JP4300724B2 - Polarization diversity omnidirectional antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a horizontal omnidirectional antenna that radiates orthogonal oblique polarization having a polarization diversity function, and in particular, a polarization diversity omnidirectional antenna that is excellent in vibration resistance and easy to adjust omnidirectional. It is about.
[0002]
[Prior art]
Radiation characteristics required for mobile communication base station antennas such as PHS and mobile phones vary depending on conditions such as installation location and cover area, but they must be omnidirectional in a horizontal plane. Especially many.
[0003]
Most of the omnidirectional antennas in the horizontal plane are sleeve antennas, and their gain is a single type (single-stage configuration) and is about 2.14 dBi. There is also a configuration in which the number of stages is increased to several or more than ten according to the user's request, and the gain becomes high according to the number of stages.
[0004]
However, in reality, a horizontal omnidirectional antenna that radiates orthogonal oblique polarized waves having a polarization diversity function may be required. FIG. 9 shows a conventional polarization diversity omnidirectional antenna. A conventional polarization diversity omnidirectional antenna is provided with a patch 5a on one side of a dielectric substrate, microstrip lines 4a and 4b connected to the patch 5a, and a slot 3 that is obliquely orthogonal to the back surface of the patch 5a, A patch 5b is provided on the opposite side of the dielectric substrate, and a chassis 2 for fixing the dielectric substrate is attached to the dielectric substrate. With this structure, orthogonally polarized waves are excited in the patch 5a with the power supplied from the microstrip lines 4a and 4b, and a directional beam having a wide beam half-value width is emitted from the patch 5a. On the other hand, a part of the electric power supplied to the patch 5a is taken out by the slot 3, and a directional beam having a wide beam half-value width is similarly emitted from the patch 5b on the opposite side. The radio waves radiated from the patch 5a and the patch 5b are combined in space to become an omnidirectional beam. In the case of high gain, the antenna having this configuration is multistaged. Further, when this antenna is operated, due to environmental problems such as waterproofing, the antenna is accommodated in a radome (cover) 10 as shown in FIG. 8, and a pedestal 11 is attached to fix the antenna to the tower of the base station.
[0005]
[Problems to be solved by the invention]
By the way, when the omnidirectional antenna in the horizontal plane is attached to the tower of the base station, it is necessary to fix it only on the lower side of the antenna so as not to interfere with radio wave radiation. An antenna fixed only on the lower side has a lower natural frequency as a structure compared to a directional antenna that can be fixed to a steel tower at multiple locations on the back side of the antenna. This causes the antenna to resonate. In addition, in the conventional polarization diversity omnidirectional antenna, the chassis 2 to which the dielectric substrate is attached has a flat and upright structure, and therefore has a problem that it is very weak against a load perpendicular to the surface of the dielectric substrate. .
[0006]
Further, when the material of the radome 10 is changed, the beam half-value width on one side is changed, so that there is a possibility that the non-directional property is lost. In the conventional polarization diversity omnidirectional antenna, it is necessary to change the dimensions of the dielectric substrate and the patches 5a and 5b in order to recover the omnidirectionality. For this reason, there exists a problem that redesign takes very time.
[0007]
Further, in the conventional polarization diversity omnidirectional antenna, the directivity on one side is not completely symmetrical about the main beam. For this reason, the intensity difference due to the angle becomes large in the directivity synthesized on both side surfaces.
[0008]
Accordingly, an object of the present invention is to provide a polarization diversity omnidirectional antenna that solves the above-described problems, has excellent vibration resistance, and allows easy adjustment of omnidirectionality.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the polarization diversity omnidirectional antenna according to the present invention includes a dielectric substrate having a polarization diversity function and a directivity antenna, and the antenna on three sides is erected in three directions. Is a polarization diversity omnidirectional antenna in which the combined directivity becomes horizontal omnidirectional by being fed to each antenna from a 1-input 3-output distributor. Te, said dielectric substrate in a linear slot perpendicular shape of the slot is provided diagonally opposite the slot, in a position to receive the radio wave radiated from the slot, so as to be parallel to the dielectric substrate in the slot patch is provided which emits a directional beam to be excited, the direction where the virtual extension plane of the patch intersects the imaginary extension plane of the other of said patches Parasitic elements are provided at positions on both sides of the patch at a predetermined distance from the patch so that one side is in contact with the dielectric substrate and is perpendicular to the dielectric substrate, and the center of the antenna of the three surfaces A polarization diversity omnidirectional antenna in which the distance from the antenna to each antenna is 0.3λ ₀ (λ ₀ : propagation wavelength in vacuum) or less, and the beam half-value width in the horizontal plane of each antenna is 70 ° to 80 °. is there.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
[0014]
As shown in FIG. 1, the polarization diversity omnidirectional antenna according to the present invention is configured such that three antennas 1a, 1b, and 1c made of a dielectric substrate are erected and faced in three directions. As the sides of each surface come into contact with each other, a triangular prism shape is formed as a whole. The chassis 2 is similarly formed in a triangular prism shape with three plate-like members, and antennas 1a, 1b, and 1c are attached to the respective surfaces.
