JP2004266499A - Flat antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize reduction of cross polarization of both of two orthogonal polarization in a prescribed covered area on a prescribed observation surface by selecting the optimum value of a relative dielectric constant or thickness of a dielectric substrate. <P>SOLUTION: In this flat antenna system, the dielectric substrate is arranged between a ground conductor and an excitation element, it has two orthogonal feeding points and the dielectric substrate has the relative dielectric constant ε<SB>r</SB>which equalizes relation F(ε<SB>r</SB>) between the maximum value F[dB] of the cross polarization level and the relative dielectric constant ε<SB>r</SB>of the dielectric substrate in the prescribed covered area on the prescribed observation surface in the case of feeding power from one of the feeding points to relation G(ε<SB>r</SB>) between the maximum value G[dB] of the cross polarization level and the relative dielectric constant ε<SB>r</SB>of the dielectric substrate in the prescribed covered area on the prescribed observation surface in the case of feeding power from the other of the feeding points. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

となる。ここで、
【数７】

であり、ｋ_０ は自由空間の波数、Ｖ_０ は定数である。
【００１６】
式（１）、（２）についてｒ、α、β座標からｒ，θ，φ座標への座標変換を行い、電界のθ成分Ｅ_θ 、φ成分Ｅ_φ を求める。そうすると、Ｈ偏波励振した場合には、主偏波はＥ_φ 、交差偏波はＥ_θ となるので、Ｈ偏波励振した場合の交差偏波レベルは、
【数８】

となる。また、Ｖ偏波励振した場合には、主偏波はＥ_θ 、交差偏波はＥ_φ となるので、Ｖ偏波励振した場合の交差偏波レベルは、
【数９】

となる。式（４）から、Ｈ偏波励振時には誘電体基板の比誘電率ε_ｒ が大きくなるにつれ交差偏波レベルが小さくなることが分かる。逆に、式（５）から、Ｖ偏波励振時には誘電体基板の比誘電率ε_ｒ が大きくなるにつれ交差偏波レベルが大きくなることが分かる。
【００１７】
例えば、式（４）、（５）にθ＝８１°を代入し、θ＝８１°観測面での交差偏波レベルの誘電体基板の比誘電率ε_ｒ に対する依存性を求めると、それぞれ図７、図８のようになる。さらに、例えば、覆域φ＝−４０°〜４０°内での交差偏波レベルの最大値を求めると、図７および図８よりφ＝±４０°の時に式（４）、（５）は最大となり、Ｈ偏波励振時とＶ偏波励振時の覆域φ＝−４０°〜４０°内での交差偏波レベルの最大値と誘電体基板の比誘電率ε_ｒ との関係は図９のようになる。
【００１８】
図９において、直交する２偏波双方の交差偏波レベルを同程度まで下げるためには、基板誘電率ε_ｒ を、Ｈ偏波励振時とＶ偏波励振時のθ＝８１°観測面の覆域φ＝−４０°〜４０°内における交差偏波レベルの最大値が等しくなるε_ｒにすれば良いことが分かる。このε_ｒを求めるとε_ｒ ＝１．７６となる。
