JP3659461B2

JP3659461B2 - High frequency measurement board

Info

Publication number: JP3659461B2
Application number: JP16216998A
Authority: JP
Inventors: 武宏奥道
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 1998-06-10
Filing date: 1998-06-10
Publication date: 2005-06-15
Anticipated expiration: 2018-06-10
Also published as: JPH11352172A

Description

【０００１】
【発明の属する技術分野】
本発明はマイクロストリップ線路を用いた半導体素子や半導体素子収納用パッケージ・回路基板のマイクロ波帯あるいはミリ波帯といった高周波における電気的特性の測定に使用される高周波測定用基板に関し、特に測定可能な周波数帯域を改善した広帯域で低損失な高周波測定用基板に関する。
【０００２】
【従来の技術】
マイクロ波帯あるいはミリ波帯といった高周波帯域における半導体素子や半導体素子収納用パッケージ・回路基板の電気的特性の測定評価においては、測定器側には、コプレーナ線路との接触により高確度測定を可能としたウェハプローブが用いられる。一方、高周波信号を用いる無線通信機器用等の高速ディジタル回路や高周波回路もしくは高周波用半導体素子やそれを収容する高周波用半導体素子収納用パッケージ等の被測定物側の入出力部分の伝送線路はマイクロストリップ線路が一般的である。このために、ウェハプローブを用いた高周波における電気的特性の測定にはウェハプローブのコプレーナ線路と被測定物のマイクロストリップ線路との接続を行なう線路変換部を設ける必要があり、この線路変換部には被測定物の特性を高確度に抽出するために低損失に高周波信号の伝送を行なうことが要求される。
【０００３】
従来、この線路変換部の構造としては、一般にはコプレーナ線路部の信号導体幅ならびにグランド導体幅はウェハプローブのヘッドが要求する寸法に対応するように適切に設計され、その一端とマイクロストリップ線路の一端とを相互の信号導体幅が滑らかに変化するように接続しており、コプレーナ線路の接地（グランド）導体はマイクロストリップ線路の裏面の接地導体とスルーホール導体あるいはビアホール導体といった貫通導体を介して接続する構成であった。
【０００４】
例えば、図８に従来の線路変換部の構造の例を平面図で示すように、比誘電率が9.6 の誘電体基板１の裏面のほぼ全面に導体膜を被着形成して接地導体とし、マイクロストリップ線路部の信号導体２の幅を190 μｍ、コプレーナ線路部の信号導体３の幅を160 μｍ、コプレーナ線路部の信号導体３と接地導体４および４’との間隔を135 μｍとし、コプレーナ線路部の接地導体４・４’を貫通導体である各々直径150 μｍのスルーホール導体５および５’を介して裏面の接地導体と電気的に接続した構造のものが用いられる。そして、このようにスルーホールパッド構造としたコプレーナ線路部の接地導体を全く同一形状でマイクロストリップ線路部を介して鏡像対称に対向させたものの電気的特性を測定により抽出すると、図９に線図で示すような周波数特性が得られる。
【０００５】
図９において、横軸は周波数（単位：ＧＨｚ）、縦軸は入力した信号のうちの伝送された量の評価指標としての透過係数（単位：ｄＢ）を示しており、特性曲線は透過係数の周波数特性を示している。この結果から、周波数が高くなるに従って透過係数が小さくなり、信号の透過量が減少することが分かる。
【０００６】
また、上記のようにスルーホール導体あるいはビアホール導体といった貫通導体を介さずにコプレーナ線路とマイクロストリップ線路を線路変換して高周波測定用基板として構成したものに、実用新案登録第2507797 号「マイクロストリップライン回路測定治具」がある。同号公報によれば、図10に平面図で示すように、その測定治具（測定用基板）10は、裏面に地導体を有する誘電体基板11上のマイクロストリップ線路12の先端をステップ状またはテーパ状に形成してその幅をプローブヘッド13の中心導体幅に一致させて接続し、また、その先端近傍に半円状または半円に近い扇形のラジアルスタブ14による等価的グランドを形成してプローブヘッド13の２つのグランドラインの導体に対応させ、かつラジアルスタブ14のスタブ半径を測定周波数の下限の約１／２波長の実効長とする構成であった。
【０００７】
そして、このような構成によれば、プローブヘッド13と測定治具10の結合にリボンボンディングや上記の貫通導体のように変動する要素での接地導体間の接続手段が介在しないので、測定データの良好な再現性が得られるというものである。
【０００８】
この半円状または扇形のラジアルスタブ14による等価的グランドの原理は、高周波回路における一般的なラジアルスタブの現象と等価であるといえる。
【０００９】
すなわち、この内容はIEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL.36, NO.7, JULY 1988 " A Coplanar Probe to Microstrip Transition " に基づくと、図11に平面図で示したような形状のラジアルスタブ15のリアクタンス値は、このラジアルスタブ15が形成されている基板の厚みとラジアルスタブ15の内径と外径・ラジアルの中心角・ラジアルを径方向へ伝搬する場合の実効比誘電率・自由空間波長として次式で表わされる。
【００１０】
【数１】

