JP2015103912A - Biconical antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biconical antenna in which a propagation property is improved by reducing directivity in a zenith direction and turning energy for a reduced component in a horizontal direction.SOLUTION: A biconical antenna includes: a cylindrical first antenna element including a conical first cone part at one end side in a center axis direction; and a cylindrical second antenna element including a conical second cone part, opposing the first cone part, at one end side in a center axis direction. Power is supplied by an apex of the first cone part and an apex of the second cone part. The biconical antenna further includes: a dielectric-made plate-like member disposed at the another end side in the center axis direction of the first antenna element or at the another end side in the center axis direction of the second antenna element; and a conductor-made cylindrical member disposed at the another end side in the center axis direction of the first antenna element or at the another end side in the center axis direction of the second antenna element and held at a floating potential, via the dielectric.

Description

  The present invention relates to a biconical antenna.

  The wireless camera system is a system that can shoot music programs and sports programs on television stations without being affected by cables. In such a wireless camera system, a signal photographed by a camera is generally transmitted using radio waves using the 1-2 GHz or 6-7 GHz band, and various antennas are used for signal transmission. . (For example, see Patent Documents 1, 2, and 3).

JP 2008-92396 A Japanese Patent No. 4504933 JP 2000-174540 A

However, the antenna as described above has the following problems.
(A) When a wireless camera is used in the millimeter wave band, it is advantageous to have non-directionality in a horizontal plane and not directivity in a zenith direction and a direct downward direction in a vertical plane. However, since the antennas of Patent Documents 1 and 3 have a large directivity in the zenith direction, the propagation characteristics deteriorate.
(C) When a transmission antenna used in the millimeter wave band is manufactured using a linear antenna, the loss increases depending on the length of the line, and the characteristics of the antenna disclosed in Patent Document 2 deteriorate.

  Therefore, an object of the present invention is to provide a biconical antenna with improved propagation characteristics by reducing directivity in the zenith direction and directing the corresponding energy in the horizontal direction.

  The biconical antenna according to one aspect of the present invention includes a cylindrical first antenna element having a conical first cone portion on one end side in the central axis direction, and a first cone portion on one end side in the central axis direction. A biconical antenna including a cylindrical second antenna element having a conical second cone portion opposed thereto, and fed by a top portion of the first cone portion and a top portion of the second cone portion, Via a dielectric plate-like member disposed on the other end side in the central axis direction of the first antenna element or on the other end side in the central axis direction of the second antenna element, and the dielectric A conductive cylindrical member disposed on the other end side in the central axis direction of the first antenna element or on the other end side in the central axis direction of the second antenna element and held at a floating potential; Including.

  According to the present invention, it is possible to provide a biconical antenna with improved propagation characteristics by reducing directivity in the zenith direction and directing the corresponding energy in the horizontal direction.

1 is a diagram illustrating a biconical antenna according to a first embodiment. It is a figure which shows the biconical antenna 10 for a comparison. 3 is a diagram showing a radiation pattern of the biconical antenna 100 according to Embodiment 1. FIG. It is a figure which shows the radiation pattern of the biconical antenna 10 for a comparison. 6 is a diagram showing a biconical antenna according to a second embodiment. FIG. It is a figure which shows the radiation pattern of the biconical antenna 200 of Embodiment 2. FIG. FIG. 10 is a diagram illustrating a biconical antenna according to a third embodiment. It is a figure which shows the radiation pattern of the biconical antenna 300 of Embodiment 3. FIG.

  Embodiments to which the biconical antenna of the present invention is applied will be described below.

<Embodiment 1>
1A and 1B are diagrams showing a biconical antenna according to a first embodiment, where FIG. 1A is a perspective view and FIG. 1B is a side view showing a state where a cover 150 is removed. In FIG. 1, an XYZ coordinate system, which is an orthogonal coordinate system, is defined as shown.

  The biconical antenna 100 includes antenna elements 110 and 120, a dielectric 130, a metal plate 140, and a cover 150.

  The antenna elements 110 and 120, the dielectric 130, and the metal plate 140 are held by the cover 150 shown in FIG. 1A so that the positional relationship shown in FIG. The cover 150 is preferably made of a material having a small relative dielectric constant and a small tan δ (dielectric loss). For example, the cover 150 may be made of Teflon.

  FIG. 1B shows a coaxial waveguide converter 160 and a waveguide 180 and a transmission circuit (Tx) 190 provided on the negative side of the antenna element 110 in the Z-axis direction.

