JP3974766B2 - Surface acoustic wave device - Google Patents

Description

である（Ｖｉｋｔｏｒｏｖ，Ｒａｙｌｅｉｇｈ ａｎｄ Ｌａｍｂ Ｗａｖｅｓ）。式（３）はレイリー波やラム波について求められたものであるが弾性表面波一般にも適用できる。なおここで、Ｃは定数、Ｃ_Ｒはレイリー波速度、ｔは時間である。ｍは
ｍ＝円周の長さ／弾性表面波の波長
であり、波数パラメータと呼ぶ。
【００４２】
角度θは式（２）から求められる。点Ｅから見こむ角度が２θ_Ａの円弧状音源による点Ｑの音場は、式（３）をθ_oについて−θ_Ａからθ_Ａまで積分することにより得られる。音場分布は点Ｑの迎角θ_１を変化させて計算することで求められる。
【００４３】
図３には点ＰがＸＺ面上にあるφ_０＝０の場合について式（３）を使用して求めた弾性表面波が球面上を伝搬する４つの状態が示されている。
【００４４】
図３（Ａ）、図３（Ｂ）及び図３（Ｃ）は、波数パラメータｍ＝６００の場合の音場（粒子変位の絶対値の角度θ_１依存性）を調べた結果である。図の各々において、最も下のプロットは球面上の弾性表面波の伝搬を表す角度（伝搬角）φ_１が０°の場合の音場であり、上に向かって１５°づつ増加した場合の音場が順にプロットしてある。
【００４５】
図３（Ａ）は、開口半角θ_Ａ＝３０°の場合である。この場合には、図３（Ａ）から明らかなように、弾性表面波の伝搬状態は集束ビーム形状である。即ち、伝搬角φ_１が増加するにつれて音場の幅が減少しφ_１＝９０°で最小になった後は再び幅が増加し対極点１８０°で音源上と同じ分布が再現される。以降は１８０°毎に上記同じ変化が繰り返され、何周回っても同じ変化が繰り返される。これは回折による波の拡散が全く無い球面に独特な現象である。この場合、開口半角θ_Ａ＝３０°よりも音場が広がることがなく、θ_１＜θ_Ａの帯状部分に弾性表面波のエネルギーが閉じ込められている。この場合には球面のθ_１＞θ_Ａの部分に他の物体を接触させても音場に擾乱は生じない。
【００４６】
図３（Ｃ）は、開口半角θ_Ａ＝１°の場合である。この場合には、図３（Ｃ）から明らかなように、弾性表面波の伝搬状態は点音源の場合と類似した発散ビーム形状である。即ち、伝搬角φ_１が増加するにつれて音場の幅も増加しφ_１＝９０°で最大になった後は再び幅が減少し対極点１８０°で音源上と同じ分布が再現される。この場合は、図３（Ａ）を参照しながら上述した集束ビームの場合とは異なり、θ_１＜θ_Ａの帯状部分に弾性表面波のエネルギーが閉じ込められることが無く、φ_１＝９０°では球の表面全体に広がってしまう。この場合には、球面のφ_１＝９０°かつθ_１＞θ_Ａの部分に他の物体を接触させると音場に擾乱が生じる。
【００４７】
図３（Ｂ）は、開口半角θ_Ａ＝３．５°の場合である。この場合には、図３（Ｂ）から明らかなように、弾性表面波の伝搬状態は伝搬角φ_１が増加しても音場の幅は殆ど変化しないコリメートビーム形状である。即ち、θ_１＝θ_Ａの帯状部分に弾性表面波のエネルギーが閉じ込められている。これは無限媒体中のベッセルビームと同様な特性である。そしてコリメートビームが得られる開口半角θ_Ａをコリメート角θ_ｃｏｌと呼ぶ。
【００４８】
図３（Ａ）、図３（Ｂ）及び図３（Ｃ）から明らかなように、開口半角θ_Ａがコリメート角θ_ｃｏｌに略等しい時、最も幅の狭い帯状部分に弾性表面波のエネルギーが閉じ込められている
さらに、波数パラメータｍを変化させて上述したのと同様の数値解析を行った結果、波数パラメータｍによりコリメート角θ_ｃｏｌが変化することが分かった。図３（Ｄ）は、波数パラメータｍが３００の場合に弾性表面波の伝搬状態がコリメートビーム形状になるのは、開口半角θ_Ａが略４．５°であることを示しており、この場合のコリメート角θ_ｃｏｌは約４．５°になる。
【００４９】
以下には、波数パラメータｍが変化した場合のコリメート角θ_ｃｏｌの値を示す。
【００５０】

なおこれは、数値計算による近似値である。このように、コリメート角θ_ｃｏｌは波数パラメータｍから式（３）を用いて求められる。
【００５１】
再び図１を参照して本実施の形態の弾性表面波素子を説明する。櫛形電極１２３から弾性表面波が出力されると、上述のように円環状表面１１１に沿って伝搬する。説明の便宜上、円環状表面１１１の幅を櫛形電極１２３の重なり幅と等しく取る。櫛形電極１２３の重なり幅は、コリメート角θ_ｃｏｌにより規定される弾性表面波の発生源の幅以上である。より好ましくは重なり幅はコリメート角θ_ｃｏｌにより規定される幅に等しい。弾性表面波は、上記数値計算の結果から円環状表面１１１の幅を超えて拡散することなく、円環状表面１１１に沿って伝搬する。この伝搬の様子は図３（Ａ）及び図３（Ｂ）に対応する。コリメート角θ_ｃｏｌを決定する波数パラメータｍの代表的な値は、１００〜８００であるが、本発明の波数パラメータｍはこの値に限定されない。
【００５２】
上記数値計算では、弾性表面波の波長及び位相速度は弾性表面波が伝搬する球面の全ての場所で一定であるとして説明した。しかしながら、結晶である水晶で形成された球状の基材では、ある振動数をもった弾性表面波の波長及び位相速度は結晶方位に従って一般に異なる。よって、波数パラメータｍも球面上で一定ではないが、近似的に一定であるとする。この一定の波数パラメータｍを求めるために、弾性表面波励起手段により弾性表面波が励起される基材の部分を伝搬している弾性表面波の波長を用いる。即ち、櫛形電極１２３が設けられた基材１１０の部分の波長を用いる。さらに、それぞれの電極片の位置の基材１１０上の波長に合わせて櫛形電極１２３の電極パターンの形状を設定することが望ましい。
【００５３】
弾性表面波が伝搬する円環状表面１１１は、上述したように基材１１０を形成しいている単結晶の結晶方位で決まる所定の経路に沿って形成されている。この経路は三方晶系に属する水晶については発明者らの実験によって確認されている。この経路は水晶のＺ軸に関係している。水晶の結晶軸は図４に示されている。
【００５４】
図５はこの経路を示す図である。説明の便宜上、Ｚ軸は球状の基材１１０の中心を通るものとする。結晶方位で決まる所定の経路は４つの経路ａ，ｂ１，ｂ２，ｂ３を含んでいる。経路ａは基材１１０の表面である球面と、この球面の中心を通り、Ｚ軸と直交する平面との交線である。経路ｂ１，ｂ２，ｂ３はそれぞれ基材１１０の表面である球面と、この球面の中心を通り、Ｚ軸と平行な３つの平面との交線である。経路ｂ１を含む平面は経路ｂ２，ｂ３を含む平面とそれぞれ６０°，−６０°の角度をなしている。Ｚ軸を球状の基材１１０の地軸と考えると、経路ａは赤道であり、経路ｂ１，ｂ２，ｂ３は６０°間隔で並んでいる６つの経線で構成される。
【００５５】
本実施の形態では、弾性表面波は図１に示されているように経路ａに沿って伝搬する。即ち、円環状表面１１１は経路ａに沿って形成されている。しかしながら、本発明はこれに限定されるものではない。経路ａ，ｂ１，ｂ２，ｂ３の内の少なくとも２つの経路に沿って弾性表面波を伝搬させてもよい。例えば経路ａと経路ｂ１に沿って伝搬させる場合、経路ａ，ｂ１に対向させて弾性表面波励起手段をそれぞれ設ける。また、経路ａと経路ｂ１が交差する基材１１０の部分に弾性表面波を散乱する散乱体又は弾性表面波を反射する反射体を設け、経路ａを伝搬する弾性表面波を経路ｂ１に分岐してもよい。経路ａ上の弾性表面波の乱れが無視できる程度の散乱体又は反射体を設ければ、経路ａ上で励起され、経路ａを周回する弾性表面波を経路ａの外で検出できる。
【００５６】
櫛形電極１２３をより詳細に説明する。図６は櫛形電極１２３の平面図である。櫛形電極１２３は１対の櫛形パターン１２３ａ，１２３ｂを備えている。櫛形パターン１２３ａは弾性表面波が伝搬する方向に配列している複数の電極片ｌ１，ｌ２，ｌ３，…を有している。後述するように、弾性表面波が伝搬する方向は図６のように基材１１０の経路ａに一致させられる。櫛形パターン１２３ｂは電極片ｌ１，ｌ２，ｌ３，…と互い違いに配列している複数の電極片ｒ１，ｒ２，ｒ３，…を有している。隣り合う電極（例えば電極片ｒ１と電極片ｌ１、又は電極片ｌ１と電極片ｒ２）の間隔は全て等しい。電極片ｌ１，ｌ２，ｌ３，…と電極片ｒ１，ｒ２，ｒ３，…とは経路ａに対して垂直に延びている。即ち、Ｚ軸を基材１１０の地軸とすれば、これらの電極片は経線に沿って延びている。これらの電極片は周期的に並んでいる。即ち、電極片ｌ１，ｒ１を経路ａに沿って移動すれば、電極片ｌ２，ｒ２、電極片ｌ３，ｒ３、…にそれぞれほぼ重なる。電極片ｌ１，ｒ１は周期的に並んだ電極片の単位を形成する。この電極片の単位を弾性表面波が伝搬する方向に並べれば、櫛形電極１２３の１対の櫛形パターン１２３ａ，１２３ｂが形成される。
【００５７】
弾性表面波が伝搬する方向の電極片の単位の長さである電極周期Ｐは一定である。弾性表面波励起手段により励起される弾性表面波の波長は、基材の球面の半径の１／１０以下である。このとき、この波長は基材１１０全体の固有振動ではなく、電極周期Ｐにほぼ等しくなる。但し、上述したように、弾性表面波励起手段により励起される弾性表面波の波長、即ち櫛形電極１２３に対向する基材１１０の部分を伝搬する弾性表面波の波長は、基材１１０のその他の部分の波長と異なる場合がある。
【００５８】
再び図１を参照して説明する。水晶の基材１１０のＺ軸は水平にされている。上述したように、基材１１０は、経路ａに沿って櫛形電極１２３の電極片が並ぶように凹部１２２に対して位置決めされている。
【００５９】
櫛形電極１２３の電極周期は以下のようにして設定される。以下、基材１１０を等方性の材料で形成されていると見なす。水晶の結晶のＹカット面のＸ軸伝搬のレイリー波の位相速度のある値は３１６０ｍ／ｓである。これを弾性表面波の代表的な位相速度と見なす。周波数が１５．１ＭＨｚの弾性表面波が励起される素子を作るときを考える。波数パラメータが１５０の素子を作成しようとする。弾性表面波の波長は３１６０ｍ／ｓ÷１５．１ＭＨｚ＝２０９．３μｍより、０．２０９ｍｍである。従って、電極周期を０．２０９ｍｍに設定する。尚、周囲長が３１．４１５ｍｍであるから半径は５．０ｍｍである。上述したように、弾性表面波の波長は基材１１０の球面の半径の１／１０以下である。
【００６０】
弾性表面波が拡散しないような重なり幅は以下のようにして設定される。１５０である波数パラメータに対応するコリメート角θ_ｃｏｌは、上記数値計算から７．０°である。コリメート角の定義から重なり幅は、

従って、重なり幅を１．２２ｍｍに設定する。
【００６１】
本実施の形態の弾性表面波素子に、信号振幅２０Ｖ、時間幅２ナノ秒にインパルス信号を１ｍｍ秒置きに入力して、その出力信号の観測を２０ＭＨｚのローパスフィルターを通して測定した波形を図７に示す。雑音信号が非常に小さく、１０回まで周回することが確認できた。
【００６２】
次に、櫛形電極の変形例を説明する。図８は本変形例の櫛形パターン１２３ｃ，１２３ｄの平面図を変形した図である。図８では水晶の基材１１０のＺ軸を地軸としたとき、全ての緯線が同じ長さにされている。即ち、地軸に対して垂直に基材１１０を見ると、基材１１０は正方形に見える。
【００６３】
櫛形パターン１２３ｃは経路ａに沿って配列している複数の電極片Ｓ１，ｓ１，Ｓ２，ｓ２，Ｓ３，ｓ３，…を有している。これらの電極片は経線方向に延びている。電極片Ｓ１，ｓ１、電極片Ｓ２，ｓ２、電極片Ｓ３，ｓ３…はそれぞれ組みになっている。これらの電極片は周期的に並んでいる。電極片Ｓ１と電極片Ｓ２の間隔、電極片Ｓ２と電極片Ｓ３の間隔、…は全て等しい。電極片Ｓ１と電極片ｓ１の間隔、電極片Ｓ２と電極片ｓ２の間隔、電極片Ｓ３と電極片ｓ３の間隔、…は全て等しい。電極片Ｓ１，ｓ１を経路ａに沿って移動すれば、電極片Ｓ２，ｓ２、電極片Ｓ３，ｓ３…にそれぞれ重なる。
【００６４】
