JP2004254001A - Method and apparatus for detecting arrival direction of radio wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting an arrival direction of a radio wave which does not need calibration when using an electronically steerable passive array radiator antenna to detect a radio wave arrival angle. <P>SOLUTION: In a radio wave arrival direction detecting device that uses the array antenna device 100, a radio wave arrival direction detection computer 30 receives and detects the same radio signal transmitted from a plurality of prescribed azimuths different from one another in the state of a plurality of radiation patterns from different one another, wherein a plurality of sets with reactance values of respective variable reactance elements different one another are set by an array antenna, and calculates a current steering vector inherent to the antenna on the basis of each detected radio signal. Each reception signal y(t) received when the plurality of sets whose reactance values are different from one another is detected to calculate a correlation matrix R<SB>yy</SB>among a plurality of reception signals, the correlation matrix R<SB>yy</SB>is decomposed into characteristic values to calculate its characteristic vector, and a music spectrum is calculated on the basis of the current steering vector to calculate the arrival angle of the reception signals. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２９】
ここで、φ_ｍ＝３６０（ｍ−１）／６，０≦ｍ≦６は、励振素子Ａ０に対して非励振素子Ａ１が位置する方向を基準として、ｍ番目の非励振素子Ａｍが位置する方向の方位角である。
【００３０】
合計Ｑ個の着信信号ｕ_ｑ（ｔ）が存在して、各着信信号ｕ_ｑ（ｔ）が、対応する到来角であるθ_ｑ（ｑ＝１，２，…，Ｑ）を有するものとすれば、ｓ（ｔ）で示される、アレーアンテナ装置１００に入射するＲＦ信号ベクトルは、次式のように表わすことができる。
【００３１】
【数２】

【００３２】
この信号モデルによれば、アレーアンテナ装置１００から出力される受信信号は次式のように表すことができる。
【００３３】
【数３】
ｙ（ｔ）＝ｉ^Ｔｓ（ｔ）＋ｎ（ｔ）
【００３４】
ここで、ｎ（ｔ）は相加性白色ガウス雑音信号であり、ｉはＲＦ電流ベクトルである。説明の簡単化のために、アレーアンテナ装置１００から出力される信号と無線受信機４から出力される信号とを同様に受信信号ｙ（ｔ）と表記する。電流ベクトルｉは、アレーアンテナ装置１００のリアクタンスと、アンテナ素子間の相互インピーダンスと、励振素子Ａ０のＲＦソース電圧Ｖ_ｓとに依存する（非特許文献３を参照）。この電流ベクトルｉは、次のように定式化される。
【００３５】
【数４】
ｉ＝Ｖ_ｓ（Ｚ＋Ｘ）^−１ｕ_０
【００３６】
ここで、Ｖ_ｓは定数であり、Ｘは次式の対角行列で表されるリアクタンス行列である。
【００３７】
【数５】
Ｘ＝ｄｉａｇ［５０，ｊｘ_１，ｊｘ_２，…，ｊｘ_６］
【００３８】
また、ｕ_０は次式で表される（６＋１）次元ベクトルである。
【００３９】
【数６】
ｕ_０＝［１，０，０，０，０，０，０］^Ｔ
【００４０】
さらに、Ｚは（６＋１）×（６＋１）定数値行列で表された相互インピーダンス行列であり、その成分はアンテナ素子間の相互インピーダンスによって決定される定数である。具体的には次式のようになる。
【００４１】
【数７】

【００４２】
アレーアンテナ装置１００の構造は巡回的な対称性を有しているため、この行列Ｚの４９個の成分のうち独立な成分は６個の成分となる。これらはその物理的意味からそれぞれ以下のように呼ばれるべき複素パラメータである。
【００４３】
【表１】
―――――――――――――――――――――――――――――――――――
ｚ_００：励振素子の自己入力インピーダンス。
ｚ_０１：励振素子と非励振素子との間の結合インピーダンス。
ｚ_１１：非励振素子の自己入力インピーダンス。
ｚ_１２：互いに隣接する２つの非励振素子間の結合インピーダンス。
ｚ_１３：次に隣接する（１つ間をおいて隣接する）２つの非励振素子間の結合インピーダンス。
ｚ_１４：互いに対向する２つの非励振素子間の結合インピーダンス。
―――――――――――――――――――――――――――――――――――
【００４４】
アレーアンテナ装置１００の場合は、ただ１つのアンテナ素子上の信号のみが測定可能であることが分かるが、このことは、すべてのアンテナ素子上の信号が測定可能である従来型の適応型アンテナとは異なる。従って、インピーダンス行列Ｚは実際には完璧に推定できないことが分かる。よって、数４を使用して電流ベクトルｉを計算する場合、推定されるＭＵＳＩＣの到来角スペクトルの精度は、推定されたインピーダンス行列Ｚに依存する（非特許文献３を参照）。
【００４５】
次に、本実施形態のアレーアンテナ装置１００の場合に応用される、リアクタンス領域のＭＵＳＩＣアルゴリズムの原理について説明する（非特許文献４を参照）。
【００４６】
まず、アレーアンテナ装置１００に対する相関行列の計算方法について説明する。アレーアンテナ装置１００の場合、励振素子Ａ０に接続された単一ポートの出力信号のみが観測可能でありかつ測定可能であって、他の周辺の６本の非励振素子Ａ１乃至Ａ６上の信号を観測することはできない。さらに、複数のアンテナ素子上のＲＦ電流は互いに結合されあうので、アレーアンテナ装置１００から出力される受信信号は、調整可能な複数のリアクタンス値の非線形関数である。従って、これらの調整可能なリアクタンス値とアレーアンテナ装置１００から出力されて測定された受信信号のみを用いて相関行列Ｒ_ｙｙを計算しなければならない。
【００４７】
計算処理のために、まずアレーアンテナ装置１００の６本の非励振素子Ａ１乃至Ａ６に着目して考察すると、６回反復して送信される同一の入射信号に対して、６個のリアクタンス値のセット（すなわちリアクタンスベクトル）ｘの値を６回変化させることにより、アレーアンテナ装置１００の空間ダイバーシティを取得することができる。以下、各リアクタンスベクトルを、ｘ^ｍ，１≦ｍ≦６と表記する。図４は、図１のアレーアンテナ装置１００で受信される信号のタイミングチャートである。アレーアンテナ装置１００に入射する信号データは、Ｐ個のシンボルＳ_１乃至Ｓ_ｐより成る各ブロックが６回反復される変調信号である。各シンボルの長さは時間Ｔであるので、信号データ全体の長さは時間６Ｔ×Ｐになる。各ブロックが受信される毎に、アレーアンテナ装置１００にはリアクタンス値の異なるセットが設定され、図４では、設定される各リアクタンスベクトルの成分をｘ_１ ^ｍ，…，ｘ_６ ^ｍで表している。
【００４８】
上記６個のリアクタンスベクトルｘ^１，…，ｘ^６は、リアクタンス値テーブルメモリ２０内に予め設定されたディジタル電圧値を成分として含む６個のセットに基づいて生成される。６個のリアクタンスベクトルによって形成されるアレーアンテナ装置１００の６個の指向性ビームパターンを互いに異なるものにするために、例えば、可変リアクタンス素子１２−１乃至１２−６に印加される制御電圧値にそれぞれに対応するディジタル電圧値ｖ_１，ｖ_２，…，ｖ_６を以下の表のように巡回させ、これらのディジタル電圧値にて構成される６個の電圧値セットｖ^１，ｖ^２，…，ｖ^６をリアクタンス値テーブルメモリ２０内に予め設定しておく。
【００４９】
【表２】

【００５０】
本実施形態では、ディジタル電圧値ｖ_１，ｖ_２，…，ｖ_６を表２のように巡回させて設定している（以下、これをシフト法という。）が、本発明はこれに限らず、互いにビームパターンが異なるディジタル電圧値であればよく、例えば、公知の乱数発生法を用いて発生された乱数値を、ディジタル電圧値ｖ_１，ｖ_２，…，ｖ_６に設定してもよい。ただし、オムニパターンのディジタル電圧値（すなわち、各非励振素子に対して実質的に同一の値）を採用しないことが好ましい。
【００５１】
次に、各リアクタンスベクトルｘ^１，…，ｘ^６が設定された場合のそれぞれについてアレーアンテナ装置１００から出力される受信信号を観測することによって、次のような受信信号ベクトルを構成する。
【００５２】
【数８】
ｙ（ｔ）＝［ｙ_１（ｔ），…，ｙ_ｍ（ｔ），…，ｙ_６（ｔ）］^Ｔ
【００５３】
ここで、ｙ_ｍ（ｔ）は、アレーアンテナ装置１００にｍ番目のリアクタンスベクトルｘ^ｍが設定されているときに、アレーアンテナ装置１００から出力されて測定された受信信号である。最終的に、アレーアンテナ装置１００で受信される複数の受信信号間の相関を表す相関行列Ｒ_ｙｙを次式のように評価することができる。
【００５４】
【数９】
Ｒ_ｙｙ＝Ｅ［ｙ（ｔ）ｙ（ｔ）^Ｈ］
【００５５】
ここで、上付き添字^Ｈはエルミート転置演算を示す。
【００５６】
アレーアンテナ装置１００の各アンテナ素子によって受信される信号は、数３に示されたように、入射する信号と雑音との組み合せである。さらに、電流ベクトルｉは、数４に示されたように、定数値と可変なリアクタンス値との組み合せである。従って、１つのリアクタンスベクトルｘ^ｍ（ｍ＝１，２，…，６）に対して、アレーアンテナ装置１００から出力される受信信号は次のように表すことができる。
【００５７】
【数１０】

【００５８】
ここで、アレーアンテナ装置１００で受信される各着信信号ｕ_ｑ（ｔ），ｑ＝１，２，…，Ｑが、同期化され、かつ６回反復して送信されるものと仮定する。受信信号ベクトルｙ（ｔ）は、６回の反復のそれぞれにおける電流ベクトルと雑音信号とを、ｉ_１，…，ｉ_６とｎ_１，…，ｎ_６によって表すと、数１１、又はそれに等価な形式である数１２で示すことができる。
【００５９】
【数１１】