  The antenna element 110 is a cylindrical metal member, and is arranged so that the central axis is parallel to the Z axis in FIGS. 1 (A) and 1 (B). The antenna element 110 has a cone portion 111 on the Z axis positive direction side. The antenna element 110 has a shape in which a conical cone portion 111 is placed on the surface of the cylindrical member 112 on the positive side in the Z-axis direction. The diameter of the bottom surface of the cone of the cone part 111 is smaller than the diameter of the cylindrical member 112 of the antenna element 110.

  The antenna element 110 has an opening 111 </ b> A at the top of the cone 111. The opening 111 </ b> A is located on the central axis of the antenna element 110. Further, the cone portion 111 is formed with a through hole 111B having an opening 111A as an upper end. The through hole 111 </ b> B communicates with a hole portion 112 </ b> A formed on the central axis of the cylindrical member 112. In FIG. 1, for convenience of explanation, the opening 111 </ b> A is shown to be larger than the ratio of the actual size of the opening 111 </ b> A to the cone 111, but the opening 111 </ b> A is positioned at the top of the cone 111. To do.

  Inside the cylindrical member 112, a hole 112A and a rectangular waveguide 170 are formed. The hole 112 </ b> A extends from the upper part of the cylindrical member 112 to approximately the center in the thickness direction of the cylindrical member 112. The upper end of the hole 112A communicates with the through hole 111B, and the lower end communicates with the rectangular waveguide 170. A coaxial cable 161 is disposed inside the hole 112A and the through hole 111B. Further, the rectangular waveguide 170 has an upper end 170A communicating with the hole 112A, and is bent at right angles to the L shape three times and extends to the lower end 170B. The central axis at the lower end 170B of the rectangular waveguide 170 coincides with the central axis of the cylindrical member 112. The central axis at the lower end 170B of the rectangular waveguide 170 may be offset with respect to the central axis of the cylindrical member 112.

  The coaxial waveguide converter 160 is configured by a coaxial cable 161, and the upper end 161 </ b> A <b> 1 of the core wire 161 </ b> A of the coaxial cable 161 is connected to the apex of the cone portion 121 of the antenna element 120. The core wire 161A extends from the opening 111A of the cone portion 111 of the antenna element 110 in the positive direction of the Z axis.

  The outer peripheral surface of the shield (coating) of the coaxial cable 161 is connected to the inner wall surfaces of the through hole 111B and the hole portion 112A. The top part of the cone part 111 and the top part of the cone part 121 constitute a feeding part of the biconical antenna 100. The shield of the coaxial cable 161 is disposed between the opening 111A and the lower end 112A1 of the hole 112A so as to contact the inner wall surface of the through hole 111B and the hole 112A. An insulating portion that insulates the shield of the coaxial cable 161 from the core wire 161A is provided between the core wire 161A and the shield between the opening 111A and the lower end 112A1 of the hole portion 112A. An insulating portion that insulates the shield of the coaxial cable 161 from the core wire 161A is provided in a cylindrical space between the core wire 161A and the shield. The portion of the core wire 161A located above the opening 111A is bare. Further, the lower end 161A2 of the core wire 161A extends below the lower end 112A1 of the hole 112A and is connected to the inner wall surface of the rectangular waveguide 170. Note that the lower end 161A2 of the core wire 161A may not reach the inner wall surface of the rectangular waveguide 170. The core wire 161A is also exposed below the lower end 112A1 of the hole 112A. The antenna element 110 may be made of a metal such as aluminum, brass, or copper.

  The antenna element 120 is a cylindrical metal member, and is arranged so that the central axis is parallel to the Z axis in FIGS. 1 (A) and 1 (B). The antenna element 120 has a cone portion 121 on the Z-axis negative direction side. The antenna element 120 has a shape in which a conical cone portion 121 is connected to the surface of the cylindrical member 122 on the Z axis negative direction side. The diameter of the bottom surface of the cone of the cone portion 121 (the surface located in the positive Z-axis direction in FIG. 1) is smaller than the diameter of the cylindrical member 122 of the antenna element 120, and the diameter of the bottom surface of the cone portion 111 of the antenna element 110 is smaller. Equal to diameter.

  The cone part 121 has the same shape as the cone part 111 and is opposed in the Z-axis direction. A core wire 161A is connected to the top portion of the cone portion 121 (the top portion facing the negative Z-axis direction in FIG. 1).

  The diameter of the cylindrical member 122 of the antenna element 120 is equal to the diameter of the cylindrical member 112 of the antenna element 110 and is arranged so that the central axes coincide.

