface 2a and a second surface 2b. The first surface 2a is the surface of the circuit board 2 facing the Z1 direction. The second surface 2b is the surface of the circuit board 2 facing the Z2 direction.

[0024] Figure 2 shows the main components of the circuit board 2. Figure 2 shows the circuit board 2 with the antenna element 10 removed. As shown in Figures 2 and 1, the circuit board 2 has a substrate body 3, a grounding conductor plate 4, and a power supply line 5. The substrate body 3 is a rectangular plate-shaped member made of dielectric material. The grounding conductor plate 4 is a conductor pattern made of copper or the like, provided on the first surface 2a side of the circuit board 2. The grounding conductor plate 4 is provided so as to cover at least the portion of the surface of the substrate body 3 facing the Z1 direction that surrounds the antenna element 10 and the power supply line 5. The grounding conductor plate 4 is grounded.

[0025] The power supply line 5 is a conductor pattern made of copper or the like, provided on the first 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 slit 4a has a wide portion 4a1 and a narrow portion 4a2. The wide portion 4a1 has a rectangular shape along the side 4b. The narrow portion 4a2 has an elongated shape extending from the wide portion 4a1 along the X1 direction. The width of the narrow portion 4a2 in the Y direction is narrower than the width of the wide portion 4a1 in the Y direction.

[0026] The power supply line 5 is provided on the exposed surface of the substrate body 3 inside the slit 4a. The power supply line 5 has a land portion 5a and a line portion 5b. The land portion 5a is provided within the wide portion 4a1. The land portion 5a has a rectangular shape corresponding to the shape of the wide portion 4a1. An antenna element 10 is provided on the land portion 5a. A part of the antenna element 10 is fixed to the land portion 5a by soldering, brazing, etc. This electrically connects the land portion 5a and the antenna element 10. A first through hole 6 is also provided in the land portion 5a. Furthermore, a second through hole 7 is provided in the circuit board 2 at a predetermined interval on the Y1 direction side of the first through hole 6. The first through hole 6 and the second through hole 7 penetrate between the first surface 2a and the second surface 2b. The first through hole 6 and the second through hole 7 are used to fix the antenna element 10 to the circuit board 2. Parts of the antenna element 10 are inserted into the first through-hole 6 and the second through-hole 7, respectively.

[0027] The track section 5b is provided in the narrow section 4a2. Therefore, the track section 5b extends from the land section 5a along the X1 direction. A small gap is provided between the edge of the track section 5b in the width direction (Y direction) and the edge of the grounding conductor plate 4 in the narrow section 4a2. The track section 5b, together with the portions of the grounding conductor plates 4 on both sides of the track section 5b, constitutes a coplanar track.

[0028] A signal source S of a communication module for wireless communication is connected to the end 5b1 of the line section 5b. Also, as described above, the antenna element 10 is electrically connected to the land section 5a. Therefore, the land section 5a is the power supply section (feed point) for the antenna element 10. The antenna element 10 is powered from the signal source S via the power supply line 5. In the following description, we will explain the case when the antenna device 1 transmits radio waves, but when receiving radio waves, it operates in the same way as when transmitting.

[0029] The antenna element 10 is obtained, for example, by punching out a conductive metal sheet such as copper, brass, or steel. Therefore, the antenna element 10 has an integrated shape that includes all the parts it has.

[0030] As shown in Figure 1, the antenna element 10 comprises a columnar portion 12, a first element portion 14, and a second element portion 16. The columnar portion 12 is a strip-shaped member and extends linearly from the land portion 5a along a first direction (Z1 direction) intersecting the circuit board 2. The first element portion 14 is connected to the first end portion 12a of the columnar portion 12. The first end portion 12a is the tip side (Z1 direction side) of the columnar portion 12. The first element portion 14 protrudes from the first side portion 12b of the columnar portion 12. The first side portion 12b is the side of the columnar portion 12 on the Y1 direction side. The first element portion 14 extends along the Y1 direction, which is parallel to the first surface 2a.

[0031] The second element portion 16 is connected to the columnar portion 12. The second element portion 16 protrudes from the first side portion 12b of the columnar portion 12. The position where the second element portion 16 is connected to the columnar portion 12 is closer to the second end portion 12c than to the first end portion 12a in the longitudinal direction of the columnar portion 12. Therefore, the second element portion 16 is located closer to the circuit board 2 than the first element portion 14. The second end portion 12c is the end portion of the columnar portion 12 on the Z2 direction side (circuit board 2 side).