【数１２】
Ｙ（ｔ）＝Ｉ^ＴＡｕ（ｔ）＋ｎ（ｔ）
【００６０】
ここで、Ｉを電流行列と呼ぶ。さらに電流ステアリングベクトルａ_ｒｅａ（θ_ｑ）を、
【数１３】

と表記することによって、数１１は、次式
【数１４】

又は、等価な形式
【数１５】
ｙ（ｔ）＝Ａ_ｒｅａｕ（ｔ）＋ｎ（ｔ）
に書き直すことができる。
【００６１】
従って、数９の推定された相関行列Ｒ_ｙｙと、アレーアンテナ装置１００の受信信号ベクトルの対応する表現式（数１５）とに基づいて、リアクタンス領域のＭＵＳＩＣアルゴリズムの計算ステップを与えることができる。
【００６２】
＜ステップ１＞図４のような信号が送信されているときに測定されたアレーアンテナ装置１００の受信信号ｙ（ｔ）から、相関行列Ｒ_ｙｙを計算する。
＜ステップ２＞相関行列Ｒ_ｙｙの固有値分解を実行して、降順で並んだ固有値λ_１，λ_２，…，λ_６とそれらの対応する固有ベクトルｅ_１，ｅ_２，…，ｅ_６とを計算する。
＜ステップ３＞推定すべき到来角の個数Ｄ（Ｄ＜６）を決定するために、固定されたしきい値Ｔよりも大きいＤ個の固有値を用いることができ、あるいは、入射する信号の個数が知られていれば個数Ｄは固定される。
＜ステップ４＞雑音部分空間行列をＥ_Ｎ＝［ｅ_Ｄ＋１，ｅ_Ｄ＋２，…，ｅ_６］と構成する。ここで、Ｅ_Ｎはステップ２で計算された固有ベクトルで構成されるＮ列の行列であり、Ｎ＝６−Ｄである。従って、次式を０゜≦θ＜３６０゜について計算することにより、ＭＵＳＩＣの到来角スペクトルの推定値を導出することができる。
【００６３】
【数１６】

【００６４】
推定された到来角θ_ｍａｘ（１，２，…，Ｄ）は、到来角スペクトルＰ_ＭＵ（θ）が最大になるときの方位角θの値である。
【００６５】
上述のステップ１乃至４は、図１の電波到来方向探知装置によって実行されるが、電流ステアリングベクトルａ_ｒｅａ（θ）は、これらのステップを実行する前に予め取得されている必要がある。電流ステアリングベクトルの取得は、図３のパターン測定装置によって実行される。
【００６６】
次に、電流ステアリングベクトルを取得するための方法を説明するために、到来角スペクトルＰ_ＭＵ（θ）を推定するための２つの実験的な方法について説明する。
【００６７】
本実施形態のＭＵＳＩＣアルゴリズムでは、実際には離散時間値を用いたので、アレーアンテナ装置１００から出力される受信信号（数３参照）は、ｙ［ｋ］＝ｙ（ｋＴ）としてｙ［ｋ］で表記される。ここで、ｋは離散時間のインデックスであり、Ｔは時間サンプルレートに対応する定数である。
【００６８】
まずは、アレーアンテナ装置１００の相関行列Ｒ_ｙｙの計算について説明する。図４に示されたように、アレーアンテナ装置１００に入射する信号データは、Ｐ個のシンボルＳ_１乃至Ｓ_ｐより成る各ブロックが６回反復される変調信号である。ブロック毎にリアクタンス値の異なるセットが使用される。
【００６９】
複数の受信信号間の相関を表す相関行列Ｒ_ｙｙは、図４のような受信信号に基づいて、次式のように推定される。
【００７０】
【数１７】

【００７１】
ここで、上付き添字^＊は複素共役を表す。
【００７２】
以下説明する２つの方法、すなわち、非特許文献４に記載された従来例の方法と同様の等価ウエイトベクトル法と、本発明に係る実施形態である直接測定法とは、数１６の電流ステアリングベクトルａ_ｒｅａ（θ）を取得するための方法において異なっている。
【００７３】
まず、等価ウェイトベクトル法（ＥＷＶ法）によるＭＵＳＩＣの到来角スペクトルＰ_ＭＵ（θ）の計算方法について説明する。ｍ番目の非励振素子Ａｍに装荷される重み（ウエイト）であるリアクタンス値は、ディジタル電圧値ｖ_ｍ（ｍ＝１，２，…，６）に対応した制御電圧値を可変リアクタンス素子１２−ｍに設定することによって変化される。リアクタンス値ｘ_ｍとディジタル電圧値ｖ_ｍとの関係は、次式によって近似される。
【００７４】
【数１８】
ｘ_ｍ＝−０．０２１７ｖ_ｍ−４９．２１
【００７５】
リアクタンス値コントローラ１０は、リアクタンス値テーブルメモリ２０内に予め設定された−２０４８≦ｖ_ｍ≦２０４７の値を有するディジタル電圧値ｖ_ｍを、内蔵したディジタル／アナログ変換器（図示せず。）を用いてアナログの制御電圧値に変換し、次いで、この制御電圧値をリアクタンス値信号として可変リアクタンス素子１２−ｍに出力して設定する。このとき、可変リアクタンス素子１２−ｍに設定されるリアクタンス値ｘ_ｍの範囲は、−９３．６３Ω≦ｘ_ｍ≦−４．７７Ωになる。
【００７６】
電流行列Ｉ^Ｔ（数１２参照）を計算するためには、数４に与えられた電流ベクトルｉの式を用いる。正確には、ディジタル電圧の各セットｖ^ｍ＝［ｖ_１，ｖ_２，…，ｖ_６］について、ディジタル電圧のセットｖ^ｍはリアクタンスベクトルｘ^ｍ＝［ｘ_１，ｘ_２，…，ｘ_６］に対応しているので、リアクタンスベクトルｘ^ｍの代わりにディジタル電圧のセットｖ^ｍに基づいて、電流ベクトルｉ_ｍの計算に使用されるリアクタンス行列Ｘを形成する（数４を参照）。６個のリアクタンスベクトルについてこの処理を反復すると、ＭＵＳＩＣの到来角スペクトルの計算に用いられる電流行列Ｉ^Ｔを得ることができ、従って、数１３より電流ステアリングベクトルａ_ｒｅａ（θ）を得ることができる。
【００７７】
この方法では、電流行列Ｉ^Ｔの計算値と、よってＭＵＳＩＣの到来角スペクトル（数１６参照）とは、インピーダンス行列Ｚと、リアクタンス値を取得するために用いられる、リアクタンス値とそれに等価なディジタル電圧値の間の関係とを推定することによって導出される点に注意する。従って、到来角スペクトルの精度を向上させるためには、これらのパラメータは較正されていなければならない。
【００７８】
次に、直接測定法（ＤＭ法）を用いたＭＵＳＩＣの到来角スペクトルＰ_ＭＵ（θ）の計算方法について説明する。上述の等価ウエイトベクトル法では、与えられたアレーアンテナについて、インピーダンス行列Ｚと、ディジタル電圧値及びリアクタンス値の関係とを推定する必要がある。取得されるＭＵＳＩＣの到来角スペクトルの精度は、これらの推定に強く依存する。なお、直接測定法では、到来角スペクトルは、直接に測定されたデータのみを用いて計算される。
【００７９】
本方法は、雑音なしの仮定において、方位角θの方向から到来する１つの一定の着信信号（すなわち連続波信号）ｕ（ｔ）（例えば、任意のｔに対して、ｕ（ｔ）＝Ｋ＝１）とリアクタンスベクトルｘとについて、アレーアンテナ装置１００から出力される受信信号（数３参照）が次式で表されるという考えに基づいている。
【００８０】
【数１９】
ｙ（ｔ）＝ｉ^Ｔａ（θ）ｕ（ｔ）＝ｉ^Ｔａ（θ）
【００８１】
これは、アレーアンテナ装置１００から出力される受信信号の電力及び位相を測定することによって推定可能である。図３に示されたように、パターン測定コンピュータ５０には、無線送信機４０が送信する無線信号の一部が分岐されて入力され、パターン測定コンピュータ５０は、無線送信機４０から入力された無線信号の位相を基準として、無線受信機４から入力される受信信号の位相を測定する。
【００８２】
６個のリアクタンスベクトルの各々について、アレーアンテナ装置１００から出力される受信信号の電力及び位相を測定することによって、与えられた方位角θに対する次式の電流ステアリングベクトルを得ることができる。
【００８３】
【数２０】