【００１９】
以上のように、実施の形態３によれば、グランド導体５と誘電体基板４をｙ，ｚ方向に無限とした場合に、式（４）と式（５）から、Ｈ偏波励振時とＶ偏波励振時の、θが一定またはφが一定の所定の観測面における交差偏波レベルを求め、この時、所定の覆域内において、式（４）と式（５）の最大値が等しくなるような誘電体基板４の比誘電率ε_ｒ を求めるようにしたので、θが一定またはφが一定の所定の観測面における所定の覆域内において、直交する２偏波双方の交差偏波レベルを同程度まで低減することができる効果が得られる。
【００２０】
実施の形態４．
図１０はこの発明の実施の形態４による平面アンテナ装置の構造体を示す２面図で、図１０（ａ）は正面図、（ｂ）は断面図である。図において、図１に相当する部分には同一符合を付して示す。この場合、２次励振素子９が、励振素子１の近傍に配置され、励振素子１からの電磁波によって間接的に励振されるように構成されている。誘電体基板１０がグランド導体５と励振素子１の間および励振素子１と２次励振素子９の間にそれぞれ複数個Ｎ（Ｎ＞１）配置される。この誘電体基板１０の一部は空気層で形成されてもよい。ここで、Ｎ個の誘電体基板１０のうち、ｎ番目の誘電体基板の比誘電率をε_ｒｎ、厚さをｔ_ｎ とする。
【００２１】
所定の観測面における所定の覆域内の交差偏波レベルを考える。数値計算あるいは測定をおこなうことにより、一方の給電点２から給電した場合の所定の観測面における所定の覆域内の交差偏波レベルの最大値Ｆ［ｄＢ］とｎ番目の誘電体基板の比誘電率ε_ｒｎとの関係Ｆ（ε_ｒｎ）と、もう一方の給電点３から給電した場合の所定の観測面における所定の覆域内の交差偏波レベルの最大値Ｇ［ｄＢ］とｎ番目の誘電体基板の比誘電率ε_ｒｎとの関係Ｇ（ε_ｒｎ）を得る。
【００２２】
一般に、ｎ番目の誘電体基板の比誘電率ε_ｒｎの増加に伴うＦ（ε_ｒｎ）とＧ（ε_ｒｎ）の増減の方向は逆となっている。したがって、上記実施の形態１と同じように、ｎ番目の誘電体基板の比誘電率ε_ｒｎを上記Ｆ（ε_ｒｎ）と上記Ｇ（ε_ｒｎ）が等しくなるようにおけば、直交する２偏波双方の交差偏波レベルを同程度まで低減することができる。
【００２３】
同様に、数値計算あるいは測定をおこなうことにより、一方の給電点２から給電した場合の所定の観測面における所定の覆域内の交差偏波レベルの最大値Ｆ［ｄＢ］とｎ番目の誘電体基板の厚さｔ_ｎ との関係Ｆ（ｔ_ｎ ）と、もう一方の給電点３から給電した場合の所定の観測面における所定の覆域内の交差偏波レベルの最大値Ｇ［ｄＢ］とｎ番目の誘電体基板の厚さｔ_ｎ との関係Ｇ（ｔ_ｎ ）を得る。
一般に、ｎ番目の誘電体基板の厚さｔ_ｎ の増加に伴うＦ（ｔ_ｎ ）とＧ（ｔ_ｎ）の増減の方向は逆となっている。したがって、ｎ番目の誘電体基板の厚さｔ_ｎ を選ぶことにより上記Ｆ（ｔ_ｎ ）と上記Ｇ（ｔ_ｎ ）を等しくすることができる。
【００２４】
以上のように、実施の形態４によれば、上記Ｆ（ε_ｒｎ）と上記Ｇ（ε_ｒｎ）が等しくなるｎ番目の誘電体基板の比誘電率ε_ｒｎを設定するようにしたので、直交する２偏波双方の交差偏波レベルを同程度まで低減できる効果が得られる。一方、上記Ｆ（ｔ_ｎ ）と上記Ｇ（ｔ_ｎ ）を等しくするｎ番目の誘電体基板の厚さｔ_ｎ を設定するようにしても、同様に、直交する２偏波双方の交差偏波レベルを同程度まで低減できる効果が得られる。
【００２５】
実施の形態５．
この実施の形態５は、図１０のグランド導体５と誘電体基板４がｙ，ｚ方向に無限であるとした場合に、理論式から上記実施の形態４の効果を明らかにするものである。図１１はこの発明の実施の形態５による平面アンテナ装置の構造体を示す２面図で、図１１（ａ）は正面図、（ｂ）はＡ−Ａ断面図である。図において、図１０に相当する部分には同一符合を付して示す。励振素子１および２次励振素子９は矩形とする。給電点２に給電した時に励振される偏波をＨ偏波、給電点３に給電した時に励振される偏波をＶ偏波とする。また、Ｎ個の誘電体基板１０のうちｎ番目の誘電体基板の比誘電率をε_ｒｎ、厚さをｔ_ｎ とする。図４のｘ，ｙ，ｚ座標とｒ，θ，φ座標との関係を使用する。
【００２６】
図１１おいて、放射に主として寄与するのは２次励振素子９であるので、２次励振素子９の放射特性を考えればよい。また、２次励振素子９から見た等価比誘電率ε_ｒｅｆｆは、
【数１０】

