Dipole antenna and radio wave direction finder

Abstract

To provide a dipole antenna and a radio direction finding device that has a simple structure, can receive radio waves in a wide frequency band, and has near-omnidirectional directivity.SOLUTION: A dipole antenna 1 includes a dipole 20 having a total length L corresponding to the wavelength of the center frequency of the frequency band used. The dipole 20 has a pair of elements 21 and 22 that are inclined at a predetermined inclination angle θ from a reference plane Sq passing through a feeding point Q in a front direction D perpendicular to the reference plane Sq.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a dipole antenna and a radio wave direction finder. [Background technology]

[0002] There have been radio wave direction finders for receiving radio waves in a wide frequency band from a wide azimuth angle range. Antennas such as sleeve dipole antennas, biconical antennas, and discone antennas have been used in radio wave direction finders (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 6-77314 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the radio wave direction finder has a problem in that it has a complicated structure because it is capable of receiving radio waves in a wide frequency band and has as little directivity as possible.

[0005] In view of the above-mentioned problems, the present invention aims to provide a dipole antenna and a radio wave direction finder that have a simple structure, are capable of receiving radio waves over a wide frequency band, and have directivity that is close to omnidirectional. [Means for solving the problem]

[0006] A dipole antenna according to one aspect of the present invention comprises a dipole having a total length corresponding to the wavelength of the center frequency of the frequency band in use, and the dipole has a pair of elements inclined at a predetermined inclination angle from a reference plane passing through a feed point toward a front direction perpendicular to the reference plane. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a dipole antenna and a radio wave direction finder that have a simple structure, are capable of receiving radio waves in a wide frequency band, and have near-omnidirectional directivity. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a partial perspective view of a radio wave direction finding device according to an embodiment; [Figure 2] FIG. 2 is a side view of the dipole antenna according to the embodiment. [Figure 3] FIG. 10 is a comparison diagram of gain characteristics in the front direction of dipole antennas. [Figure 4] FIG. 2 is a side view of a dipole antenna according to an embodiment of the minimum configuration. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a partial perspective view of a radio wave direction finding device 100 according to the embodiment. Fig. 2 is a side view of a dipole antenna 1 according to the embodiment.

[0010] 1 and 2, a radio wave direction finding device 100 according to the embodiment includes a dipole antenna 1. The radio wave direction finding device 100 according to the embodiment may include a support 10 that supports the dipole antenna 1.

[0011] The support pole 10 is a linear structure that supports the dipole antenna 1. The support pole 10 is installed on the ground or a structure, for example, extending vertically.

[0012] The dipole antenna 1 is supported on the side of the support mast 10. The dipole antenna 1 extends in a direction away from the support mast 10. For example, if the extension direction of the support mast 10 is vertical, the dipole antenna 1 extends in the horizontal direction, which is perpendicular to the extension direction. A plurality of dipole antennas 1 may be arranged radially when viewed from the vertical direction (hereinafter, this may be used to mean the same as the extension direction of the support mast 10). As shown in FIG. 1, the dipole antennas 1 may be arranged radially at five locations when viewed from the vertical direction. When viewed from the vertical direction, the dipole antennas 1 may be arranged at equal intervals in the circumferential direction around the support mast 10.

[0013] The dipole antenna 1 has a support arm 23 supported by a support pole 10 and a dipole 20 .

[0014] The support arm 23 is a structure having the rigidity and strength to support the dipole 20. One end of the support arm 23 is cantilevered on the support column 10. The other end of the support arm 23 supports the dipole 20. The support arm 23 extends radially and linearly when viewed in the vertical direction. The support arms 23 may be arranged in five locations, for example. The support arm 23 is, for example, a cylindrical body extending linearly along a direction perpendicular (horizontal) to the extension direction (vertical direction) of the support column 10. A communication cable or the like including a conductor that constitutes a communication circuit connected to the dipole 20 passes through the support arm 23 along its extension direction.

[0015] The dipole 20 is composed of a pair of elements 21 and 22. The dipole 20 is arranged so as to be parallel to a plane parallel to the extension direction of the support 10 (a vertical plane when the support 10 extends vertically).