  The antenna element 120 may be made of a metal such as aluminum, brass, or copper, and is preferably made of the same metal material as the antenna element 110.

  The dielectric 130 has a disk shape and is disposed on the surface of the cylindrical member 122 on the Z axis positive direction side. The dielectric 130 may be made of resin, for example. The diameter of the dielectric 130 is equal to the diameter of the cylindrical member 122 of the antenna element 120, and is arranged so that the central axes coincide.

  The metal plate 140 has a disk shape and is disposed on the surface of the dielectric 130 on the Z axis positive direction side. The diameter of the dielectric 130 is equal to the diameter of the cylindrical member 122 of the antenna element 120, and is arranged so that the central axes coincide.

  Note that the metal plate 140 may be made of a metal such as aluminum, brass, or copper, and is preferably made of the same metal material as the antenna elements 110 and 120.

  The rectangular waveguide 170 has an upper end 170A communicating with the hole 112A, and is bent three times into an L shape at a right angle and extends to the lower end 170B. The central axis at the lower end 170B of the rectangular waveguide 170 coincides with the central axis of the cylindrical member 112. The central axis at the lower end 170B of the rectangular waveguide 170 may be offset with respect to the central axis of the cylindrical member 112.

  A radio wave propagates to the rectangular waveguide 170 from a portion where the core wire 161 </ b> A is exposed inside the rectangular waveguide 170. The rectangular waveguide 170 is bent in an L shape between the upper end 170A and the lower end 170B, and radio waves propagate between the upper end 170A and the lower end 170B. The cross section perpendicular to the central axis extending in an L shape from the upper end 170A to the lower end 170B is rectangular. A lower end 170 </ b> B of the rectangular waveguide 170 communicates with the through hole 180 </ b> A of the waveguide 180. The rectangular waveguide 170 propagates radio waves transmitted from the transmission circuit 190 via the waveguide unit 180 to the coaxial cable 161.

  The waveguide section 180 has an upper end connected to the lower end 170B of the rectangular waveguide 170 and a lower end connected directly to the transmission circuit 190. The waveguide section 180 is a tubular member and has a through hole 180A. A cross section perpendicular to the central axis (longitudinal axis) of the through hole 180A is a rectangle. The cross-sectional shape of the through hole 180 </ b> A is in communication with the cross-sectional shape of the rectangular waveguide 170 in the same level. The waveguide portion 180 is formed of a metal such as aluminum, brass, or copper, for example.

  When radio waves are output from the transmission circuit 190 in a state where the coaxial waveguide converter 160 (coaxial cable 161), the waveguide 180, and the transmission circuit 190 are connected to the biconical antenna 100 as described above, Through the waveguide 180, the rectangular waveguide 170, and the coaxial waveguide converter 160, the cones 111 and 121 radiate so that the plane of polarization extends mainly in the XY plane on the ZY plane.

  Here, the radiation pattern of the biconical antenna 100 of the first embodiment will be described using the comparative biconical antenna 10.

  FIG. 2 is a diagram showing a comparative biconical antenna 10. The comparative biconical antenna 10 uses the antenna element 20 instead of the antenna element 120, the dielectric 130, and the metal plate 140 of the biconical antenna 100 of the first embodiment.

  The antenna element 20 is a cylindrical metal member, and is arranged so that the central axis is parallel to the Z axis in FIG. The antenna element 20 has a cone portion 21 on the Z axis negative direction side. The antenna element 20 has a shape in which a conical cone portion 21 is connected to the surface of the cylindrical member 22 on the negative side in the Z-axis direction.

  The antenna element 20 has a configuration in which the cylindrical member 22 of the antenna element 120 of the first embodiment is thickened. The dielectric 130 and the metal plate 140 are not disposed on the antenna element 120.

  The cone part 21 has the same shape as the cone part 111 and is opposed in the Z-axis direction. A core wire 161 is connected to the top portion of the cone portion 21 (the top portion facing the negative Z-axis direction in FIG. 2).

  In FIG. 2, the cover 150 is omitted. FIG. 2 shows a state where the coaxial waveguide conversion unit 160, the waveguide 180, and the transmission circuit 190 are connected to the biconical antenna 10.

  Next, radiation patterns of the biconical antenna 100 of the first embodiment and the comparative biconical antenna 10 will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a diagram showing a radiation pattern of the biconical antenna 100 according to the first embodiment. FIG. 3A shows a radiation pattern in a horizontal plane, and FIG. 3B shows a radiation pattern in a vertical plane.

