JP5795016B2 - Directional antenna and small cell base station - Google Patents

Description

  The present invention relates to an antenna of a small cell base station.

  In recent mobile communication systems, together with a macro cell base station that covers an area with a radius of several hundred m to several km, an area with a radius of several m to several tens of m that is narrower than the cell size of a normal base station is generally covered. Small small cell base stations are in operation. Small cell base stations are installed in places where radio waves from macro cell base stations are difficult to reach, such as in buildings, houses, and underground malls. Even in a place where the macrocell radio waves reach, it may be installed for the purpose of improving communication quality and communication speed. The small cell base station can be easily installed even in a complicated crowded environment, and can provide a stable radio wave environment to the mobile terminal. Conventionally, an omnidirectional antenna is generally used for an antenna used in a small cell base station.

  However, since an omnidirectional antenna radiates radio waves in all directions, radio waves from a small cell base station installed indoors may leak out outdoors. Such leaked radio waves are not preferable because they induce unnecessary handover processing by an outdoor mobile terminal. If the output of a small cell base station is reduced to suppress leaked radio waves from indoors to the outdoors, it will be difficult for radio waves to reach the entire indoor area, resulting in a dead band, or from an outdoor macro cell base station. May penetrate indoors, which may cause interference with the small cell base station. In particular, in LTE (Long Term Evolution), when the output is lowered, the communication speed is lowered. Therefore, an improvement for raising the output while suppressing leakage radio waves to the outdoors is desired.

  Therefore, an object of the present invention is to propose a directional antenna and a small cell base station that can radiate radio waves indoors with sufficient output while suppressing leaked radio waves to the outdoors.

In order to solve the above-mentioned problems, the directional antenna according to the present invention shields an antenna body disposed around an indoor window glass so that the main radiation direction of radio waves faces indoors, and leaks of radio waves to the outside. And a radio wave shielding member disposed on a part of the window glass . By placing the antenna body around the window glass so that the main radiation direction of the radio wave faces indoors, it is possible to prevent the main lobe from directly passing through the window glass and leaking outside. Thereby, it is possible to radiate radio waves with sufficient output indoors while suppressing leaked radio waves to the outdoors. Here, the periphery of the window glass means an attachment position of the antenna body where the main lobe does not directly leak through the window glass and leak outside. In addition, the radio wave shielding member placed on a part of the window glass to shield the leakage of radio waves to the outside suppresses radiation patterns such as back lobes and side lobes to the outside and outputs the directional antenna. Can be raised. In addition, by arranging the antenna body at a position and angle where the main lobe directly passes through the window glass and does not leak outside, the range occupied by the radio wave shielding member is the back lobe and side lobe out of the area of the window glass. The minimum range that can suppress the leakage of the radiation pattern to the outside is sufficient.

  The antenna body may further include a reflector for adjusting the front-back ratio. The higher the front-back ratio, the stronger the directivity and the radiation pattern that is less likely to leak outdoors.

  A small cell base station according to the present invention includes the above-described directional antenna. The small cell base station can radiate radio waves with sufficient output indoors while suppressing leaked radio waves to the outdoors.

  ADVANTAGE OF THE INVENTION According to this invention, an electromagnetic wave can be radiated | emitted with sufficient output indoors, suppressing the electromagnetic wave leaked outdoors.

It is sectional drawing of the directional antenna for small cell base stations concerning this embodiment. It is explanatory drawing which shows the example of arrangement | positioning of the small cell base station concerning this embodiment. It is explanatory drawing which shows the example of arrangement | positioning of the small cell base station concerning this embodiment. It is explanatory drawing which shows the example of arrangement | positioning of the small cell base station concerning this embodiment. It is sectional drawing of the antenna main body for small cell base stations concerning this embodiment.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view of a directional antenna 10 for a small cell base station according to this embodiment. The directional antenna 10 includes an antenna body 20 having strong directivity in the main radiation direction 90. In the directional antenna 10, unlike the omnidirectional antenna having an isotropic radiation pattern, the RF energy is concentrated in the main radiation direction 90. As a result, the main lobe 61 is greatly pushed toward the main radiation direction 90. The back lobe 62 on the back side is relatively small. The antenna body 20 is arranged so that the main radiation direction 90 of the radio wave 60 faces indoors, and consideration is given so that the main lobe 61 does not directly pass through the window glass 40 and leak to the outdoors. By adjusting the gain of the directional antenna 10 according to the indoor shape and the indoor area, the half-value width can be adjusted, and an optimal communication area can be formed.

  However, the radio wave 60 radiated from the antenna body 20 includes a radiation pattern called a back lobe 62 or a side lobe 63 in addition to the main lobe 61. Since the back lobe 62 and the side lobe 63 may leak through the window glass 40 to the outside, the directional antenna 10 shields the radiation pattern such as the back lobe 62 and the side lobe 63 from leaking to the outside. A radio wave shielding member 30 is further provided. As a result, the output of the antenna body 20 can be increased, and the radio wave 60 can be radiated indoors with a sufficient output while suppressing leaked radio waves to the outdoors. The radio wave shielding member 30 is formed of an electromagnetic shield film (for example, glass cloth reinforced aluminum foil) that reflects or absorbs the radio wave 60. The ratio between the energy of the main lobe 61 and the energy of the back lobe 62 is called the front back ratio, and the higher the front back ratio, the higher the radiation output to the indoor while suppressing leaking electric waves to the outside. Can do. From the viewpoint of improving the front-back ratio, it is more effective that the electromagnetic wave shielding member 30 has a function of reflecting rather than a function of absorbing the radio wave 60.