櫛形パターン１２３ｄは経路ａに沿って配列している複数の電極片Ｔ０，Ｔ１，Ｔ２，Ｔ３，…を有している。これらの電極片は経線方向に延びている。電極片Ｔ１は電極片ｓ１と電極片Ｓ２の間に、電極片Ｔ２は電極片ｓ２と電極片Ｓ３の間に、それぞれ配置されている。Ｔ３以降の電極片Ｔｉ（ｉ＝３，４，５…）も電極片Ｔ１，Ｔ２と同様に電極片ｓｉと電極片Ｓｉ＋１の間に配置されている。電極片Ｔ０は、電極片Ｔ０と電極片Ｔ１との間に電極片Ｓ１，ｓ１が位置するように配置されている。電極片Ｔ０，Ｔ１，Ｔ２，Ｔ３，…の内の隣り合う電極片の間隔は全て等しい。電極片Ｔ０を経路ａに沿って移動すれば、電極片Ｔ１，Ｔ２，Ｔ３，…にそれぞれ重なる。
【００６５】
電極片Ｓ１，ｓ１，Ｔ１、電極片Ｓ２，ｓ２，Ｔ３、電極片Ｓ３，ｓ３，Ｔ３…はそれぞれ組みになっている。上記説明からこれらの電極片の組みは周期的に並んでいることは明らかである。電極片Ｓ１，ｓ１，Ｔ１は周期的に並んだ電極片の単位を形成する。櫛形パターン１２３ｃ，１２３ｄの寸法を説明する。電極周期Ｐは図８に示されているように、
電極周期Ｐ＝（電極片Ｓ１と電極片Ｓ２の間隔）＋（経路ａに沿った方向の電極片Ｓ１の幅）
で表される。電極周期Ｐを用いて櫛形パターン１２３ｃ，１２３ｄの寸法は、
経路ａに沿った方向の電極片Ｓ１の幅＝Ｐ／４
経路ａに沿った方向の電極片Ｔ１の幅＝Ｐ／８
電極片Ｔ１と電極片Ｓ２の間隔＝３Ｐ／１６
となるように設定されている。
【００６６】
櫛形パターン１２３ｃ，１２３ｄを上記のように形成すると、経路ａに沿って一方向（図８の矢印の方向）に弾性表面波を出力することができる。
【００６７】
本実施の形態の櫛形電極１２３及びこれの上記変形例には様々な修正と変形とが可能である。例えば、電極片は基材１１０の経線に沿って延びているが、経線に交差する方向に延びてもよい。図９のような各部が縦方向と横方向に直線的に延びる穴を有する板状のフォトマスクを基台１２１の凹部１２２に対向させてフォトレジストにより櫛形電極を形成する場合、電極片は経線に交差する方向に延びる。このようなフォトマスクは容易に設計することができ、またフォトレジストを容易に行うことができる。
【００６８】
また、隣り合う電極片の間隔（例えば、電極片Ｓ１と電極片ｓ１の間隔、電極片ｓ１と電極片Ｔ１の間隔等）又は、電極片の組みの間隔（電極片Ｔ１と電極片Ｓ２の間隔）、又は電極周期を一定にしなくともよい。上述したように、結晶である水晶で形成された球では、波長及び位相速度は結晶方位に従って一般に異なる。電極片が位置する基材１１０の部分の波長に応じて電極周期等を設定すれば、所望の周波数をもつ弾性表面波を効率よく励起できる。
【００６９】
ところで、従来、基材が平板状であり、広帯域用の弾性表面波素子として、電極片の組みが周期的に並んでいる弾性表面波素子が知られている。このような弾性表面波素子を球状の基材１１０に応用すれば、広い波長域にわたって弾性表面波が励起される。波長と関係しているコリメート角θ_ｃｏｌが櫛形電極の重なり幅以上であるような波長をもつ弾性表面波だけが拡散せずに基材１１０を周回できる。
【００７０】
また、本実施の形態では櫛形電極１２３には高周波電源を有する発信器１２６が接続されているが、本発明はこれに限定されない。例えば、高周波電源１２３の代わりに、高周波の電波を受信するアンテナを櫛形電極１２３に接続してもよい。アンテナに高周波の電波が受信されると、発信器１２６が接続されていた場合と同様に、櫛形電極１２３に電界が発生し、弾性表面波が励起される。
【００７１】
次に、本発明の第２の実施の形態の弾性表面波素子を説明する。本実施の形態の構成の大部分は、基本的に第１の実施の形態の構成の大部分と同じである。本実施の形態において、第１の実施の形態の図１を参照して説明した構成部材と実質的に同一の構成部材は、第１の実施の形態の対応する構成部材を指示していた参照符号と同じ参照符号を付して詳細な説明を省略する。
【００７２】
本実施の形態の構成が第１の実施の形態の構成と異なる点は基材の構成である。本実施の形態の基材には樹脂薄膜が設けられていない。図１０は基台１２１の斜視図である。基台１２１には、櫛形電極１２３が基材と間隔を置いて対向するようにスペーサ２３１，２３２が設けられている。スペーサ２３１，２３２はレジスト樹脂を硬化させて設けられる。スペーサ２３１，２３２は櫛形電極１２３の櫛形パターンが形成されている部分の両側に配置されており、弾性表面波の伝搬に影響を与えないように設けられている。
【００７３】
図１１は基台１２１を図１０のＬ１１−Ｌ１１断面線で切断した断面図であり、スペーサ２３１，２３２に基材２１０が保持されている。Ｌ１１−Ｌ１１断面線は２つのスペーサ２３１，２３２を貫き、櫛形電極１２３の電極片が並んでいる方向に対して直交する方向に延びている。
【００７４】
基材２１０は、等方性の材料であるガラス材料で形成されている球状部材２１２と、これを覆う厚さ１０００Åの金膜２１３と、金膜２１３を覆うＺｎＯのＺ軸配向膜２１４とを有している。図１１では、金膜２１３と配向膜２１４は球状部材２１２の表面から一部取り除かれて示されている。配向膜２１４は圧電性材料である。即ち、基材２１０の一部は圧電性材料で形成されている。
【００７５】
金膜２１３は蒸着などにより形成される。配向膜２１４はＤＣスパッタにより形成される。基材２１０を回転させながらスパッタを行うことで基材２１０を一周する環状の領域に配向膜を形成できる。これを利用して基材２１０の表面の全てにわたって配向膜を形成できる。ＤＣスパッタで用いるガスの濃度やＤＣ高圧電圧の電圧など、また蒸着マスクの作成方法については基本的に公知の技術を利用できる。
【００７６】
櫛形電極１２３により基材２１０に電界が印加されると、圧電効果によりＺｎＯのＺ軸配向膜２１４が振動する。この結果、基材２１０の円環状表面２１１に沿って伝搬する弾性表面波が励起される。円環状表面２１１は櫛形電極１２３の電極片が並んでいる方向に沿ってスペーサ２３１，２３２の間で延びている。円環状表面２１１はスペーサ２３１，２３２から離れている。これにより、弾性表面波は散乱したり反射されたりせずに円環状表面２１１を伝搬できる。尚、円環状表面２１１は、図５を用いて第１の実施の形態で説明した水晶の基材１１０のように、材料の性質に基づく特定の経路に沿っていない。但し、円環状表面２１１は基材２１０の最大円周線に沿って延びている。
【００７７】
本実施の形態では櫛形電極１２３の重なり幅は２ｍｍ、電極周期は３５０μｍである。スペーサ２３１，２３２の高さ、即ち櫛形電極１２３と円環状表面２１１との間隔は第１の実施の形態と同様に１０μｍである。これは電極周期の１／４以下である。
【００７８】
本実施の形態では、櫛形電極１２３の櫛形が形成されている部分の両側に２つのスペーサが設けられているが、本発明はこれに限定されない。例えば両側に２つずつ設けられていてもよい。あるいは、微小な樹脂の粒子を基材２１０と櫛形電極１２３の間に分散させても比較的よいスペーサになり得る。
【００７９】
次に、本発明の第３の実施の形態の弾性表面波素子を説明する。本実施の形態の構成の大部分は、基本的に第２の実施の形態の構成と同じである。本実施の形態において、第２の実施の形態の図１０及び図１１を参照して説明した構成部材と実質的に同一の構成部材は、第２の実施の形態の対応する構成部材を指示していた参照符号と同じ参照符号を付して詳細な説明を省略する。
【００８０】
本実施の形態では、第２の実施の形態の基台１２１の代わりに、基台３２１を用いている。図１３は基台３２１の斜視図である。基台３２１の上面には縦方向に延びている角柱状の電極片ｕ１，ｖ１，ｕ２，ｖ２，ｕ３，ｖ３，ｕ４がこの順に横方向に並んでいる。これらの電極片は櫛形電極を形成している。これらの電極片の上面にわたって、基材２１０の球面の一部沿った形状をもつ凹面が形成されている。電極片ｕ１，ｖ１，ｕ２，ｖ２，ｕ３，ｖ３，ｕ４内の隣り合う電極片はそれぞれ別の電極に接続されている。即ち、電極片ｕ１，ｕ２，ｕ３，ｕ４は電極３３５に、電極片ｖ１，ｖ２，ｖ３は電極３３６にそれぞれ接続されている。これらの電極片と基台３２１とは、ガラスエポキシ材料の切削し、電極片の上面に対応する部分に銅をメッキすることにより形成される。これらの電極片で形成されている櫛形電極の重なり幅と電極周期は第２の実施の形態のものと同じである。電極３３５，３３６は所定の回路を介してインピーダンスマッチング回路１２４（図１参照）に接続されている。電極片ｕ１，ｖ１，ｕ２，ｖ２，ｕ３，ｖ３，ｕ４と電極３３５，３３６は弾性表面波励起手段として用いられている。
【００８１】
基台３２１の上面には基材２１０を保持するための４つの保持部材３３１，３３２，３３３，３３４が設けられている。保持部材３３１，３３２，３３３，３３４に基材２１０が保持されるとき、電極片ｕ１，ｖ１，ｕ２，ｖ２，ｕ３，ｖ３，ｕ４の上面は基材２１０の表面と間隔を置いて対向する。これらの電極片により基材２１０に電界が印加されると、基材２１０の円環状表面２１１に沿って伝搬する弾性表面波が励起される。円環状表面２１１は、第２の実施の形態と同様に、最大円周線に沿って延びている。これらの電極片で形成されている櫛形電極は円環状表面２１１と間隔を置いて対向している。この間隔は第２の実施の形態のものと同じであり、上記電極周期の１／４以下である。保持部材３３１，３３２，３３３，３３４は円環状表面２１１の両側に位置する。
【００８２】
このように弾性表面波素子を構成しても、第２の実施の形態と同様の効果が得られる。
【００８３】
本実施の形態では櫛形電極は７つの電極片ｕ１，ｖ１，ｕ２，ｖ２，ｕ３，ｖ３，ｕ４で形成されているが、本発明はこれに限定されない。電極片の数は２〜６つでもよいし、８以上でもよい。
【００８４】
上記第１から第３の実施の形態には様々な修正と変形とが可能である。例えば、第１の実施の形態の水晶の基材１１０は第２の実施の形態の基台１２１又は第３の実施の形態の基台３２１に保持されてもよい。この場合、第１の実施の形態の基材１１０には樹脂薄膜が形成されない。基材１１０は、基材１１０の経路ａが第１の実施の形態の櫛形電極１２３又は第２の実施の形態の櫛形電極の電極片が並ぶ方向に沿うように、第２の実施の形態の基台１２１又は第３の実施の形態の基台３２１に位置決めされる。
【００８６】
次に、本発明の第１の実施の形態の分析方法を説明する。先ず、少なくとも球面の一部で形成されていて円環状に連続している円環状表面を有している基材を用意する（基材用意工程）。本実施の形態では、圧電性材料である水晶の単結晶で形成された球状の基材を用意する。この基材は水晶の表面に形成されていて、人の所定の体内物質と反応する反応膜を有している。即ち、反応膜は円環状表面に沿って形成されている。本実施の形態では体内物質を被検物質として分析する。反応膜は反応部として用いられている。反応膜は体内物質と反応すると硬度が増す材料で形成されている。本実施の形態では基材に水晶が用いられているが、水晶と同じ三方晶系であり、圧電性材料であるＬｉＮｂＯ_３、ＬｉＴａＯ_３等の単結晶を用いてもよい。
【００８７】
次に、反応膜と体内物質を反応させる（反応工程）。反応させるには、基材を人に経口投与する（投与工程）。このとき比較的多数の基材を投与する。基材の反応膜は体内物質と反応し硬化する。これらの基材を排泄物から取り出すことにより、投与工程で経口投与した基材を回収する（回収工程）。このとき、経口投与した基材２１０の全てを回収する必要はない。反応工程には多数の基材が必要であるが、基材は殆ど加工を要しないために非常に安価であるので、反応工程にかかるコストは比較的低い。
【００８８】
