JP5493132B2 - Radio wave absorber and design method thereof - Google Patents
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Description
本発明は、電波反射層と電波吸収層を有する層構造の電波吸収体及びその設計方法に関する。 The present invention relates to a radio wave absorber having a layer structure having a radio wave reflection layer and a radio wave absorption layer, and a design method thereof.
電波吸収体は、電波暗室内での電波散乱抑制、各種構造体によるレーダ偽像防止、レーダ反射断面積低減、ＥＴＣの誤作動防止、電波機器の人体への影響を計測するための人体ファントム用部材への使用等を目的として近年広く産業界でその需要が増大している。 The radio wave absorber is for human body phantoms to suppress radio wave scattering in an anechoic chamber, prevent radar false images with various structures, reduce radar cross section, prevent ETC malfunction, and measure the effects of radio wave equipment on the human body. In recent years, the demand has been increasing widely in the industry for the purpose of use for members.
層構造を有する一般的な電波吸収体は、図１（Ａ）に示すように、入射電波の透過を阻止し反射するための電波反射層１、電波のエネルギーを熱エネルギーに変換する機能を有する電波損失材をフィラーとしてバインダーに混入した電波吸収層２、入力インピーダンスの整合を行う電波整合層３、及び外部環境から各層を保護するための電波表面層４から構成される。 A general radio wave absorber having a layer structure has a function of converting a radio wave energy into heat energy, as shown in FIG. 1A, a radio wave reflection layer 1 for blocking and reflecting incident radio waves. It is composed of a radio wave absorbing layer 2 mixed with a binder using a radio wave loss material, a radio wave matching layer 3 for matching input impedance, and a radio wave surface layer 4 for protecting each layer from the external environment.
電波吸収層及び電波整合層は複数あってもよい。また、電波表面層については、電波吸収層もしくは電波整合層で代用してもよい。さらに、電波整合層を電波吸収層で代用してもよい。 There may be a plurality of radio wave absorption layers and radio wave matching layers. The radio wave surface layer may be substituted with a radio wave absorption layer or a radio wave matching layer. Further, the radio wave matching layer may be substituted with a radio wave absorption layer.
電波吸収体による電波の吸収メカニズムの説明としては、電波を波動として扱う場合と幾何光学的なレイとして扱う場合があるがいずれも結果は同じである。図４を用いて幾何光学的に説明すると以下のようになる。 The explanation of the absorption mechanism of the radio wave by the radio wave absorber includes the case where the radio wave is handled as a wave and the case where it is handled as a geometrical optical ray. The geometric optical description with reference to FIG. 4 is as follows.
入射電波であるレイ６は電波吸収体表面でフレネルの法則に従い、一部がレイ７として反射され残りがレイ８として透過する。透過したレイ８は各層の界面５で反射及び透過を繰り返し、途中の電波吸収層２では吸収減衰し、電波反射層１まで達すると全反射される。 Ray 6 that is an incident radio wave is partially reflected as ray 7 and the rest is transmitted as ray 8 according to Fresnel's law on the surface of the wave absorber. The transmitted ray 8 repeats reflection and transmission at the interface 5 of each layer, is absorbed and attenuated in the radio wave absorption layer 2 on the way, and is totally reflected when reaching the radio wave reflection layer 1.
全反射されたレイ９は電波吸収体表面に達するまで前記透過レイ８と同様の過程を経て吸収体表面に達するとその一部が透過し、残りが再反射される。この一連のレイ群の伝搬過程により、全体として電波が吸収される。 The totally reflected ray 9 passes through the same process as that of the transmission ray 8 until reaching the surface of the radio wave absorber. Radio waves are absorbed as a whole by this series of ray group propagation processes.
一方、電波を波動として扱う場合は分布定数回路でモデル化することにより、その電波吸収量Ｓ[dB]は、入射面での電波の振幅反射率Γを用いて下記式(1)及び(2)で求められる。
ここで、Ｚinは入射面から電波吸収体内部を見たときの規格化入力インピーダンスであり、光速度、入射電波の周波数、電波吸収体表面での電波の入射角、各層の厚み、及び各層の電気定数の複素関数である。従って、振幅反射率Γも振幅と位相を有する複素関数となる。 Here, Z in is the normalized input impedance when the inside of the radio wave absorber is viewed from the incident surface, and the speed of light, the frequency of the incident radio wave, the incident angle of the radio wave on the surface of the radio wave absorber, the thickness of each layer, and each layer Is a complex function of the electric constant of Therefore, the amplitude reflectance Γ is also a complex function having an amplitude and a phase.
