JP2006229646A - Antenna system for horizontal polarization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna system for horizontal polarization which has a broad band and a thinned diameter, and to provide a horizontally omnidirectional polarization antenna system. <P>SOLUTION: A skeleton slot antenna element 3 and a balanced-unbalanced conversion circuit 4 are integrally formed by printing on a dielectric board 2. In order to obtain horizontal plane non-directivity, the system includes: a first antenna unit 1-1 for the horizontal polarization which is constituted by integrally forming by printing the skeleton slot antenna element 3 and the balanced-unbalanced conversion circuit 4 on the dielectric board 2; and a second antenna unit 1-2 for the horizontal polarization which has a configuration being the same as that of the first antenna unit 1-1, which is perpendicularly combined with the first antenna unit 1-1 for the horizontal polarization in a state that their vertical center axes are mutually superimposed, and whose power feeding phase is made different by 90° relative to the first antenna unit 1-1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a horizontally polarized antenna device suitable for use in a base station such as a mobile communication system.

For example, in a mobile communication system, an antenna having omnidirectionality in a horizontal plane is used as a base station antenna in a place with a relatively small subscriber capacity. Many of these omnidirectional antennas are vertically polarized antennas, but sometimes horizontally polarized antennas are also used.
On the other hand, in recent years when the polarization diversity system has been actively adopted, there is a growing demand for a dual-polarized antenna that combines a vertically polarized antenna and a horizontally polarized antenna. For this reason, realization of a horizontally polarized omnidirectional antenna having a broadband as narrow as that of a vertically polarized omnidirectional antenna is desired.

As an example of a wide-band horizontally polarized omnidirectional antenna, a batwing type turn-style antenna used in television broadcasting is well known (for example, Non-Patent Document 1). In addition, a horizontally polarized omnidirectional antenna having a narrow diameter has also been proposed (for example, Patent Documents 1 and 2).
"Antenna Engineering Handbook", page 286 The Institute of Electrical Communication, October 30, 1955 Published by Ohm Co., Ltd. Japanese Patent Laid-Open No. 11-251832 JP 2000-196352 A

Taking a cellular phone system, which is a typical example of a mobile communication system, as an example, the frequency band currently used is 810 to 960 MHz in the 800 MHz band (approximately 17% of the specific band), and 1920 to 2170 MHz in the 2 GHz band (ratio). The bandwidth is about 12%). Therefore, the horizontally polarized omnidirectional antenna used in the base station of this cellular phone system is required to have a band characteristic of about 20% of the specific band.
On the other hand, it is desirable to make the horizontal polarization omnidirectional antenna as thin as possible from the viewpoint of aesthetics and wind pressure load. For this reason, the outer diameter of the vertical polarization omnidirectional antenna, that is, 0.3λ ( λ is required to have an outer diameter dimension equal to or less than the wavelength of the center frequency of the used frequency band.

  However, in general, it is difficult for a horizontally polarized omnidirectional antenna to achieve both a wider bandwidth and a smaller outer diameter compared to a vertically polarized omnidirectional antenna. This is because if the broadband characteristic is pursued, the outer diameter becomes thicker, and if the outer diameter is kept small, the broadband characteristic tends to be sacrificed.

For example, as is well known, the bat wing type turn style antenna described in the non-patent document has a broadband characteristic with a specific band of about 30%, but on the other hand, its outer diameter is as thick as 0.5λ or more. On the other hand, the horizontally polarized omnidirectional antennas described in Patent Documents 1 and 2 can have an outer diameter as thin as about 0.35λ. However, although this antenna is not specified, it is assumed that it is for PHS band (1893.5 to 1919.6 MHz) because it is an antenna for 1.9 GHz band. Therefore, there are many specific bands in which this antenna operates. Estimates are expected to remain around 10%.
As described above, the conventional horizontally polarized omnidirectional antenna, like the vertically polarized omnidirectional antenna, is difficult to achieve both wideband characteristics and a thin outer diameter.

  In view of such circumstances, an object of the present invention is to provide a horizontally polarized antenna device and a horizontal plane omnidirectional horizontally polarized antenna device capable of achieving a wide band and a narrow diameter.