  For example, when the directional antenna 10 is installed at a position where the main radiation direction 90 faces the window glass 40 (for example, an inner wall facing the window glass 40), the main lobe 61 passes directly through the window glass 40 and is outdoors. Therefore, it is necessary to arrange the radio wave shielding member 30 so as to cover the entire window glass 40. On the other hand, since the antenna body 20 itself is installed on the window glass 40 so that the main radiation direction 90 of the radio wave 60 faces indoors, the main lobe 61 can be prevented from passing directly through the window glass 40. The range which the shielding member 30 occupies is sufficient in the minimum range which can suppress the leakage to the outdoors of radiation patterns, such as the back lobe 62 and the side lobe 63, among the areas of the window glass 40. The radio wave shielding member 30 can be stuck and fixed so as to be interposed between the antenna body 20 and the window glass 40 by using, for example, a double-sided tape.

  FIG. 2 is an explanatory diagram illustrating an arrangement example of the small cell base stations 50 according to the present embodiment. The radio wave shielding member 30 is disposed so as to cover a part of the window glass 40. The antenna main body 20 is disposed so as to overlap the radio wave shielding member 30. What is necessary is just to adjust suitably the magnitude | size and shape of the electromagnetic wave shielding member 30 according to the radiation pattern of the directional antenna 10 so that the leakage electric wave to the outdoors can be suppressed. The small cell base station 50 is connected to the directional antenna 10 via the cable 70. However, the arrangement location of the antenna body 20 is not necessarily limited to the window glass 40. For example, the antenna body 20 is placed at a position and an angle at which the main lobe 61 does not directly pass through the window glass 40 and leak outside. It only has to be attached. The mounting position of the antenna main body 20 that satisfies such conditions is, for example, a peripheral portion of the window glass 40 such as an indoor ceiling or an inner wall. For example, as shown in FIG. 3, the main radiation direction 90 of the radio wave 60 is directed indoors, and the main lobe 61 passes through the window glass 40 directly and does not leak to the outdoors. The antenna body 20 may be attached. Even with such an arrangement, it is possible to prevent the main lobe 61 from directly passing through the window glass 40, so that the radio wave shielding member 30 can prevent the radiation pattern such as the back lobe 62 and the side lobe 63 from leaking to the outside. It is sufficient to install it on a part of the glass 40. Note that the antenna body 20 and the small cell base station 50 do not necessarily have to be separate bodies, and may have an integrated configuration, for example, as shown in FIG.

  FIG. 5 is a cross-sectional view of the antenna body 20 according to the present embodiment. The antenna body 20 includes an antenna element 21, a reflection plate 22 for adjusting the front-back ratio, and a housing 23 that houses the antenna element 21 and the reflection plate 22. By improving the front-back ratio by utilizing the reflection of radio waves by the reflecting plate 22, it is possible to increase the directivity to the indoors and obtain a radiation pattern that hardly leaks to the outside.

  The directional antenna 10 according to the present embodiment includes the indoor window glass 40 or the antenna body 20 disposed in the periphery thereof so that the main radiation direction 90 of the radio wave 60 faces indoors. It is possible to effectively avoid leakage through the glass 40 directly. Thereby, it is possible to radiate radio waves with sufficient output indoors while suppressing leaked radio waves to the outdoors. Further, since the directional antenna 10 includes the radio wave shielding member 30 disposed in a part of the window glass 40 so that the radio wave 60 does not leak to the outdoors, the radiation pattern of the back lobe 62, the side lobe 63, etc. Leakage to the outdoors can be effectively suppressed, and the output of the directional antenna 10 can be increased. In addition, since the transmission output of the small cell base station 50 can be increased, it is possible to reduce interference of radio waves penetrating from the outside to the inside (for example, radio waves from the macro cell base station). In particular, when the small cell base station 50 is compatible with the LTE system, the transmission output can be increased indoors while preventing leakage of radio waves to the outdoors, so that an improvement in communication speed can be expected.

DESCRIPTION OF SYMBOLS 10 ... Directional antenna 20 ... Antenna main body 21 ... Antenna element 22 ... Reflector plate 23 ... Case 30 ... Radio wave shielding member 40 ... Window glass 50 ... Small cell base station 60 ... Radio wave 61 ... Main lobe 62 ... Back lobe 63 ... Side Lobe 70 ... Cable 80 ... Ceiling 90 ... Main radiation direction

Claims (2)

A directional antenna for a small cell base station installed indoors,
An antenna element, a reflecting plate having a concave curved surface that covers a side surface and a back surface of the antenna element in order to adjust a front-back ratio of radio waves radiated from the antenna element, and a housing that houses the antenna element and the reflecting plate An antenna body that is disposed around the indoor window glass so that a main radiation direction of the radio wave faces the indoor,
A directional antenna comprising an electromagnetic shielding film adhered and fixed to a part of the window glass so as to shield leakage of the radio wave to the outdoors. A small cell base station comprising the directional antenna according to claim 1 .

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