【００８４】
次に、数１６を用いて、０゜≦θ＜３６０゜についてＭＵＳＩＣの到来角スペクトルを計算する。
【００８５】
アレーアンテナ装置１００の方位角θの値をそれぞれ異なる値（例えば、θ＝０°，１，…，３５９°）に固定し、予め与えられた６個のリアクタンスベクトルをそれぞれアレーアンテナ装置１００に設定する毎に、各リアクタンスベクトルに対応するビームパターンで受信された各受信信号の測定値と、上記受信信号に基づいて計算された行列Ｅ_Ｎとにより、到来角スペクトルＰ_ＭＵ（θ）が形成されるということを注意する。また、６個のビームパターンで受信される各受信信号がそれぞれただ１度だけ測定されると（従って、数１９より、電流ステアリングベクトルがいったん取得されると）、異なる到来角で入射する同一の信号ｕ（ｔ）に対してそれぞれ到来角推定値を生成することができる。同様に、後述の実験３において仰角を変化させたときの到来角推定値を取得するとき、６個のビームパターンで受信される各受信信号がそれぞれただ１度だけ測定されると、異なる仰角で入射する同一の信号ｕ（ｔ）に対してそれぞれ到来角の推定値を生成することができる。
【００８６】
以上説明したように、図３のパターン測定装置は、アレーアンテナ装置１００の互いに異なる複数の所定の方位角の方向から送信される同一の無線信号を、上記各可変リアクタンス素子のリアクタンス値の互いに異なる複数のセットがそれぞれ設定された状態においてアレーアンテナ装置１００で受信し、上記受信された各無線信号の電力及び位相を測定し、上記測定された各無線信号の電力及び位相に基づいて、アレーアンテナ装置１００に固有の電流ステアリングベクトルａ_ｒｅａ（θ）を計算する。この電流ステアリングベクトルａ_ｒｅａ（θ）は電流ステアリングベクトルメモリ５４に記憶され、電流ステアリングベクトルメモリ５４は、図１の電波到来方向探知装置の電波到来方向探知コンピュータ３０に接続される。
【００８７】
【実施例】
以下、本実施形態の電波到来方向探知装置の実験結果として取得された到来角スペクトルについて説明する。実験による測定は、図３に示されたパターン測定装置を用いて電波暗室２００内で行われた。この場合、方位角及び仰角コントローラ５１は、無線信号が所定の到来角でアレーアンテナ装置１００に入射するように支持台１０１を用いてアレーアンテナ装置１００を回転させて固定し、パターン測定コンピュータ５０は、電波到来方向探知コンピュータ３０と同様の動作を実行して、上記無線信号の到来角を探知する。
【００８８】
＜実験１及び実験２＞
以下の実験の目的は、アレーアンテナ装置１００によるリアクタンス領域のＭＵＳＩＣアルゴリズムを使用して、１つの入射信号の到来角を推定することにある。ここで、入射信号の総数Ｑ＝Ｄ＝１とする。実験は、比較のために、先に説明した等価ウエイトベクトル法と直接測定法との２つの方法で行なう。
【００８９】
相関行列Ｒ_ｙｙを計算するために用いられるシンボルブロックのサイズは、Ｐ＝２００である。入射信号のデータはバイナリ位相シフトキーイング（ＢＰＳＫ）で変調され、信号電力は約１０ｄＢｍである。
【００９０】
先述の方法の各々について、２つの実験セットを行った（実験１及び実験２）。これらの実験セットでは、選択されたリアクタンスベクトル（すなわち、リアクタンス値テーブルメモリ２０に予め記憶されたディジタル電圧値のセット）と着信信号の到来角とが異なる。直接測定法はＤＭ法と呼ばれ、等価ウェイトベクトル法はＥＷＶ法と呼ばれる。図５及び図６は、図１の電波到来方向探知装置の実験結果であって、実験１の場合にＭＵＳＩＣの到来角スペクトルから到来角推定値を得た方法を示している。図５は、到来角３０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフであり、図６は、到来角１４０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。表３にはさらに、到来角６０°、９０°及び１２０°のときの、ＤＭ法とＥＷＶ法の両方についての到来角推定値がまとめられている。
【００９１】
【表３】
２つの方法に対する到来角推定値（実験１）
――――――――――――――――――――――――――――――――――――
到来角 ３０° ６０° ９０° １２０° １４０°
――――――――――――――――――――――――――――――――――――
到来角推定値
ＤＭ法 ２９° ５９° ８８° １２３° １４３°
ＥＷＶ法 ２４° ４２° ８９° １０８° １４６°
――――――――――――――――――――――――――――――――――――
【００９２】
図７及び図８は、電波到来方向探知装置の実験結果であって、実験２の場合にＭＵＳＩＣの到来角スペクトルから到来角推定値を得た方法を示している。図７は、到来角０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフであり、図８は、で到来角６０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。表４にはさらに、到来角３０°及び１２０°のときの、ＤＭ法とＥＷＶ法の両方について到来角推定値がまとめられている。
【００９３】
【表４】
２つの方法に対する到来角推定値（実験２）
――――――――――――――――――――――――――――――――――――
到来角 ０° ３０° ６０° １２０°
――――――――――――――――――――――――――――――――――――
到来角推定値
ＤＭ法 ２° ３２° ６０° １１７°
ＥＷＶ法 −７° ２２° ５５° １１０°
――――――――――――――――――――――――――――――――――――
【００９４】
表３と表４からは、明らかに、推定される到来角の精度は、ＥＷＶ法よりもＤＭ法の方が高いことが分かる。ここで、同一の到来角値であれば、２つの実験はリアクタンスベクトルが相違するのみであり、両方の実験１及び２において２つの方法を比較すると、ＤＭ法の相対誤差は０゜乃至３゜であって、ＥＷＶ法の相対誤差は５゜乃至１８゜であると言える。またＤＭ法の場合、相対的な角度推定値の誤差は一定であり、ＥＷＶ法よりも、到来角スペクトルは鋭くかつより高い最大レベル値（単位ｄＢ）を有している。このことは、ＥＷＶ法では、推定される到来角の精度が、評価されたインピーダンス行列Ｚに依存するという事実から説明することができる。この場合、結果をより良いものにするために、インピーダンス行列を較正する必要がある。ＤＭ法ではインピーダンス行列が使用されないので、較正の問題は直ちに解消される。
【００９５】
＜実験３＞
以下の実験の目的は、異なる仰角の設置角度に対して、アレーアンテナ装置１００によるリアクタンス領域のＭＵＳＩＣアルゴリズムを用いることによって、１つの入射信号の到来角を推定することにある。到来方向の推定には、直接測定法を用いた。
【００９６】
図３は、受信用アンテナとしてのアレーアンテナ装置１００と送信用アンテナとしてのホーンアンテナ装置４１の構成及び位置関係を示している。アレーアンテナ装置１００及び支持台１０１の構造上の制約のために、ホーンアンテナ装置４１によって送信される信号は、アレーアンテナ装置１００上に９０゜方向で到来する。実験は、アレーアンテナ装置１００の鉛直方向の軸（すなわち励振素子Ａ０）をホーンアンテナ装置４１の方向に傾けて、０゜から３０゜までの仰角で行われた。
【００９７】
相関行列Ｒ_ｙｙを推定するために、各リアクタンスベクトルｘ^ｍ（ｍ＝１，…，６）について、アレーアンテナ装置１００から出力されて測定された対応する受信信号は、各チャンネル（Ｉ及びＱチャンネル）毎に２００シンボルを使用した。すべての実験を通じて、送信された無線信号の電力は約１０ｄＢｍであった。
【００９８】
まず、ＭＵＳＩＣアルゴリズムによる到来角推定の一例を挙げる。図９は、図１の電波到来方向探知装置の実験結果であって、実験３で到来角９０°かつ仰角１０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。図９の曲線が最大になるときの角度値は、アレーアンテナ装置１００に入射する信号の到来角推定値に一致している。
【００９９】
図１０は、到来角９０°かつ仰角０°乃至３０°のときの到来角推定値を示す表である。入射する信号の到来角は９０゜に固定された。ＭＵＳＩＣアルゴリズムによる到来角推定値θは、０゜から３０゜までの仰角（傾き角度）φについて得られた。測定された角度は図１０の表にまとめられている。
【０１００】
これらの測定値は、推定された角度の平均が約８８．２゜であり、標準偏差角は３．８゜であることを示している。ＭＵＳＩＣによる到来角スペクトルの標準偏差は、約１．３ｄＢである。これらの結果から、３０゜未満の仰角に関しては、推定された角度の大域的な精度は変化しないと言える。
【０１０１】
本実施形態において、われわれは、アレーアンテナ装置１００に入射する信号の到来角を推定する２つの実験的な方法を提案した。実験結果（実験１及び実験２）は、特に直接測定法を用いたときに、入射する信号の到来角が約３゜の精度で推定可能であることを示している。また、相関行列Ｒ_ｙｙの計算がＰ＝２００個のシンボルサンプルのみを用いて実行されたという点を強調することも重要である。実験は、本発明で提案された直接測定法が、推定される角度の精度を改善しただけでなく、アレーアンテナ装置１００から出力される受信信号のモデル化において使っているインピーダンスパラメータの較正という重要な問題を解決したことを示している。
【０１０２】
われわれはさらに、実験３において、リアクタンス領域のＭＵＳＩＣアルゴリズムを用いて計算される角度推定値に対して、アレーアンテナ装置１００に対する仰角が与える影響を検証した。実験結果は、推定される角度の精度に対して仰角が影響しないことを示している。到来方向を推定するアプリケーションでは、実験結果をもとにして行った統計が、仰角が３０゜未満であるときに約４゜の精度を期待できるということを示している。異なる仰角で行った実験は、アレーアンテナ装置１００のためのリアクタンス領域のＭＵＳＩＣアルゴリズムを使用することによって、効率を損なうことなく到来角推定が実行可能であるということを示している。
【０１０３】
＜変形例＞
以上説明した実施形態では（６＋１）素子のアレーアンテナ装置１００を用いたが、非励振素子の本数が任意のＭ本であるアレーアンテナ装置を用いて同様に電波到来方向を探知できることは明らかであろう。
【０１０４】
実験では、１つ着信信号の到来角を見つけ出すために、リアクタンス領域のＭＵＳＩＣアルゴリズムが効果的に使用可能であることを確認したわけであるが、例えば複数の着信信号が存在する場合にも、アレーアンテナ装置１００を使用する多くの実験構成を調査することができる。
【０１０５】
以上説明したように、本発明に係る実施形態の電波到来方向探知装置によれば、高い検出精度で、同時に複数の電波到来方向を検出できるとともに、厳密に較正された信号モデルに依存しない電波到来方向探知装置を提供することができる。さらに、ハードウエア回路を従来例の電波到来方向探知方法に比較して簡単化できる。実験結果は、入射する１つの信号の到来方向を３°以内の誤差精度で推定でき、また、到来角の推定値は、入射する信号の有する仰角（０°乃至３０°）には影響されないということを示している。すなわち、受信部である電子制御導波器アレーアンテナ装置を手持ちで持った場合において手ぶれを生じた場合（仰角が変化した場合）であっても高い精度で電波到来角を推定して計算できるという特有の効果を有している。
【０１０６】
【発明の効果】
以上詳述したように、本発明に係る電波到来方向探知方法又は装置によれば、公知の電子制御導波器アレーアンテナ装置を用いた電波到来方向探知方法又は装置において、アレーアンテナの互いに異なる複数の所定の方位角の方向から送信される同一の無線信号をそれぞれ、各可変リアクタンス素子のリアクタンス値の互いに異なる複数のセットがそれぞれ設定された互いに異なる複数の放射パターンの状態において上記アレーアンテナで受信し、上記受信された各無線信号の信号レベル及び位相を検出し、上記検出した各無線信号の信号レベル及び位相に基づいて、上記アレーアンテナに固有の電流ステアリングベクトルａ_ｒｅａ（θ）を計算した後、上記各可変リアクタンス素子のリアクタンス値の上記互いに異なる複数のセットをそれぞれ設定したときに上記アレーアンテナによって受信される各受信信号ｙ（ｔ）を検出し、上記複数の受信信号間の相関を表す相関行列Ｒ_ｙｙを計算し、上記計算された各相関行列Ｒ_ｙｙを固有値分解して上記各相関行列Ｒ_ｙｙの固有ベクトルを計算し、上記計算された各固有ベクトルと上記電流ステアリングベクトルａ_ｒｅａ（θ）とに基づいて、ＭＵＳＩＣ法を用いてＭＵＳＩＣスペクトルを計算し、上記計算されたＭＵＳＩＣスペクトルに基づいて上記アレーアンテナによって受信された受信信号の到来角を計算する。
【０１０７】
従って、高い検出精度で、同時に複数の電波到来方向を検出できるとともに、厳密な較正を必要とする信号モデルに依存しない電波到来方向探知装置を提供することができる。また、ハードウエア回路を従来例の電波到来方向探知方法に比較して簡単化できる。さらに、受信部である電子制御導波器アレーアンテナ装置を手持ちで持った場合において手ぶれを生じた場合（仰角が変化した場合）であっても高い精度で電波到来角を推定して計算できる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る電波到来方向探知装置の構成を示すブロック図である。
【図２】図１のアレーアンテナ装置１００の詳細な構成を示す断面図である。
【図３】図１の電波到来方向探知装置で用いる電流ステアリングベクトルを取得するためのパターン測定装置の構成を示すブロック図である。
【図４】図１のアレーアンテナ装置１００で受信される信号のタイミングチャートである。
【図５】図１の電波到来方向探知装置の実験結果であって、実験１で到来角３０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。
【図６】図１の電波到来方向探知装置の実験結果であって、実験１で到来角１４０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。
【図７】図１の電波到来方向探知装置の実験結果であって、実験２で到来角０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。
【図８】図１の電波到来方向探知装置の実験結果であって、実験２で到来角６０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。
【図９】図１の電波到来方向探知装置の実験結果であって、実験３で到来角９０°かつ仰角１０°のときの到来角スペクトルＰ_ＭＵ（θ）を示すグラフである。
【図１０】図１の電波到来方向探知装置の実験結果であって、実験３で到来角９０°かつ仰角０°乃至３０°のときの到来角推定値を示す表である。
【符号の説明】
Ａ０…励振素子、
Ａ１乃至Ａ６…非励振素子、
１…低雑音増幅器（ＬＮＡ）、
２…ダウンコンバータ、
３…Ａ／Ｄ変換器、
４…無線受信機、
９…同軸ケーブル、
１０…リアクタンス値コントローラ、
１１…接地導体、
１２−１乃至１２−６…可変リアクタンス素子、
２０…リアクタンス値テーブルメモリ、
３０…電波到来方向探知コンピュータ、
３１，５３…ＣＲＴディスプレイ、
４０…無線送信機、
４１…ホーンアンテナ装置、
５０…パターン測定コンピュータ、
５１…方位角及び仰角コントローラ、
５２…入力装置、
５４…電流ステアリングベクトルメモリ、
１００…アレーアンテナ装置、
１０１…支持台、
２００…電波暗室。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and apparatus for detecting a radio wave arrival direction using an array antenna having a plurality of antenna elements and capable of changing a directional characteristic, and more particularly, to an electronic control waveguide capable of adaptively changing a directional characteristic. TECHNICAL FIELD The present invention relates to a method and apparatus for detecting the direction of arrival of a radio wave using an electronically steerable passive array antenna.
[0002]
[Prior art]
Estimating the angle of arrival (DoA) of a signal incident on an array antenna is an interesting and important issue in digital array processing. Several methods have been proposed to solve this problem. In particular, the MUSIC (Multiple Signal Classification) algorithm described in Non-Patent Document 1 is widely known to provide a result that asymptotically approaches an unbiased estimator.
[0003]
The electronically controlled waveguide array antenna devices proposed in Patent Document 1 and Non-Patent Documents 2 and 3 are provided with an excitation element to which a radio signal is fed and a predetermined distance from the excitation element, An array antenna comprising at least one parasitic element to which no power is supplied and a variable reactance element connected to the parasitic element, and by changing a reactance value of the variable reactance element, the directional characteristic of the array antenna is changed. Can be changed. The electronically controlled director array antenna device has lower cost, lower power consumption, and a simpler configuration than conventional array antennas. Therefore, this electronically controlled waveguide array antenna device is a very promising candidate for application to mobile user terminals. However, since the electronically controlled director array antenna device has a single-port output configuration, the algorithm for the conventional array antenna cannot be used as it is.
[0004]
Recently, a “reactance region MUSIC algorithm” based on an improved MUSIC algorithm has been proposed for estimating a radio wave arrival angle using the array antenna of Patent Document 1 (see Non-Patent Document 4). This algorithm obtains the correlation matrix of the array antenna and estimates the arrival angles of a plurality of incident signals (hereinafter, referred to as a conventional example).
[0005]
[Patent Document 1]
JP-A-2001-24431.
[Non-patent document 1]
R. O. Schmidt, "Multiple Emitter Location and Signal Parameter Estimation", IEEE Transactions on Antennas and Propagation, Vol. AP-34, no. 3, pp. 276-280, March, 1986.
[Non-patent document 2]
T. Ohira et al. , "Electronically Steerable Passive Array Radiator Antennas for Low-Cost Analog Analog Beamforming," 2000 IEEE International Conference on Electronics and Technology. 101-104, Dana point, California, May 21-25, 2000.
[Non-Patent Document 3]
T. Ohira, et al. , "Equivalent weight vector and array factor formation for Espar antennas," IEICE Technical Report, AP2000-44, SAT2000-41, NW2000-41, July.
[Non-patent document 4]
Plapus Cyril et al., "Reactance Domain MUSIC Method Using ESPAR Antenna", IEICE Technical Report, RCS2002-147, published by IEICE, August 2002.
[0006]
[Problems to be solved by the invention]
However, in the conventional method of detecting the direction of arrival of a radio wave, the direction of arrival of the radio wave is detected using a signal model of the received signal output from the array antenna. Therefore, in order to more accurately detect the direction of arrival, the signal of the received signal is detected. The model needed to be calibrated. In particular, it is necessary to calibrate the impedance matrix including the impedance between the antenna elements of the array antenna as a component, and calibrate the relational expression between the control voltage value applied to the variable reactance element and the reactance value of the variable reactance element. Was. There has been a problem that the accuracy of this calibration greatly affects the accuracy of the detected radio wave arrival direction.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and to detect the angle of arrival of a radio wave using the array antenna disclosed in Patent Document 1, which does not require the above-described calibration and has a simple radio wave arrival direction. An object of the present invention is to provide a detection method and device.
[0008]
[Means for Solving the Problems]
The radio wave direction-of-arrival detection method according to the present invention includes an excitation element for receiving a radio signal, a plurality of non-excitation elements provided at a predetermined distance from the excitation element, and a connection to each of the non-excitation elements. And a variable reactance element. The array antenna changes the reactance value of each of the variable reactance elements, thereby operating each of the non-exciting elements as a director or a reflector, and changing the directional characteristics of the array antenna. In the method of detecting the direction of arrival of radio waves using
The same radio signal transmitted from a plurality of different azimuth directions different from each other of the array antenna is respectively transmitted to a plurality of different radiation patterns in which a plurality of different sets of reactance values of the respective variable reactance elements are respectively set. In the state described above, the signal level and phase of each received radio signal are detected by the array antenna, and the current steering vector specific to the array antenna is detected based on the detected signal level and phase of each radio signal. a_reaCalculating (θ);
When each of the plurality of different sets of reactance values of the variable reactance elements is set, the received signal y (t) received by the array antenna is detected, and the correlation representing the correlation between the plurality of received signals is detected. Matrix R_yy, And the calculated correlation matrix R_yyBy eigenvalue decomposition of_yyIs calculated, and each of the calculated eigenvectors and the current steering vector a are calculated._reaCalculating the MUSIC spectrum using the MUSIC method based on (θ), and calculating the angle of arrival of the received signal received by the array antenna based on the calculated MUSIC spectrum. And
[0009]
Also, the radio wave arrival direction detecting method according to the present invention includes an excitation element for receiving a radio signal, a plurality of non-excitation elements provided at a predetermined distance from the excitation element, and each of the non-excitation elements. A variable reactance element connected thereto, and by changing the reactance value of each of the variable reactance elements, each of the non-excitation elements operates as a director or a reflector, thereby changing the directional characteristics of the array antenna. In a radio wave direction-of-arrival detection device using an array antenna,
The same radio signal transmitted from a plurality of different azimuth directions different from each other of the array antenna is respectively transmitted to a plurality of different radiation patterns in which a plurality of different sets of reactance values of the respective variable reactance elements are respectively set. In the state described above, the signal level and phase of each received radio signal are detected by the array antenna, and the current steering vector specific to the array antenna is detected based on the detected signal level and phase of each radio signal. a_reaFirst control means for calculating (θ);
When each of the plurality of different sets of reactance values of the variable reactance elements is set, the received signal y (t) received by the array antenna is detected, and the correlation representing the correlation between the plurality of received signals is detected. Matrix R_yy, And the calculated correlation matrix R_yyBy eigenvalue decomposition of_yyIs calculated, and each of the calculated eigenvectors and the current steering vector a are calculated._rea(Θ) based on the calculated MUSIC spectrum, and second control means for calculating the angle of arrival of the received signal received by the array antenna based on the calculated MUSIC spectrum. It is characterized by having.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals.