  In order to achieve the above object, a first horizontally polarized antenna device according to the present invention has a configuration in which a skeleton slot antenna element and a flat-balance unbalance conversion circuit are integrally printed on a dielectric substrate.

  The second horizontally polarized antenna device according to the present invention is a first horizontally polarized wave antenna formed by integrally printing a skeleton slot antenna element and a counter-balance unbalance conversion circuit on a dielectric substrate. The antenna unit has the same configuration as the first horizontal polarization antenna unit, and is vertically combined with the first horizontal polarization antenna unit in a form in which the upper and lower central axes overlap each other. A second horizontally polarized antenna unit having a feeding phase different from that of the first horizontally polarized antenna unit by 90 °.

  Further, the third horizontally polarized antenna device according to the present invention has a plurality of horizontally polarized antenna blocks arranged in the vertical direction, and each horizontally polarized antenna block is flat with the skeleton slot antenna element. The first horizontal polarization antenna unit, which is formed by integrally printing an impulse / unbalance conversion circuit on a dielectric substrate, has the same configuration as the first horizontal polarization antenna unit, and The vertical center axes of the first horizontal polarization antenna unit and the first horizontal polarization antenna unit are combined at right angles so that the feed phase is 90 ° different from that of the first horizontal polarization antenna unit. A horizontally polarized antenna unit.

  The horizontal polarization antenna blocks of the third horizontal polarization antenna device can be made to have different mechanical rotation angles around the vertical center axis. In this case, the horizontal polarization antenna block is fed with a phase that individually compensates for the mechanical rotation angle. Such power feeding is achieved, for example, by adjusting the length of the power feeding cable connected to each of the horizontally polarized antenna blocks.

  In each of the horizontally polarized antenna devices, the skeleton slot antenna element is formed on one surface of the dielectric substrate, and the counterbalance unbalance conversion circuit is connected to the antenna from each feeding point of the skeleton slot antenna element. First and second lines extending in the vertical direction to the lateral conductor portion of the element, and a feed line formed on the other surface of the dielectric substrate can be provided. The feed line extends from the side of the lateral conductor through the back of the first line, reverses the direction through the back of each feed point, and then reverses at the back of the second line. It is formed to extend a predetermined length in the direction.

In each of the second and third horizontally polarized antenna devices, one or more metals along the vertical center axis are formed in a space formed between the first and second horizontally polarized antenna units. Posts can be provided.
Further, another antenna element, for example, an antenna element for vertical polarization or an antenna element applied to a different frequency band may be disposed in the space.

  According to the present invention, it is possible to provide a horizontally polarized antenna device having a small diameter and a wide band characteristic. In addition, it is possible to provide a horizontally polarized omnidirectional antenna device capable of realizing broadband characteristics and a thin outer diameter comparable to those of a vertically polarized omnidirectional antenna.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a known skeleton slot antenna. This skeleton slot antenna has a specific bandwidth of about 20% and is usually formed of a thin metal conductor such as a wire. This skeleton slot antenna has a horizontal length and a vertical length set to about 0.25λ and about 0.5λ, respectively (λ is the wavelength of the center frequency of the used frequency band), and is a separate component, balanced and unbalanced. Power is supplied from a power supply cable such as a coaxial cable via a conversion circuit (not shown). Symbols a and b indicate feed points of the skeleton slot antenna.

  FIG. 2 is a perspective view showing an embodiment of an antenna device for horizontal polarization according to the present invention, which is configured based on the skeleton slot antenna. The antenna device 1 includes a skeleton slot antenna element 3 and a balance-unbalance conversion circuit (balun) 4 formed by printing a metal foil (for example, copper foil) on a dielectric substrate 2.

  The skeleton slot antenna element 3 is formed on the surface of the dielectric substrate 2. The skeleton slot antenna element 3 has a shape similar to that of the skeleton slot antenna shown in FIG. 1, and includes horizontal conductor portions 3a and 3b (length of about 0.25λ) and vertical conductor portions 3c and 3d (length of about 0.1 mm). 5λ), an intermediate conductor portion 3e extending from the intermediate point of the vertical conductor portion 3c to the feeding point 5a and an intermediate conductor portion 3f extending from the intermediate point of the vertical conductor portion 3d to the feeding point 5b.

