JP4133712B2 - Directional antenna - Google Patents

Description

  The present invention relates to a directional antenna for mobile communication base stations, and more particularly to a directional antenna with improved directivity and wind receiving load.

  2. Description of the Related Art Conventionally, a directional antenna using vertically polarized waves is known as a directional antenna for mobile communication base stations (see, for example, Patent Document 1).

  FIG. 8 is a perspective view showing a configuration example of a conventional directional antenna using vertically polarized waves. In FIG. 8, 21 is an arm, and 22a and 22b are screen arms attached to the arm 21 in an inverted corner shape. Near the tip of the arm 21, a radiating element 23 having a length of about λ / 2 (λ: wavelength) with respect to the operating frequency is vertically attached. In addition, one reflection element 24 is vertically attached to the apex position A of the screen arms 22a and 22b, and a plurality of reflection elements 24 are attached along the screen arms 22a and 22b at a predetermined interval. The length of the reflection element 24 is about 1λ, the distance between adjacent reflection elements 24 is about 0.15λ, and the angle of the reverse corner formed by the screen arms 22a and 22b is about 260 degrees.

  As described above, the conventional directional antenna includes a radiating element 23 having a length of about λ / 2 with respect to a used frequency, and a plurality of radiating elements 23 arranged in parallel in reverse corners separated from the radiating element 23 by a predetermined distance. This is composed of seven (seven shown) reflective elements 24.

FIG. 9 shows the vertical polarization horizontal plane directivity of the conventional directional antenna. FIG. 9 shows polar coordinates on the dB scale. In the conventional directional antenna, the beam width of the vertical polarization horizontal plane directivity is set to about ± 90 degrees, and the forward / backward ratio characteristic in the 180 degree direction is set to about 20 dB.
Japanese Utility Model Publication No. 61-28403

  However, the conventional directional antenna has a problem that the wind receiving load is large because the length of the reflection element 24 is set to be very long as 1λ and the number of the reflection elements 24 to be configured is large.

  Further, when the beam width of directivity is set to approximately ± 90 degrees, there is a problem that directivity in the 0 degree direction falls by 1.5 to 2 dB.

  Furthermore, with conventional directional antennas, if the sensitivity is as high as possible in directions other than 180 degrees and an attempt is made to obtain good communication characteristics, the sensitivity of directivity is suppressed by a width of about 180 degrees ± 30 degrees. Therefore, there is a problem that it is impossible to increase the sensitivity in the direction of 150 degrees or in the direction of 210 degrees.

  In addition, in order to attach the reflective element to the apex position A of the inverted corner-shaped arrangement, there is a problem that a complicated support structure is required, and the manufacturing cost is increased.

  The present invention has been made to solve the above-described problems. The number of reflecting elements arranged in an inverted corner shape can be reduced to facilitate installation, reduce wind receiving load, and simplify the support structure of the reflecting elements. An object of the present invention is to provide a directional antenna that can be reduced in cost.

A directional antenna according to a first aspect of the present invention includes an element mounting arm, a radiating element using a dipole antenna having a length of about a half wavelength attached in the vicinity of the tip of the arm, and a screen arm mounting bracket on the arm. and two screens arms attached to opposite corner shape with respect to the radiating element, attached by at least two in each of the two screens arms, are two intervals which are provided on the same screen arm about the 0 A plurality of reflective elements having a predetermined length and arranged in parallel with the radiating element in an inverted corner shape at intervals of 18 wavelengths, and the inverted corner-shaped screen arm has a vertex position from the radiating element at a predetermined value. The plurality of reflecting elements are provided at positions apart from each other except for the vertex position of the screen arm.

  According to a second aspect of the present invention, in the directional antenna according to the first aspect of the present invention, the length of the reflective element arranged in an inverted corner shape is set to about 0.7 wavelength.

  According to a third aspect of the present invention, in the directional antenna according to the first aspect of the present invention, the reflective elements arranged in an inverted corner shape are composed of four reflective elements, the two reflective elements arranged on the inner side and the outer side arranged. The two reflecting elements are set to different lengths.

  According to the present invention, it is possible to reduce the number of reflective elements arranged in an inverted corner shape while ensuring the vertical polarization horizontal plane directivity beam width of about ± 90 degrees and the front-rear ratio characteristic of about 20 dB. Wind load can be reduced. In addition, when the reflective element is arranged in the reverse corner shape, it is not necessary to arrange the reflective element at the apex position of the reverse corner, and the support structure of the reflective element can be made relatively simple. Costs can be reduced compared to conventional antennas, such as transport packaging size.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a perspective view showing a configuration example of a vertically polarized directivity antenna according to the first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes an arm, and screen arms 2 a and 2 b are attached to the arm 1 by a screen arm attachment fitting 3 in an inverted corner shape when viewed from the directing direction. The angle α that forms the reverse corner of the screen arms 2a and 2b is set in the range of 230 to 260 degrees, for example, preferably about 240 degrees.

