Antenna

Abstract

This antenna comprises a first plate conductor and a columnar conductor provided so as to protrude on a plate surface of the first plate conductor. The tip end of the columnar conductor has a feed point, and the cross-sectional area of a cross-section of the columnar conductor along the plate surface is greater than the area of the end surface of the tip end.

Description

antenna

[0001] This application claims priority to Japanese Patent Application No. 2022-157687, filed on September 30, 2022, and incorporates by reference all of the contents of said Japanese application.

[0002] Conventionally, there has been an antenna for a mobile station in a mobile communication system in which a capacitance loading plate is provided at the tip of a monopole element. Monopole antennas with a capacitance loading plate can be made low-profile, and are therefore sometimes used as vehicle-mounted antennas (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-74206

[0004] The antenna of this embodiment comprises a first plate-shaped conductor and a columnar conductor protruding from the plate surface of the first plate-shaped conductor, the tip of the columnar conductor having a power supply point, and the cross-sectional area of ​​the columnar conductor along the plate surface is larger than the area of ​​the end face of the tip.

[0005] FIG. 1 is a perspective view showing an example of an antenna according to a first embodiment. FIG. 2A is a front view of the antenna according to the first embodiment. FIG. 2B is a side view of the antenna according to the first embodiment. FIG. 3 is a cross-sectional view of the antenna according to the first embodiment taken along the X-Z plane. FIG. 4 is a graph showing a profile curve of a side surface in a cross section of a columnar conductor taken along a plane including the rotation axis. FIG. 5 is a perspective view showing an example of an antenna according to a second embodiment. FIG. 6 is a side view of the antenna according to the second embodiment. FIG. 7 is a cross-sectional view of the antenna according to the second embodiment taken along the X-Z plane. FIG. 8 is a perspective view of the antenna according to a third embodiment. FIG. 9 is a cross-sectional view of the antenna according to the third embodiment taken along the X-Z plane. FIG. 10 is a cross-sectional view taken along the arrow A-A in FIG. 9. FIG. 11 is a perspective view of an antenna according to a fourth embodiment. FIG. 12 is a perspective view of an antenna according to a fifth embodiment. FIG. 13A is a perspective view of an antenna according to a modified example. FIG. 13B is a front view of an antenna according to a modified example. FIG. 14A is a perspective view of an antenna according to another modified example. FIG. 14B is a front view of an antenna according to another modified example. Fig. 15 is a perspective view of an antenna according to a comparative example. Fig. 16 is a cross-sectional view along the XZ plane of the antenna according to the comparative example. Fig. 17 is a diagram showing the frequency characteristics of return loss in comparative example 1. Fig. 18 is a diagram showing the frequency characteristics of return loss in example 1. Fig. 19 is a diagram showing the frequency characteristics of return loss in example 2. Fig. 20 is a diagram showing the frequency characteristics of return loss in example 3. Fig. 21 is a diagram showing the frequency characteristics of return loss in example 4. Fig. 22 is a diagram showing the frequency characteristics of return loss in example 5.

[0006] [Problem to be Solved by the Present Disclosure] In recent years, multi-band mobile communication systems have become more common, and there is a demand for broadband antennas for mobile stations as well. However, while monopole antennas having the above-mentioned capacitance-loaded plate are capable of transmitting and receiving signals in a relatively low frequency band of 1 GHz or less, they have sometimes been unable to support transmission and reception of signals in a relatively high frequency band of several GHz or more, such as SUB6 in fifth-generation mobile communication systems. Thus, while monopole antennas having a capacitance-loaded plate can achieve a low profile, they have had the problem of difficulty in supporting a wide band.

[0007] Therefore, an object of the present disclosure is to provide an antenna that can be made low-profile and is compatible with a wide band.

[0008] Effect of the Present Disclosure According to the present disclosure, an antenna that can be used in a wide band while realizing a low profile can be obtained.

[0009] [Description of the embodiment of the present disclosure] First, the contents of the embodiment will be listed and described. [Outline of the embodiment]

[0010] (1) An embodiment of an antenna comprises a first plate-shaped conductor and a columnar conductor protruding from the plate surface of the first plate-shaped conductor, the tip of the columnar conductor having a power supply point, and the cross-sectional area of ​​the columnar conductor along the plate surface is larger than the area of ​​the end face of the tip.

[0011] According to the above configuration, the first plate conductor functions as a capacitance-loading plate, enabling a low profile while supporting signals in a relatively low frequency band. Furthermore, by appropriately shaping the side surface of the columnar conductor connecting the feed point and the first plate conductor, the change in the characteristic impedance of the first columnar conductor from the feed point to the first plate conductor can be made gentler. This reduces the return loss of the antenna for signals in a relatively high frequency band.

[0012] (2) More specifically, in the antenna of (1) above, the columnar conductor may have a tapered side that tapers from the first plate conductor side toward the tip end side. In this case, a smooth connection can be achieved between the feed point and the first plate conductor. As a result, the change in the characteristic impedance of the columnar conductor from the feed point to the first plate conductor can be made gentler. This reduces the return loss of the antenna for signals in a relatively high frequency band. As a result, an antenna that can be used in a wide frequency band while achieving a low profile can be obtained.

[0013] (3) In the antenna of (1) or (2), the side surface may be a convex curved surface, in which case it is possible to appropriately adjust the change in the characteristic impedance of the columnar conductor.

[0014] (4) In the antenna of any one of (1) to (3) above, the shape of the side surface may be that of a body of revolution with a rotation axis that is a straight line perpendicular to the plate surface, and a contour curve of the side surface in a cross section of the columnar conductor taken along a plane including the rotation axis may satisfy the following formula, where the rotation axis is the y-axis and a straight line at the tip end that is perpendicular to the rotation axis is the x-axis: y = ax Ｐ However, x ≥ 0, a > 0, and P ≥ 1. In this case, the change in the characteristic impedance of the columnar conductor can be more appropriately adjusted.

[0015] (5) In the antenna of (1), the columnar conductor may have a stepped side surface that widens in a stepwise manner from the tip end side toward the first plate conductor side. In this case, the stepped side surface that widens in a stepwise manner can smoothly connect the feed point and the first plate conductor, and can make the change in the characteristic impedance of the columnar conductor more gradual.

[0016] (6) In the antennas of (1) to (5) above, the first plate-like conductor may be strip-shaped. In this case, the size of the antenna in a plan view can be reduced, thereby enabling miniaturization of the antenna.

[0017] (7) In the antenna of (6) above, the columnar conductor may be provided on the first end side of the first plate-like conductor in the longitudinal direction. In this case, it is possible to ensure an appropriate distance from a second end opposite to the first end to the columnar conductor while achieving compactness, and it is possible to more easily achieve a low profile.

[0018] (8) In the antenna of (6) or (7), the width of the first plate-like conductor may be the same as the width of a cross section of the columnar conductor taken along the plate surface, thereby making it possible to further reduce the size of the antenna in a plan view.

