JP5432055B2 - Dual-polarization Yagi antenna - Google Patents

Description

  The present invention relates to a dual-polarization Yagi antenna that can obtain good cross polarization discrimination.

Conventionally, a Yagi antenna is known as a directional antenna used in the ultra-high frequency (VHF) band or higher. A perspective view showing an example of the configuration of a conventional Yagi antenna is shown in FIG.
A conventional Yagi antenna 100 shown in FIG. 11 is composed of a linear rod-shaped arm 114, three linear waveguide elements 111, a linear radiating element 110, and a linear reflective element 112. ing. In order from the front side of the arm 114, the three waveguide elements 111 are arranged substantially orthogonal to the arm 114, then the radiating element 110 is arranged substantially orthogonal to the arm 114, and the reflecting element 112 is arranged almost to the arm 114 on the rear side. They are arranged orthogonally. In this case, the waveguide element 111, the radiating element 110, and the reflecting element 112 are arranged substantially parallel to each other. Assuming that the wavelength of the operating frequency of the Yagi antenna 100 is λ, the length of the radiating element 110 is about λ / 2, and the length of the three waveguide elements 111 is slightly shorter than about λ / 2. The length of the element 112 is slightly longer than about λ / 2. In addition, the spacing between the three waveguide elements 111, the radiating element 110, and the reflecting element 112 is approximately λ / 4. As a result, the waveguide element 111 becomes capacitive and the reflection element 112 becomes inductive at the operating frequency, and has a directivity characteristic having a radiation beam with a small half-value angle in the direction from the reflection element 112 toward the waveguide element 111. It becomes like this.

  Each of the three waveguide elements 111 is attached to the arm 114 using a saddle fitting. The saddle fitting is an attachment fitting used to stably attach the waveguide element 111 to the arm 114 since the sectional shape of the arm 114 is circular and the sectional shape of the waveguide element 111 is circular. In order to stably attach the waveguide element 111 to the arm 114, a concave portion that coincides with the curved surface of the outer surface of the arm 114 is formed on the lower surface of the saddle fitting, and is in a direction perpendicular to the concave portion. A recess that matches the curved surface of the outer surface of the waveguide element 111 is formed on the upper surface of the saddle fitting. The reflective element 112 is also attached to the arm 114 using the saddle fitting described above. Further, the radiating element 110 is attached to the feeding box 113 fixed to the arm 114 by introducing an end, and power is fed from the feeding line to the end of the radiating element 110 in the feeding box 113. A feed line such as a coaxial cable is led out from the feed box 113.

  By the way, the Yagi antenna is installed so that the element is in the vertical or horizontal direction with respect to the ground so that it corresponds to either vertical polarization or horizontal polarization according to the communication system specifications and infrastructure communication specifications. Is done. In this case, the mode in which elements are arranged in the vertical direction with respect to the ground corresponds to vertical polarization, and the mode in which elements are arranged in parallel to the ground corresponds to horizontal polarization. Also, in future communication systems and broadcasting business fields, communication modes that use separate frequency bands for vertical polarization and horizontal polarization, and spatial multiplexing communication that uses both vertical and horizontal polarization, It is possible to do it. In this case, it is conceivable to use a dual-polarization Yagi antenna that can support vertical polarization and horizontal polarization with a single antenna device.

Therefore, FIG. 12 is a perspective view showing an example of the configuration of a conventional dual-polarization Yagi antenna, and FIG. 13 is a front view of an example of the configuration of the dual-polarization Yagi antenna.
The conventional polarized wave Yagi-type antenna 101 shown in these drawings includes a straight bar-shaped arm 128, three linear horizontal polarization-side waveguide elements 121 arranged in a horizontal plane, and a straight line. Horizontal polarization-side radiation element 120 and linear horizontal polarization-side reflection element 122, three linear vertical polarization-side waveguide elements 125 arranged in the vertical plane, and linear vertical polarization The wave-side radiation element 124 and the linear vertical polarization-side reflection element 126 are configured. In order from the front side of the arm 128, three horizontal polarization-side waveguide elements 121 and vertical polarization-side waveguide elements 125 are arranged substantially orthogonal to the arm 128, and then the horizontal polarization-side radiation element 120 and the vertical polarization-side The radiating element 124 is disposed substantially orthogonal to the arm 128, and the horizontal polarization side reflection element 122 and the vertical polarization side reflection element 126 are disposed substantially orthogonal to the arm 128 on the rear side. In this case, the horizontal polarization-side waveguide element 121, the horizontal polarization-side radiation element 120, and the horizontal polarization-side reflection element 122 are arranged in a horizontal plane substantially parallel to each other. Further, the vertical polarization side waveguide element 125, the vertical polarization side radiation element 124, and the vertical polarization side reflection element 126 are arranged in a vertical plane substantially parallel to each other.

  In the dual-polarization Yagi antenna 101, when the wavelength of the use frequency of the dual-polarization Yagi antenna 101 is λ, the length of the horizontal polarization-side radiation element 120 and the vertical polarization-side radiation element 124 is about λ / 2. The lengths of the three horizontal polarization side waveguide elements 121 and the vertical polarization side waveguide elements 125 are slightly shorter than about λ / 2. The horizontal polarization side reflection element 122 and the vertical polarization side reflection element The length of the element 126 is slightly longer than about λ / 2. Also, three horizontal polarization side waveguide elements 121 and vertical polarization side waveguide elements 125, horizontal polarization side radiation element 120 and vertical polarization side radiation element 124, horizontal polarization side reflection element 122 and vertical polarization side The interval between the elements in the side reflection element 126 is set to an interval of about λ / 4. As a result, the horizontal polarization side waveguide element 121 and the vertical polarization side waveguide element 125 become capacitive and the horizontal polarization side reflection element 122 and the vertical polarization side reflection element 126 become inductive at the operating frequency. The horizontal polarization and the vertical polarization having a small half-value angle in the direction from the horizontal polarization side reflection element 122 and the vertical polarization side reflection element 126 to the horizontal polarization side waveguide element 121 and the vertical polarization side waveguide element 125. It has a directivity characteristic with a radiation beam.