【００１１】
【数２】

【００１２】
【数３】

【００１３】
【数４】

【００１４】
【数５】

【００１５】
ここで、Ｊ_i（ｘ），Ｎ_i（ｘ）はｉ次のベッセル関数である。
【００１６】
このような原理でラジアルスタブは高周波における動作が完全反射状態に近くなって等価的なグランドとみなせるという効果があることから高周波測定用基板における等価的グランドとしての応用が可能であり、実用新案登録第2507797 号のラジアルスタブ14はそのような効果を用いているものである。
【００１７】
次に、このようなラジアルスタブによる高周波測定用基板の特性を抽出する。
【００１８】
図５はラジアルスタブを用いた従来の高周波測定用基板の例を示す平面図であり、比誘電率が9.6 の誘電体基板21の裏面のほぼ全面に接地導体としての金属膜を被着形成し、表面にマイクロストリップ線路の信号導体22、コプレーナ線路の信号導体23および23’を形成し、コプレーナ線路の接地導体24および24’を信号導体23・23’から135 μｍの間隔を設けて設置し、接地導体24および24’はそれぞれ内径215 μｍ・外径580 μｍ・中心角230 °の扇形のラジアルスタブとして形成している。
【００１９】
この高周波用基板の電気的特性を測定により抽出すると、図６および図７にそれぞれ線図で示す結果が得られた。
【００２０】
図６において、横軸は周波数（単位：ＧＨｚ）、縦軸は入力した信号のうちの反射された量の評価指標としての反射係数（単位：ｄＢ）を示しており、特性曲線の内の実線はシミュレーションの結果を、破線は実測値をそれぞれ示している。また、図７において、横軸は周波数（単位：ＧＨｚ）、縦軸は入力した信号のうちの伝送された量の評価指標としての透過係数（単位：ｄＢ）を示しており、特性曲線の内の実線はシミュレーションの結果を、破線は実測値をそれぞれ示している。これらの結果から、ラジアルスタブを等価的なグランドとして用いることにより、低損失な透過周波数帯域特性を有する高周波測定用基板が得られることが分かる。
【００２１】
【発明が解決しようとする課題】
しかしながら、上記のような従来の高周波測定用基板においては、図８に示したようなスルーホール導体やビアホール導体等の貫通導体を用いたものの場合には、マイクロ波帯さらにはミリ波帯という高い周波数帯域において貫通導体のインダクタンス成分によりグランドが不安定となってしまう結果、特性インピーダンスの不連続が生じ、入射信号に対して反射が増大し、高周波信号の透過量が減少するという問題点があった。
【００２２】
また、貫通導体の加工工程が必要であるために高周波測定用基板の高精度な製造が困難であるという問題点もあった。
【００２３】
また、図10や図５に示したように半円状または扇形のラジアルスタブによる等価的グランドを用いた場合には、半円状または扇形の径方向の略中心位置の周方向の長さが１波長の実効長に相当する周波数において、周方向の電荷分布が半円状または扇形の周方向の端部と中間部とで密度が高くなるという定在的分布となる結果、共振が生じてしまうという問題点があった。このためにこの共振周波数近傍においては等価的グランドの効果はほとんど生じなくなり、それによって特性インピーダンスが不連続となる結果、入射信号に対して反射が増大し、高周波信号の透過量が減少してしまうという問題点があった。
【００２４】
さらに、この共振周波数が低損失の透過周波数帯域内あるいはその近傍の周波数となる場合には、測定可能な周波数帯域の狭帯域化という悪影響を及ぼすという問題点もあった。
【００２５】
本発明は上記従来技術における問題点に鑑みてなされたものであり、その目的は、ラジアルスタブを等価的なグランドとして用いた高周波測定用基板において、ラジアルスタブの共振周波数を高周波側へ移動させることにより低損失透過周波数帯域を広帯域化した高周波測定用基板を提供することにある。
【００２６】
【課題を解決するための手段】
本発明の高周波測定用基板は、誘電体基板の下面の略全面に接地導体が形成され、上面にマイクロストリップ線路の信号導体と、該信号導体の先端近傍に設けた、信号導体の中心線に対して線対称な２つの略扇面形のラジアルスタブによる等価的接地導体とが形成されて成り、前記信号導体と等価的接地導体とにそれぞれコプレーナ線路構造のウェハプローブの信号導体と接地導体とを電気的に接続させる高周波測定用基板であって、前記略扇面形の等価的接地導体は、前記信号導体側の第１の側辺および他方側の第２の側辺の長さが外周の円弧の長さよりも短く径方向に沿った形状であり、前記信号導体側の第１の側辺と前記信号導体の中心線の延長方向とのなす角度をθ_１、他方側の第２の側辺と前記信号導体の中心線の延長方向とのなす角度をθ_２としたとき、90°≦θ_１≦180°かつ３／８≦θ_２／θ_１≦５／８であることを特徴とするものである。
【００２７】
また、本発明の高周波測定用基板は、上記構成において、前記２つの略扇面形の等価的接地導体の中心が同心であり、前記２つの等価的接地導体は、前記第１の側辺の延長線と前記第２の側辺の延長線との交点を中心とし、前記第１の側辺およびその延長線と前記第２の側辺およびその延長線とを半径とし、外周を円弧とする扇面形であることを特徴とするものである。
【００２８】
【発明の実施の形態】
本発明の高周波測定用基板によれば、コプレーナ線路構造のウェハプローブの接地導体と接触させて電気的に接続させるために誘電体基板上面に形成するラジアルスタブによる等価的接地導体を、信号導体の中心線に対して線対称な２つの、信号導体側の第１の側辺および他方側の第２の側辺の長さが外周の円弧の長さよりも短く径方向に沿った略扇面形の形状に形成し、その略扇面形の等価的接地導体の２つの側辺について、信号導体側の元側の第１の側辺と信号導体の中心線の先端側への延長方向とのなす角度をθ_１とし、他方側すなわち信号導体の先端側の第２の側辺と信号導体の中心線の延長方向とのなす角度をθ_２としたときに、90°≦θ_１≦180°かつ３／８≦θ_２／θ_１≦５／８としたことにより、略扇面形の等価的接地導体における周方向の定在的な電荷密度分布が、図５に示したような従来の扇形のラジアルスタブによる等価的接地導体に比べて、より高周波側の周波数で生じることとなる。
【００２９】
そのため、従来のようなラジアルスタブによる等価的接地導体において半円形または扇形の径方向の略中心位置の周方向の長さが１波長の実効長に相当する周波数が低損失な透過周波数帯域内の周波数となる場合に周方向の電荷分布が半円形または扇形の周方向の端部と中間部とで密度が高くなるという定在的分布となって共振が生じてしまう場合と比較して、共振周波数を低損失な透過周波数帯域の高周波側へ移動することができる。その結果、低損失な透過周波数帯域が広がることとなるので、広帯域に低損失な特性を有する高周波測定用基板となる。
【００３０】
また、誘電体基板上に形成された略扇面形のラジアルスタブによる等価的接地導体において、前記の角度θ₁およびθ₂の関係がθ₂／θ₁＜３／８の場合には、略扇面形においてその径方向の中央付近での周方向の長さが１波長の実効長に相当する周波数が低損失な透過周波数帯域内の周波数となる場合に、周方向の電荷分布が略扇面形の周方向の端部と中間部とで密度が高くなるという定在的分布となって生じる共振が低損失な透過周波数帯域内に存在する問題がある。他方、θ₂／θ₁＞５／８の場合には、低損失な透過周波数帯域での伝搬損失が増加するという問題がある。従って、３／８≦θ₂／θ₁≦５／８とすることによりこれらの問題をなくすことができ、その結果、低損失な透過周波数帯域を広く確保することとなるので、広帯域に低損失な特性を有する高周波測定用基板となる。
【００３１】
なお、θ₁を90°≦θ₁≦180 °とするのは、２つのラジアルスタブの等価的接地導体間の容量的結合（干渉）を極力抑えるためであり、また、ウェハプローブの接触において支障のない構造とするためである。
【００３２】
また、上記構成の本発明の高周波測定用基板において、２つの略扇面形のラジアルスタブによる等価的接地導体の中心、すなわち、図１（ｃ）に一点鎖線で示す第１の側辺の延長線と図１（ｃ）に同じく一点鎖線で示す第２の側辺の延長線との交点を中心とし、第１の側辺およびその延長線と第２の側辺およびその延長線とを半径とし、外周を円弧とする扇面形の中心を同心とした場合には、略扇面形の等価的接地導体における周方向の定在的な電荷密度分布が、より高周波側の周波数で生じることとなる。
【００３３】
そのため、従来のようなラジアルスタブによる等価的接地導体において半円形または扇形の径方向の略中心位置の周方向の長さが１波長の実効長に相当する周波数が低損失な透過周波数帯域内の周波数となる場合に周方向の電荷分布が半円形または扇形の周方向の端部と中間部とで密度が高くなるという定在的分布となって共振が生じてしまう場合と比較して、共振周波数を低損失な透過周波数帯域の高周波側へ移動することができる。その結果、低損失な透過周波数帯域が広がることとなるので、広帯域に低損失な特性を有する高周波測定用基板となる。
【００３４】
以下、図面に基づいて本発明を詳細に説明する。
【００３５】