電波吸収量を大きくするためには、電波吸収層を厚くするとともに損失材の量を多くして電波の熱への変換効率を高めることが通常考えられる。 In order to increase the amount of radio wave absorption, it is usually considered to increase the radio wave heat conversion efficiency by increasing the thickness of the radio wave absorption layer and increasing the amount of loss material.
しかし、単純に電波吸収層を厚くし損失材の量を多くするだけでは、電波吸収体と空気のインピーダンスの不一致により電波吸収体表面での電波の反射量が増大し、吸収性能は良くならない。 However, simply increasing the thickness of the radio wave absorption layer and increasing the amount of loss material increases the amount of radio wave reflection on the surface of the radio wave absorber due to the mismatch between the impedance of the radio wave absorber and the air, and does not improve the absorption performance.
従来インピーダンスのマッチングをよくするために、
１．電波吸収体表面から電波反射層に向かって誘電率や透磁率である電気定数を連続的に変化させる、
２．多層化する、
３．層間界面に二次元的な構造物を挟む、
４．界面に周期的凹凸をつける、
等の解決手法が提案されている。各手法の代表的な文献を特許文献１乃至３に提示する。
Conventionally, to improve impedance matching,
1. Continuously changing the electrical constant, which is the dielectric constant and permeability, from the surface of the radio wave absorber to the radio wave reflection layer,
2. Multilayered,
3. Sandwich a two-dimensional structure at the interface between layers,
4). Add periodic irregularities to the interface,
Such a solution method has been proposed. Representative documents of each method are presented in Patent Documents 1 to 3.
電波吸収体の各層の厚みが場所的に均一であれば、前記分布定数回路を用いてモデル化できるため、従来型の電波吸収体では各層の厚みが均一という条件下で最適値を求めていた。 If the thickness of each layer of the radio wave absorber is uniform in location, it can be modeled using the distributed constant circuit. Therefore, in the conventional radio wave absorber, the optimum value was obtained under the condition that the thickness of each layer was uniform. .
一方、電波吸収体各層界面もしくは電波吸収体表面（空気と電波吸収体との界面）に導体パッチ、導体ホール、凹凸などを配列することによる、電波吸収特性の改善策が近年提案されているが、いずれも周期的な構造に限定されていた。このように従来の電波吸収体の実現にあたっては、上記条件の範囲内で設計していたため、電波吸収特性向上も限定される問題があった。 On the other hand, measures have been proposed in recent years to improve radio wave absorption characteristics by arranging conductor patches, conductor holes, irregularities, etc. on the interface of each wave absorber or on the surface of the wave absorber (the interface between air and the wave absorber). Both were limited to periodic structures. As described above, since the conventional radio wave absorber is designed within the range of the above-described conditions, there is a problem that improvement of radio wave absorption characteristics is limited.
本発明は、上記の点に鑑み、一もしくは複数の界面から電波反射層を見込んだ入力インピーダンスを界面上で非周期的に変化させることにより、電波吸収性能を向上させた新しいタイプの電波吸収体及びその設計方法を実現することを目的としている。 In view of the above points, the present invention is a new type of radio wave absorber that has improved radio wave absorption performance by aperiodically changing the input impedance that expects a radio wave reflection layer from one or more interfaces on the interface. And its design method.
本発明のある態様は、電波吸収体である。この電波吸収体は、
電波反射層と電波吸収層と電波整合層と電波表面層とからなる電波吸収体、もしくは電波反射層と電波吸収層と電波表面層とからなる電波吸収体、もしくは電波反射層と電波吸収層とからなる電波吸収体であって、
セル構造を有し、電波吸収体を構成する各層のうち少なくとも一つの層の誘電率の実部、透磁率の実部、及び透磁率の虚部の少なくとも一つが場所的に非周期的かつセルごとに離散的に変化し、その変化量が平均と分散を有する確率分布に従うことを特徴とする。
One embodiment of the present invention is a radio wave absorber. This radio wave absorber
A radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, a radio wave matching layer, and a radio wave surface layer, or a radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, and a radio wave surface layer, or a radio wave reflection layer and a radio wave absorption layer An electromagnetic wave absorber made of
At least one of the real part of the dielectric constant, the real part of the magnetic permeability, and the imaginary part of the magnetic permeability of the at least one of the layers constituting the electromagnetic wave absorber having a cell structure is locally aperiodic and a cell It is characterized in that it changes discretely every time and the amount of change follows a probability distribution having mean and variance.
