JP3735058B2 - Horizontally polarized omnidirectional antenna device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a horizontally polarized omnidirectional antenna device used for a wireless LAN base station, for example.
[0002]
[Prior art]
Conventionally, a wireless LAN base station is required to have a non-directional antenna characteristic in order to communicate with a terminal. For this reason, for example, in a wireless LAN outdoor base station, a collinear antenna with vertical polarization non-directivity is currently widely used.
[0003]
[Problems to be solved by the invention]
As described above, conventionally, a vertically polarized omnidirectional collinear antenna is generally used as a wireless LAN antenna, but recently, a horizontally polarized omnidirectional antenna is also considered. However, a horizontally polarized omnidirectional antenna generally has a larger diameter than a vertically polarized omnidirectional antenna, which is disadvantageous in terms of weight and wind pressure load. For this reason, conventionally, a horizontally polarized omnidirectional antenna is not often used.
[0004]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a horizontally polarized omnidirectional antenna device that has a simple structure, a small diameter, and can be miniaturized.
[0005]
[Means for Solving the Problems]
A horizontally polarized omnidirectional antenna device according to the present invention includes a first antenna in which a pair of mountain-shaped antenna elements having a length of approximately λ / 6 are arranged facing each other, and an upper portion of the first antenna. And a second antenna composed of a pair of mountain-shaped antenna elements having a length of approximately λ / 6, which are disposed with a spacing of approximately λ / 4, and an upper portion of the second antenna, approximately λ / 4. A third antenna comprising a pair of mountain-shaped antenna elements having a length of approximately λ / 6 and an arm having a length of approximately λ / 8 provided at the tip of the pair of antenna elements disposed at a distance of approximately λ / 6; A feeding means for feeding power to an end of the antenna element such that a current of opposite phase flows through each antenna element constituting the first antenna; and a current having the same phase as that of the first antenna; The first antenna so that it flows through the antenna 3 Between the second antenna, and wherein the second antenna; and a feed line that connects the third antenna.
[0006]
With the above-described configuration, the diameter can be reduced with a simple structure, and the directivity in the horizontal plane can be made non-directional with a deviation within 1 dB. In addition, the directivity in the horizontal plane can be adjusted by finely adjusting the length and interval of the arms provided in the antenna element constituting the third antenna.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a basic configuration of a horizontally polarized omnidirectional antenna apparatus according to an embodiment of the present invention.
[0008]
In FIG. 1, reference numeral 1 denotes a first antenna, which is a pair of mountain-shaped antenna elements 1a, 1b having a length of approximately λ (wavelength) / 6 and is disposed facing each other, and the tip of each antenna element 1a, 1b. Power is fed from a feeding point 2 provided in the section.
[0009]
Then, the second antenna 3 is arranged on the upper portion of the first antenna 1 with an interval of approximately λ / 4. The second antenna 3 includes a pair of mountain-shaped antenna elements 3a and 3b having a length of approximately λ / 6. In addition, the feed line 4 connects the end portions of the first antenna 1 and the second antenna 3 so that a current i having the same phase as that of the first antenna 1 flows through the second antenna 3.
[0010]
In addition, the third antenna 5 is disposed on the second antenna 3 with an interval of approximately λ / 4. The third antenna 5 has a pair of mountain-shaped antenna elements 5a and 5b having a length of approximately λ / 6 as in the case of the second antenna 3, and is disposed so as to face each other. The arms 6a and 6b are provided in parallel toward the second antenna 3 side. Further, the feed line 7 connects the end portions of the second antenna 3 and the third antenna 5 so that the current i having the same phase as that of the second antenna 3 flows to the third antenna 5.
[0011]
In the above-described configuration, the length of the arms 6a and 6b of the third antenna 5 and the distance Δg are finely adjusted so that the horizontal polarization in the horizontal plane becomes non-directional. Since the currents flowing through the arms 6a and 6b are in opposite phases, no radio waves are emitted.
[0012]
On the other hand, in the first antenna 1, currents in opposite phases flow through the antenna elements 1 a and 1 b, but radio waves are radiated because the flowing directions are the same. Further, since the current having the same phase as the first antenna 1 flows through the second antenna 3 and the third antenna 5, the radio wave is efficiently radiated.
