JP3363009B2 - 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 two-beam directivity. The present invention relates to a directivity improving technique.

[0002]

2. Description of the Related Art A conventional antenna device will be described with reference to FIG. FIG. 8 is a configuration diagram of a conventional two-beam array antenna device. Dipole antenna elements M _{1 to} M ₄ ,
N _{1 to} N _{4 form} dipole array antennas M and N, respectively. As shown in FIG. 8, a hybrid circuit HYB is used for a reflector R and two dipole array antennas M and N having the same characteristics, and a terminal a is used.
And b respectively, the input from terminal a producing beam A and the input from terminal b producing beam B.

The dipole array antennas M and N
Are arranged in parallel at approximately half-wavelength intervals,
The dipole antenna elements M ₁ , M ₂ , M ₃ , M ₄ and N ₁ , N ₂ , N ₃ , N ₄ are fed with a phase difference φ between them.

[0004]

Side lobes SA1, SA2, SB1 and SB2 peculiar to the array antenna are generated in the beam of the antenna device of this conventional example. The generation of the side lobes SA1, SA2, SB1 and SB2 imposes various restrictions on the effective use of radio waves. For example, when used as 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, it is necessary for each sector to allocate and operate different frequencies in order to avoid inter-sector interference due to the influence of side lobes.

The reduction of side lobes makes it possible to assign the same or close frequencies to adjacent antenna devices, which is useful for effective use of radio waves.

The present invention has been made against such a background, and an object thereof is to provide an antenna device having 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. An object of the present invention is to provide an antenna device having a wide sideband frequency characteristic with a small side lobe.

[0007]

The antenna device of the present invention realizes an antenna device having a small side lobe by narrowing the distance between two dipole array antennas arranged facing each other as the distance from the reflector plate increases. Is the main feature.

That is, the present invention is an antenna device, which is characterized in that one planar reflector (R) is used.
And two normals perpendicular to the reflector set on one side of the reflector and separated from each other by a distance L1 from the reflector and separated from each other by a distance L2 from the reflector. There are n dipole antenna elements, each parallel to the straight line rotated inward by an angle α on a plane including the vertical line, at intervals d so that they are orthogonal to each other at the same corresponding position and parallel to the reflector ( M _{1 to} M _n , N _{1 to} N _n ) are arranged, and the distance between the reflector and the closest one of the dipole antenna elements to the reflector is L 2, and the dipole antenna element includes According to the straight line, signals of equal amplitude having different phase amounts φ are fed.

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

The side lobes can be canceled by installing the two dipole array antennas so as to be separated from each other by approximately one-half wavelength. At this time, the feature of the present invention lies in that the side lobes can be further reduced by arranging the dipole array antennas so as to be inclined inward with respect to each other by the inclination angle α. The inventor obtained this result by simulation.

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. With this, it is possible to reduce the wraparound of the radiated wave to the back surface of the reflector, and thus it is possible to further improve the directivity of the antenna device.

The lengths of the dipole antenna elements forming the two dipole array antennas are configured to be gradually reduced at a constant ratio as the distance from the dipole antenna element closest to the reflector is increased. You may As a result, it is possible to realize an antenna device having wideband frequency characteristics while reducing side lobes.

[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 by one planar reflector R and this reflector R.
The two perpendiculars that are perpendicular to the reflector R set on one side and are separated by a distance L2 from the reflector R that are perpendicular to each other and include the two perpendiculars. The straight lines rotated inward by an angle α on the plane are parallel to each other at intervals d so that they are orthogonal to each other at the corresponding corresponding positions, and the reflector R
Dipole antenna elements M _{1 to} M ₄ , N _{1 to} N parallel to
_Four dipoles are arrayed four by four, and this dipole antenna element M
The distance between the reflector R out of _{1 to} M ₄ and N _{1 to} N ₄ which is the closest to the reflector R is L2, and the dipole antenna elements M _{1 to} M ₄ and N _{1 to} N _{4 are provided.} Is fed with equal amplitude signals having different phases by the same phase amount φ according to the straight line.

The distance L1 is approximately a half wavelength. The distance L2 is approximately a quarter wavelength.

Here, in order to make the explanation easy to understand, four dipole antenna elements M _{1 to} M ₄ and N _{1 to} N _{4 are used.}
However, the number is not limited.

Each dipole antenna M _{1 to} M ₄ , N ₁ to
N ₄ has the same amplitude, and dipole antennas M ₂ and N ₂
Are delayed by 1φ from the dipole antennas M ₁ and N ₁ , the dipole antennas M ₃ and N ₃ are delayed from the dipole antennas M ₁ and N ₁ by 2φ, and the dipole antennas M ₄ and N ₄ are dipole antennas. M ₁ , N ₁
The phase is delayed by 3φ.

