JP4027775B2 - Slot array antenna - Google Patents

Description

の間にあって、前記スロット板を所定の寸法および形状に裁断し、必要に応じて位置合わせの穴を設け、前記導体板側と導波管プレートとを向かい合わせ、位置合わせ手段を用いて位置合わせを行ってから、導電性固着手段を用いて電気的に接続させ、前記放射指向性主ビームのチルト角θが、表面傾斜角αを有する前記誘電体板による屈折で略零度に補正されることにより、前記放射指向性主ビームが傾かずに前記導波管プレートと垂直になり、しかも、前記誘電体板が外側に向くように構成されることにより、前記誘電体板がレードームの役割も果たすことを特徴とする。
【００４９】
〔２〕上記〔１〕記載のスロットアレーアンテナにおいて、前記スロット板を構成する誘電体板と導体板がそれぞれ独立に加工された後、前記導波管プレートの表面に前記導体板を所定の位置に配置し、位置合わせの部材を用いて位置を合わせてから導電性固着手段を用いて固定すると同時に電気的に接続させ、その上に前記誘電体板を所定の位置に配置し、固着手段を用いて固定することを特徴とする。
【００５０】
【発明の実施の形態】
以下、本発明の実施の形態について詳細に説明する。
【００５１】
一般的に全てのアンテナには可逆定理が成立しているため、送信特性と受信特性はまったく同じなので以下に述べる説明には断りがない限りすべて送信の場合の説明であるが、受信の場合も同様なので説明は省略する。
【００５２】
図１は本発明の実施例を示すスロットアレーアンテナの構成図であり、図１（ａ）はその放射導波管の軸に沿った断面図、図１（ｂ）はその放射導波管を横断する方向の断面図である。図２はそのスロットアレーアンテナの主ビームのチルト角θとそのスロット板誘電体部の傾斜角αの関係を示す図である。
【００５３】
従来のスロット板を用いれば、チルト角θが零度でないため、放射指向性の主ビームが導波管プレートの垂直方向から、図１０に示すように、導波管軸に沿って給電口側またはその反対側に傾くが、ここでは、図１１に示すように給電口の反対側に傾く場合を採用している。
【００５４】
図１（ａ）は放射導波管軸に沿った断面図である。ここでは、１は従来の導波管プレート、２は給電口側、３はスロット板の導体部（導体板）、４はスロット板の誘電体部（誘電体板）、５はアンテナの放射指向性、６はアンテナの正面方向を示す矢印である。
【００５５】
この実施例では、スロット板の導体部３は薄く、例えば厚み０．１ｍｍ以下の銅箔でできており、スロット板の誘電体部４の片面に張り合わされている。前記導体部３にはエッチング技術等で所定の位置にスロット素子の加工が施される。導波管プレート１とスロット素子の寸法と位置は、従来と同様にアンテナ全体の周波数帯域幅が広くなるように設計されるので、放射指向性主ビームのチルト角θが零度でなくなるわけである。このチルト角θをほぼ零度に補正、すなわち放射指向性主ビームを導波管プレート１に垂直になるようにするために、前記誘電体部４に傾斜角を持たせる方法を採用した。
【００５６】
前記誘電体部４は、スロットアレーアンテナの周波数帯域において、低損失な誘電体材料でできており、すなわち、電磁波をほとんど吸収せずに通過させる。言い換えれば、電磁波にとって極めて透明な材料である。また、前記誘電体材料は誘電率εを有するが、入射される電磁波を反射させたり、屈折させたりし、光線と透明ガラスの場合と同様である。
【００５７】
したがって、光学で扱われている多くの法則はこのまま電磁波と誘電体４にも適用できることがよく知られている。例えば、誘電体部４の誘電率がεで、比誘電率がε_r とすれば、屈折率ｎはほぼε_r の平方根に等しい。すなわち、
【００５８】
【数３】

本発明では、放射指向性の主ビームチルト角を補正するために、誘電体材料による電磁波の屈折現象を利用することが重要なポイントである。
【００５９】
本発明の実施例の誘電体部４を、給電口の反対側に傾く主ビームのチルト角θを補正する機能をもたせるためには、図１（ａ）に示すように、給電口２の反対側に傾斜角を持たせることである。すなわち、誘電体部４の片面は平面で、スロット素子を施された導体部２と張り合わされているが、もう片面は、前記導体部２と張り合わせられた面に対して平行ではなく、傾斜角αをなしており、誘電体は露出している。
【００６０】
零度でないチルト角θを有する放射指向性のビームが、誘電体部４を通過する過程で、屈折によってチルト角θが略零度に補正されるためには、前記傾斜角αは次式のように与えられる：
【００６１】
【数４】

式（２）から明らかなように主ビームのチルト角θと誘電体部の屈折率ｎが決まれば、誘電体部の傾斜角αを計算することができるが、傾斜角αの値を一義的に決められるためには次のような条件を考慮する必要がある。すなわち、前記チルト角θは通常、数度以内の正の微小角なので、式（２）の解の中から、最小の正の値を前記傾斜角αにすることが望ましい。
【００６２】
図２は式（２）をグラフ化したものであり、誘電体部の屈折率ｎを１．４から２．０まで変化させた。グラフから明らかなように、ｎの値が大きくなるに連れて傾斜角αのちょっとした変動でもθに大きな影響を与えることが分かる。したがって、誘電体部斜面を加工するとき、誘電体材料の比誘電率ε_r または屈折率ｎが大きければ大きいほど傾斜角αの高い加工精度が要求されるわけである。実用的にはｎの値は２以下になることが望ましい。
【００６３】
また、前記傾斜角αの値を、前記チルト角θと同様に数度以内の正の微小角にするためには前記屈折率ｎが式（３）を満たす必要がある。
【００６４】
【数５】

常用の誘電体の屈折率ｎは容易に式（３）を満足する。例えば、テフロン（登録商標）のような低誘電率材料でも、比誘電率ε_r が約２．７、屈折率に換算するとｎは１．６４になるので式（３）は満足する。
【００６５】
一方、放射指向性のビームを給電口側２の方に傾ければ、前記誘電体部４の導体部３と張り合わせられていない側の上部の面も給電口側２の方に傾き、そのとき傾斜角αも式（２）から計算される。すなわち、前記誘電体部４の上部の面を、放射指向性主ビームの傾く側に傾斜角αで傾かせれば、零度でないチルト角θを略零度に補正できる。
【００６６】
図１（ｂ）は放射導波管の断面を含む本発明の実施例のアンテナの断面図であり、７は放射導波管の断面である。
【００６７】
本実施例のスロット板の加工は下記のように行われる。
【００６８】
まず、スロット板の作製に必要な定数を求めておかなければならないので、すでに決まった値から計算する。
【００６９】
本実施例に用いた導波管プレート１は、厚み０．０１８ｍｍの銅箔で造ったスロット板の導体部３と組み合わせてスロットアレーアンテナを得た場合、アンテナ全体の放射指向性の主ビームチルト角θが２．８°になるように設計されたものである。
【００７０】
また、スロット板の誘電体部４に用いた材料は比誘電率約２．７のテフロン（登録商標）なので、その屈折率ｎは１．６４になる。これらのθとｎの値を式（２）に代入すると、スロット板の誘電体部４の傾斜角αは約４．３°になる。図２では、８が本発明の実施例のチルト角θと傾斜角αの関係位置である。
【００７１】
一方、導波管プレートの導波管軸方向の全長Ｌが７０．０ｍｍ、誘電体部４の一番薄いところｈ₀ を０．８ｍｍとすれば、誘電体部４の一番厚いところｈは式（４）を用いて計算すると６．０ｍｍになる。
【００７２】
ｈ＝ｈ₀ ＋Ｌ×ｔａｎα （４）
したがって、スロット板の誘電体部４に用いるテフロン（登録商標）基板の厚みは６．０ｍｍ以上が望ましいわけであるが、本実施例では厚み６．０ｍｍのテフロン（登録商標）基板を使うことにする。