と定義することができる。したがって、上記実施の形態３においてキャビティモデルより求めた交差偏波レベル式（４）、（５）のε_ｒ を、式（６）のε_ｒｅｆｆで置き換えることによって、図１１の平面アンテナの交差偏波レベルを求めることができる。Ｈ偏波励振した場合の交差偏波レベル、すなわちｙ軸上に設けられた給電点から給電した場合の交差偏波の振幅｜Ｅ_θ ｜と主偏波の振幅｜Ｅ_φ ｜から得る交差偏波レベルは、
【数１１】

となり、Ｖ偏波励振した場合の交差偏波レベル、すなわちｚ軸上に設けられた給電点から給電した場合の交差偏波の振幅｜Ｅ_φ ｜と主偏波の振幅｜Ｅ_θ ｜による交差偏波レベルは、
【数１２】

となる。
【００２７】
式（７）から、Ｈ偏波励振時には等価比誘電率ε_ｒｅｆｆが大きくなるにつれ交差偏波レベルが小さくなることが分かる。逆に、式（８）から、Ｖ偏波励振時には等価比誘電率ε_ｒｅｆｆが大きくなるにつれ交差偏波レベルが大きくなることが分かる。したがって、式（７）と式（８）が等しくなる等価比誘電率ε_ｒｅｆｆが存在することになる。
【００２８】
以上のように、実施の形態５によれば、グランド導体５と誘電体基板４を無限とした場合に、θが一定またはφが一定の所定の観測面における所定の覆域内において、式（７）と式（８）が等しくする等価比誘電率ε_ｒｅｆｆを求めるようにしたので、直交する２偏波双方の交差偏波レベルを同程度まで低減できる効果が得られる。
【００２９】
実施の形態６．
この実施の形態６は、給電ピンではなく給電線路を用いて励振素子を励振させた場合に、上記実施の形態１〜実施の形態５と同じ効果あることについて述べる。図１２はこの実施の形態６における平面アンテナ装置の構造体を示す２面図で、図１２（ａ）は正面図、（ｂ）はＡ−Ａ断面図である。図において、図１に相当する部分には同一符合を付して示す。ここでは、給電ピンの代わりに、給電線路１１，１２が励振素子１と同じ平面に設けられている。
励振素子１は、２つの給電線路１１，１２によって給電され、励振され、直交する偏波を発生し、実施の形態１乃至実施の形態３で述べたと同様に、直交２偏波共用アンテナとして動作する。また、アンテナ構造体として、上記実施の形態４の図１０に示すように、励振素子１の近傍に２次励振素子９を配置し、グランド導体５と２次励振素子の間に複数個の誘電体基板を配置したものを適用してもよい。
以上のように、この実施の形態６によれば、給電点が、励振素子と共通な平面に設置した給電線路で形成されるようにしたので、給電ピンを用いた場合の給電ピン自体からの放射による不要な交差偏波が存在しないという効果が得られる。
【００３０】
実施の形態７．
図１３は実施の形態７による平面アンテナ装置の配置構成を示す正面図である。図において、図１に相当する部分には同一符合を付して示す。ここでは、複数のアンテナ構造体が平面上に配置された状態を示している。この配置は、上記実施の形態１乃至実施の形態６で述べたアンテナ構造体を適用することについて提案するものである。
このように励振素子１を平面上に複数個配置した場合、交差偏波レベルを維持したまま、１素子のときより利得を高くとることができる。図１３では、一方向に励振素子１を配置した例を示しているが、給電点の位置関係を保てば、平面上でどのように配置してもよい。上記実施の形態４および実施の形態５で述べたような、励振素子１の近傍に２次励振素子９を配置し、グランド導体５と２次励振素子１の間に複数個の誘電体基板１０を配置したアンテナ構造体を適用しても同様である。また、上記実施の形態６の給電線路１１，１２で給電するアンテナ構造体を適用しても同様である。
【００３１】
以上のように、実施の形態７によれば、アンテナ構造体、すなわち放射素子を平面上に複数個配置しているので、所定の観測面における所定の覆域内において直交する２偏波双方の交差偏波レベルを同程度低減し、かつ１素子の場合より利得を高くできる効果が得られる。
【００３２】
以上、実施の形態１乃至実施の形態７では、放射素子が矩形である場合について述べてきたが、放射素子は円形等、矩形以外の形状にしてもよく、おおむね同様の効果を奏することができる。
【００３３】
【発明の効果】
以上のように、この発明によれば、グランド導体と、このグランド導体の片面側に配置された励振素子と、グランド導体と励振素子の間に配置された誘電体基板と、励振素子を励振させ直交する偏波を発生させる位置に設けられた２点の給電点とを有するアンテナ構造を備えた平面アンテナ装置において、誘電体基板が、交差偏波の振幅を主偏波の振幅で除した値を交差偏波レベルと定義したとき、給電点の一方から給電した場合の所定の観測面における所定の覆域内の交差偏波レベルの最大値Ｆ［ｄＢ］と誘電体基板の比誘電率ε_ｒとの関係Ｆ（ε_ｒ ）と、給電点の他方から給電した場合の所定の観測面における所定の覆域内の交差偏波レベルの最大値Ｇ［ｄＢ］と誘電体基板の比誘電率ε_ｒ との関係Ｇ（ε_ｒ ）とを等しくする比誘電率ε_ｒ を有するように構成したので、所定の観測面における所定の覆域内において直交する２偏波双方の交差偏波レベルを同程度まで低減できる効果がある。
【図面の簡単な説明】
【図１】この発明の実施の形態１による平面アンテナ装置の構造体を示す２面図である。
【図２】この発明の実施の形態１係る平面アンテナ装置の交差偏波識別度の最大値対基板比誘電率について示す説明図である。
【図３】この発明の実施の形態２による平面アンテナ装置の構造体を示す２面図である。
【図４】この発明の実施の形態２および実施の形態５に係るｘ，ｙ，ｚ座標とｒ，θ，φ座標の関係を示す説明図である。
【図５】この発明の実施の形態２に係る平面アンテナ装置の交差偏波レベルの最大値対基板比誘電率を示す説明図である。
【図６】この発明の実施の形態３に係るｘ，ｙ，ｚ座標とｒ，α，β座標との関係を示す説明図である。
【図７】この発明の実施の形態３に係る平面アンテナ装置の交差偏波レベル対観側面の覆域を示す説明図である。
【図８】この発明の実施の形態３に係る平面アンテナ装置の他の交差偏波レベル対観側面の覆域を示す説明図である。
【図９】この発明の実施の形態３に係る平面アンテナ装置の交差偏波識別度の最大値対基板比誘電率について示す説明図である。
【図１０】この発明の実施の形態４による平面アンテナ装置の構造体を示す２面図である。
【図１１】この発明の実施の形態５による平面アンテナ装置の構造体を示す２面図である。
【図１２】この発明の実施の形態６における平面アンテナ装置の構造体を示す２面図で
【図１３】この発明の実施の形態７による平面アンテナ装置の配置構成を示す正面図である。
【符号の説明】
１ 励振素子、２，３ 給電ピン（給電点）、４，１０ 誘電体基板、５ グランド導体、９ ２次励振素子、１１，１２ 給電線路。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a planar antenna device that shares two orthogonally polarized waves.
[0002]
[Prior art]
In some communications, different channels are formed with orthogonal polarizations, and low cross polarization characteristics are required to avoid interference. When transmission and reception are performed using the dual-polarized antenna, it is necessary to reduce the cross polarization corresponding to each of two orthogonal main polarizations. As a method of realizing the low cross polarization, there is a method of perturbing a feeding point (for example, see Non-Patent Document 1). In addition, by using a circularly polarized microstrip antenna and appropriately selecting the relative permittivity of the dielectric substrate interposed between the circular radiating element and the ground plate, the loss due to the axial ratio can be reduced and the cross polarization characteristics can be improved. There is a method for improvement (for example, see Patent Document 1).
[0003]
[Non-patent document 1]
Toru Takahashi, et al., "Low Cross-Polarization Design Method Using Feed Point Perturbation for Orthogonally-Polarized Patch Antenna," IEICE General Conference, B-1-95, p. 111
[Patent Document 1]
JP-A-63-276302 (FIG. 3)
[0004]
[Problems to be solved by the invention]
A conventional method of perturbing a feed point of an antenna device is a method of reducing cross polarization deterioration due to mutual coupling between orthogonal feed points. Therefore, it is effective on the observation surface including the front direction of the dielectric substrate surface, but is not effective on the observation surface inclined from the front direction of the substrate surface because cross polarization generated from the fundamental mode of the antenna exists. In an antenna that excites two orthogonal linear polarizations instead of an antenna that excites circular polarization, there is a method of improving cross polarization by appropriately selecting the relative permittivity of the dielectric substrate. I didn't.
For the reasons described above, it is difficult for the conventional technology to reduce the cross polarization of both orthogonal two polarizations on the observation plane inclined from the front of the substrate surface for the dual orthogonal polarization antenna. Was.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. By selecting an optimum value of the relative permittivity or the thickness of the dielectric substrate, two orthogonal cross sections within a predetermined coverage area on a predetermined observation surface can be obtained. It is an object of the present invention to provide a planar antenna device that shares two orthogonal polarizations that can reduce cross polarization of both polarizations.
