JP3551227B2 - Horizontally polarized omnidirectional antenna - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a horizontally polarized omnidirectional antenna that can be used for a PHS or a mobile phone base station, and more particularly to a horizontally polarized omnidirectional antenna that can obtain good directional characteristics in a horizontal plane.
[0002]
[Prior art]
Radiation characteristics required for an antenna for mobile communication vary depending on conditions such as an installation location and a cover area, but in particular, many antennas are required to be non-directional in a horizontal plane. Of these horizontal omnidirectional antennas, a sleeve antenna and the like are often used, and the gain thereof is a single type (one stage) and is about 2.14 dBi. In addition, there is a configuration in which the number of stages is increased to several stages or tens of stages in accordance with a user's request, and the gain becomes high according to the number of stages.
[0003]
As the high-gain horizontal omnidirectional antenna, specifically, an antenna in which a plurality of antenna elements are arranged vertically and parallel power is supplied from a power supply circuit on a substrate has been proposed (Japanese Patent Laid-Open No. 8-340221). reference). This high-gain horizontal omnidirectional antenna has a plurality of vertically polarized dipole antenna elements arranged in a line in the vertical direction, and a feed line having an electrical length approximately equal to the electrical length between the feed point and each dipole antenna element. (Strip line).
[0004]
Specifically, as shown in FIGS. 16A and 16B, an antenna element 22 is arranged on a vertically long ground plane 21 (the ground plane 21 and the antenna element 22 are insulated). Power is supplied to each antenna element 22 through 23. Similarly, an antenna element 22 is arranged on the back side base plate 21, and power is supplied from the power supply circuit through a power supply pin 23.
[0005]
However, in practice, a horizontal omnidirectional antenna that emits horizontally polarized waves instead of vertically polarized waves may be required.
In this case, for example, as shown in FIG. 17A, a horizontally polarized dipole antenna can be considered by rearranging the antenna elements horizontally.
[0006]
[Problems to be solved by the invention]
However, since the length L3 of the antenna elements 22a and 22b (see FIG. 17A) is required to be about 0.5 wavelength in principle, the width L2 of the entire antenna is longer than 0.5 wavelength. The width L2 is considerably longer than the width L1 (see FIG. 16 (a)) for emitting vertically polarized waves which is about 0.2 wavelength. That is, if a structure for emitting horizontally polarized waves is used, the outer diameter of the antenna becomes large, and accordingly, it becomes difficult to obtain horizontal omnidirectional characteristics.
[0007]
In addition, when the antenna elements are arranged side by side, as shown in FIG. 17B, the feeding point for the front antenna element 22a and the feeding point for the rear antenna element 22b are adjusted as shown in FIG. The position must be reversed. That is, two power supply pins are required for each stage (23a and 23b).
For this reason, as shown in FIG. 17C, it is necessary to branch the strip line 25 for supplying power to the power supply pins 23a and 23b, which further complicates the structure of the power supply circuit.
[0008]
Accordingly, an object of the present invention is to provide a horizontally polarized omnidirectional antenna having good horizontal omnidirectionality and requiring a small outer diameter of the antenna itself.
Another object of the present invention is to provide a horizontally polarized omnidirectional antenna having a simple feeder circuit structure.
[0009]
Means for Solving the Problems and Effects of the Invention
The horizontally polarized omnidirectional antenna of the present invention has rectangular conductor ground planes opposing each other on both sides of the center line, and a single feed circuit board is disposed between both ground planes. An antenna in which a pair of antenna elements are arranged in one stage or in multiple stages in the center line direction, each of the antenna elements constituting the pair of antenna elements is bent and arranged so as to straddle the side end surfaces of both base plates, A power supply pin is provided on the power supply circuit board to feed power to the pair of antenna elements through both conductor ground planes, and power is supplied to both antenna elements constituting the pair of antenna elements from both ends of the power supply pin. (Claim 1).
[0010]
A typical structure of the horizontally polarized omnidirectional antenna will be described with reference to FIG.