[0011]
FIG. 1 is a block diagram showing a configuration of a radio wave direction-of-arrival detecting device according to an embodiment of the present invention. As shown in FIG. 1, the radio wave direction-of-arrival detecting device of this embodiment includes one excitation element A0 and six non-excitation elements A1 to A6. It includes a wave array antenna device (hereinafter, referred to as an array antenna device) 100, a radio receiver 4, a radio wave arrival direction detection computer 30, and a reactance value controller 10. Here, variable reactance elements 12-1 to 12-6 are loaded on each of the non-excitation elements A1 to A6, and the radio wave arrival direction detection computer 30 is constituted by, for example, a digital computer, and each of the variable reactance elements 12-1 to 12-6. When a plurality of different sets of reactance values of −6 are set, each received signal y (t) received by the array antenna apparatus 100 is detected, and a correlation matrix R representing a correlation between the plurality of received signals is detected._yy(See Equation 9 or Equation 17), and the calculated correlation matrix R_yyBy eigenvalue decomposition of_yyIs calculated, and the calculated eigenvector and a current steering vector a calculated in advance for the array antenna apparatus 100 are calculated._reaBased on (θ), a MUSIC spectrum is calculated using a known MUSIC method, and an arrival angle of a received signal received by the array antenna apparatus 100 is calculated based on the calculated MUSIC spectrum. .
[0012]
In FIG. 1, an array antenna device 100 includes an excitation element A0 and non-excitation elements A1 to A6 provided on a ground conductor 11, and the excitation element A0 includes six excitation elements A0 provided on a circumference having a radius r. It is arranged so as to be surrounded by the non-exciting elements A1 to A6. Preferably, the non-exciting elements A1 to A6 are provided at equal intervals on the circumference of the radius r. The length of the excitation element A0 and each of the non-excitation elements A1 to A6 are configured to be, for example, about λ / 4 (where λ is the wavelength of a desired wave), and is 0.23λ in the present embodiment. . The radius r is configured to be λ / 4. The grounding conductor 11 includes a disk-shaped upper surface having a radius of λ / 2 and a cylindrical skirt having a length of λ / 4 extending downward from an outer peripheral edge of the upper surface. The elevation angle of the main beam can be reduced. The feeding point of the excitation element A0 is connected to the low noise amplifier (LNA) 1 of the radio receiver 4 via the coaxial cable 9, and the non-excitation elements A1 to A6 are connected to the variable reactance elements 12-1 to 12-6, respectively. The reactance values of these variable reactance elements 12-1 to 12-6 are set by a reactance value signal from the reactance value controller 10.
[0013]
FIG. 2 is a longitudinal sectional view of the array antenna device 100. The excitation element A0 is electrically insulated from the ground conductor 11, and each of the non-excitation elements A1 to A6 is grounded at a high frequency to the ground conductor 11 via the variable reactance elements 12-1 to 12-6. The variable reactance elements 12-1 to 12-6 are, for example, variable capacitance diodes whose reactance values change when a control voltage (or bias voltage) is applied, and the control voltage is a reactance from the reactance value controller 10. It is applied in the form of a value signal. The reactance value controller 10 is a controller based on a digital signal processor, and refers to a digital voltage value preset in a reactance value table memory 20, and refers to six built-in D / A converters (not shown). ) To convert the digital voltage value into an analog control voltage value, and output and set the control voltage value as a reactance value signal to the variable reactance elements 12-1 to 12-6. On 100, each corresponding directional beam pattern is formed.
[0014]
The operation of the variable reactance elements 12-1 to 12-6 will be described. For example, when the longitudinal lengths of the excitation element A0 and the non-excitation elements A1 to A6 are substantially the same, for example, the variable reactance element 12-1 Has an inductance property (L property), the variable reactance element 12-1 becomes an extension coil, and the electrical length of the non-exciting elements A1 to A6 becomes longer than that of the exciting element A0, thus acting as a reflector. On the other hand, for example, when the variable reactance element 12-1 has a capacitance property (C property), the variable reactance element 12-1 becomes a shortening capacitor, and the electrical length of the non-excitation element A1 becomes shorter than that of the excitation element A0. , Work as a director. The same applies to the non-exciting elements A2 to A6 connected to the other variable reactance elements 12-2 to 12-6. Therefore, in the array antenna apparatus 100 of FIG. 1, by changing the reactance values of the variable reactance elements 12-1 to 12-6 connected to the non-exciting elements A1 to A6, the planar directivity characteristic of the array antenna apparatus 100 is changed. Can be changed.
[0015]
In the radio wave direction-of-arrival detection device shown in FIG.₁(T), and the received signal y (t), which is the received radio signal, is output from the coaxial cable 9 connected to the excitation element A0. The output received signal y (t) is input to the down converter 2 via the low noise amplifier 1 of the radio receiver 4, and the down converter 2 converts the input received signal into an intermediate frequency signal of a predetermined intermediate frequency. After the conversion, it is output to the A / D converter 3. The A / D converter 3 converts the input analog intermediate frequency signal into a digital intermediate frequency signal, and outputs the digital intermediate frequency signal to the radio wave arrival direction detection computer 30. Further, the radio wave direction-of-arrival detection computer 30 calculates the angle of arrival of the received radio signal based on the input intermediate frequency signal (for simplicity, represented as a received signal y (t)). The result is output to the CRT display 31 and displayed. Here, the radio wave direction-of-arrival detection computer 30 sets each received signal y () received by the array antenna apparatus 100 when a plurality of different sets of reactance values of the respective variable reactance elements 12-1 to 12-6 are set. t) and a correlation matrix R representing the correlation between the plurality of received signals._yy, And the calculated correlation matrix R_yyBy eigenvalue decomposition of_yyCompute the eigenvectors of. Next, the radio wave direction-of-arrival detection computer 30 calculates the calculated eigenvector and the current steering vector a unique to the array antenna apparatus 100 and calculated in advance and stored in the current steering vector memory 54._rea(Θ), the MUSIC spectrum is calculated using, for example, the MUSIC method disclosed in Non-Patent Document 1 or the like, and the angle of arrival of the received signal received by the array antenna apparatus 100 based on the calculated MUSIC spectrum. Is calculated.
[0016]
FIG. 3 is a block diagram showing a configuration of a pattern measuring device for acquiring a current steering vector used in the radio wave direction-of-arrival detecting device of FIG. Note that, in the “direct measurement method” which is the radio wave direction-of-arrival detection method according to the present embodiment, before estimating the arrival angle of an arbitrary radio signal using the radio wave direction-of-arrival detection device of FIG. The current steering vector of the array antenna device 100 is obtained by the experimental measurement used.
[0017]
In the pattern measuring apparatus of FIG. 3, inside the anechoic chamber 200, a horn antenna device 41 as a transmitting antenna and an array antenna device 100 as a receiving antenna mounted on the platform of the support 101 are mutually separated. It is installed at a distance of about 18 m. The horn antenna device 41 transmits a radio signal of an RF frequency of 2.484 GHz from the radio transmitter 40 to the array antenna device 100. The support table 101 to which the array antenna device 100 is attached is controlled by the azimuth and elevation angle controller 51 to rotate the array antenna device 100 about the excitation element A0 as a rotation axis to stop at a position of a predetermined azimuth angle θ. Further, the rotation axis can be inclined by a tilt angle φ (in this embodiment, referred to as an elevation angle) from a horizontal direction (the direction of the horizontal plane of the ground conductor 11) toward the direction in which the horn antenna device 41 is located.
[0018]
The wireless signal received by the array antenna device 100 is input to the wireless receiver 4 via the coaxial cable 9, and the wireless receiver 4 amplifies the received wireless signal, performs low-frequency conversion, and performs A / D conversion. Is performed to generate a digital intermediate frequency signal, and the received signal which is the intermediate frequency signal is output to the pattern measurement computer 50. The pattern measurement computer 50 measures the power and phase of the received signal input from the wireless receiver 4 in the in-phase (I) and quadrature (Q). At this time, a part of the wireless signal transmitted by the wireless transmitter 40 is branched and input to the pattern measuring computer 50, and the pattern measuring computer 50 determines the phase of the wireless signal input from the wireless transmitter 40. As a reference, the phase of the signal received from the wireless receiver 4 is measured.
[0019]
The pattern measurement computer 50 controls the azimuth and elevation controller 51 to control the support table 101 so that the array antenna device 100 receives radio signals from desired azimuth and elevation directions, and sets a reactance value. The controller 10 controls the array antenna device 100 to set a desired beam pattern. As in FIG. 1, the reactance value controller 10 is a controller based on a digital signal processor, and refers to a digital voltage value set in advance in a reactance value table memory 20 and includes six built-in D / A. The digital voltage value is converted into an analog control voltage value using a converter (not shown), and the control voltage value is output to the variable reactance elements 12-1 to 12-6 of the array antenna device 100 and set. I do.
[0020]
Each time the azimuth of the array antenna device 100 is changed in the direction in which the horn antenna device 41 is located, the pattern measurement computer 50 changes six different sets of six reactance values into the variable reactance element 12-1. To 12-6, and each time a set of these reactance values is set, the power and phase of the received signal are detected. The pattern measurement computer 50 calculates a current steering vector specific to the array antenna device 100 based on the detected power and phase of the received signal using a method described later in detail, and stores the current steering vector in the current steering vector memory 54. .
[0021]
In the present embodiment, the personal computer 50 detects the power and phase of the received signal, but the present invention is not limited to this, and the signal level and phase of the voltage or current of the received signal may be detected.
[0022]
Therefore, there are two measurement configurations in the pattern measurement device of FIG. The first configuration is used to acquire power and phase patterns, where the digital voltage corresponding to the control voltage set in the variable reactance elements 12-1 to 12-6 is fixed, and the array antenna device 100 The power and the phase pattern are measured by rotating the platform of the installed support 101. The second configuration is used to measure the I and Q channels output from array antenna device 100. In this configuration, the data of the incoming signal is modulated by binary phase shift keying (BPSK).
[0023]
The user can set parameters such as the elevation angle φ of the array antenna device 100, the step size of the change in the azimuth angle of the array antenna device 100, and the reactance value set in the array antenna device 100 using the input device 52 as an initial setting. It can be set in the measurement computer 50. The pattern measurement computer 50 outputs the measurement result of the current steering vector of the array antenna device 100 and the like to the CRT display 53 for display.
[0024]
As described above, the pattern measuring apparatus of FIG. 3 converts the same radio signal transmitted from a plurality of different azimuth directions of the array antenna apparatus 100 into the variable reactance elements 12-1 to 12-. 6 are received by the array antenna apparatus 100 in a state where a plurality of different sets of reactance values are set respectively, the power and the phase of each of the received radio signals are measured, and the power and the power of each of the measured radio signals are measured. Based on the phase, the current steering vector a unique to the array antenna device 100_rea(Θ) is calculated. This current steering vector a_rea(Θ) is stored in the current steering vector memory 54, and the current steering vector memory 54 is connected to the radio wave arrival direction detection computer 30 of the radio wave arrival direction detection device in FIG. Next, in the radio wave direction-of-arrival detection device, when the plurality of different sets of reactance values of the variable reactance elements 12-1 to 12-6 are set respectively, the received signals y ( t) and a correlation matrix R representing the correlation between the plurality of received signals._yy, And the calculated correlation matrix R_yyBy eigenvalue decomposition of the correlation matrix R_yy, And the calculated eigenvector and the current steering vector a_reaBased on (θ), the MUSIC spectrum is calculated using the MUSIC method, and the angle of arrival of the received signal received by the array antenna apparatus 100 is calculated based on the calculated MUSIC spectrum.
[0025]
Next, a signal model of a signal received by the array antenna device 100 and a formulation of the array antenna device 100 will be described below (see Non-Patent Document 3).
[0026]
The beam pattern of the array antenna apparatus 100 has a value x = [x of a reactance vector having the reactance values of the variable reactance elements 12-1 to 12-6 as components.₁, X₂, ..., x₆]^TIs formed by changing Where the superscript^TIndicates a transposition operation.
[0027]
The current steering vector of the array antenna device 100 is given as follows to the wavefront incident on the array antenna device 100 from the angle of arrival θ with respect to the axis formed by the non-excitation element A1, the excitation element A0, and the non-excitation element A6.
[0028]
(Equation 1)