[0032] The second element section 16 comprises a first line section 18 and a connecting section 20. The first line section 18 is the portion of the second element section 16 that extends linearly from the columnar section 12. In other words, the first line section 18 extends along a direction parallel to the first surface 2a. The first line section 18 extends parallel to the second direction (Y1 direction) in which the first element section 14 extends. The first line section 18 has a strip shape with its longitudinal direction parallel to the Y direction. The first line section 18 is positioned opposite the grounding conductor plate 4 with a small gap between them. The connecting section 20 is a strip-shaped member of the second element section 16 that extends from the tip 18a of the first line section 18 toward the Z2 direction. The connecting section 20 connects the tip 18a of the first line section 18 to the grounding conductor plate 4.

[0033] Figure 3 is a cross-sectional view taken along the line III-III in Figure 2. Figure 3 shows cross-sections of the columnar portion 12 and the connecting portion 20. As shown in Figure 3, the second end portion 12c of the columnar portion 12 has an end face 13a and a projection 13b. The end face 13a is the surface facing the Z2 direction at the second end portion 12c. The projection 13b is the portion that protrudes from the end face 13a in the Z2 direction. The cross-section of the projection 13b is rectangular. The second end portion 12c and the projection 13b have the same thickness in the X direction.

[0034] The projection 13b is inserted into the first through hole 6. The end face 13a abuts against the land portion 5a provided on the first surface 2a. Thus, the projection 13b positions the columnar portion 12 on the circuit board 2 in the X and Y directions. The end face 13a also positions the columnar portion 12 on the circuit board 2 in the Z direction.

[0035] The side surface of the second end portion 12c and the land portion 5a are fixed by the solder portion 22a. Also, the tip 13b1 of the projection 13b and the land portion 15 are fixed by the solder portion 22b. The land portion 15 is a conductive pattern made of copper or the like, provided on the surface of the substrate body 3 facing the Z2 direction. The land portion 15 is provided in a shape corresponding to the land portion 5a. Therefore, the land portion 15 has a rectangular shape. A conductive layer made of copper or the like is provided on the inner circumferential surface of the first through hole 6. This conductive layer connects the land portion 5a and the land portion 15. The solder portions 22a and 22b, made of solder alloy, are formed by soldering. The solder portions 22a and 22b fix the second end portion 12c, including the projection 13b, and the circuit board 2. Furthermore, the soldered portions 22a and 22b electrically connect the columnar portion 12 to the land portion 5a and the land portion 15. Note that the land portion 15 is not electrically connected to anything other than the projection 13b and the land portion 5a.

[0036] As shown in Figure 3, the connecting portion 20 has an end face 21a and a projection 21b. The end face 21a is the surface of the connecting portion 20 facing in the Z2 direction. The projection 21b is the portion that protrudes from the end face 21a in the Z2 direction. The cross-section of the projection 21b is rectangular. The connecting portion 20 and the projection 21b have the same thickness in the X direction.

[0037] The projection 21b is inserted into the second through hole 7. The end face 21a abuts against the grounding conductor plate 4 provided on the first surface 2a. Thus, the projection 21b positions the connection portion 20 on the circuit board 2 in the X and Y directions. The end face 21a also positions the connection portion 20 on the circuit board 2 in the Z direction.

[0038] The side surface of the connection portion 20 and the grounding conductor plate 4 are fixed by the solder portion 24a. The tip 21b1 of the projection 21b and the land portion 17 are fixed by the solder portion 24b. The land portion 17 is a conductive pattern made of copper or the like, provided on the surface of the substrate body 3 facing the Z2 direction. A conductive layer made of copper or the like is provided on the inner circumferential surface of the second through hole 7. This conductive layer connects the grounding conductor plate 4 and the land portion 17. The solder portions 24a and 24b, made of solder alloy, are formed by soldering. The solder portions 24a and 24b fix the connection portion 20, including the projection 21b, and the circuit board 2. The solder portions 24a and 24b also electrically connect the connection portion 20 to the grounding conductor plate 4 and the land portion 17. The land portion 17 is not electrically connected to anything other than the projection 21b and the grounding conductor plate 4. As a result, the connection part 20 electrically connects the tip 18a of the first line section 18 with the grounding conductor plate 4.