図１（ａ）〜（ｃ）は、それぞれ本発明の高周波測定用基板の実施の形態の例を示す平面図である。これらの図において、31は裏面（下面）の略全面に接地導体を被着形成した誘電体基板であり、32は誘電体基板31の表面（上面）に形成されたマイクロストリップ線路の信号導体である。33はコプレーナ線路部の信号導体であり、マイクロストリップ線路の信号導体32とは電気的に接続されて信号導体32の先端となっていて、コプレーナ線路構造のウェハプローブ（図示せず）の信号導体をマイクロストリップ線路の信号導体32に接触させて電気的に接続させる部分に相当する。
【００３６】
34および34’はマイクロストリップ線路の信号導体32の先端近傍に設けた等価的接地導体であり、信号導体32の中心線に対して線対称な２つの略扇面形としたラジアルスタブ形状の導体パターンにより形成されている。この等価的接地導体34・34’の形状・寸法・位置等は従来のラジアルスタブと同様に設定され、特に、内周の形状については完全な扇面形をなす円弧状には限らず、所望の高周波的な特性を満たすようにマイクロストリップ線路の信号導体32の先端形状やコプレーナ線路部の信号導体33の形状に合わせて、両端部を延長する等して適宜設定される。
【００３７】
ここで、図１（ａ）は、２つの等価的接地導体34・34’をそれぞれの中心が信号導体32の先端である信号導体33の両側に位置するように配置して形成した例を、図１（ｂ）は、図１（ａ）に対して２つの等価的接地導体34・34’を信号導体32・33の先端側にずらせて配置して形成した例を、図１（ｃ）は、２つの等価的接地導体34・34’の中心を同心とし、その中心が信号導体33上に位置するように配置して形成した例を示している。このように２つの等価的接地導体34・34’の配置については、図１（ｃ）の２つの等価的接地導体34・34’をその中心が信号導体33のさらに先の位置にくるように配置するなど種々の位置関係に設定し得るものであり、これら２つの等価的接地導体34・34’と信号導体33とに電気的に接続させるコプレーナ線路構造のウェハプローブとが接触できるような範囲において、測定の仕様等に応じて適宜設定すればよい。
【００３８】
そして、これらの図に示すように、略扇面形の等価的接地導体34の信号導体32側すなわち信号導体32の元側の第１の側辺と信号導体32・33の中心線の延長方向とのなす角度、すなわち信号導体32・33の中心線の先端方向へ延長した側から見た第１の側辺までの角度をθ₁とし、他方側すなわち信号導体32・33の先端側の第２の側辺と信号導体32・33の中心線の延長方向とのなす角度、すなわち信号導体32・33の中心線の先端方向へ延長した側から見た第１の側辺までの角度をθ₂としたときに、90°≦θ₁≦180 °かつ３／８≦θ₂／θ₁≦５／８としたことが本発明の高周波測定用基板の特徴であり、これにより、前述のように広帯域に低損失な特性を有する高周波測定用基板とすることができる。
【００３９】
なお、これらθ₁・θ₂については等価的接地導体34と線対称に形成されたもう一方の等価的接地導体34’についても同様であることはいうまでもない。
【００４０】
また、等価的接地導体34・34' の寸法や形状・位置等は、高周波的に悪影響を与えずかつ透過周波数帯域よりも低周波側の周波数で定在的な電荷密度分布が生じるように適宜設定すればよく、例えば、裏面の接地導体との高周波的な結合を極力強く（多く）することによって広帯域となるために、ラジアル角を大きくとることから、その幅は径方向の長さよりも短くして径方向に沿った形状となるようにする。
【００４１】
【実施例】
次に、本発明の高周波測定用基板について具体例を説明する。
【００４２】
まず、比誘電率が9.6のアルミナセラミックスから成る誘電体基板31に対して裏面のほぼ全面にわたる金属膜を被着形成した。また、誘電体基板31の上面にマイクロストリップ線路の信号導体32を形成し、その先端にコプレーナ線路部33を信号導体の中心から接地導体までの距離を105μｍとして形成し、マイクロストリップ線路の信号導体32の先端と電気的に接続した。さらに、コプレーナ線路部の信号導体33（マイクロストリップ線路の信号導体32の先端）の近傍に信号導体の幅方向の中点を中心として、内径105μｍ・外径400μｍ・中心角65°の扇面形のラジアルスタブをθ_２が65°（θ_１＝130°）となる様に等価的接地導体34および34'として形成することにより、図１（ｃ）に示すような、本発明の高周波測定用基板の試料を作製した。ここで、等価的接地導体34・34’の中心角が異なることによる特性の比較を行なうために、θ_１を130°で一定としてθ_２を以下の通りに設定して、それぞれ試料Ａ〜試料Ｊを作製した。
【００４３】
試料名 θ₂
Ａ・・・45°
Ｂ・・・50°
Ｃ・・・55°
Ｄ・・・60°
Ｅ・・・65°
Ｆ・・・70°
Ｇ・・・75°
Ｈ・・・80°
Ｉ・・・85°
Ｊ・・・90°
そして、これら試料Ａ〜試料Ｊについて、電磁界シミュレーションにより、マイクロストリップ線路のコプレーナ線路に接続しない端部からコプレーナ線路のマイクロストリップ線路に接続しない端部への周波数に応じた特性を抽出し、抽出した特性から、入力した信号のうちの伝送された量の評価指標として透過係数（Ｓ₂₁）を周波数に対する伝送特性として求めた。
【００４４】
また、試料Ａ〜試料Ｅの伝送特性の比較として、図２に各々の反射係数Ｓ₂₁の周波数特性を線図で示す。図２において横軸は周波数（単位：ＧＨｚ）、縦軸は透過量（単位：ｄＢ）を表わしている。
【００４５】
また、試料Ｅ〜試料Ｊの伝送特性の比較として、図３に各々の透過係数Ｓ₂₁の周波数特性を線図で示す。図３において横軸は周波数（単位：ＧＨｚ）、縦軸は透過量（単位：ｄＢ）を表わしている。
【００４６】
これらより分かるように、本発明の高周波測定用基板である試料Ｂ〜試料Ｈは、誘電体基板の下面の略全面に接地導体が形成され、上面にマイクロストリップ線路の信号導体と、この信号導体の先端近傍に設けた、信号導体の中心線に対して線対称な２つの略扇面形のラジアルスタブによる等価的接地導体とが形成されて成り、前記信号導体と等価的接地導体とにそれぞれコプレーナ線路構造のウェハプローブの信号導体と接地導体とを電気的に接続させる高周波測定用基板であって、略扇面形の等価的接地導体は、信号導体側の第１の側辺と信号導体の中心線の延長方向とのなす角度をθ₁、他方側の第２の側辺と信号導体の中心線の延長方向とのなす角度をθ₂としたとき、90°≦θ₁≦180 °かつ３／８≦θ₂／θ₁≦５／８であることにより、等価的接地導体におけるリアクタンス値が小さくなるために、低損失透過周波数帯域を広帯域化できている。
【００４７】
なお、θ₂／θ₁＜３／８である試料Ａは、略扇面形の径方向の略中心位置の周方向の長さが１波長の実効長に相当する周波数が低損失な透過周波数帯域内の周波数となる場合に周方向の電荷分布が半円形または扇形の周方向の端部と中間部とで密度が高くなるという定在的分布となって生じる共振が低損失な透過周波数帯域内に存在することによる狭帯域化が問題として残されている。また、θ₂／θ₁＞５／８である試料Ｉおよび試料Ｊは、低損失な透過周波数帯域での伝搬損失が増加するという問題が残されている。さらに、３／８≦θ₂／θ₁≦５／８の試料の内では試料Ｅが最も良い。
【００４８】
ここで、試料Ｅのみの伝送特性として、図４に反射係数Ｓ₁₁および透過係数Ｓ₂₁の周波数特性を線図で示す。図４において横軸は周波数（単位：ＧＨｚ）、縦軸は反射量（単位：ｄＢ）および透過量（単位：ｄＢ）を表わしている。図４より、低損失な透過周波数帯域を従来のラジアルスタブによる等価的接地導体を用いたものと比較して大幅に広くすることができ、高確度な測定系として応用することが可能であることが分かる。
【００４９】
これにより、本発明の高周波測定用基板によれば、２つの略扇面形のラジアルスタブによる等価的接地導体におけるリアクタンス値が小さくなる結果、低損失な透過周波数帯域を広く確保することとなるので、広帯域に低損失な特性を有する高周波測定用基板とすることができることが確認できた。
【００５０】
なお、以上はあくまで本発明の実施の形態の例示であって、本発明はこれらに限定されるものではなく、本発明の要旨を逸脱しない範囲で種々の変更や改良を加えることは何ら差し支えない。
【００５１】
【発明の効果】
以上のように、本発明の高周波測定用基板によれば、コプレーナ線路構造のウェハプローブの接地導体と接触させて電気的に接続させるために誘電体基板上面に形成するラジアルスタブによる等価的接地導体を、信号導体の中心線に対して線対称な２つの、信号導体側の第１の側辺および他方側の第２の側辺の長さが外周の円弧の長さよりも短く径方向に沿った略扇面形の形状に形成し、その略扇面形の等価的接地導体の２つの側辺について、信号導体側の元側の第１の側辺と信号導体の中心線の先端側への延長方向とのなす角度をθ_１とし、他方側すなわち信号導体の先端側の第２の側辺と信号導体の中心線の延長方向とのなす角度をθ_２としたときに、90°≦θ_１≦180°かつ３／８≦θ_２／θ_１≦５／８としたことにより、略扇面形の等価的接地導体における周方向の定在的な電荷密度分布が従来の扇形のラジアルスタブによる等価的接地導体に比べてより高周波側の周波数で生じることとなる。そのため、従来のようなラジアルスタブによる等価的接地導体において半円形または扇形の径方向の略中心位置の周方向の長さが１波長の実効長に相当する周波数が低損失な透過周波数帯域内の周波数となる場合に周方向の電荷分布が半円形または扇形の周方向の端部と中間部とで密度が高くなるという定在的分布となって共振が生じてしまう場合と比較して、共振周波数を低損失な透過周波数帯域の高周波側へ移動することができる。その結果、低損失な透過周波数帯域が広がることとなるので、広帯域に低損失な特性を有する高周波測定用基板とすることができた。
