JP4689503B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device in a mobile communication base station, and more particularly to a small antenna device used in a weak electric field area.

  Currently, small antennas are arranged so that mobile phones can be used in weak electric field areas where radio field strength is weak from mobile communication base stations. There are roughly two types of antenna devices used for these: an antenna device equipped with a booster device and an antenna device equipped with a parasitic antenna.

  An antenna device including a booster device can provide a service to a certain wide area. On the other hand, an antenna device including a parasitic antenna has low transmission power, and a mobile phone may not be able to receive radio waves unless it is in the vicinity of the antenna device. For this reason, for example, an antenna device described in Patent Document 1 is known as an antenna device provided with a parasitic antenna. This antenna apparatus includes a cylindrical reflector below the dipole antenna, and prevents the electric field strength at the end of the service area from being reduced.

The configuration of the antenna device and the directivity of the antenna device will be described with reference to the drawings. FIG. 8 is a configuration diagram showing a specific configuration of the antenna device. As shown in FIG. 8, this antenna device has a configuration in which a reflector 31 is disposed below the dipole antenna 11 in the z-axis direction. FIG. 9 illustrates the directivity of the antenna device. FIG. 9A is a diagram showing the directivity pattern Eθ in the vertical plane, and FIG. 9B is a diagram showing the directivity pattern Eθ in the horizontal plane of the θ component. As shown in FIG. 9A, a null point (dent) is formed in the z-axis (vertical) direction, and it can be seen that the radio wave is weak in this direction. In addition, it turns out that the directivity in a horizontal surface is equal as shown in FIG.9 (b).
JP 2004-96207 A

  However, an antenna device provided with a booster device has a problem that its configuration is complicated or expensive. Further, when the dipole antenna is arranged on the z axis (vertical axis), the directivity indicated by the directivity pattern in the ± z axis direction becomes a very low value. Furthermore, in the antenna apparatus provided with the parasitic antenna described in Patent Document 1, the side lobe level can be suppressed, but the side lobe level cannot be increased. That is, as shown in FIG. 9A, a null point is formed in the directivity pattern in the z-axis direction, and there is a problem if the radio wave is weak in this z-axis direction.

  Accordingly, in order to solve the above-described problems, an object of the present invention is to provide an antenna device that can increase the side lobe level when a parasitic antenna is used.

  In order to solve the above-described problems, an antenna device of the present invention is disposed in parallel with a dipole antenna, a reflector disposed in a horizontal plane below the vertical axis of the dipole antenna, and a vertical axis of the dipole antenna. And one or a plurality of C-type parasitic elements arranged with an interval of 0.33λ (λ: wavelength) with respect to the dipole antenna.

  Further, the antenna device of the present invention is disposed in parallel with the monopole antenna, the reflector disposed in the horizontal plane direction below the vertical axis of the monopole antenna, and the vertical axis of the monopole antenna, And one or a plurality of half C-type parasitic elements arranged with an interval of 0.33λ (λ: wavelength) with respect to the monopole antenna.

  The antenna device configured as described above can direct the main beam in the side lobe direction in the directivity pattern, and can sufficiently provide the wireless communication service even at the service area end. Moreover, by adopting a monopole antenna, it can contribute to size reduction as a parasitic antenna.

  As described above, according to the present invention, the main beam can be directed in the side lobe direction in the directivity pattern, and the wireless communication service can be sufficiently provided even at the service area end.

  The present invention can be readily understood by considering the following detailed description with reference to the accompanying drawings shown for the embodiments. Subsequently, embodiments of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram illustrating a configuration of the antenna device 1 according to the first embodiment. The antenna device 1 is configured such that a dipole antenna 11 is disposed in the z-axis direction and a reflecting plate 31 is disposed below the dipole antenna 11. Further, C-type parasitic elements are arranged parallel to the z-axis direction of the dipole antenna 11 with an interval of 0.33λ (λ: wavelength). The C-type parasitic element is a circular parasitic element in which an opening is formed in one direction.

  In the present embodiment, the C-type parasitic element is arranged so as to surround the four sides of the dipole antenna 11. However, the present invention is not limited to this, and one C-type parasitic element is arranged in the dipole antenna 11. You may comprise as follows.

  FIG. 2 shows a directivity pattern of the antenna device 1 configured as described above. FIG. 2A is a diagram showing a directivity pattern in the vertical plane of the antenna device 1, and FIG. 2B is a diagram showing a directivity pattern in the horizontal plane. As shown in FIG. 2A, the directivity pattern (Eθ indicating the θ component and Eφ indicating the φ component) of the antenna device 1 is compared with the directivity pattern shown in FIG. It can be seen that the null point in the axial direction is improved and the main beam is directed in the sidelobe direction. In addition, as shown in FIG. 2B, the directivity pattern in the horizontal plane forms a pattern that does not change much compared to the conventional configuration (FIG. 9B).