JP 2003-274296 A

  In the conventional dual-polarization Yagi antenna 101, each of the three horizontal polarization-side waveguide elements 121 and the horizontal polarization-side reflection element 122 is placed in a horizontal plane using a saddle fitting 130 as shown in FIG. It is attached to the arm 128 so as to be positioned, and each of the three vertical polarization side waveguide elements 125 and the vertical polarization side reflection element 126 is also positioned in the vertical plane using the saddle fitting 131. It is attached to the arm 128. In addition, the horizontal polarization side radiating element 120 is attached to the horizontal polarization side power supply box 123 with an end portion introduced into the horizontal polarization side power supply box 123 fixed to the arm 128 so as to be positioned in the horizontal plane. In FIG. 5, power is fed from the feeder to the end of the horizontally polarized radiation element 120. Further, the vertical polarization side radiating element 124 is attached to the vertical polarization side power supply box 127 fixed to the arm 128 so that the vertical polarization side radiation element 124 is positioned in the vertical plane. In the inside, power is fed from the feeder to the end of the vertically polarized radiation element 124. A feed line such as a coaxial cable is led out from the horizontal polarization side feed box 123 and the vertical polarization side feed box 127. Note that a balanced / unbalanced converter using a balun transformer composed of a toroidal core or the like connected between the feed line and the horizontally polarized radiation element 120 and the vertically polarized radiation element 124 is a horizontally polarized feed box. 123 and the vertical polarization side power supply box 127.

  The horizontally polarized wave radiating element 120, the horizontally polarized wave side waveguide element 121, and the horizontally polarized wave side reflecting element 122 attached to the arm 128 by the saddle fitting 130 are shifted from the central axis of the arm 128 as shown in FIG. The vertical polarization side radiating element 124, the vertical polarization side waveguide element 125, and the vertical polarization side reflection element 126, which are disposed at the positions and attached to the arm 128 by the saddle fitting 131, are also shown in FIG. It is arranged at a position shifted from the central axis. For this reason, the central axis of the Yagi antenna for horizontal polarization attached to the arm 128 does not coincide with the central axis of the Yagi antenna for vertical polarization.

Here, FIG. 14 shows the main polarization / cross polarization characteristics of the conventional Yagi antenna 101. In FIG. 14, the radiation level of the main polarization in the 0 ° direction is 0 dB. The direction of 0 ° is the direction of the central axis of the arm 128 from the horizontal polarization side reflection element 122 and the vertical polarization side reflection element 126 toward the three horizontal polarization side waveguide elements 121 and the vertical polarization side waveguide element 125. It is. Referring to FIG. 14, the half-value angle of the main polarization is within 30 °, and a sharp main beam is emitted in the 0 ° direction. The cross polarization is radiated at a large level as the cross polarization of about -17.3 dB in the 0 ° direction, and the cross polarization discrimination degree is only about 17.3 dB.
In this case, when the same frequency band is used for the vertical polarization and the horizontal polarization and the single antenna device supports the vertical polarization and the horizontal polarization, the cross polarization pattern degree of 20 dB or more is obtained. The goal is to be. However, in the conventional dual-polarization Yagi antenna 101, a cross polarization discrimination degree of 20 dB or more is not obtained. As a cause of this, it is conceivable that leaked radio waves are radiated from the feeding portions of the horizontally polarized radiation element 120 and the vertically polarized radiation element 124. Further, it is conceivable that the central axis of the horizontally polarized Yagi antenna attached to the arm 128 does not coincide with the central axis of the vertically polarized Yagi antenna.

  Therefore, an object of the present invention is to provide a polarization-shared Yagi antenna that can obtain excellent cross polarization discrimination.

  The dual-polarization Yagi-type antenna of the present invention is fixed to the arm so that the first waveguide element, the first radiating element, and the first reflecting element are arranged on a first plane including substantially the central axis of the arm. The second waveguide element, the second radiating element, and the second reflecting element are disposed on a second plane that is orthogonal to the first plane and includes the substantially central axis of the arm. In addition, a second Yagi antenna fixed to the arm, and a first feeding unit that feeds power from the unbalanced first feeding means to the balanced first radiating element via the first balanced / unbalanced converting means. And a second power feeding unit that feeds power from the unbalanced second power feeding means to the balanced second radiating element via the second balance / unbalance conversion means, and the first balance / unbalance conversion means. And the second balance / unbalance conversion means is housed in the conductive arm. It is the most important feature that you are.

  According to the present invention, the central axes of the horizontally polarized Yagi antenna and the vertically polarized Yagi antenna can be attached orthogonally to each other while passing through the central axis of the arm. In addition, the radiating element in the horizontally polarized Yagi antenna fed from the coaxial cable and the radiating element in the vertically polarized Yagi antenna are fed via a balanced / unbalanced converter housed in the arm. ing. As a result, in the dual-polarization Yagi antenna according to the present invention, an excellent degree of cross polarization discrimination can be obtained.