[0016] The pair of elements 21, 22 are, for example, tubes made of a metal such as aluminum. The pair of elements 21, 22 are arranged along a plane parallel to the extension direction of the support 10 (a vertical plane if the support 10 extends vertically). The pair of elements 21, 22 each extend in a direction away from a feed point Q. The feed point Q is the position where a conductor arranged along the support arm 23 branches into one element 21 and the other element 22. The current passing through the conductor changes direction at the feed point Q. The conductor is bundled while being arranged along the support arm 23. The conductor is connected to each of the pair of elements 21, 22. The feed point Q is, for example, the tip of the support arm 23 in the front direction D.

[0017] The pair of elements 21 and 22 may be arranged symmetrically in the vertical direction with respect to the front direction D that passes through the feed point Q. In other words, the pair of elements 21 and 22 may be arranged above and below the feed point Q, respectively, with the feed point Q in between.

[0018] 2, dipole 20 has a total length L corresponding to the wavelength of the center frequency of the frequency band in use. Note that total length L is the distance parallel to reference plane Sq from one tip 21e to the other tip 22e of dipole 20 (the length when viewed along the front direction D). The dipole 20 also has a pair of elements 21 and 22 that are inclined at a predetermined inclination angle θ from a reference plane Sq that passes through the feed point Q to a front direction D that is perpendicular to the reference plane Sq. The reference plane Sq may be a vertical plane that is parallel to the extension direction of the support 10 and perpendicular to the support arm 23.

[0019] As described above, dipole antenna 1 includes dipole 20 having total length L corresponding to the wavelength of the center frequency of the frequency band in use. Dipole 20 has a pair of elements 21 and 22 that are inclined at a predetermined inclination angle θ from reference plane Sq that passes through feed point Q toward a front direction D perpendicular to reference plane Sq. By adjusting the relationship between total length L and inclination angle θ of dipole 20, radio waves over a wide frequency band can be received while suppressing an increase in directivity. Therefore, by using this dipole antenna, it is possible to provide an antenna and radio wave direction finder with a simple structure that can receive radio waves over a wide frequency band and has directivity that is close to omnidirectional, without the need to combine multiple types of antenna systems with low directivity to cover a wide frequency band. The total length L preferably corresponds to 0.5 to 1.5 wavelengths of the center frequency of the frequency band in use. The tilt angle θ is preferably 10 to 45 degrees. This allows for more effective reception of radio waves over a wide frequency band while minimizing the increase in directivity.

[0020] Furthermore, it is preferable that dipole 20 has curled portions 21c, 22c at its tip that are curved so as to convex in front direction D. In other words, curled portions 21c, 22c are bent in the opposite direction to front direction D. By curving the tip of dipole 20 so as to convex in front direction D in this way, it is possible to suppress the directivity that is strengthened by tilting elements 21, 22 in front direction D, and it is possible to achieve a structure that can receive radio waves in a wide frequency band and has directivity that is close to omnidirectional.

[0021] Furthermore, it is preferable that the radius of curvature r of curled portions 21c, 22c is 0.02 to 0.3 wavelengths of the center frequency of the frequency band being used. In this way, by setting the radius of curvature r of curled portions 21c, 22c to 0.02 to 0.3 wavelengths of the center frequency of the frequency band being used, it is possible to effectively suppress the directivity that is strengthened by tilting elements 21, 22 toward the front direction D, and to achieve a structure that can receive radio waves over a wide frequency band and has directivity that is close to omnidirectional.

[0022] Furthermore, the central angle α of curled portions 21c, 22c is preferably 30° or greater and 180° or less. By setting the central angle α of curled portions 21c, 22c to 30° or greater and 180° or less in this way, it is possible to effectively suppress the directivity that is strengthened by tilting elements 21, 22 toward front direction D, and to achieve a structure that can receive radio waves over a wide frequency band and has directivity that is close to omnidirectional.