FIG. 1 is a cross-sectional view of a horizontally polarized omnidirectional antenna viewed from the center line direction. A rectangular conductor ground plane is indicated by reference numeral 21. 24 is a power supply circuit board. Each of the antenna elements 22 c and 22 d constituting a pair of antenna elements is arranged so as to bend over the side end surfaces 25 of both base plates 21. A power supply pin 23 is provided upright on the power supply circuit board 24, and both ends of the power supply pin are connected to the antenna elements 22c and 22d.
[0011]
With such a horizontally polarized omnidirectional antenna structure, since each of the antenna elements 22c and 22d is bent so as to straddle the side end surfaces 25 of both base plates 21, the length L4 of the bent portion is , Antenna length can be earned. Therefore, the antenna can be made more compact as compared with the case where the antenna length is increased only by L3 as in the prior art of FIG. In other words, although the thickness is slightly increased, the width L2 of the antenna does not need to be increased, so that the cross-sectional dimension of the antenna can be reduced as a whole. Further, since the cross-sectional dimension of the antenna is reduced, the wave source becomes smaller, and omnidirectionality can be easily obtained.
[0012]
It is preferable that a bending process is performed on side end surfaces of the conductor ground plates (claim 2). Referring to FIG. 1, both ends of a conductive ground plane 21 are bent as shown by 21a. Due to this bending, the holding of the antenna elements 22c and 22d is ensured, and the mechanical strength is increased.
Although the conductor ground plane 21 and the antenna elements 22c and 22d are illustrated as having a space in FIG. 1, it is actually necessary to eliminate this space and to make a perfect electrical connection. Normal. However, if it is inevitable to insulate the device and the ground plate with an adhesive sheet as a method of fixing the device to the ground plate, the insulator may be filled. This is because if the insulator is thin, it can be regarded as conducting at high frequencies. If the insulator is thick and the capacitance between the element and the ground plane is not large enough to be considered as conducting at high frequencies, the effect of asymmetrical parts such as projecting parts may occur Therefore, it is necessary to design other parts of the element to be asymmetric so as to cancel out the influence.
[0013]
It is preferable that a metal plate for short-circuiting the two conductor ground plates is attached to the side end surfaces of the two conductor ground plates. Referring to FIG. 1, a metal plate 26 is attached to the side end surface 25. Without this metal plate, a slot antenna would be formed between the two conductor ground plates, generating unnecessary radiation and disturbing the characteristics of the antenna.
[0014]
It is preferable that the antenna elements forming the pair of antenna elements are arranged substantially point-symmetrically when viewed from a center line direction, and the power supply pins are erected on a center line of the power supply circuit board. ). It is preferable that the cross-sectional shapes and dimensions of the element and the conductive ground plane are symmetrical in the vertical and horizontal directions except for the projecting portion of the element. This structure will be described with reference to FIG. 1. The feeding pin 23 is provided upright in the center of the substrate 24, and the antenna elements 22c and 22d are arranged in the same shape and point-symmetrically. With such a structure, the electric field distribution is point-symmetrical as indicated by the symbol E in FIG. 1, and omnidirectionality is easily obtained.
[0015]
As shown in FIG. 2, the antenna element constituting the pair of antenna elements is formed by bending a convex conductive plate into a U-shaped cross section. Good (claim 5). However, in the present invention, the antenna element is not limited to the U-shaped cross section, and the protrusion 22ca is not absolutely necessary. As will be described later, various modifications are possible.
[0016]
It is preferable that a shielding plate electrically connected to a conductive ground plane is interposed between the antenna elements constituting the pair of antenna elements (claim 6).
With such a structure, as described later, an electric field is generated between the antenna element and the shielding plate, which becomes a wave source, so that omnidirectionality is easily obtained.
A dielectric may be inserted between the antenna element and the conductor ground plane (claim 7). According to this, the antenna element size can be reduced and the antenna outer diameter can be reduced due to the wavelength shortening effect of the dielectric.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 3 is an exploded perspective view of the horizontally polarized omnidirectional antenna, FIG. 4 is a partial cross-sectional view of the horizontally polarized omnidirectional antenna of FIG. 3, and FIG. 5 is a horizontally polarized omnidirectional antenna of FIG. FIG. 2 is an elevational view of the directional antenna as viewed from the front.