It is a perspective view which shows the structure of the polarization shared Yagi-type antenna concerning the Example of this invention. It is a front view which shows the structure of the polarization shared Yagi-type antenna concerning the Example of this invention. It is a perspective view which shows the structure of the balance-unbalance converter connected between the radiation element and the coaxial cable for electric power feeding. It is a front view which shows the structure of the electric power feeding part in the polarization shared Yagi-type antenna of this invention with sectional drawing. It is a side view which shows the structure of the electric power feeding part in the polarization shared Yagi-type antenna of this invention with sectional drawing. It is a front view which shows the attachment structure of the waveguide element of the polarization shared Yagi-type antenna concerning this invention with sectional drawing. It is a side view which shows the attachment structure of the waveguide element of the polarization shared Yagi-type antenna concerning this invention by sectional drawing. It is a front view which shows the attachment structure of the reflective element of the polarization shared Yagi-type antenna concerning this invention with sectional drawing. It is a side view which shows the attachment structure of the reflection element of the polarization shared Yagi-type antenna concerning this invention with sectional drawing. It is a figure which shows the main polarization and cross polarization characteristic of the polarization shared Yagi-type antenna concerning this invention. It is a perspective view which shows an example of a structure of the conventional Yagi antenna. It is a perspective view which shows an example of a structure of the conventional polarization shared Yagi-type antenna. It is a front view which shows an example of a structure of the conventional polarization shared Yagi-type antenna. It is a figure which shows the main polarization and cross polarization characteristic of the conventional polarization shared Yagi type | mold antenna.

1 and 2 show the configuration of a polarization sharing Yagi antenna 1 according to an embodiment of the present invention. FIG. 1 is a perspective view showing a configuration of a dual-polarization Yagi antenna 1 according to an embodiment of the present invention, and FIG. 2 is a front view showing a configuration of the dual-polarization Yagi antenna 1 according to an embodiment of the present invention. is there.
The dual-polarized Yagi antenna 1 according to the embodiments of the present invention shown in these drawings includes a straight metal arm 18 having a circular cross section and a plurality (for example, six) arranged in a horizontal plane. The linear horizontal polarization side waveguide element 11, the linear horizontal polarization side radiation element 10 and the linear horizontal polarization side reflection element 12, and a plurality (for example, 6) arranged in the vertical plane. A linear vertical polarization side waveguide element 15, a linear vertical polarization side radiation element 14, and a linear vertical polarization side reflection element 16. The arm 18 is divided into a first arm 18a at the front and a second arm 18b at the rear, and a shield cylinder 19 is disposed therebetween. A plurality of horizontal polarization-side waveguide elements 11 and vertical polarization-side waveguide elements 15 are arranged in order substantially orthogonal to the first arm 18a from the front side of the first arm 18a. Next, the horizontally polarized radiation element 10 and the vertically polarized radiation element 14 are arranged substantially orthogonal to the shield cylinder 19 arranged in the middle of the arm 18. The horizontally polarized radiation element 10 and the vertically polarized radiation element 14 are dipole elements. On the subsequent rear side, the horizontal polarization side reflection element 12 and the vertical polarization side reflection element 16 are arranged substantially orthogonal to the second arm 18b. In this case, the horizontally polarized wave side waveguide element 11, the horizontally polarized wave side radiating element 10 and the horizontally polarized wave side reflecting element 12 are arranged in a horizontal plane substantially parallel to each other to form a horizontally polarized Yagi antenna. doing. The vertically polarized wave side waveguide element 15, the vertically polarized wave side radiating element 14 and the vertically polarized wave side reflecting element 16 are arranged in a vertical plane substantially parallel to each other to form a vertically polarized Yagi antenna. doing.
The second arm 18b of the arm 18 also serves as a support, and the second arm 18b is attached to a support that supports the polarization-sharing Yagi antenna 1. The second arm 18b has a larger diameter than the first arm 18a, but can have the same diameter.

  In the dual-polarization Yagi antenna 1 according to the present invention, when the wavelength of the use frequency of the dual-polarization Yagi antenna 1 is λ, the horizontal polarization-side radiation element 10 and the vertical polarization-side radiation element that are dipole elements 14 has a length of about λ / 2, and the plurality of horizontal polarization side waveguide elements 11 and vertical polarization side waveguide elements 15 have a length slightly shorter than about λ / 2. The lengths of the side reflection element 12 and the vertical polarization side reflection element 16 are slightly longer than about λ / 2. Also, a plurality of horizontal polarization side waveguide elements 11 and vertical polarization side waveguide elements 15, horizontal polarization side radiation elements 10 and vertical polarization side radiation elements 14, horizontal polarization side reflection elements 12 and vertical polarization waves The interval between the elements in the side reflection element 16 is set to an interval of about λ / 4. As a result, the horizontal polarization side waveguide element 11 and the vertical polarization side waveguide element 15 become capacitive and the horizontal polarization side reflection element 12 and the vertical polarization side reflection element 16 become inductive at the operating frequency. The horizontal polarization and the vertical polarization having a small half-value angle in the direction from the horizontal polarization side reflection element 12 and the vertical polarization side reflection element 16 to the horizontal polarization side waveguide element 11 and the vertical polarization side waveguide element 15. It has a directional characteristic with a sharp beam of radiation.