前記平均と分散を有する確率分布が離散一様分布、二項分布、ポアソン分布、負の二項分布、ベルヌーイ分布、超幾何分布、多項分布、もしくはジップ分布のいずれか一つであるとよい。 The probability distribution having the mean and variance may be any one of discrete uniform distribution, binomial distribution, Poisson distribution, negative binomial distribution, Bernoulli distribution, hypergeometric distribution, multinomial distribution, or zip distribution.
前記セル構造において、セル形状が多角形であるとよい。 In the cell structure, the cell shape may be a polygon.
前記セル構造において、前記電波表面層が複数種の塗装であるとよい。 In the cell structure, the radio wave surface layer may be a plurality of types of coating.
電波反射層と電波吸収層と電波整合層と電波表面層とからなる電波吸収体、もしくは電波反射層と電波吸収層と電波表面層とからなる電波吸収体、もしくは電波反射層と電波吸収層とからなる電波吸収体であって界面から前記電波吸収層側を見込む入力インピーダンスが場所的に均一である基準電波吸収体と比較して、所定周波数範囲及び所定入射角度範囲における電波吸収量が大きいとよい。 A radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, a radio wave matching layer, and a radio wave surface layer, or a radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, and a radio wave surface layer, or a radio wave reflection layer and a radio wave absorption layer Compared with a reference wave absorber in which the input impedance looking into the wave absorption layer side from the interface is uniform in place, the amount of radio wave absorption in a predetermined frequency range and a predetermined incident angle range is large. Good.
本発明の別の態様は、電波吸収体の設計方法である。この方法は、
電波反射層と電波吸収層と電波整合層と電波表面層とからなる電波吸収体、もしくは電波反射層と電波吸収層と電波表面層とからなる電波吸収体、もしくは電波反射層と電波吸収層とからなる電波吸収体であって界面から前記電波吸収層側を見込む入力インピーダンスが場所的に均一である基準電波吸収体を仮想的にセル構造に分割し、前記基準電波吸収体を構成する各層のうち少なくとも一つの層の誘電率の実部、透磁率の実部、及び透磁率の虚部の少なくとも一つをセルごとに変化させたものを設計値とする電波吸収体の設計方法であって、
平均と分散を有する確率分布に従う確率変数をセルごとに発生させて、その発生した確率変数に基づいて前記誘電率の実部、前記透磁率の実部、及び前記透磁率の虚部の少なくとも一つの変化量をセルごとに決定することを特徴とする。
Another aspect of the present invention is a method for designing a radio wave absorber. This method
A radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, a radio wave matching layer, and a radio wave surface layer, or a radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, and a radio wave surface layer, or a radio wave reflection layer and a radio wave absorption layer A reference wave absorber having an input impedance that is uniform from the interface and having a uniform input impedance from the interface, is virtually divided into cell structures, and each of the layers constituting the reference wave absorber is divided into cell structures. A method of designing a radio wave absorber, wherein a design value is obtained by changing at least one of the real part of the dielectric constant, the real part of the magnetic permeability, and the imaginary part of the magnetic permeability of each layer among the cells. ,
A random variable according to a probability distribution having a mean and variance is generated for each cell, and at least one of the real part of the dielectric constant, the real part of the magnetic permeability, and the imaginary part of the magnetic permeability is based on the generated random variable. One change amount is determined for each cell.
前記平均と分散を有する確率分布が、離散一様分布、二項分布、ポアソン分布、負の二項分布、ベルヌーイ分布、超幾何分布、多項分布、もしくはジップ分布のいずれか一つであるとよい。 The probability distribution having the mean and variance may be any one of discrete uniform distribution, binomial distribution, Poisson distribution, negative binomial distribution, Bernoulli distribution, hypergeometric distribution, multinomial distribution, or zip distribution. .
なお、以上の構成要素の任意の組合せ、本発明の表現を方法やシステムなどの間で変換したものもまた、本発明の態様として有効である。 It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.
