Polarization-sharing antenna

Abstract

This provides a small, lightweight, and polarized shared antenna that achieves high antenna gain while suppressing unnecessary radio wave radiation to the rear. [Solution] The polarization-sharing antenna comprises a feeding element having an element body made of a loop-shaped conductor and four first feeding lines made of conductors extending laterally toward the loop central axis from four locations on the element body at equal angular intervals in the circumferential direction; a ground plate positioned opposite the back of the feeding element at a predetermined separation distance; and four second feeding lines made of conductors extending vertically toward the ground plate from the loop central axis side end of each of the four first feeding lines in the feeding element. Of the four second feeding lines, any two second feeding lines that are adjacent to each other in the circumferential direction around the loop central axis are connected to the ground plate, and the other two second feeding lines are each connected to the signal lines of the two polarizations.

Description

Technical Field

[0001] The present invention relates to a polarization sharing antenna shared by polarizations orthogonal to each other.

Background Art

[0002] Patent Document 1 describes a polarization sharing patch antenna that includes a radiation patch, a ground plate, a dielectric layer between the radiation patch and the ground plate, and a first polarization port and a second polarization port arranged on the radiation patch, and is shared by polarizations orthogonal to each other (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a radio device mounted on an aircraft such as a HAPS (High Altitude Platform Station) that can stay or fly at a predetermined altitude or a UAV (Unmanned Aerial Vehicle) such as a drone, a polarization sharing antenna is used in consideration of the rotation and inclination of the aircraft. In such a radio device mounted on an aircraft in the sky, there is a need for a small and lightweight polarization sharing antenna that can achieve a high antenna gain while suppressing unnecessary radio wave radiation to the rear.

Means for Solving the Problems

[0005] An antenna according to one aspect of the present invention is a polarization-sharing antenna used for two mutually orthogonal polarizations. This polarization-sharing antenna comprises a loop-structured feeding element having an element body made of a loop-shaped conductor and four first feeding lines made of conductors extending laterally toward the loop central axis from four locations on the element body at equiangled intervals in the circumferential direction; a ground plate positioned opposite the back of the feeding element at a predetermined separation distance; and four second feeding lines made of conductors extending longitudinally toward the ground plate from the loop central axis side end of each of the four first feeding lines in the feeding element. Of the four second feeding lines, any two second feeding lines adjacent to each other in the circumferential direction around the loop central axis are connected to the ground plate, and the other two second feeding lines are each connected to the signal lines of the two polarizations.

[0006] In the polarization-sharing antenna, the ground plate may have one or more openings. Here, the openings of the ground plate may be formed in a portion facing all or part of the opening of the feeding element.

[0007] The polarization-sharing antenna may further include a passive element made of a conductor, which is positioned opposite the feeding element at a predetermined separation distance.

[0008] The polarization-sharing antenna may further include a protective member that covers and protects the feeding element, the second feeding line, and the passive element. Here, the protective member may have one or more openings. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a small, lightweight polarization-sharing antenna that can achieve high antenna gain while suppressing unnecessary radio wave radiation to the rear. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a plan view showing an example of a polarization-sharing antenna according to an embodiment. [Figure 2] Figure 2 is a perspective view showing an example of a polarization-sharing antenna according to an embodiment. [Figure 3] Figure 3 is an explanatory diagram showing an example of the current vector distribution in the feeding element of the loop structure of the polarization-sharing antenna shown in Figure 1. [Figure 4] Figure 4 is an explanatory diagram showing an example of the current vector distribution in the second feed line of the vertical structure of the polarization-sharing antenna shown in Figure 2. [Figure 5] Figure 5 is a perspective view showing an example of a polarization-sharing antenna having a ground plate without holes according to an embodiment. [Figure 6] Figure 6 is an explanatory diagram showing an example of the electric field vector in the longitudinal section of the polarization-sharing antenna with a ground plate without holes, as shown in Figure 5. [Figure 7] Figure 7 is a perspective view showing an example of a polarization-sharing antenna having a perforated ground plate according to an embodiment. [Figure 8] Figure 8 is an explanatory diagram showing an example of the electric field vector in a longitudinal section of a polarization-sharing antenna having a perforated ground plate as shown in Figure 7. [Figure 9] Figure 9 is an explanatory diagram showing an example of the current vector distribution in a polarization-sharing antenna with a ground plate without holes, as shown in Figure 5. [Figure 10] Figure 10 is an explanatory diagram showing an example of the current vector distribution in a polarization-sharing antenna having a perforated ground plate as shown in Figure 7. [Figure 11] Figure 11 is a front view showing an example of the external appearance of a polarization-sharing antenna according to an embodiment. [Figure 12] Figure 12 is a right side view of the polarization-sharing antenna shown in Figure 11. [Figure 13] Figure 13 is a rear view of the polarization-sharing antenna shown in Figure 11. [Figure 14] Figure 14 is an exploded perspective view of the polarization-sharing antenna shown in Figure 11. [Figure 15] Figure 15 is a longitudinal cross-sectional view of the polarization-sharing antenna shown in Figure 11. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing only schematically shows the shape, size, and positional relationship to such an extent that the content of the present invention can be understood. Therefore, the present invention is not limited only to the shape, size, and positional relationship illustrated in each drawing. Also, the numerical values exemplified hereinafter are merely preferred examples of the present invention. Therefore, the present invention is not limited to the exemplified numerical values.