【００５２】
また、上記構成の本発明の高周波測定用基板において、２つの略扇面形のラジアルスタブによる等価的接地導体の中心、すなわち、第１の側辺の延長線と第２の側辺の延長線との交点を中心とし、第１の側辺およびその延長線と第２の側辺およびその延長線とを半径とし、外周を円弧とする扇面形の中心を同心とした場合には、略扇面形の等価的接地導体における周方向の定在的な電荷密度分布が、より高周波側の周波数で生じることとなる。そのため、従来のようなラジアルスタブによる等価的接地導体において半円形または扇形の径方向の略中心位置の周方向の長さが１波長の実効長に相当する周波数が低損失な透過周波数帯域内の周波数となる場合に周方向の電荷分布が半円形または扇形の周方向の端部と中間部とで密度が高くなるという定在的分布となって共振が生じてしまう場合と比較して、共振周波数をより低損失な透過周波数帯域の高周波側へ移動することができる。その結果、低損失な透過周波数帯域が広がることとなるので、広帯域に低損失な特性を有する高周波測定用基板とすることができた。
【００５３】
また、本発明の高周波測定用基板によれば、スルーホール導体やビアホール導体等の貫通導体を用いた従来の高周波測定用基板の場合のように高精度な基板加工工程を必要としないために、高精度な測定が可能な高周波測定用基板を容易かつ安価に提供できるものとなる。
【００５４】
以上により、本発明によれば、ラジアルスタブを等価的なグランドとして用いた高周波測定用基板において、誘電体基板の基板厚みを適切に設定することにより低損失透過周波数帯域を広帯域化した高周波測定用基板を提供することができた。
【図面の簡単な説明】
【図１】（ａ）〜（ｃ）は、それぞれ本発明の高周波測定用基板の実施の形態の例を示す平面図である。
【図２】高周波測定用基板における周波数に対する透過特性を示す線図である。
【図３】高周波測定用基板における周波数に対する透過特性を示す線図である。
【図４】高周波測定用基板における周波数に対する反射特性および透過特性を示す線図である。
【図５】従来の高周波測定用基板の例を示す平面図である。
【図６】高周波測定用基板における周波数に対する反射特性を示す線図である。
【図７】高周波測定用基板における周波数に対する透過特性を示す線図である。
【図８】従来の高周波測定用基板の例を示す平面図である。
【図９】高周波測定用基板における周波数に対する透過特性を示す線図である。
【図１０】従来の高周波測定用基板の例を示す平面図である。
【図１１】ラジアルスタブの例を示す平面図である。
【符号の説明】
31・・・・・・・・・・誘電体基板
32・・・・・・・・・・マイクロストリップ線路信号導体
33・・・・・・・・・・コプレーナ線路信号導体
34、34' ・・・・・・・等価的接地導体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency measurement substrate used for measuring electrical characteristics at a high frequency such as a microwave band or a millimeter-wave band of a semiconductor element using a microstrip line or a package / circuit board for housing a semiconductor element. The present invention relates to a broadband, low-loss, high-frequency measurement substrate with an improved frequency band.
[0002]
[Prior art]
When measuring and evaluating the electrical characteristics of semiconductor elements, semiconductor element storage packages and circuit boards in high frequency bands such as microwave band and millimeter wave band, high accuracy measurement is possible by contact with the coplanar line on the measuring instrument side. A wafer probe is used. On the other hand, the transmission line of the input / output portion on the measured object side such as a high-speed digital circuit for a radio communication device using a high-frequency signal, a high-frequency circuit or a high-frequency semiconductor element, or a high-frequency semiconductor element storage package for accommodating it A strip line is common. For this reason, it is necessary to provide a line converter for connecting the coplanar line of the wafer probe and the microstrip line of the object to be measured in order to measure the electrical characteristics at high frequency using the wafer probe. In order to extract the characteristics of the object to be measured with high accuracy, it is required to transmit a high-frequency signal with low loss.
[0003]
Conventionally, as the structure of this line conversion section, generally, the signal conductor width and the ground conductor width of the coplanar line section are appropriately designed to correspond to the dimensions required by the head of the wafer probe, One end is connected so that the mutual signal conductor width changes smoothly, and the ground (ground) conductor of the coplanar line is connected to the ground conductor on the back surface of the microstrip line and a through conductor such as a through-hole conductor or a via-hole conductor. It was a configuration to connect.
[0004]
For example, as shown in a plan view in FIG. 8 as an example of the structure of a conventional line converter, a conductor film is deposited on almost the entire back surface of a dielectric substrate 1 having a relative dielectric constant of 9.6 to form a ground conductor, The width of the signal conductor 2 in the microstrip line portion is 190 μm, the width of the signal conductor 3 in the coplanar line portion is 160 μm, and the distance between the signal conductor 3 in the coplanar line portion and the