[0006]
[Means for Solving the Problems]
A planar antenna device according to the present invention includes a ground conductor, an excitation element disposed on one side of the ground conductor, a dielectric substrate disposed between the ground conductor and the excitation element, and an excitation element that is orthogonal to the excitation element. In a planar antenna device having an antenna structure having two feeding points provided at positions where polarization is generated, a dielectric substrate crosses a value obtained by dividing the amplitude of the cross polarization by the amplitude of the main polarization. When defined as the polarization level, the maximum value F [dB] of the cross polarization level within a predetermined coverage area on a predetermined observation surface when power is supplied from one of the feeding points and the relative permittivity ε _r of the dielectric substrate The relationship between the relationship F (ε _r ), the maximum value G [dB] of the cross polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from the other of the feeding points, and the relative permittivity ε _r of the dielectric substrate. a dielectric for equalizing the relationship G (epsilon _r) It is that to have a ε _r.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
Embodiment 1 FIG.
FIG. 1 is a two-sided view showing a structure of a planar antenna device according to Embodiment 1 of the present invention. FIG. 1A is a front view, and FIG. In the figure, a rectangular excitation element 1 is arranged on one side of a ground conductor 5, and a dielectric substrate 4 is arranged between the ground conductor 5 and the excitation element 1. Feeding pins (feeding points) 2 and 3 are arranged as feed points through the dielectric substrate 4 to excite the excitation element 1. The power supply pins 2 and 3 are set so as to have a positional relationship in which polarized waves are generated orthogonally. Although not shown, the inner conductor of each coaxial line is connected to the power supply pins 2 and 3 of the excitation element 1 from the ground conductor 5 side, and the outer conductor (covered wire) of each coaxial line is connected to the ground conductor 5. . By exciting the excitation element 1 from two feeding points (feeding pins) 2 and 3, the antenna operates as a dual-polarized dual-use antenna that generates orthogonal polarized waves. For this reason, it is necessary to reduce cross polarization with respect to each main polarization.
[0008]
Consider the cross-polarization level in a predetermined coverage on a predetermined observation surface. Here, the cross polarization level is defined as a value obtained by dividing the amplitude of the cross polarization by the amplitude of the main polarization. In general, when the relative permittivity ε _r of the dielectric substrate 4 is changed, the change in the maximum value of the cross polarization level within a predetermined coverage area is determined when the power is supplied from one power supply point 2 and when the other power is supplied. This is different from when power is supplied from point 3. FIG. 2 is an explanatory diagram showing the maximum value of the cross polarization discrimination degree versus the relative permittivity of the substrate in each case. F (ε _r ) is the difference between the maximum value F [dB] of the cross polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from one of the feeding points 2 and the relative permittivity ε _r of the dielectric substrate. Show the relationship. G (ε _r ) is the maximum value G [dB] of the cross polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from the other power supply point 3 and the relative permittivity ε of the dielectric substrate. _This shows the relationship with _r . In FIG. 2, if the substrate dielectric constant ε _r is set to a value such that the above-mentioned F (ε _r ) and the above-mentioned G (ε _r ) are equal, the cross polarization levels of both orthogonal two polarizations can be reduced to the same level. You can see that.
[0009]
As described above, according to the first embodiment, F (ε _r ) and G (ε _r ) are obtained by performing numerical calculation or measurement within a predetermined coverage area on a predetermined observation surface, and obtaining the F (ε _r ). By obtaining the relative permittivity ε _r of the dielectric substrate 4 that makes ε _r ) and G (ε _r ) equal, the cross polarization levels of both orthogonal two polarizations within the predetermined coverage area on the predetermined observation surface can be made the same. The effect that can be reduced to the extent is obtained.
[0010]
Embodiment 2 FIG.