[0012] The antenna according to the embodiment described in this document is a polarization sharing antenna (polarization sharing loop antenna) shared by two mutually orthogonal polarizations (for example, horizontal polarization and vertical polarization). The polarization sharing antenna of this embodiment includes a feeding element having a loop structure and a ground plane having a structure without holes or a structure with holes, and thus can realize a small-sized and lightweight polarization sharing antenna that suppresses unnecessary radio wave radiation to the back while achieving a high antenna gain. In particular, the polarization sharing antenna of this embodiment is suitable for a wireless device mounted on an aircraft such as a HAPS that can stay or fly at a predetermined altitude or a UAV such as a drone.

[0013] FIG. 1 and FIG. 2 are a plan view and a perspective view respectively showing an example of the polarization sharing antenna 10 according to the embodiment. The polarization sharing antenna 10 may be a transceiver antenna, or may be a transmitting antenna or a receiving antenna. The radio wave to be transmitted or received by the polarization sharing antenna 10 is, for example, a microwave, millimeter wave, or sub-millimeter wave of 300 MHz or higher.

[0014] In FIGS. 1 and 2, the polarization sharing antenna (hereinafter also simply referred to as "antenna") 10 includes a feeding element 100 and a ground plane 120. The feeding element 100 has an element body 110 made of a conductor having a loop shape, and four first feeding lines 111, 112, 113, 114 made of a conductor such as metal. The feeding element 100 has a four-fold rotationally symmetric loop structure centered on the loop central axis A in the z-axis direction in the figure.

[0015] The element body 110 is, for example, a hollow disk arranged parallel to the illustrated x-y plane and having an opening 101 inside. Note that the loop shape of the element body 110 may be any shape, for example, the circular shape shown in the figure. The loop shape of the element body 110 may be an ellipse, a triangle, a quadrilateral, a polygon with five or more sides. The perimeter (loop length) of the element body 110 may be the length of one wavelength (1λ) or approximately one wavelength of the target radio wave. Here, "λ" is the wavelength of the target radio wave in free space (the same applies hereinafter). The element body 110 may be formed of a wire, a plate, a tube, etc. made of a conductor such as metal. The cross-section of the element body 110 may be any shape, for example, a quadrilateral. The cross-section of the element body 110 may be a circle, an ellipse, a triangle, a polygon with five or more sides.

[0016] The first feeding lines 111, 112, 113, 114 are feeding lines of a lateral structure that extend in the lateral direction (the x direction and the y direction in the figure) from four locations at equal angular intervals (90 degrees or approximately 90 degrees) in the circumferential direction of the element body 110 toward the loop central axis A. The first feeding lines 111, 112, 113, 114 may be formed of a wire, a plate, a tube, etc. made of a conductor such as metal. The cross-section of the first feeding lines 111, 112, 113, 114 may be any shape, for example, a quadrilateral. The cross-section of the first feeding lines 111, 112, 113, 114 may be a circle, an ellipse, a triangle, a polygon with five or more sides.

[0017] The element body 110 and the first feeding lines 111, 112, 113, 114 may be integrally formed of the same member, for example, or the element body 110 and the first feeding lines 111, 112, 113, 114 may be formed as separate members and then joined at four locations at equal angular intervals (90 degrees or approximately 90 degrees) in the circumferential direction of the element body 110.