【００７３】
前記テフロン（登録商標）基板の片面に導体板３として厚み０．０１８ｍｍの銅箔を張り合わせてから、その銅箔の上にエッチング技術を用いて所定の位置に、所定の寸法（０．２４ｍｍ×１．８５ｍｍ）および形状（両端半円の長方形）のスロット素子を形成する。この時、テフロン（登録商標）基板のもう片面は露出したままで、図１（ａ）に示すように、前記傾斜角α（＝４．３°）が得られるように、前記テフロン（登録商標）基板露出面（導体部３と張り合わされていない面）を斜めに裁断する。結果的に、給電口２側端におけるテフロン基板の厚みはｈ（＝６．０ｍｍ）で、給電口２の反対側端の厚みはｈ₀ （＝０．８ｍｍ）になる。また、組み立てるときを考慮して、スロット側の周囲の寸法も導波管プレート１と同じ寸法に裁断する必要がある。そして、裁断したテフロン（登録商標）基板の表面が滑らかになるように表面処理を行ってから、スロット板全体を洗浄すれば加工作業は完了するが、銅箔の腐蝕を防止するためにメッキ作業等を施しても良い。
【００７４】
次の作業は、導波管プレートの上に前記スロット板を取り付けることである。前記導波管プレートをスロット素子を有する導波管の列にするためには、前記加工したスロット板の銅箔側を、所定の位置に導波管プレートと直接、電気的に接続させ、導電性接着剤またはネジで固定すれば、本願実施例のスロットアレーアンテナが完成する。
【００７５】
以下、本発明のスロットアレーアンテナの動作の説明を行う。
【００７６】
本発明のスロットアレーアンテナの動作と、従来のスロットアレーアンテナの動作との違いは、放射電磁波が放射指向性主ビームチルト角補正用誘電体板を通過しなければならないところが異なるところである。つまり、スロットから放射する電磁波がテフロン（登録商標）板を通過しなければならないので、厳密にいえば、前記テフロン（登録商標）板による吸収と反射の影響は避けられない。
【００７７】
しかし、本発明の実施例では、比誘電率が略２の誘電体材料であるテフロン（登録商標）を採用し、その厚みも７０ＧＨｚ帯の電磁波からみても薄く、数ミリなので、前記テフロン（登録商標）板による特性への悪影響は無視できる範囲であると考える。したがって、動作の説明は従来のスロットアレーアンテナと全く同じである。
【００７８】
まず、スロットアレーアンテナ本体の動作は図９を用いて説明する。
【００７９】
従来のスロットアレーアンテナの外観は図９に示す通りである。給電口４３１から電磁波を給電すると、電磁波は給電回路を通過してそれぞれの放射導波管に給電され、さらにスロット板のスロット素子４２１から放射される。アンテナ内部の給電回路および放射導波管を通過した過程で、各々のスロット素子に給電される電磁波の電力はある分布、例えば、テイラー分布や一様分布に従うように調整されるので、放射指向性の主ビームに放射電力が集中し、高い放射効率を得る。放射効率が高ければ高いほど放射電磁波がより遠方に届く。
【００８０】
次に、テフロン（登録商標）板における、スロットから放射された直後の電磁波の屈折について図３を用いて説明する。図３は図１（ａ）を部分的に拡大したものなので、そこで使用した名称もこのまま使用する。
【００８１】
図３は本発明の実施例を示すスロットアレーアンテナのスロット板誘電体部による放射指向性主ビームの屈折の説明図である。
【００８２】
この図において、１１は導波管プレート、１２はスロット板の導体部（導体板）、１３はスロット板の誘電体部（誘電体板）、１４は放射指向性主ビーム（放射電磁波）である。
【００８３】
図３では点Ａはスロット板銅箔表面Ｐ１上の一点で、１４は放射指向性主ビームを表している。十分遠方からみれば一般的にアンテナを一点とみなすことができるので放射指向性主ビーム１４の出発点は前記点Ａと考えられ、放射指向性主ビーム１４は放射電磁波ではあるが、一本の光線のようにみなすこともできる。
【００８４】
この場合の放射指向性主ビーム１４のチルト角はθなので、放射指向性主ビーム１４はＰ１の垂線となす角度θになる。主ビーム１４は点Ａにおいて誘電体部１３によって屈折し、その屈折角はθ₁ である。中心周波数において、誘電体部１３の比誘電率がε_r なので、屈折率ｎは式（１）に示すようになる。また、チルト角θと屈折角θ₁ では式（５）に示すようなスネルの法則で結ばれている：
ｓｉｎθ＝ｎ×ｓｉｎθ₁ （５）
屈折した放射電磁波１４は誘電体部１３を通過し、もう片側の表面Ｐ２に達すと点Ｂから自由空間に放射することになる。点Ｂにおいて、１４は再屈折し、スロット板銅箔表面Ｐ１に垂直な方向に伝搬する。そのときの屈折角はαである。幾何学の定理によれば、屈折角αは誘電体部１３の傾斜角と等しい。
【００８５】
また、本来放射電磁波１４はチルト角θを有するが、この二回の屈折で、伝搬方向がＰ１に垂直になるということはチルト角θが「零度」に補正されたことを意味する。これらの条件のもとで、関係式を整理すると次式が得られる：
ｎ×ｓｉｎ（α−θ₁ ）＝ｓｉｎα （６）
式（５）と式（６）からαを計算すると、式（２）が得られる。
【００８６】
このように、スロット板の誘電体部１３の屈折によって放射指向性主ビームのチルト角θが「零度」に補正されるが、アンテナの導波管プレート１１とスロット素子を施されたスロット板１２の銅箔の形状と寸法はこのまま残るので、アンテナの周波数帯域は変わることなく、広帯域のままである。
【００８７】
本発明のスロット板の誘電体部は、放射指向性主ビームチルト角を補正すると同時に、スロットアレーアンテナのレードームの役割も果たしている。
【００８８】
また、本発明は、以下のような利用形態を有する。
【００８９】
本発明のスロットアレーアンテナはミリ波通信用に適し、近年ＥＴＣやＩＴＳのアンテナとして使われることは従来のスロットアレーアンテナと同じように可能である。
【００９０】
また、スロット素子の数を増やせば放射利得がさらに高くなり、主ビーム幅も鋭くなるので、パラボラアンテナのような高利得アンテナを必要とするシステムにも利用できる。例えば、電話通信基地局中継用アンテナ、テレビ基地局中継用アンテナ、衛星通信用アンテナ、電波天文学の電波望遠鏡用アンテナ等が挙げられる。
【００９１】
更に、本発明は以下のような変形実施例を挙げることができる。
【００９２】
本発明の実施例では、図１１に示すように、放射指向性主ビームが給電口の反対側に傾く場合の導波管プレートとスロット素子の配置を採用し、改善策を説明したが、放射指向性主ビームが給電口側に傾く場合では、スロット板の設計と加工も同様に式（２）を用いて誘電体部の傾斜角αを計算して行うが、誘電体部の傾斜面は放射指向性主ビームと同様に給電口側に傾くことになるので、このような変形例も考えられる。
【００９３】
また、本発明の実施例のスロット板は、誘電体基板の片面に銅箔を張り合わせて、銅箔上にエッチング技術でスロット素子を形成して造られたが、ある程度の厚みを有する導体板、例えば厚み０．１ｍｍ以上のステンレス板または厚み０．２ｍｍ以上のアルミニウム板、銅板の上にスロット素子を形成すると別に、傾斜角αを有する誘電体板を加工してから導電性接着剤や通常接着剤またはネジを用いて導波管プレートの上に固定しアンテナを完成させるような変形例も考えられる。
【００９４】
この他に、例えば、所定の厚みの誘電体を有する市販のプリント基板を用いて本発明の実施例と同様にスロット板を造れば、アンテナの更なる低価格化が望めるので、このような変形例も考えられる。
【００９５】
なお、本発明は上記実施例に限定されるものではなく、本発明の趣旨に基づいて種々の変形が可能であり、これらを本発明の範囲から排除するものではない。
【００９６】
【発明の効果】
