JP3363008B2 - Antenna device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used in a wireless communication device. The present invention is suitable for use in a fixed wireless station or a mobile wireless station. The present invention relates to an antenna device having a one-beam directivity. The present invention relates to a directivity improving technique.

[0002]

2. Description of the Related Art FIG. 7 and FIG. 8 show a conventional antenna device.
Will be described with reference to. FIG. 7 is a diagram for explaining a conventional antenna device. FIG. 8 is a diagram for explaining a conventional antenna device arranged in parallel. The antenna device of the conventional example shown in FIG. 7 is a dipole array antenna DA1 with a reflector, and its directivity is expressed as a main lobe M and side lobes S1 and S2 as shown in FIG.

Ideally, the directivity of the dipole array antenna DA1 should ideally consist of only the main lobe M, and the side lobes S1 and S2 are required to be at the lowest possible level. Therefore, in order to reduce the side lobe, as shown in FIG. 8, another dipole array antenna DA2 having the same shape and characteristics as the dipole array antenna DA1 is arranged in parallel with the dipole array antenna DA1 and the dipole array antenna DA1.
A method is adopted in which the distance between 1 and the dipole array antenna DA2 is set at a distance of about ½ wavelength at the used frequency, and power is fed in two phases from the power feeding device in the same phase.
According to this method, the phase of the side lobes is inverted by 180 ° by separating the distance by half wavelength (half wavelength), and it is possible to reduce the side lobes by the effect of canceling each other.

[0004]

However, the antenna device shown in FIG. 8 has a drawback that the directivity is 2 beams, and the antenna device is required to have 1 beam directivity and a small side lobe. Is unsuitable.

For example, when used for a base station antenna of a mobile communication system, it is general to install a plurality of antenna devices covering a plurality of sectors adjacent to each other on one steel tower. At this time, each sector is assigned a different frequency in order to avoid interference between sectors, but if the sidelobe level is sufficiently low, it is possible to assign the same or close frequencies to adjacent sectors. Becomes This is also useful from the viewpoint of effective use of radio waves.

At this time, even if the level of the side lobe can be reduced as shown in FIG. 8, the width of the beam is expanded when the number of beams is two, so that interference between sectors due to the main lobe is avoided. In addition, since a measure such as widening the sector interval is required, a new problem occurs.

The present invention has been made against such a background, and an object thereof is to provide an antenna device having one beam and a small side lobe. An object of the present invention is to provide an antenna device that can avoid interference between adjacent wireless devices. An object of the present invention is to provide an antenna device that can effectively use radio waves.

[0008]

The antenna device of the present invention realizes an antenna device having a single beam in a horizontal plane and a small side lobe by controlling the intervals and feeding phases of a plurality of dipole antenna elements. The main feature is to do.

That is, the present invention is an antenna device, which is characterized in that one planar reflector (R) is used.
And two straight lines, which are respectively set on one side of the reflecting plate and are perpendicular to the reflecting plate and are separated from each other by a distance L1, are parallel to each other with a distance d so as to be orthogonal at the corresponding corresponding positions. In addition, n dipole antenna elements parallel to the reflector are provided (DA1,1 to DA1, n, DA
2,1 to DA2, n) are arranged, and the distance between the one of the dipole antenna elements closest to the reflector and the reflector is L2. Signals of equal amplitude with different phases are fed by the same amount of phase φ.

It is desirable that the distance L1 is approximately one half wavelength. Further, it is desirable that the distance L2 is approximately a quarter wavelength.

As described above, since the dipole array antennas are arranged at a distance of one-half wavelength, the side lobes of the two antennas cancel each other and become small. Further, according to the configuration of the present invention, directivity of one beam can be obtained.

Both ends of the reflection plate may be bent on the side where the two dipole array antennas are arranged so that the dipole antenna element and its bending surface are parallel to each other. By doing so, it is possible to reduce the wraparound of the radiated wave to the back surface of the reflector.

[0013]

DETAILED DESCRIPTION OF THE INVENTION

[0014]

【Example】

(First Embodiment) The configuration of the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of an antenna device according to a first embodiment of the present invention. FIG. 2 is a configuration diagram of the antenna device according to the first embodiment of the present invention.

The present invention is an antenna device, which is characterized in that a planar reflector R and a reflector R set on one side of the reflector R are perpendicular to each other and are spaced apart from each other. Dipole antenna elements DA1, which are parallel to each other and are parallel to the reflector R, are spaced apart by a distance d so as to be orthogonal to the two corresponding straight lines separated by L1.
1 to DA1,4 and DA2,1 to DA2,4 are arranged in groups of four, and the dipole antenna elements DA1,1 to DA1,4,
The distance between the reflector R out of DA2,1 to DA2,4 and the reflector R is L2, and this dipole antenna element DA1,1 to DA1,4, DA2,1 to DA2,4
Is fed with equal amplitude signals having different phases by the same phase amount φ according to the straight line.

The distance L1 is arranged at a distance of approximately one-half wavelength. Further, the distance L2 is set to approximately a quarter wavelength.