[0015]
The antennas 1a, 1b, and 1c are formed on a dielectric substrate by forming a slot 3 having a straight slot obliquely orthogonal thereto and a microstrip line 4a and 4b extending along the slot 3, and a patch (radiating) on the slot 3. (Also referred to as a patch) 5a is provided, and parasitic elements 6a and 6b are provided on both sides of the patch 5a so as to be perpendicular to the dielectric substrate. The parasitic elements 6a and 6b are formed in a rectangular plate shape, and are installed at a predetermined distance from the patch 5a so that one side is in contact with the dielectric substrate and the surfaces of the parasitic elements 6a and 6b are perpendicular to the dielectric substrate. The The length of the side perpendicular to the dielectric substrate is called the height h of the parasitic elements 6a and 6b.
[0016]
FIG. 2 shows the front of the antenna 1a. FIG. 3 shows the top surface of the polarization diversity omnidirectional antenna of FIG. As shown in the figure, the patch 5a is provided in parallel to the dielectric substrate at a predetermined distance from the dielectric substrate of the antenna 1a, and the parasitic elements 6a and 6b are parallel to the left and right sides of the patch 5a. It is provided vertically.
[0017]
The polarization diversity omnidirectional antenna is configured to feed power to the respective antennas 1a, 1b, and 1c from the three distributors 7a and 7b.
[0018]
Here, + 45 ° polarization is supplied by the microstrip line 4a, and −45 ° polarization is supplied by the microstrip line 4b. One of the portions where the microstrip lines 4a and 4b intersect with each other is formed, for example, by letting the microstrip line 4b pass through the back side of the dielectric substrate through the through hole 9. The three distributors 7a and 7b are circuits that divide the input power into three in-phase and equal distribution ratios. The three distributors 7a and 7b have one input terminal and three output terminals. Each input terminal is connected to a + 45 ° polarization source and a −45 ° polarization source (not shown), and each output terminal is connected to the connection cable 8a to 8c. 8f is connected to the microstrip lines 4a and 4b of the antennas 1a, 1b and 1c.
[0019]
In the above configuration, when power is supplied to the microstrip lines 4a and 4b, the slot 3 is excited and a directional beam is emitted from the patch 5a. The antennas 1a, 1b, and 1c are arranged in an equilateral triangle when viewed from above, and the distance from the center of the equilateral triangle (this is called the center of the antenna) to each of the antennas 1a, 1b, and 1c is propagated in the vacuum at the used frequency When the wavelength is λ ₀ , the wavelength is 0.3λ ₀ or less. Further, the beam half-value width in the horizontal plane of each antenna 1a, 1b, 1c is set to 70 ° to 80 °. As a result, the combined directivity of each beam becomes horizontal omnidirectional.
[0020]
If the distance from the center of the antenna to each of the antennas 1a, 1b, and 1c is greater than 0.3λ ₀ , the radiation intensity at the valley of the combined directivity becomes small and becomes non-directional. Further, when the beam half width becomes narrower than 70 °, the radiation intensity decreases in the direction of the side of each antenna 1a, 1b, 1c. Conversely, when the beam half width becomes wider than 80 °, each antenna 1a, 1b, 1c. Since the radiation intensity increases in the direction of the side of, the omnidirectionality is lost in either case.
[0021]
As described above, the polarization diversity omnidirectional antenna according to the present invention can realize horizontal omnidirectionality.
[0022]
Further, focusing on the strength as a structure, the polarization diversity omnidirectional antenna according to the present invention is arranged so that the antennas 1a, 1b, and 1c are directed in three directions. It can be formed in a triangular prism shape with a shaped member. This triangular structure increases the robustness against vibration.
[0023]
Next, when the radome material or the like is changed depending on the installation environment of the antenna, the horizontal beam half-value widths of the individual antennas 1a, 1b, and 1c may change, and the combined directivity may not be omnidirectional. Therefore, in the present invention, the horizontal beam half width of each antenna 1a, 1b, 1c is controlled by the height h of the parasitic elements 6a, 6b. In this way, the synthesized directivity can be made omnidirectional by changing the horizontal beam half-value widths of the individual antennas 1a, 1b, and 1c depending on the height h of the parasitic elements 6a and 6b. Easy.
[0024]
In the case of high gain, the antenna having the configuration of the present invention may be multistaged.