[0013]
Next, a specific configuration example of the horizontally polarized omnidirectional antenna device will be described with reference to FIGS. 2A is a perspective view of the front side of the horizontally polarized omnidirectional antenna device according to the embodiment of the present invention, and FIG. 2B is a perspective view of the back side. 3 is a perspective view showing a specific example of a single antenna element, FIG. 4A is a front view showing a feeding circuit portion, FIG. 4B is a rear view thereof, and FIG. 4C is a feeding end side. FIG. 5 is a side view showing the overall configuration, and FIG. 6 is a cross-sectional view showing a state where the antenna is mounted on the radome.
[0014]
In FIG. 2, 11 is a dielectric substrate, for example, a copper foil substrate, having a relative dielectric constant of 2.2 and a thickness of about 0.8 mm. Then, on the front side of the substrate 11, as shown in FIG. 2A, one of the antenna elements 1a, 3a, 5a of the first, second, and third antennas 1, 3, and 5 is approximately λ / 4. Install at intervals of.
[0015]
Further, on the back surface of the substrate 11, as shown in FIG. 2B, the other antenna elements 1b, 3b, and 5b of the first, second, and third antennas 1, 3, and 5 are connected to the antenna elements on the front side. It is mounted at a position facing 1a, 3a and 5a. Each element of the antennas 1, 3, and 5 uses a conductor such as copper or brass, and has a shape called a blues antenna (a meander line having one side of λ / 4) formed in a mountain shape. That is, each antenna element is formed in a mountain shape by bending a rectangular conductor plate at the center as shown in FIG. Furthermore, the arms 6 a and 6 b of the third antenna 5 are provided on the substrate 11. The arms 6a and 6b are formed by a microstrip line having a length of λ / 8.
[0016]
Further, as shown in FIGS. 2 (a) and 4 (a), on the front side of the substrate 11, a feed line constituted by a microstrip line 12a is provided, and a split balun 13 is provided at the base. As shown in FIG. 4C, the split balun 13 has a ground portion 15 and a line 16 made of copper foil on the upper surface of a dielectric substrate 14. In this case, the ground portion 15 is formed in the lower half of the substrate 14, and the line 16 is formed upward from the upper center of the ground portion 15. Further, the upper end of the line 16 is extended to the upper end surface of the substrate 14 to form a short line 16a, and the short line 16a is connected to the microstrip line 12a. The microstrip line 12a is provided from the base of the substrate 11 toward the first antenna 1, and is connected to the short line 16a of the split balun 13 in the middle thereof. Further, the substrate 14 is provided with a notch 17 in the lower center so that the lower end of the microstrip line 12a is exposed so that it can be connected to an external circuit (a connector 19 described later).
[0017]
On the other hand, as shown in FIGS. 2B and 4B, a grounding portion 18 is provided at the base on the back side of the substrate 11, and the first antenna is connected to the grounding portion 18 through the microstrip line 12b. It connects with the feeding point of antenna element 1a, 1b.
[0018]
Further, between the antenna elements 1 a and 1 b of the first antenna 1 and the antenna elements 3 a and 3 b of the second antenna 3 and between the antenna elements 3 a and 3 b of the second antenna 3 and the antenna element of the third antenna 5. 5a and 5b are connected by feed lines (microstrip lines) 4 and 7, respectively.
[0019]
4A, 4B, and 5, the external connection connector 19 is attached to the base of the substrate 11, and the microstrip line 12a formed on the upper surface of the substrate 11, the rear surface of the substrate 11. Are connected to the grounding portion 18 formed in the above and the grounding portion 15 of the split balun 13.
[0020]
Further, a radome 20 as shown in FIG. 6 is provided on the outside of the antenna for protection as required.
[0021]
As shown in the embodiment, the antenna elements of the first, second, and third antennas 1, 3, and 5 are mounted on both sides of the substrate 11 on which the feed line is formed in the center, and the antenna element is a plate. By forming in the shape, the radiation resistance and the band can be improved.
[0022]
In the horizontal polarization omnidirectional antenna device, the center frequency is 5250 MHz, the antenna elements of the first, second, and third antennas 1, 3, and 5 have a total length of 25.5 mm (0.446λ) and a total width of 6 mm (0 .105λ), the return loss characteristic shown in FIG. 7, the directivity in the horizontal plane shown in FIG. 8, and the directivity in the vertical plane shown in FIG. 9 were obtained. In the antenna device, an FRP having an outer diameter of 12 mm and a thickness of 0.5 mm was used as the radome 20, and the overall length of the antenna device was 130 mm.
