JP3721406B2 - Radio power antenna estimation method - Google Patents

Description

【００１７】
で与えられる。
【００１８】
ここで、σ² はマルチパス波の電力、Ａ² ／２は直接波の電力、Ｉ₀ は０次（0th-order ）変形ベッセル関数である。式（１）は２つのパラメータＡとσを含んでいる。ここで新たなパラメータρ（直接波の電力とマルチパス波の電力との比）
【００１９】
【数２】

【００２０】
を定義し、包絡線ｒを直接波とマルチパス波の電力和の平方根で規格化すると、
【００２１】
【数３】

【００２２】
ただし、
【００２３】
【数４】

【００２４】
と表される。ここで分子の係数１／√２は包絡線の２乗平均を１にするために付けている。
【００２５】
包絡線の２乗平均は、
Ｅ［ｒ² （ｔ）］＝Ａ² ＋２σ² （５）
で与えられる。従って、
【００２６】
【数５】

【００２７】
となる。
【００２８】
式（３）をＲで積分することにより、例えば、図２に示す累積分布関数Ｆ（Ｒ）（ＣＤＦ：Cumulative distribution function）が算出される。この累積分布関数Ｆ（Ｒ）（ＣＤＦ）が、本発明における電界強度累積分布関数である。
【００２９】
単位階段関数（ステップ関数）をＵとするとき、ρ→∞のときはＦ（Ｒ）＝Ｕ（Ｒ−１）となり、ρ＝０のときはレイリー分布になるから、Ｆ（Ｒ）＝１−ｅｘｐ（−Ｒ² ）となる。したがって累積確率１−ｅ^-1＝０．６３２において両者は交叉する。両者の中間のρに対しては、交叉点はずれるが、累積確率０．６３２において、そのずれは高々０．５ｄＢであることが判る（図２参照）。すなわち電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値はρに関わらずほぼ一定の値になる。これは、反射箱内がレイリー分布でもライス分布でも電力和の平方根で規格化すれば、一定の値となるということである。
【００３０】
本発明では、この電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値がほぼ一定であることを利用して、無線機空中線電力を推定する。具体的な推定方法については後述する。
【００３１】
次に、電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値がほぼ一定であることを具体的に検証する。図３は、本発明の実施の形態において測定に用いた反射箱の諸元を示す図である。
【００３２】
反射箱５のサイズは、５．５ｍ×４．５ｍ×３ｍである。反射箱５内の攪拌翼（スターラー）のサイズは２ｍ×０．７ｍ、設置場所は、天井、正面、右、左の壁からの距離７０ｃｍの位置、回転速度は、最高１２０ｒｐｍであり、４枚別々に回転可能である。また、シールド特性は、１５０ＭＨｚ−１０ＧＨｚに対して１００ｄＢ以上、１８ＧＨｚに対して９０ｄＢ以上である。
【００３３】
図４は、本発明の実施の形態において測定に用いた統計量測定装置６の諸元を示す図である。統計量測定装置６はスペクトルアナライザ（スペアナ）のビデオ出力信号をＡ／Ｄ変換し、指定された時間区間における種々の統計量を実時間計測する装置である。
【００３４】
統計量測定装置６の単位観測時間は、約１秒、欠測時間は、約１０ミリ秒、サンプリング速度は、２０Ｍサンプル／秒（５０ｎｓ）、振幅分解能は、２５６段階である。統計量測定装置６としては、例えば、ＡＰＤ測定装置などを用いることができる。
【００３５】