[0029]
Where φ_m= 360 (m-1) / 6,0≤m≤6 is the azimuth in the direction in which the m-th parasitic element Am is located with respect to the direction in which the parasitic element A1 is located with respect to the exciting element A0. is there.
[0030]
A total of Q incoming signals u_q(T) exists and each incoming signal u_q(T) is the corresponding angle of arrival θ_qAssuming that (q = 1, 2,..., Q), the RF signal vector incident on the array antenna device 100 and represented by s (t) can be represented by the following equation.
[0031]
(Equation 2)

[0032]
According to this signal model, the received signal output from the array antenna device 100 can be represented by the following equation.
[0033]
(Equation 3)
y (t) = i^Ts (t) + n (t)
[0034]
Where n (t) is the additive white Gaussian noise signal and i is the RF current vector. For the sake of simplicity, the signal output from the array antenna device 100 and the signal output from the wireless receiver 4 are similarly referred to as a received signal y (t). The current vector i is determined by the reactance of the array antenna device 100, the mutual impedance between the antenna elements, and the RF source voltage V of the excitation element A0._s(See Non-Patent Document 3). This current vector i is formulated as follows.
[0035]
(Equation 4)
i = V_s(Z + X)^-1u₀
[0036]
Where V_sIs a constant, and X is a reactance matrix expressed by the following diagonal matrix.
[0037]
(Equation 5)
X = diag [50, jx₁, Jx₂, ..., jx₆]
[0038]
U₀Is a (6 + 1) -dimensional vector represented by the following equation.
[0039]
(Equation 6)
u₀= [1,0,0,0,0,0,0]^T
[0040]
Further, Z is a mutual impedance matrix represented by a (6 + 1) × (6 + 1) constant value matrix, and its components are constants determined by the mutual impedance between the antenna elements. Specifically, the following equation is obtained.
[0041]
(Equation 7)