次に、回収した基材を図１を用いて説明した第１の実施の形態の弾性表面波素子の基台１２１の凹部１２２に載置する。尚、図１を参照して説明した構成部材と実質的に同一の構成部材は、第１の実施の形態の弾性表面波素子の対応する構成部材を指示していた参照符号と同じ参照符号を付して詳細な説明を省略する。載置されるとき、基材１１０は、基材１１０の経路ａが櫛形電極１２３の電極片が並ぶ方向に沿うように、位置決めされる。経路ａは図５を用いて説明したように、水晶の基材１１０のＺ軸を地軸としたときの赤道である。経路ａに沿って上記円環状表面が形成されている。基材１１０はこのＺ軸が水平にされたときに適切に位置決めされる。Ｚ軸を地軸としたとき北極と南極に対応する部分には印が設けられている。この印は基材１１０をエッチングするなどしてくぼみを作るなどして形成してもよい。位置決め後、円環状表面に沿って弾性表面波を伝搬させる（伝搬工程）。尚、基材１１０は、基材１１０の経路ｂ１，ｂ２，ｂ３が櫛形電極１２３の電極片が並ぶ方向に沿うように、位置決めされてもよい。
【００８９】
次に、伝搬工程で伝搬させられた弾性表面波を検出する（検出工程）。
【００９０】
この後、検出工程で検出された弾性表面波と、基材用意工程で用意された基材の円環状表面を伝搬する弾性表面波とを比較する。後者の弾性表面波は体内物質と反応していない反応膜を有している基材の円環状表面を伝搬する弾性表面波である。この弾性表面波は予め検出しておく。体内物質の性質、例えば特定の化学物質の濃度に応じて、体内物質と反応した反応膜の硬度は変化する。そして、反応膜の硬度に応じて弾性表面波の周波数や速度は変化する。即ち、体内物質の性質に応じて、検出工程後の弾性表面波と基材用意工程直後の弾性表面波の周波数や速度の差は変化する。これを利用して化学物質の性質を分析することができる。
【００９１】
本実施の形態では、人の体内物質を被検物質として分析していたが、動物の体内物質を被検物質として分析してもよい。
【００９２】
次に、本発明の第２の実施の形態の分析方法を説明する。本実施の形態の分析方法は例えば、配管内のアルカリ濃度を評価するために用いられる。先ず、基材用意工程を説明する。先ず直径３ｍｍの水晶の単結晶で形成された球状の基材を用意する。この基材は水晶の表面に形成されていて、アルカリ溶液に溶出するレジスト樹脂膜を有している。即ち、レジスト樹脂膜は円環状表面に沿って形成されている。レジスト樹脂膜は反応部を形成している。水晶の基材のＺ軸を地軸としたとき北極と南極に対応する部分には印が設けられている。
【００９３】
続く反応工程では基材を配管に入れ、配管内でレジスト樹脂膜をアルカリ溶液と反応させる。レジスト樹脂膜はアルカリ溶液に溶出し膜の厚さはうすくなる。反応後、基材を配管から回収する。
【００９４】
回収後、第１の実施の形態の分析方法と同様に、伝搬工程、検出工程及び比較工程を行う。本実施の形態では、レジスト樹脂膜の厚さに応じて弾性表面波の周波数や速度が変化することを利用して配管内のアルカリ溶液を分析する。
【００９５】
上記第１又は第２の実施の形態の分析方法では硬化又は溶出する反応部を用いているが、本発明はこれらに限定されない。被検物質と遊離する、結合する、分解するなどをして反応する様々な反応部を含む。
【００９６】
尚、本発明は上述した実施の形態に限定されるものではなく、発明の趣旨を逸脱しない範囲内において種々の変形や応用が可能であることは勿論である。
【００９７】
【発明の効果】
以上詳述したことから明らかなように、本発明に従った弾性表面波素子においては、極めて多い回数の弾性表面波の周回を実現することで高い精度の信号処理や評価ができる。
【図面の簡単な説明】
【図１】 本発明の第１の実施の形態における弾性表面波素子の構成を示す斜視図である。
【図２】弾性表面波の振幅を計算するために用いた座標系を示す図である。
【図３】（Ａ）、（Ｂ）、（Ｃ）及び（Ｄ）は、図２の座標系を使用して作成された式により計算された波数パラメータｍ（円周の長さと弾性表面波の波長の比）と開口半角（振動手段を設ける幅の１／２）を変えて得られた弾性表面波が球状の基材の表面を伝搬する４つの状態を概略的に示す図である。
【図４】水晶の結晶軸を示す図である。
【図５】弾性表面波が伝搬する経路を示す図である。
【図６】本発明の第１の実施の形態における弾性表面波素子の櫛形電極の平面図である。
【図７】図１の弾性表面波素子で測定された弾性表面波の波形を示す図である。
【図８】図６の櫛形電極の変形例の平面図を変形した図である。
【図９】櫛形電極のフォトマスクの穴の平面図である。
【図１０】本発明の第２の実施の形態における弾性表面波素子の基台の斜視図である。
【図１１】図１０のＬ１１−Ｌ１１断面線で切断した基台の断面図である。
【図１２】本発明の第３の実施の形態における弾性表面波素子の基台の斜視図である。
【符号の説明】
１１０ 基材
１１１ 円環状表面
１２１ 基台
１２３ 櫛形電極
２１０ 基材
２１１ 円環状表面
３２１ 基台[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a surface acoustic wave element.For childIn relationYes.
[0002]
[Prior art]
2. Description of the Related Art A surface acoustic wave element has been well known for generating surface acoustic waves on a base material and receiving surface acoustic waves generated on the base material.
[0003]
In the conventional surface acoustic wave device, a pair of comb-shaped electrodes is provided on a flat substrate. The base material is formed of a piezoelectric material, or a piezoelectric body is provided between the comb-shaped electrode and the substrate, and an elastic surface is provided in the direction in which the electrodes are arranged by supplying a high-frequency voltage to one of the comb-shaped electrodes. Excites the wave. The other comb-shaped electrode is arranged in the propagation direction of the surface acoustic wave and receives the surface acoustic wave.
[0004]
The surface acoustic wave element is used for a delay line, an oscillation element or a resonance element for a transmitter, a filter for selecting a frequency, a chemical sensor, a biosensor, a remote tag, or the like.
[0005]
[Problems to be solved by the invention]
As a method for improving the accuracy of a surface acoustic wave element, a method is known in which a surface acoustic wave is propagated to the surface of a spherical base material and the base material is circulated many times. At this time, the surface acoustic wave propagates a long distance without diffusing, but it is necessary to form a comb-shaped electrode or the like in order to apply an electric field to the surface of the substrate. In this case, in particular, in order to form a pattern smaller than 0.5 mm, a photolithography method must be adopted, and the number of man-hours increases and the cost becomes high.
[0006]
In addition, when an electrode such as a metal is directly formed on the surface of the base material, the surface acoustic wave that circulates around the surface of the base material is reflected by this electrode, and the strength is rapidly reduced as the number of turns increases. . For this reason, for example, when the evaluation is performed by measuring the time required to go around 30 times, it disappears by attenuation or diffusion after about 20 times, and evaluation with sufficient accuracy cannot be performed.
[0007]
  The present invention has been made under such circumstances, and the objects of the present invention are extremely numerous.TimesIt is to provide a surface acoustic wave device that can perform highly accurate signal processing and evaluation by realizing the surface acoustic wave circulation.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, a surface acoustic wave device according to claim 1 of the present invention includes:
  It has an annular surface that is formed of at least a part of a spherical surface and is continuous in an annular shape.PressureA base material formed of an electrically conductive material;
  A surface acoustic wave excitation means that is opposed to the annular surface at an interval and excites the surface acoustic wave propagating along the annular surface;,