ground conductors

4 and 4 ′ is 135 μm. A structure in which the

ground conductors

4 and 4 ′ of the line portion are electrically connected to the ground conductor on the back surface through through-

hole conductors

5 and 5 ′ each having a diameter of 150 μm, which are through conductors, is used. Then, by extracting the electrical characteristics of the coplanar line portion ground conductor having the through-hole pad structure in exactly the same shape and facing each other mirror-symmetrically via the microstrip line portion, a diagram is shown in FIG. A frequency characteristic as shown in FIG.
[0005]
In FIG. 9, the horizontal axis indicates the frequency (unit: GHz), the vertical axis indicates the transmission coefficient (unit: dB) as an evaluation index of the transmitted amount of the input signal, and the characteristic curve indicates the transmission coefficient. The frequency characteristics are shown. From this result, it can be seen that as the frequency increases, the transmission coefficient decreases and the amount of signal transmission decreases.
[0006]
In addition, a utility model registration No. 2507797 “Microstrip line” is used as a high-frequency measurement board by converting the coplanar line and the microstrip line without passing through conductors such as through-hole conductors or via-hole conductors as described above. Circuit measurement jig ". According to the publication, as shown in a plan view in FIG. 10, the measuring jig (measuring substrate) 10 has a stepped end of a microstrip line 12 on a dielectric substrate 11 having a ground conductor on the back surface. Alternatively, it is tapered so that its width matches the center conductor width of the probe head 13, and an equivalent ground is formed by a semicircular or semicircular fan-shaped radial stub 14 near its tip. Thus, the stub radius of the radial stub 14 is made to correspond to the conductors of the two ground lines of the probe head 13 and the effective length of about ½ wavelength of the lower limit of the measurement frequency.
[0007]
According to such a configuration, there is no connection means between the ground conductors in the elements such as ribbon bonding and the above-described through conductors in the coupling between the probe head 13 and the measurement jig 10, so that the measurement data Good reproducibility is obtained.
[0008]
The principle of the equivalent ground by the semicircular or fan-shaped radial stub 14 can be said to be equivalent to a general radial stub phenomenon in a high-frequency circuit.
[0009]
That is, this content is based on IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL.36, NO.7, JULY 1988 "A Coplanar Probe to Microstrip Transition". The reactance value is the thickness of the substrate on which the radial stub 15 is formed, the inner diameter and outer diameter of the radial stub 15, the central angle of the radial, the effective relative dielectric constant when propagating in the radial direction, and the free space wavelength. It is expressed by the following formula.
[0010]
[Expression 1]

[0011]
[Expression 2]

[0012]
[Equation 3]

[0013]
[Expression 4]

[0014]
[Equation 5]