[0039] As shown in Figure 1, the first element section 14 comprises a second line section 26, a third line section 28, and a fourth line section 30. The second line section 26 is the portion of the first element section 14 that extends linearly from the first end 12a of the columnar section 12. The second line section 26 extends parallel to the Y1 direction (second direction). The second line section 26 has a strip shape with its longitudinal direction parallel to the Y direction. The third line section 28 is the portion of the first element section 14 that extends linearly from the tip 26a of the second line section 26. The third line section 28 extends in a third direction (Z2 direction) opposite to the first direction. The third line section 28 has a strip shape with its longitudinal direction parallel to the Z direction.

[0040] The fourth line section 30 is the portion of the first element section 14 that extends linearly from the tip 28a of the third line section 28. The fourth line section 30 extends parallel to the fourth direction (Y2 direction), which is opposite to the second direction. The fourth line section 30 has a strip shape with its longitudinal direction parallel to the Y direction. A small gap is provided between the tip 30a of the fourth line section 30 and the first side surface 12b of the columnar section 12. The fourth line section 30 is positioned between the second line section 26 and the first line section 18. Therefore, the fourth line section 30 and the second line section 26 are positioned opposite each other. Also, the fourth line section 30 and the first line section 18 are positioned opposite each other.

[0041] The resonant frequency of the transmission line including the first element section 14 is determined by the length from the second end 12c connected to the land section 5a (feed point) to the tip 30a of the fourth transmission line section 30. In this embodiment, the transmission line including the first element section 14 corresponds to signals in the low frequency range from 0.8 GHz to 1 GHz. Therefore, the length from the second end 12c to the tip 30a is set to approximately 1 / 4 of the wavelength of the signal having a low frequency range. The antenna device 1 operates as a multiband antenna because the first element section 14 has this shape.

[0042] According to the above configuration, by providing the second element section 16, the frequency band that the antenna device 1 can transmit and receive can be shifted to a lower frequency side compared to the case where the second element section 16 is not provided. In other words, by providing the second element section 16, the resonant frequency of the line including the first element section 14 can be shifted to an even lower frequency side. As a result, the line length (electrical length) of the antenna element 10 when normalized by the wavelength of the transmittable signal is shortened, making it possible to miniaturize the antenna device 1. In other words, in this embodiment, by providing the second element section 16, the electrical length of the line including the first element section 14 is shortened, making it possible to miniaturize the antenna device 1. In this way, a multiband and miniaturized antenna device 1 can be obtained.

[0043] Also, by providing the second element portion 16, the antenna element 10 is fixed to the circuit board 2 by the second end portion 12c and the connection portion 20. As a result, compared with the case where the second element portion 16 is not provided, the antenna element 10 is more firmly fixed to the circuit board 2.

[0044] Also, in the present embodiment, since the first line portion 18 extends along the Y1 direction and the fourth line portion 30 of the first element portion 14 is arranged to face each other, the first element portion 14 and the first line portion 18 are arranged side by side along the Z1 direction (first direction). Therefore, the size of the antenna element 10 can be made smaller compared with the case where the first element portion 14 and the first line portion 18 are not arranged side by side along the Z1 direction.

[0045] Also, in the present embodiment, the interval g1 shown in FIG. 1 is larger than the interval g2. Thereby, the grounded first line portion 18 and the first element portion can be separated from each other, and deterioration of the characteristics of the antenna element 10 is suppressed. The interval g1 is the Z-direction interval between the first line portion 18 of the second element portion 16 and the fourth line portion 30 of the first element portion 14. The interval g2 is the Z-direction interval between the first line portion 18 and the ground conductor plate 4.

[0046] If the interval g2 is narrowed, it becomes easier to bring the first element portion 14 closer to the circuit board 2, which is advantageous for making the antenna device 1 lower in profile. Therefore, the interval g2 is preferably 3 mm or less, and more preferably 2 mm or less. Also, if the interval g2 is too narrow, there is a risk that foreign matter may be caught between the first line portion 18 and the ground conductor plate 4. Therefore, the interval g2 is preferably 1 mm or more.

[0047] Also, if the interval g1 is narrowed, the influence of the second element portion 16 on the first element portion 14 may occur, and the characteristics of the antenna device 1 may deteriorate. For this reason, the interval g1 is preferably larger than 1 mm, and more preferably 5 mm or more.

[0048] Further, since the first element portion 14 of the present embodiment includes a second line portion 26, a third line portion 28, and a fourth line portion 30, the first element portion has a bent shape. As a result, the length of the first element portion 14 can be significantly increased without significantly extending the length of the first element portion 14 in the Y1 direction (second direction).