[0018]
In this horizontally polarized omnidirectional antenna, a printed circuit board 3 sandwiched between insulating plates 2a and 2b is sandwiched between both conductive ground plates 1a and 1b with metal conductive ground plates 1a and 1b opposed to each other. Antenna elements 6a to 6d and 6a 'to 6d' are arranged at regular intervals on the outer surfaces of the conductor ground plates 1a and 1b, respectively. Further, the metal plates 1c and 1d are arranged on the side surface.
[0019]
The materials of the conductor ground plates 1a and 1b, the antenna elements 6a to 6d, 6a 'to 6d', and the metal plates 1c and 1d are not particularly limited as long as they are conductors. For example, aluminum or brass can be used.
On the printed circuit board 3, strip lines 4 and 5, which are wirings for feeding power to the antenna elements 6a to 6d and 6a 'to 6d', are formed on one surface. The strip line 4 supplies signals to the antenna elements 6a, 6b, 6a ', 6b' through feed pins 7a, 7b, and the strip line 5 supplies the antenna elements 6c, 6d, 6c ', 6d' to feed pins 7c, 7d. Feed the signal through.
[0020]
FIG. 6 is a sectional view taken along line XX of FIG. Both sides of the conductor ground plates 1a and 1b are both bent to form a U-shaped cross section. In the state of FIG. 6 sandwiching the insulating plates 2a and 2b and the printed board 3, the cross section is H as a whole. It has a shape.
Metal plates 1c and 1d for short-circuiting the conductor ground plates are attached to side end surfaces of the conductor ground plates 1a and 1b.
[0021]
The power supply pins 7a are illustrated as penetrating the conductor ground plates 1a and 1b, the insulating plates 2a and 2b, and the printed circuit board 3, but are actually soldered to predetermined portions of the strip line 4 on the printed circuit board 3. , Are also soldered to the antenna elements 6a and 6a '. However, the antennas 6a and 6a 'may be tightened with nuts by cutting the feed pin 7a with screws. Alternatively, the power supply pin 7a may be divided into two pieces that can be screwed with a male screw and a female screw, and the strip line 4 may be tightened from both pieces. 6 shows a cylinder denoted by reference numeral 9, which is a radome that protects the entire antenna, and is not shown in FIGS.
[0022]
The print patterns of the strip lines 4 and 5 are formed in a tree shape as shown in FIG. More specifically, the tip of the strip line 4 branched at equal impedance is constituted by a tip 4a for soldering the power supply pin 7a and a tip 4b for soldering the power supply pin 7b. The tip branched by impedance is constituted by a tip 5c for soldering the power supply pin 7c and a tip 5d for soldering the power supply pin 7d. Note that it is not always necessary to branch at an equal impedance, and the branch may be asymmetric. The branching method is a matter determined according to how to achieve the directivity in the vertical direction.
[0023]
The bases of the striplines 4 and 5 are independently wired to realize variable beam tilt characteristics, and a connector 10 for connecting a coaxial cable or a phase shifter is attached to each base end.
Since the strip lines 4 and 5 are sandwiched between the conductor ground plates 1a and 1b and surrounded by the metal plates 1c and 1d, unnecessary radiation from the strip lines 4 and 5 can be prevented.
[0024]
The structure of the horizontally polarized omnidirectional antenna has been described above, but the structure of the horizontally polarized omnidirectional antenna of the present invention is not limited to the above. Hereinafter, various modifications will be described with reference to the drawings.
FIG. 8 is a perspective view showing another shape of the antenna elements 6a to 6d and 6a 'to 6d'. According to this example, the fact that the convex conductor plate is bent in a U-shape in cross section is similar to the antenna element shown in FIG. The difference is that a notch 62 for impedance adjustment is provided. This adjustment is for matching the impedance of the strip lines 4 and 5 of the printed circuit board 3 with the impedance of the antenna elements 6a to 6d and 6a 'to 6d'.