本発明によれば、電波吸収体の局所的な電気定数を設計パラメータに取り込むことにより、従来設計できなかった局所入力インピーダンスの非周期変化が実現可能となり、これにより従来よりも高性能の電波吸収体及びその設計方法を実現できる。 According to the present invention, by incorporating a local number electrical constant of the wave absorber to the design parameters, aperiodic changes in the local input impedance which could not be conventionally designed becomes feasible, thereby high-performance radio than conventional An absorber and its design method can be realized.
以下、図面を参照しながら本発明の好適な実施の形態を詳述する。なお、各図面に示される同一または同等の構成要素、部材等には同一の符号を付し、適宜重複した説明は省略する。また、実施の形態は発明を限定するものではなく例示であり、実施の形態に記述されるすべての特徴やその組み合わせは必ずしも発明の本質的なものであるとは限らない。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.
一もしくは複数の界面から電波反射層を見込んだ入力インピーダンスは一般に、層の電気定数、層の厚み、層間界面と入射電波の成す入射角により変化する。したがって、本発明の実施の形態に係る電波吸収体では、電波吸収体を構成する各層の電気定数を離散的に場所的にランダムに変化させている。すなわち、本発明の実施の形態は、一もしくは複数の界面から電波反射層を見込んだ入力インピーダンスが場所的にランダムに変化していることを特徴とするものである。なお、界面は、電波吸収体の表面すなわち空気層と電波吸収体との境界面を含んでもよい。 In general, an input impedance in which a radio wave reflection layer is expected from one or a plurality of interfaces varies depending on an electrical constant of the layer, a thickness of the layer, and an incident angle formed between the interlayer interface and an incident radio wave. Therefore, a radio wave absorber according to the embodiment of the present invention is to change the electrical constants of each layer constituting the electromagnetic wave absorber in discrete manner spatially random. In other words, the embodiment of the present invention is characterized in that the input impedance in which the radio wave reflection layer is expected from one or a plurality of interfaces changes randomly in place. The interface may include the surface of the radio wave absorber, that is, the boundary surface between the air layer and the radio wave absorber.
図１（Ａ）は、層構造を有する電波吸収体の構造断面図である。図１（Ｂ）は、参考例１であって、界面上の局所入力インピーダンス（Ｚin）が場所的にランダムに連続的に変化している様子を示す説明図である。図１（Ｃ）は、本発明に係る電波吸収体の第１の実施の形態であって、界面上の局所入力インピーダンスが場所的にランダムに離散的に変化している様子を示す説明図である。 FIG. 1A is a structural cross-sectional view of a radio wave absorber having a layer structure. FIG. 1B is an explanatory diagram illustrating a state in which the local input impedance (Zin) on the interface is continuously and randomly changed in place in Reference Example 1 . FIG. 1C is an explanatory diagram showing a state in which the local input impedance on the interface is randomly and discretely changed locally in the first embodiment of the radio wave absorber according to the present invention. is there.
図２（Ａ）は、参考例２であって、電波吸収体を構成する一もしくは複数の層の電気定数が場所的にランダムに連続的に変化している様子を示す説明図である。図２（Ｂ）は、本発明に係る電波吸収体の第２の実施の形態であって、電波吸収体を構成する一もしくは複数の層の電気定数が場所的にランダムに離散的に変化している様子を示す説明図である。 FIG. 2A is a reference example 2 and is an explanatory diagram showing a state in which the electrical constants of one or a plurality of layers constituting the radio wave absorber change continuously and randomly in place. FIG. 2 (B), a second embodiment of the radio wave absorber according to the present invention, the electric constant one or more layers of the electromagnetic wave absorber is spatially discretely change randomly It is explanatory drawing which shows a mode that it is.
図３（Ａ）は、参考例３であって、電波吸収体を構成する一もしくは複数の層の厚みがランダムに連続的に変化している様子を示す断面図である。図３（Ｂ）は、参考例４であって、電波吸収体を構成する一もしくは複数の層の厚みがランダムに離散的に変化している様子を示す断面図である。図３（Ｃ）は、参考例５であって、電波吸収体を構成する一もしくは複数の層間界面の傾きがランダムに離散的に変化している様子を示す断面図である。 FIG. 3A is a cross-sectional view showing a third example in which the thickness of one or more layers constituting the radio wave absorber is randomly and continuously changed. FIG. 3B is a cross-sectional view showing a fourth example of the reference example 4 in which the thickness of one or a plurality of layers constituting the radio wave absorber is randomly and discretely changed. FIG. 3C is a cross-sectional view showing Reference Example 5 in which the inclination of one or a plurality of interlayer interfaces constituting the radio wave absorber is randomly and discretely changed.