[0049] Further, in the present embodiment, the tip 18a of the first line portion 18 is located closer to the columnar portion 12 than the third line portion 28 located at the tip of the first element portion 14. As a result, the length of the first line portion 18 can be suppressed, and the influence of the second element portion 16 on the size of the antenna element 10 can be suppressed.

[0050] [Regarding the Second Embodiment] FIG. 4 is a perspective view showing an example of an antenna device according to the second embodiment. This embodiment is different from the first embodiment in that the antenna element 10 includes a third element portion 32. Other points are the same as those of the first embodiment.

[0051] The third element portion 32 extends linearly from the columnar portion 12. The third element portion 32 extends parallel to the Y1 direction (second direction). The third element portion 32 has a strip shape with its longitudinal direction parallel to the Y direction. The third element portion 32 is located between the second line portion 26 and the fourth line portion 30 of the first element portion 14. Therefore, the second line portion 26, the third element portion 32, and the fourth line portion 30 are arranged side by side along the Z direction.

[0052] A slit-like gap extending in the Y direction is provided between the third element portion 32 and the second line portion 26. A slit-like gap extending in the Y direction is also provided between the third element portion 32 and the fourth line portion 30. The distance between the tip 32a of the third element portion 32 and the third line portion 28 is larger than the gap between the third element portion 32 and the second line portion 26. Thus, the third element portion 32 is provided in the space surrounded by the first element portion 14 without contacting the first element portion 14.

[0053] The resonant frequency of the transmission line including the third element section 32 is determined by the length from the second end 12c connected to the land section 5a (feed point) to the tip 32a of the third element section 32. In this embodiment, the transmission line including the third element section 32 corresponds to a signal in the mid-frequency range of 1.4 GHz to 1.6 GHz. Therefore, the length from the second end 12c to the tip 32a is set to approximately 1 / 4 of the wavelength of the signal having a frequency in the mid-frequency range.

[0054] According to this embodiment, by providing the third element section 32, the frequency band that the antenna device 1 can transmit and receive can be shifted to an even lower frequency. In addition, by providing the third element section 32 in the space enclosed by the first element section 14, the impact of the third element section 32 on the size of the antenna element 10 is suppressed. Furthermore, in this embodiment, since the length of the line including the third element section 32 is different from the length of the line including the first element section 14, the antenna device 1 can be made multiband.

[0055] [Regarding the Third Embodiment] Figure 5 is a perspective view showing the antenna device 1 according to the third embodiment. This embodiment differs from the second embodiment in that the antenna element 10 has an additional element section 34. In other respects, it is the same as the second embodiment.

[0056] The additional element section 34 is connected to the columnar section 12 and extends along the Y2 direction, which is the opposite direction to the Y1 direction (second direction). The additional element section 34 protrudes from the second side surface 12d of the columnar section 12. The second side surface 12d is the side surface of the columnar section 12 on the Y2 direction side. The additional element section 34 comprises a fourth line section 38, a fifth line section 40, a sixth line section 42, and a seventh line section 44.

[0057] The fourth line section 38 is part of the additional element section 34 that connects to the second end 12c of the columnar section 12 and extends from the second end 12c in the Z1 direction. The fourth line section 38 extends parallel and linearly to the columnar section 12 at a slight distance. The fourth line section 38 has a strip shape with its longitudinal direction parallel to the Z direction. The fifth line section 40 is part of the additional element section 34 that extends linearly from the tip 38a of the fourth line section 38. The fifth line section 40 extends parallel to the Y2 direction. The fifth line section 40 has a strip shape with its longitudinal direction parallel to the Y direction. The sixth line section 42 is part of the additional element section 34 that extends linearly from the tip 40a of the fifth line section 40. The sixth line section 42 extends parallel to the Z2 direction. The sixth track section 42 has a strip shape with its longitudinal direction parallel to the Z direction.

[0058] The seventh line section 44 is the portion of the additional element section 34 that extends linearly from the tip 42a of the sixth line section 42. The seventh line section 44 extends parallel to the Y1 direction. The seventh line section 44 has a strip shape with its longitudinal direction parallel to the Y direction.

[0059] The resonant frequency of the transmission line including the additional element section 34 is determined by the length from the second end 12c connected to the land section 5a (feed point) to the tip 44a of the seventh transmission line section 44. In this embodiment, the transmission line including the additional element section 34 corresponds to signals in the high-frequency range of 1.6 GHz to 2.5 GHz. Therefore, the length from the second end 12c to the tip 44a is set to approximately 1 / 4 of the wavelength of the signal having a high-frequency range.