[0025]
FIG. 9A is a perspective view showing still another shape of the antenna element. According to this example, the antenna element 64a is formed by bending a convex-shaped conductor plate so that the cross section has a polygonal shape. As a result, the processing of the antenna element becomes slightly complicated, but the outer diameter of the radome can be further reduced.
FIG. 9B is a sectional view of a horizontally polarized omnidirectional antenna using the antenna element of FIG. 9A.
[0026]
FIG. 10 shows an example in which the bending angles θ1 on both sides of the conductor ground plates 11a and 11b are smaller than 90 °. In this case, the bending angle θ2 of the antenna elements 64a and 65a 'can be arbitrarily set. Also in this example, the outer diameter of the antenna can be reduced as in the case of FIG.
FIG. 11A is a cross-sectional view in which shielding plates 1e and 1f electrically connected to a conductive ground plane are interposed between antenna elements 6a and 6a ', and FIG. 11B is an elevation view. Show. Without these shielding plates 1e and 1f, when viewed from the left-right direction AA, the wave source may be behind the antenna element and radiation in the left-right direction may be reduced. Therefore, by providing the shielding plates 1e and 1f, an electric field is generated as shown by the symbol E in FIG. 11A, and this serves as a radiation source of radio waves to increase radiation in the left-right direction AA. it can.
[0027]
FIG. 12 shows an example in which the shielding plates 1e and 1f are mounted in the middle of the antenna element. In this example, since the shielding plates 1e and 1f can be disposed at the center while avoiding the power supply pin 7b, the variation in the directivity between left and right can be further reduced. FIG. 12 illustrates the distribution of the electric field.
FIG. 13 shows an example in which the dielectric 11 is inserted between the antenna elements 6a, 6a 'and the conductor ground plates 1a, 1b. Polytetrafluoroethylene can be given as a material of the dielectric 11. According to this, the antenna element size can be reduced and the antenna outer diameter can be reduced due to the wavelength shortening effect of the dielectric.
[0028]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. In the above embodiment, the number of antenna elements is four. However, the number of antenna elements is not limited to four, and may be one, two, or five or more. The shape of the strip line of the substrate 3 may be appropriately changed. Further, as shown in FIG. 14, the antenna elements 6b and 6b 'and the like which are bent and arranged so as to straddle the side end surfaces of both ground plates and the conventional vertically polarized radiation antenna element 6p (shown in FIG. 16 (a)). (Equivalent to the antenna element 22). Various other changes can be made without changing the gist of the present invention.
[0029]
【Example】
Next, specific design guidelines including materials and dimensions of each part are shown.
First, the conductor ground plates 1a and 1b are formed of aluminum, have a thickness of 4.5 mm, and a height of 700 mm. If this material has this thickness, sufficient strength can be obtained even when it is erected as a base antenna or a mobile antenna. Further, if it is grounded due to its conductivity, it can be used as a lightning conductor.
[0030]
As the insulating plates 2a and 2b, a foam of a synthetic resin such as foamed polypropylene, foamed polyethylene, foamed styrene, foamed urethane, or the like can be used.
The substrate 3 is a flexible substrate (FPC) composed of a base film of polyimide or polyester and copper foil applied thereto.
The antenna elements 6a to 6d and 6a 'to 6d' are made of aluminum, brass or copper plate as usual.
[0031]
The length of the antenna element is L7 (see FIG. 3), the width of the antenna element is L2, the distance between the opposing antenna elements, that is, the thickness of the horizontally polarized omnidirectional antenna is L4, the distance between the opposing conductor ground planes is L5, and the antenna The length of the bent portion of the element is L6 (see FIG. 6).
Actually, a horizontally polarized omnidirectional antenna having four antenna elements was manufactured with L2 = 58 mm, L4 = 26 mm, L5 = 6.2 mm, L6 = 20 mm, and L7 = 20 mm.
[0032]
FIG. 15 shows the measurement results of the directivity of the horizontal polarization in the horizontal plane. The direction of 0 ° on the circumferential axis corresponds to the direction B shown in FIG. The radiation axis is normalized on a linear scale with the electric field strength (V / m) as a peak at 100%.