以上、詳細に述べたように、本発明によれば、従来のスロット板の代わりに、前記レードーム付きスロット板を用いることによって、次のような効果が挙げられる。
【００９７】
（１）従来、スロットアレーアンテナのスロット板表面を保護するために必要なレードームが不要になるので、部品点数が少なくなり、アンテナの低価格化が促進される。
【００９８】
（２）スロット板と誘電体板が一体化されるので、アンテナがコンパクトとなり、小型化も促進される上に、実装も簡素化されるので低価格化がさらに進む。
【００９９】
（３）従来のスロット板は、材質によって異なるが、ある程度の厚みをもたないと精密な寸法を維持することができず（例えば、アルミニウムの場合では薄くても０．２ｍｍまで、ステンレスの場合では０．１ｍｍまで）、このような厚みを有するために、スロットを加工するときになかなか計算通りの寸法を得ることができない。しかし、本発明の実施例のように、スロット板となる導体板を誘電体板に張り合わせたので導体板が０．０１８ｍｍのように薄くても十分に使用可能である。スロット板の厚みが薄ければ薄いほどスロットの形状および寸法が計算値に近くなるので設計と試作が容易に行え、アンテナ特性の向上が期待できる。
【０１００】
（４）誘電体板に傾斜角αを持たせることによって、放射指向性主ビームのチルト角θが補正されるので、実装するとき、従来のように無駄なスペースがなくなるばかりでなく、アンテナ主ビーム方向の調整も不要となり、通信装置の小型化と低価格化に貢献できる。
【０１０１】
（５）本発明のスロット板は、市販のプリント基板でも使用可能なので従来のスロット板だけと比較しても十分安価なものである。
【０１０２】
したがって、本発明はスロットアレーアンテナの高性能化、小型化および低価格化に大きく貢献するといえる。
【図面の簡単な説明】
【図１】 本発明の実施例を示すスロットアレーアンテナの構成図である。
【図２】 本発明の実施例を示すスロットアレーアンテナの主ビームのチルト角θとそのスロット板誘電体部の傾斜角αの関係を示す図である。
【図３】 本発明の実施例を示すスロットアレーアンテナのスロット板誘電体部による放射指向性主ビームの屈折の説明図である。
【図４】 従来の二次元的なアレーアンテナの基本構成図である。
【図５】 単一方形導波管を用いたスロットアレーアンテナの構成例を示す図である。
【図６】 従来の二次元的なスロットアレーアンテナを示す分解斜視図である。
【図７】 従来の二次元的なスロットアレーアンテナのスロット板の平面図である。
【図８】 従来のスロットアレーアンテナの導波管プレートの平面図である。
【図９】 従来のスロット板と導波管プレートを接着させた後のスロットアレーアンテナの立体図である。
【図１０】 スロットアレーアンテナの放射指向性主ビームのチルト角の説明図である。
【図１１】 インピーダンス不整合抑制を施した従来のスロットアレーアンテナの断面図である。
【図１２】 従来のレードームを備えたスロットアレーアンテナの断面図である。
【符号の説明】
１，１１ 導波管プレート
２， 給電口側
３，１２ スロット板の導体部（導体板）
４，１３ スロット板の誘電体部（誘電体板）
５ アンテナの放射指向性
６ アンテナの正面方向を示す矢印
７ 放射導波管の断面
８ 実施例に用いたチルト角θと傾斜角αの関係位置
１４ 放射指向性主ビーム（放射電磁波）[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a slot array antenna, and more particularly to a slot plate of a slot array antenna.
[0002]
[Prior art]
  An array antenna is an antenna system in which a plurality of antennas are arranged in a pattern and can have characteristics that cannot be obtained with a single antenna. By controlling the phase of each element antenna constituting this array antenna, the directivity of the entire antenna system can be controlled, so it can be used as a beam scanning antenna without mechanically moving the antenna body. Can do.
[0003]
  In recent years, with the remarkable development of wireless communication technology, the frequency band allocated to various communication devices tends to be insufficient, and technology development necessary for effective use of frequencies and movement to higher frequencies has been made to compensate for this. It has become an urgent issue.
[0004]
  For example, millimeter waves, which have been used only for basic research in the past, are now being used in intelligent transport systems (ITS), and in the near future, millimeter waves will be used in automobile societies such as Japan and Europe and America. Communication equipment can be expected to be used explosively like home appliances.
[0005]
  Of course, in the field of millimeter wave communication as described above, it is indispensable to make various parts and devices into millimeter waves. Among these, one of the most important devices responsible for millimeter wave communication is an antenna.
[0006]
  Millimeter wave communication is not possible without an antenna that can transmit and receive millimeter wave signals. Currently, research institutes and manufacturers all over the world participating in the research and development of millimeter wave communications are competing to develop high performance millimeter wave antennas.