[0060] In this embodiment as well, the additional element section 34 enables multiband operation of the antenna device. Furthermore, the additional element section 34 comprises a fourth line section 38, a fifth line section 40, a sixth line section 42, and a seventh line section 44, and has a bent shape. This allows for a large length of the additional element section 34 without significantly extending its length in the Y2 direction.

[0061] Figure 6 is a perspective view showing an antenna device 1 according to a modification of the third embodiment. This modification differs from the third embodiment in that the antenna element 10 does not have a third element section 32. Even in this configuration, the antenna device can be made multiband by the additional element section 34. In the third embodiment and its modification, the case in which the additional element section 34 extends along the Y2 direction was illustrated. However, the additional element section 34 may be provided to extend along the Y1 direction. In this case, the size of the antenna device 1 in the Y direction can be reduced.

[0062] [Regarding Modifications] Figures 7 and 8 are schematic diagrams showing antenna devices 1 according to other embodiments. Figures 7 and 8 show the Y-Z plane as viewed from the X1 direction. Figure 7A in Figure 7 differs from the third embodiment in that the second element portion 16 extends in the Y2 direction, and the additional element portion 34 is connected to the second element portion 16. Figure 7B in Figure 7 differs from the modification of the third embodiment in that the additional element portion 34 extends from the second end of the columnar portion 12 in the Y2 direction and has an L-shape. Figure 7C in Figure 7 differs from the third embodiment in that the first element portion 14 and the additional element portion 34 each partially have a meander shape. Figure 7D in Figure 7 differs from the third embodiment in that the entire first element portion 14 is formed in a straight line. Figure 7E in Figure 7 differs from the third embodiment in that the entire first element portion 14 is formed in a straight line, and the third element portion 32 partially has a meander shape. Figure 8A in Figure 8 differs from the third embodiment in that the entire first element portion 14 is formed in a straight line, and the third element portion 32 has a bent shape. Figure 8B in Figure 8 differs from the third embodiment in that the portion of the columnar portion 12 to which the additional element portion 34 is connected is located on the Z1 side of the columnar portion 12 than the portion of the columnar portion 12 to which the second element portion 16 is connected. Figure 8C in Figure 8 differs from the third embodiment in that the additional element portion 34 is located between the first element portion 14 and the second element portion 16. Figure 8D in Figure 8 differs from the third embodiment in that the portion of the columnar portion 12 to which the additional element portion 34 is connected is located on the Z2 side of the columnar portion 12 than the portion of the columnar portion 12 to which the second element portion 16 is connected. Figure 8E in Figure 8 differs from the third embodiment in that the width dimension of the columnar portion 12 is wider than the width dimension of the other element portions. In each of the above embodiments, having the second element portion 16 makes it possible to miniaturize the antenna device 1, and a multiband and compact antenna device 1 can be obtained.

[0063] Furthermore, in the above embodiments, examples were given in which the first element portion 14 and the second element portion 16 have a line portion along the Y direction, but the first element portion 14 and the second element portion 16 may further have a line portion along the X direction that intersects the Y direction. In this case, the first element portion 14 and the second element portion 16 are composed of a line portion along the Y direction, a line portion along the X direction, and a bent portion connecting these line portions. Thus, the antenna element 10 may have a line portion along the Y direction and a line portion along the X direction, which are provided by bending or other processes. In this case, the antenna device 1 can be miniaturized. Furthermore, the antenna element 10 will include corners in the X-Y plane, increasing its strength and thereby improving vibration resistance.

[0064] Furthermore, in each of the above embodiments, an example was given in which the line portion 5b of the power supply line 5 extends integrally from the land portion 5a. However, a matching circuit may be provided between the land portion 5a and the line portion 5b. In this case, even if the impedance of the antenna element 10 cannot be properly adjusted on the antenna element 10 side alone, this matching circuit can be used to adjust it appropriately, and the impedance of the antenna element 10 side and the impedance of the power supply line 5 side can be properly matched.

[0065] Furthermore, in each of the above embodiments, the case in which the first line portion 18 of the second element portion 16 extends along the Y1 direction was illustrated. However, the first line portion 18 only needs to extend along a direction parallel to the first surface 2a, and may also extend along a direction intersecting the Y direction on the X-Y plane. In this case, either the first element portion 14 or the first line portion 18 can be bent.