On the other hand, the balance-unbalance conversion circuit 4 is constituted by lines 6 a and 6 b formed on the surface of the dielectric substrate 2 and a feed line 7 formed on the back surface of the dielectric substrate 2.
The lines 6a and 6b extend downward from the feed points 5a and 5b of the skeleton slot antenna element 3 in parallel with each other, and their lower ends are coupled to the lower horizontal conductor portion 3b of the antenna element 3. Yes. The feed line 7 extends upward at the back of the feed line 6b, then reverses the direction through the 5a and 5b, and further extends downward by a predetermined length at the back of the feed line 6a.

  In this antenna device 1, the starting end portion of the feed line 7 located at the back of the lower conductor portion 3 b becomes the input / output end 8, and the internal conductor of an unbalanced feed cable such as a coaxial cable (not shown) is provided here. Connected. Moreover, the length of the site | part 7a located in the back part of the said feed line 6a is adjusted so that the feed line 7 may resonate to the center frequency of a use frequency band. The outer conductor of the power feeding cable is connected to the lateral conductor portion 3b.

Since the antenna device 1 according to this embodiment has a structure in which the balance-unbalance conversion circuit 4 is integrally formed on the dielectric substrate 2, the antenna device 1 operates only by connecting a power feeding cable to the input / output end 8. That is, the antenna device 1 has a function as a horizontally polarized antenna device that radiates horizontally polarized waves by feeding through the feeding cable, and has a maximum radiation direction in front of and behind the surface including the antenna element 3. Exhibits bi-directionality.
According to the antenna device 1 according to this embodiment, the skeleton slot antenna element 3 having excellent broadband characteristics is used as the antenna element, and the balance-unbalance conversion circuit 4 is integrally formed without increasing the overall shape. As a result, both broadband and compactness can be obtained. The outer diameter of the antenna device 1 is about 0.25λ, which is the length of the lateral conductor portions 3a and 3b.

  In addition, although the basic dimension of the antenna element 3 is as having shown in FIG. 1, about 10 to 20% may be changed according to a condition. Further, even if the lead positions of the intermediate conductor portions 3e and 3f from the vertical conductor portions 3c and 3d are offset to some extent in the vertical direction from the vertical center positions of the vertical conductor portions 3c and 3d, there is no practical problem.

FIG. 3 shows an embodiment of a horizontally polarized antenna device according to the present invention that is omnidirectional in a horizontal plane. The antenna device 10 has a configuration in which two horizontally polarized antenna units 1-1 and 1-2 having a configuration equivalent to that of the antenna device 1 shown in FIG.
As shown in FIG. 4, a slit 2a is formed at the center of the lower half of the dielectric substrate 2 of the antenna unit 1-1, and as shown in FIG. 5, the slit is formed on the dielectric substrate 2 of the antenna unit 1-2. A slit 2b is formed at the center of the half.
In the antenna device 10 of the present embodiment, the slit 2a of the antenna unit 1-1 is fitted to the lower half of the dielectric substrate 2 of the antenna unit 1-2, and the slit 2b of the antenna unit 1-2 is connected to the antenna unit 1-2. It is assembled by fitting to the upper half of the dielectric substrate 2 of 1-1.

  The horizontal conductor portions 3b of the antenna units 1-1 and 1-2 shown in FIG. 3 are divided at the central portions in accordance with the formation of the slits 2a and 2b shown in FIGS. After the combination of −1 and 1-2, each of the divided portions is electrically connected.

The antenna device 10 in which the antenna units 1-1 and 1-2 are combined has two input / output terminals 8, and one (upper) input / output terminal 8 of them has a feeding cable 9 such as a coaxial cable. And the other (lower) input / output terminal 8 is connected to the other output terminal of the two distributor 11 via a feeding cable 12.
The two distributors 11 require that the difference between the phase of the signal at one output end and the phase of the signal at the other output end be 90 °. Therefore, as the two distributors 11, one using a difference in line length as shown in the figure, one using a 90 ° hybrid circuit, or the like is used.