[0023]
In the return loss characteristic shown in FIG. 7, it can be set to −9.5 dB (VSWR≈2.0) or less at 5.190 to 5.305 GHz. The operating gain at this time was about 2 dBi.
[0024]
In the horizontal plane directivity shown in FIG. 8, a non-directional characteristic was obtained with a deviation within 1 dB.
The vertical plane directivity shown in FIG. 9 has an 8-shaped characteristic having a high gain in the horizontal direction.
By constructing an antenna element having a simple shape on a single substrate 11 as described above, the antenna element and the feeding circuit can be integrated to reduce weight and size, and a horizontally polarized wave with a thin diameter and high gain. An omnidirectional antenna device could be realized.
[0025]
In the above embodiment, the case where the antenna has a single-stage configuration has been described. However, the gain can be improved by further configuring the antenna in multiple stages. For example, when the antenna has a two-stage configuration, an operation gain of about 5 dBi can be obtained, and when the antenna has a four-stage configuration, an operation gain of about 7 dBi can be obtained.
[0026]
FIG. 10 shows an example in which the horizontally polarized omnidirectional antenna apparatus has a four-stage configuration. The length of the substrate 11 is set in accordance with the multi-stage configuration, and the first to fourth stage antennas 21 to 24 are mounted at a predetermined interval. Since the first to fourth stage antennas 21 to 24 have the same configuration as the one-stage antenna described above, detailed description thereof is omitted.
[0027]
On the front side of the substrate 11, a feed line previously configured with a microstrip line 12 a is provided. The microstrip line 12a is provided from the base of the substrate 11 toward the first stage antenna 21 and is connected to the short line 16a at the tip of the split balun in the middle. That is, the split balun 13 is provided at the base portion on the front side of the substrate 11 as in the case of the one-stage configuration, and the short line 16a at the tip end of the split balun and the microstrip line 12a are connected.
[0028]
Then, the microstrip line 12a is extended to the second stage antenna 22, and a branching portion 25 is provided at the extended portion to branch in the vertical direction (the direction of the first stage antenna 21 and the third stage antenna 23). .
[0029]
The microstrip line 12a branched downward in the branching section 25 extends to the first stage antenna 21, and is branched in the vertical direction by the branching section 26 to be divided into the first stage antenna 21 and the second stage antenna. Power is supplied to 22.
[0030]
Further, the microstrip line 12a branched upward in the branching portion 25 extends to the third stage antenna 23, and is branched in the vertical direction by the branching portion 27 to be separated from the third stage antenna 23 and the fourth stage. The antenna 24 is fed.
[0031]
Similarly, power is supplied to the first to fourth stage antennas 21 to 24 on the back side of the substrate 11.
By the above power feeding means, power can be fed to the first to fourth stage antennas 21 to 24 under the same conditions.
[0032]
In the four-stage horizontally polarized omnidirectional antenna device, the return loss characteristic shown in FIG. 11, the horizontal plane directivity shown in FIG. 12, and the vertical plane directivity shown in FIG. 13 were obtained.
[0033]
In the return loss characteristic shown in FIG. 11, −9.5 dB (VSWR≈2.0) or less could be achieved at 5.250 to 5.350 GHz. The operating gain at this time was about 7 dBi.
[0034]
In the horizontal plane directivity shown in FIG. 12, the non-directional characteristic was obtained with a deviation within 1 dB as in the case of the antenna device having a single stage configuration.
Further, in the vertical in-plane directivity shown in FIG. 13, sharper 8-shaped characteristics were obtained than the one-stage antenna device due to the improvement of the operation gain.
By configuring the antenna in multiple stages as described above, the operation gain can be improved according to the number of stages.
[0035]
In the above embodiment, the case where the antenna element is formed in a mountain shape has been described. However, a semicircular shape or a polygon approximated to a semicircular shape, for example, a trapezoidal shape, may be used. Characteristics can be obtained.