  FIG. 4 is a diagram showing a radiation pattern of the comparative biconical antenna 10. 4A shows a radiation pattern in a horizontal plane, and FIG. 4B shows a radiation pattern in a vertical plane.

  Comparing FIG. 3 and FIG. 4, in FIG. 4 (B), the amplitude value is particularly large in the vertical direction (0 degree) in the vertical plane, whereas in FIG. 3 (B), the vertical value is particularly high in the vertical plane. It can be seen that the amplitude value on the (0 degree) side is reduced. That is, it can be seen that the biconical antenna 100 according to the first embodiment has a lower radio wave emission vertically than the comparative biconical antenna 10.

  Further, comparing FIG. 3A and FIG. 4A, it can be seen that radio waves are radiated equally in the horizontal direction. The omnidirectionality can be maintained on the horizontal plane.

From the above, it can be seen that the biconical antenna 100 according to the first embodiment has reduced radio wave radiation vertically upward compared to the comparative biconical antenna 10. In addition, comparing FIG. 3 (B) and FIG. 4 (B), FIG. 3 (B
), The radiation in the 65, 295, 35, and 325 degrees directions is increased, and the radiation pattern in the horizontal direction is considered to be improved.

  As described above, the radio wave radiation upward is reduced because the dielectric 130 and the metal plate 140 are arranged on the antenna element 120 in the biconical antenna 100 of the first embodiment. This is considered to be due to the fact that the element 120 and the metal plate 140 are coupled to each other, and it is difficult for current to flow in the Z axis positive direction surface of the antenna element 120.

  For this reason, in the biconical antenna 100 of the first embodiment, as shown in FIG. 3B, the radiation upward in the vertical direction is reduced, and the antenna gain in other directions can be increased. .

<Embodiment 2>
FIG. 5 is a diagram illustrating the biconical antenna according to the second embodiment, and is a side view illustrating a state in which the cover 150 is removed as in FIG. In FIG. 5, an XYZ coordinate system, which is an orthogonal coordinate system, is defined as shown.

  The biconical antenna 200 includes antenna elements 210 and 20, a dielectric 230, and a metal plate 240.

  In the biconical antenna 200 of the second embodiment, a dielectric 230 and a metal plate 240 similar to the dielectric 130 and the metal plate 140 are disposed below the antenna element 110 of the first embodiment, and the antenna element 120 and the dielectric The body 130 and the metal plate 140 are replaced with the antenna element 20 of the comparative biconical antenna 10.

  For this reason, the same code | symbol is attached | subjected to the component similar to the component shown in FIG.1 and FIG.2, and the description is abbreviate | omitted.

  Further, FIG. 5 shows the coaxial waveguide converter 160, a waveguide 180 and a transmission circuit (Tx) 190 provided on the Z-axis negative direction side of the metal plate 240.

  The antenna element 210 is a cylindrical metal member, and is arranged so that the central axis is parallel to the Z axis in FIG. The antenna element 210 has a cone portion 211 on the Z axis positive direction side. The antenna element 210 has a shape in which a conical cone portion 211 is placed on the surface of the cylindrical member 212 on the positive side in the Z-axis direction. The diameter of the bottom surface of the cone of the cone part 211 is smaller than the diameter of the cylindrical member 212 of the antenna element 210. The antenna element 210 is thinner than the antenna element 110 of the first embodiment.

  The antenna element 210 has an opening 211 </ b> A at the top of the cone portion 211. The opening 211 </ b> A is located on the central axis of the antenna element 210. Further, the cone portion 211 is formed with a through hole 211B having an opening portion 211A as an upper end. The through hole 211 </ b> B communicates with a hole 212 </ b> A that passes through the central axis of the cylindrical member 212. The hole 212A is formed from the opening 211A to the upper end 170A of the rectangular waveguide 170 formed inside the metal plate 240 through the dielectric 230. A coaxial waveguide converter 160 (coaxial cable 161) is disposed inside the hole 212A while being insulated from the antenna element 210.

  The core wire 161 </ b> A of the coaxial cable 161 extends from the opening 211 </ b> A of the cone portion 211 of the antenna element 210 toward the positive direction of the Z axis.

  The upper end 161A1 of the core wire 161A is connected to the top of the cone portion 21 of the antenna element 20. Further, the shield wire is connected to the inner wall surface of the hole 212A. The top part of the cone part 211 and the top part of the cone part 21 constitute a power feeding part of the biconical antenna 200.