本発明者は、一もしくは複数の界面から電波反射層を見込んだ入力インピーダンスを層間界面上で場所的にランダムに変化させた場合、従来の入力インピーダンスが一様な電波吸収体に較べて電波吸収量や電波吸収帯域が改善されることを見いだした。入力インピーダンスと電波反射率の観点からこの吸収原理について以下詳述する。 When the input impedance in which the radio wave reflection layer is expected from one or a plurality of interfaces is randomly changed on the interlayer interface, the inventor absorbs radio waves as compared with a radio wave absorber having a uniform input impedance. We found that the quantity and the radio wave absorption band were improved. This absorption principle will be described in detail below from the viewpoint of input impedance and radio wave reflectance.
従来の層構造電波吸収体では、振幅反射率Γは電波吸収体表面で一様な定数であったが、本発明の実施の形態では層の厚み、電気定数、界面の局所的な傾きが場所ごとにランダム変動することにより局所入力インピーダンスＺinがランダムとなり、局所振幅反射率Γも電波吸収体表面上のランダム関数となる。 In the conventional layered structure wave absorber, the amplitude reflectance Γ is a uniform constant on the surface of the wave absorber, but in the embodiment of the present invention, the thickness of the layer, the electrical constant, and the local inclination of the interface are the places. local input impedance Z in by random fluctuation is random, even local amplitude reflectance Γ becomes random function on the wave absorber surface every.
一例として面積Ｓを有する電波吸収体の表面を仮想的に面積Ｓnを有するＮ個のセルに分割し、各セルの入力インピーダンスをランダム化した場合を考える。遠方界領域における反射率は、下記式(3)に示すように、個々のセルの振幅反射率Γnと、面積の重み付けをした係数αnとの積の総和となる。 Dividing the surface of the wave absorber having an area S as an example the N cells with virtually area S n, consider the case where randomized input impedance of each cell. The reflectance in the far-field region is the sum of products of the amplitude reflectance Γ n of each cell and the coefficient α n weighted for the area, as shown in the following formula (3).
ただし、Γnはセルの位置と観測点間の距離差に伴う位相差を考慮したものとする。この式で従来の電波吸収体は、αn＝１／Ｎ，Γn＝Γであり、フェーザー表示すると図５（Ａ）に示すように同一のΓ／Ｎを有する複素数である振幅反射率（符号１０で示す）がＮ個、コヒーレントに加算されている。 However, Γ n is assumed to take into account the phase difference accompanying the distance difference between the cell position and the observation point. In this equation, the conventional wave absorber is α n = 1 / N, Γ n = Γ, and when expressed in phaser, the amplitude reflectivity (which is a complex number having the same Γ / N as shown in FIG. 5A) ( N (indicated by reference numeral 10) are coherently added.
一方、本発明の実施の形態では、Γnの振幅は従来のものよりも大きくなるものもあるが、位相がランダムであるため、それらを加算したものは図５（Ｂ）に示すように、前記コヒーレントに加算した従来の電波吸収体の反射率よりも小さくなる場合がある。 On the other hand, in the embodiment of the present invention, the amplitude of Γ n may be larger than the conventional one, but since the phase is random, the sum of them is as shown in FIG. In some cases, the reflectivity of the conventional wave absorber added coherently becomes smaller.
また、ホイヘンスの原理によれば、図６に示すように入射レイ６及び波面１１を有する平面入射波が各セルに照射されると、各セルを波源とする２次球面波が発生し、界面近傍ではこれらの合成として散乱波が形成される。従来の電波吸収体界面においては、この２次球面波が相関性を持って加算されるため、図６（Ａ）に示すようにその波面１２は平面状となりレイ７も空間的に同一方向を有する。 Further, according to Huygens' principle, when a plane incident wave having an incident ray 6 and a wavefront 11 is irradiated to each cell as shown in FIG. 6, a secondary spherical wave having each cell as a wave source is generated, and the interface In the vicinity, a scattered wave is formed as a combination of these. At the conventional wave absorber interface, the secondary spherical wave is added with correlation, so that the wavefront 12 becomes planar as shown in FIG. 6A, and the ray 7 also has the same spatial direction. Have.