As shown in FIG. 1, the dipole antenna elements DA1,1, DA2,1, DA1,2, DA are arranged from the side closer to the reflector R.
Let 2,2, DA1,3, DA2,3, DA1,4, DA2,4. The dipole antenna element DA2,1 has the same amplitude and the same phase as the dipole antenna element DA1,1 and the dipole antenna elements DA1,2 and DA2, DA2,1.
2 is a phase difference φ delayed from the dipole antenna elements DA1,1 and DA2,1, and the dipole antenna elements DA1,3
And DA2,3 are dipole antenna elements DA1,1
And DA2,1 are delayed by a phase difference of 2φ, and dipole antenna elements DA1,4 and DA2,4 are delayed by a phase difference of 3φ compared to dipole antenna elements DA1,1 and DA1,2. In the first embodiment of the present invention, four dipole antenna elements DA1,1 are provided for the sake of clarity.
.About.DA1,4, DA2,1 to DA2,4 will be described as an example, but the number is not limited. In this case,
The dipole antenna elements DA1, n and DA2, n are controlled so that the power is delayed with a phase difference (n-1) φ compared with the dipole antenna elements DA1,1 and DA1,2. At this time, by optimally selecting the interval d and the phase difference φ,
A dipole array antenna device with a reflector having a low side lobe can be realized. In order to determine the optimum interval d and the phase difference φ, it is possible to determine them by theoretical values obtained by performing calculation using the method of moments.

In the moment method, the antenna is divided into minute sections, the current flowing in the minute sections is calculated from the boundary conditions, and the current distribution of the antenna is known to determine the electromagnetic field created by the antenna and the input / output of the antenna. It is a method to derive impedance etc. (Reference: Kazuhiro Hirasawa, "Points of application of moment method for linear antenna analysis", Technical Report of IEICE 2nd Class, AP89-S
2, pp. 5-11, November 1989, Institute of Electronics, Information and Communication Engineers, Antenna Engineering Handbook, Ohmsha, Showa 55
Year).

By using this moment method and performing a simulation for a state in which the distance d and the phase difference φ are changed, the optimum distance d and the phase difference φ can be determined. In the first embodiment of the present invention, the optimum spacing d and the phase difference φ are set such that the spacing d is 0.2 wavelength of the used frequency and the phase difference φ is 80 °.

A radiation pattern of the antenna device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing a radiation pattern showing directivity in a horizontal plane of the antenna device of the first embodiment of the present invention. The horizontal axis represents the angle in the horizontal plane when the antenna device is viewed from the front, and the vertical axis represents the relative electric field strength. In FIG. 3, the interval d is set to 0.
Two wavelengths and a phase difference φ of 80 ° were set. According to the present invention, an antenna device having a sidelobe level of approximately −20 dB or less can be realized in this way.

Here, FIG. 4 shows an example in which another interval d and phase difference φ in the simulation process are adopted. FIG. 4 is a diagram showing a radiation pattern indicating directivity in the horizontal plane of the antenna device in the simulation process. In FIG. 4, the interval d is 0.2 wavelength of the used frequency, but the phase difference φ is 150 °. Thus the phase difference φ
Therefore, the low sidelobe antenna device, which is the object of the present invention, could not be realized.

In the antenna device of the first embodiment of the present invention, the result of measuring the side lobe level at that time by changing the interval d and the phase difference φ is shown in FIG. The horizontal axis represents the element spacing d / λ, and the vertical axis represents the phase difference φ. An antenna device with a low side lobe can be realized by controlling the element spacing d and the phase difference φ so that the portion S surrounded by a diagonal line is formed.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram of the antenna device according to the second embodiment of the present invention. In the second embodiment of the present invention, dipole antenna elements DA1,1 to DA1, are provided on both sides of the reflector R on which the dipole array antennas DA1 and DA2 are arranged.
4, DA2,1 to DA2,4 are bent so that their bent surfaces are parallel to each other.

By doing so, it is possible to reduce the wraparound of the radiated wave toward the rear surface of the reflection plate R, so that the directivity of the antenna device can be further improved.

[0025]

As described above, according to the present invention,
A one-beam antenna device having a small sidelobe level can be realized. As a result, it is possible to avoid interference between adjacent wireless devices and to effectively use radio waves.

[Brief description of drawings]

FIG. 1 is a perspective view of an antenna device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of the antenna device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a radiation pattern showing directivity in a horizontal plane of the antenna device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a radiation pattern showing directivity in a horizontal plane of the antenna device in a simulation process.

FIG. 5 is a diagram showing a result of measuring a side lobe level at that time by changing the element spacing d and the phase difference φ.

FIG. 6 is a configuration diagram of an antenna device according to a second embodiment of the present invention.

FIG. 7 is a diagram for explaining a conventional dipole array antenna with a reflector.

FIG. 8 is a diagram for explaining a conventional dipole array antenna with a reflector arranged in parallel.

[Explanation of symbols]

DA1, DA2 Dipole array antenna DA1,1 to DA1,4, DA2,1 to DA2,4 Dipole antenna element M Main lobe R Reflectors S1 and S2 Side lobes

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Claims (3)

(57) [Claims] 1. A planar reflector (R) and two reflectors (R), which are set on one side of the reflector and are perpendicular to each other and are separated from each other by a distance L1 of about a half wavelength. There are n dipole antenna elements (DA1, 1 to DA1, DA1 to DA1, DA1 to DA1, which are parallel to each other and are parallel to each other at a distance d so as to be orthogonal to each other at the same position.
n, DA2,1 to DA2, n) are arranged, and the distance between the dipole antenna element closest to the reflector and the reflector is L2. An antenna device, wherein signals of equal amplitude having different phases are fed by an equal amount of phase φ. 2. The distance L2 is approximately a quarter wavelength.
The antenna device of a claim 1, wherein. 3. The two dipoles are provided at both ends of the reflector.
On the side where the lure array antenna is arranged, the dipole antenna
Bend it so that the bending element and the bending surface are parallel.
The antenna device according to claim 1 or 2, wherein was.