As a general performance required for the so-called omnidirectional antenna in a horizontal plane, the electric field strength in the minimum direction is 50% or more of the electric field strength in the peak direction. In FIG. 6, the electric field strength in the minimum direction is 80%, and it can be seen that sufficient performance can be secured.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a specific example of a horizontally polarized omnidirectional antenna of the present invention.
FIG. 2 is a perspective view showing a specific example of an antenna element alone.
FIG. 3 is an exploded perspective view of a horizontally polarized omnidirectional antenna.
FIG. 4 is a side elevation view of a horizontally polarized omnidirectional antenna.
FIG. 5 is a front elevation view of a horizontally polarized omnidirectional antenna.
FIG. 6 is a sectional view taken along line XX of the horizontally polarized omnidirectional antenna.
FIG. 7 is an elevation view of a flexible printed circuit board.
FIG. 8 is a perspective view showing another specific example of the antenna element alone.
9A is a perspective view showing another specific example of the antenna element alone, and FIG. 9B is a cross-sectional view showing a horizontally polarized omnidirectional antenna using the antenna element.
FIG. 10 is a cross-sectional view showing another example of a horizontally polarized omnidirectional antenna.
11A is a cross-sectional view showing still another example of a horizontally polarized omnidirectional antenna, and FIG. 11B is a front view.
FIG. 12 is a front view showing another further example of the horizontally polarized omnidirectional antenna.
FIG. 13 is a sectional view showing still another example of a horizontally polarized omnidirectional antenna.
FIG. 14 is a front view showing a structure using a combination of a horizontally polarized omnidirectional antenna of the present invention in which antenna elements are bent so as to straddle side end surfaces of both ground plates and a conventional vertically polarized radiation antenna; It is.
FIG. 15 is a graph showing a measurement result of directivity of a horizontally polarized wave in a horizontal plane in the example.
16A is a front view of a conventional vertically polarized horizontal omnidirectional array antenna, and FIG. 16B is a cross-sectional view.
17A is a front view of a conventional horizontally polarized horizontal omnidirectional array antenna, FIG. 17B is a cross-sectional view, and FIG. 17C is a front view of a feed circuit board.
[Explanation of symbols]
1a, 1b Metallic conductive ground plates 1c, 1d Metal plates 2a, 2b Insulating plate 3 Printed circuit board (feeding circuit board)
4,5 Strip lines 6a-6d, 6a'-6d 'Antenna elements 7a, 7b Feed pins

Claims (7)

On one side of the center line, rectangular conductor ground planes are opposed to each other, and one feed circuit board is provided between the ground planes. On the outer surface of the conductor ground plane, a pair of antenna elements is provided in one stage or in multiple stages in the center line direction. The antenna arranged in the
Each antenna element constituting the pair of antenna elements is bent and arranged so as to straddle the side end surfaces of both base plates,
A power supply pin is provided on the power supply circuit board to penetrate both conductor ground planes and supply power to the pair of antenna elements.
A horizontally polarized omnidirectional antenna, wherein power is supplied to both antenna elements constituting the pair of antenna elements from both ends of the power supply pin. 2. The horizontally polarized omnidirectional antenna according to claim 1, wherein the side end surfaces of the conductor ground plates are bent. 2. The horizontally polarized omnidirectional antenna according to claim 1, wherein a metal plate for short-circuiting the conductor ground plates is attached to side end surfaces of the conductor ground plates. 2. The horizontally biased antenna according to claim 1, wherein each of the antenna elements constituting the pair of antenna elements is arranged substantially point-symmetrically when viewed from a center line direction, and the feed pin is provided upright on a center line of the feed circuit board. 3. Wave omnidirectional antenna. 5. The antenna according to claim 4, wherein the antenna element forming the pair of antenna elements is formed by bending a convex conductive plate into a U-shaped cross section, and the projecting portion is connected to the feed pin. 6. Directional antenna. The omnidirectional horizontally polarized antenna according to claim 1, wherein a shielding plate electrically connected to a conductive ground plane is interposed between the antenna elements constituting the pair of antenna elements. 2. The omnidirectional horizontally polarized antenna according to claim 1, wherein a dielectric is inserted between the antenna element and the conductive ground plane.

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