一方、本実施の形態の電波吸収体では、前記２次球面波の相関性が小さいため、合成された波面１２は図６（Ｂ）に示すように凹凸状を有する曲面となりレイ７は拡散散乱され、鏡面反射方向の反射率は減少し、レイの伝搬長が伸長することにより電波吸収減衰の効果が大きくなる。 On the other hand, in the radio wave absorber of the present embodiment, since the correlation of the secondary spherical wave is small, the synthesized wavefront 12 becomes a curved surface having an uneven shape as shown in FIG. As a result, the reflectivity in the specular reflection direction is reduced, and the propagation length of the ray is extended, so that the effect of attenuation of radio wave absorption is increased.
本実施の形態によれば、下記の効果を奏することができる。 According to the present embodiment, the following effects can be achieved.
(1) 電波吸収体の電気定数を界面上の場所ごとの設計パラメータとして取り込むことにより、従来設計できなかった局所入力インピーダンスのランダム化が実現可能となり、これにより従来よりも高性能の電波吸収体が実現することができる。 (1) by incorporating the electrical constants of the wave absorber as a design parameter for each location on the surface, randomization of the local input impedance which could not be conventionally designed becomes feasible, thereby high-performance wave absorption than conventional The body can be realized.
(2) さらに、層の厚みもしくは界面の傾きを場所的に変化させた結果として層間界面が粗面となる場合は、層間界面の密着度が増し、隣接層が剥がれにくいという副次的な効果も期待できる。 (2) Furthermore, when the interlayer interface becomes rough as a result of changing the thickness of the layer or the inclination of the interface, the secondary effect that the adhesion of the interlayer interface increases and the adjacent layer is difficult to peel off. Can also be expected.
(3) また、電波的な欺瞞性を高めるために航空機等に電波吸収塗料を塗布し、さらに可視光における欺瞞も行うためにトップコートとして複数種の塗装(例えば迷彩塗装)を施した場合、局所的な電気特性が同じである従来の電波吸収塗料では、複数種の塗装の局所的なインピーダンスの変化に追従できず電波吸収特性が劣化する可能性もあるが、本実施の形態では対応可能となる。 (3) In addition, when radio wave absorbing paint is applied to aircraft etc. in order to enhance radio fraud, and more than one type of coating (e.g. camouflage painting) is applied as a top coat to perform fraud in visible light, Conventional electromagnetic wave absorption paint with the same local electrical characteristics may not be able to follow the local impedance change of multiple types of paints and may deteriorate the radio wave absorption characteristics. It becomes.
以下に、本実施の形態の手法により設計した実施例に係る電波吸収体の吸収性能について、ＦＶＴＤ法を用いた電磁界シミュレータによる結果を示す。 Below, the result by the electromagnetic field simulator using FVTD method is shown about the absorption performance of the electromagnetic wave absorber which concerns on the Example designed by the method of this Embodiment.
垂直入射において８ＧＨｚに吸収ピークを有するように設計された一辺長が１５０ｍｍ、第一層及び第二層の厚みがそれぞれ１ｍｍ、第一層の誘電率が１４.５−ｊ０.４４、第二層の誘電率が５.０−ｊ０.４４５、第一層及び第二層の透磁率がそれぞれ２.１−ｊ１.９５の二層構造電波吸収層を電波反射層で裏打ち（電波到来方向よりみて第一層の裏面に電波反射層を配置）した電波吸収体を基準電波吸収体とする。この基準電波吸収体を一辺長３０ｍｍの２５個のセルに分割し、第一層の電気定数のうち誘電率の実数部を図７（Ａ）に示すようにセルごとに変化させたものが本実施例の電波吸収体である。変化量は、離散一様確率分布に従いランダム化したものである。すなわち、離散一様分布に従う確率変数をセルごとに発生させて変化量としている。垂直入射における本実施例の電波吸収体の電波吸収量を基準電波吸収体の電波吸収量と対比して図７（Ｂ）に示す。 Designed to have an absorption peak at 8 GHz at normal incidence, the length of one side is 150 mm, the thickness of the first layer and the second layer is 1 mm, the dielectric constant of the first layer is 14.5-j0.44, the second layer The two-layer structure radio wave absorption layer having a dielectric constant of 5.0-j0.445 and a magnetic permeability of the first and second layers of 2.1-j1.95 is lined with a radio wave reflection layer (as viewed from the direction of radio wave arrival). A radio wave absorber having a radio wave reflection layer disposed on the back surface of the first layer is defined as a reference radio wave absorber. This reference wave absorber is divided into 25 cells each having a side length of 30 mm, and the real part of the dielectric constant of the electric constant of the first layer is changed for each cell as shown in FIG. It is the electromagnetic wave absorber of an Example. The amount of change is randomized according to a discrete uniform probability distribution. That is, a random variable according to a discrete uniform distribution is generated for each cell and used as a change amount. FIG. 7B shows the radio wave absorption amount of the radio wave absorber of the present embodiment at normal incidence in comparison with the radio wave absorption amount of the reference radio wave absorber.