[0019] (9) In the antenna of (8), a short side of the first longitudinal end of the first plate-like conductor may have a shape that follows the outline of a cross section of the columnar conductor along the plate surface, thereby further reducing the size of the antenna in a plan view.

[0020] (10) In the antenna of any one of (1) to (9), the columnar conductor may be provided at a position on the plate surface that is offset from the center of the first plate-like conductor. In this case, the distance on the first plate-like conductor from the columnar conductor to the other edge on either side of the center of the first plate-like conductor can be secured as needed, and the antenna can be suitably adapted to signals in a relatively low frequency band.

[0021] (11) In the antenna of (10), the center of the first plate-shaped conductor may be the center of gravity of a contour shape of the first plate-shaped conductor when viewed from above, or the center of a circumscribing circle of the contour shape. The center of gravity of the contour shape and the center of the circumscribing circle are suitable as the center of the first plate-shaped conductor.

[0022] (12) The antenna of any one of (1) to (11) above may further include a short-circuiting conductor that protrudes from the plate surface and grounds the first plate-like conductor. In this case, the short-circuiting conductor can appropriately adjust the input impedance of the antenna, allowing the antenna to be compatible with a wider frequency band.

[0023] (13) In the antenna of (12), the short-circuiting conductor may have a plate shape curved according to a side surface of the columnar conductor and be disposed opposite the side surface of the columnar conductor at a predetermined interval, thereby achieving a broadband coverage of a relatively low frequency band among the available frequency bands.

[0024] (14) The antenna of any one of (1) to (13) above may further include a second plate-shaped conductor that protrudes from a side surface of the columnar conductor and is disposed on the plate surface side of the first plate-shaped conductor so as to face the first plate-shaped conductor. In this case, the antenna can be made into a two-element antenna, and a wider bandwidth can be achieved by increasing the resonant frequency.

[0025] [Details of the Embodiments] Preferred embodiments will now be described with reference to the drawings. At least some of the embodiments described below may be combined in any desired manner. [Overall Configuration of the First Embodiment] FIG. 1 is a perspective view showing an example of an antenna according to the first embodiment. This antenna 1 is an in-vehicle antenna mounted on the roof of a vehicle, for example. The antenna 1 is used in a mobile station of a mobile communication system mounted on a vehicle such as a passenger car, bus, or railcar. The antenna 1 can be used in a fifth-generation mobile communication system.

[0026] In the following description, the three mutually orthogonal directions in each drawing are referred to as the X direction, Y direction, and Z direction. The X direction, indicated by the arrow in FIG. 1, is referred to as the X1 direction, and the opposite direction to the arrow is referred to as the X2 direction. The Y direction, indicated by the arrow in FIG. 1, is referred to as the Y1 direction, and the opposite direction to the arrow is referred to as the Y2 direction. The Z direction, indicated by the arrow in FIG. 1, is referred to as the Z1 direction, and the opposite direction to the arrow is referred to as the Z2 direction.

[0027] The antenna 1 is disposed on a ground conductor 10. The ground conductor 10 has a plate shape parallel to the X-Y plane. The ground conductor 10 is, for example, the roof of a vehicle. Note that FIG. 1 shows only a portion of the ground conductor 10. The antenna 1 includes a first plate-shaped conductor 2, a columnar conductor 4, and a short-circuit conductor 6. The first plate-shaped conductor 2 has a plate shape along the X-Y plane. Therefore, the first plate-shaped conductor 2 and the ground conductor 10 are parallel to each other. The first plate-shaped conductor 2 extends in a strip shape along the X direction. Note that the term "strip shape" refers to a shape that has a constant width and is elongated, like a band or belt, and in this specification refers to a shape that includes an elongated rectangular shape, like the first plate-shaped conductor 2. The columnar conductor 4 and the short-circuit conductor 6 protrude from the first plate-shaped conductor 2 in the Z2 direction. The tips of the columnar conductor 4 and the short-circuit conductor 6 are connected to the ground conductor 10. As a result, the first plate-shaped conductor 2 is disposed facing the ground conductor 10 .

[0028] Fig. 2A is a front view of the antenna 1 according to the first embodiment, and Fig. 2B is a side view of the antenna 1 according to the first embodiment. Fig. 3 is a cross-sectional view of the antenna 1 according to the first embodiment taken along the X-Z plane. Note that Fig. 3 shows a cross section passing through the center of the antenna 1 in the Y direction.

[0029] 2A and 2B, a connector 13 to which a coaxial cable (not shown) is connected is provided on the first surface 10a of the ground conductor 10. As shown in Fig. 3, a hole 11 is provided in the ground conductor 10. The connector 13 is inserted into the hole 11. The connector 13 has a cylindrical insulating member 13a, a pin 12, and a main body 13b. The insulating member 13a is inserted into the hole 11. The insulating member 13a has a through-hole 13a1 that penetrates in the Z direction.

[0030] The pin 12 is inserted into the through hole 13a1. Therefore, the pin 12 is insulated from the ground conductor 10 by the insulating member 13a. The pin 12 protrudes from the second surface 10b and the end surface 13a2 of the insulating member 13a. The second surface 10b is the surface facing the Z1 direction of the ground conductor 10. The pin 12 is connected to the inner conductor (not shown) of the coaxial cable. The main body 13b connects the outer conductor (not shown) of the coaxial cable to the ground conductor 10.

[0031] The columnar conductor 4 is a columnar member formed of a conductor such as copper. The columnar conductor 4 is provided to protrude from the plate surface 2a of the first plate conductor 2. The plate surface 2a is the plate surface of the first plate conductor 2 facing the Z2 direction. The columnar conductor 4 has a tip portion 16, a base end surface 18, and a side surface 20. The tip portion 16 has an end surface 19. The end surface 19 is the end surface of the columnar conductor 4 facing the Z2 direction. The base end surface 18 is the end surface facing the Z1 direction, which is the opposite direction to the end surface 19. The side surface 20 is a surface connecting the end surface 19 and the base end surface 18. The side surface 20 has a shape that tapers from the base end surface 18 (first plate conductor 2) side toward the tip portion 16 side.

[0032] The base end surface 18 abuts against the plate surface 2a of the first plate conductor 2. Thus, the columnar conductor 4 is electrically connected to the first plate conductor 2. The first plate conductor 2 and the columnar conductor 4 are fixed together in abutting contact with each other by a plurality of screws (not shown).

[0033] The columnar conductor 4 and the first plate-like conductor 2 being electrically connected includes not only the case where the columnar conductor 4 and the first plate-like conductor 2 are in direct contact with each other or are electrically connected via another conductor, but also the case where the columnar conductor 4 and the first plate-like conductor 2 are connected at high frequency by being capacitively coupled to each other. The same applies to the connection between conductors in the following description.