  Next, the antenna device 2 according to the second embodiment will be described. FIG. 3 is a schematic configuration diagram of the antenna device 2 according to the second embodiment. As shown in FIG. 3, the antenna device 2 is configured such that a monopole antenna 12 is disposed in the z-axis direction and a reflector 32 is disposed below the monopole antenna 12. Furthermore, in parallel to the z-axis direction of the monopole antenna 12, half C-type parasitic elements are arranged with an interval of 0.33λ (λ: wavelength). The half C-type parasitic element has a shape obtained by halving a circular parasitic element.

  FIG. 4 shows a directivity pattern of the antenna device 2 configured as described above. FIG. 4A is a diagram showing a directivity pattern in the vertical plane of the antenna device 2, and FIG. 4B is a diagram showing a directivity pattern in the horizontal plane. As shown in FIG. 4A, the directivity pattern (Eθ indicating the θ component and Eφ indicating the φ component) of the antenna device 2 is the directivity pattern shown in FIGS. 2A and 9A. It can be seen that the null point in the ± z-axis direction is improved and the main beam is directed in the sidelobe direction. Further, as shown in FIG. 4B, the directivity pattern in the horizontal plane is compared with the directivity pattern of the first embodiment (FIG. 2B) and the conventional configuration (FIG. 9B). The pattern does not change so much. Further, as can be seen from the VSWR in the antenna device 2 shown in FIG. 5, since the impedance is (43.685 + 1.09j) ohms, which is relatively close to 50 ohms, this antenna configuration has no problem in impedance matching. I understand.

  Next, the influence of the reflection characteristics in the antenna device 2 when the antenna of the mobile device is in the vicinity of the antenna device 2 will be described. Here, as an antenna configuration at that time, as shown in FIG. 6, a dipole antenna 41 arranged in parallel to the xy plane of the antenna device 2 is arranged by being rotated by −45 ° from the x axis. FIG. 7 shows measured values of S parameters, which are explained as a result of measuring the mutual coupling characteristics between the antenna of the mobile device and the antenna of the base station provided with a parasitic element. At this time, the distance between the port 1 and the port 2 indicating the relationship of the antennas is 100 mm. As shown in FIG. 7, at a frequency of 1.78 GHz, the input / output ratio in the coupling between transmission and reception is −10 dB (location indicated by MARKER3), and even if the distance between the transmission and reception antennas is close, the respective reflection characteristics It turns out that it is hardly influenced by.

  As described above, the C-type parasitic element 21 is arranged apart from the dipole antenna 11 by about 0.33λ, and the half-C type parasitic element 22 is arranged apart from the monopole antenna 12 by about 0.33λ, It can be seen that the main beam can be directed in the lobe direction, and even if the distance between the transmitting and receiving antennas is close, the loss of reflection characteristics is not so much. In addition, the monopole antenna can contribute to the miniaturization of the parasitic antenna.

It is a schematic block diagram which shows the structure of the antenna device 1 of 1st Embodiment. 2 is a diagram showing a directivity pattern of the antenna device 1. FIG. It is a schematic block diagram of the antenna apparatus 2 of 2nd Embodiment. It is a figure which shows the directivity pattern of the antenna apparatus. It is a figure which shows VSWR in the antenna apparatus 2. FIG. It is a schematic block diagram of the antenna apparatus 2 when the antenna of a mobile apparatus adjoins. It is a figure which shows S parameter. It is a schematic block diagram which shows the structure of the conventional antenna apparatus. It is a figure which shows the directivity pattern of the conventional antenna device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna device, 2 ... Antenna device, 11 ... Dipole antenna, 12 ... Monopole antenna, 21 ... Type parasitic element, 22 ... Type parasitic element, 31 ... Reflector, 32 ... Reflector, 41 ... Dipole antenna

Claims (2)

A dipole antenna,
A reflector disposed in a horizontal plane below the vertical axis of the dipole antenna;
One or more C-type parasitic elements that are arranged in parallel to the vertical axis of the dipole antenna and are spaced 0.33λ (λ: wavelength) from the vertical axis of the dipole antenna;
An antenna device comprising: With a monopole antenna,
A reflector disposed in a horizontal plane below the vertical axis of the monopole antenna;
One or more half-C parasitic elements arranged in parallel to the vertical axis of the monopole antenna and arranged with a spacing of 0.33λ (λ: wavelength) with respect to the vertical axis of the monopole antenna When,
An antenna device comprising:

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