[0018] The ground plate 120 is positioned opposite the back of the power supply element 100 at a predetermined separation distance. The separation distance (spacing) between the ground plate 120 and the power supply element 100 is, for example, 0.06λ or approximately 0.06λ. The ground plate 120 functions as a reflecting element (reflector) that reflects the target radio waves in the directional direction (front direction) where the power supply element 100 is located. The ground plate 120 is positioned parallel to the xy plane shown in the figure, that is, parallel or approximately parallel to the element body 110. The ground plate 120 is formed of a plate-shaped member made of a conductive material such as metal, and the outer shape of the ground plate 120 may be any shape, for example, a rectangle. The outer shape of the ground plate 120 may also be circular, elliptical, triangular, or a polygon with pentagons or more. The ground plate 120 may have through holes (holes) as openings, as described later.

[0019] The antenna 10 comprises the element body 110 and the ground plate 120, as well as four second feed lines 131, 132, 133, and 134 made of a conductive material such as metal. Each of the second feed lines 131, 132, 133, and 134 extends vertically from the loop-center axis end of each of the four first feed lines in the feed element 100 toward the ground plate 120. The second feed lines 131, 132, 133, and 134 are vertical feed lines arranged in a concentrated manner around the loop-center axis A.

[0020] In the antenna 10 of this embodiment, of the four second feed lines 131, 132, 133, and 134, any two second feed lines 133 and 134 that are adjacent to each other in the circumferential direction around the loop central axis A are connected to the ground plate 120. The other two second feed lines 131 and 132 are connected to the signal line for the first polarization (horizontal polarization) and the signal line for the second polarization (vertical polarization), respectively, via feed ports 141 and 142, which are electrically insulated from the ground plate 120.

[0021] In Figures 1 and 2, the horizontally structured first power lines 111 and 113 and the opposing vertically structured second power lines 131 and 133 are power lines for the first polarization (horizontal polarization). In addition, the horizontally structured first power lines 112 and 114 and the opposing vertically structured second power lines 132 and 134 are power lines for the second polarization (vertical polarization).

[0022] Figure 3 is an explanatory diagram showing an example of the distribution of current vectors in the feed element 100 of the loop structure of the polarization-sharing antenna 10 shown in Figure 1. Figure 3 shows the results of calculating the current vectors when vertical (V) polarization is fed at multiple points set on the entire element body 110 and the first feed lines 111 to 114 of the feed element 100 using computer simulation. When transmitting and receiving vertical (V) polarized radio waves, for example, as shown in Figure 3, upward-facing currents I1 to I4 are generated at the left and right ends of the loop-shaped element body 110 and the first feed lines 112 and 114, respectively. This creates a vertically polarized electric field parallel to the yz plane in the figure. At this time, the current flowing at the upper and lower ends of the loop-shaped element body 110 and the first feed lines 111 and 113 is small, so the influence on the transmission and reception of horizontal (H) polarized radio waves can be reduced.

[0023] On the other hand, when transmitting and receiving horizontally (H) polarized radio waves, a lateral current is generated in the upper and lower ends of the loop-shaped element body 110 and in the first feed lines 111 and 113. This creates a horizontally polarized electric field parallel to the xz plane in the figure. In this case, the current flowing through the left and right ends of the loop-shaped element body 110 and the first feed lines 112 and 114 is small, thus reducing the impact on the transmission and reception of vertically (V) polarized radio waves.

[0024] Figure 4 is an explanatory diagram showing an example of the distribution of current vectors in the vertically structured second feed lines 131, 132, 133, and 134 of the polarization-sharing antenna 10 shown in Figure 2. Figure 4 shows the results of calculating the current vectors when vertically (V) polarized waves are fed at multiple points set throughout the vertically structured second feed lines 131 to 134 using computer simulation. When transmitting and receiving vertically (V) polarized radio waves, for example, as shown in Figure 4, a current I5 in the downward direction in the figure is generated in the second feed line 132, and a current I6 in the upward direction in the figure is generated in the second feed line 134. That is, opposite-phase currents flow in opposite directions in the opposing second feed lines 132 and 134. This makes it possible to suppress unwanted radiation in the lateral direction of the antenna while flowing vertically (V) polarized currents in the left and right ends of the loop-shaped element body 110 and in the first feed lines 112 and 114, respectively. In this case, the current flowing through the other second power lines 131 and 133 is small, thus reducing the impact on the transmission and reception of horizontally polarized (H) radio waves.