[0034] The end face 19 abuts against the end face 13a2 of the insulating member 13a. Therefore, the columnar conductor 4 and the ground conductor 10 are not electrically connected. As shown in FIG. 3 , a tip hole 17 is opened in the end face 19. The tip hole 17 is a cylindrical hole provided along the Z direction. The pin 12 is inserted into the tip hole 17. The inner circumferential surface of the tip hole 17 and the outer circumferential surface of the pin 12 are in contact. Therefore, the columnar conductor 4 and the pin 12 are electrically connected. The pin 12 is electrically connected to the inner conductor of the coaxial cable. Therefore, the opening edge 19a of the tip hole 17 in the end face 19 is the power supply point.

[0035] The columnar conductor 4 has a hole 21. The hole 21 is a cylindrical hole provided along the Z direction. The hole 21 opens to the base end surface 18. The hole 21 has a small diameter portion 21a and a large diameter portion 21b. The small diameter portion 21a and the large diameter portion 21b are concentrically connected to each other. The small diameter portion 21a is provided on the tip end portion 16 side. The large diameter portion 21b is provided on the base end surface 18 side. The hole 21 and the tip hole 17 are concentric and connected to each other. In other words, the tip hole 17 and the hole 21 penetrate the columnar conductor 4 along the Z direction.

[0036] As shown in FIG. 3 , the pin 12 inserted into the tip hole 17 protrudes into the hole 21. The pin 12 and the columnar conductor 4 are joined by a welding member (not shown) formed by, for example, soldering or brazing. The shape of the hole 21 in the columnar conductor 4 is not particularly limited. However, the hole 21 in the columnar conductor 4 may be used as a work space when forming a welding member that joins the pin 12 and the columnar conductor 4. In this case, from the viewpoint of workability, it is preferable that the inner diameter of the hole 21 be as large as possible. To increase the inner diameter of the hole 21 as much as possible, it is possible to form the inner circumferential surface of the hole 21 so that the diameter gradually increases from the tip end 16 side toward the base end surface 18 side along the shape of the side surface 20. However, in this case, it is considered that the cost required for forming the hole 21 increases. Therefore, in this embodiment, the hole 21 is configured with a small diameter portion 21a and a large diameter portion 21b. This allows the large diameter portion 21b to ensure a relatively large inner diameter of the hole 21, while reducing the cost required to form the hole 21.

[0037] The columnar conductor 4 has a shape of a body of revolution. The axis of revolution S of the columnar conductor 4 is a straight line perpendicular to the plate surface 2a and extends along the Z direction. The axis of revolution S also passes through the center of the tip hole 17. Therefore, the outline shape of the cross section of the columnar conductor 4 along the XY plane is circular. Therefore, the side surface 20 of the columnar conductor 4 has the side surface shape of the body of revolution. The shape of the side surface 20 will be described in detail later.

[0038] As described above, the first plate conductor 2 extends in a band shape along the X direction. The columnar conductor 4 is provided on the first end 2b side of the first plate conductor 2 in the longitudinal direction (the X2 direction side of the first plate conductor 2). In other words, the first end 2b side of the first plate conductor 2 is electrically connected to the columnar conductor 4 having the power feed point. Therefore, the second end 2c side of the first plate conductor 2 is an open end. The second end 2c is the end opposite the first end 2b in the longitudinal direction of the first plate conductor 2. The longitudinal direction of the first plate conductor 2 is the extension direction of the band-shaped first plate member 2, which is the direction along the X direction.

[0039] As shown in FIG. 1 , the short side 2c1 of the first plate-shaped conductor 2 on the second end 2c side is an end face along the Y direction and is a plane parallel to the Y-Z plane. On the other hand, the short side 2b1 on the first end 2b side in the longitudinal direction of the first plate-shaped conductor 2 has a curved surface that is continuous with the side surface 20 without any steps. The short side 2b1 may also be a curved surface that is parallel to the Z direction and follows the side surface 20 in the X-Y plane. This is advantageous in terms of ease of manufacture and cost. In addition, in this case, the short side 2b1 may slightly protrude or recess relative to the side surface 20. However, these protrusions and recesses are very slight and have little effect on the effect of gradual change in characteristic impedance, which will be described later.

[0040] The pair of long sides 2d1 of the first plate conductor 2 are end faces along the X direction and are planes parallel to the X-Z plane. The width dimension of the first plate conductor 2 along the Y direction is approximately the same as the width dimension of the base end face 18 along the Y direction. The base end face 18 is also a cross section of the columnar conductor 4 along the plate surface 2a.

[0041] The first plate-shaped conductor 2 functions as a capacitance loading plate for the columnar conductor 4. Therefore, instead of a strip-shaped member as in this embodiment, a plate-shaped member with a larger area can be used. However, by making the first plate-shaped conductor 2 strip-shaped as in this embodiment, the size of the antenna 1 in a plan view can be reduced while maintaining the characteristics of the antenna 1, thereby achieving miniaturization of the antenna 1. Furthermore, by making the width dimension of the first plate-shaped conductor 2 the same as the width dimension of the base end surface 18 of the columnar conductor 4, the size of the antenna 1 in a plan view can be further reduced. Furthermore, in this embodiment, the short side portion 2b1 on the first end 2b side of the first plate-shaped conductor 2 has a shape that follows the contour shape of the base end surface 18, so the size of the antenna 1 in a plan view can be further reduced.

[0042] The short-circuiting conductor 6 is a cylindrical member protruding from the plate surface 2a of the first plate-shaped conductor 2. As shown in FIG. 3 , the short-circuiting conductor 6 is provided at a predetermined distance from the columnar conductor 4. The short-circuiting conductor 6 includes a conductor body 6a and a spacer 6b. The conductor body 6a is a long screw made of a conductor such as copper, mechanical structural steel, or alloy steel. The spacer 6b is a cylindrical member made of an insulator or conductor such as resin. The spacer 6b is disposed between the first plate-shaped conductor 2 and the grounding conductor 10. The first plate-shaped conductor 2 and the grounding conductor 10 are provided with holes 2e and 10d for attaching the short-circuiting conductor 6. The spacer 6b is disposed along the Z direction. The inner peripheral holes of the spacer 6b are aligned with the holes 2e and 10d of the first plate-shaped conductor 2 and the grounding conductor 10. The length of the spacer 6b is set to be approximately the same as the length of the columnar conductor 4 in the Z direction. Both end faces of the spacer 6b abut against the first plate-shaped conductor 2 and the ground conductor 10. In this way, the spacer 6b determines the distance between the first plate-shaped conductor 2 and the ground conductor 10.

[0043] The conductor body 6a is inserted through the hole 2e, the spacer 6b, and the hole 10d. A nut 7 is attached to the threaded portion at the tip of the conductor body 6a. By tightening the nut 7, the first plate-shaped conductor 2, the spacer 6b, and the ground conductor 10 are fastened between the screw head 6a1 of the conductor body 6a and the nut 7. This reduces the load acting on the tip 16 of the columnar conductor 4 connected to the ground conductor 10, thereby firmly holding the antenna 1. Note that the screw head 6a1 is omitted in FIG. 2B . A conductive washer 8 is interposed between the screw head 6a1 and the first plate-shaped conductor 2. A conductive washer 9 is also interposed between the nut 7 and the ground conductor 10. As a result, the short-circuit conductor 6 electrically connects the first plate-shaped conductor 2 and the ground conductor 10, grounding the first plate-shaped conductor 2. In this case, the short-circuit conductor 6 can appropriately adjust the input impedance of the antenna 1, allowing the antenna 1 to support a wider frequency band.