  WithAnd
  The surface acoustic wave excitation means includes a comb-shaped electrode provided along the annular surface and connected to a high-frequency power source,
  The interval between the comb electrode and the annular surface is ¼ or less of the electrode period of the comb electrode.
  It is characterized by.
[0009]
In the surface acoustic wave device according to claim 2 of the present invention, the base material is a single crystal of crystal, LiNbO.₃Single crystal and LiTaO₃And a single crystal selected from the group consisting of the single crystals.
[0010]
In the surface acoustic wave element according to claim 3 of the present invention, the wavelength of the surface acoustic wave excited by the surface acoustic wave excitation means is 1/10 or less of the radius of the spherical surface of the substrate.
[0013]
  Claims of the invention4In the surface acoustic wave device according to the above, the overlapping width of the comb-shaped electrodes is not more than half of the diameter of the spherical surface of the substrate and is not less than 1/100 of the radius of the spherical surface.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
A surface acoustic wave device according to an embodiment of the present invention will be described with reference to FIGS. First, the surface acoustic wave element according to the first embodiment of the present invention will be described. FIG. 1 is a perspective view showing a configuration of a surface acoustic wave element. The surface acoustic wave element has a spherical substrate 110 made of single crystal quartz. In this embodiment, a single crystal crystal is used, but LiNbO.₃Single crystal of LiTaO₃A single crystal of a piezoelectric material such as a single crystal may be used. The substrate 110 is held on a base 121 made of fused quartz. The base 121 is provided with a recess 122 that fits a part of the spherical surface of the substrate 110. The recess 122 is shown through the substrate 110. The base material 110 is fitted in the recess 122. In the present embodiment, the radius of the substrate 110 and the radius of curvature of the recess 122 are both 5 mm. However, the dimension of the base material 110 is not limited to this.
[0018]
A comb-shaped electrode 123 indicated by hatching is provided in the recess 122 along the surface of the substrate 110. The comb-shaped electrode 123 has a 500 mm thick chromium layer laminated on the surface of the base 121 and a 1500 mm thick gold layer laminated on the chromium layer. These layers are formed by thermal evaporation and then patterned by photolithography to form a pair of comb patterns. In addition to the comb pattern, a circuit for generating an electric field (not shown) connected to the comb pattern is formed on the surface of the substrate 110. The comb electrode 123 includes such a circuit.
[0019]
The comb electrode 123 may be formed by other forming methods. For example, conductive foil may be cut into a comb shape and attached to the recess 122. Further, printing, sputtering, sol-gel method or the like may be used. The comb electrode 123 is connected to a transmitter 126 having a high frequency power source via an impedance matching circuit 124 and a circulator 125. The comb electrode 123 is used as a surface acoustic wave excitation means.
[0020]
A resin thin film is formed on the surface of the quartz substrate 110. The resin thin film is formed by creating a resist thin film pattern by a photoresist process and performing a hardening process.
[0021]
When a voltage is applied to the comb electrode 123, the comb electrode 123 generates an electric field. This electric field is applied to the surface of the substrate 110 that passes through the resin thin film and faces the recess 122.
[0022]
By the way, when the recessed part 122 is not provided in the base 121, and the comb-shaped electrode is formed in the flat base, and these are facing the base material 110, an electric field is relatively on the surface of the base material 110. It is applied only to a narrow area. In contrast, if the recess 122 is provided as in the present embodiment, an electric field can be applied to a relatively wide area of the substrate 110.
[0023]
The crystal of quartz forming the substrate 110 is a piezoelectric material. When an electric field is applied to the surface of the substrate 110, the surface of the substrate 110 vibrates due to the piezoelectric effect, and a surface acoustic wave of a predetermined mode is excited on the surface of the substrate 110. The surface acoustic wave excitation means using the comb electrode 123 can excite surface acoustic waves in a specific direction with relatively high efficiency.
[0024]
In this specification, the elastic wave which propagates by concentrating energy on the surface of a single crystal base material is collectively referred to as a surface acoustic wave. Also included are leaky surface acoustic waves that propagate while releasing energy from a single crystal substrate, SH (shear horizontal) waves, and elastic waves called lateral waves.