[0007]
  There are various configurations of millimeter-wave antennas that have been developed so far, and one of the millimeter-wave antennas that is considerably superior in characteristics is a slot array antenna.
[0008]
  As the name suggests, a slot array antenna is an array antenna that is arranged in a certain pattern using a plurality of conventional slot antennas as element antennas. Depending on the size and arrangement of each slot antenna, a desired electric field distribution can be obtained in a certain region. For example, when a plurality of slot antennas are two-dimensionally arranged in a square region, an electric field distribution having a uniform direction, phase and amplitude can be obtained. The radiation characteristics of such an antenna are theoretically almost the same as those of an aperture antenna having a uniform electric field distribution, but the degree of freedom of configuration and the uniformity of the electric field distribution are superior to those of the aperture antenna. There is a point.
[0009]
  FIG. 4 is a basic configuration diagram of a conventional two-dimensional array antenna.
[0010]
  In this figure, reference numeral 20 denotes an array antenna signal source or feeding port, 21 denotes an element antenna constituting the array antenna, and 22 denotes a transmission path connecting each element antenna 21 and the signal source 20. The transmission line 22 serves as a phase shifter as well as a transmission line.
[0011]
  That is, the length of the transmission path 22 from the signal source 20 to each element antenna 21 determines the phase of the electromagnetic wave radiated from each element antenna 21 and has a significant influence on the radiation characteristics of the entire array antenna. When further phase adjustment is required, a phase shifter may be added in series with each transmission line 22.
[0012]
  FIG. 5 shows one configuration of a slot array antenna using a single rectangular waveguide.
[0013]
  In this figure, 31 is a waveguide, 32 is a thin slot which is a slot antenna provided on the tube wall of the waveguide 31, and is generally a rectangular cut. The length of each slot 32 is usually about half of the wavelength λ of the electromagnetic wave input to the waveguide 31, and the width is about 1/20 of that. The arrangement of the slots 32, such as the slot array antenna shown in FIG._TenWhen excited in the mode, a magnetic field is distributed in the length direction of each slot 32, and an electric field is distributed in the width direction.
[0014]
  Unless otherwise noted, all modes of electromagnetic waves in the waveguide handled in the present invention are fundamental modes TE._TenMode. The interval between the slots is generally about half of the in-tube wavelength λg as shown in FIG. 5, and the center interval between adjacent slots 32 in the same row is about the same as the in-tube wavelength λg of the waveguide 31. is there. In order to obtain a desired electromagnetic field distribution on the tube wall of the waveguide 31, it can be realized to some extent by adjusting the size and arrangement of the slots 32. Such a slot array antenna is a one-dimensional array antenna.
[0015]
  Further, when a plurality of the slot array antennas are arranged in parallel, a wide range two-dimensional slot array antenna can be obtained.
[0016]
  Such a slot array antenna has been actively researched and developed and confirmed theoretically and experimentally as one of high gain antennas (Non-patent Document 1).
[0017]
  6 is an exploded perspective view showing a conventional two-dimensional slot array antenna, FIG. 7 is a plan view of a slot plate of the slot array antenna, and FIG. 8 is a plan view of a waveguide plate of the slot array antenna. Hereinafter, unless otherwise noted, a two-dimensional slot array antenna is abbreviated as a slot array antenna. The slot array antenna is mainly composed of a slot plate and a waveguide plate that functions as a waveguide.
[0018]
  In these drawings, reference numeral 411 denotes a slot plate, and 412 denotes a waveguide plate. In general, the slot plate 411 is made of a thin conductor plate, and a plurality of slots 421 serving as element antennas are provided thereon. The waveguide plate 412 is provided with a rectangular groove 437 so that an input electromagnetic wave can be fed from one feeding port 431 on a slightly thick conductor plate to all slots 421 on the slot plate 411. When the slot plate 411 and the waveguide plate 412 are overlapped and bonded together, a row of slots 421 is formed on the tube wall of the waveguide that is arranged in exactly one row, and the entire system becomes a slot array antenna.
[0019]
  The higher the conductivity of the conductors used for the slot plate 411 and the waveguide plate 412, the smaller the automic loss, which contributes to the reduction of the antenna loss. Further, the processing accuracy and adhesion accuracy of the slot plate 411 and the waveguide plate 412 also have a strong influence on the radiation characteristics of the antenna.
[0020]
  In FIG. 7, reference numeral 421 denotes a slot, which is basically rectangular in shape, but may be rounded at both ends for convenience of processing. As described above, the length of the slot 421 is about a half wavelength of the radiated electromagnetic wave length λ, and the width is about 1/20. Further, the center interval between adjacent slots 421 in the same row is approximately the same as the guide wavelength λg of the waveguide.
[0021]
  In FIG. 8, reference numeral 431 denotes a power feeding port, and a portion 432 surrounded by a broken-line ellipse is an H-plane branch in a microwave circuit element when the slot plate 411 and the waveguide plate 412 are bonded. The electromagnetic wave input from the power supply port 431 is bifurcated into an electromagnetic wave having the same phase in terms of power at the left and right at the H plane branch 432. Here, the protrusion 433 serves as a conventional alignment bar for the H-plane branch 432.
[0022]
  The groove connected to the left and right of the H-plane branch 432 becomes a waveguide when the slot plate 411 and the waveguide plate 412 are bonded to each other, and will be referred to as a feed waveguide here. Since the feed waveguide is symmetric with respect to the axis of the feed port 431, the structure of the waveguide plate 412 will be described only on one side. Reference numeral 434 denotes a power feeding port to the radiation waveguide, and the size thereof is approximately the same as the cross section of the power feeding waveguide. A protrusion 435 is provided on the opposite side of each power supply port, and serves as an alignment rod.
[0023]
  Further, the distance between the tip of the feed waveguide and the final feed port is set to about one quarter of the guide wavelength λg in order to suppress the reflected wave. The electromagnetic wave input from each power supply port 434 is equally divided into the central wall 436 and supplied to the two radiation waveguides 437. When the slot plate 411 and the waveguide plate 412 are bonded, a plurality of slots 421 are formed on the tube wall of each radiation waveguide, and a one-dimensional array antenna as shown in FIG. 5 is obtained.
[0024]
  Because of this structure, the number of radiation waveguides constituting the conventional two-dimensional slot array antenna is always a multiple of four. If the desired radiation characteristics and the frequency to be used are determined, the approximate number of radiation waveguides and the number of slots on each radiation waveguide wall are also determined, so that the overall size of the antenna is also substantially determined.
[0025]
  FIG. 9 is a three-dimensional view of the slot array antenna after the slot plate and the waveguide plate are bonded together. Here, the mode of the electromagnetic wave in the radiation waveguide is TE._TenIn the mode, the magnetic field direction is the length direction of the slot 421, and the electric field direction is the width direction of the slot 421.