[0066] 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.

[0067] [About the Verification Test] Next, we will explain the verification test conducted on the effects of antenna device 1. The test method involved constructing multiple models of antenna device 1 using computer simulations and determining the characteristics of these models. The effectiveness of antenna device 1 was verified by comparing and confirming the determined characteristics.

[0068] Models were constructed for the following four embodiments and one comparative example. (Embodiment 1) In Embodiment 1, the antenna device 1 shown in the first embodiment is used. The antenna element 10 was formed using brass with a thickness of 1.2 mm.

[0069] Figure 9 is a diagram illustrating the dimensions of the antenna element 10. Although Figure 9 shows the antenna element 10 of the third embodiment, the common parts of the first to third embodiments are set to the same dimensions. Also, the width dimension perpendicular to the longitudinal direction of each line is 2.0 mm in all cases.

[0070] The dimensions of each part of the antenna device 1 according to Example 1 are as follows: - Total length dimension L1 of the second track section 26 and width dimension of the columnar section 12: 39.45 mm - Width dimension V1 of the first element section 14: 8.00 mm - Total length dimension L2 of the fourth track section 30 and width dimension of the third track section 28: 36.45 mm - Length dimension L3 of the first track section 18: 36.45 mm - Distance L4 between the connecting section 20 and the second end 12c of the columnar section 12: 31.45 mm - Height dimension V2 of the second element section 16: 3.30 mm - Length dimension V3 of the projection 21b (projection 13b): 3.00 mm - Width dimension L5 of the connecting section 20: 4.00 mm - Width dimension L6 of the projection 21b: 0.90 mm - Width dimension L7 of the second end 12c of the columnar section 12: 4.00 mm - Width dimension L8 of the projection 13b: 0.90 mm - The distance g1 between the first track section 18 and the fourth track section 30 is 5.00 mm. - The distance g2 between the first track section 18 and the grounding conductor plate 4 is 1.30 mm. The width dimension perpendicular to the longitudinal direction of each track, which is not shown above, is 2.0 mm in all cases.

[0071] (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. • Length L9 of the third element 32: 30.45 mm

[0072] (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 listed below. - Overall length of the antenna element 10 L10: 56.70 mm - Sum of the length of the fifth line section 40 and the width of the fourth line section 38 L11: 16.25 mm - Dimension V4 obtained by subtracting the width of the fifth line section 40 from the length of the fourth line section 38 V4: 13.00 mm - Sum of the length of the sixth line section 42 and the width of the fifth line section 40 V5: 11.00 mm - Sum of the length of the seventh line section 44 and the width of the sixth line section 42 L12: 8.00 mm - Width of the seventh line section 44 V6: 2.00 mm The width dimensions of each line perpendicular to the longitudinal direction, which are not shown above, are all 2.0 mm.

[0073] (Example 4) Example 4 uses an antenna device 1 according to a modification of the third embodiment. The dimensions of each part of the antenna device 1 are the same as in Example 3.

[0074] (Comparative Example) Figure 10 is a perspective view of an antenna device 100 according to a comparative example. The antenna device 100 has a columnar part 102 and an element part 104, which have the same configuration as the columnar part 12 and first element part 14 of Example 1, but does not have a configuration corresponding to the second element part 16. This antenna device 100 was used as a comparative example. The dimensions of each part of the antenna device 100 are the same as those of Example 1.

[0075] (Comparison of Return Loss and Total Efficiency) Figure 11 is an example of a graph showing the frequency characteristics of the return loss for Examples 1 to 4 and the Comparative Example. The horizontal axis of Figure 11 represents frequency. The vertical axis of Figure 11 shows the S-parameter S11 as the return loss when the second end 12c of the antenna element 10 is used as the input terminal.

[0076] In Figure 11, the comparative example has frequency bands in which it can operate as an antenna within both the low-frequency and high-frequency ranges. In the comparative example, the center frequency of the lowest frequency band (hereinafter also referred to as the minimum operating frequency) is approximately 1 GHz (wavelength approximately 300 mm) within the low-frequency range. Example 1 also has frequency bands in which it can operate as an antenna within both the low-frequency and high-frequency ranges. The minimum operating frequency of Example 1 is approximately 0.95 GHz (wavelength approximately 315 mm). From this, it can be seen that the minimum operating frequency is shifted to the lower frequency side by providing the second element section 16. From this result, it can be seen that by providing the second element section 16, the frequency band that can be transmitted and received by the antenna device 1 can be shifted to the lower frequency side, and the electrical length of the antenna element 10 is shortened.