図から明らかなように、本手法による電波吸収体は基準電波吸収体よりも吸収性能が向上しており、本手法の有効性が確認された。 As is apparent from the figure, the radio wave absorber of this method has improved absorption performance compared to the standard radio wave absorber, and the effectiveness of this method has been confirmed.
（参考例６）
前記基準電波吸収体において、電波吸収層の全体厚みを２ｍｍに固定し、第一層の厚みを図８（Ａ）に示すようにセルごとに変化させたものが本参考例の電波吸収体である。変化量は、離散一様分布に従いランダム化したものである。すなわち、離散一様分布に従う確率変数をセルごとに発生させて変化量としている。垂直入射における本参考例の電波吸収体の電波吸収特性を基準電波吸収体の電波吸収量と対比して図８（Ｂ）に示す。この場合も、実施例１と同様に本手法を適用する前よりも吸収性能が向上しており、本手法の有効性が確認された。
(Reference Example 6)
In the reference wave absorber, the wave absorber of this reference example is obtained by fixing the entire thickness of the wave absorber layer to 2 mm and changing the thickness of the first layer for each cell as shown in FIG. is there. The amount of change is randomized according to a discrete uniform distribution. That is, a random variable according to a discrete uniform distribution is generated for each cell and used as a change amount. FIG. 8B shows the radio wave absorption characteristics of the radio wave absorber of the present reference example at normal incidence in comparison with the radio wave absorption amount of the reference radio wave absorber. Also in this case, the absorption performance was improved as compared to before applying the present method, as in Example 1, and the effectiveness of the present method was confirmed.
（参考例７）
前記基準電波吸収体において、電波吸収層の全体厚みを２ｍｍに固定し、第一層の厚みを図９（Ａ）に示すように、参考例６とは異なる分布にした場合の垂直入射における電波吸収特性を図９（Ｂ）に示す。この場合も、参考例６と同様に本手法を適用する前よりも吸収性能が向上しており、本手法の有効性が確認された。
(Reference Example 7)
In the reference wave absorber, the radio wave at normal incidence when the entire thickness of the radio wave absorption layer is fixed to 2 mm and the thickness of the first layer is different from that of Reference Example 6 as shown in FIG. Absorption characteristics are shown in FIG. In this case as well, the absorption performance was improved as compared to before applying this method as in Reference Example 6, and the effectiveness of this method was confirmed.
以上、実施の形態及び実施例を例に本発明を説明したが、実施の形態の各構成要素や各処理プロセスには請求項に記載の範囲で種々の変形が可能であることは当業者に理解されるところである。 Although the present invention has been described above by way of embodiments and examples, it will be understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiments within the scope of the claims. It is understood.
本発明の実施例においては、矩形状の同一面積のセルを用いているが、面積及び形状は任意でもよく、面積を微細化した極限においては、厚み変化は連続となり厚みの確率分布も離散分布から連続分布に移行する。なお、形状の別の例としては三角形や六角形等の多角形が挙げられる。 In actual施例of the present invention, is used a cell having the same area of the rectangular shape, area and shape may be arbitrary, in the limit of the area is miniaturized, the thickness change is the probability distribution of the thickness is obtained as a continuous discrete Transition from distribution to continuous distribution. Another example of the shape is a polygon such as a triangle or a hexagon.
厚みは離散一様分布に従う乱数を発生させ生成したが、他の平均と分散を有する離散確率分布（例えば二項分布、ポアソン分布、負の二項分布、ベルヌーイ分布、超幾何分布、多項分布、もしくはジップ分布）に従ってもよい。 The thickness was generated by generating random numbers according to the discrete uniform distribution, but other discrete probability distributions with mean and variance (eg binomial distribution, Poisson distribution, negative binomial distribution, Bernoulli distribution, hypergeometric distribution, multinomial distribution, Or it may follow a zip distribution) .