[0026]
  In this figure, reference numeral 431 denotes a power supply port for the entire antenna, and reference numeral 421 denotes a slot element. Reference numeral 51 denotes the magnetic field direction of the entire antenna, and 52 denotes the electric field direction of the entire antenna. Since all the slots 421 are arranged in the same direction, the electric field direction near the antenna surface is substantially the same as the electric field direction 52 except for the edge of the antenna. Therefore, 52 can be said to be the polarization direction of the antenna.
[0027]
[Non-Patent Document 1]
  Kimura, Hirokawa, Ando: "Prototype characteristics of 76.5 GHz low sidelobe single layer waveguide slot array", 2000 IEICE General Conference, B-1-130, March 2000
[0028]
[Problems to be solved by the invention]
  When designing such a slot array antenna, it is common to have a certain bandwidth at the center frequency. In other words, if the frequency actually used with respect to the set center frequency is within a range that deviates from the center frequency, the radiation directivity, impedance characteristics, reflection characteristics, and the like of the antenna do not deteriorate. The width of the frequency at which the use frequency can be shifted with respect to the center frequency is called a bandwidth. In general, the wider the bandwidth of this frequency, the higher the evaluation of the antenna, but the bandwidth cannot be easily expanded.
[0029]
  However, the bandwidth can be expanded to some extent by providing a tilt angle to the radiation directivity main beam of the slot array antenna. That is, the antenna may be designed so that the radiation directivity main beam that should be perpendicular to the slot plate of the antenna is inclined several degrees from the direction perpendicular to the slot plate in the length direction of the slot.
[0030]
  FIG. 10 is an explanatory diagram of the tilt angle of the radiation directivity main beam of the slot array antenna. Here, although shown using a part of one radiation waveguide, the actual radiation directivity is the radiation directivity of the whole antenna.
[0031]
  FIG. 10A shows a radiation directivity having no tilt angle or a tilt angle of “zero”, and the center interval between adjacent slots is equal to the half wavelength 0.5λg of the wavelength λg in the radiation waveguide. Here, 61 is a vertical axis of the slot plate, 62 is a main beam of radiation directivity, and 63 is a feeding port of the radiation waveguide. Since the tilt angle of the main beam is “zero”, it can be seen that the main beam is perpendicular to the slot plate.
[0032]
  In FIG. 10B, the tilt angle θ₁Is inclined toward the feeding port 63 side of the radiating waveguide, so that the center interval L between adjacent slots is₁Is smaller than 0.5λg. Here, the radiation directivity main beam 62 is θ with respect to the vertical axis 61 of the slot plate.₁It turns out that it inclines to the electric power feeding port 63 side.
[0033]
  In FIG. 10C, the tilt angle θ₂Is inclined to the opposite side of the feeding port of the radiation waveguide, so that the center interval L between adjacent slots is₂Becomes larger than 0.5λg. Here, the main beam is θ relative to the vertical direction of the slot plate.₂It can be seen that it tilts to the opposite side of the feeding port.
[0034]
  Here, the interval adjustment between the slots is performed in order to suppress impedance mismatching in each radiation waveguide caused by the tilt angle. The tilt angle is determined according to a certain rule, and the center interval between adjacent slots is calculated based on the tilt angle value.
[0035]
  FIG. 11 is a cross-sectional view of a conventional slot array antenna in which impedance mismatching is suppressed, and FIG. 11A is a cross-sectional view along the axial direction of the radiation waveguide.
[0036]
  In this figure, 711 is a waveguide plate, 712 is a feeding port side, 713 is a slot plate, 714 is the radiation directivity of the antenna, 715 is an arrow indicating the front direction of the antenna, and θ is the tilt angle of the radiation directivity main beam. It is. When the tilt angle θ is zero degrees, the radiation directivity main beam of the antenna is directed in the front direction of the antenna.
[0037]
  FIG. 11B is a cross-sectional view along the cross-sectional direction of the radiation waveguide. In this figure, 721 is a cross-section of the radiation waveguide.
[0038]
  As shown in FIG. 11A, when the tilt angle θ is generated in the radiation directivity main beam, when the slot array antenna is used for transmission or reception, the radiation directivity main beam is directed toward the target to transmit / receive electromagnetic waves. However, since the slot plate 713 is not perpendicular to the transmission / reception direction, when an antenna is mounted on the transmission / reception apparatus, a considerable wasteful space is generated, and adjustment of the main beam direction of the antenna takes time and the size and cost of the communication apparatus. Adversely affect.
[0039]
  On the other hand, the slot array antenna having such a structure may cause dust and water vapor and other foreign substances to enter from the slot of the slot plate 713 into the internal waveguide, which may deteriorate the antenna characteristics.
[0040]
  In order to prevent this, conventionally, a lid called a radome is generally provided on the entire antenna or a side surface of the slot.
[0041]
  FIG. 12 shows a sectional view of a conventional slot array antenna having a radome.
[0042]
  FIG. 12A is a sectional view along the axial direction of the radiating waveguide. In this figure, 811 is the waveguide plate of the antenna, 812 is the slot plate, 813 is the dielectric radome, and 814 is the radome. It is a screw for fixing.
[0043]
  FIG. 12B is a cross-sectional view along the cross-sectional direction of the radiation waveguide. In this figure, 821 is a cross-section of the radiation waveguide.
[0044]
  When designing the radome 813, in order to prevent the radome 813 from adversely affecting the characteristics of the antenna, the dielectric constant of the dielectric constituting the radome 813 should be made as small as possible (for example, 3 or less), and the thickness of the radome surface facing the slot Is required to be as thin as possible (for example, 1/5 or less of the center wavelength), and the radome surface to be as smooth as possible.
[0045]
  Therefore, in addition to the design of the antenna body, attention must be paid to the design of the radome 813 for protecting the antenna, resulting in high costs.
[0046]
  In view of the above situation, the present invention integrates the slot plate and the radome, and further reduces the number of parts and makes it possible to provide the radome with the function of correcting the tilt angle of the radiation directivity main beam of the antenna. An object is to provide a small and low-priced slot array antenna which is simplified and lightened.
[0047]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides
  [1]In slot array antennas,At the center frequency of wavelength λ, the radiation-directed main beam has a tilt angle θ, and a slot plate having slot elements provided on the radiation surface has a surface in the same direction as the tilt angle θ of the radiation-directed main beam. A dielectric plate having an inclination angle α and a conductive plate having a thickness of approximately λ / 10 or less are bonded together on one side of the dielectric plate, and the conductive plate has a predetermined size and shape at a predetermined position. And a substrate in which a plurality of slot elements that function as unit slot antennas are formed by removing the conductor from the pattern, and the refractive index n of the dielectric plate is √ (1 + sin) at the center frequency of use.²θ), and the value of the inclination angle α of the dielectric plate isThe tilt angle θ can be canceled by refraction of the radiation-directed main beam on the dielectric.