[0077] Furthermore, in Figure 11, Example 2 has a frequency band in which it can operate as an antenna within the low-frequency range and the medium-frequency range. The lowest operating frequency of Example 2 is approximately 0.92 GHz (wavelength approximately 326 mm). Therefore, the lowest operating frequency of Example 2 is shifted to an even lower frequency than the lowest operating frequency of Example 1. From this result, it can be seen that by providing the third element section 32, the frequency band in which the antenna device 1 can transmit and receive can be shifted to an even lower frequency, and the electrical length of the antenna element 10 can be further shortened.

[0078] Examples 3 and 4 also have frequency bands in which they can operate as antennas within the low-frequency and mid-frequency ranges. Examples 3 and 4 do not show a significant impact on the minimum operating frequency, indicating that the additional element 34 does not significantly affect the minimum operating frequency. However, in Examples 3 and 4, the frequency band in which they can operate as antennas within the mid-frequency range is expanded, demonstrating the significant multi-band capability resulting from the addition of the additional element 34.

[0079] Figure 12 is an example of a graph showing the frequency characteristics of the total efficiency of Examples 1 to 4 and the Comparative Example. The horizontal axis of Figure 12 represents frequency. The vertical axis of Figure 12 represents total efficiency. Total efficiency is the ratio of radiated power to input power of the antenna device 1. The same trend as in the case of return loss is observed in total efficiency, and it can be seen that by providing the second element section 16, the frequency band that can be transmitted and received by the antenna device 1 can be shifted to the lower frequency side. Furthermore, it can be seen that by providing the third element section 32, the frequency band that can be transmitted and received can be shifted to the lower frequency side even further.

[0080] (Impedance Comparison) Figure 13 is a Smith chart showing the input impedance of Example 1 and the comparative example. In Figure 13, the thick line shows the change in impedance of Example 1. The thin line shows the impedance of the comparative example. Point P1 on the thick line shows the impedance at 0.6 GHz. Point P2 on the thick line shows the impedance at 0.9 GHz. Point P3 on the thick line shows the impedance at 1.0 GHz. Point P11 on the thin line shows the impedance at 0.6 GHz. Point P12 on the thin line shows the impedance at 0.9 GHz. Point P13 on the thin line shows the impedance at 1.0 GHz. Note that the impedance of the power supply line 5 is 50 Ω, and Figure 13 shows the impedance normalized with Z0 = 50 Ω.

[0081] The resistance (radiation resistance) at 0.9 GHz in Example 1 is 0.223 (11.144 Ω). On the other hand, the resistance (radiation resistance) at 0.9 GHz in the Comparative Example is 0.124 (6.212 Ω). From these results, it can be seen that the radiation resistance increases when the second element section 16 is provided. This means that when the second element section 16 is provided, it becomes easier to match it with the system, such as the power supply line 5.

[0082] (Regarding the effect of spacing g1) Using Example 3, the effect of spacing g1 on the characteristics of the antenna device 1 was confirmed. Spacing g1 was varied in 1 mm increments from 1 mm to 5 mm. The distance from the edge of the first element section 14 to the grounding conductor plate 4 was fixed at 8.3 mm, and spacing g2 was also changed in accordance with the change in spacing g1. In other words, spacing g2 is expressed by the following formula: Spacing g2 = 6.3 mm - Spacing g1

[0083] Figure 14 is a graph showing the frequency characteristics of the return loss of the antenna device 1 when the interval g1 is changed in Example 3. The horizontal axis of Figure 14 represents frequency. The vertical axis of Figure 20 represents S11.

[0084] As can be seen in Figure 14, the characteristics in the low-frequency range tend to shift towards lower frequencies as the interval g1 decreases, while the characteristics in the mid-frequency range tend to shift towards higher frequencies as the interval g1 decreases.

[0085] Here, the return loss in the low-frequency range when the spacing g1 is 1 mm deteriorates sharply compared to other values. Also, in the characteristics in the mid-frequency range when the spacing g1 is 1 mm, the peak around 2 GHz seen in other values ​​disappears, and the characteristics in the mid-frequency range when the spacing g1 is 1 mm are narrower in bandwidth compared to other values. From these results, it is preferable to make the spacing g1 larger than 1 mm. A more preferable value for spacing g1 is 5 mm or more. By making the spacing g1 5 mm or more, the bandwidth of the characteristics in each frequency range is broadened.