  In the dual-polarization Yagi antenna 1 according to the present invention, each of the plurality of horizontal polarization-side waveguide elements 11 is positioned in the horizontal plane by the fixing bracket 20 as shown in FIG. Each of the plurality of vertically polarized wave side waveguide elements 15 is also attached to the first arm 18a by the fixing metal fitting 21 so as to be positioned in the vertical plane. Further, the horizontally polarized radiation element 10 and the vertically polarized radiation element 14 are attached to a shield cylinder 19 provided in the middle of the arm 18. The shield cylinder 19 is made of metal, and includes a balanced / unbalanced converter (to be described later) connected between the horizontally polarized radiation element 10 and the vertically polarized radiation element 14 and the coaxial cable. Has been. The horizontal polarization side radiating element 10 and the vertical polarization side radiating element 14 are supplied with power from a coaxial cable serving as an unbalanced line via the balanced / unbalanced converter. The coaxial cable is led out from an end portion of the arm 18 or led out from a drawing hole formed in the arm 18. Further, the horizontal polarization-side reflecting element 12 is attached to the second arm 18b so as to be positioned in a horizontal plane by screwing onto a screw protruding from an external ring fixed to the second arm 18b as described later. The vertical polarization side reflecting element 16 is also attached to the second arm 18b so as to be positioned in the vertical plane by screwing onto a screw protruding from an external ring fixed to the second arm 18b as will be described later. ing.

  The horizontal polarization side radiating element 10, the horizontal polarization side waveguide element 11, and the horizontal polarization side reflection element 12 attached to the arm 18 so as to be parallel to each other have the center axis of the arm 18 as shown in FIG. A Yagi antenna for horizontal polarization is arranged on a plane including the same. Further, as shown in FIG. 2, the vertical polarization side radiating element 14, the vertical polarization side waveguide element 15, and the vertical polarization side reflection element 16 attached to the arm 18 so as to be parallel to each other are substantially the same as those of the arm 18. A vertically polarized Yagi antenna is configured on a plane orthogonal to the plane including the central axis. For this reason, the central axis of the Yagi antenna for horizontal polarization attached perpendicularly to the arm 18 and the central axis of the Yagi antenna for vertical polarization almost coincide with each other.

Next, the balanced / unbalanced converter built in the shield cylinder 19 will be described. FIG. 3A is a top view showing a configuration of a balanced / unbalanced converter 30 connected between the radiating element and the coaxial cable for feeding, and FIG. It is a front view which shows the structure of the balance / unbalanced converter 30 connected between coaxial cables.
The radiating element is composed of two radiating elements 31a and 31b. The two radiating elements 31a and 31b are balanced, and are fed from an unbalanced coaxial cable 32. Therefore, the balanced / unbalanced converter 30 shown in FIGS. The radiating elements 31 a and 31 b and the coaxial cable 32 are connected. When the wavelength of the operating frequency of the radiating elements 31a and 31b is λ, the lengths of the radiating element 31a and the radiating element 31b are approximately λ / 4, respectively, and a dipole element having an electrical length of λ / 2 is formed. Has been.

  The balanced / unbalanced converter 30 includes a coaxial cable 32, a branch conductor 34 disposed adjacent to the coaxial cable 32 so as to be substantially parallel with a predetermined interval, and a short-circuit plate 33. The outer peripheral surface at the tip of the outer conductor 32b of the coaxial cable 32 is connected to a feeding end which is one end of one radiating element 31b, and the inner conductor 32a led out from the tip of the coaxial cable 32 is folded back. The inner conductor 32a of the branch conductor 34 disposed adjacent to the branch conductor 34 is used. In the coaxial cable 32, the inner conductor 32a is supported by an insulator and disposed at the center of the outer conductor 32b. In the branch conductor 34, the inner conductor 32a is supported by the insulator and disposed at the center of the outer conductor 34b. ing. In addition, the feeding end, which is one end of the other radiating element 31 a, is connected to the outer peripheral surface at the tip of the outer conductor 34 b of the branch conductor 34. Further, the length of the branch conductor 34 is approximately λ / 4, the lower end surface of the outer conductor 34 b of the branch conductor 34 is connected to the short-circuit plate 33, and the short-circuit plate 33 is the outer periphery of the outer conductor 32 b of the coaxial cable 32. Connected to the surface. In other words, the lower end of the branch conductor 34 having a length of about λ / 4 is short-circuited by the short-circuit plate 33 to the outer conductor 32 b at a position about λ / 4 below the end of the coaxial cable 32. The inner conductor 32a of the branch conductor 34 is inserted from the tip to a depth of about λg / 4, and the tip is open. Thus, the length of the inner conductor 32a in the branch conductor 34 is about λg / 4. Note that λg is the guide wavelength in the branch conductor 34.

  In the balanced / unbalanced converter 30 configured as described above, since the tip of the inner conductor 32a in the branch conductor 34 is open, the current flowing through the tip is minimized, and the length thereof is about λg / 4. Therefore, the current flowing through the inner conductor 32a at the tip of the branch conductor 34 is maximized. In the opposite direction to the current flowing through the inner conductor 32a, a current of the same magnitude flows on the inner surface of the outer conductor 34b facing, and the other radiating element 31a is excited by this current. Since the lower end of the outer conductor 34b having a length of about λ / 4 is short-circuited to the outer conductor 32b of the coaxial cable 32 by the short circuit plate 33, the branch conductor 34 is viewed from the front end of the outer conductor 34b. Impedance can be regarded as almost infinite. As a result, current does not flow on the outer surface of the external conductor 34b, and leakage current in the branch conductor 34 is prevented.

Furthermore, since the current flowing through the inner conductor 32a is maximized at the tip of the branch conductor 34, the current flowing through the inner conductor 32a is also maximized at the tip of the coaxial cable 32. In the opposite direction to the current flowing through the inner conductor 32a, a current of the same magnitude flows through the inner surface of the outer conductor 32b facing, and one radiating element 31b is excited by this current. Since the short-circuit plate 33 is short-circuited to the external conductor 34b of the branch conductor 34 at a position about λ / 4 from the front end of the external conductor 32b, the impedance viewed from the front end of the external conductor 32b of the coaxial cable 32 is obtained. Can be considered almost infinite. As a result, current does not flow on the outer surface of the outer conductor 32b, and leakage current in the coaxial cable 32 is prevented.
As described above, the unbalanced signal transmitted through the coaxial cable 32 by the balanced / unbalanced converter 30 is converted into a balanced signal and is fed to the balanced radiation elements 31a and 31b. In this case, no leakage current occurs in the balanced / unbalanced converter 30 as described above.