Further, the dipole antennas M _{1 to} M ₄ and the dipole antennas N _{1 to} N ₄ are fed by the hybrid circuit HYB with a phase difference of 90 °.

As shown in FIG. 7 as a conventional example, a straight line in which the dipole antennas M _{1 to} M ₄ are lined up with respect to a vertical line of the reflector R and a line in which the dipole antennas N _{1 to} N ₄ are lined up do not form an inclination angle α. Side lobes can be reduced as compared with the case. At this time, the interval d, the phase difference φ, and the tilt angle α can be optimized by determining each parameter using the calculated values by the method of moments.

In the moment method, the antenna is divided into minute sections, the current flowing in the minute sections is obtained 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, the tilt angle α, and the phase difference φ are changed, the optimum distance d, the tilt angle α, and the phase difference φ can be determined. . In the first embodiment of the present invention, the optimum distance d, the tilt angle α and the phase difference φ are set.
As a result, the interval d was set to 0.2 wavelength of the used frequency, the tilt angle α was set to 4 ° to 6 °, and the phase difference φ was set to 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.
The phase difference φ was set to 90 ° for 24 wavelengths. According to the present invention, the sidelobe level is thus approximately -20 dB.
An antenna device that can be reduced to the following can be realized.

FIG. 4 shows the relationship between the tilt angle α and the side lobe.
Shown in. In FIG. 4, the interval d = 0.24 wavelength and the phase difference φ = 9.
It is a figure which shows the relationship between the inclination angle (alpha) and side lobe when it is set to 0 degree. The horizontal axis represents the tilt angle α (°), and the vertical axis represents the side lobe level (dB). According to this, it can be seen that the side lobe level has the lowest value in the vicinity of the tilt angle α of 4 ° to 6 °.

Here, FIG. 5 shows an example of the case in which another interval d, tilt angle α, and phase difference φ are adopted in the simulation process. FIG. 5 is a diagram showing a radiation pattern showing directivity in the horizontal plane of the antenna device in the simulation process. In FIG. 5, the interval d is 0.
Two wavelengths are used, but the tilt angle α is 0 ° and the phase difference φ is 90 °
And In this way, the tilt angle α is not set (α = 0
If the phase difference φ is set to 90 °, the low sidelobe antenna device, which is the object of the present invention, could not be realized.

(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, the reflector R
Dipole both ends of the vertical to the side of arranging the dipole array antenna M and N antenna elements M ₁ ~M _4, N ₁
It is characterized in that it is bent so that N ₄ and its bent surface are parallel to each other. By doing so, it is possible to reduce the wraparound of the radiated wave toward the back surface of the reflector R, and thus it is possible to further improve the directivity of the antenna device.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a block diagram of the antenna device according to the third embodiment of the present invention. In the present invention the third embodiment, the dipole antenna elements M ₁ ~M _4, N ₁ respective lengths of to N _4, the reflection plate nearest dipole antenna elements R M ₁
And N ₁ away from the reflection plate R, the distance is gradually reduced at a constant rate. By doing so, it is possible to realize an antenna device having wideband frequency characteristics while reducing side lobes.

[0028]

As described above, an antenna device having a small side lobe can be realized. As a result, it is possible to avoid interference between adjacent wireless devices and to effectively use radio waves. Further, it is possible to realize an antenna device having a small side lobe and a wide band frequency characteristic.

[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 relationship between a tilt angle α and side lobes.

FIG. 5 is a diagram showing a radiation pattern showing directivity in a horizontal plane of the antenna device in a simulation process.

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

FIG. 7 is a configuration diagram of an antenna device according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional two-beam array antenna device.

[Explanation of symbols]

HYB hybrid circuits M _{1 to} M ₄ , N _{1 to} N ₄ dipole antenna M, N dipole array antenna R reflectors SA1, SA2, SB1, SB2 side lobes

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 3/00-3/46 H01Q 21/00-25/04 H01Q 9/16 H01Q 19/10

Claims (4)

(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. Two perpendicular lines are rotated inwardly by a distance L2 from the reflection plate, respectively, and are linearly rotated inward by an angle α on a plane including the two perpendicular lines. There are arranged n dipole antenna elements (M _{1 to} M _n , N _{1 to} N _n ) parallel to each other and spaced apart from each other by d (M _{1 to} M _n , N _{1 to} N _n ). The distance between the reflector and the reflector is L2, and the dipole antenna element is fed with equal amplitude signals having different phase amounts φ according to the straight line. Antenna device that. 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. 4. The two dipole array antennas
The length of the constituent dipole antenna elements is the same as that of the reflector plate.
From the dipole antenna element closest to
It gradually decreases at a constant rate as the distance increases
The antenna device according to claim 1 , configured as described above.