[0086] (Regarding the current distribution of each element) The current distribution of each element was confirmed using Example 3. Figure 15 is a diagram showing an example of the current distribution in the Y-Z plane in Example 3. In Figure 15, darker colors indicate stronger current, and lighter colors indicate weaker current. In Figure 15, Figure 15A shows the current distribution when the signal frequency is 0.9 GHz (low frequency range). Figure 15B shows the current distribution when the signal frequency is 1.5 GHz (medium frequency range). Figure 15C shows the current distribution when the signal frequency is 2.0 GHz (high frequency range).

[0087] Looking at Figure 15A, a strong current is shown in the first element section 14, which has the longest transmission line length, indicating that the first element section 14 is operating as the main radiating portion. Looking at Figure 15B, a strong current is shown in the third element section 32, and considering the current distribution in other parts, it can be seen that the third element section 32 is operating as the main radiating portion. Looking at Figure 15C, a strong current is shown in the additional element section 34, indicating that the additional element section 34 is operating as the main radiating portion.

[0088] Furthermore, at all frequencies, current antinodes are generated around the second end 12c of the columnar portion 12, and current nodes are generated at the tip of each element. From this, it can be seen that each element is operating at the fundamental wave (wavelength / 4). Thus, it can be seen that transmission and reception are possible appropriately in each frequency range.

[0089] [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.

[0090] 1 Antenna device 2 Circuit board 2a First side 2b Second side 3 Main board body 4 Grounding conductor plate 4a Slit 4a1 Wide part 4a2 Narrow part 4b Side 5 Feed line 5a Land part 5b Line part 5b1 End part 6 First through hole 7 Second through hole 10 Antenna element 12 Columnar part 12a First end part 12b First side part 12c Second end part 12d Second side part 13a End face 13b Projection 13b1 Tip 14 First element part 15 Land part 16 Second element part 17 Land part 18 First line part 18a Tip 20 Connection part 21a End face 21b Projection 21b1 Tip 22a Solder part 22b Solder part 24a Solder section 24b Solder section 26 Second line section 26a Tip 28 Third line section 28a Tip 30 Fourth line section 30a Tip 32 Third element section 32a Tip 34 Additional element section 38 Fourth line section 38a Tip 40 Fifth line section 40a Tip 42 Sixth line section 42a Tip 44 Seventh line section 44a Tip 100 Antenna device 102 Columnar section 104 Element section S Signal source

Claims

1. An antenna device comprising: a circuit board having a first surface; and an antenna element provided on the circuit board, wherein the antenna element comprises: a columnar portion extending from a power supply portion provided on the first surface along a first direction intersecting the circuit board; a first element portion connected to the columnar portion and extending along a second direction parallel to the first surface; and a second element portion connected to the columnar portion and located closer to the circuit board than the first element portion, wherein the second element portion comprises: a first line portion extending from the columnar portion along a direction parallel to the first surface and positioned opposite to a grounding conductor plate provided on the first surface; and a connecting portion connecting the tip of the first line portion and the grounding conductor plate.

2. The antenna device according to claim 1, wherein the first line portion extends along the second direction and is arranged opposite to the first element portion.

3. The antenna device according to claim 1 or claim 2, wherein the distance between the first line section and the first element section is greater than the distance between the first line section and the grounding conductor plate.

4. The antenna device according to any one of claims 1 to 3, wherein the first element portion comprises a second line portion extending from the columnar portion along the second direction, a third line portion extending from the tip of the second line portion in a third direction opposite to the first direction, and a fourth line portion extending from the tip of the third line portion in a fourth direction opposite to the second direction.

5. The antenna device according to claim 4, further comprising a third element portion connected to the columnar portion and extending along the second direction, wherein the third element portion is located between the second line portion and the fourth line portion.

6. The antenna device according to any one of claims 1 to 4, further comprising a third element portion connected to the columnar portion and extending along the second direction, wherein the third element portion is located between the first line portion and the first element portion.

7. The antenna device according to any one of claims 1 to 6, wherein the tip of the first line portion is located closer to the columnar portion than the tip of the first element portion.

8. The antenna device according to any one of claims 1 to 7, further comprising an additional element connected to the columnar portion.

9. The antenna device according to any one of claims 1 to 8, wherein the antenna element is a member obtained by punching from a conductive metal plate.

10. A wireless communication device comprising an antenna device as described in claim 1, and a communication module that performs transmission and reception using the antenna device.

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