[0015]
Where J_i(X), N_i(X) is an i-th order Bessel function.
[0016]
Based on this principle, radial stubs can be used as equivalent grounds for high-frequency measurement boards because they can be regarded as equivalent grounds because the operation at high frequencies is close to a perfect reflection state. The 2507797 radial stub 14 uses such an effect.
[0017]
Next, the characteristics of the high-frequency measurement substrate using such a radial stub are extracted.
[0018]
FIG. 5 is a plan view showing an example of a conventional high-frequency measurement substrate using a radial stub, in which a metal film as a ground conductor is deposited on almost the entire back surface of a dielectric substrate 21 having a relative dielectric constant of 9.6. The signal conductor 22 of the microstrip line and the signal conductors 23 and 23 'of the coplanar line are formed on the surface, and the ground conductors 24 and 24' of the coplanar line are installed at a distance of 135 μm from the signal conductors 23 and 23 '. The ground conductors 24 and 24 'are formed as fan-shaped radial stubs each having an inner diameter of 215 μm, an outer diameter of 580 μm, and a central angle of 230 °.
[0019]
When the electrical characteristics of this high frequency substrate were extracted by measurement, the results shown in the diagrams in FIGS. 6 and 7 were obtained.
[0020]
In FIG. 6, the horizontal axis indicates the frequency (unit: GHz), and the vertical axis indicates the reflection coefficient (unit: dB) as an evaluation index of the reflected amount of the input signal. The solid line in the characteristic curve Indicates the simulation result, and the broken line indicates the actual measurement value. In FIG. 7, the horizontal axis indicates the frequency (unit: GHz), and the vertical axis indicates the transmission coefficient (unit: dB) as an evaluation index of the transmitted amount of the input signal. The solid line indicates the simulation result, and the broken line indicates the actual measurement value. From these results, it can be seen that a high-frequency measurement substrate having low-loss transmission frequency band characteristics can be obtained by using a radial stub as an equivalent ground.
[0021]
[Problems to be solved by the invention]
However, in the conventional high-frequency measurement substrate as described above, in the case where a through-hole conductor such as a through-hole conductor or a via-hole conductor as shown in FIG. 8 is used, the microwave band and the millimeter wave band are high. As a result of the unstable ground due to the inductance component of the through conductor in the frequency band, the characteristic impedance becomes discontinuous, the reflection increases with respect to the incident signal, and the transmission amount of the high-frequency signal decreases. It was.
[0022]
In addition, since a through conductor processing step is required, it is difficult to manufacture a high-frequency measurement substrate with high accuracy.
[0023]
Also, as shown in FIGS. 10 and 5, when an equivalent gland with a semicircular or fan-shaped radial stub is used, the circumferential length of the approximate center position in the radial direction of the semicircular or fan-shaped At a frequency corresponding to the effective length of one wavelength, the circumferential charge distribution becomes a standing distribution in which the density increases at the semicircular or fan-shaped circumferential end and middle, resulting in resonance. There was a problem of end. For this reason, the effect of the equivalent ground hardly occurs in the vicinity of this resonance frequency, and as a result, the characteristic impedance becomes discontinuous, resulting in an increase in reflection with respect to the incident signal and a decrease in the transmission amount of the high-frequency signal. There was a problem.
[0024]
Furthermore, when the resonance frequency is in the low-loss transmission frequency band or in the vicinity thereof, there is a problem that the measurable frequency band is narrowed.
[0025]
  The present invention has been made in view of the above-described problems in the prior art, and an object of the present invention is to move the resonance frequency of the radial stub to the high frequency side in a high frequency measurement substrate using the radial stub as an equivalent ground. Accordingly, an object of the present invention is to provide a high-frequency measurement substrate having a low loss transmission frequency band widened.
[0026]
[Means for Solving the Problems]
  The substrate for high frequency measurement of the present invention has a ground conductor formed on substantially the entire bottom surface of the dielectric substrate, a signal conductor of the microstrip line on the top surface, and a center line of the signal conductor provided near the tip of the signal conductor. An equivalent ground conductor is formed by two substantially fan-shaped radial stubs that are line-symmetric with respect to the signal conductor and the equivalent ground conductor. The signal conductor and the ground conductor of the wafer probe having a coplanar line structure are respectively connected to the signal conductor and the equivalent ground conductor. The high-frequency measurement board to be electrically connected, wherein the substantially fan-shaped equivalent ground conductor has an arc whose outer length is the length of the first side on the signal conductor side and the second side on the other side. The angle formed between the first side on the signal conductor side and the extending direction of the center line of the signal conductor is θ.₁, The angle formed between the second side of the other side and the extending direction of the center line of the signal conductor is θ₂90 ° ≦ θ₁≦ 180 ° and 3/8 ≦ θ₂/ Θ₁≦ 5/8.
[0027]
  In the high frequency measurement substrate of the present invention, in the configuration described above, the centers of the two substantially fan-shaped equivalent ground conductors are concentric, and the two equivalent ground conductors are extensions of the first side. A fan surface having an intersection between a line and an extension line of the second side as a center, a radius of the first side and its extension line, and the second side and its extension line, and an arc as an outer periphery It is characterized by its shape.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
  According to the high-frequency measurement substrate of the present invention, an equivalent ground conductor formed by a radial stub formed on the top surface of the dielectric substrate for contact with the ground conductor of the wafer probe having a coplanar line structure is electrically connected to the signal conductor. The length of the first side on the signal conductor side and the second side on the other side that are axisymmetric with respect to the center line is shorter than the length of the outer arc and is substantially fan-shaped along the radial direction. The angle formed between the first side on the signal conductor side and the extending direction to the front end side of the center line of the signal conductor with respect to the two sides of the substantially fan-shaped equivalent ground conductor Θ₁And the angle between the other side, that is, the second side on the front end side of the signal conductor, and the extending direction of the center line of the signal conductor is θ₂90 ° ≦ θ₁≦ 180 ° and 3/8 ≦ θ₂/ Θ₁By setting ≦ 5/8, the circumferential constant charge density distribution in the substantially fan-shaped equivalent ground conductor is larger than that of the equivalent fan-shaped radial ground stub shown in FIG. Therefore, it occurs at a higher frequency.
[0029]
Therefore, in a conventional equivalent grounding conductor using a radial stub, the frequency corresponding to the effective length of one wavelength in the circumferential direction at the substantially central position in the radial direction of the semicircular or fan shape is within the transmission frequency band where the loss is low. Resonance compared to the case where resonance occurs as a standing distribution in which the charge distribution in the circumferential direction increases in density in the semicircular or fan-shaped circumferential end and middle when the frequency is reached The frequency can be moved to the high frequency side of the low-loss transmission frequency band. As a result, a low-loss transmission frequency band is widened, so that a high-frequency measurement substrate having a low-loss characteristic in a wide band is obtained.
[0030]
Further, in an equivalent ground conductor formed by a substantially fan-shaped radial stub formed on a dielectric substrate, the angle θ₁And θ₂Is the relationship θ₂/ Θ₁In the case of <3/8, when the frequency corresponding to the effective length of one wavelength in the circumferential direction near the center in the radial direction in a substantially fan shape is a frequency within the transmission frequency band with low loss. However, there is a problem in that resonance that occurs as a standing distribution in which the density of the circumferential charge distribution becomes higher at the end portion and the middle portion of the substantially fan-shaped circumferential direction exists in the low-loss transmission frequency band. On the other hand, θ₂/ Θ₁In the case of> 5/8, there is a problem that the propagation loss increases in the low-loss transmission frequency band. Therefore, 3/8 ≦ θ₂/ Θ₁By setting .ltoreq.5 / 8, these problems can be eliminated. As a result, a wide low-loss transmission frequency band can be secured, so that a high-frequency measurement substrate having a low-loss characteristic in a wide band is obtained.
[0031]

Θ

₁90 ° ≦ θ₁The reason why ≦ 180 ° is to suppress the capacitive coupling (interference) between the equivalent ground conductors of the two radial stubs as much as possible, and to make the structure free from trouble in contact with the wafer probe.
[0032]
Further, in the high-frequency measurement substrate of the present invention having the above-described configuration, the center of an equivalent ground conductor by two substantially fan-shaped radial stubs, that is, an extension line of the first side indicated by a one-dot chain line in FIG. And the center of the intersection with the extension line of the second side indicated by the alternate long and short dash line in FIG. 1C, and the radius of the first side and its extension line and the second side and its extension line. In the case where the center of the fan-shaped shape having the outer periphery as an arc is concentric, a constant charge density distribution in the circumferential direction in the substantially ground-shaped equivalent ground conductor is generated at a higher frequency.
[0033]
Therefore, in a conventional equivalent grounding conductor using a radial stub, the frequency corresponding to the effective length of one wavelength in the circumferential direction at the substantially central position in the radial direction of the semicircular or fan shape is within the transmission frequency band where the loss is low. Resonance compared to the case where resonance occurs as a standing distribution in which the charge distribution in the circumferential direction increases in density in the semicircular or fan-shaped circumferential end and middle when the frequency is reached The frequency can be moved to the high frequency side of the low-loss transmission frequency band. As a result, a low-loss transmission frequency band is widened, so that a high-frequency measurement substrate having a low-loss characteristic in a wide band is obtained.
[0034]
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0035]
FIGS. 1A to 1C are plan views showing examples of embodiments of the high-frequency measurement substrate of the present invention. In these figures, 31 is a dielectric substrate having a ground conductor deposited on substantially the entire back surface (lower surface), and 32 is a signal conductor of a microstrip line formed on the surface (upper surface) of the dielectric substrate 31. is there. Reference numeral 33 denotes a signal conductor of the coplanar line portion, which is electrically connected to the signal conductor 32 of the microstrip line and serves as a tip of the signal conductor 32, and is a signal conductor of a wafer probe (not shown) having a coplanar line structure. Corresponds to a portion to be brought into contact with and electrically connected to the signal conductor 32 of the microstrip line.
[0036]
34 and 34 'are equivalent ground conductors provided in the vicinity of the tip of the signal conductor 32 of the microstrip line, and two substantially fan-shaped radial stub-shaped conductor patterns axisymmetric with respect to the center line of the signal conductor 32 It is formed by. The shape, dimensions, position, etc. of the equivalent grounding conductors 34, 34 'are set in the same manner as the conventional radial stub. In particular, the shape of the inner periphery is not limited to the arc shape that forms a complete fan surface, but is desired. In accordance with the shape of the tip of the signal conductor 32 of the microstrip line and the shape of the signal conductor 33 of the coplanar line portion so as to satisfy the high frequency characteristics, the both ends are set as appropriate.
[0037]
Here, FIG. 1A shows an example in which two equivalent ground conductors 34 and 34 'are arranged so that their centers are located on both sides of the signal conductor 33 which is the tip of the signal conductor 32. FIG. 1B shows an example in which two