The directivity of the horizontal polarization of the antenna device 10 according to this embodiment is a combination of the directivity of the horizontal polarizations of the antenna units 1-1 and 1-2 combined at right angles. Become.
Further, the outer diameter of the antenna device 10 is about 0.00 mm because the length of the lateral conductor portions 3a and 3b of the skeleton slot antenna elements 3 of the antenna units 1-1 and 1-2 is about 0.25λ. 25λ.

FIG. 6 shows a horizontal sectional view of FIG. As shown in FIG. 6, metal struts 14 for supporting the antenna device 10 are disposed in the four space portions 13 formed by the orthogonal antenna units 1-1 and 1-2, respectively. Yes. Each support column 14 is separated from the antenna element 3 shown in FIG. 3 by an appropriate distance so as not to affect the operation of the antenna device 10.
The longitudinal direction of the support column 14 and the polarization direction of the antenna device 10 are orthogonal to each other. Therefore, if the thickness of each support column 14 is about 0.1λ or less, the effect of the support columns 14 on the antenna element 3 is small, and the current induced in these support columns 14 is also small. In addition to the role of increasing the strength of the antenna device 10, the support column 14 also has a role as a lightning conductor.

FIG. 7 schematically shows an antenna device 100 in which four antenna blocks 10-1, 10-2, 10-3, and 10-4 having the same configuration as the antenna device 10 shown in FIG. Show.
Two distributors 11-1 to 11-4 corresponding to the two distributors 11 shown in FIG. 3 are connected to the respective antenna blocks 10-1 to 10-4. The input terminals of the distributors 11-1 to 11-4 are connected to the corresponding output terminals of the four distributors 16 through power supply cables 15-1 to 15-4 such as coaxial cables, respectively.
According to the antenna device 100, by equalizing the lengths of the feeding cables 15-1 to 15-4, the electric field in the circumferential direction can be strengthened and the gain can be increased.

  The connection form of the power feeding cable is not limited to the form shown in FIG. 7, and there are several other types. For example, you may employ | adopt the connection form shown in FIG. In FIG. 8, one antenna unit 1-1 included in each of the antenna blocks 10-1 to 10-4 is connected to a corresponding output end of the four distributor 18 via power feeding cables 17-1 to 17-4, respectively. The other antenna unit 1-2 connected and included in each of the antenna blocks 10-1 to 10-4 is connected to a corresponding output end of the four distributor 20 via the feeding cables 19-1 to 19-4, respectively. Has been.

  One output terminal and the other output terminal of the two distributors 21 are connected to the input terminal of the distributor 18 and the input terminal of the distributor 20, respectively. The two distributors 21 need to have a phase difference of 90 ° between the signal at one output end and the signal at the other output end. Therefore, as the two distributors 21, one using a difference in line length as shown in the figure, one using a 90 ° hybrid circuit, or the like is used.

FIG. 9 schematically shows an antenna device 100 ′ in which the horizontal plane omnidirectional deviation characteristic and the input reflection characteristic are improved using the antenna apparatus 100 of FIG. 7 as a basic configuration.
The antenna device 100 ′ has a mechanical rotation angle around the central axis X (see FIG. 3) of the antenna block 10-1 as 0 °, and the other antenna blocks 10-2, 10-3, and 10-4 at the center. The antenna devices 10-2, 10-3, and 10 are rotated around the axis X by angles θ ₂ , θ _3, and θ ₄ , respectively, so as to compensate for electrical angles (phases) corresponding to these mechanical rotation angles. The lengths of the feeding cables 15-2, 15-3 and 15-4 with respect to 10-4 are adjusted.