[0044] [Regarding the Side Surface 20 of the Columnar Conductor 4] As described above, the side surface 20 of the columnar conductor 4 is tapered from the first plate-shaped conductor 2 side toward the tip 16 side. Here, in this embodiment, tapered means that the side surface 20 as a whole tapers from the first plate-shaped conductor 2 side toward the tip 16 side. Even if there is a partial protrusion or recess, the shape of the side surface 20 as a whole tapers from the first plate-shaped conductor 2 side toward the tip 16 side is considered tapered.

[0045] The side surface 20 is a smooth convex curve. Fig. 4 is a graph showing the contour curve of the side surface 20 in the cross section of the columnar conductor 4 taken along a plane including the rotation axis S. Fig. 4 shows the contour curve C when the rotation axis S is taken as the y-axis and a straight line at the end surface 19 perpendicular to the rotation axis S is taken as the x-axis. The contour curve C shown in Fig. 4 satisfies the following formula (1): y = ax Ｐ ...(1) where x≧0, a>0, and P≧1.

[0046] The columnar conductor 4 of this embodiment has a side surface 20 with a contour curve that satisfies the above formula (1). Therefore, the area of ​​the base end surface 18 (the cross-sectional area of ​​the columnar conductor 4 taken along the plate surface 2a) is larger than the area of ​​the end surface 19 of the tip portion 16. In this case, the contour length of the base end surface 18 and the contour length of the end surface 19 are different from each other. In contrast, the side surface 20 tapers from the first plate conductor 2 side toward the tip portion 16 side.

[0047] In other words, the columnar conductor 4 of this embodiment has a side surface 20 with a contour curve that satisfies the above formula (1), and therefore has a shape in which the cross-sectional area of ​​the columnar conductor 4 along a plane parallel to the plate surface 2a gradually decreases as it moves from the first plate conductor 2 side toward the tip portion 16 side.

[0048] With this configuration, the first plate-shaped conductor 2 functions as a capacitance-loading plate, enabling a low profile while supporting signals in a relatively low frequency band, for example, below 1 GHz. Furthermore, the columnar conductor 4 has a tapered side surface 20 that tapers from the first plate-shaped conductor 2 toward the tip end 16, allowing the contours of the base end surface 18 and the end surface 19, which have different lengths, to be smoothly connected. This allows for a gentle change in the characteristic impedance of the columnar conductor 4 from the tip end 16, which has the feed point, to the first plate-shaped conductor 2. This reduces the return loss of the antenna 1 for signals in a relatively high frequency band above several GHz, such as SUB6. As a result, an antenna 1 can be obtained that supports a wide frequency band while achieving a low profile.

[0049] The height of the antenna 1 is preferably about 0.07 times the wavelength in a relatively low frequency band of 1 GHz or less among the frequency bands supported by the antenna 1. For example, if the frequency band supported by the antenna 1 includes 800 MHz, the wavelength is about 380 mm, and therefore the height of the antenna 1 is preferably about 27 mm.

[0050] Furthermore, since the side surface 20 is a convex curved surface and the contour curve of the side surface 20 satisfies the above formula, it is possible to more appropriately adjust the change in the characteristic impedance of the columnar conductor 4. The contour curve of the side surface 20 is a curve that indicates the overall shape of the side surface 20. Therefore, even if the side surface 20 has a partial protrusion or depression, the contour curve of the side surface 20 is considered to satisfy the above formula as long as the contour curve that indicates the overall shape of the side surface 20 satisfies the above formula.

[0051] Furthermore, in this embodiment, by arranging the columnar conductor 4 on the first end 2b side of the first plate-shaped conductor 2, it is possible to achieve compactness while appropriately ensuring the distance from the second end 2c of the first plate-shaped conductor 2 to the columnar conductor 4, making it easier to achieve a low profile.

[0052] In the present embodiment, the antenna 1 is obtained by assembling the first plate-shaped conductor 2 and the columnar conductor 4, but the antenna 1 may be configured using an integrally formed first plate-shaped conductor 2 and the columnar conductor 4. Furthermore, in the above first embodiment, the columnar conductor 4 is formed integrally, but the columnar conductor 4 may be configured by combining multiple divided bodies, as in the second embodiment described below.

[0053] [Regarding the Second Embodiment] Fig. 5 is a perspective view of the antenna 1 according to the second embodiment, and Fig. 6 is a side view of the antenna 1 according to the second embodiment. Note that the screw heads 6a1 are omitted in Fig. 6. This embodiment differs from the first embodiment in that the antenna 1 includes a second plate conductor 30. The second plate conductor 30 is provided to protrude from the side surface 20 of the columnar conductor 4 and is disposed opposite the first plate conductor 2. The second plate conductor 30 is disposed between the first plate conductor 2 and the ground conductor 10.

[0054] The second plate-shaped conductor 30 has a plate shape along the XY plane. Therefore, the second plate-shaped conductor 30 and the ground conductor 10 are parallel to each other. The second plate-shaped conductor 30 also extends in a strip shape along the X direction.

[0055] As shown in FIG. 5 , the third longitudinal end 30b of the second plate conductor 30 is connected to the side surface 20 of the columnar conductor 4. Meanwhile, the short side 30c1 of the second plate conductor 30 at the fourth end 30c is an end face along the Y direction and is a plane parallel to the Y-Z plane. Furthermore, the pair of long sides 30d1 of the second plate conductor 30 are end faces along the X direction and are planes parallel to the X-Z plane. The position of the short side 30c1 of the second plate conductor 30 in the X direction is the same as the position of the short side 2c1 of the first plate conductor 2 in the X direction. Furthermore, the position of the pair of long sides 30d1 of the second plate conductor 30 in the Y direction is the same as the position of the pair of long sides 2d1 of the first plate conductor 2 in the Y direction. Therefore, the width dimension of the second plate conductor 30 in the Y direction is the same as the width dimension of the first plate conductor 2 in the Y direction. Therefore, the projected shape of the pair of long sides 30d1 and short sides 30c1 of the second plate-shaped conductor 30 in the XY plane coincides with the projected shape of the pair of long sides 2d1 and short sides 2c1 of the first plate-shaped conductor 2 in the XY plane.

[0056] A pair of long side portions 30d1 of the second plate-shaped conductor 30 extend to the position of the rotation axis S in the X direction. The diameter of the columnar conductor 4 at the position in the Z direction where the second plate-shaped conductor 30 is located is smaller than the diameter of the base end surface 18. Therefore, an edge 30d2 on the X2 direction side of the long side portion 30d1 protrudes beyond the side surface 20. Therefore, the third end portion 30b of the second plate-shaped conductor 30 has a pair of end flat portions 33 on both sides of the columnar conductor 4. As shown in FIGS. 5 and 6 , the pair of end flat portions 33 are surfaces facing the X2 direction. The pair of end flat portions 33 are planes parallel to the Y-Z plane.