equivalent ground conductors

34 and 34 ′ are shifted from the front end side of the

signal conductors

32 and 33 with respect to FIG. Shows an example in which the centers of two

equivalent ground conductors

34 and 34 ′ are concentric and arranged so that the centers thereof are located on the signal conductor 33. Thus, with respect to the arrangement of the two equivalent ground conductors 34 and 34 ', the two equivalent ground conductors 34 and 34' in FIG. It can be set in various positional relations such as being arranged, and the range in which the wafer probe of the coplanar line structure that is electrically connected to these two equivalent ground conductors 34 and 34 'and the signal conductor 33 can be in contact with each other. In this case, it may be set as appropriate according to the measurement specifications.
[0038]
As shown in these drawings, the first side of the signal conductor 32 side of the substantially fan-shaped equivalent ground conductor 34, that is, the original side of the signal conductor 32, and the extending direction of the center line of the

signal conductors

32 and 33, , That is, the angle from the side extending toward the tip of the center line of the

signal conductors

32 and 33 to the first side as viewed from θ.₁The angle formed by the other side, that is, the second side of the

signal conductors

32 and 33 on the tip side and the extending direction of the center line of the

signal conductors

32 and 33, that is, the

signal conductors

32 and 33 extend toward the tip of the center line The angle to the first side as seen from the angled side is θ₂90 ° ≦ θ₁≦ 180 ° and 3/8 ≦ θ₂/ Θ₁≦ 5/8 is a feature of the high-frequency measurement substrate of the present invention, and as a result, a high-frequency measurement substrate having a low loss characteristic in a wide band as described above can be obtained.
[0039]
These θ₁・ Θ₂Needless to say, the same applies to the other equivalent ground conductor 34 'formed in line symmetry with the equivalent ground conductor 34.
[0040]
Also, the dimensions, shape, position, etc. of the equivalent ground conductors 34, 34 'are appropriately set so that a stationary charge density distribution is generated at a frequency lower than the transmission frequency band without adversely affecting the high frequency. For example, since a wide band is obtained by strengthening (highly) high-frequency coupling with the ground conductor on the back surface as much as possible, the radial angle is increased, so the width is shorter than the radial length. Thus, a shape along the radial direction is obtained.
[0041]
【Example】
Next, specific examples of the high-frequency measurement substrate of the present invention will be described.
[0042]
  First, a metal film covering almost the entire back surface was deposited on a dielectric substrate 31 made of alumina ceramic having a relative dielectric constant of 9.6. In addition, a microstrip line signal conductor 32 is formed on the upper surface of the dielectric substrate 31, and a coplanar line portion 33 is formed at the tip thereof with a distance from the center of the signal conductor to the ground conductor being 105 μm. Electrically connected to 32 tips. Furthermore, in the vicinity of the signal conductor 33 of the coplanar line section (the tip of the signal conductor 32 of the microstrip line), a fan-shaped surface having an inner diameter of 105 μm, an outer diameter of 400 μm, and a central angle of 65 ° centered on the midpoint of the width of the signal conductor. The radial stub is θ₂Is 65 ° (θ₁= 130 °) as equivalent ground conductors 34 and 34 ', a sample of the high-frequency measurement substrate of the present invention as shown in FIG. 1 (c) was produced. Here, in order to compare the characteristics due to the difference in the central angles of the equivalent ground conductors 34 and 34 ', θ₁Θ is constant at 130 °₂Were set as follows to prepare Sample A to Sample J, respectively.
[0043]
Sample name θ₂
A ... 45 °
B ... 50 °
C ... 55 °
D ... 60 °
E ... 65 °
F ... 70 °
G ... 75 °
H ... 80 °
I ... 85 °
J ... 90 °
For these samples A to J, the characteristics corresponding to the frequency from the end of the microstrip line not connected to the coplanar line to the end of the coplanar line not connected to the microstrip line are extracted and extracted by electromagnetic field simulation. The transmission coefficient (S) is used as an evaluation index of the transmitted amount of the input signal._{twenty one}) As a transmission characteristic with respect to frequency.
[0044]
In addition, as a comparison of the transmission characteristics of sample A to sample E, FIG._{twenty one}The frequency characteristics are shown in a diagram. In FIG. 2, the horizontal axis represents the frequency (unit: GHz), and the vertical axis represents the transmission amount (unit: dB).
[0045]
As a comparison of the transmission characteristics of sample E to sample J, FIG._{twenty one}The frequency characteristics are shown in a diagram. In FIG. 3, the horizontal axis represents frequency (unit: GHz), and the vertical axis represents transmission amount (unit: dB).
[0046]
As can be seen from the above, the sample B to sample H, which are high-frequency measurement substrates of the present invention, have a ground conductor formed on substantially the entire bottom surface of the dielectric substrate, a signal conductor of a microstrip line on the top surface, and this signal conductor. Formed in the vicinity of the front end of the signal conductor, and is formed by two substantially fan-shaped radial stubs that are line-symmetric with respect to the center line of the signal conductor, and each of the signal conductor and the equivalent ground conductor is coplanar. A high-frequency measurement board for electrically connecting a signal conductor and a ground conductor of a wafer probe having a line structure, wherein the substantially fan-shaped equivalent ground conductor includes a first side on the signal conductor side and a center of the signal conductor. The angle between the line extension direction and θ₁, The angle formed between the second side of the other side and the extending direction of the center line of the signal conductor is θ₂90 ° ≦ θ₁≦ 180 ° and 3/8 ≦ θ₂/ Θ₁By satisfying ≦ 5/8, the reactance value in the equivalent ground conductor is reduced, so that the low-loss transmission frequency band can be widened.
[0047]
Θ₂/ Θ₁In the case of sample A that is <3/8, when the length in the circumferential direction of the substantially central position in the radial direction of the substantially fan-shaped surface is a frequency in the transmission frequency band with a low loss, the frequency corresponding to the effective length of one wavelength Narrow band due to the presence of resonance in the low-loss transmission frequency band where the circumferential charge distribution becomes a semi-circular or fan-shaped density distribution at the circumferential end and middle. Remains a problem. And θ₂/ Θ₁Sample I and sample J, which are> 5/8, have a problem that propagation loss increases in a low-loss transmission frequency band. 3/8 ≦ θ₂/ Θ₁Among the samples of ≦ 5/8, the sample E is the best.
[0048]
Here, as a transmission characteristic of only the sample E, the reflection coefficient S is shown in FIG.₁₁And transmission coefficient S_{twenty one}The frequency characteristics are shown in a diagram. In FIG. 4, the horizontal axis represents frequency (unit: GHz), and the vertical axis represents reflection amount (unit: dB) and transmission amount (unit: dB). As shown in FIG. 4, the low-loss transmission frequency band can be significantly widened compared to a conventional radial stub equivalent ground conductor and can be applied as a highly accurate measurement system. I understand.
[0049]
Thereby, according to the high-frequency measurement substrate of the present invention, the reactance value in the equivalent ground conductor by the two substantially fan-shaped radial stubs is reduced, so that a low-loss transmission frequency band is widely secured. It was confirmed that a high frequency measurement substrate having a low loss characteristic in a wide band can be obtained.