  Near the tip of the arm 1, a radiating element 4 such as a dipole antenna is mounted in the vertical direction by an element mounting bracket 5. The length of the radiating element 4 is set to a length of about λ / 2 (λ: wavelength) with respect to the operating frequency. When a dipole antenna is used as the radiating element 4, the central portion is insulated by the insulating material 10. The radiating element 4 is provided with a feeding terminal 11.

  The screen arms 2a and 2b, except for the apex position A, have a plurality of, for example, four reflecting elements 6a1, 6a2, 6b1, and 6b2 that are parallel to each other in the vertical direction by the element mounting bracket 7. Mounted. In this case, the reflective elements 6a1 and 6a2 are disposed on the inner side, and the reflective elements 6b1 and 6b2 are disposed on the outer side. The lengths of the four reflecting elements 6a1, 6a2, 6b1, and 6b2 are set to about 0.7λ.

  Next, the positional relationship between the radiating element 4 and the reflecting elements 6a1, 6a2, 6b1, and 6b2 will be described with reference to FIG. FIG. 2 is a diagram schematically showing the directional antenna shown in FIG. 1 as seen from above.

  As shown in FIG. 2, the distance from the inner-side reflecting elements 6a1 and 6a2 to the outer-side reflecting elements 6b1 and 6b2 arranged in an inverted corner shape by the screen arms 2a and 2b is d1, and the inner-side reflecting element 6a1 and The distance between the reflecting elements 6a1 and 6a2 and the radiation element 4 is d3, the distance between the reflecting elements 6b1 and 6b2 arranged outside is d4, and the line connecting the reflecting elements 6b1 and 6b2. When the distance from the radiating element 4 is d5, the values of d1 to d5 are set as follows.

d1: about 0.18λ
d2: about 0.32λ
d3: about 0.33λ
d4: about 0.64λ
d5: about 0.42λ
Further, as described above, the length of the radiating element 4 is about λ / 2, the length of the reflecting elements 6a1, 6a2, 6b1, and 6b2 is about 0.7λ, and the angle of the reverse corner formed by the screen arms 2a and 2b, That is, the angle α of the reverse corner formed by the reflective elements 6a1 and 6b1 and the reflective elements 6a2 and 6b2 is about 240 degrees. The directional antenna is used in a 150 MHz band, a 400 MHz band, or the like, for example.

  FIG. 3 shows the vertical polarization horizontal plane directivity of the directional antenna according to the first embodiment. FIG. 3 shows polar coordinates on the dB scale. As is apparent from the figure, the directivity beam width is about ± 90 degrees, and the forward / backward ratio characteristic in the 180 degree direction is about 20 dB.

  Compared to conventional directional antennas, it is possible to reduce the number of reflective elements arranged in an inverted corner shape while maintaining directional characteristics to four, and the length of the reflective elements can be shortened. A directional antenna with a small wind load can be realized.

  Further, in the horizontal plane directivity, 120 to 150 degrees and 210 to 240 degrees are approximately 3 dB higher than the conventional directional antenna, and 90 to 150 degrees and 210 to 270 degrees are more sensitive than the conventional directional antenna. An antenna can be provided.

(Second Embodiment)
Next, a directional antenna according to the second embodiment of the present invention will be described.
FIG. 4 is a perspective view showing a configuration example of a directional antenna according to the second embodiment of the present invention. The directional antenna according to the second embodiment uses reflection elements 16a1 and 16a2 having a length of about 0.7λ instead of the inner reflection elements 6a1 and 6a2 in the first embodiment shown in FIG. The reflective elements 16b1 and 16b2 having a length of about 0.6λ are used instead of the external reflective elements 6b1 and 6b2.

  Then, as shown in FIG. 5, the distance between the reflective elements 16a1 and 16a2 arranged in an inverted corner by the screen arms 2a and 2b to the reflective elements 16b1 and 16b2 arranged outside is d1, and the reflective elements arranged inside The distance between 16a1 and 16a2 is d2, the distance between the line connecting the reflection elements 16a1 and 16a2 and the radiation element 4 is d3, the distance between the reflection elements 16b1 and 16b2 arranged outside is d4, and the reflection elements 16b1 and 16b2 are connected. When the distance between the line and the radiating element 4 is d5, the values of d1 to d5 are set as follows.

d1: about 0.18λ
d2: about 0.32λ
d3: about 0.34λ
d4: about 0.64λ
d5: about 0.43λ
The length of the radiating element 4 is about λ / 2, and the angle α of the reverse corner formed by the reflecting elements 16a1 and 16b1 and the reflecting elements 16a2 and 16b2 is about 240 degrees.

  FIG. 6 shows the vertical polarization horizontal plane directivity of the directional antenna according to the second embodiment. The beam width of the directivity is about ± 90 degrees and the forward / backward ratio characteristic in the 180 degree direction is about 20 dB. ing.