[0057] FIG. 7 is a cross-sectional view of the antenna 1 according to the second embodiment taken along the X-Z plane. Note that FIG. 7 shows a cross section passing through the center of the antenna 1 in the Y direction. As shown in FIG. 7, the columnar conductor 4 includes a first divided body 22 and a second divided body 24. The first divided body 22 is a member formed of a conductor such as copper. The first divided body 22 includes the tip portion 16 described above. The first divided body 22 also includes a hole 21. The hole 21 opens to an abutment surface 22a. The abutment surface 22a is a surface of the first divided body 22 opposite the end surface 19.

[0058] The second divided body 24 is a member formed of a conductor such as copper. The second divided body 24 includes a base end surface 18. A contact surface 24a of the second divided body 24 is provided with a protrusion 24a1 that fits into the hole 21. The contact surface 24a is a surface of the second divided body 24 that is on the opposite side of the base end surface 18. The protrusion 24a1 determines the positioning between the first divided body 22 and the second divided body 24.

[0059] As shown in FIG. 7 , a plate member 40 is sandwiched and fixed between the first division 22 and the second division 24. The plate member 40 includes the second plate conductor 30 described above and an intervening portion 42. The intervening portion 42 is a portion intervening between the first division 22 and the second division 24. The intervening portion 42 constitutes a part of the columnar conductor 4. When the plate member 40 is fixed between the first division 22 and the second division 24, the portion of the plate member 40 protruding from the columnar conductor 4 becomes the second plate conductor 30. In other words, the portion of the plate member 40 on the X1 direction side of the boundary portion 32 in FIG. 7 is the second plate conductor 30. The portion of the plate member 40 on the X2 direction side of the boundary portion 32 is the intervening portion 42.

[0060] As described above, the columnar conductor 4 of this embodiment is composed of the first division 22, the second division 24, and the intervening portion 42. The plate-shaped intervening portion 42 is sandwiched between the abutment surface 22a and the abutment surface 24a. As a result, the first division 22 and the intervening portion 42 abut against each other. Furthermore, the intervening portion 42 and the second division 24 abut against each other. Therefore, the first division 22, the second division 24, and the intervening portion 42 are electrically connected to each other. As a result, the second plate-shaped conductor 30 and the columnar conductor 4 are electrically connected to each other.

[0061] The end face of the intervening portion 42 facing the X2 direction has a curved surface that is continuous with the side face 20 without any steps. Note that, like the short side portion 2b1 of the first plate-shaped conductor 2, the end face of the intervening portion 42 facing the X2 direction may be a curved surface that is parallel to the Z direction and follows the side face 20 in the XY plane. A hole 42a is provided in the intervening portion 42. A protrusion 24a1 is inserted into the hole 42a. This positions the intervening portion 42 (plate member 40) with respect to the first divided body 22 and the second divided body 24.

[0062] The first division 22, the second division 24, and the intermediate portion 42 are combined with one another and fixed together with the first plate-shaped conductor 2 by screws (not shown) or the like. The first division 22 and the second division 24 are fixed together after the pin 12 is joined to the first division 22. This is because, as described above, the hole 21 in the first division 22 can be used as a work space when forming the welding member that joins the pin 12 to the first division 22.

[0063] The second plate-shaped conductor 30 has a hole 30e through which the conductor body 6a of the short-circuit conductor 6 is inserted. The conductor body 6a is inserted through hole 2e, hole 30e, spacer 6b, and hole 10d. The spacer 6b includes a first body portion 36 and a second body portion 38. The first body portion 36 and the second body portion 38 are cylindrical members made of an insulating material such as resin. The second body portion 38 is disposed between the ground conductor 10 and the second plate-shaped conductor 30. Both end faces of the second body portion 38 abut against the second plate-shaped conductor 30 and the ground conductor 10. This allows the second body portion 38 to determine the distance between the second plate-shaped conductor 30 and the ground conductor 10.

[0064] The first body portion 36 is disposed between the first plate conductor 2 and the second plate conductor 30. The first body portion 36 has a large diameter portion 36a and a small diameter portion 36b. The small diameter portion 36b protrudes from one end surface of the large diameter portion 36a. The small diameter portion 36b is inserted into the hole 30e of the second plate conductor 30. The small diameter portion 36b is interposed between the conductor body 6a and the second plate conductor 30. Therefore, the conductor body 6a and the second plate conductor 30 are insulated from each other. Both end surfaces of the large diameter portion 36a abut against the first plate conductor 2 and the second plate conductor 30. As a result, the large diameter portion 36a determines the distance between the first plate conductor 2 and the second plate conductor 30.

[0065] As described above, the antenna 1 of this embodiment includes the second plate-like conductor 30 that protrudes from the side surface 20 of the columnar conductor 4 and is disposed opposite the first plate-like conductor 2 on the plate surface 2a side of the first plate-like conductor 2. This allows the antenna 1 to be made into a two-element configuration, and the increased resonant frequency enables a wider bandwidth.

[0066] In this embodiment, an example is given of an antenna 1 being obtained by assembling a first plate-shaped conductor 2, a plate member 40, a first divided body 22, and a second divided body 24, but the antenna 1 may also be constructed using a first plate-shaped conductor 2, a second plate-shaped conductor 30, and a columnar conductor 4 formed integrally.

[0067] Furthermore, in this embodiment, the projected shape of the second plate conductor 30 in the X-Y plane and the projected shape of the first plate conductor 2 in the X-Y plane are identical. However, the projected shape of the second plate conductor 30 in the X-Y plane and the projected shape of the first plate conductor 2 in the X-Y plane do not have to be identical. Furthermore, in addition to the first plate conductor 2 and the second plate conductor 30, another plate conductor may be provided. In this case, the other plate conductor is provided so as to protrude from the side surface 20 of the columnar conductor 4. In this case, the other plate conductor is provided at a predetermined distance in the Z direction from the first plate conductor 2 and the second plate conductor 30.

[0068] Furthermore, the first plate-shaped conductor 2 and the plate member 40 may have exactly the same shape. In this case, the first plate-shaped conductor 2 can be used not only as the first plate-shaped conductor 2 but also as the plate member 40. This allows for cost reduction through mass production. When the first plate-shaped conductor 2 is used as the plate member 40, the edge of the plate member 40 (the edge of the first end 2b of the first plate-shaped conductor 2 when used as the plate member 40) protrudes from the side surface 20 of the columnar conductor 4. However, the side surface 20 can be said to have a shape that tapers overall from the first plate-shaped conductor 2 side toward the tip end 16 side, and this does not have a significant effect.

[0069] [Regarding the Third Embodiment] Fig. 8 is a perspective view of an antenna 1 according to a third embodiment, and Fig. 9 is a cross-sectional view of the antenna 1 according to the third embodiment taken along the X-Z plane. In Fig. 8, the first plate-shaped conductor 2 is shown by an imaginary line (two-dot chain line) for ease of understanding. Fig. 9 also shows a cross section passing through the center of the antenna 1 in the Y direction. This embodiment differs from the second embodiment in that the short-circuit conductor 6 has a plate shape.