A front view showing the configuration of the feeding section in the polarization-sharing Yagi antenna 1 of the present invention in which such a balanced / unbalanced converter 30 is provided in the horizontally polarized radiation element 10 and the vertically polarized radiation element 14. FIG. 4 shows a diagram, and FIG. 5 shows a side view showing the configuration of the power feeding unit in the dual-polarization Yagi antenna 1 of the present invention.
In the power feeding section shown in these drawings, power is fed from the coaxial cable 40 to the horizontally polarized radiation element 10 composed of the two radiation elements 10a and 10b via the balanced / unbalanced converter, and the two radiation elements 14a. , 14b is fed from the coaxial cable 41 via a balanced / unbalanced converter. In the power feeding section for feeding power to the horizontally polarized radiation element 10, the power feeding end, which is one end of one radiation element 10 a, is fixed to the outer peripheral surface at the tip of the outer conductor 40 b of the coaxial cable 40 and electrically connected. The internal conductor 40a connected and led out from the tip of the coaxial cable 40 is folded and used as the internal conductor of the branch conductor 42 arranged in parallel. In the coaxial cable 40, the inner conductor 40a is supported by an insulator and disposed at the approximate center of the outer conductor 40b. In the branch conductor 42, the inner conductor 40a is supported by the insulator and disposed at approximately the center of the outer conductor 42b. ing. In addition, the feeding end, which is one end of the other radiating element 10 b, is fixed to and electrically connected to the outer peripheral surface at the tip of the outer conductor 42 b of the branch conductor 42. Further, the length of the branch conductor 42 is approximately λ / 4, and the lower end surface of the outer conductor 42 b of the branch conductor 42 is connected to the short-circuit plate 44, and the short-circuit plate 44 is connected to the outer conductor 40 b of the coaxial cable 40. It is connected to the outer peripheral surface. That is, the lower end of the branch conductor 42 having a length of about λ / 4 is short-circuited by the short-circuit plate 44 to the outer conductor 40 b at a position about λ / 4 below the tip of the coaxial cable 40. Further, the inner conductor 40a in the branch conductor 42 is inserted from the tip to a depth of about λg / 4, and the tip is open. Thus, the length of the inner conductor 40a in the branch conductor 42 is about λg / 4. Note that λg is the guide wavelength in the branch conductor 42. As described above, the balanced / unbalanced converter that supplies power to the horizontally polarized radiation element 10 includes the coaxial cable 40, the branch conductor 42, and the short-circuit plate 44.

  In addition, in the power feeding section that feeds power to the vertically polarized radiation element 14, power is fed from the coaxial cable 41 to the vertically polarized radiation element 14 composed of two radiation elements 14a and 14b via a balanced / unbalanced converter. Yes. That is, the feeding end, which is one end of one of the radiating elements 14a, is fixed to and electrically connected to the outer peripheral surface at the tip of the outer conductor 41b of the coaxial cable 41, and the inner conductor 41a led out from the tip of the coaxial cable 41 is The inner conductor of the branch conductor 43 is folded and arranged in parallel. In the coaxial cable 41, the inner conductor 41a is supported by an insulator and disposed at the approximate center of the outer conductor 41b. In the branch conductor 43, the inner conductor 41a is supported by an insulator and disposed at the approximate center of the outer conductor 43b. ing. In addition, the feeding end, which is one end of the other radiating element 14 b, is fixed to and electrically connected to the outer peripheral surface at the tip of the outer conductor 43 b of the branch conductor 43. Further, the length of the branch conductor 43 is about λ / 4, and the lower end surface of the outer conductor 43 b in the branch conductor 43 is connected to the short-circuit plate 45, and the short-circuit plate 45 is connected to the outer conductor 41 b of the coaxial cable 41. It is connected to the outer peripheral surface. That is, the lower end of the branch conductor 43 having a length of about λ / 4 is short-circuited by the short-circuit plate 45 to the outer conductor 41b at a position below the length of the coaxial cable 41 by about λ / 4. Further, the inner conductor 41a in the branch conductor 43 is inserted from the tip to a depth of about λg / 4, and the tip is open. Thus, the length of the inner conductor 41a in the branch conductor 43 is about λg / 4. Note that λg is the guide wavelength in the branch conductor 43. As described above, the balanced / unbalanced converter that feeds the vertically polarized radiation element 14 includes the coaxial cable 41, the branch conductor 43, and the short-circuit plate 45.