In this example, the mechanical rotation angles θ ₂ , θ ₃ and θ ₄ are set to about 90 °, 2 × 90 ° and 3 × 90 °, respectively. The lengths of the feeding cables 25-2, 25-3, and 25-4 are adjusted so that the target angle (phase) is compensated. Here, assuming that the lengths of the feeding cables 15-1, 15-2, 15-3 and 15-4 are l ₁ , l ₂ , l ₃ and l ₄ , respectively, l ₁ <l ₂ <l ₃ <l ₄ It becomes.

The arrangement form of the antenna blocks 10-1 to 10-4 in the antenna device 100 ′ is called a so-called sequential arrangement, and has been conventionally applied to a planar antenna that radiates circularly polarized waves.
When this sequential arrangement is applied to a circularly polarized flat antenna, an improvement in the circular polarization rate (axial ratio) and an improvement in input reflection characteristics are expected.
On the other hand, in the case of the antenna device 100 ′ shown in FIG. 9 to which this sequential arrangement is applied, an improvement in the omnidirectional characteristic (deviation characteristic) of the horizontal plane directivity and an improvement in the input reflection characteristic are expected.

  That is, since the antenna units (1-1, 1-2) of the antenna blocks 10-1 to 10-4 constituting the antenna device 100 ′ have different mechanical rotation angles, the antenna blocks 10-1 to 10-4 have different mechanical rotation angles. The horizontal plane directivity of -1 to 10-4 is averaged, and the directivity deviation is reduced. Further, since the feeding phases to the respective antenna blocks 10-1 to 10-4 are different, the reflected waves from the respective antenna blocks 10-1 to 10-4 are canceled by the distributor 16 near the input end. As a result, the reflection characteristics viewed from the input end are improved.

10 and 11 show examples of the horizontal plane directivity and the input reflection characteristic of the antenna device 100 ′, respectively.
As is clear from FIG. 10, according to the antenna device 100 ′, the horizontal plane directivity deviation can be reduced within 1 dB to obtain a good horizontal plane non-directivity, and as is clear from FIG. It is possible to obtain a specific bandwidth of 20% or more at VSWR of 1.5 or less. In FIG. 11, f ₀ represents the center frequency of the used frequency band.

The technique of the present invention is not limited to the technique in the above-described embodiment, and various modifications and additions are possible within the technical scope described in the claims.
For example, in the antenna device 10 shown in FIG. 3, the balance-unbalance conversion circuit 7 on the antenna unit 1-1 side is positioned on the lower side, and the balance-unbalance conversion circuit 4 on the antenna unit 1-2 side is positioned on the upper side. However, these antenna units 1-1 and 1-2 may be combined so that the balance-unbalance conversion circuit 4 of both antenna units 1-1 and 1-2 is located on the lower side or the upper side. Is possible.

Moreover, the number of the support | pillars 14 arrange | positioned in the space part 13 shown in FIG. 6 may be two or more, Furthermore, instead of the support | pillar 14, another thin antenna element, for example, the antenna element for vertical polarization Alternatively, an antenna element or the like that is applied to a different frequency band can be provided. And the said support | pillar 14 and another thin antenna element are applicable also to the antenna apparatus 100 shown in FIG. 7, FIG.
Furthermore, in the antenna device shown in FIGS. 7, 8, and 9, a plurality of antenna blocks having the same configuration as the antenna device 10 having the configuration shown in FIG. 3 are arranged in the vertical direction. The number of blocks arranged can be set arbitrarily.

  The antenna device for horizontally polarized waves according to the present invention can obtain a wide band characteristic (20% relative bandwidth) sufficient for use in a mobile communication system, and has a thin outer diameter (0.3λ or less) to reduce wind pressure. Since the load can be reduced, the strength can be improved, and the appearance can be improved, it is particularly suitable as a base station antenna for mobile communication. In addition, the horizontally polarized antenna device according to the present invention can have the same outer diameter as that of the vertically polarized omnidirectional antenna having the same characteristics. By combining the antenna devices, it is possible to realize the antenna device having an outer diameter thinner than that of the conventional polarized wave omnidirectional antenna device.

