JP2007329666A - Array antenna device - Google Patents

Abstract

There is a need to suppress a side lobe level in an elevation angle direction in an antenna directivity characteristic in a vertical plane. Suppress traditional side lobes.
An array antenna apparatus in which M antenna elements are arranged in a predetermined direction: the tilt angle θ2 of N antenna elements at one end of the M antenna elements and the other end The tilt angle θ3 of a certain N antenna elements is different from the tilt angle θ1 of (M−2N) antenna elements located between one end and the other end.
[Selection] Figure 2

Description

  The present invention relates to an array antenna device, and more particularly to an array antenna device characterized in that the tilt angle of the antenna element of the antenna block at one end and the other end is different from the tilt angle of the antenna element of the antenna block at the intermediate portion.

  An example of a conventional base station antenna device for a mobile communication system is schematically shown in FIG. An antenna device 10 shown in FIG. 1 is an array antenna composed of M antenna elements 1 arranged vertically. The M antenna elements have the same tilt angle. In general, a phase shifter is connected to each antenna element in order to control the radiation direction in the vertical plane of the antenna.

  It is desired that a base station antenna of a mobile communication system suppresses interference with adjacent zones in order to ensure quality and subscriber capacity. If the main beam direction of the antenna is inclined downward to provide a depression angle, side lobes above the main beam direction cause interference. Also, with the rise in urban areas, side lobes in the elevation direction (the sky direction, ie all directions above the horizontal direction) cause interference for mobile stations and the like that are higher than the base station antenna. Become.

  Accordingly, it is necessary to suppress the side lobe level in the elevation direction (the sky direction, that is, all directions above the horizontal direction) in the directivity characteristics of the antenna in the vertical plane. A Chebyshev distributed array antenna exists as a conventional antenna with suppressed side lobes. However, since it is necessary to change the excitation amplitude value depending on the position of the radiating element, the design of the power distributor becomes very complicated, which is not preferable.

  Therefore, the present invention solves such problems of the conventional antenna. In the array antenna arranged in the vertical direction, the tilt angle of a predetermined number of elements at the upper end and the lower end is set to be equal to that of the antenna element at the middle. The side lobe level in the elevation direction is easily reduced by increasing the tilt angle as compared with the tilt angle.

  An array antenna apparatus according to a feature of the present invention is an array antenna apparatus in which M antenna elements are arranged in a predetermined direction: of N antenna elements at one end of the M antenna elements. The tilt angle θ2 and the tilt angle θ3 of the N antenna elements at the other end are different from the tilt angle θ1 of the (M−2N) antenna elements located between the one end and the other end. Features.

  It is desirable that the ratio N / M of the number N of antenna elements at one end and the multi-end with respect to the total number M of antenna elements is between 0.05 and 0.2.

  Further, it is desirable that the ratio N / M of the number N of antenna elements at one end and the multi-end with respect to the total number M of antenna elements is approximately 0.1.

  The θ1, θ2, and θ3 are preferably θ1 <θ2 <θ3.

  Furthermore, it is desirable that θ1, θ2, and θ3 satisfy θ1 <θ2 = θ3.

  A phase shifter is connected to each antenna element, and the phase of the input excitation power to the antenna element can be adjusted.

  In the array antenna apparatus, the predetermined direction may be a vertical direction. The one end may be the uppermost part and the other end may be the lowermost part.

  According to the antenna device according to the embodiment of the present invention, the side lobe level in the elevation angle direction can be suppressed in the directivity characteristics in the vertical plane.

  Hereinafter, embodiments of an antenna device according to the present invention will be described with reference to the drawings.

[Example 1]
FIG. 2 schematically shows an antenna device 20 according to the first embodiment of the present invention. The antenna device 20 is an array antenna including M antenna elements arranged in the vertical direction (for example, M = 60, but is not limited thereto). The tilt angles (the depression angles, that is, the angles inclined downward with respect to the horizontal direction) of the uppermost N antenna elements and the lowermost N antenna elements are θ2 and θ3, respectively. In addition, the tilt angle (the depression angle) of the (M−2N) antenna block elements located in the central portion between the uppermost portion and the lowermost portion is defined as θ1.

  The relationship between the tilt angles θ1, θ2, and θ3 is as follows.