[0025]
The excited surface acoustic wave propagates along the annular surface 111 of the substrate 110 that is continuous in an annular shape. The surface acoustic wave goes around the surface of the substrate 110. The surface acoustic wave excitation means, in this embodiment, the comb-shaped electrode 123 is opposed to the annular surface 111 at an interval, and is provided along the annular surface 111. Fine resin particles are interspersed between the comb-shaped electrode 123 and the annular surface 111, and the comb-shaped electrode 123 and the annular surface 111 are not in direct contact with each other. For this reason, the surface acoustic wave that circulates around the surface of the substrate 110 is less likely to be scattered by the comb electrodes.
[0026]
When the comb electrode is directly formed on the surface of the substrate, the surface acoustic wave excited on the surface of the substrate is reflected or scattered by the comb electrode. This is not the case in this embodiment.
[0027]
When predetermined conditions are met, an elastic wave may be excited using a resin thin film as a waveguide. Such a mode of acoustic wave is also included in the surface acoustic wave of the present embodiment.
[0028]
The inventors' experiments have shown that the comb-shaped electrode is not in contact with the surface of the substrate, so that it can excite surface acoustic waves with sufficient strength and can realize extremely many rounds compared to the case where it is in contact. Such characteristics are extremely advantageous for application to various sensors.
[0029]
If the space between the surface acoustic wave excitation means and the annular surface 111 can apply an electric field to the quartz crystal substrate 110, which is a piezoelectric material, the distance between the surface acoustic wave excitation means and the surface acoustic wave wavelength excited by the surface acoustic wave excitation means. It is preferable that it is 1/4 or less. When this interval exceeds 1/4 of the wavelength, it is confirmed that the amplitude of the electric field strength on the surface of the base material based on the voltage gradient of the comb electrode becomes gentle, and the strength of the excited surface acoustic wave becomes extremely weak. ing.
[0030]
As will be described later, the wavelength of the surface acoustic wave is generally substantially equal to the electrode period of the comb-shaped electrode 123 under predetermined conditions. If this fact is used, the relationship between the distance and the wavelength can be paraphrased as that the distance between the comb-shaped electrode 123 and the annular surface 111 is ¼ or less of the electrode period of the comb-shaped electrode 123. In the present embodiment, the diameter of the resin particles, that is, the interval between the comb electrode 123 and the annular surface 111 is 10 μm, and the wavelength is 0.209 mm as will be described later.
[0031]
In addition to the transmitter 126 described above, an amplifier 127 and a digital oscilloscope 128 are connected to the comb electrode 123. If the comb-shaped electrode 123 is used, it is possible to detect a surface acoustic wave that is input to the comb-shaped electrode 123 after it circulates. Here, since the comb electrode 123 has a function of detecting the surface acoustic wave by converting the surface acoustic wave into an electric signal again, the excitation and detection of the surface acoustic wave can be performed with only one pair of comb electrodes. The comb electrode for detection may be separately formed on the propagation path of the surface acoustic wave.
[0032]
The phenomenon of surface acoustic waves propagating along the annular surface of a spherical substrate has been known for substrates made of isotropic materials. About the base material formed with the single crystal, the propagation speed of a surface acoustic wave changes according to crystal orientation. Then, in order to pass through a crystal plane that cannot propagate in the process of circling a spherical base material formed of a single crystal or through a crystal face where energy is diffused, surface acoustic waves are generated on the surface of the base material. It was thought that the efficiency at the time of orbiting deteriorated, and energy was consumed rapidly each time it orbited.
[0033]
However, quartz, LiNbO₃LiTaO₃It has been experimentally confirmed by the inventors that a similar phenomenon occurs with a trigonal single crystal base material such as the same, if a path through which surface acoustic waves propagate is appropriately selected. This path is determined by the crystal orientation as will be described later. The surface acoustic wave propagating along this path is less dissipated in the energy of the elastic wave and reflected on the surface of the sphere, so that it is possible to realize a good circulation with less noise.
[0034]
When forming a base material with a non-piezoelectric material as in the past, it is necessary to form a piezoelectric film between the base material and the comb-shaped electrode. LiNbO₃LiTaO₃Since the quartz crystal forming the base material of the present embodiment is a good piezoelectric material, it is not necessary to form a piezoelectric film and the cost is low. In addition, since there is no risk of changing the characteristics of the surface acoustic wave element with the conditions of the piezoelectric film formation process, the same product can be produced stably.
[0035]
Quartz, LiNbO than when using a non-piezoelectric material substrate₃And LiTaO₃The signal purity is higher when the base material is used. Therefore, the performance can be greatly improved as compared with the conventional surface acoustic wave device.
[0036]
Among the single crystals, quartz is very useful because it has high hardness, can be easily processed, and can be obtained at low cost as a material. LiNbO₃And LiTaO₃In addition, a good circulation with less noise can be realized because of the large electromechanical coupling coefficient and the characteristics of the temperature dependence of the phase velocity of the surface acoustic wave.
[0037]
The conditions for circling the surface of the spherical base material without the surface acoustic wave diffusing were determined approximately as follows. The following calculation explains the case where the base material is formed of an isotropic material. However, in the region where most of the surface acoustic waves circulate, the surface acoustic wave phase velocity in the direction in which the surface acoustic waves propagate significantly changes. If not, a theoretical approximation can be made.
[0038]
First, a case where the surface acoustic wave generation source can be regarded as a point will be described. The source is on the surface of the spherical substrate. This corresponds to the overlapping width of the comb electrodes 123 being less than 1/100 of the radius of the spherical surface of the substrate 110. Here, the overlapping width is a length in which the plurality of electrode pieces of one comb-shaped pattern and the plurality of electrode pieces of the other comb-shaped pattern face each other.
[0039]
A surface acoustic wave concentrically converges on a surface opposite to the source after concentrically spreading on a spherical surface around the source. Then, after concentrically spreading on the spherical surface from a point on the opposite side, the light is focused on the generation source. That is, when the source can be regarded as a point, it diffuses without directivity. When the comb electrode is directly formed on the substrate, or when the support part for supporting the substrate is in direct contact with the substrate, the wiring attachment part of the comb electrode and the comb pattern of the comb electrode are connected. The surface acoustic wave is scattered by a predetermined circuit, support portion, and the like. This does not happen in this embodiment.
[0040]
Next, a case where the surface acoustic wave generation source can be regarded as an arc will be described. This corresponds to the overlapping width of the comb-shaped electrode 123 being 1/100 or more of the radius of the spherical surface of the substrate 110. However, the entire width of the comb-shaped electrode including the accompanying electric circuit pattern needs to be less than or equal to half of the peripheral length of the substrate 110, and therefore the overlapping width of the comb-shaped electrode 123 is less than or equal to half of the diameter of the spherical surface of the substrate 110. It is. FIG. 2 shows a coordinate system in which the center of the spherical substrate is the origin O. Points of intersection of the XYZ coordinate axis and the spherical surface with the radius r of the base material are points A, B, and C, respectively. Further, the point between the OBs, the point on the Y-axis is the point E, the point E is the intersection of the straight line parallel to the Z-axis and the spherical surface, the point F is the point of intersection, Is a point D. It is assumed that the surface acoustic wave generated from the point P on the arc DF reaches the point Q on the arc CG. Here, the point G is a point on the arc AB. Angle φ₀, Θ₀, Φ₁, Θ₁Is taken as shown in FIG. 2, the coordinates of points P and Q are respectively
(Rcosφ₀cosθ_o, Rsinφ₀, Rcosφ₀sinθ_o)as well as
(Rcosφ₁cosθ₁, R cos θ₁sinφ₁, Rsinθ₁)
So that
PQ²= 2r²[1-cosφ₀cosθ_ocosφ₁cosθ₁-Sinφ₀cosφ₁cosθ₁-Cosφ₀sinφ₀sinθ₁] ... (1)
It is. Therefore, if the angle POQ = θ, the cosine theorem
cos θ = cos φ₀cosθ_ocosφ₁cosθ₁+ Sinφ₀cosφ₁cosθ₁+ Cosφ₀sinφ₀sinθ₁  ... (2)
The relationship holds.
[0041]
The radial component of the particle displacement at point Q of the surface acoustic wave generated at point P is
[Expression 1]

(Viktorov, Rayleigh and Lamb Waves). Equation (3) is obtained for Rayleigh waves and Lamb waves, but can also be applied to surface acoustic waves in general. Here, C is a constant, C_RIs the Rayleigh wave velocity and t is time. m is
m = circumference length / surface acoustic wave wavelength
Which is called the wavenumber parameter.
[0042]
The angle θ is obtained from the equation (2). The angle seen from point E is 2θ_AThe sound field at point Q by the arc-shaped sound source of_oAbout -θ_ATo θ_AIs obtained by integrating up to. Sound field distribution is angle of attack θ of point Q₁It is calculated by changing
[0043]
FIG. 3 shows that the point P is on the XZ plane.₀Four states are shown in which the surface acoustic wave obtained using Equation (3) for the case of = 0 propagates on the spherical surface.
[0044]
3 (A), 3 (B), and 3 (C) show the sound field (the angle θ of the absolute value of the particle displacement) when the wave number parameter m = 600.₁(Dependency) is the result of examining. In each of the figures, the bottom plot is an angle (propagation angle) φ representing the propagation of a surface acoustic wave on a spherical surface.₁Is the sound field in the case of 0 °, and the sound field in the case of increasing by 15 ° upwards is plotted in order.
[0045]
FIG. 3A shows the opening half angle θ._A= 30 °. In this case, as is apparent from FIG. 3A, the propagation state of the surface acoustic wave is a focused beam shape. That is, the propagation angle φ₁As the value increases, the width of the sound field decreases and φ₁After reaching the minimum at 90 °, the width increases again, and the same distribution as that on the sound source is reproduced at the counter electrode 180 °. Thereafter, the same change is repeated every 180 °, and the same change is repeated no matter how many times it circulates. This is a phenomenon peculiar to a spherical surface where there is no wave diffusion due to diffraction. In this case, the opening half angle θ_A= The sound field does not spread more than 30 °, θ₁<Θ_AThe energy of the surface acoustic wave is confined in the belt-like portion. In this case, the spherical θ₁> Θ_AEven if another object is brought into contact with this part, the sound field is not disturbed.