[0048]
[Expression 2]

The slot plate is cut into a predetermined size and shape, an alignment hole is provided if necessary, the conductor plate side and the waveguide plate face each other, and alignment is performed using an alignment means. And then electrically connecting using conductive fixing means, the tilt angle θ of the radiation-directed main beam is corrected to approximately zero degrees by refraction by the dielectric plate having the surface inclination angle α. Thus, the radiation directional main beam is not tilted and is perpendicular to the waveguide plate, and the dielectric plate also serves as a radome by being configured so that the dielectric plate faces outward. It is characterized by that.
[0049]
  [2] In the slot array antenna according to [1], after the dielectric plate and the conductor plate constituting the slot plate are independently processed, the conductor plate is placed on the surface of the waveguide plate at a predetermined position. And aligning using a positioning member, fixing using a conductive fixing means and simultaneously electrically connecting, and placing the dielectric plate on a predetermined position thereon, fixing means It is characterized by using and fixing.
[0050]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described in detail.
[0051]
  In general, the reversibility theorem holds for all antennas, so the transmission characteristics and reception characteristics are exactly the same, so the explanation below is for all transmissions unless otherwise noted. The description is omitted because it is similar.
[0052]
  FIG. 1 is a block diagram of a slot array antenna according to an embodiment of the present invention. FIG. 1 (a) is a sectional view along the axis of the radiation waveguide, and FIG. 1 (b) is a diagram of the radiation waveguide. It is sectional drawing of the direction to cross. FIG. 2 is a diagram showing the relationship between the tilt angle θ of the main beam of the slot array antenna and the tilt angle α of the slot plate dielectric portion.
[0053]
  If the conventional slot plate is used, the tilt angle θ is not zero, so that the main beam of radiation directivity is from the vertical direction of the waveguide plate along the waveguide axis as shown in FIG. Although it inclines to the opposite side, here, the case where it inclines to the opposite side of a power feeding port as shown in FIG.
[0054]
  FIG. 1A is a cross-sectional view along the radiation waveguide axis. Here, 1 is a conventional waveguide plate, 2 is a feeding port side, 3 is a conductor portion (conductor plate) of the slot plate, 4 is a dielectric portion (dielectric plate) of the slot plate, and 5 is a radiation direction of the antenna. 6 is an arrow indicating the front direction of the antenna.
[0055]
  In this embodiment, the conductor portion 3 of the slot plate is thin, for example, made of copper foil having a thickness of 0.1 mm or less, and is bonded to one surface of the dielectric portion 4 of the slot plate. The conductor portion 3 is processed with a slot element at a predetermined position by an etching technique or the like. The dimensions and positions of the waveguide plate 1 and the slot element are designed so that the frequency bandwidth of the entire antenna is wide as in the conventional case, so that the tilt angle θ of the radiation directivity main beam is not zero degrees. . In order to correct the tilt angle θ to approximately zero degrees, that is, to make the radiation-directed main beam perpendicular to the waveguide plate 1, a method is adopted in which the dielectric portion 4 has an inclination angle.
[0056]
  The dielectric portion 4 is made of a low-loss dielectric material in the frequency band of the slot array antenna, that is, allows the electromagnetic wave to pass through without being absorbed. In other words, it is an extremely transparent material for electromagnetic waves. The dielectric material has a dielectric constant ε, but reflects or refracts incident electromagnetic waves, which is the same as in the case of light rays and transparent glass.
[0057]
  Therefore, it is well known that many laws handled in optics can be applied to the electromagnetic wave and the dielectric 4 as they are. For example, the dielectric constant of the dielectric part 4 is ε and the relative dielectric constant is ε_rIf so, the refractive index n is approximately ε._rIs equal to the square root of That is,
[0058]
[Equation 3]

  In the present invention, in order to correct the radiation directivity main beam tilt angle, it is important to use the refraction phenomenon of the electromagnetic wave by the dielectric material.
[0059]
  In order to provide the dielectric part 4 of the embodiment of the present invention with a function of correcting the tilt angle θ of the main beam inclined to the opposite side of the power supply port, as shown in FIG. It is to have a tilt angle on the side. That is, one surface of the dielectric portion 4 is a flat surface and is bonded to the conductor portion 2 to which the slot element is applied, but the other surface is not parallel to the surface bonded to the conductor portion 2 and has an inclination angle. α is formed, and the dielectric is exposed.
[0060]
  In order for the tilt angle θ to be corrected to approximately zero degrees by refraction in the process of passing a radiation-directed beam having a tilt angle θ that is not zero degrees through the dielectric part 4, the tilt angle α is expressed as follows: Given:
[0061]
[Expression 4]

  As is clear from the equation (2), if the tilt angle θ of the main beam and the refractive index n of the dielectric portion are determined, the tilt angle α of the dielectric portion can be calculated. The value of the tilt angle α is unambiguous. The following conditions must be considered in order to be determined. That is, since the tilt angle θ is usually a positive minute angle within a few degrees, it is desirable to set the minimum positive value as the tilt angle α from the solution of the equation (2).
[0062]
  FIG. 2 is a graph of the formula (2), in which the refractive index n of the dielectric portion is changed from 1.4 to 2.0. As is apparent from the graph, as the value of n increases, even a slight change in the inclination angle α has a great effect on θ. Therefore, when processing the dielectric slope, the dielectric constant ε of the dielectric material_rOr, the higher the refractive index n, the higher the processing accuracy of the inclination angle α is required. Practically, the value of n is desirably 2 or less.
[0063]
  Further, in order to make the value of the tilt angle α a positive minute angle within a few degrees like the tilt angle θ, the refractive index n needs to satisfy the formula (3).
[0064]
[Equation 5]

  The refractive index n of a conventional dielectric easily satisfies the formula (3). For example, even if a low dielectric constant material such as Teflon (registered trademark) is used, the relative dielectric constant ε_rIs approximately 2.7, and when converted to a refractive index, n is 1.64, so that the expression (3) is satisfied.
[0065]
  On the other hand, radiation directivity beamTheWhen tilted toward the power supply port side 2, the upper surface of the dielectric portion 4 that is not bonded to the conductor 3 is also tilted toward the power supply port side 2, and the tilt angle α is also expressed by the equation (2). Calculated from That is, if the upper surface of the dielectric portion 4 is inclined at an inclination angle α toward the side on which the radiation directivity main beam is inclined, the non-zero tilt angle θ can be corrected to substantially zero degrees.
[0066]
  FIG. 1B is a cross-sectional view of an antenna according to an embodiment of the present invention including a cross section of the radiation waveguide, and 7 is a cross section of the radiation waveguide.
[0067]
  The processing of the slot plate of the present embodiment is performed as follows.
[0068]
  First, since it is necessary to obtain constants necessary for the production of the slot plate, the calculation is made from already determined values.
[0069]
  When the waveguide plate 1 used in this example is combined with the conductor portion 3 of the slot plate made of copper foil having a thickness of 0.018 mm to obtain a slot array antenna, the main beam tilt of the radiation directivity of the entire antenna is obtained. The angle θ is designed to be 2.8 °.