[0042]
Since the structure of the array antenna apparatus 100 has cyclic symmetry, the independent components among the 49 components of the matrix Z are six components. These are complex parameters that should be called as follows from their physical meanings.
[0043]
[Table 1]
―――――――――――――――――――――――――――――――――――
z₀₀: Self-input impedance of the excitation element.
z₀₁: Coupling impedance between the excitation element and the non-excitation element.
z₁₁: Self-input impedance of the parasitic element.
z₁₂: Coupling impedance between two parasitic elements adjacent to each other.
z_Thirteen: Coupling impedance between two non-excited elements that are next to each other (adjacent to each other).
z₁₄: Coupling impedance between two non-exciting elements facing each other.
―――――――――――――――――――――――――――――――――――
[0044]
In the case of the array antenna apparatus 100, it can be seen that only signals on one antenna element can be measured, which is different from a conventional adaptive antenna in which signals on all antenna elements can be measured. Is different. Therefore, it can be seen that the impedance matrix Z cannot actually be completely estimated. Therefore, when calculating the current vector i using Equation 4, the accuracy of the estimated angle of arrival spectrum of MUSIC depends on the estimated impedance matrix Z (see Non-Patent Document 3).
[0045]
Next, the principle of the MUSIC algorithm in the reactance region applied to the case of the array antenna device 100 of the present embodiment will be described (see Non-Patent Document 4).
[0046]
First, a method of calculating a correlation matrix for the array antenna device 100 will be described. In the case of the array antenna apparatus 100, only the output signal of the single port connected to the excitation element A0 can be observed and measured, and the signals on the other six non-excitation elements A1 to A6 in the vicinity are obtained. It cannot be observed. Further, since the RF currents on the plurality of antenna elements are coupled to each other, the received signal output from the array antenna apparatus 100 is a non-linear function of a plurality of adjustable reactance values. Therefore, using only these adjustable reactance values and the measured reception signals output from the array antenna apparatus 100, the correlation matrix R_yyMust be calculated.
[0047]
For the calculation process, first consider the six non-exciting elements A1 to A6 of the array antenna apparatus 100. When the same incident signal transmitted six times is repeatedly transmitted, six reactance values By changing the value of the set (that is, the reactance vector) x six times, the spatial diversity of the array antenna device 100 can be obtained. Hereinafter, each reactance vector is represented by x^m, 1 ≦ m ≦ 6. FIG. 4 is a timing chart of signals received by the array antenna device 100 of FIG. The signal data incident on the array antenna apparatus 100 has P symbols S₁Or S_pEach block is a modulated signal that is repeated six times. Since the length of each symbol is time T, the total length of the signal data is 6T × P. Each time each block is received, a different set of reactance values is set in the array antenna apparatus 100. In FIG. 4, each set reactance vector component is represented by x₁ ^m, ..., x₆ ^mIt is represented by
[0048]
The above six reactance vectors x¹, ..., x⁶Are generated based on six sets each including a digital voltage value set in advance in the reactance value table memory 20 as a component. In order to make the six directional beam patterns of the array antenna device 100 formed by the six reactance vectors different from each other, for example, the control voltage values applied to the variable reactance elements 12-1 to 12-6 are changed. Digital voltage value v corresponding to each₁, V₂, ..., v₆Are circulated as shown in the following table, and six voltage value sets v composed of these digital voltage values are set.¹, V², ..., v⁶Is set in the reactance value table memory 20 in advance.
[0049]
[Table 2]

[0050]
In the present embodiment, the digital voltage value v₁, V₂, ..., v₆Is set in a cyclic manner as shown in Table 2 (hereinafter, this is referred to as a shift method). However, the present invention is not limited to this. The random number value generated by using the random number generation method is converted into a digital voltage value v₁, V₂, ..., v₆May be set. However, it is preferable not to use the digital voltage value of the omni pattern (that is, substantially the same value for each parasitic element).
[0051]
Next, each reactance vector x¹, ..., x⁶By observing the received signal output from the array antenna apparatus 100 in each case where is set, the following received signal vector is formed.
[0052]
(Equation 8)
y (t) = [y₁(T), ..., y_m(T), ..., y₆(T)]^T
[0053]
Where y_m(T) shows the m-th reactance vector x in the array antenna device 100.^mIs a received signal output from the array antenna device 100 and measured when is set. Finally, a correlation matrix R representing a correlation between a plurality of received signals received by the array antenna apparatus 100_yyCan be evaluated as follows:
[0054]
(Equation 9)
R_yy= E [y (t) y (t)^H]
[0055]
Where the superscript^HIndicates a Hermitian transpose operation.
[0056]
The signal received by each antenna element of the array antenna device 100 is a combination of an incident signal and noise as shown in Expression 3. Further, the current vector i is a combination of a constant value and a variable reactance value as shown in Expression 4. Therefore, one reactance vector x^mFor (m = 1, 2,..., 6), the received signal output from the array antenna device 100 can be expressed as follows.
[0057]
(Equation 10)

[0058]
Here, each incoming signal u received by the array antenna device 100_qAssume that (t), q = 1, 2,..., Q are synchronized and transmitted six times repeatedly. The received signal vector y (t) represents the current vector and the noise signal in each of the six iterations as i₁, ..., i₆And n₁, ..., n₆Can be expressed by Expression 11 or Expression 12 which is an equivalent form thereof.
[0059]
(Equation 11)

(Equation 12)
Y (t) = I^TAu (t) + n (t)
[0060]
Here, I is called a current matrix. Further, the current steering vector a_rea(Θ_q),
(Equation 13)

Equation 11 is expressed by the following equation.
[Equation 14]

Or equivalent format
[Equation 15]
y (t) = A_reau (t) + n (t)
Can be rewritten.
[0061]
Therefore, the estimated correlation matrix R of equation 9_yyBased on the corresponding expression (Equation 15) of the received signal vector of the array antenna apparatus 100, a calculation step of the MUSIC algorithm in the reactance region can be provided.
[0062]
<Step 1> From the received signal y (t) of the array antenna apparatus 100 measured when the signal as shown in FIG._yyIs calculated.
<Step 2> Correlation matrix R_yyBy performing the eigenvalue decomposition of₁, Λ₂,…, Λ₆And their corresponding eigenvectors e₁, E₂, ..., e₆Is calculated.
<Step 3> To determine the number D of arrival angles to be estimated (D <6), D eigenvalues larger than a fixed threshold T can be used, or the number of incident signals Is known, the number D is fixed.
<Step 4> Let the noise subspace matrix be E_N= [E_{D + 1}, E_{D + 2}, ..., e₆]. Where E_NIs an N-column matrix composed of the eigenvectors calculated in step 2, where N = 6-D. Therefore, by calculating the following equation for 0 ° ≦ θ <360 °, an estimated value of the MUSIC arrival angle spectrum can be derived.
[0063]
(Equation 16)

[0064]
Estimated angle of arrival θ_max(1, 2, ..., D) is the arrival angle spectrum P_MUThis is the value of the azimuth angle θ when (θ) is maximized.
[0065]
Steps 1 to 4 described above are performed by the radio wave direction-of-arrival detection device of FIG._rea(Θ) needs to be obtained in advance before executing these steps. The acquisition of the current steering vector is performed by the pattern measuring device of FIG.
[0066]
Next, in order to describe a method for obtaining the current steering vector, the arrival angle spectrum P_MUTwo experimental methods for estimating (θ) will be described.
[0067]
Since the discrete time value is actually used in the MUSIC algorithm of the present embodiment, the received signal (see Equation 3) output from the array antenna device 100 is represented by y [k] as y [k] = y (kT). Is represented by Here, k is an index of discrete time, and T is a constant corresponding to the time sample rate.
[0068]
First, the correlation matrix R of the array antenna device 100_yyThe calculation of will be described. As shown in FIG. 4, signal data incident on the array antenna apparatus 100 has P symbols S₁Or S_pEach block is a modulated signal that is repeated six times. Different sets of reactance values are used for each block.
[0069]
Correlation matrix R representing correlation between a plurality of received signals_yyIs estimated based on the received signal as shown in FIG.
[0070]
[Equation 17]