[0070] The short-circuit conductor 6 of this embodiment has a main body member 6c made of a conductor such as copper formed into a plate shape. A fifth end 6c1 of the main body member 6c is fixed in contact with the first plate-shaped conductor 2, thereby electrically connecting the main body member 6c and the first plate-shaped conductor 2. A sixth end 6c2 of the main body member 6c is fixed in contact with the ground conductor 10, thereby electrically connecting the main body member 6c and the ground conductor 10. Therefore, the main body member 6c grounds the first plate-shaped conductor 2.

[0071] The main body member 6c has a plate shape that is curved according to the side surface 20 of the columnar conductor 4, and is disposed opposite the side surface 20 of the columnar conductor 4 with a predetermined distance therebetween. As shown in Fig. 8, the hole 30e of the second plate conductor 30 has a hole shape that is curved according to the shape of the main body member 6c. A gap is provided between the main body member 6c and the hole 30e. Therefore, the main body member 6c and the second plate conductor 30 are insulated from each other.

[0072] 9 , the radial distance D between the first surface 6c3 of the main body member 6c in a cross section including the diameter of the columnar conductor 4 and the side surface 20 of the columnar conductor 4 is constant in the Z direction. In other words, the main body member 6c has a curved shape that follows the side surface when the radius of the columnar conductor 4 is expanded by D.

[0073] FIG. 10 is a cross-sectional view taken along the arrow A-A in FIG. 9 . In FIG. 10 , the radial distance between the contour line 19b and the edge 6c4 is D1, and the radial distance between the contour line 20a and the edge line 6c5 is D2. The contour line 19b is the contour line of the end face 19. The edge 6c4 is the edge of the sixth end 6c2 of the main body member 6c. The edge 6c4 is an arc centered on the rotation axis S. The edge 6c4 and the contour line 19b are located at the same position in the Z direction. Here, when the insulating member 13a slightly protrudes from the second surface 10b of the ground conductor 10, as in this embodiment, the Z-direction position of the edge 6c4 may be slightly misaligned with the Z-direction position of the contour line 19b. In such a case, the positions of the main body member 6c and the columnar conductor 4 are adjusted so that the Z-direction position of the edge 6c4 and the Z-direction position of the contour line 19b coincide with each other. For ease of understanding, it is assumed here that the position of the edge 6c4 in the Z direction is the same as the position of the contour line 19b in the Z direction.

[0074] The contour line 20a is the contour line of the side surface 20 in the cross section of the columnar conductor 4 in Fig. 10. The contour line 6c5 is the contour line of the first surface 6c3 in the cross section of the main body member 6c in Fig. 10. The contour line 6c5 is an arc centered on the rotation axis S.

[0075] 10 , the distance D1 and the distance D2 have the same value D. In this way, the distance D along the radial direction between the main body member 6c and the columnar conductor 4 has the same value regardless of the position in the Z direction and the position in the circumferential direction around the rotation axis S. In this way, the main body member 6c has a curved shape that fits along the side surface when the radius of the columnar conductor 4 is expanded by D.

[0076] In this embodiment, the short-circuit conductor 6, which is curved according to the side surface 20 of the columnar conductor 4, is arranged opposite the side surface 20 at a distance D, thereby making it possible to widen the bandwidth for relatively low frequency bands among the available frequency bands.

[0077] [Regarding the Fourth Embodiment] Fig. 11 is a perspective view of an antenna 1 according to a fourth embodiment. In Fig. 11, the first plate conductor 2 is shown by an imaginary line (two-dot chain line) for ease of understanding. This embodiment differs from the second and third embodiments in that the first plate conductor 2 and the second plate conductor 30 have a circular shape and the main body member 6c of the short-circuit conductor 6 has a rectangular plate shape.

[0078] 11 , the first plate-shaped conductor 2 and the second plate-shaped conductor 30 have a circular shape centered on the rotation axis S. Therefore, the columnar conductor 4 is provided at the center of the first plate-shaped conductor 2 and the second plate-shaped conductor 30.

[0079] The main body member 6c of the short-circuit conductor 6 is formed in a plate shape along the YZ plane. The main body member 6c extends in the Z direction. The hole 30e of the second plate-shaped conductor 30, through which the main body member 6c is inserted, is formed in a rectangular shape corresponding to the shape of the main body member 6c. In this embodiment as well, a gap is provided between the main body member 6c and the hole 30e. Therefore, the main body member 6c and the second plate-shaped conductor 30 are insulated from each other.

[0080] [Regarding the Fifth Embodiment] Fig. 12 is a perspective view of an antenna 1 according to a fifth embodiment. In Fig. 12, the first plate conductor 2 is shown by an imaginary line (two-dot chain line) for ease of understanding. This embodiment differs from the fourth embodiment in that the rotation axis S of the columnar conductor 4 does not coincide with the central axis T of the first plate conductor 2 and the second plate conductor 30.

[0081] 12 , the columnar conductor 4 of this embodiment is provided at a position shifted in the X2 direction from the central axis T. The edge 18a of the base end surface 18 of the columnar conductor 4 coincides with the edge 2f1 of the first plate-like conductor 2. In other words, the columnar conductor 4 is provided at the outermost end of the first plate-like conductor 2.

[0082] In this way, since the columnar conductor 4 is provided at a position offset from the central axis T of the first plate-shaped conductor 2, the distance on the first plate-shaped conductor 2 from the columnar conductor 4 to the other edge 2f2 on either side of the central axis T can be secured as needed, making it possible to suitably accommodate signals in a relatively low frequency band. Note that in the first to third embodiments, the columnar conductor 4 is also provided between the center of the first plate-shaped conductor 2 and the edge of the first plate-shaped conductor 2. The center in this case is, for example, the center of gravity of the contour shape of the first plate-shaped conductor 2.

[0083] [Regarding Modifications] In the above embodiments, the side surface 20 of the columnar conductor 4 is a smoothly curved surface. However, the side surface 20 may have a stepped shape that gradually widens from the end surface 19 toward the first plate-like conductor 2, as shown in Figures 13A and 13B. Furthermore, the side surface 20 may have a conical surface, as shown in Figures 14A and 14B. In these cases, the change in the characteristic impedance of the columnar conductor 4 can be made gradual, just like when the side surface is a smoothly curved surface.

[0084] In addition, in each of the above embodiments, the side surface 20 of the columnar conductor 4 has a solid of revolution shape, and the cross-sectional contour shape of the columnar conductor 4 along the X-Y plane is circular. However, the cross-sectional contour shape of the columnar conductor 4 along the X-Y plane may be oval, elliptical, or polygonal. In addition, in each of the above embodiments, the columnar conductor 4 (first divided body 22 and second divided body 24) is formed from a conductor. However, the columnar conductor 4 may also be configured to include, for example, a main body formed from a resin or the like and a conductive coating formed on the surface of the main body.