Here, the case where the ground conductor 5 and the dielectric substrate 4 are finite in the planar antenna device of FIG. 1 will be described. 3A and 3B are two views showing a structure of the planar antenna device according to the second embodiment. FIG. 3A is a front view, and FIG. 3B is a cross-sectional view along AA. In the figure, portions corresponding to those in FIG. 1 are denoted by the same reference numerals. Here, the excitation element 1 is defined as a rectangle. x, y, and z are rectangular coordinates, and the plane of the ground conductor 5 is a yz plane, and the origin is located on the plane of the ground conductor 5. Similarly, the origin of the r, θ, φ coordinates is used. “a” and “b” are the lengths of one side of the rectangular excitation element 1 respectively. The center of the rectangular excitation element 1 is set on the x-axis, and the sides “a” and “b” of the rectangle are set to be parallel to the y-axis or the z-axis. Have been. Feed points 2 and 3 are located on the y and z axes, respectively. FIG. 4 shows the relationship between the x, y, z coordinates and the r, θ, φ coordinates. θ is the angle from the z-axis, and φ is the angle from the x-axis in the xy plane.
[0011]
The main polarization excited when power is supplied to the feeding point 2 is defined as H polarization, and the main polarization excited when feeding the power to the feeding point 3 is defined as V polarization. That is, assuming that the θ component of the electric field is E _θ and the φ component is E _φ , the main polarization at the time of H polarization excitation is E _φ , and the main polarization at the time of V polarization excitation is E _θ .
FIG. 5 shows the maximum value of the cross polarization level and the dielectric constant in the coverage φ of the observation plane φ = −40 ° to 40 ° during the H polarization excitation and the V polarization excitation, which were obtained by numerical calculation. It illustrates the relationship between the relative dielectric constant epsilon _r of the body board 4. This means that the ground conductor 5 and the substrate 4 are finite, the excitation element 1 is excited at the resonance frequency of the antenna, the feeding point 3 is dummy-terminated when feeding the feeding point 2, and the feeding is performed when feeding the feeding point 3. The result of a numerical calculation performed when the point 2 is dummy terminated is shown. As shown in FIG. 4, r, θ, φ coordinates are defined, θ = 81 °, the cross polarization level of the observation plane is calculated, and the maximum value of the cross polarization level in the coverage area φ = −40 ° to 40 ° is calculated. and in which to determine the relationship between the specific dielectric constant epsilon _r of the dielectric substrate.
[0012]
In FIG. 5, in order to reduce the cross polarization level of both orthogonal two polarizations to the same level, the substrate dielectric constant ε _r is changed by θ = 81 ° of the observation plane during the H polarization excitation and the V polarization excitation. It can be seen that ε _{r at} which the maximum value of the cross polarization level within the coverage area φ = −40 ° to 40 ° becomes equal is sufficient. When this ε _r is obtained, it is about 1.65.
[0013]
As described above, according to the second embodiment, when the ground conductor 5 and the substrate 4 are finite, the numerical observation is used to obtain a predetermined observation surface at the time of the H polarization excitation and the V polarization excitation. In the predetermined coverage area in the above, the relative permittivity ε _r of the dielectric substrate at which the maximum value of the cross polarization level of both orthogonal two polarizations is equal is obtained, so that within the predetermined coverage area on the predetermined observation surface The effect of reducing the cross polarization level of both orthogonal two polarizations to the same level can be obtained.
[0014]
Embodiment 3 FIG.
In the third embodiment, when the ground conductor 5 and the dielectric substrate 4 in FIG. 3 are infinite in the y and z directions, the effect of the first embodiment will be clarified from a theoretical formula. FIG. 6 is an explanatory diagram showing the relationship between the x, y, z coordinates and the r, α, β coordinates. FIG. 7 shows the cross polarization level at the θ = 81 ° observation plane obtained from the cavity model at the time of the H polarization excitation, and FIG. 8 shows the intersection at the θ = 81 ° observation plane obtained at the V polarization excitation. The polarization level. FIG. 9 shows the maximum value of the cross polarization level and the relative permittivity of the dielectric substrate 4 within the coverage area φ of the observation surface φ = −40 ° to 40 ° during the H polarization excitation and the V polarization excitation. This shows the relationship with ε _r .
[0015]
Ideally, no cross-polarization occurs in the θ = 90 ° plane and φ = 0 ° plane. However, cross-polarization occurs on the observation plane where θ inclined from the front direction of the substrate is constant (θ ≠ 90 °) or φ is constant (φ ≠ 0 °). This cross-polarization is to occur from the relationship of the coordinate system in the main mode (TM ₁₀ mode) for radiating the original main polarization. It is assumed that the ground conductor 5 and the dielectric substrate 4 are infinite in the y and z directions. The main mode serving TM ₁₀ mode radiation field at resonance of the antenna of FIG. 3, r as shown in FIG. 6, alpha, when defining the beta coordinates, the cavity model, E the alpha component of the electric field _alpha, the beta component E _beta and then, the dielectric constant of the dielectric substrate 4 as epsilon _r,
(Equation 6)