[0025] On the other hand, when transmitting and receiving horizontally (H) polarized radio waves, a current is generated in the downward direction in the diagram in one of the second feed lines 131 and 133, and an upward current is generated in the other. That is, opposite-phase currents flow in opposite directions in the opposing second feed lines 131 and 133. This makes it possible to suppress unwanted radiation in the lateral direction of the antenna while allowing horizontally (H) polarized current to flow through the upper and lower ends of the loop-shaped element body 110 and the first feed lines 111 and 113. At this time, the current flowing through the other second feed lines 132 and 134 is small, so the impact on the transmission and reception of vertically (V) polarized radio waves can be reduced.

[0026] As described above, the antenna 10 of this embodiment has a linear loop structure, which allows for weight reduction compared to a planar patch antenna.

[0027] Furthermore, with the antenna 10 of this embodiment, the loop length (circumference) of the element body 110 of the feed element 100 can be set to the length of one wavelength (1λ) or approximately one wavelength of the target radio wave. Compared to a patch antenna with a circumference of 2λ, the area is reduced (for example, to 1 / π of the area of ​​a patch antenna), thus enabling miniaturization.

[0028] Furthermore, according to the antenna 10 of this embodiment, vertical (V) polarization and horizontal (H) polarization feed lines 111-114, 131-134 can be arranged in the center of the loop-shaped feed element 100, reducing the effect of coupling between polarizations on the feed element 100 and enabling the shared use of vertical (V) polarization and horizontal (H) polarization.

[0029] Furthermore, according to the antenna 10 of this embodiment, by configuring an axisymmetric vertical structure of the feeding element that connects the second feeding lines 133 and 134, which are extended to the center inside the loop-shaped feeding element 100, to the ground plate 120, opposite phase currents flow through the opposing second feeding lines 132 and 134 for vertical (V) polarization, and opposite phase currents flow through the opposing second feeding lines 131 and 133 for horizontal (H) polarization. This suppresses the inverse F mode (the so-called operating mode of an inverse F antenna) and suppresses the vertical electric field (for example, the electric field along the plane including the z-axis in the figure), thereby suppressing unwanted radiation in the lateral direction of the antenna 10 (for example, the direction perpendicular to the z-axis in the figure) and improving the antenna gain.

[0030] In the antenna 10 of this embodiment, the ground plate 120 may be a ground plate without holes and without openings, or it may be a ground plate with a perforated structure having one or more openings. In particular, when using a ground plate with a perforated structure, the gain of the antenna 10 can be further improved and the FB ratio (front-to-back ratio) of the antenna 10 can also be improved, as shown below.

[0031] Figure 5 is a perspective view showing an example of a polarization-sharing antenna 10 having a holeless disc-shaped ground plate 120 according to an embodiment. In Figure 5, parts (components) common to Figures 1 and 2 are denoted by the same reference numerals, and their descriptions are omitted. Figure 6 shows the results of calculating the electric field vectors at multiple points set in the entire surrounding space in the longitudinal section (BB section) of the polarization-sharing antenna 10 having a holeless ground plate 120 as shown in Figure 5, using computer simulation. As shown in Figure 6, when a holeless ground plate 120 is used, unwanted radiation due to fringing electric field Ef is likely to occur in the space on the back side of the outer edge of the ground plate 120 of the antenna 10.

[0032] Figure 7 is a perspective view showing an example of a polarization-sharing antenna having a perforated disc-shaped ground plate 120 according to an embodiment. In Figure 7, the same reference numerals are used for parts that are the same as those in Figures 1 and 2, and their descriptions are omitted. In Figure 7, the ground plate 120 is a perforated ground plate having a plurality of rectangular openings 121, 122, 123, and 124 formed in a portion facing a part of the opening 101 of the feed element 100. By having openings 121, 122, 123, and 124 in the ground plate 120, the weight of the ground plate 120 can be reduced. Furthermore, by using a loop-structured feed element 100 and a perforated ground plate 120 in combination, the overall structure of the antenna 10 can be made perforated, thereby improving the wind load on the antenna 10 itself.

[0033] The opening (hole) in the ground plate 120 may be formed in a portion that faces the entire opening 101 of the power supply element. The shape of the opening (hole) in the ground plate 120 may be rectangular as shown in the figure, or it may be circular.