[0085] In the above embodiments, the first plate conductor 2 has a strip or a circle. However, the first plate conductor 2 may have a polygonal shape, such as a triangle or a pentagon, or may have an oval or elliptical shape. Furthermore, in the above embodiments, the center of the first plate conductor 2 is set as the center of gravity of the outline shape of the first plate conductor 2 when viewed from above, and the position of the columnar conductor 4 is determined based on the center of gravity of the first plate conductor 2. In contrast, when the first plate conductor 2 has a polygonal shape, the center of the first plate conductor 2 may be set as the center of a circumscribing circle of the outline shape of the first plate conductor 2, and the position of the columnar conductor 4 may be determined based on this center. The center of gravity of the first plate conductor 2 or the center of the circumscribing circle of the outline shape of the first plate conductor 2 can be suitably used as the center of the first plate conductor 2.

[0086] In addition, in each of the above embodiments, the case where one short-circuit conductor 6 is provided has been exemplified. However, a plurality of short-circuit conductors 6 may be provided. In this case, the load acting on the tip 16 of the columnar conductor 4 connected to the ground conductor 10 can be further reduced, and the antenna 1 can be held more firmly.

[0087] [Regarding Verification Test 1] Next, a description will be given of Verification Test 1, which was conducted to examine the effects of antenna 1. As a test method, a model of antenna 1 was constructed, and the model was used to determine the frequency characteristics of the return loss (S parameter S11) of antenna 1 through computer simulation. In Verification Test 1, one comparative example and five examples shown below were used as test subjects, and the effects of antenna 1 were verified by comparing the determined frequency characteristics of return loss with each other.

[0088] Example 1 The antenna 1 shown in the first embodiment was constructed as a model for Example 1. The dimensions of each part of the first plate-like conductor 2 were set as follows: Width (Y-direction dimension): 30 mm Length (X-direction dimension): 95 mm Plate thickness: 1 mm Furthermore, the dimensions of each part of the columnar conductor 4 were set as follows: Height (Z-direction dimension): 26 mm Diameter of base end surface 18: 30 mm In the above formula (1), a = 1, P = 1.7 The width (Y-direction dimension) of the antenna 1 was 30 mm, the length (Y-direction dimension) of the antenna 1 was 95 mm, and the height (Z-direction dimension) of the antenna 1 was 27 mm. Furthermore, the diameter of the conductor body 6a of the short-circuiting conductor 6 was 2.5 mm. The distance in the X direction between the central axis of the columnar conductor 4 and the central axis of the short-circuiting conductor 6 was 30 mm.

[0089] Example 2 The antenna 1 shown in the second embodiment was constructed as a model for Example 2. That is, in Example 2, an antenna 1 in which a second plate-shaped conductor 30 was added to Example 1 was verified. The width dimension in the Y direction of the second plate-shaped conductor 30 was set to 30 mm. The plate thickness of the second plate-shaped conductor 30 was set to 1 mm. The other dimensions were the same as those of Example 1.

[0090] Example 3 The antenna 1 shown in the third embodiment was constructed as a model for Example 3. That is, in Example 3, an antenna 1 in which the short-circuit conductor 6 of Example 2 was made plate-shaped was verified. The short-circuit conductor 6 of Example 3 has a plate shape curved in accordance with the side surface 20 of the columnar conductor 4. The width dimension in the Y direction of the fifth end 6c1 of the short-circuit conductor 6 was set to 20 mm. The distance in the X direction between the center of the fifth end 6c1 in the X and Y directions and the rotation axis S was set to 30 mm. The other dimensions were the same as those of Example 2.

[0091] Example 4 The antenna 1 shown in the fourth embodiment was constructed as a model for Example 4. That is, in Example 4, an antenna 1 in which the first plate conductor 2 and the second plate conductor 30 have a circular shape was verified. The diameters of the first plate conductor 2 and the second plate conductor 30 were set to 70 mm. The width dimension in the Y direction of the short-circuiting conductor 6, which is a rectangular plate, was set to 10 mm. The distance in the X direction between the short-circuiting conductor 6 and the rotation axis S was set to 30 mm. The other dimensions were the same as in Example 2.

[0092] Example 5 The antenna 1 shown in the fifth embodiment was constructed as a model for Example 5. Example 5 verified the antenna 1 in Example 4, in which the rotation axis S of the columnar conductor 4 did not coincide with the central axis T of the first plate conductor 2 and the second plate conductor 30. The antenna 1 of Example 5 is similar to the antenna 1 of Example 4, except that the edge 18a of the base end surface 18 of the columnar conductor 4 coincides with the edge 2f1 of the first plate conductor 2.

[0093] Comparative Example 1 The antenna 101 shown below was constructed as a model of Comparative Example 1. Fig. 15 is a perspective view of the antenna 101 according to Comparative Example 1, and Fig. 16 is a cross-sectional view of the antenna 101 taken along the X-Z plane. In Fig. 15, the first plate-like conductor 102 is shown by an imaginary line (two-dot chain line) for ease of understanding. Fig. 16 also shows a cross-section passing through the center of the antenna 101 in the Y direction.

[0094] 15 and 16 , an antenna 101 of Comparative Example 1 is provided on a ground conductor 100. The antenna 101 includes a first plate conductor 102, a second plate conductor 130, a columnar conductor 104, and a short-circuit conductor 106. The first plate conductor 102, the second plate conductor 130, the hole 130 e, the columnar conductor 104, and the short-circuit conductor 106 correspond to the first plate conductor 2, the second plate conductor 30, the hole 30 e, the columnar conductor 4, and the short-circuit conductor 6 in the fourth embodiment, respectively.

[0095] The columnar conductor 104 in Comparative Example 1 is a rod-shaped member with a diameter of 1.3 mm. The width dimension in the Y direction of the short-circuit conductor 106 in Comparative Example 1 is 20 mm. The other dimensions are the same as those of the first plate-shaped conductor 2, the second plate-shaped conductor 30, the columnar conductor 4, and the short-circuit conductor 6 in the fourth embodiment.

[0096] Figure 17 is a diagram showing the frequency characteristics of return loss in Comparative Example 1. As shown in Figure 17, in Comparative Example 1, the return loss is -5 dB or less in the range of approximately 700 to 900 MHz. However, the return loss in other bands is greater than -5 dB. Note that frequency bands in which the return loss is -5 dB or less can be determined to be frequency bands that the antenna can support. In this way, Comparative Example 1 is only compatible with relatively low frequency bands below 1 GHz.

[0097] FIG. 18 is a diagram showing the frequency characteristics of return loss in Example 1. As shown in FIG. 18, in Example 1, the return loss is −5 dB or less in the range of approximately 750 to 900 MHz. Furthermore, the return loss in the frequency band of 1.6 GHz or more is −5 dB or less. Note that in FIG. 17, the return loss in the frequency band from 1.6 GHz to at least 6 GHz is −5 dB or less. Thus, Example 1 is capable of supporting a relatively low frequency band of 1 GHz or less and a frequency band of 1.6 GHz or more. From these results, it can be seen that Example 1 provides an antenna 1 that is compatible with a wider frequency band than Comparative Example 1.