As described above, in the power feeding unit, the folded portion of the inner conductor 41a on the horizontally polarized wave side is disposed substantially orthogonal to the folded portion of the inner conductor 40a on the vertically polarized wave side, and the folded horizontal portion of the inner conductor 40a and An insulating plate 46 is disposed between the folded horizontal portions of the inner conductor 41a to prevent short circuit between them. Further, the coaxial cable 41 and the branch conductor 43 are arranged substantially orthogonally between the coaxial cable 40 and the branch conductor 42, so that the power feeding unit is made compact. For this reason, the power feeding section can be stored in the shield cylinder 19 and the arm 18.
As shown in FIG. 5, the outer diameter of the shield cylinder 19 is slightly larger than the outer diameter of the arm 18, but the inner diameter of the shield cylinder 19 is smaller than the inner diameter of the arm 18. A step is formed at a portion of a predetermined length from both ends of the arm, and the outer diameter of one end is substantially equal to the inner diameter of the first arm 18a, and the outer diameter of the other end is approximately equal to the inner diameter of the second arm 18b. . A male screw is formed on the outer peripheral surface of the other end portion of the shield cylinder 19, and a female screw is formed on the inner peripheral surface of the second arm 18b. The second arm 18b is fixed to the shield cylinder 19 by screwing the male screw formed on the outer peripheral surface of the shield cylinder 19 to the female screw formed on the inner periphery of the second arm 18b. Further, one end of the shield cylinder 19 having a small diameter is fitted and inserted into the first arm 18a, and a plurality of screws are screwed into the first arm 18a from the lateral direction so that the tip of the screw is one end of the shield cylinder. And is fixed to the shield cylinder 19 in a non-rotatable manner on the first arm 18a. As a result, the shield cylinder 19 is firmly fixed between the first arm 18a and the second arm 18b. In addition, four insertion holes penetrating from the inner peripheral surface to the outer peripheral surface are formed in the shield cylinder 19 so as to form an angle of about 90 ° with each other, and the horizontal polarization side radiation element 10 is formed in each of the insertion holes. The two radiating elements 10a and 10b and the two radiating elements 14a and 14b of the vertically polarized radiation element 14 are inserted and led out from the shield cylinder 19. In this case, the radiating elements 10a and 10b and the radiating elements 14a and 14b are supported by insertion holes formed in the shield cylinder 19 by supporting means made of an insulating material, but the configuration is omitted. Yes.

  In the horizontal and vertical balanced / unbalanced converters in the power feeding section, the tips of the inner conductors 40a and 41a in the branch conductors 42 and 43 are open, so that the current flowing through the tips is minimized and the length thereof is reduced. Since it is about λg / 4, the current flowing through the inner conductors 40a and 41a at the tips of the branch conductors 42 and 43 is maximized. In the opposite direction to the current flowing through the inner conductors 40a and 41a, a current of the same magnitude flows through the inner surfaces of the outer conductors 42b and 43b facing each other, and the other radiating elements 10b and 14b are excited by this current. Since the lower ends of the outer conductors 42b and 43b having a length of about λ / 4 are short-circuited to the outer conductors 40b and 41b of the coaxial cables 40 and 41 by the short-circuit plates 44 and 45, the branch conductors 42 and The impedance viewed from the tips of the 43 outer conductors 42b and 43b can be regarded as almost infinite. As a result, current does not flow on the outer surfaces of the external conductors 42b and 43b, and leakage current in the branch conductors 42 and 43 is prevented.

Furthermore, since the current flowing through the inner conductors 40a and 41a is maximized at the ends of the branch conductors 42 and 43, the current flowing through the inner conductors 40a and 41a is maximized at the ends of the coaxial cables 40 and 41. In the opposite direction to the current flowing through the inner conductors 40a and 41a, a current of the same magnitude flows on the inner surfaces of the outer conductors 40b and 41b facing each other, and the one radiating element 10a and 14a is excited by this current. Since the outer conductors 40b and 41b are short-circuited to the outer conductors 42b and 43b of the branch conductors 42 and 43 by the short-circuit plates 44 and 45 at a position about λ / 4 from the tip of the outer conductors 40b and 41b, the coaxial cables 40 and 41 are connected. The impedance viewed from the tips of the outer conductors 40b and 41b can be regarded as almost infinite. As a result, current does not flow on the outer surfaces of the outer conductors 40b and 41b, and leakage current in the coaxial cables 40 and 41 is prevented.
As described above, the unbalanced signal transmitted through the coaxial cables 40 and 41 by the two balanced / unbalanced converters in the power supply unit is converted into a balanced signal, and the balanced horizontal polarization side radiation elements 10a and 10b are converted. In addition, power is supplied to the vertical radiating elements 14a and 14b.

The reason why the leakage current does not flow in the horizontal polarization side power supply unit and the vertical polarization side power supply unit in the power supply unit is that it does not flow theoretically. Thus, the radiation field is affected by the leakage current. Therefore, in the polarization-shared Yagi type antenna 1 of the present invention, as shown in FIGS. 4 and 5, the horizontal polarization side feeding unit and the vertical polarization side feeding unit having balanced / unbalanced converters are crossed. By arranging and compacting in this way, the horizontal polarization side power supply unit and the vertical polarization side power supply unit can be accommodated in the shield cylinder 19. A first arm 18 a and a second arm 18 b divided as shown in FIG. 5 are fixed to the front and rear of the shield cylinder 19, and are integrated with the shield cylinder 19. Since the first arm 18a, the second arm 18b, and the shield cylinder 19 are made of metallic pipes, even if a slight amount of leakage current occurs in the horizontal polarization side power supply unit and the vertical polarization side power supply unit. Thus, the influence on the radiation field due to the leakage current can be prevented.
An insulating separator that supports the coaxial cables 40 and 41 and the branch conductors 42 and 43 so as to be substantially parallel is provided in the arm 18 and the shield cylinder 19 at a predetermined interval.