[0050]
Note that the above are merely examples of the embodiments of the present invention, and the present invention is not limited to these embodiments, and various modifications and improvements may be made without departing from the scope of the present invention. .
[0051]
【The invention's effect】
  As described above, according to the high-frequency measurement substrate of the present invention, the equivalent ground conductor formed by the radial stub formed on the top surface of the dielectric substrate in order to be in contact with and electrically connected to the ground conductor of the wafer probe having the coplanar line structure. The lengths of the first side on the signal conductor side and the second side on the other side that are axisymmetric with respect to the center line of the signal conductor are shorter than the length of the outer arc and along the radial direction. The two sides of the substantially fan-shaped equivalent ground conductor are extended from the first side on the signal conductor side to the front end side of the center line of the signal conductor. The angle between the direction and θ₁And the angle between the other side, that is, the second side on the front end side of the signal conductor, and the extending direction of the center line of the signal conductor is θ₂90 ° ≦ θ₁≦ 180 ° and 3/8 ≦ θ₂/ Θ₁By setting ≦ 5/8, the peripheral charge density distribution in the substantially fan-shaped equivalent ground conductor is generated at a higher frequency than the equivalent ground conductor of the conventional fan-shaped radial stub. It will be. Therefore, in a conventional equivalent grounding conductor using a radial stub, the frequency corresponding to the effective length of one wavelength in the circumferential direction at the substantially central position in the radial direction of the semicircular or fan shape is within the transmission frequency band where the loss is low. Resonance compared to the case where resonance occurs as a standing distribution in which the charge distribution in the circumferential direction increases in density in the semicircular or fan-shaped circumferential end and middle when the frequency is reached The frequency can be moved to the high frequency side of the low-loss transmission frequency band. As a result, a low-loss transmission frequency band is widened, so that a high-frequency measurement substrate having a low-loss characteristic in a wide band can be obtained.
[0052]
  Further, in the high-frequency measurement substrate of the present invention configured as described above, the center of an equivalent ground conductor by two substantially fan-shaped radial stubs, that is, an extension line of the first side and an extension line of the second side The first side and its extension line and the second side and its extension line as the radius.,In the case where the center of the fan-shaped shape having an arc on the outer periphery is concentric, a stationary charge density distribution in the circumferential direction of the substantially fan-shaped equivalent ground conductor is generated at a higher frequency. Therefore, in a conventional equivalent grounding conductor using a radial stub, the frequency corresponding to the effective length of one wavelength in the circumferential direction at the substantially central position in the radial direction of the semicircular or fan shape is within the transmission frequency band where the loss is low. Resonance compared to the case where resonance occurs as a standing distribution in which the charge distribution in the circumferential direction increases in density in the semicircular or fan-shaped circumferential end and middle when the frequency is reached The frequency can be moved to the high frequency side of the transmission frequency band with lower loss. As a result, a low-loss transmission frequency band is widened, so that a high-frequency measurement substrate having a low-loss characteristic in a wide band can be obtained.
[0053]
Further, according to the high-frequency measurement substrate of the present invention, since a high-precision substrate processing step is not required as in the case of a conventional high-frequency measurement substrate using a through conductor such as a through-hole conductor or a via-hole conductor, A high-frequency measurement substrate capable of highly accurate measurement can be provided easily and inexpensively.
[0054]
As described above, according to the present invention, in the high frequency measurement substrate using the radial stub as an equivalent ground, the low loss transmission frequency band is widened by appropriately setting the substrate thickness of the dielectric substrate. A substrate could be provided.
[Brief description of the drawings]
FIGS. 1A to 1C are plan views showing examples of embodiments of a high-frequency measurement substrate according to the present invention, respectively.
FIG. 2 is a diagram showing transmission characteristics with respect to frequency in a high-frequency measurement substrate.
FIG. 3 is a diagram showing transmission characteristics with respect to frequency in a high-frequency measurement substrate.
FIG. 4 is a diagram showing reflection characteristics and transmission characteristics with respect to frequency in a high-frequency measurement substrate.
FIG. 5 is a plan view showing an example of a conventional high-frequency measurement substrate.
FIG. 6 is a diagram showing reflection characteristics with respect to frequency in a high-frequency measurement substrate.
FIG. 7 is a diagram showing transmission characteristics with respect to frequency in a high-frequency measurement substrate.
FIG. 8 is a plan view showing an example of a conventional high-frequency measurement substrate.
FIG. 9 is a diagram showing transmission characteristics with respect to frequency in a high-frequency measurement substrate.
FIG. 10 is a plan view showing an example of a conventional high-frequency measurement substrate.
FIG. 11 is a plan view showing an example of a radial stub.
[Explanation of symbols]
31 ・・・・・・・・・・ Dielectric substrate
32 ・・・・・ Microstrip line signal conductor
33 ・・・・・ Coplanar signal conductor
34, 34 '・・・・・・・ Equivalent ground conductor

Claims

A ground conductor is formed on substantially the entire bottom surface of the dielectric substrate, the signal conductor of the microstrip line is formed on the top surface, and two substantially fan surfaces that are axisymmetric with respect to the center line of the signal conductor provided near the tip of the signal conductor An equivalent ground conductor is formed by using a radial stub of a shape, and the signal conductor and the ground conductor of the wafer probe having a coplanar line structure are electrically connected to the signal conductor and the equivalent ground conductor, respectively. In the substantially fan-shaped equivalent ground conductor, the length of the first side on the signal conductor side and the length of the second side on the other side is shorter than the length of the arc of the outer circumference and is along the radial direction. The angle between the first side on the signal conductor side and the extending direction of the center line of the signal conductor is θ ₁ , and the second side on the other side and the extension of the center line of the signal conductor 90 when the angle formed by the direction is θ ₂ A substrate for high-frequency measurement, wherein ° ≦ θ ₁ ≦ 180 ° and 3/8 ≦ θ ₂ / θ ₁ ≦ 5/8.

The center of the two equivalent ground conductor of substantially fan face shape is concentric, the two equivalent grounding conductor, the intersection of an extension of the said an extension of the first lateral side second sides 2. The high frequency device according to claim 1 , wherein the first side and the extension line and the second side and the extension line have a radius and the outer periphery has an arc shape. Measurement board.