θ1 <θ2 = θ3
By setting θ2 = θ3, an optimum effect can be obtained.

  Here, in an array antenna having M antenna elements (M = 20, 30, 40, 50 or 60), the ratio (N / M) of the number N of antenna elements having tilt angles θ2 and θ3 to M is changed. FIG. 3 shows the side lobe characteristics in the elevation angle direction when it is applied. The characteristics shown in FIG. 3 are obtained by computer simulation. The vertical axis in FIG. 3 indicates the maximum value of the side lobe level in the range of the elevation angle of 20 ° from the main beam direction to the sky direction, and the horizontal axis indicates N / M. As shown in the graph of FIG. 3, no matter what value M is, when N / M is between 0.05 and 0.2, the side lobe becomes small and M / N = 0. It was found that the side lobe level was minimized when 1.

Also, the directivity in the vertical plane of the antenna of Example 1 in the case of (N, M) = (2, 20) and in the case of (N, M) = (6, 60) is shown in FIGS. 4 and 5, respectively. Show. As shown in FIGS. 4 and 5, it can be seen that the sidelobe level in the sky direction is greatly improved in the antenna according to the first embodiment compared to the conventional antenna. Thus, according to the embodiment of the present invention, it can be seen that the sidelobe characteristics are greatly improved.
[Example 2]
FIG. 6 schematically shows an antenna device 60 according to the second embodiment of the present invention. The antenna device 60 has a configuration in which the phase shifter 4 is connected to each of the M antenna elements in the antenna 20 of the first embodiment. With such a configuration, it is possible to easily control the main beam direction, and it is possible to achieve a flexible area configuration.
[Example 3]
In the antenna device 20 according to the second embodiment of the present invention, a certain effect can be obtained even if θ2 and θ3 are not equal. Furthermore, it is known from computer simulation that θ1 <θ2 <θ3 is official.

  In each of the above embodiments, each antenna element is shown as a single antenna element having directivity. However, each element may be an antenna block composed of, for example, four antenna elements. In that case, it is possible to set the tilt angle of the antenna block by making the phases of the signals transmitted from the four elements different (for example, by inserting a phase shifter). It is also possible to set the tilt angle of the antenna block by providing a predetermined difference in the physical distance of the route from the cable to each of the four antenna elements. In this application, the term antenna element means an antenna element, an antenna block, or other antenna unit.

It is the schematic of the conventional base station antenna apparatus for mobile communications. It is the schematic of the antenna apparatus according to Example 1 of this invention. 6 is a graph showing side lobe level characteristics of the antenna device of Example 1. It is a graph which shows the vertical in-plane directivity in case M = 20 of the antenna apparatus of Example 1. It is a graph which shows the vertical in-plane directivity in the case of M = 60 of the antenna apparatus of Example 1. It is the schematic of the antenna apparatus according to Example 2 of this invention.

Explanation of symbols

20, 60 Antenna device 1 Antenna element 2 Feed cable 3 Antenna feed point 4 Phase shifter

Claims (8)

An array antenna device in which M antenna elements are arranged in a predetermined direction:
Among the M antenna elements, the tilt angle θ2 of the N antenna elements at one end and the tilt angle θ3 of the N antenna elements at the other end are located between the one end and the other end. An array antenna apparatus characterized by being different from a tilt angle θ1 of (M-2N) antenna elements. 2. The array antenna according to claim 1, wherein a ratio N / M of the number N of antenna elements at the one end portion and the multi-end portion to the total number M of antenna elements is between 0.05 and 0.2. apparatus. 3. The array antenna apparatus according to claim 2, wherein a ratio N / M of the number N of antenna elements at the one end portion and the multi-end portion to the total number M of antenna elements is approximately 0.1. The array antenna apparatus according to claim 1, wherein the θ1, θ2, and θ3 satisfy θ1 <θ2 <θ3. The array antenna apparatus according to claim 4, wherein the θ1, θ2, and θ3 satisfy θ1 <θ2 = θ3. The array antenna apparatus according to claim 1, wherein a phase shifter is connected to each antenna element, and the phase of input excitation power to the antenna element can be adjusted. The array antenna apparatus according to claim 1, wherein the predetermined direction is a vertical direction. The array antenna apparatus according to claim 7, wherein the one end is an uppermost part and the other end is a lowermost part.

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