[0034] Figure 8 shows the results of computer simulations to calculate the electric field vectors at multiple points set in the entire surrounding space in the longitudinal section (CC section) of the polarization-sharing antenna having a perforated ground plate 120 as shown in Figure 7. As shown in Figure 8, when a perforated ground plate 120 is used, an electric field Ec opposite in phase to the fringing electric field is generated in the central space on the back side of the ground plate 120 of the antenna 10, and unwanted radiation to the space behind the antenna 10 can be suppressed. As a result, the gain of the antenna 10 can be further improved, and the FB ratio (front-to-back ratio) of the antenna 10 can also be improved.

[0035] Figure 9 is an explanatory diagram showing an example of the current vector distribution of a polarization-sharing antenna 10 having a holeless disc-shaped ground plate 120 as shown in Figure 5. In Figure 9, since the ground plate 120 does not have an opening (hole), the image currents I7 and I8 corresponding to the currents I1 and I2 flowing through the first feed lines 112 and 114 to form a vertically polarized electric field are distributed and flow through the ground plate 120, making it difficult to obtain the effect of canceling the fringing electric field mentioned above.

[0036] Figure 10 is an explanatory diagram showing an example of the distribution of current vectors in a polarization-sharing antenna 10 having a perforated ground plate 120 as shown in Figure 7. In Figure 10, the ground plate 120 has openings (holes) 121, 122, 123, and 124 in the portion facing the opening 101 of the feed element 100. Therefore, for example, image currents I7 and I8 corresponding to the currents I1 and I2 flowing through the first feed lines 112 and 114 to form a vertically polarized electric field are concentrated in the linear ground portion of the ground plate 120 (the portion facing the first feed lines 112 and 114), which has a symmetrical structure with respect to the first feed lines 112 and 114. As a result, the effect of canceling the fringing electric field mentioned above can be enhanced. Consequently, the gain of the antenna 10 can be further improved, and the FB ratio (front-back ratio) of the antenna 10 can also be further improved.

[0037] Figures 11, 12, and 13 are front, right, and rear views, respectively, showing examples of the external appearance of a polarization-sharing antenna 10 according to another embodiment. Figure 14 is an exploded perspective view of the polarization-sharing antenna 10 of Figure 11. Figure 15 is a longitudinal cross-sectional view (D-D cross-sectional view) of the polarization-sharing antenna 10 of Figure 11. In Figures 11 to 15, parts (components) common to those in Figures 1, 2, 5, and 7 are denoted by the same reference numerals, and their descriptions are omitted. Furthermore, although the antenna 10 of this embodiment has pin-shaped second feed lines (vertical feed lines) 131 to 134, the second feed lines (vertical feed lines) 131 to 134 are omitted in the perspective view of Figure 14 for illustrative purposes.

[0038] In Figures 11 to 15, the polarization-sharing antenna 10 further comprises a hollow disc-shaped parasitic element 150 made of a conductor such as metal, which is positioned opposite the feed element 100 at a predetermined separation distance, and a radome 155 as a protective member positioned to cover the feed element 100 and the parasitic element 150. The separation distance (spacing) between the parasitic element 150 and the feed element 100 is, for example, 0.01λ or approximately 0.01λ.

[0039] The passive element 150 electromagnetically couples with the power supply element 100, thereby expanding the frequency bandwidth. The overall shape of the passive element 150 is a loop shape similar to the element body 110 of the power supply element 100. The outer and inner diameters of the passive element 150 are smaller than the outer and inner diameters of the element body 110 of the power supply element 100, respectively.

[0040] The radome 155 functions as a protective member that protects the feed element 100, the second feed lines (vertical feed lines) 131, 132, 133, 134, and the passive element 150. The radome 155 also functions as a housing (protective case) for the antenna 10. The radome 155 is made of a material that has good transparency to the target radio waves. As the material of the radome 155, for example, a material with a low relative permittivity is used to suppress the reflection of radio waves on the surface, and a material with a low dielectric loss tangent is used to suppress the attenuation of radio waves due to dielectric loss during transmission. The material of the radome 155 may be, for example, fiberglass or fluororesin.

[0041] The radome 155 may have one or more openings through which wind can pass in order to improve the wind load on the antenna 10.

[0042] In Figures 11 to 15, the radome 155 has a convex portion 157 formed in the direction of the main directivity of the antenna 10, and a flange portion 156 formed on the circumference of the convex portion. Through holes 156a for antenna mounting are formed at four locations on the flange portion 156, with four rotational symmetries around the loop central axis A. A ground plate 120 is attached to the back surface of the flange portion 156 of the radome 155. Through holes 120a for antenna mounting are formed at four locations on the ground plate 120, with four rotational symmetries around the loop central axis A, corresponding to the through holes 156a for antenna mounting in the flange portion 156.