[0046]
FIG. 3C shows the opening half angle θ._A= 1 °. In this case, as is apparent from FIG. 3C, the propagation state of the surface acoustic wave has a divergent beam shape similar to that of the point sound source. That is, the propagation angle φ₁As the value increases, the width of the sound field also increases and φ₁After reaching the maximum at 90 °, the width decreases again, and the same distribution as that on the sound source is reproduced at the counter electrode 180 °. In this case, unlike the case of the focused beam described above with reference to FIG.₁<Θ_AThe energy of the surface acoustic wave is not confined in the band-like portion of₁= 90 ° spreads over the entire surface of the sphere. In this case, the φ of the spherical surface₁= 90 ° and θ₁> Θ_AIf another object is brought into contact with this part, the sound field is disturbed.
[0047]
FIG. 3B shows the opening half angle θ._A= 3.5 °. In this case, as is apparent from FIG. 3B, the propagation state of the surface acoustic wave is the propagation angle φ.₁The width of the sound field hardly changes even when the value increases. That is, θ₁= Θ_AThe energy of the surface acoustic wave is confined in the belt-like portion. This is the same characteristic as a Bessel beam in an infinite medium. And the aperture half angle θ at which the collimated beam is obtained_AThe collimating angle θ_colCall it.
[0048]
As is clear from FIGS. 3A, 3B, and 3C, the opening half angle θ_AIs the collimating angle θ_colWhen the surface wave energy is confined to the narrowest band,
Further, as a result of performing the same numerical analysis as described above by changing the wave number parameter m, the collimation angle θ is determined by the wave number parameter m._colWas found to change. FIG. 3D shows that when the wave number parameter m is 300, the propagation state of the surface acoustic wave becomes a collimated beam shape._AIs approximately 4.5 °, and in this case the collimating angle θ_colBecomes about 4.5 °.
[0049]
Below, the collimating angle θ when the wave number parameter m changes_colIndicates the value of.
[0050]

This is an approximate value by numerical calculation. Thus, the collimating angle θ_colIs obtained from the wave number parameter m using equation (3).
[0051]
With reference to FIG. 1 again, the surface acoustic wave device of the present embodiment will be described. When a surface acoustic wave is output from the comb electrode 123, it propagates along the annular surface 111 as described above. For convenience of explanation, the width of the annular surface 111 is made equal to the overlapping width of the comb electrodes 123. The overlapping width of the comb electrode 123 is determined by the collimating angle θ_colThe width of the surface acoustic wave source defined by More preferably, the overlap width is the collimating angle θ_colIs equal to the width defined by The surface acoustic wave propagates along the annular surface 111 without diffusing beyond the width of the annular surface 111 from the result of the numerical calculation. This propagation state corresponds to FIG. 3 (A) and FIG. 3 (B). Collimation angle θ_colA typical value of the wave number parameter m for determining the value is 100 to 800, but the wave number parameter m of the present invention is not limited to this value.
[0052]
In the above numerical calculation, the wavelength and phase velocity of the surface acoustic wave have been described as being constant at all locations on the spherical surface through which the surface acoustic wave propagates. However, in the case of a spherical base material made of crystal, which is a crystal, the wavelength and phase velocity of a surface acoustic wave having a certain frequency generally differ according to the crystal orientation. Therefore, it is assumed that the wave number parameter m is not constant on the spherical surface but is approximately constant. In order to obtain the constant wave number parameter m, the wavelength of the surface acoustic wave propagating through the portion of the substrate where the surface acoustic wave is excited by the surface acoustic wave excitation means is used. That is, the wavelength of the portion of the substrate 110 on which the comb electrode 123 is provided is used. Furthermore, it is desirable to set the shape of the electrode pattern of the comb-shaped electrode 123 according to the wavelength on the substrate 110 at the position of each electrode piece.
[0053]
The annular surface 111 on which the surface acoustic wave propagates is formed along a predetermined path determined by the crystal orientation of the single crystal forming the substrate 110 as described above. This route has been confirmed by the inventors' experiments for crystals belonging to the trigonal system. This path is related to the Z axis of the crystal. The crystal axis of the quartz is shown in FIG.
[0054]
FIG. 5 is a diagram showing this route. For convenience of explanation, it is assumed that the Z axis passes through the center of the spherical substrate 110. The predetermined path determined by the crystal orientation includes four paths a, b1, b2, and b3. The path a is a line of intersection between a spherical surface that is the surface of the substrate 110 and a plane that passes through the center of the spherical surface and is orthogonal to the Z axis. Paths b1, b2, and b3 are intersections of a spherical surface that is the surface of the substrate 110 and three planes that pass through the center of the spherical surface and are parallel to the Z axis. The plane including the path b1 forms an angle of 60 ° and −60 ° with the plane including the paths b2 and b3, respectively. Considering the Z axis as the ground axis of the spherical substrate 110, the path a is the equator, and the paths b1, b2, and b3 are composed of six meridians arranged at intervals of 60 °.
[0055]
In the present embodiment, the surface acoustic wave propagates along the path a as shown in FIG. That is, the annular surface 111 is formed along the path a. However, the present invention is not limited to this. A surface acoustic wave may be propagated along at least two of the paths a, b1, b2, and b3. For example, when propagating along the path a and the path b1, surface acoustic wave excitation means are provided to face the paths a and b1, respectively. Further, a scatterer that scatters a surface acoustic wave or a reflector that reflects a surface acoustic wave is provided at a portion of the substrate 110 where the path a and the path b1 intersect, and the surface acoustic wave propagating through the path a is branched into the path b1. May be. If a scatterer or reflector that can ignore the disturbance of the surface acoustic wave on the path a is provided, the surface acoustic wave that is excited on the path a and circulates on the path a can be detected outside the path a.
[0056]
The comb electrode 123 will be described in more detail. FIG. 6 is a plan view of the comb electrode 123. The comb electrode 123 includes a pair of comb patterns 123a and 123b. The comb pattern 123a has a plurality of electrode pieces l1, l2, l3,... Arranged in the direction in which the surface acoustic wave propagates. As will be described later, the direction in which the surface acoustic wave propagates is made to coincide with the path a of the substrate 110 as shown in FIG. The comb pattern 123b has electrode pieces l1, l2, l3,... And a plurality of electrode pieces r1, r2, r3,. The intervals between adjacent electrodes (for example, electrode piece r1 and electrode piece l1, or electrode piece l1 and electrode piece r2) are all equal. The electrode pieces l1, l2, l3,... And the electrode pieces r1, r2, r3,. That is, if the Z axis is the ground axis of the substrate 110, these electrode pieces extend along meridians. These electrode pieces are arranged periodically. That is, if the electrode pieces l1 and r1 are moved along the path a, the electrode pieces l2 and r2, and the electrode pieces l3, r3,. The electrode pieces l1 and r1 form a unit of electrode pieces arranged periodically. By arranging the units of the electrode pieces in the direction in which the surface acoustic wave propagates, a pair of comb patterns 123a and 123b of the comb electrode 123 are formed.
[0057]
The electrode period P, which is the unit length of the electrode piece in the direction in which the surface acoustic wave propagates, is constant. The wavelength of the surface acoustic wave excited by the surface acoustic wave excitation means is 1/10 or less of the radius of the spherical surface of the substrate. At this time, this wavelength is not the natural vibration of the entire substrate 110 but is substantially equal to the electrode period P. However, as described above, the wavelength of the surface acoustic wave excited by the surface acoustic wave excitation means, that is, the wavelength of the surface acoustic wave propagating through the portion of the base 110 facing the comb-shaped electrode 123 is the other of the base 110. It may be different from the wavelength of the part.
[0058]
A description will be given with reference to FIG. 1 again. The Z-axis of the quartz substrate 110 is horizontal. As described above, the substrate 110 is positioned with respect to the recess 122 so that the electrode pieces of the comb-shaped electrode 123 are arranged along the path a.
[0059]
The electrode period of the comb electrode 123 is set as follows. Hereinafter, the substrate 110 is considered to be formed of an isotropic material. A certain value of the phase velocity of the Rayleigh wave of the X-axis propagation on the Y-cut surface of the crystal of the crystal is 3160 m / s. This is regarded as a typical phase velocity of a surface acoustic wave. Consider a case where an element that excites a surface acoustic wave having a frequency of 15.1 MHz is produced. An element with a wave number parameter of 150 is to be created. The wavelength of the surface acoustic wave is 0.209 mm from 3160 m / s ÷ 15.1 MHz = 209.3 μm. Therefore, the electrode period is set to 0.209 mm. Since the perimeter is 31.415 mm, the radius is 5.0 mm. As described above, the wavelength of the surface acoustic wave is 1/10 or less of the radius of the spherical surface of the substrate 110.
[0060]
The overlap width so that the surface acoustic wave does not diffuse is set as follows. Collimation angle θ corresponding to a wave number parameter of 150_colIs 7.0 ° from the above numerical calculation. From the definition of the collimating angle, the overlap width is

Therefore, the overlap width is set to 1.22 mm.
[0061]
FIG. 7 shows a waveform obtained by inputting an impulse signal into the surface acoustic wave device of this embodiment every 1 mm second with a signal amplitude of 20 V and a time width of 2 nanoseconds, and observing the output signal through a 20 MHz low-pass filter. Show. It was confirmed that the noise signal was very small and it circulated up to 10 times.