  In the directional antenna according to the second embodiment, the lengths of the reflection elements 16b1 and 16b2 arranged on the outside can be made shorter than in the case of the first embodiment.

  FIG. 7 shows the directional antenna according to the second embodiment in which the lengths of the two reflecting elements 16a1 and 16a2 are set to about 0. The vertical polarization horizontal plane directivity is shown when the length of the two reflecting elements 16b1 and 16b2 arranged at 7λ and outside is set to about 0.6λ and the element spacings d1 to d5 are set as follows. Is.

d1: about 0.18λ
d2: about 0.42λ
d3: about 0.38λ
d4: about 0.74λ
d5: about 0.47λ
As shown in FIG. 7, when the forward / backward ratio characteristic in the 180 degree direction is about 15 dB, the directivity deviation can be made about 3 dB in the range of 0 ± 120 degrees in directivity. In other words, the sensitivity is suppressed so as not to interfere with a specific specific direction on the horizontal plane directivity, or to prevent the interference, and it can be used like a non-directional antenna except for a specific direction ± 60 degrees. It becomes possible.

  By adopting the configuration shown in the above embodiment, the vertical polarization horizontal plane directivity beam width of about ± 90 degrees and the front-rear ratio characteristic of about 20 dB are secured, and the reflection element arranged in an inverted corner shape is used. The number can be reduced to four and the wind receiving load can be reduced.

  In addition, when the reflective element is arranged in the reverse corner shape, it is not necessary to arrange the reflective element at the apex position A of the reverse corner, and the support structure of the reflective element can be made relatively simple, and the material, processing, and incorporation Costs can be reduced compared to conventional antennas, such as transport packaging size.

  Further, in the vertical polarization horizontal plane directivity, the angle adjustment for suppressing directivity sensitivity can be made as narrow as possible, and the remaining angles can reduce the directivity deviation like an omnidirectional antenna. That is, it is possible to give sensitivity to as wide a range as possible while suppressing jamming interference as a relay station antenna for a system or the like using the same frequency.

  When a dipole antenna is used as the radiating element, it can be used as a broadband antenna having a bandwidth of about 5% while maintaining the above directivity.

  In addition, if a vertically polarized horizontal plane element such as a sleeve antenna or a whip antenna is used as the radiating element, a directional antenna having similar characteristics can be obtained.

  In the above embodiment, the case where four reflective elements are used has been described, but it is needless to say that a larger number of reflective elements may be used.

  Moreover, although the case where it implemented as a directional antenna of a vertically polarized wave was shown in the said embodiment, it can be used also as a directional antenna for horizontally polarized waves.

  Further, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage.

1 is a perspective view of a directional antenna according to a first embodiment of the present invention. It is a figure which shows the positional relationship of the radiation element and reflection element of the directional antenna which concerns on the same embodiment. It is a figure which shows the vertical polarization horizontal surface directivity of the directional antenna which concerns on the same embodiment. It is a perspective view of the directional antenna which concerns on 2nd Embodiment of this invention. It is a figure which shows the positional relationship of the radiation element and reflection element of the directional antenna which concerns on the same embodiment. It is a figure which shows the vertical polarization horizontal surface directivity of the directional antenna which concerns on the same embodiment. It is a figure which shows the vertical polarization horizontal plane directivity in the other example of a setting of the directional antenna which concerns on the same embodiment. It is a perspective view which shows the structure of the conventional directional antenna. It is a figure which shows the vertical polarization horizontal plane directivity of the conventional directional antenna.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Arm, 2a, 2b ... Screen arm, 3 ... Screen arm mounting bracket, 4 ... Radiation element, 5 ... Element mounting bracket, 6a1, 6a2 ... Reflective element, 6b1, 6b2 ... Reflective element, 7 ... Element mounting bracket, 10 ... Insulating material, 11 ... Feed terminal, 16a1, 16a2 ... Reflective element, 16b1.16b2 ... Reflective element.

Claims (3)

An element mounting arm, a radiating element using a dipole antenna having a length of about half wavelength, which is mounted near the tip of the arm, and a reverse arm shape with respect to the radiating element by a screen arm mounting bracket on the arm and two screens arms mounted, the mounted by at least two on each two screen arms, the reversed corners shaped with two spacing interval of about 0.18 wavelengths provided in the same screen arm A plurality of reflective elements of a predetermined length arranged in parallel with the radiating element,
The inverted corner-shaped screen arm is provided with a vertex position at a predetermined distance from the radiating element, and the plurality of reflecting elements are arranged excluding the vertex position of the screen arm. .   The directional antenna according to claim 1, wherein a length of the reflective elements arranged in the inverted corner shape is set to about 0.7 wavelength.   The reflection element arranged in the reverse corner shape is composed of four reflection elements, and the two reflection elements arranged inside and the two reflection elements arranged outside are set to different lengths. The directional antenna according to claim 1.

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