[0071]
Where the superscript^*Represents a complex conjugate.
[0072]
The two methods described below, that is, the equivalent weight vector method similar to the method of the conventional example described in Non-Patent Document 4 and the direct measurement method according to the embodiment of the present invention, use the current steering vector a_reaThe method for obtaining (θ) is different.
[0073]
First, the arrival angle spectrum P of the MUSIC by the equivalent weight vector method (EWV method)_MUThe calculation method of (θ) will be described. The reactance value, which is the weight loaded on the m-th parasitic element Am, is a digital voltage value v_mThe control voltage value corresponding to (m = 1, 2,..., 6) is changed by setting the variable reactance element 12-m. Reactance value x_mAnd the digital voltage value v_mIs approximated by the following equation.
[0074]
(Equation 18)
x_m= -0.0217v_m-49.21
[0075]
The reactance value controller 10 stores a preset value of −2048 ≦ v in the reactance value table memory 20._mDigital voltage value v having a value of ≦ 2047_mIs converted to an analog control voltage value using a built-in digital / analog converter (not shown), and this control voltage value is output to the variable reactance element 12-m as a reactance value signal and set. . At this time, the reactance value x set in the variable reactance element 12-m_mIs in the range of −93.63Ω ≦ x_m≦ −4.77Ω.
[0076]
Current matrix I^TTo calculate (see Equation 12), the equation of the current vector i given in Equation 4 is used. More precisely, each set of digital voltages v^m= [V₁, V₂, ..., v₆], The set of digital voltages v^mIs the reactance vector x^m= [X₁, X₂, ..., x₆], The reactance vector x^mSet of digital voltages instead of^mBased on the current vector i_mForm a reactance matrix X used in the calculation of (see Equation 4). By repeating this process for the six reactance vectors, the current matrix I used to calculate the MUSIC angle-of-arrival spectrum is obtained.^TFrom the current steering vector a_rea(Θ) can be obtained.
[0077]
In this method, the current matrix I^TAnd thus the angle of arrival spectrum of MUSIC (see Equation 16) estimate the impedance matrix Z and the relationship between the reactance value and its equivalent digital voltage value used to obtain the reactance value Note that this is derived by Therefore, these parameters must be calibrated to improve the accuracy of the angle of arrival spectrum.
[0078]
Next, the arrival angle spectrum P of the MUSIC using the direct measurement method (DM method)_MUThe calculation method of (θ) will be described. In the above-described equivalent weight vector method, it is necessary to estimate the impedance matrix Z and the relationship between digital voltage values and reactance values for a given array antenna. The accuracy of the obtained MUSIC angle-of-arrival spectrum strongly depends on these estimates. In the direct measurement method, the angle of arrival spectrum is calculated using only directly measured data.
[0079]
The method is based on a noise-free assumption, where one constant incoming signal (ie, continuous wave signal) u (t) coming from the direction of azimuth θ (eg, for any t, u (t) = K = 1) and the reactance vector x, based on the idea that the received signal (see Equation 3) output from the array antenna apparatus 100 is expressed by the following equation.
[0080]
[Equation 19]
y (t) = i^Ta (θ) u (t) = i^Ta (θ)
[0081]
This can be estimated by measuring the power and phase of the received signal output from the array antenna device 100. As shown in FIG. 3, a part of the wireless signal transmitted by the wireless transmitter 40 is branched and input to the pattern measurement computer 50, and the wireless communication input from the wireless transmitter 40 is input to the pattern measurement computer 50. The phase of the received signal input from the wireless receiver 4 is measured based on the phase of the signal.
[0082]
By measuring the power and phase of the received signal output from the array antenna device 100 for each of the six reactance vectors, the following current steering vector can be obtained for a given azimuth θ.
[0083]
(Equation 20)