[0062]
Next, a modification of the comb electrode will be described. FIG. 8 is a diagram obtained by modifying the plan view of the comb patterns 123c and 123d of the present modification. In FIG. 8, when the Z axis of the quartz base material 110 is the ground axis, all the parallels are set to the same length. That is, when the base material 110 is viewed perpendicular to the ground axis, the base material 110 looks square.
[0063]
The comb pattern 123c has a plurality of electrode pieces S1, s1, S2, s2, S3, s3,... Arranged along the path a. These electrode pieces extend in the meridian direction. The electrode pieces S1, s1, the electrode pieces S2, s2, the electrode pieces S3, s3,. These electrode pieces are arranged periodically. The distance between the electrode piece S1 and the electrode piece S2, the distance between the electrode piece S2 and the electrode piece S3, are all equal. The distance between the electrode piece S1 and the electrode piece s1, the distance between the electrode piece S2 and the electrode piece s2, the distance between the electrode piece S3 and the electrode piece s3, are all equal. If the electrode pieces S1, s1 are moved along the path a, they overlap with the electrode pieces S2, s2, the electrode pieces S3, s3,.
[0064]
The comb pattern 123d has a plurality of electrode pieces T0, T1, T2, T3,... Arranged along the path a. These electrode pieces extend in the meridian direction. The electrode piece T1 is arranged between the electrode piece s1 and the electrode piece S2, and the electrode piece T2 is arranged between the electrode piece s2 and the electrode piece S3. The electrode pieces Ti (i = 3, 4, 5,...) After T3 are also arranged between the electrode pieces si and the electrode pieces Si + 1, similarly to the electrode pieces T1, T2. The electrode piece T0 is disposed such that the electrode pieces S1 and s1 are located between the electrode piece T0 and the electrode piece T1. Among the electrode pieces T0, T1, T2, T3,..., The intervals between adjacent electrode pieces are all equal. If the electrode piece T0 is moved along the path a, it overlaps with the electrode pieces T1, T2, T3,.
[0065]
The electrode pieces S1, s1, T1, the electrode pieces S2, s2, T3, the electrode pieces S3, s3, T3,. From the above description, it is apparent that these electrode pieces are arranged periodically. The electrode pieces S1, s1, T1 form a unit of electrode pieces arranged periodically. The dimensions of the comb patterns 123c and 123d will be described. The electrode period P is as shown in FIG.
Electrode period P = (Distance between electrode piece S1 and electrode piece S2) + (Width of electrode piece S1 in the direction along path a)
It is represented by Using the electrode period P, the dimensions of the comb patterns 123c and 123d are
Width of electrode piece S1 in the direction along path a = P / 4
Width of electrode piece T1 in the direction along path a = P / 8
Distance between electrode piece T1 and electrode piece S2 = 3P / 16
It is set to become.
[0066]
When the comb patterns 123c and 123d are formed as described above, surface acoustic waves can be output in one direction (the direction of the arrow in FIG. 8) along the path a.
[0067]
Various modifications and variations can be made to the comb-shaped electrode 123 of the present embodiment and the above-described modifications thereof. For example, the electrode piece extends along the meridian of the substrate 110, but may extend in a direction intersecting the meridian. When a comb-like electrode is formed by a photoresist with a plate-like photomask having holes extending linearly in the vertical direction and the horizontal direction as shown in FIG. It extends in the direction that intersects. Such a photomask can be easily designed, and a photoresist can be easily formed.
[0068]
Further, the interval between adjacent electrode pieces (for example, the interval between the electrode piece S1 and the electrode piece s1, the interval between the electrode piece s1 and the electrode piece T1, etc.) or the interval between the electrode pieces (the interval between the electrode piece T1 and the electrode piece S2). ), Or the electrode period may not be constant. As described above, in a sphere formed of crystal, which is a crystal, the wavelength and phase velocity generally differ according to the crystal orientation. If an electrode period or the like is set according to the wavelength of the portion of the substrate 110 where the electrode piece is located, a surface acoustic wave having a desired frequency can be excited efficiently.
[0069]
By the way, conventionally, a surface acoustic wave element in which a base material is a flat plate and a set of electrode pieces is periodically arranged is known as a surface acoustic wave element for a wide band. When such a surface acoustic wave element is applied to the spherical substrate 110, surface acoustic waves are excited over a wide wavelength range. Collimation angle θ related to wavelength_colHowever, only surface acoustic waves having a wavelength that is equal to or greater than the overlapping width of the comb electrodes can circulate the substrate 110 without diffusing.
[0070]
In this embodiment, the comb-shaped electrode 123 is connected to the transmitter 126 having a high-frequency power source, but the present invention is not limited to this. For example, instead of the high-frequency power supply 123, an antenna that receives high-frequency radio waves may be connected to the comb-shaped electrode 123. When a high-frequency radio wave is received by the antenna, an electric field is generated in the comb-shaped electrode 123 and a surface acoustic wave is excited, as in the case where the transmitter 126 is connected.
[0071]
Next, a surface acoustic wave device according to a second embodiment of the present invention will be described. Most of the configuration of the present embodiment is basically the same as most of the configuration of the first embodiment. In the present embodiment, substantially the same components as those described with reference to FIG. 1 of the first embodiment refer to the corresponding components of the first embodiment. The same reference numerals as the reference numerals are assigned and detailed description is omitted.
[0072]
The difference between the configuration of the present embodiment and the configuration of the first embodiment is the configuration of the base material. The base material of the present embodiment is not provided with a resin thin film. FIG. 10 is a perspective view of the base 121. Spacers 231 and 232 are provided on the base 121 so that the comb-shaped electrode 123 faces the base material with a gap. The spacers 231 and 232 are provided by curing a resist resin. The spacers 231 and 232 are arranged on both sides of the portion of the comb electrode 123 where the comb pattern is formed, and are provided so as not to affect the propagation of the surface acoustic wave.
[0073]
11 is a cross-sectional view of the base 121 taken along the line L11-L11 in FIG. 10, and the base material 210 is held by the spacers 231 and 232. The L11-L11 cross-sectional line passes through the two spacers 231 and 232 and extends in a direction orthogonal to the direction in which the electrode pieces of the comb-shaped electrode 123 are arranged.
[0074]
The base member 210 includes a spherical member 212 formed of a glass material which is an isotropic material, a gold film 213 having a thickness of 1000 mm covering the spherical member 212, and a ZnO Z-axis alignment film 214 covering the gold film 213. Have. In FIG. 11, the gold film 213 and the alignment film 214 are shown partially removed from the surface of the spherical member 212. The alignment film 214 is a piezoelectric material. That is, a part of the substrate 210 is formed of a piezoelectric material.
[0075]
The gold film 213 is formed by vapor deposition or the like. The alignment film 214 is formed by DC sputtering. By performing sputtering while rotating the substrate 210, an alignment film can be formed in an annular region that goes around the substrate 210. By utilizing this, an alignment film can be formed over the entire surface of the substrate 210. Known techniques can be basically used for the concentration of gas used in DC sputtering, the voltage of DC high voltage, and the like, and for the method of creating a vapor deposition mask.
[0076]
When an electric field is applied to the substrate 210 by the comb-shaped electrode 123, the Z-axis alignment film 214 of ZnO vibrates due to the piezoelectric effect. As a result, the surface acoustic wave propagating along the annular surface 211 of the substrate 210 is excited. The annular surface 211 extends between the spacers 231 and 232 along the direction in which the electrode pieces of the comb-shaped electrode 123 are arranged. The annular surface 211 is separated from the spacers 231 and 232. Thereby, the surface acoustic wave can propagate through the annular surface 211 without being scattered or reflected. The annular surface 211 does not follow a specific path based on the properties of the material, like the quartz substrate 110 described in the first embodiment with reference to FIG. However, the annular surface 211 extends along the maximum circumference of the substrate 210.
[0077]
In the present embodiment, the overlapping width of the comb-shaped electrode 123 is 2 mm, and the electrode period is 350 μm. The height of the spacers 231 and 232, that is, the distance between the comb-shaped electrode 123 and the annular surface 211 is 10 μm as in the first embodiment. This is ¼ or less of the electrode period.
[0078]
In the present embodiment, two spacers are provided on both sides of the comb-shaped portion of the comb-shaped electrode 123, but the present invention is not limited to this. For example, two may be provided on both sides. Alternatively, a relatively good spacer can be obtained by dispersing fine resin particles between the substrate 210 and the comb-shaped electrode 123.
[0079]
Next, a surface acoustic wave device according to a third embodiment of the present invention will be described. Most of the configuration of the present embodiment is basically the same as the configuration of the second embodiment. In the present embodiment, substantially the same components as those described with reference to FIGS. 10 and 11 of the second embodiment indicate the corresponding components of the second embodiment. The same reference numerals as those used in the above description are attached and detailed description thereof is omitted.
[0080]
In the present embodiment, a base 321 is used instead of the base 121 of the second embodiment. FIG. 13 is a perspective view of the base 321. On the upper surface of the base 321, prismatic electrode pieces u 1, v 1, u 2, v 2, u 3, v 3, u 4 extending in the vertical direction are arranged in the horizontal direction in this order. These electrode pieces form comb electrodes. A concave surface having a shape along a part of the spherical surface of the substrate 210 is formed over the upper surfaces of these electrode pieces. Adjacent electrode pieces in the electrode pieces u1, v1, u2, v2, u3, v3, u4 are connected to different electrodes, respectively. That is, the electrode pieces u1, u2, u3, u4 are connected to the electrode 335, and the electrode pieces v1, v2, v3 are connected to the electrode 336, respectively. These electrode pieces and the base 321 are formed by cutting a glass epoxy material and plating copper on a portion corresponding to the upper surface of the electrode pieces. The overlapping width and electrode period of the comb-shaped electrodes formed of these electrode pieces are the same as those in the second embodiment. The electrodes 335 and 336 are connected to the impedance matching circuit 124 (see FIG. 1) via a predetermined circuit. The electrode pieces u1, v1, u2, v2, u3, v3, u4 and the electrodes 335, 336 are used as surface acoustic wave excitation means.