[0070]
  Further, since the material used for the dielectric portion 4 of the slot plate is Teflon (registered trademark) having a relative dielectric constant of about 2.7, the refractive index n is 1.64. By substituting these values of θ and n into the equation (2), the inclination angle α of the dielectric portion 4 of the slot plate becomes about 4.3 °. In FIG. 2, reference numeral 8 denotes a relational position between the tilt angle θ and the tilt angle α in the embodiment of the present invention.
[0071]
  On the other hand, the total length L in the waveguide axis direction of the waveguide plate is 70.0 mm, and the thinnest portion h of the dielectric portion 4 is h.₀Is 0.8 mm, the thickest portion h of the dielectric portion 4 is 6.0 mm when calculated using the equation (4).
[0072]
    h = h₀+ L × tanα (4)
  Therefore, the thickness of the Teflon (registered trademark) substrate used for the dielectric portion 4 of the slot plate is preferably 6.0 mm or more, but in this embodiment, a Teflon (registered trademark) substrate having a thickness of 6.0 mm is used. To do.
[0073]
  A copper foil having a thickness of 0.018 mm as a conductor plate 3 is attached to one side of the Teflon (registered trademark) substrate, and then a predetermined dimension (0.24 mm × 1.85 mm) and a shape (a semicircular rectangle on both ends) is formed. At this time, the other surface of the Teflon (registered trademark) substrate is exposed, and the Teflon (registered trademark) is obtained so that the inclination angle α (= 4.3 °) is obtained as shown in FIG. ) The substrate exposed surface (surface not bonded to the conductor 3) is cut obliquely. As a result, the thickness of the Teflon substrate at the power supply port 2 side end is h (= 6.0 mm), and the thickness of the opposite side end of the power supply port 2 is h.₀(= 0.8 mm). In consideration of assembly, it is necessary to cut the peripheral dimensions on the slot side to the same dimensions as the waveguide plate 1. Then, after the surface treatment is performed so that the surface of the cut Teflon (registered trademark) substrate is smooth, the entire slot plate is washed to complete the processing operation, but the plating operation is performed to prevent corrosion of the copper foil. Etc. may be applied.
[0074]
  The next task is to mount the slot plate on the waveguide plate. In order to make the waveguide plate into a row of waveguides having slot elements, the copper foil side of the processed slot plate is directly electrically connected to the waveguide plate at a predetermined position, and conductive. The slot array antenna according to the embodiment of the present invention is completed by fixing with the adhesive adhesive or the screw.
[0075]
  The operation of the slot array antenna of the present invention will be described below.
[0076]
  The difference between the operation of the slot array antenna of the present invention and the operation of the conventional slot array antenna is that the radiated electromagnetic wave must pass through the radiation-directed main beam tilt angle correcting dielectric plate. In other words, electromagnetic waves radiated from the slot must pass through the Teflon (registered trademark) plate, and strictly speaking, the influence of absorption and reflection by the Teflon (registered trademark) plate is inevitable.
[0077]
  However, in the embodiment of the present invention, Teflon (registered trademark), which is a dielectric material having a relative dielectric constant of approximately 2, is employed, and its thickness is thin even when viewed from an electromagnetic wave in the 70 GHz band. The adverse effect on the properties of the (trademark) board is considered to be negligible. Therefore, the description of the operation is exactly the same as that of the conventional slot array antenna.
[0078]
  First, the operation of the slot array antenna body will be described with reference to FIG.
[0079]
  The appearance of a conventional slot array antenna is as shown in FIG. When electromagnetic waves are fed from the feeding port 431, the electromagnetic waves pass through the feeding circuit and are fed to the respective radiation waveguides, and further radiated from the slot elements 421 of the slot plate. In the process of passing through the power feeding circuit and the radiation waveguide inside the antenna, the power of the electromagnetic wave fed to each slot element is adjusted so as to follow a certain distribution, for example, the Taylor distribution or the uniform distribution. The radiated power is concentrated on the main beam, and high radiation efficiency is obtained. The higher the radiation efficiency, the farther the radiated electromagnetic wave reaches.
[0080]
  Next, the refraction of the electromagnetic wave immediately after being emitted from the slot in the Teflon (registered trademark) plate will be described with reference to FIG. Since FIG. 3 is a partially enlarged view of FIG. 1A, the names used there are also used as they are.
[0081]
  FIG. 3 is an explanatory view of the refraction of the radiation-directed main beam by the slot plate dielectric portion of the slot array antenna according to the embodiment of the present invention.
[0082]
  In this figure, 11 is a waveguide plate, 12 is a conductor portion (conductor plate) of the slot plate, 13 is a dielectric portion (dielectric plate) of the slot plate, and 14 is a radiation-directed main beam (radiated electromagnetic wave). .
[0083]
  In FIG. 3, point A is a point on the surface of the slot plate copper foil P1, and 14 represents the radiation-directed main beam. Since the antenna can generally be regarded as one point when viewed from a sufficiently long distance, the starting point of the radiation directivity main beam 14 is considered to be the point A, and although the radiation directivity main beam 14 is a radiation electromagnetic wave, It can be regarded as a ray.
[0084]
  In this case, since the tilt angle of the radiation directivity main beam 14 is θ, the radiation directivity main beam 14 becomes an angle θ formed with the perpendicular of P1. The main beam 14 is refracted by the dielectric portion 13 at point A, and its refraction angle is θ₁It is. At the center frequency, the dielectric constant of the dielectric portion 13 is ε_rTherefore, the refractive index n is as shown in Equation (1). Also, tilt angle θ and refraction angle θ₁Then, it is connected by Snell's law as shown in equation (5):
    sin θ = n × sin θ₁                            (5)
  The refracted radiated electromagnetic wave 14 passes through the dielectric portion 13 and radiates from the point B to the free space when it reaches the surface P2 on the other side. At point B, 14 is refracted and propagates in a direction perpendicular to the slot plate copper foil surface P1. The refraction angle at that time is α. According to the geometrical theorem, the refraction angle α is equal to the tilt angle of the dielectric portion 13.
[0085]
  In addition, the radiated electromagnetic wave 14 originally has a tilt angle θ, but the fact that the propagation direction becomes perpendicular to P1 due to the two refractions means that the tilt angle θ is corrected to “zero degree”. Under these conditions, rearranging the relational expressions gives:
    n × sin (α−θ₁) = Sin α (6)
  When α is calculated from Equation (5) and Equation (6), Equation (2) is obtained.
[0086]
  In this way, the tilt angle θ of the radiation directivity main beam is corrected to “zero degree” by refraction of the dielectric portion 13 of the slot plate, but the waveguide plate 11 of the antenna and the slot plate 12 provided with the slot elements. Since the shape and dimensions of the copper foil remain as they are, the frequency band of the antenna does not change and remains a wide band.
[0087]
  The dielectric portion of the slot plate of the present invention corrects the radiation directivity main beam tilt angle and at the same time serves as the radome of the slot array antenna.
[0088]
  Moreover, this invention has the following utilization forms.