[0025]
By the way, in general, the directivity of an obliquely polarized antenna is not completely symmetric with respect to the main beam as an axis, and there is an intensity difference between right and left in a portion where the radiation intensity is small. In the example of the directivity of + 45 ° polarization shown in FIG. 4, the intensity at −90 ° (left) is larger than the intensity at + 90 ° (right). Although not shown, in the opposite polarization (in this case, −45 ° polarization), the difference in intensity between the left and right is reversed, and the intensity on the left is reduced. As a result, the combined directivity of the three antennas 1a, 1b, and 1c has a difference in strength between the left and right sides of the front of the antenna as shown in FIG.
[0026]
Therefore, in the present invention, the directivity symmetry of the antenna is adjusted by changing the shape of the parasitic element. Specifically, the height h is increased in a part of the parasitic elements 6a and 6b on the side where the radiation intensity is low. When the intensity on the right side is small in the + 45 ° polarization as shown in FIG. 4, the right parasitic element 6a is formed in a key shape whose upper side is longer than the lower side, as in the embodiment shown in FIG. In this way, the height h of the upper portion of the right parasitic element 6a is increased. Then, the beam on the right side of the parasitic element 6a spreads, resulting in a symmetric beam. As a result, the intensity difference as shown in FIG. 5 is eliminated, and excellent omnidirectionality is realized with a small intensity difference as shown in FIG.
[0027]
Even at −45 ° polarization, the strength at the left side of the antenna is small, so it is necessary to increase the height h in a part of the parasitic element 6b. At this time, the upper part of the parasitic element 6b having a height h is separated from the portion of the slot 3 that radiates the + 45 ° polarized wave, thereby eliminating the influence on the directivity of the + 45 ° polarized wave.
[0028]
As described above, in the polarization diversity omnidirectional antenna of FIG. 6, the beam on the right side of + 45 ° polarization is spread by the parasitic element 6a, and the beam on the left side of −45 ° polarization is spread by the parasitic element 6b.
[0029]
【The invention's effect】
The present invention exhibits the following excellent effects.
[0030]
(1) Since each antenna is arranged in three directions, the chassis can be formed in a triangular prism shape to improve anti-vibration properties.
[0031]
(2) Even when the material of the radome is changed, the half width of the beam can be controlled by the height of the parasitic element, so that the design can be easily changed.
[0032]
(3) Due to the shape of the parasitic element, it is possible to improve the directivity asymmetry of the individual antennas and reduce the intensity difference of the combined directivity.
[Brief description of the drawings]
FIG. 1 is a perspective view of a polarization diversity omnidirectional antenna showing an embodiment of the present invention.
2 is a front view of the polarization diversity omnidirectional antenna of FIG. 1; FIG.
3 is a top view of the polarization diversity omnidirectional antenna of FIG. 1. FIG.
FIG. 4 is a directivity diagram of an antenna when there is a difference in intensity between the right and left main beams.
FIG. 5 is a directivity diagram showing a combined directivity when three antennas having intensity differences on the left and right of the main beam are used.
FIG. 6 is a perspective view of a polarization diversity omnidirectional antenna showing another embodiment of the present invention.
7 is a directivity diagram showing a combined directivity when the left-right intensity difference of the main beam is compensated by the configuration of FIG. 4; FIG.
FIG. 8 is an installation structure diagram of a base station antenna.
FIG. 9 is a perspective view of a conventional polarization diversity omnidirectional antenna.
[Explanation of symbols]
1a, 1b, 1c Antenna 2 Chassis 3 Slots 4a, 4b Microstrip line 5a Patches 6a, 6b Parasitic elements 7a, 7b 3 distributors

Claims (1)

An antenna having a polarization diversity function and a directivity is formed on a dielectric substrate, and the three-surface antennas are erected and arranged in three directions. Each distributor is provided with a 1-input 3-output distributor. A polarization diversity omnidirectional antenna in which the synthesized directivity becomes horizontal omnidirectional by being fed,
The dielectric substrate is provided with a slot having a shape in which a straight slot is obliquely orthogonal,
The opposite to the slot, in a position to receive the radio wave radiated from the slot, so as to be parallel to the dielectric substrate, said slot patch is provided which emits a directional beam to be excited,
One side of the patch is in contact with the dielectric substrate at a predetermined distance from the patch on both sides of the patch in a direction in which the virtual extension surface of the patch intersects the virtual extension surface of another patch. Parasitic elements are provided to be vertical,
The distance from the center of the antennas of the three surfaces to each antenna is set to 0.3λ ₀ (λ ₀ : propagation wavelength in vacuum) or less, and the beam half-value width in the horizontal plane of each antenna is set to 70 ° to 80 °. Polarization diversity omnidirectional antenna.

Images