  The antenna element 210 may be made of a metal such as aluminum, brass, or copper.

  The dielectric 230 has a disk shape and is disposed on the surface of the cylindrical member 212 on the Z axis negative direction side. The dielectric 230 may be made of resin, for example. The diameter of the dielectric 230 is equal to the diameter of the cylindrical member 212 of the antenna element 210 and is arranged so that the central axes coincide. A hole 212A is formed on the central axis of the dielectric 230, and a coaxial cable 161 is inserted therein.

  The metal plate 240 has a disk shape, and is disposed on the surface of the dielectric 230 on the Z axis negative direction side. The diameter of the dielectric 230 is equal to the diameter of the cylindrical member 212 of the antenna element 210 and is arranged so that the central axes coincide. On the central axis of the dielectric 230, a lower end 170B side of the hole 212A and a rectangular waveguide 170 are formed.

  The metal plate 240 may be made of a metal such as aluminum, brass, or copper, and is preferably made of the same metal material as the antenna elements 210 and 20.

  In addition to the antenna element 210, the hole 212A is formed inside the dielectric 230 and the metal plate 240. The lower end 212A1 of the hole portion 212A communicates with the upper end 170A of the rectangular waveguide 170.

  The antenna element 210, the dielectric 230, and the metal plate 240 of the biconical antenna 200 of the second embodiment are provided with the dielectric 230 in the intermediate portion in the Z-axis direction of the antenna element 110 of the biconical antenna 100 of the first embodiment. It is the inserted configuration. The hole 212 </ b> A is formed over the antenna element 210, the dielectric 230, and the metal plate 240, and the rectangular waveguide 170 is formed inside the metal plate 240.

  When a radio wave is output from the transmission circuit 190 in a state where the waveguide 180 and the transmission circuit 190 are connected to the biconical antenna 200 as described above, the radio wave passes through the waveguide 180 and the coaxial waveguide converter 160. The cones 211 and 21 radiate so that the plane of polarization extends in the XY plane mainly in the XY plane.

  FIG. 6 is a diagram showing a radiation pattern of the biconical antenna 200 of the second embodiment. FIG. 6A shows a radiation pattern in a horizontal plane, and FIG. 6B shows a radiation pattern in a vertical plane.

  As shown in FIG. 6A, similarly to the radiation pattern of the biconical antenna 10 of the first embodiment shown in FIG. 3, radio waves are radiated evenly in the horizontal direction, and omnidirectionality is obtained in the horizontal plane. Maintained.

  Further, as shown in FIG. 6B, compared to the radiation pattern in the vertical plane of the comparative biconical antenna 10 (see FIG. 4B), the vertical upper side (0 degree) side in the vertical plane. It can be seen that the amplitude value vertically downward (180 degrees) is reduced. That is, it can be seen that the biconical antenna 200 according to the second embodiment has a lower radio wave emission vertically upward and downward than the comparative biconical antenna 10.

  From the above, it can be seen that the biconical antenna 200 according to the second embodiment has reduced radio wave radiation vertically upward and downward compared to the comparative biconical antenna 10. Further, comparing FIG. 6B and FIG. 4B, the biconical antenna 200 of the second embodiment is 65 degrees in FIG. 6B by the amount of radiation of the radio wave vertically upward. The radiation pattern in the horizontal direction is considered to be improved by increasing the radiation in the directions of 295 degrees, 35 degrees and 325 degrees.

  As described above, the radiation of the radio wave vertically upward and downward is reduced because the dielectric 230 and the metal plate 240 are disposed under the antenna element 210 in the biconical antenna 200 of the second embodiment. As a result, the antenna element 210 and the metal plate 240 are combined, and current flows through the Z-axis positive direction surface and the Z-axis negative direction surface of the antenna element 210, thereby making it difficult for current to flow through the Z-axis negative direction surface of 240. It is thought to be due to.

  For this reason, in the biconical antenna 200 according to the second embodiment, as shown in FIG. 6B, radiation vertically upward and vertically downward is reduced, and the antenna gain in other directions can be increased. it is conceivable that.

<Embodiment 3>
FIG. 7 is a diagram illustrating the biconical antenna according to the third embodiment, and is a side view illustrating a state in which the cover 150 is removed as in FIG. In FIG. 7, an XYZ coordinate system, which is an orthogonal coordinate system, is defined as shown.