[0089]
  The slot array antenna of the present invention is suitable for millimeter wave communication, and can be used as an ETC or ITS antenna in recent years, as is the case with conventional slot array antennas.
[0090]
  Further, if the number of slot elements is increased, the radiation gain is further increased and the main beam width is also sharpened. Therefore, it can be used for a system that requires a high gain antenna such as a parabolic antenna. For example, a telephone communication base station relay antenna, a television base station relay antenna, a satellite communication antenna, a radio astronomy radio telescope antenna, and the like can be given.
[0091]
  Furthermore, the present invention can include the following modified embodiments.
[0092]
  In the embodiment of the present invention, as shown in FIG. 11, the arrangement of the waveguide plate and the slot element in the case where the radiation directivity main beam is inclined to the opposite side of the feeding port is adopted, and the improvement measures have been described. In the case where the directional main beam is tilted toward the feeding port side, the slot plate is designed and processed in the same manner by calculating the tilt angle α of the dielectric portion using Equation (2). Like the radiation directivity main beam, it is inclined toward the feeding port side, so such a modification can be considered.
[0093]
  In addition, the slot plate of the embodiment of the present invention was manufactured by laminating a copper foil on one side of a dielectric substrate and forming a slot element on the copper foil by an etching technique, but a conductor plate having a certain thickness, For example, when a slot element is formed on a stainless steel plate having a thickness of 0.1 mm or more, an aluminum plate having a thickness of 0.2 mm or more, or a copper plate, a dielectric plate having an inclination angle α is processed and then a conductive adhesive or normal bonding is performed. A modification in which the antenna is completed by fixing it on the waveguide plate using an agent or a screw is also conceivable.
[0094]
  In addition to this, for example, if a slot plate is made in the same manner as the embodiment of the present invention using a commercially available printed board having a dielectric having a predetermined thickness, the antenna can be further reduced in price. Examples are also possible.
[0095]
  In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
[0096]
【The invention's effect】
  As described above in detail, according to the present invention, the following effects can be obtained by using the slot plate with radome instead of the conventional slot plate.
[0097]
  (1) Conventionally, since the radome necessary for protecting the surface of the slot plate of the slot array antenna is not required, the number of parts is reduced, and the price of the antenna is promoted.
[0098]
  (2) Since the slot plate and the dielectric plate are integrated, the antenna is made compact, the miniaturization is promoted, and the mounting is simplified, so that the cost is further reduced.
[0099]
  (3) Although the conventional slot plate differs depending on the material, it cannot maintain a precise dimension unless it has a certain thickness (for example, in the case of aluminum, it is thin, up to 0.2 mm, in the case of stainless steel) Therefore, when the slot is processed, it is difficult to obtain a dimension as calculated. However, as in the embodiment of the present invention, since the conductor plate serving as the slot plate is bonded to the dielectric plate, the conductor plate can be sufficiently used even if it is as thin as 0.018 mm. The thinner the slot plate is, the closer the slot shape and dimensions are to the calculated values, so that design and trial production can be performed easily, and improvement in antenna characteristics can be expected.
[0100]
  (4) Since the tilt angle α of the radiation-directed main beam is corrected by giving the tilt angle α to the dielectric plate, not only the useless space is eliminated as in the prior art, but also the antenna main Adjustment of the beam direction is also unnecessary, contributing to the miniaturization and cost reduction of communication devices.
[0101]
  (5) Since the slot plate of the present invention can be used even with a commercially available printed board, it is sufficiently inexpensive as compared with a conventional slot plate alone.
[0102]
  Therefore, it can be said that the present invention greatly contributes to high performance, downsizing, and low price of the slot array antenna.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a slot array antenna showing an embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between a tilt angle θ of a main beam of a slot array antenna according to an embodiment of the present invention and a tilt angle α of a slot plate dielectric portion thereof.
FIG. 3 is an explanatory diagram of the refraction of the radiation-directed main beam by the slot plate dielectric part of the slot array antenna showing the embodiment of the present invention.
FIG. 4 is a basic configuration diagram of a conventional two-dimensional array antenna.
FIG. 5 is a diagram showing a configuration example of a slot array antenna using a single rectangular waveguide.
FIG. 6 is an exploded perspective view showing a conventional two-dimensional slot array antenna.
FIG. 7 is a plan view of a slot plate of a conventional two-dimensional slot array antenna.
FIG. 8 is a plan view of a waveguide plate of a conventional slot array antenna.
FIG. 9 is a three-dimensional view of a slot array antenna after bonding a conventional slot plate and waveguide plate.
FIG. 10 is an explanatory diagram of the tilt angle of the radiation directivity main beam of the slot array antenna.
FIG. 11 is a cross-sectional view of a conventional slot array antenna in which impedance mismatch is suppressed.
FIG. 12 is a cross-sectional view of a conventional slot array antenna having a radome.
[Explanation of symbols]
  1,11 Waveguide plate
  2, Power supply side
  3,12 Slot plate conductor (conductor plate)
  4,13 Slot plate dielectric (dielectric plate)
  5 Antenna radiation pattern
  6 Arrow indicating the front direction of the antenna
  7 Cross section of radiation waveguide
  8 Relationship between tilt angle θ and tilt angle α used in the example
  14 Radiation-directed main beam (radiated electromagnetic wave)

Claims (2)

At the center frequency of wavelength λ, the radiation-directed main beam has a tilt angle θ, and a slot plate having slot elements provided on the radiation surface has a surface in the same direction as the tilt angle θ of the radiation-directed main beam. A dielectric plate having an inclination angle α and a conductive plate having a thickness of approximately λ / 10 or less are bonded together on one side of the dielectric plate, and the conductive plate has a predetermined size and shape at a predetermined position. And a substrate in which a plurality of slot elements that function as unit slot antennas are formed by removing the conductor from the pattern, and the refractive index n of the dielectric plate is √ (1 + sin ^{2) at the} center frequency of use. The tilt angle α of the dielectric plate is larger than θ) , and the tilt angle θ can be canceled by the refraction of the radiation-directed main beam on the dielectric.

The slot plate is cut into a predetermined size and shape, an alignment hole is provided if necessary, the conductor plate side and the waveguide plate face each other, and alignment is performed using an alignment means. And then electrically connecting using conductive fixing means, the tilt angle θ of the radiation-directed main beam is corrected to approximately zero degrees by refraction by the dielectric plate having the surface inclination angle α. Thus, the radiation directional main beam is not tilted and is perpendicular to the waveguide plate, and the dielectric plate also serves as a radome by being configured so that the dielectric plate faces outward. A slot array antenna characterized by that.   The slot array antenna according to claim 1, wherein after the dielectric plate and the conductor plate constituting the slot plate are independently processed, the conductor plate is disposed at a predetermined position on the surface of the waveguide plate, After aligning using an alignment member, fixing using a conductive fixing means, and simultaneously connecting them, the dielectric plate is placed on a predetermined position, and fixed using fixing means. A slot array antenna characterized by that.

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