[0023] Next, with reference to FIG. 3, the gain characteristics in the front direction D of the dipole antenna 1 according to this embodiment will be described in comparison with a comparative example. Fig. 3 is a comparison diagram of gain characteristics in the front direction D of various dipole antennas. In Fig. 3, the horizontal axis represents frequency and the vertical axis represents gain. In Fig. 3, the thick line a represents the gain curve of the dipole antenna 1 according to this embodiment. In Fig. 3, the dashed line b represents a representative example of the gain curve of the sleeve dipole antenna according to Comparative Example 1. In Fig. 3, the thin line c represents a representative example of the gain curve of the dipole antenna according to Comparative Example 2 that is capable of receiving narrow frequency band radio waves.

[0024] 3, in this embodiment and Comparative Example 1, a gain of -10 dBi or more is obtained in the frequency band from about 0.1 GHz to 0.7 GHz. In contrast, in Comparative Example 2, the frequency band in which a gain of -10 dBi or more is obtained is limited to the frequency band from about 0.1 GHz to 0.45 GHz. In this way, the dipole antenna 1 of this embodiment has a simple structure, is small and lightweight like a narrow frequency band dipole antenna, yet provides performance equivalent to that of a large, heavy antenna with a complex structure such as a sleeve dipole.

[0025] <Embodiment of minimum configuration> Hereinafter, an embodiment of the minimum configuration of the dipole antenna 1 according to the present invention will be described with reference to Fig. 4. Fig. 4 is a side view of the dipole antenna 1 according to the embodiment of the minimum configuration.

[0026] (composition) The dipole antenna 1 of this embodiment includes a dipole 20 having a total length L corresponding to the wavelength of the center frequency of the frequency band in use. The dipole 20 has a pair of elements 21 and 22 that are inclined at a predetermined inclination angle θ from a reference plane Sq that passes through a feed point Q toward a front direction D that is perpendicular to the reference plane Sq.

[0027] (Action and effect) The dipole antenna 1 of this embodiment includes a dipole 20 having a total length L corresponding to the wavelength of the center frequency of the frequency band in use. The dipole 20 has a pair of elements 21 and 22 that are inclined at a predetermined inclination angle θ from a reference plane Sq that passes through a feed point Q toward a front direction D that is perpendicular to the reference plane Sq. By adjusting the relationship between the total length L and the inclination angle θ of the dipole 20, radio waves over a wide frequency band can be received while suppressing an increase in directivity. Therefore, by using this dipole antenna, it is possible to provide an antenna and radio wave direction finder with a simple structure that can receive radio waves over a wide frequency band and has directivity that is close to omnidirectional, without the need to combine multiple types of antenna systems with low directivity to cover a wide frequency band.

[0028] Although the embodiment of the present disclosure has been described above, this embodiment is shown as an example and is not intended to limit the scope of the present disclosure. This embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the present disclosure. [Explanation of symbols]

[0029] 1. Dipole antenna 10 pillars 20 Dipole 21,22 elements 21c, 22c curl section 21e,22e Tip 23 Support arm 100 Radio direction finding device D Front direction L total length Q Power supply point r radius of curvature Sq reference plane α central angle θ Tilt angle

Claims

1. a dipole having a total length corresponding to the wavelength of the center frequency of the frequency band in use, The dipole has a pair of elements inclined at a predetermined inclination angle from a reference plane passing through a feed point to a front direction perpendicular to the reference plane, The dipole has a curled portion at its tip that is curved so as to be convex toward the front. Dipole antenna.

2. the total length corresponds to 0.5 or more and 1.5 or less wavelengths of the center frequency, 2. The dipole antenna according to claim 1, wherein the tilt angle is equal to or greater than 10 degrees and equal to or less than 45 degrees.

3. 2. The dipole antenna according to claim 1, wherein the radius of curvature of the curled portion is 0.02 to 0.3 wavelengths of the center frequency of the frequency band used.

4. The dipole antenna according to claim 1 , wherein a central angle of the curled portion is equal to or greater than 30° and equal to or less than 180°.

5. A radio wave direction finder comprising the dipole antenna according to any one of claims 1 to 4.

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