Next, FIG. 6 and FIG. 7 show a fixing structure for fixing the horizontal polarization side waveguide element 11 and the vertical polarization side waveguide element 15 to the first arm 18a. FIG. 6 is a front view showing a cross-sectional view of the mounting structure of the waveguide element of the dual-polarization Yagi antenna 1 according to the present invention, and FIG. 7 shows the mounting of the waveguide element of the dual-polarization Yagi antenna according to the present invention. It is a side view which shows a structure with sectional drawing.
In the mounting structure shown in these drawings, the horizontally polarized wave side waveguide element 11 is composed of two waveguide elements 11a and 11b, and a screw is formed on the outer peripheral surface of the root part of the waveguide elements 11a and 11b. Has been. The vertically polarized wave-side waveguide element 15 includes waveguide elements 15a and 15b divided into two, and a screw is formed on the outer peripheral surface of the root part of the waveguide elements 15a and 15b. A cylindrical inner ring 50 is inserted into the first arm 18a having a circular cross section. The inner ring 50 is made of metal or resin, and the inner ring 50 is formed with four screw holes in which screws are formed at an angle of about 90 ° to each other. In addition, insertion holes corresponding to the screw holes of the inner ring 50 are provided at about 90 positions at positions where the plurality of horizontal polarization side waveguide elements 11 and vertical polarization side waveguide elements 15 are attached to the first arm 18a. Four are formed to have an angle of °.

  The screws formed at the roots of the waveguide elements 11a and 11b of the horizontally polarized wave side waveguide element 11 and the waveguide elements 15a and 15b of the vertically polarized wave side waveguide element 15 protrude by a predetermined length. As described above, the fixing bracket 20a is fixed to the waveguide element 11a, the fixing bracket 20b is fixed to the waveguide element 11b, the fixing bracket 21a is fixed to the waveguide element 15a, and the fixing bracket 21b is fixed to the waveguide element 15b. Next, bushes 51a, 51b, 51c, 51d are inserted into the screws protruding from the waveguide elements 11a, 11b and the waveguide elements 15a, 15b, respectively, and the position of the internal ring 50 inserted into the first arm 18a is determined. The screw holes are adjusted to be aligned with the insertion holes formed in the first arm 18a, and the waveguide elements 11a and 11b of the horizontal polarization side waveguide element 11 and the waveguides 15 of the vertical polarization side waveguide element 15 are guided to the insertion holes. The wave elements 15 a and 15 b are inserted, and the screws formed at the roots of the wave elements 15 a and 15 b are respectively screwed into the screw holes of the inner ring 50. Further, by rotating the fixing fittings 20a, 20b, 21a, 21b and fastening them to the inner ring 50, the waveguide elements 11a, 11b of the horizontal polarization side waveguide element 11 and the vertical polarization side waveguide element 15 are fixed. The waveguide elements 15a and 15b can be fixed to the first arm 18a so as to be orthogonal to each other. A plurality of inner rings 50 are inserted into the first arm 18a corresponding to the plurality of insertion holes formed in the first arm 18a, and a plurality of inner rings 50 are utilized by using the respective inner rings 50. The horizontally polarized wave side waveguide element 11 and the vertically polarized wave side waveguide element 15 are fixed to the first arm 18a so as to be orthogonal to each other. Further, spring washers are interposed between the fixing brackets 20a, 20b, 21a, 21b and the bushes 51a, 51b, 51c, 51d.

Next, FIGS. 8 and 9 show a fixing structure for fixing the horizontal polarization side reflection element 12 and the vertical polarization side reflection element 16 to the second arm 18b. FIG. 8 is a front view showing a reflection element mounting structure of the dual-polarization Yagi antenna 1 according to the present invention in a sectional view, and FIG. 9 shows a reflection element mounting structure of the dual-polarization Yagi antenna according to the present invention. It is a side view shown with sectional drawing. After the second arm 18b is fixed to the shield cylinder 19, the horizontal polarization side reflection element 12 and the vertical polarization side reflection element 16 are fixed to the second arm 18b.
In the mounting structure shown in these drawings, the horizontal polarization side reflection element 12 is composed of two reflection elements 12a and 12b, and a screw is formed inside the base part of the reflection elements 12a and 12b. The vertical polarization side reflection element 16 includes reflection elements 16a and 16b divided into two, and a screw is formed inside the base part of the reflection elements 16a and 16b. Further, a cylindrical outer ring 53 is fitted on the outer side of the second arm 18b having a circular cross section, and the four bosses 52a and 52b are projected on the outer peripheral surface of the outer ring 53 at an angle of about 90 °. , 52c, 52d are formed. The outer ring 53 is made of metal or resin, and each of the bosses 52a, 52b, 52c, 52d is provided with a threaded hole.

Screw portions 12c, 12d and screw portions 16c, 16d are screwed to the bosses 52a, 52b, 52c, 52d, respectively, and the tips of the screw portions 12c, 12d and the screw portions 16c, 16d are outer peripheral surfaces of the second arm 18b. Pressure contact. Next, the spring seats 12f and 12h and the spring seats 16f and 16h are fitted and inserted into the screw parts 12c and 12d and the screw parts 16c and 16d, respectively, and the hexagonal nuts 12e and 12g are inserted into the screw parts 12c and 12g, respectively. 12d, and hexagonal nuts 16e and 16g are screwed to the screw parts 16c and 16d, respectively. As a result, the tips of the screw portions 12c, 12d, 16c, and 16d are pressed against the outer peripheral surface of the second arm 18b, so that the outer ring 53 is fixed to a predetermined position of the second arm 18b so as not to rotate.
Then, the screws formed inside the reflecting elements 12a and 12b are screwed to the screw portions 12c and 12d protruding from the nuts 12e and 12g, respectively, by a predetermined length. In addition, screws formed inside the reflecting elements 16a and 16b are screwed onto the screw portions 16c and 16d protruding from the nuts 16e and 16g, respectively, by a predetermined length. Thereby, the reflection elements 12a and 12b of the horizontal polarization side reflection element 12 are fixed to the screw portions 12c and 12d, and the reflection elements 16a and 16b of the vertical polarization side reflection element 16 are fixed to the screw portions 16c and 16d. Thus, the horizontal polarization side reflection element 12 and the vertical polarization side reflection element 16 are fixed to the second arm 18b so as to be orthogonal to each other.