[0081]
Four holding members 331, 332, 333, and 334 for holding the base material 210 are provided on the upper surface of the base 321. When the substrate 210 is held by the holding members 331, 332, 333, and 334, the upper surfaces of the electrode pieces u 1, v 1, u 2, v 2, u 3, v 3, u 4 face the surface of the substrate 210 with a gap. When an electric field is applied to the substrate 210 by these electrode pieces, a surface acoustic wave propagating along the annular surface 211 of the substrate 210 is excited. The annular surface 211 extends along the maximum circumferential line as in the second embodiment. Comb electrodes formed of these electrode pieces are opposed to the annular surface 211 at a distance. This interval is the same as that of the second embodiment, and is ¼ or less of the electrode period. The holding members 331, 332, 333, and 334 are located on both sides of the annular surface 211.
[0082]
Even if the surface acoustic wave element is configured in this way, the same effect as in the second embodiment can be obtained.
[0083]
In the present embodiment, the comb electrode is formed of seven electrode pieces u1, v1, u2, v2, u3, v3, u4, but the present invention is not limited to this. The number of electrode pieces may be 2 to 6, or 8 or more.
[0084]
Various modifications and variations can be made to the first to third embodiments. For example, the quartz crystal substrate 110 of the first embodiment may be held on the base 121 of the second embodiment or the base 321 of the third embodiment. In this case, a resin thin film is not formed on the substrate 110 of the first embodiment. The substrate 110 has the same structure as that of the second embodiment so that the path a of the substrate 110 is along the direction in which the comb electrodes 123 of the first embodiment or the electrode pieces of the comb electrodes of the second embodiment are arranged. It is positioned on the base 121 or the base 321 of the third embodiment.
[0086]
Next, an analysis method according to the first embodiment of the present invention will be described. First, a base material having an annular surface that is formed of at least a part of a spherical surface and is continuous in an annular shape is prepared (base material preparation step). In the present embodiment, a spherical base material formed of a single crystal of quartz that is a piezoelectric material is prepared. This base material is formed on the surface of the crystal and has a reaction film that reacts with a predetermined human body substance. That is, the reaction film is formed along the annular surface. In this embodiment, the in-vivo substance is analyzed as a test substance. The reaction membrane is used as a reaction part. The reaction film is formed of a material that increases in hardness when it reacts with a substance in the body. In this embodiment, quartz is used as the base material, but it is the same trigonal system as quartz and is a piezoelectric material, LiNbO.₃LiTaO₃A single crystal such as may be used.
[0087]
Next, the reaction film is reacted with the substance in the body (reaction process). To react, the substrate is orally administered to a person (administration process). At this time, a relatively large number of substrates are administered. The reaction film of the base material reacts with the substance in the body and hardens. By removing these base materials from the excrement, the base material orally administered in the administration step is recovered (recovery step). At this time, it is not necessary to collect all of the base material 210 administered orally. Although a large number of substrates are required for the reaction process, the cost for the reaction process is relatively low because the substrate requires very little processing and is very inexpensive.
[0088]
Next, the recovered base material is placed in the concave portion 122 of the base 121 of the surface acoustic wave element according to the first embodiment described with reference to FIG. Note that components substantially the same as the components described with reference to FIG. 1 have the same reference numerals as the reference numerals indicating the corresponding components of the surface acoustic wave element according to the first embodiment. Detailed description will be omitted. When placed, the base 110 is positioned so that the path a of the base 110 is along the direction in which the electrode pieces of the comb-shaped electrodes 123 are arranged. As described with reference to FIG. 5, the path a is the equator when the Z axis of the quartz base material 110 is the ground axis. The annular surface is formed along the path a. The substrate 110 is properly positioned when the Z axis is leveled. Marks are provided on portions corresponding to the north and south poles when the Z axis is the ground axis. This mark may be formed, for example, by etching the base material 110 to create a recess. After positioning, a surface acoustic wave is propagated along the annular surface (propagation process). The substrate 110 may be positioned so that the paths b1, b2, and b3 of the substrate 110 are along the direction in which the electrode pieces of the comb-shaped electrode 123 are arranged.
[0089]
Next, the surface acoustic wave propagated in the propagation process is detected (detection process).
[0090]
Thereafter, the surface acoustic wave detected in the detection step is compared with the surface acoustic wave propagating on the annular surface of the base material prepared in the base material preparation step. The latter surface acoustic wave is a surface acoustic wave that propagates on the annular surface of a substrate having a reaction film that does not react with the body substance. This surface acoustic wave is detected in advance. The hardness of the reaction film that has reacted with the internal substance varies depending on the nature of the internal substance, for example, the concentration of a specific chemical substance. The frequency and speed of the surface acoustic wave change according to the hardness of the reaction film. That is, the difference in the frequency and speed between the surface acoustic wave after the detection step and the surface acoustic wave immediately after the substrate preparation step changes depending on the properties of the in-vivo substance. This can be used to analyze the properties of chemical substances.
[0091]
In the present embodiment, the human body substance is analyzed as the test substance, but the animal body substance may be analyzed as the test substance.
[0092]
Next, an analysis method according to the second embodiment of the present invention will be described. The analysis method of the present embodiment is used, for example, for evaluating the alkali concentration in the pipe. First, the base material preparation step will be described. First, a spherical substrate formed of a single crystal of quartz having a diameter of 3 mm is prepared. This base material is formed on the surface of quartz and has a resist resin film that elutes into an alkaline solution. That is, the resist resin film is formed along the annular surface. The resist resin film forms a reaction part. Marks are provided on portions corresponding to the north and south poles when the Z axis of the quartz base material is the ground axis.
[0093]
In the subsequent reaction step, the base material is put in a pipe, and the resist resin film is reacted with an alkaline solution in the pipe. The resist resin film elutes in the alkaline solution and the film thickness is thin. After the reaction, the substrate is recovered from the pipe.
[0094]
After the collection, the propagation step, the detection step, and the comparison step are performed as in the analysis method of the first embodiment. In the present embodiment, the alkaline solution in the pipe is analyzed using the fact that the frequency and speed of the surface acoustic wave change according to the thickness of the resist resin film.
[0095]
In the analysis method of the first or second embodiment, a reaction part that hardens or elutes is used, but the present invention is not limited thereto. It includes various reaction parts that react with the test substance by releasing, binding, or decomposing.
[0096]
It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications and applications can be made without departing from the spirit of the invention.
[0097]
【The invention's effect】
  As is clear from the above detailed description, the surface acoustic wave device according to the present invention is extremely numerous.TimesHigh-accuracy signal processing and evaluation can be achieved by realizing the surface acoustic wave circulation.
[Brief description of the drawings]
FIG. 1 shows a surface acoustic wave element according to a first embodiment of the present invention.Of childIt is a perspective view which shows a structure.
FIG. 2 is a diagram showing a coordinate system used for calculating the amplitude of a surface acoustic wave.
3 (A), (B), (C) and (D) are wave number parameters m (circumference length and surface acoustic wave) calculated by an equation created using the coordinate system of FIG. FIG. 6 is a diagram schematically showing four states in which surface acoustic waves obtained by changing the ratio of the wavelength and the half angle of the opening (1/2 of the width at which the vibration means is provided) propagate through the surface of a spherical substrate.
FIG. 4 is a diagram showing crystal axes of quartz.
FIG. 5 is a diagram illustrating a path through which a surface acoustic wave propagates.
FIG. 6 is a plan view of a comb electrode of the surface acoustic wave device according to the first embodiment of the invention.
7 is a diagram showing a surface acoustic wave waveform measured by the surface acoustic wave device of FIG. 1; FIG.
FIG. 8 is a modified plan view of a modification of the comb electrode of FIG. 6;
FIG. 9 is a plan view of a photomask hole of a comb electrode.
FIG. 10 is a perspective view of a base of a surface acoustic wave element according to a second embodiment of the invention.
11 is a cross-sectional view of the base taken along the line L11-L11 in FIG.
FIG. 12 is a perspective view of a base of a surface acoustic wave element according to a third embodiment of the invention.
[Explanation of symbols]
110 Substrate
111 toroidal surface
121 base
123 Comb electrode
210 Base material
211 Annular surface
321 base

Claims (4)

And at least a portion of the spherical surface be formed Propelled by one of the annular surfaces are continuous in an annular shape, groups are formed by pressure-conductive material member,
A surface acoustic wave excitation means that is opposed to the annular surface at an interval and excites a surface acoustic wave that propagates along the annular surface ;
The equipped,
The surface acoustic wave excitation means includes a comb-shaped electrode provided along the annular surface and connected to a high-frequency power source,
The interval between the comb electrode and the annular surface is ¼ or less of the electrode period of the comb electrode.
A surface acoustic wave device. 2. The surface acoustic wave device according to claim 1, wherein the base material is formed of a single crystal selected from the group consisting of a single crystal of crystal, a single crystal of LiNbO _{3, and} a single crystal of LiTaO _3. .   The surface acoustic wave device according to claim 1 or 2, wherein the surface acoustic wave excited by the surface acoustic wave excitation means has a wavelength of 1/10 or less of a radius of a spherical surface of the substrate. 4. The elastic surface according to claim 1 , wherein an overlapping width of the comb-shaped electrode is not more than half of a diameter of the spherical surface of the base material and not less than 1/100 of a radius of the spherical surface. Wave element.

Images