[0043] The passive element 150 and the power supply element 100 are mounted on the inner surface of the protrusion 157 of the radome 155. The outer peripheral edge of the element body 110 of the power supply element 100 is supported by the inner peripheral surface of the protrusion 157 of the radome 155. The inner end edges of the first power supply lines 111 to 114 are supported by the outer peripheral surface of the boss portion 158 formed in the center of the radome 155. The central portion of the ground plate 120 is supported by a support member 165 attached to the boss portion 158 of the radome 155.

[0044] The second feed lines (vertical feed lines) 131-134 are installed by passing them through the through-holes of the support members 165 attached to the boss portion 158 of the radome 155. One end of each of the second feed lines 131-134 (the upper end in Figure 15) is connected to the central axis end of the first feed lines 111-114 of the feed element 100. The other ends (lower ends in Figure 15) of two of the four second feed lines 131-134, 131 and 132, are each connected to two feed ports 141 that are insulated and installed at corresponding locations on the ground plate 120. The other ends (lower ends in Figure 15) of the remaining two second feed lines 133 and 134 are each directly connected to the ground plate 120.

[0045] A support member 165 is attached to the end of the boss portion 158 of the radome 155, which has a parasitic element 150 and a feeding element 100, and a ground plate 120 is attached via the support member 165. A bolt 160, which is a fixing member, is attached so as to pass through the central through hole 159 of the boss portion 158 of the radome 155, the central through hole 166 of the support member 165, and the central through hole 125 of the ground plate 120, and a nut 161, which is a fixing member, is attached to the tip of the bolt 160 and tightened. In this way, a small and lightweight antenna 10 can be assembled with the feeding element 100 having the first feeding lines 111 to 114, the ground plate 120, the second feeding lines 131 to 134, the parasitic element 150, and the radome 155 positioned in predetermined positions.

[0046] As described above, this embodiment provides a small, lightweight polarization-sharing antenna 10 that can achieve high antenna gain while suppressing unnecessary radio wave radiation to the rear.

[0047] Furthermore, the present invention provides a small, lightweight, and polarity-sharing antenna suitable for use as an antenna for radio equipment mounted on HAPS and UAVs in the air, which can achieve high antenna gain while suppressing unnecessary radio wave radiation to the rear, thus contributing to the achievement of Sustainable Development Goal (SDG) 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation." [Explanation of symbols]

[0048] 10: Polarization-sharing antenna 100: Power supply element 101: Opening 110: Element body 111-114: First power supply line 120: Groundboard 120a: Through hole 121~124: Opening 125: Central through hole 131-134: Second power supply line 141: Power supply port 142: Power supply port 150: Powerless element 155: Radome 156: Flange section 156a: Through hole 157: Convex part 158: Boss Section 159: Central through hole 160: Bolt 161: Nut 165: Support member 166: Central through hole

Claims

1. A polarization-sharing antenna used for two mutually orthogonal polarizations, A power supply element having an element body made of a loop-shaped conductor and four first power supply lines made of conductors extending laterally toward the loop central axis from four locations on the element body at equal angular intervals in the circumferential direction, A ground plate is positioned on the back of the power supply element so as to face it at a predetermined separation distance, The power supply element comprises four second power supply lines made of conductors that extend longitudinally from the loop-center axis end of each of the four first power supply lines toward the ground plate, A polarization-sharing antenna characterized in that, of the four second feed lines, any two second feed lines adjacent to each other in the circumferential direction around the loop central axis are connected to the ground plate, and the other two second feed lines are each connected to the signal lines of the two polarizations.

2. In the polarization-sharing antenna of claim 1, The polarization-sharing antenna is characterized in that the ground plate has one or more openings.

3. In the polarization-sharing antenna of claim 2, A polarization-sharing antenna characterized in that the opening of the ground plate is formed in a portion facing all or part of the opening of the power supply element.

4. In the polarization-sharing antenna of claim 1, 2, or 3, A polarization-sharing antenna further comprising a passive element made of a conductor, which is positioned opposite the power-feeding element at a predetermined separation distance.

5. In the polarization-sharing antenna of claim 4, A polarization-sharing antenna further comprising a protective member that covers and protects the power supply element, the second power supply line, and the powerless element.

6. In the polarization-sharing antenna of claim 5, The protective member is characterized by having one or more openings, thus forming a polarization-sharing antenna.

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