It becomes. here,
(Equation 7)

Where k ₀ is the wave number of free space and V ₀ is a constant.
[0016]
With respect to Expressions (1) and (2), coordinate conversion from r, α, β coordinates to r, θ, φ coordinates is performed to obtain θ components E _θ and φ components E _φ of the electric field. Then, when the H polarization excitation, the main polarization is E _phi, since cross-polarization becomes E _theta, cross-polarization level in the case of H polarization excitation,
(Equation 8)

It becomes. When the V polarization is excited, the main polarization is E _θ and the cross polarization is E _φ. Therefore, the cross polarization level when the V polarization is excited is
(Equation 9)

It becomes. From equation (4), it can be seen that the as the cross-polarization level relative dielectric constant epsilon _r of the dielectric substrate is increased becomes smaller when the H-polarized wave excitation. Conversely, from equation (5), it can be seen that the cross polarization level increases as the relative permittivity ε _{r of the} dielectric substrate increases during V polarization excitation.
[0017]
For example, the formula (4), (5) by substituting theta = 81 °, when determining the dependence on the relative dielectric constant epsilon _r of the cross-polarization level of the dielectric substrate at theta = 81 ° observation surface, respectively view 7, as shown in FIG. Further, for example, when the maximum value of the cross polarization level within the coverage area φ = −40 ° to 40 ° is obtained, the equations (4) and (5) are obtained when φ = ± 40 ° from FIGS. The relationship between the maximum value of the cross polarization level and the relative permittivity ε _r of the dielectric substrate in the coverage area φ = −40 ° to 40 ° during the H polarization excitation and the V polarization excitation is shown in FIG. It looks like 9.
[0018]
In FIG. 9, in order to reduce the cross polarization level of both orthogonal two polarizations to the same level, the substrate dielectric constant ε _{r is set} to θ = 81 ° of the observation plane during the H polarization excitation and the V polarization excitation. It can be seen that it is sufficient to set ε _{r so} that the maximum value of the cross polarization level within the coverage area φ = −40 ° to 40 ° becomes equal. When ε _r is obtained, ε _r = 1.76.
[0019]
As described above, according to the third embodiment, when the ground conductor 5 and the dielectric substrate 4 are infinite in the y and z directions, the equations (4) and (5) show that At the time of V-polarized excitation, the cross-polarization level at a predetermined observation plane where θ is constant or φ is constant is calculated. At this time, the maximum values of Equations (4) and (5) are equal within a predetermined coverage area. Since the relative permittivity ε _r of the dielectric substrate 4 is determined as described above, the cross polarization level of both orthogonal two polarizations within a predetermined coverage on a predetermined observation surface where θ is constant or φ is constant. Can be reduced to the same extent.
[0020]
Embodiment 4 FIG.
10A and 10B are two views showing a structure of a planar antenna device according to a fourth embodiment of the present invention. FIG. 10A is a front view, and FIG. 10B is a cross-sectional view. In the figure, portions corresponding to those in FIG. 1 are denoted by the same reference numerals. In this case, the secondary excitation element 9 is arranged near the excitation element 1 and is configured to be indirectly excited by the electromagnetic wave from the excitation element 1. A plurality of dielectric substrates 10 are arranged between the ground conductor 5 and the excitation element 1 and between the excitation element 1 and the secondary excitation element 9 (N> 1). Part of the dielectric substrate 10 may be formed of an air layer. Here, among the N dielectric substrates 10, the relative dielectric constant of the n-th dielectric substrate is ε _rn , and the thickness is t _n .
[0021]
Consider the cross-polarization level within a given coverage area on a given observation surface. By performing numerical calculation or measurement, the maximum value F [dB] of the cross polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from one power supply point 2 and the relative dielectric constant of the n-th dielectric substrate The relationship F (ε _rn ) with the rate ε _rn , the maximum value G [dB] of the cross polarization level within a predetermined coverage area on a predetermined observation surface when power is supplied from the other feeding point 3, and the n-th dielectric The relationship G (ε _rn ) with the relative permittivity ε _rn of the body substrate is obtained.
[0022]
Generally, the directions of increase and decrease of F (ε _rn ) and G (ε _rn ) with the increase of the relative dielectric constant ε _rn of the n-th dielectric substrate are opposite. Therefore, as in the first embodiment, if the relative permittivity ε _rn of the n-th dielectric substrate is set so that the F (ε _rn ) and the G (ε _rn ) are equal, two orthogonal polarization The cross polarization level of both waves can be reduced to the same extent.
[0023]
Similarly, by performing a numerical calculation or measurement, the maximum value F [dB] of the cross polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from one of the power supply points 2 and the n-th dielectric substrate the relation between the thickness t _n F (t _n), the maximum value of the predetermined covering region of the cross-polarization level in the predetermined observation plane in the case of feeding from the other feeding point 3 G [dB] and n-th The relationship G (t _n ) with the thickness t _n of the dielectric substrate is obtained.
Generally, the directions of increase and decrease of F (t _n ) and G (t _n ) with the increase of the thickness t _n of the n-th dielectric substrate are opposite. Therefore, F (t _n ) and G (t _n ) can be made equal by selecting the thickness t _n of the n-th dielectric substrate.
[0024]
As described above, according to the fourth embodiment, the relative permittivity ε _rn of the n-th dielectric substrate at which the above F (ε _rn ) and the above G (ε _rn ) are equal is set. The effect of reducing the cross polarization level of both the two polarizations to the same level can be obtained. On the other hand, even if the thickness t _n of the n-th dielectric substrate is set so that F (t _n ) and G (t _n ) are equal, the cross polarization of both orthogonal two polarizations is similarly determined. The effect of reducing the level to the same level can be obtained.
[0025]
Embodiment 5 FIG.
The fifth embodiment clarifies the effect of the fourth embodiment from a theoretical formula when the ground conductor 5 and the dielectric substrate 4 in FIG. 10 are infinite in the y and z directions. 11 is a two-sided view showing a structure of a planar antenna device according to a fifth embodiment of the present invention. FIG. 11 (a) is a front view, and FIG. 11 (b) is a cross-sectional view along AA. In the figure, parts corresponding to those in FIG. 10 are denoted by the same reference numerals. The excitation element 1 and the secondary excitation element 9 are rectangular. The polarization excited when the power is supplied to the feeding point 2 is defined as H polarization, and the polarization excited when the power is fed to the feeding point 3 is defined as V polarization. Further, the relative dielectric constant of the n-th dielectric substrate among the N dielectric substrates 10 is ε _rn , and the thickness is t _n . The relationship between the x, y, z coordinates and the r, θ, φ coordinates in FIG. 4 is used.
[0026]
In FIG. 11, since the secondary excitation element 9 mainly contributes to radiation, the radiation characteristics of the secondary excitation element 9 may be considered. The equivalent relative permittivity ε _ref seen from the secondary excitation element 9 is:
(Equation 10)

Can be defined as Therefore, by replacing ε _r in the cross polarization level equations (4) and (5) obtained from the cavity model in the third embodiment with ε _ref in equation (6), the cross polarization level of the planar antenna in FIG. Wave level can be determined. The cross polarization level obtained when the H polarization is excited, that is, the cross polarization obtained from the cross polarization amplitude | E _θ | and the main polarization amplitude | E _φ | when power is supplied from a feed point provided on the y-axis. The wave level is
[Equation 11]

The cross polarization level when the V polarization is excited, that is, the crossing by the cross polarization amplitude | E _φ | and the main polarization amplitude | E _θ | when the power is supplied from the feeding point provided on the z-axis. The polarization level is
(Equation 12)