  The biconical antenna 300 includes antenna elements 210 and 120, dielectrics 130 and 230, and metal plates 140 and 240.

  The biconical antenna 300 according to the third embodiment includes the antenna element 120, the dielectric 130, and the metal plate 140 (see FIG. 1) according to the first embodiment, and the antenna element 210, the dielectric 230, and the metal according to the second embodiment. It has the structure which combined the board 240 (refer FIG. 5).

  For this reason, the same code | symbol is attached | subjected to the component similar to the component shown in FIG.1 and FIG.5, and the description is abbreviate | omitted.

  FIG. 7 shows a waveguide 180 and a transmission circuit (Tx) 190 provided on the negative side of the metal plate 240 in the Z-axis direction.

  FIG. 8 is a diagram illustrating a radiation pattern of the biconical antenna 300 according to the third embodiment. FIG. 8A shows a radiation pattern in a horizontal plane, and FIG. 8B shows a radiation pattern in a vertical plane.

  As shown in FIG. 8A, similarly to the radiation pattern of the biconical antenna 10 of the first embodiment shown in FIG. 3, radio waves are radiated uniformly in the horizontal direction, and omnidirectionality is obtained in the horizontal plane. Maintained.

  Further, as shown in FIG. 8B, compared to the radiation pattern in the vertical plane of the comparative biconical antenna 10 (see FIG. 4B), in particular, vertically upward (0 degree) in the vertical plane. It can be seen that the amplitude value on the side is reduced. That is, it can be seen that the biconical antenna 300 according to the third embodiment has a significantly reduced radio wave emission vertically upward than the comparative biconical antenna 10.

  From the above, it can be seen that the biconical antenna 300 according to the third embodiment has reduced radio wave radiation vertically upward compared to the comparative biconical antenna 10. Further, as shown in FIG. 8B, the biconical antenna 300 according to the third embodiment has directions of 65 degrees, 295 degrees, 35 degrees, and 325 degrees corresponding to the reduction of radio wave radiation upward. It is considered that the radiation pattern in the horizontal direction has been improved.

  In this way, the radio wave radiation upward in the vertical direction is greatly reduced because the dielectric 130 and the metal plate 140 are disposed on the antenna element 120 in the biconical antenna 300 of the third embodiment, By disposing the dielectric 230 and the metal plate 240 under the antenna element 210, current flows in the Z-axis positive direction surface of the antenna elements 120 and 240, and in the Z-axis negative direction surface of the antenna elements 120 and 240. This is thought to be due to the fact that current hardly flows in the Z-axis positive direction surface and the 240-Z negative direction surface.

  For this reason, in the biconical antenna 300 of the third embodiment, as shown in FIG. 8B, the radiation upward in the vertical direction is significantly reduced, and the antenna gain in other directions can be increased. Conceivable.

  The biconical antenna of the exemplary embodiment of the present invention has been described above, but the present invention is not limited to the specifically disclosed embodiment, and does not depart from the scope of the claims. Various modifications and changes are possible.

100, 200, 300 Biconical antenna 110, 120, 210, 20 Antenna element 130, 230 Dielectric 140, 240 Metal plate 150 Cover 160 Coaxial waveguide conversion section 170 Rectangular waveguide 180 Waveguide 190 Transmission circuit

Claims (5)

A cylindrical first antenna element having a conical first cone portion on one end side in the central axis direction;
A cylindrical second antenna element having a conical second cone portion opposed to the first cone portion on one end side in the central axis direction, and a top portion of the first cone portion and the second cone portion A biconical antenna fed with the top of the
A dielectric plate-like member disposed on the other end side in the central axis direction of the first antenna element or on the other end side in the central axis direction of the second antenna element;
Via the dielectric, the conductor is disposed at the other end side in the central axis direction of the first antenna element or the other end side in the central axis direction of the second antenna element, and is held at a floating potential. A biconical antenna further comprising: a cylindrical member.   The biconical antenna according to claim 1, wherein a central axis of the first antenna element coincides with a central axis of the second antenna element.   The biconical antenna according to claim 2, wherein a central axis of the cylindrical member coincides with a central axis of the first antenna element and a central axis of the second antenna element.   The said plate-shaped member is disk shape, and has the central axis which corresponds with the central axis of the said cylindrical member, the central axis of the said 1st antenna element, and the central axis of the said 2nd antenna element. Biconical antenna described.   The biconical antenna according to claim 4, wherein dimensions of the first antenna element, the second antenna element, the cylindrical member, and the plate-like member in the system direction are equal.

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