  Here, FIG. 10 shows the main polarization / cross polarization characteristics of the dual-polarization Yagi antenna 1 according to the present invention. In FIG. 10, the radiation level of the main polarization in the 0 ° direction is set to 0 dB. The direction of 0 ° is the direction of the central axis of the arm 18 from the horizontal polarization side reflection element 12 and the vertical polarization side reflection element 16 toward the plurality of horizontal polarization side waveguide elements 11 and the vertical polarization side waveguide elements 15. It is. Referring to FIG. 10, the half-value angle of the main polarization is within 30 °, and a sharp main beam is emitted in the 0 ° direction. The cross polarization is emitted at a small level of about −30.3 dB in the 0 ° direction, and a good value of about 30.3 dB is obtained as the cross polarization discrimination. Thus, a good cross polarization discrimination is obtained because the dual-polarization Yagi antenna 1 according to the present invention accommodates the power feeding unit in the shield cylinder 19 even if a small amount of leakage current occurs in the power feeding unit. The effect of the leakage current on the radiation field can be prevented, and the central axis of the horizontally polarized Yagi antenna attached to the arm 18 and the vertically polarized Yagi antenna. This is probably because the central axis coincides with the configuration.

  In the dual-polarization Yagi antenna according to the present invention described above, the waveguide element, the radiating element, and the reflection element that constitute the horizontal polarization side Yagi antenna, and the waveguide element that constitutes the vertical polarization side Yagi antenna The radiating element and the reflecting element can be attached perpendicular to each other through the central axis of the arm. In addition, the radiating element in the horizontally polarized Yagi antenna fed from the coaxial cable and the radiating element in the vertically polarized Yagi antenna are fed via a balanced / unbalanced converter housed in the arm. I am doing so. As a result, in the dual-polarization Yagi antenna according to the present invention, an excellent degree of cross polarization discrimination can be obtained.

DESCRIPTION OF SYMBOLS 1 Polarization shared Yagi-type antenna, 10 Horizontal polarization side radiation element, 10a, 10b Radiation element, 11 Horizontal polarization side waveguide element, 11a, 11b Waveguide element, 12 Horizontal polarization side reflection element, 12a, 12b Reflection Element, 12c Screw part, 12d Screw part, 12e Nut, 12f Spring washer, 12g Nut, 12h Spring washer, 14 Vertical polarization side radiation element, 14a, 14d Radiation element, 15 Vertical polarization side waveguide element, 15a, 15b Waveguide element, 16 Vertical polarization side reflection element, 16a, 16b Reflection element, 16c Screw part, 16d Screw part, 16e Nut, 16f Spring washer, 16g Nut, 16h Spring washer, 18 arm, 18a First arm, 18b First 2 arms, 19 shield tube, 20 fixing bracket, 20a fixing bracket, 20b fixing bracket, 21 fixing bracket, 21a Fixing bracket, 21b Fixing bracket, 30 Unbalanced transducer, 31a Radiation element, 31a, 31b Radiation element, 32 Coaxial cable, 32a Inner conductor, 32b Outer conductor, 33 Short-circuit plate, 34 Branch conductor, 34b Outer conductor, 40 Coaxial cable 40a inner conductor, 40b outer conductor, 41 coaxial cable, 41a inner conductor, 41b outer conductor, 42 branch conductor, 42b outer conductor, 43 branch conductor, 43b outer conductor, 44 short circuit board, 45 short circuit board, 46 insulation board, 50 Inner ring, 51a bush, 52a to 52d boss, 53 Outer ring, 100 Yagi antenna, 101 Polarization shared Yagi antenna, 110 Radiating element, 111 Waveguide element, 112 Reflecting element, 113 Feeding box, 114 Arm, 120 Horizontal offset Wave-side radiation element, 121 horizontally polarized wave-side waveguide element, 122 Horizontal polarization side reflection element, 123 Horizontal polarization side feeding box, 124 Vertical polarization side radiation element, 125 Vertical polarization side waveguide element, 126 Vertical polarization side reflection element, 127 Vertical polarization side feeding box, 128 Arm, 130 saddle bracket, 131 saddle bracket

Claims (2)

A first Yagi antenna fixed to the arm such that the first waveguide element, the first radiating element, and the first reflecting element are disposed on a first plane including a substantially central axis of the arm;
The second waveguide element, the second radiating element, and the second reflecting element are fixed to the arm so that the second waveguide element, the second radiating element, and the second reflecting element are disposed on a second plane that is orthogonal to the first plane and includes substantially the central axis of the arm. The second Yagi antenna,
A first power feeding unit that feeds power from the unbalanced first feeding means to the balanced first radiation element via the first balanced / unbalanced converting means;
A second power feeding section that feeds power from the unbalanced second power feeding means to the balanced second radiation element via the second balance / unbalance conversion means,
The polarization-shared Yagi antenna, wherein the first balanced / unbalanced converting means and the second balanced / unbalanced converting means are housed in the conductive arm.   The arm is divided, and a conductive shield cylinder is provided in the middle of the arm. The first radiating element and the second radiating element are attached to the shield cylinder, and the shield 2. The polarization-shared Yagi antenna according to claim 1, wherein the first balanced / unbalanced converting means and the second balanced / unbalanced converting means are accommodated in a cylinder.

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