It becomes.
[0027]
From the equation (7), it can be seen that the cross polarization level decreases as the equivalent relative permittivity ε _ref increases during the H polarization excitation. Conversely, from equation (8), it can be seen that the cross polarization level increases as the equivalent relative permittivity ε _ref increases during V polarization excitation. Therefore, there is an equivalent relative permittivity ε _{ref at} which Equation (7) and Equation (8) are equal.
[0028]
As described above, according to the fifth embodiment, when the ground conductor 5 and the dielectric substrate 4 are infinite, within a predetermined coverage on a predetermined observation surface where θ is constant or φ is constant, the expression (7) ) And Equation (8) are determined to obtain the equivalent relative permittivity ε _ref , so that the effect of reducing the cross polarization level of both orthogonal two polarizations to the same level can be obtained.
[0029]
Embodiment 6 FIG.
In the sixth embodiment, the same effect as in the first to fifth embodiments will be described when the excitation element is excited using a feed line instead of a feed pin. FIGS. 12A and 12B are two views showing a structure of the planar antenna device according to the sixth embodiment. FIG. 12A is a front view, and FIG. In the figure, portions corresponding to those in FIG. 1 are denoted by the same reference numerals. Here, instead of the power supply pins, the power supply lines 11 and 12 are provided on the same plane as the excitation element 1.
Excitation element 1 is fed and excited by two feeder lines 11 and 12 to generate orthogonal polarized waves, and operates as a dual-polarized dual-use antenna, as described in the first to third embodiments. I do. As the antenna structure, as shown in FIG. 10 of the fourth embodiment, a secondary excitation element 9 is arranged near the excitation element 1 and a plurality of dielectric elements are provided between the ground conductor 5 and the secondary excitation element. A body substrate may be used.
As described above, according to the sixth embodiment, the power supply point is formed by the power supply line provided on the same plane as the excitation element. An effect that unnecessary cross polarization due to radiation does not exist is obtained.
[0030]
Embodiment 7 FIG.
FIG. 13 is a front view showing an arrangement configuration of the planar antenna device according to the seventh embodiment. In the figure, portions corresponding to those in FIG. 1 are denoted by the same reference numerals. Here, a state is shown in which a plurality of antenna structures are arranged on a plane. This arrangement proposes to apply the antenna structure described in the first to sixth embodiments.
When a plurality of the excitation elements 1 are arranged on a plane as described above, it is possible to increase the gain while maintaining the cross polarization level as compared with the case of one element. FIG. 13 shows an example in which the excitation elements 1 are arranged in one direction, but any arrangement may be made on a plane as long as the positional relationship between the feeding points is maintained. As described in the fourth and fifth embodiments, the secondary excitation element 9 is disposed in the vicinity of the excitation element 1, and the plurality of dielectric substrates 10 are provided between the ground conductor 5 and the secondary excitation element 1. The same applies to the case where an antenna structure in which is disposed is applied. The same applies to the case where the antenna structure for feeding power through the feed lines 11 and 12 of the sixth embodiment is applied.
[0031]
As described above, according to Embodiment 7, since a plurality of antenna structures, that is, a plurality of radiating elements are arranged on a plane, the intersection of both orthogonally polarized waves within a predetermined coverage area on a predetermined observation surface. The effect is obtained that the polarization level can be reduced to the same extent and the gain can be higher than in the case of one element.
[0032]
As described above, in the first to seventh embodiments, the case where the radiating element is rectangular has been described. However, the radiating element may have a shape other than a rectangle, such as a circle, and substantially the same effect can be obtained. .
[0033]
【The invention's effect】
As described above, according to the present invention, the ground conductor, the excitation element disposed on one side of the ground conductor, the dielectric substrate disposed between the ground conductor and the excitation element, and the excitation element are excited. In a planar antenna device having an antenna structure having two feed points provided at positions where orthogonal polarizations are generated, the dielectric substrate has a value obtained by dividing the amplitude of the cross polarization by the amplitude of the main polarization. Is defined as the cross polarization level, the maximum value F [dB] of the cross polarization level within a predetermined coverage area on a predetermined observation surface when power is supplied from one of the feeding points, and the relative permittivity ε _{r of the} dielectric substrate F (ε _r ), the maximum value G [dB] of the cross-polarization level within a predetermined coverage area on a predetermined observation surface when power is supplied from the other feeding point, and the relative permittivity ε _{r of the} dielectric substrate Relative dielectric constant ε to make the relationship G (ε _r ) _Since it is configured to have _r , there is an effect that the cross polarization level of both orthogonal two polarizations can be reduced to the same degree within a predetermined coverage area on a predetermined observation surface.
[Brief description of the drawings]
FIG. 1 is a two-sided view showing a structure of a planar antenna device according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing the maximum value of the cross polarization discrimination degree versus the relative permittivity of the substrate in the planar antenna device according to the first embodiment of the present invention;
FIG. 3 is a two-sided view showing a structure of a planar antenna device according to a second embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a relationship between x, y, z coordinates and r, θ, φ coordinates according to Embodiments 2 and 5 of the present invention.
FIG. 5 is an explanatory diagram showing the maximum value of the cross polarization level versus the relative permittivity of the substrate in the planar antenna device according to Embodiment 2 of the present invention;
FIG. 6 is an explanatory diagram showing a relationship between x, y, z coordinates and r, α, β coordinates according to Embodiment 3 of the present invention.
FIG. 7 is an explanatory diagram showing a cross polarization level and a coverage area on a view side surface of the planar antenna device according to Embodiment 3 of the present invention.
FIG. 8 is an explanatory diagram showing another cross polarization level and a coverage area of a view side surface of the planar antenna device according to the third embodiment of the present invention.
FIG. 9 is an explanatory diagram showing the maximum value of cross polarization discrimination versus the relative permittivity of a substrate in the planar antenna device according to Embodiment 3 of the present invention.
FIG. 10 is a two-sided view showing a structure of a planar antenna device according to a fourth embodiment of the present invention.
FIG. 11 is a two-view drawing showing a structure of a planar antenna device according to a fifth embodiment of the present invention.
FIG. 12 is a two-sided view showing a structure of a planar antenna device according to a sixth embodiment of the present invention. FIG. 13 is a front view showing an arrangement configuration of the planar antenna device according to a seventh embodiment of the present invention.
[Explanation of symbols]
1 Exciting element, 2, 3 Feeding pin (feeding point), 4, 10 Dielectric substrate, 5 Ground conductor, 9 Secondary exciting element, 11, 12 Feeding line.