It is a conceptual diagram which shows the skeleton slot antenna used as the basis of the antenna apparatus which concerns on this invention. 1 is a perspective view schematically showing an embodiment of a horizontally polarized antenna device according to the present invention. 1 is a perspective view schematically showing an embodiment of a horizontal omnidirectional horizontally polarized antenna device according to the present invention. It is a perspective view which shows the slit provided in one dielectric substrate shown in FIG. It is a perspective view which shows the slit provided in the other dielectric substrate shown in FIG. FIG. 4 is a cross-sectional view of FIG. 3 in the horizontal direction. It is a conceptual diagram which shows embodiment of the horizontal surface non-directional horizontal polarization antenna apparatus of the multistage structure which concerns on this invention. It is a conceptual diagram which shows the connection form from which the electric power feeding cable in the antenna apparatus of FIG. 7 differs. It is a conceptual diagram which shows the modification of the antenna apparatus of FIG. 10 is a graph illustrating an example of horizontal plane directivity of the antenna device of FIG. 9. 10 is a graph illustrating an example of input reflection characteristics (VSWR) of the antenna device of FIG. 9.

Explanation of symbols

1, 10, 100, 100 ′ Horizontally polarized antenna device 1-1, 1-2 Horizontally polarized antenna unit 2 Dielectric substrate 3 Skeleton slot antenna element 4 Balance / unbalance conversion circuit 5a, 5b Feed point 6a, 6b Line 7 Feed line 8 Input / output end 9, 12 Feed cable 10-1 to 10-4 Horizontally polarized antenna block 15-1 to 15-4, 17-1 to 17-4, 19-1 to 19-4 Feed cable 11, 16, 18, 20, 21 Distributor 14 Prop

Claims (8)

  A horizontally polarized antenna device, wherein a skeleton slot antenna element and a counter-balance unbalance conversion circuit are integrally printed on a dielectric substrate. A first horizontally polarized antenna unit formed by integrally printing a skeleton slot antenna element and a counter-balance unbalance conversion circuit on a dielectric substrate;
The first horizontal polarization antenna unit has a configuration similar to that of the first horizontal polarization antenna unit, and is vertically combined with the first horizontal polarization antenna unit in a form in which the upper and lower central axes overlap each other. A second horizontally polarized antenna unit whose feed phase is 90 ° different from that of the horizontally polarized antenna unit;
An antenna device for horizontal polarization, comprising: A plurality of horizontally polarized antenna blocks arranged in the vertical direction, each horizontally polarized antenna block,
A first horizontally polarized antenna unit formed by integrally printing a skeleton slot antenna element and a counter-balance unbalance conversion circuit on a dielectric substrate;
The first horizontal polarization antenna unit has a configuration similar to that of the first horizontal polarization antenna unit, and is vertically combined with the first horizontal polarization antenna unit in a form in which the upper and lower central axes overlap each other. A second horizontally polarized antenna unit whose feed phase is 90 ° different from that of the horizontally polarized antenna unit;
An antenna device for horizontal polarization, comprising:   Each of the horizontally polarized antenna blocks is fed with a mechanical rotation angle different from each other around the vertical central axis and having a phase that individually compensates for the mechanical rotation angle. An antenna device for horizontal polarization characterized by the above. The skeleton slot antenna element is formed on one surface of the dielectric substrate,
The counter-balance unbalance conversion circuit is formed on first and second lines extending in the vertical direction from each feeding point of the skeleton slot antenna element to a lateral conductor portion of the antenna element, and on the other surface of the dielectric substrate. A power feed line,
The feed line extends from the lateral conductor portion side through the back portion of the first line, reverses the direction through the back portion of each feed point, and then reverses in the back portion of the second line. 4. The horizontally polarized antenna device according to claim 1, wherein the antenna device is formed to extend a predetermined length.   4. One or more metal struts along the vertical axis are arranged in a space formed between the first and second horizontally polarized antenna units. A horizontally polarized antenna device according to claim 1.   4. The horizontally polarized antenna according to claim 1, wherein another antenna element is disposed in a space formed between the first and second horizontally polarized antenna units. apparatus.   8. The horizontally polarized antenna device according to claim 7, wherein the another antenna element is a vertically polarized antenna element or an antenna element applied to a different frequency band.

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