[0098] 19 is a diagram showing the frequency characteristics of return loss in Example 2. As shown in FIG. 19, in Example 2, the return loss is −5 dB or less in the range of approximately 750 to 950 MHz. Furthermore, the return loss in the frequency band of 1.5 GHz or more is −5 dB or less. In Example 2, the frequency band of 1 GHz or less among the supported frequency bands is broadened compared to Example 1. From this result, it can be seen that in Example 2, by adding the second plate-like conductor 30, the relatively low frequency band among the supported frequency bands is broadened.

[0099] FIG. 20 is a diagram showing the frequency characteristics of return loss in Example 3. As shown in FIG. 20, in Example 3, the return loss is −5 dB or less in the range of approximately 700 to 950 MHz. Furthermore, the return loss in the frequency band of 1.5 to 2.3 GHz is −5 dB or less. Furthermore, the return loss in the frequency band of 2.4 GHz or higher is −5 dB or less. In Example 3, the frequency band of 1 GHz or lower among the available frequency bands is broadened compared to Example 2. From these results, it can be seen that in Example 3, the short-circuit conductor 6 curved according to the side surface 20 of the columnar conductor 4 is arranged opposite the side surface 20 at a distance D, thereby broadening the available frequency band in the relatively low frequency band.

[0100] FIG. 21 is a diagram showing the frequency characteristics of return loss in Example 4. As shown in FIG. 21, in Example 4, the return loss is −5 dB or less in the range of approximately 800 to 900 MHz. Furthermore, the return loss in the frequency band of 2.4 to 3.7 GHz is −5 dB or less. Furthermore, the return loss in the frequency band of 5.2 GHz or more is −5 dB or less. In Example 4, the frequency band of 1 GHz or more among the supported frequency bands is narrower than in Examples 1 to 3, but some bands are still supported. From these results, it can be seen that Example 4 is capable of supporting relatively low frequency bands of 1 GHz or less and some frequency bands of 2.4 GHz or more, and an antenna 1 that is compatible with a wider frequency band than Comparative Example 1 is obtained.

[0101] FIG. 22 is a diagram showing the frequency characteristics of return loss in Example 5. As shown in FIG. 22, in Example 5, the return loss is −5 dB or less in the range of approximately 800 to 950 MHz. Furthermore, the return loss in the frequency band of 1.3 GHz or more is −5 dB or less. In this way, Example 5 is capable of supporting a relatively low frequency band of 1 GHz or less and a frequency band of 1.3 GHz or more. From this result, it can be seen that Example 5 provides an antenna 1 that is compatible with a wider frequency band than Comparative Example 1.

[0102] [Others] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the meaning described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0103] REFERENCE SIGNS LIST 1 Antenna 2 First plate-shaped conductor 2a Plate surface 2b First end 2b1 Short side 2c Second end 2c1 Short side 2d1 Long side 2e Hole 2f1 Edge 2f2 Edge 4 Columnar conductor 6 Short-circuiting conductor 6a Conductor body 6a1 Screw head 6b Spacer 6c Main body member 6c1 Fifth end 6c2 Sixth end 6c3 First surface 6c4 Edge 6c5 Contour line 7 Nut 8 Washer 9 Washer 10 Ground conductor 10a First surface 10b Second surface 10d Hole 11 Hole 12 Pin 13 Connector 13a Insulating member 13a1 Through hole 13a2 End surface 13b Main body 16 Tip 17 Tip hole 18 Base end surface 18a Edge 19 End surface 19a Opening edge 19b Contour line 20 Side surface 20a Contour line 21 Hole portion 21a Small diameter portion 21b Large diameter portion 22 First divided body 22a Contact surface 24 Second divided body 24a Contact surface 24a1 Projection 30 Second plate-shaped conductor 30b Third end portion 30b1 Short side portion 30c Fourth end portion 30c1 Short side portion 30d1 Long side portion 30d2 End edge 30e Hole portion 32 Boundary portion 33 End plane portion 36 First main body portion 36a Large diameter portion 36b Small diameter portion 38 Second main body portion 40 Plate member 42 Interposition portion 42a Hole portion 100 Ground conductor 101 Antenna 102 First plate-shaped conductor 104 Pillar-shaped conductor 106 Short-circuit conductor 130 Second plate-shaped conductor 130e Hole C Contour curve D Distance D1 Distance D2 Distance S Rotation axis T Central axis

Claims

1. A first plate-shaped conductor; a columnar conductor provided so as to protrude from a plate surface of the first plate conductor, The tip of the columnar conductor has a power supply point, A cross-sectional area of ​​the columnar conductor taken along the plate surface is greater than an area of ​​an end face of the tip portion. antenna.

2. The columnar conductor has a tapered side surface that tapers from the first plate conductor side toward the tip end side.

2. The antenna of claim 1.

3. The side surface is a convex curved surface.

3. The antenna of claim 2.

4. the shape of the side surface is a shape of a side surface of a rotating body having a rotation axis that is a straight line perpendicular to the plate surface, A contour curve of the side surface in a cross section of the cylindrical conductor taken along a plane including the rotation axis satisfies the following formula when the rotation axis is defined as a y-axis and a straight line at the tip portion perpendicular to the rotation axis is defined as an x-axis:

4. The antenna of claim 3. y = ax Ｐ Here, x≧0, a>0, and P≧1.

5. The columnar conductor has a stepped side surface that gradually widens from the tip end side toward the first plate conductor side.

2. The antenna of claim 1.

6. The first plate-shaped conductor is strip-shaped.

2. The antenna of claim 1.

7. The columnar conductor is provided on a first end side in a longitudinal direction of the first plate-shaped conductor.

7. The antenna of claim 6.

8. The width dimension of the first plate-shaped conductor is equal to the width dimension of a cross section of the columnar conductor taken along the plate surface.

8. An antenna as claimed in claim 6 or claim 7.

9. A short side of the first plate-shaped conductor on a first end side in a longitudinal direction has a shape that follows a contour shape of a cross section of the columnar conductor taken along the plate surface.

9. The antenna of claim 8.

10. The columnar conductor is provided at a position on the plate surface that is shifted from the center of the first plate conductor.

2. The antenna of claim 1.

11. The center of the first plate-shaped conductor is the center of gravity of a contour shape when the first plate-shaped conductor is viewed in a plane, or the center of a circumscribing circle of the contour shape.

11. The antenna of claim 10.

12. a short-circuit conductor provided on the plate surface to ground the first plate-shaped conductor; 2. The antenna of claim 1.

13. The short-circuiting conductor has a plate shape curved in accordance with the side surface of the columnar conductor, and is disposed opposite the side surface of the columnar conductor at a predetermined interval.

13. The antenna of claim 12.

14. a second plate-shaped conductor provided to protrude from a side surface of the columnar conductor and disposed opposite the first plate-shaped conductor on the plate surface side of the first plate-shaped conductor; 2. The antenna of claim 1.