[0036]
【The invention's effect】
As described in detail above, according to the present invention, the gain is small, the diameter is small, the size can be reduced, and the directivity in the horizontal plane can be made omnidirectional with a deviation within 1 dB. The horizontally polarized omnidirectional antenna apparatus can be provided. In addition, the directivity in the horizontal plane can be adjusted by finely adjusting the length and interval of the arms provided in the antenna element constituting the third antenna.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of a horizontally polarized omnidirectional antenna device according to an embodiment of the present invention.
2A is a front perspective view showing a specific configuration example of a horizontally polarized omnidirectional antenna device according to the embodiment, and FIG. 2B is a rear perspective view of the same.
FIG. 3 is a perspective view showing a specific example of a single antenna element in the embodiment.
4A is a front view showing a power feeding circuit portion in the embodiment, FIG. 4B is a rear view thereof, and FIG. 4C is a front view of a split balun.
FIG. 5 is a side view of the horizontally polarized omnidirectional antenna device according to the embodiment.
FIG. 6 is a cross-sectional view of a horizontally polarized omnidirectional antenna device according to the embodiment.
FIG. 7 is a view showing a return loss characteristic of the horizontally polarized omnidirectional antenna device according to the embodiment.
FIG. 8 is a view showing the horizontal directivity of the horizontally polarized omnidirectional antenna device according to the embodiment;
FIG. 9 is a view showing the vertical in-plane directivity of the horizontally polarized omnidirectional antenna device according to the embodiment;
FIG. 10 is a front view when the horizontally polarized omnidirectional antenna device according to the present invention has a four-stage configuration.
FIG. 11 is a view showing a return loss characteristic of the horizontally polarized omnidirectional antenna device according to the embodiment.
FIG. 12 is a diagram showing the directivity in the horizontal plane of a horizontally polarized omnidirectional antenna device having a four-stage configuration.
FIG. 13 is a diagram showing the vertical in-plane directivity of a horizontally polarized omnidirectional antenna apparatus having a four-stage configuration.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st antenna 1a, 1b ... Antenna element 2 ... Feed point 3 ... 2nd antenna 3a, 3b ... Antenna element 4 ... Feed line 5 ... 3rd antenna 5a, 5b ... Antenna element 6a, 6b ... Arm 7 ... feed line 11 ... boards 12a, 12b ... microstrip line 13 ... split balun 14 ... split balun board 15 ... earth part 16 ... line 16a ... short line 17 ... notch 18 ... earth part 19 ... connector 20 ... radome 21 ... First stage antenna 22 ... Second stage antenna 23 ... Third stage antenna 24 ... Fourth stage antennas 25, 26, 27 ... Branch

Claims (5)

A first antenna in which a pair of mountain-shaped antenna elements having a length of approximately λ / 6 are disposed facing each other;
A second antenna comprising a pair of mountain-shaped antenna elements having a length of approximately λ / 6 and disposed on the upper portion of the first antenna with a spacing of approximately λ / 4;
A pair of mountain-shaped antenna elements having a length of approximately λ / 6 disposed at an upper portion of the second antenna with a spacing of approximately λ / 4, and a length of approximately λ / 8 provided at the tip thereof. A third antenna comprising an arm having a thickness;
A power feeding means for feeding power to an end of the antenna element such that a current having an opposite phase flows to each antenna element constituting the first antenna;
Between the first antenna and the second antenna and between the second antenna and the third antenna so that a current having the same phase as that of the first antenna flows through the second antenna and the third antenna. A horizontally polarized omnidirectional antenna device comprising: a feed line connecting the two. In horizontal polarization omnidirectional antenna device according to claim 1, first to second, Mu horizontal polarization, characterized in that the formation of the respective antenna elements constituting the third antenna substantially semicircular or substantially trapezoidal Directional antenna device. In horizontal polarization omnidirectional antenna according to claim 1 wherein the first, second, one of the antenna elements forming the third antenna is provided on a surface of the dielectric substrate, the other of said antenna elements Is provided on the other surface of the dielectric substrate. 4. A horizontally polarized omnidirectional antenna device comprising a radome provided outside the horizontally polarized omnidirectional antenna device according to claim 1. 4. A horizontally polarized omnidirectional antenna device according to claim 1, 2 or 3, wherein the horizontally polarized omnidirectional antenna device is provided in multiple stages.

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