[0084]
Next, the arrival angle spectrum of MUSIC is calculated for 0 ° ≦ θ <360 ° using Expression (16).
[0085]
The values of the azimuth angles θ of the array antenna device 100 are fixed to different values (for example, θ = 0 °, 1,..., 359 °), and six reactance vectors given in advance are set in the array antenna device 100, respectively. Each time, the measured value of each received signal received in the beam pattern corresponding to each reactance vector and the matrix E calculated based on the received signal_NAnd the angle of arrival P_MUNote that (θ) is formed. Also, if each of the received signals received in the six beam patterns is measured only once (accordingly, from Equation 19, once the current steering vector is obtained), the same signals incident at different angles of arrival are obtained. An arrival angle estimate can be generated for each signal u (t). Similarly, when acquiring an estimated angle of arrival when the elevation angle is changed in Experiment 3 to be described later, if each of the received signals received in the six beam patterns is measured only once, a different elevation angle is used. An estimate of the angle of arrival can be generated for each of the same incoming signals u (t).
[0086]
As described above, the pattern measuring apparatus of FIG. 3 converts the same radio signal transmitted from a plurality of different azimuth directions of the array antenna apparatus 100 into different reactance values of the variable reactance elements. A plurality of sets are received by the array antenna device 100 in a set state, and the power and phase of each of the received radio signals are measured. Based on the measured power and phase of each of the radio signals, the array antenna Current steering vector a specific to device 100_rea(Θ) is calculated. This current steering vector a_rea(Θ) is stored in the current steering vector memory 54, and the current steering vector memory 54 is connected to the radio wave arrival direction detection computer 30 of the radio wave arrival direction detection device in FIG.
[0087]
【Example】
Hereinafter, the arrival angle spectrum obtained as an experimental result of the radio wave direction-of-arrival detection device of the present embodiment will be described. The measurement by the experiment was performed in the anechoic chamber 200 using the pattern measuring apparatus shown in FIG. In this case, the azimuth and elevation angle controller 51 rotates and fixes the array antenna device 100 using the support 101 so that the radio signal is incident on the array antenna device 100 at a predetermined arrival angle. The same operation as the radio wave arrival direction detection computer 30 is executed to detect the arrival angle of the radio signal.
[0088]
<Experiment 1 and Experiment 2>
The purpose of the following experiment is to estimate the arrival angle of one incident signal using the MUSIC algorithm in the reactance region by the array antenna device 100. Here, it is assumed that the total number of incident signals Q = D = 1. The experiment is performed for comparison by the two methods of the equivalent weight vector method described above and the direct measurement method.
[0089]
Correlation matrix R_yyThe size of the symbol block used to calculate is P = 200. The data of the incident signal is modulated by binary phase shift keying (BPSK), and the signal power is about 10 dBm.
[0090]
For each of the methods described above, two sets of experiments were performed (Experiment 1 and Experiment 2). In these experimental sets, the selected reactance vector (that is, the set of digital voltage values stored in advance in the reactance value table memory 20) differs from the arrival angle of the incoming signal. The direct measurement method is called a DM method, and the equivalent weight vector method is called an EWV method. 5 and 6 show experimental results of the radio wave direction-of-arrival detecting device of FIG. 1 and show a method of obtaining an arrival angle estimation value from the arrival angle spectrum of MUSIC in Experiment 1. FIG. 5 shows the arrival angle spectrum P when the arrival angle is 30 °._MU6 is a graph showing (θ), and FIG. 6 shows an arrival angle spectrum P at an arrival angle 140 °._MUIt is a graph which shows ((theta)). Table 3 further summarizes the angle-of-arrival estimates for both the DM method and the EWV method when the angles of arrival are 60 °, 90 °, and 120 °.
[0091]
[Table 3]
Estimated angle of arrival for two methods (Experiment 1)
――――――――――――――――――――――――――――――――――――
Arrival angle 30 ° 60 ° 90 ° 120 ° 140 °
――――――――――――――――――――――――――――――――――――
Angle of arrival estimation
DM method 29 ° 59 ° 88 ° 123 ° 143 °
EWV method 24 ° 42 ° 89 ° 108 ° 146 °
――――――――――――――――――――――――――――――――――――
[0092]
7 and 8 show experimental results of the radio wave direction-of-arrival detecting device, and show a method of obtaining an estimated angle of arrival from the MUSIC arrival angle spectrum in Experiment 2. FIG. 7 shows the arrival angle spectrum P when the arrival angle is 0 °._MUFIG. 8 is a graph showing an arrival angle spectrum P at an arrival angle of 60 °._MUIt is a graph which shows ((theta)). Table 4 further summarizes the angle-of-arrival estimates for both the DM method and the EWV method when the angles of arrival are 30 ° and 120 °.
[0093]
[Table 4]
Angle-of-arrival estimates for the two methods (Experiment 2)
――――――――――――――――――――――――――――――――――――
Arrival angle 0 ° 30 ° 60 ° 120 °
――――――――――――――――――――――――――――――――――――
Angle of arrival estimation
DM method 2 ° 32 ° 60 ° 117 °
EWV method -7 ° 22 ° 55 ° 110 °
――――――――――――――――――――――――――――――――――――
[0094]
Tables 3 and 4 clearly show that the accuracy of the estimated angle of arrival is higher in the DM method than in the EWV method. Here, if the arrival angle values are the same, the two experiments differ only in the reactance vector, and when the two methods are compared in both Experiments 1 and 2, the relative error of the DM method is 0 ° to 3 °. Thus, it can be said that the relative error of the EWV method is 5 ° to 18 °. In the case of the DM method, the error of the relative angle estimation value is constant, and the arrival angle spectrum has a sharper and higher maximum level value (unit: dB) than the EWV method. This can be explained by the fact that in the EWV method, the accuracy of the estimated angle of arrival depends on the estimated impedance matrix Z. In this case, the impedance matrix needs to be calibrated for better results. Since no impedance matrix is used in the DM method, the calibration problem is immediately resolved.
[0095]
<Experiment 3>
The purpose of the following experiment is to estimate the arrival angle of one incident signal by using the MUSIC algorithm in the reactance region by the array antenna device 100 for different elevation angles. Direct measurement was used to estimate the direction of arrival.
[0096]
FIG. 3 shows a configuration and a positional relationship between the array antenna device 100 as a receiving antenna and the horn antenna device 41 as a transmitting antenna. Due to the structural limitations of the array antenna device 100 and the support 101, the signal transmitted by the horn antenna device 41 arrives on the array antenna device 100 in a 90 ° direction. The experiment was performed at an elevation angle from 0 ° to 30 ° with the vertical axis of the array antenna device 100 (that is, the excitation element A0) inclined toward the horn antenna device 41.
[0097]
Correlation matrix R_yyTo estimate each reactance vector x^mFor (m = 1,..., 6), the corresponding received signals output and measured from the array antenna apparatus 100 used 200 symbols for each channel (I and Q channels). Throughout all experiments, the power of the transmitted radio signal was about 10 dBm.
[0098]
First, an example of arrival angle estimation using the MUSIC algorithm will be described. FIG. 9 shows an experimental result of the radio wave direction-of-arrival detecting apparatus of FIG. 1, and shows the arrival angle spectrum P when the arrival angle is 90 ° and the elevation angle is 10 ° in Experiment 3._MUIt is a graph which shows ((theta)). The angle value at which the curve in FIG. 9 is maximized matches the estimated arrival angle of the signal incident on array antenna apparatus 100.
[0099]
FIG. 10 is a table showing arrival angle estimation values when the arrival angle is 90 ° and the elevation angles are 0 ° to 30 °. The angle of arrival of the incoming signal was fixed at 90 °. The arrival angle estimation value θ by the MUSIC algorithm was obtained for an elevation angle (tilt angle) φ from 0 ° to 30 °. The measured angles are summarized in the table of FIG.
[0100]
These measurements show that the average of the estimated angles is about 88.2 ° and the standard deviation angle is 3.8 °. The standard deviation of the angle of arrival spectrum by MUSIC is about 1.3 dB. From these results, it can be said that for elevation angles less than 30 °, the global accuracy of the estimated angle does not change.
[0101]
In the present embodiment, we have proposed two experimental methods for estimating the angle of arrival of a signal incident on the array antenna device 100. The experimental results (Experiment 1 and Experiment 2) show that the angle of arrival of the incident signal can be estimated with an accuracy of about 3 °, especially when the direct measurement method is used. Also, the correlation matrix R_yyIt is also important to note that the calculation of was performed using only P = 200 symbol samples. Experiments showed that the direct measurement method proposed in the present invention not only improved the accuracy of the estimated angle, but also calibrated the impedance parameters used in modeling the received signal output from the array antenna apparatus 100. It has solved a serious problem.
[0102]
In Experiment 3, we further examined the effect of the elevation angle with respect to the array antenna device 100 on the estimated angle value calculated using the MUSIC algorithm in the reactance region. Experimental results show that elevation does not affect the accuracy of the estimated angle. In an application for estimating the direction of arrival, statistics performed based on experimental results indicate that an accuracy of about 4 ° can be expected when the elevation angle is less than 30 °. Experiments performed at different elevation angles show that by using the MUSIC algorithm in the reactance domain for the array antenna device 100, the arrival angle estimation can be performed without sacrificing efficiency.
[0103]
<Modification>
In the embodiment described above, the array antenna device 100 having (6 + 1) elements is used. However, it is apparent that the direction of arrival of a radio wave can be similarly detected using an array antenna device having any number of non-exciting elements. Would.
[0104]
In the experiment, it was confirmed that the MUSIC algorithm in the reactance area could be used effectively to find the angle of arrival of one incoming signal. Many experimental configurations using the antenna device 100 can be investigated.
[0105]
As described above, according to the radio wave direction-of-arrival detection device of the embodiment according to the present invention, it is possible to simultaneously detect a plurality of radio wave directions of arrival with high detection accuracy, and to detect a radio wave direction independent of a strictly calibrated signal model. A direction finding device can be provided. Further, the hardware circuit can be simplified as compared with the conventional radio wave arrival direction detecting method. The experimental results show that the direction of arrival of one incident signal can be estimated with an error accuracy within 3 °, and that the estimated value of the angle of arrival is not affected by the elevation angle (0 ° to 30 °) of the incident signal. It is shown that. In other words, it is possible to estimate and calculate the radio wave arrival angle with high accuracy even when the camera shake occurs (when the elevation angle changes) when the electronically controlled waveguide array antenna device serving as the receiving unit is held by hand. Has unique effects.
[0106]
【The invention's effect】
As described above in detail, according to the radio wave direction-of-arrival detection method or apparatus according to the present invention, in a radio wave direction-of-arrival detection method or apparatus using a known electronically controlled waveguide array antenna apparatus, a plurality of different array antennas are used. The same radio signal transmitted from the direction of the predetermined azimuth angle is received by the array antenna in a state of a plurality of different radiation patterns in which a plurality of different sets of reactance values of the respective variable reactance elements are respectively set. Detecting a signal level and a phase of each of the received radio signals, and, based on the detected signal levels and phases of the respective radio signals, a current steering vector a unique to the array antenna;_reaAfter calculating (θ), the reception signals y (t) received by the array antenna when the plurality of different sets of reactance values of the variable reactance elements are set are detected, and the plurality of reception signals y (t) are detected. Correlation matrix R representing correlation between received signals_yy, And the calculated correlation matrix R_yyBy eigenvalue decomposition of_yyIs calculated, and each of the calculated eigenvectors and the current steering vector a are calculated._rea(Θ), the MUSIC spectrum is calculated using the MUSIC method, and the angle of arrival of the received signal received by the array antenna is calculated based on the calculated MUSIC spectrum.
[0107]
Therefore, it is possible to provide a radio wave arrival direction detecting device that can simultaneously detect a plurality of radio wave arrival directions with high detection accuracy and does not depend on a signal model that requires strict calibration. Further, the hardware circuit can be simplified as compared with the conventional radio wave arrival direction detecting method. Furthermore, even when the electronically controlled waveguide array antenna device serving as the receiving unit is hand-held and camera shake occurs (when the elevation angle is changed), it is possible to estimate and calculate the radio wave arrival angle with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a radio wave direction-of-arrival detecting apparatus according to an embodiment of the present invention.
FIG. 2 is a sectional view showing a detailed configuration of the array antenna device 100 of FIG.
FIG. 3 is a block diagram showing a configuration of a pattern measuring device for acquiring a current steering vector used in the radio wave direction-of-arrival detecting device of FIG.
FIG. 4 is a timing chart of signals received by the array antenna device 100 of FIG.
5 is an experimental result of the radio wave direction-of-arrival detecting device of FIG._MUIt is a graph which shows ((theta)).
6 is an experimental result of the radio wave direction-of-arrival detecting device of FIG._MUIt is a graph which shows ((theta)).
7 is an experimental result of the radio wave direction-of-arrival detection device of FIG._MUIt is a graph which shows ((theta)).
8 is an experimental result of the radio wave direction-of-arrival detecting device of FIG._MUIt is a graph which shows ((theta)).
9 is an experimental result of the radio wave direction-of-arrival detecting device of FIG. 1, and shows an arrival angle spectrum P at an arrival angle of 90 ° and an elevation angle of 10 ° in Experiment 3. FIG._MUIt is a graph which shows ((theta)).
FIG. 10 is a table showing experimental results of the radio wave direction-of-arrival detecting device of FIG. 1, showing estimated values of arrival angles at an arrival angle of 90 ° and elevation angles of 0 ° to 30 ° in Experiment 3;
[Explanation of symbols]
A0: Exciting element,
A1 to A6: parasitic element,
1. Low noise amplifier (LNA),
2. Down converter,
3. A / D converter,
4 ... Wireless receiver,
9 ... coaxial cable,
10. Reactance value controller,
11 ground conductor
12-1 to 12-6: variable reactance element,
20: Reactance value table memory,
30 ... A radio wave direction of arrival detection computer,
31, 53… CRT display,
40 ... wireless transmitter,
41 ... horn antenna device,
50 ... Pattern measurement computer,
51 ... azimuth and elevation angle controller,
52 input device,
54 ... current steering vector memory
100 ... array antenna device,
101 ... support base,
200 ... Anechoic chamber.

Claims (2)

An excitation element for receiving a radio signal, a plurality of non-excitation elements provided at a predetermined distance from the excitation element, and a variable reactance element respectively connected to each of the non-excitation elements; By changing the reactance value of the variable reactance element, each of the non-excited elements is operated as a director or a reflector, and a radio wave arrival direction detecting method using an array antenna that changes the directional characteristic of the array antenna,
The same radio signal transmitted from a plurality of different azimuth directions different from each other of the array antenna is respectively transmitted to a plurality of different radiation patterns in which a plurality of different sets of reactance values of the respective variable reactance elements are respectively set. In the state, the signal level and phase of each received radio signal are detected by the array antenna, and based on the detected signal level and phase of each radio signal, a current steering vector unique to the array antenna is detected. calculating a a _rea (θ),
When each of the plurality of different sets of reactance values of the variable reactance elements is set, the received signal y (t) received by the array antenna is detected, and the correlation representing the correlation between the plurality of received signals is detected. the matrix R _yy is calculated, by eigenvalue decomposition of each correlation matrix R _yy which is above the calculated eigenvectors of each correlation matrix R _yy, and the calculated respective eigenvectors and the current steering vector a _rea was _(theta) Calculating the MUSIC spectrum using a MUSIC (Multiple Signal Classification) method based on the MUSIC, and calculating the angle of arrival of the received signal received by the array antenna based on the calculated MUSIC spectrum. Characteristic radio wave arrival direction detection method. An excitation element for receiving a radio signal, a plurality of non-excitation elements provided at a predetermined distance from the excitation element, and a variable reactance element respectively connected to each of the non-excitation elements; By changing the reactance value of the variable reactance element, each of the non-excited elements is operated as a director or a reflector, and in a radio wave arrival direction detecting device using an array antenna that changes the directional characteristics of the array antenna,
The same radio signal transmitted from a plurality of different azimuth directions different from each other of the array antenna is respectively transmitted to a plurality of different radiation patterns in which a plurality of different sets of reactance values of the respective variable reactance elements are respectively set. In the state, the signal level and phase of each received radio signal are detected by the array antenna, and based on the detected signal level and phase of each radio signal, a current steering vector unique to the array antenna is detected. first control means for calculating the a _rea (θ),
When each of the plurality of different sets of reactance values of the variable reactance elements is set, the received signal y (t) received by the array antenna is detected, and the correlation representing the correlation between the plurality of received signals is detected. the matrix R _yy is calculated, by eigenvalue decomposition of each correlation matrix R _yy which is above the calculated eigenvectors of each correlation matrix R _yy, and the calculated respective eigenvectors and the current steering vector a _rea was _(theta) A second control means for calculating a MUSIC spectrum using a MUSIC (Multiple Signal Classification) method based on the MUSIC method, and calculating an angle of arrival of a received signal received by the array antenna based on the calculated MUSIC spectrum. Direction of arrival of radio waves characterized by having Apparatus.

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