実施例においては垂直入射についての設計例を示したが、任意の角度の斜入射についても、同様の設計手法により従来よりも電波吸収性能の向上を図ることが可能である。また、実施例においては８ＧＨｚを吸収ピークとして６〜１０ＧＨｚを主な吸収範囲としたが、吸収ピーク及び主な吸収範囲は任意であり、例えばＶＨＦ帯、ＵＨＦ帯、ＳＨＦ帯その他の周波数帯から適宜選択可能である。 Although a design example for normal incidence in real施例, for the oblique incidence of any angle, it is possible to improve the radio wave absorption performance than the conventional by the same design technique. Although a main absorption range 6~10GHz as absorption peak 8GHz in real施例absorption peak and main absorption range is arbitrary, e.g. VHF band, UHF band, from SHF band other frequency bands It can be selected as appropriate.
従来の層構造電波吸収体では、層に関して均一な電気定数、均一な厚み、周期的な構造パターンという三種類の設計パラメータのみで電波吸収体を設計実現していたが、本発明は層の局所的な電気定数の不均一化という概念を取り入れることにより設計条件範囲を広げることを提案し、従来に較べ電波吸収特性をより向上させた電波吸収体を実現できる。 In the conventional layered structure wave absorber, the wave absorber is designed and realized with only three kinds of design parameters, that is, a uniform electrical constant, a uniform thickness, and a periodic structure pattern for the layer . It is proposed to expand the range of design conditions by adopting the concept of uneven electrical constant, and a radio wave absorber with improved radio wave absorption characteristics as compared with the conventional one can be realized.
１ 電波反射層
２，２Ａ，２Ｂ 電波吸収層
３ 電波整合層
４ 電波表面層
５ 電波吸収体の界面
６ 入射レイ
７ 反射レイ
８ 透過レイ
９ 全反射レイ
１０ 各セルの反射率のフェーザー表示
１１ 入射電波の波面
１２ 反射電波の波面
DESCRIPTION OF SYMBOLS 1 Radio wave reflection layer 2, 2A, 2B Radio wave absorption layer 3 Radio wave matching layer 4 Radio wave surface layer 5 Radio wave absorber interface 6 Incident ray 7 Reflected ray 8 Transmitted ray 9 Totally reflected ray 10 Phaser display 11 of reflectance of each cell Incident Wave front 12 Radio wave reflected
Claims (7)
セル構造を有し、電波吸収体を構成する各層のうち少なくとも一つの層の誘電率の実部、透磁率の実部、及び透磁率の虚部の少なくとも一つが場所的に非周期的かつセルごとに離散的に変化し、その変化量が平均と分散を有する確率分布に従うことを特徴とする電波吸収体。 A radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, a radio wave matching layer, and a radio wave surface layer, or a radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, and a radio wave surface layer, or a radio wave reflection layer and a radio wave absorption layer An electromagnetic wave absorber made of
At least one of the real part of the dielectric constant, the real part of the magnetic permeability, and the imaginary part of the magnetic permeability of the at least one of the layers constituting the electromagnetic wave absorber having a cell structure is locally aperiodic and a cell An electromagnetic wave absorber characterized in that it varies discretely and follows a probability distribution in which the amount of change has an average and variance.
平均と分散を有する確率分布に従う確率変数をセルごとに発生させて、その発生した確率変数に基づいて前記誘電率の実部、前記透磁率の実部、及び前記透磁率の虚部の少なくとも一つの変化量をセルごとに決定することを特徴とする電波吸収体の設計方法。 A radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, a radio wave matching layer, and a radio wave surface layer, or a radio wave absorber composed of a radio wave reflection layer, a radio wave absorption layer, and a radio wave surface layer, or a radio wave reflection layer and a radio wave absorption layer A reference wave absorber having an input impedance that is uniform from the interface and having a uniform input impedance from the interface, is virtually divided into cell structures, and each of the layers constituting the reference wave absorber is divided into cell structures. A method of designing a radio wave absorber, wherein a design value is obtained by changing at least one of the real part of the dielectric constant, the real part of the magnetic permeability, and the imaginary part of the magnetic permeability of each layer among the cells. ,
A random variable according to a probability distribution having a mean and variance is generated for each cell, and at least one of the real part of the dielectric constant, the real part of the magnetic permeability, and the imaginary part of the magnetic permeability is based on the generated random variable. A method of designing a radio wave absorber, wherein one change amount is determined for each cell.
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