Claims (7)

A ground conductor, an excitation element disposed on one side of the ground conductor, a dielectric substrate disposed between the ground conductor and the excitation element, and a position for exciting the excitation element and generating orthogonal polarization. A planar antenna device provided with an antenna structure having two feeding points provided in
The dielectric substrate,
When the value obtained by dividing the amplitude of the cross polarization by the amplitude of the main polarization is defined as the cross polarization level,
The relation F (ε _r ) between the maximum value F [dB] of the cross polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from one of the feeding points and the relative permittivity ε _r of the dielectric substrate; ,
The relationship G (ε _r ) between the maximum value G [dB] of the cross polarization level in the predetermined coverage area on the predetermined observation surface and the relative permittivity ε _r of the dielectric substrate when power is supplied from the other of the power supply points. ) Having the relative permittivity ε _r that is equal to The excitation element is rectangular,
Set x, y, z orthogonal coordinates and θ, φ coordinates that place the origin on the surface of the ground conductor,
The plane of the ground conductor is a yz plane, and the sides of the rectangle are set in parallel with the y-axis or z-axis with the x-axis as the center of the rectangle, and the feeding point is set on the y-z axis. , Respectively,
Let θ be the angle from the z-axis, φ be the angle from the x-axis in the xy plane, let the θ component of the electric field be E _θ, and let the φ component of the electric field be E _φ
The cross polarization level obtained from the cross polarization amplitude | E _θ | and the main polarization amplitude | E _φ | when power is supplied from the power supply point provided on the y-axis.

age,
The cross polarization level based on the cross polarization amplitude | E _φ | and the main polarization amplitude | E _θ | when power is supplied from the power supply point provided on the z-axis.

age,
2. The plane according to claim 1, wherein the dielectric has a relative permittivity ε _{r at} which the maximum value of the two equations becomes equal within a predetermined coverage area of a predetermined observation surface where θ is constant or φ is constant. Antenna device. A ground conductor,
An excitation element arranged on one side of the ground conductor,
A secondary excitation element that is arranged near the ground element on the opposite side of the excitation element and is indirectly excited by electromagnetic waves from the excitation element;
N (N> 1) dielectric substrates disposed between the ground conductor and the excitation element and between the excitation element and the secondary excitation element, respectively;
An antenna structure having two feeding points provided at positions where the excitation element is excited to generate orthogonal polarization,
The n-th (N ≧ n ≧ 1) -th dielectric substance is
When the value obtained by dividing the amplitude of the cross polarization by the amplitude of the main polarization is defined as the cross polarization level,
The relation F (ε _rn ) between the maximum value F [dB] of the cross polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from one of the feeding points and the relative permittivity ε _rn of the dielectric substrate; ,
The relation G (ε _rn ) between the maximum value G [dB] of the cross polarization level in the predetermined coverage area on the predetermined observation surface and the substrate relative permittivity ε _rn when the power is fed from the other of the feeding points is A planar antenna device having a relative permittivity ε _rn that is equal. A ground conductor,
An excitation element arranged on one side of the ground conductor,
A secondary excitation element that is arranged near the ground element on the opposite side of the excitation element and is indirectly excited by electromagnetic waves from the excitation element;
N (N> 1) dielectric substrates disposed between the ground conductor and the excitation element and between the excitation element and the secondary excitation element, respectively;
An antenna structure having two feeding points provided at positions where the excitation element is excited to generate orthogonal polarization,
The n-th dielectric substrate is
A relation F (t _n ) between the maximum value F [dB] of the cross-polarization level in a predetermined coverage area on a predetermined observation surface when power is supplied from one of the feeding points and the thickness t _n of the dielectric substrate;
The relation G (t _n ) between the maximum value G [dB] of the cross polarization level in the predetermined coverage area on the predetermined observation surface and the thickness t _n of the dielectric substrate when power is supplied from the other of the feeding points. A planar antenna device having a thickness t _n that makes The excitation element and the secondary excitation element are each rectangular,
Set x, y, z orthogonal coordinates and θ, φ coordinates that place the origin on the surface of the ground conductor,
The surface of the ground conductor is a yz plane, and the sides of each rectangle are placed in parallel with the y-axis or the z-axis with the x-axis as the center of each rectangle,
When the thickness of the n-th dielectric substrate is t _n , the equivalent relative permittivity ε _ref seen from the secondary excitation element is

Is defined as
Let θ be the angle from the z-axis, φ be the angle from the x-axis in the xy plane, let the θ component of the electric field be E _θ, and let the φ component of the electric field be E _φ
The cross polarization level obtained from the cross polarization amplitude | E _θ | and the main polarization amplitude | E _φ | when power is supplied from the power supply point provided on the y-axis.

age,
The cross polarization level based on the cross polarization amplitude | E _φ | and the main polarization amplitude | E _θ | when power is supplied from the power supply point provided on the z-axis.

age,
4. A method according to claim 3 or claim 3, wherein an equivalent relative permittivity ε _ref is such that the maximum values of the above equations become equal within a predetermined coverage area of a predetermined observation plane where θ is constant or φ is constant. Item 6. The planar antenna device according to item 4. The planar antenna device according to any one of claims 1 to 5, wherein the feed point is formed by a feed line provided on a common plane with the excitation element. The planar antenna device according to any one of claims 1 to 6, wherein a plurality of antenna structures are arranged on a plane.

Images