また、測定可能データは、確率密度分布（ＰＤＦ：Ｐｒｏｂａｂｉｌｉｔｙ ｄｅｎｓｉｔｙ ｆｕｎｃｔｉｏｎ）、振幅確率分布（１−ＣＤＦに対応）（ＡＰＤ：Ａｍｐｌｉｔｕｄｅ ｐｒｏｂａｂｉｌｉｔｙ ｄｉｓｔｒｉｂｕｔｉｏｎ）、交差率分布（ＣＲＤ：Ｃｒｏｓｓｉｎｇ ｒａｔｅ ｄｉｓｔｒｉｂｕｔｉｏｎ）、パルス幅分布（ＰＤＤ：Ｐｕｌｓｅ ｄｕｒａｔｉｏｎ ｄｉｓｔｒｉｂｕｔｉｏｎ）、パルス間隔分布（ＰＳＤ：Ｐｕｌｓｅ ｓｅｐａｒａｔｉｏｎ ｄｉｓｔｒｉｂｕｔｉｏｎ）である。
【００３６】
ここで、反射箱５内では、無線機から送信された電波が壁や攪拌翼で反射するので、受信アンテナにはその振幅がランダムに変動する信号が受信される。しかし、このランダムな信号は攪拌翼の配置状況に依存するので周期性を持っている。従ってその周期に対応した時間のデータを取得することにより適正なデータ処理が可能になる。そのため、適切なデータ取得時間を得るために受信信号の自己相関関数を求めた。
【００３７】
図５の網かけ部分は、後述する図１１に示す反射箱５において、回転速度を攪拌翼Ｂ：１２０ｒｐｍ、攪拌翼Ｄ：１１７ｒｐｍとした場合の統計量測定装置６により得られた測定値（ＰＤＦ，測定時間１秒）をプロットしたものである。５分間での各測定データ（３００本、網かけ部分）はランダム信号の周期に満たないため、ばらつきが大きく、このままでは適切なデータ処理が不可能であることがわかる。
【００３８】
攪拌翼の配置状況に依存する受信ランダム信号の周期ｔは、第１の攪拌翼と第２の攪拌翼の回転速度をｆ₁ 及びｆ₂ とし、Ｎ₁ とＮ₂ を整数としたとき、
ｔ＝（Ｎ₁ −Ｎ₂ ）／２（ｆ₁ −ｆ₂ ） （７）
で求まる。例えば、第１の攪拌翼の回転速度を１２０ｒｐｍ、第２の攪拌翼の回転速度を１１７ｒｐｍとした場合のランダム信号の周期は式（７）からｔ＝１０秒と計算される。以下、図６の測定系統を用いて、上記計算結果を検証する。
【００３９】
図６において、７は電波信号を発生する信号発生器、８はスペクトルアナライザ、９はスペクトルアナライザのビデオ出力を測定するデジタルオシロスコープ、５１は電波を送信する送信アンテナ、１２は反射箱、５２は電波を受信する受信アンテナ、５３は攪拌翼Ａ、５４は攪拌翼Ｂ、５５は攪拌翼Ｃ、５６は攪拌翼Ｄである。
【００４０】
信号発生器７から１ＧＨｚ、０ｄＢの出力を送信アンテナ５１に加え、受信アンテナ５２の受信レベルをスペクトルアナライザ８で受信する。スペクトルアナライザ８はゼロスパンとし、スペクトルアナライザ８のビデオ出力をデジタルオシロスコープ９（２０ｋｓａｍｐｌｅ／ｓｅｃ）で測定する。このデジタルオシロスコープ９の時系列データから自己相関時間を求めると、図７のように、式（７）を用いたランダム信号の周期の計算結果と同じく１０秒毎に自己相関がとれていることがわかる。
【００４１】
ここで、後述する図１１の反射箱５内における攪拌翼Ｂ５４の回転速度を１２０ｒｐｍ、攪拌翼Ｄ５６の回転速度を１１７ｒｐｍ、攪拌翼Ａ５３、攪拌翼Ｃ５５の回転速度を０ｒｐｍの設定で、１０秒を測定時間としたときの５分間のＰＤＦ測定結果を図５の実線（黒線部分）に示す。このデータは３０本の線に該当するが、それらはほぼ重なっており、統計量取得に適切なデータ処理が可能になると思われる。
【００４２】
以上の自己相関の分析結果から、本発明の実施の形態では、反射箱内の攪拌翼Ｂ５４と攪拌翼Ｄ５６の攪拌翼の回転速度をそれぞれ１２０ｒｐｍと１１７ｒｐｍ、単位測定時間１０秒間としたデータを用いて解析を行った。
【００４３】
また、本発明の実施の形態で用いた統計量測定装置６は、信号強度をＡ／Ｄ変換し、そのＡＤＣコードに対応した確率分布を求める。図８にＡＤＣコードに対応するスペアナ指示値を示す。この図からＡＤＣコードとスペアナ指示値とが直線性よく対応できていることがわかる。
【００４４】
反射箱内で、送信アンテナと受信アンテナを対向させた場合、送信アンテナから放射された電波は、受信アンテナにおいて直接波のみではなく攪拌翼や壁で反射されたマルチパス波（マルチパス波）との合成波が受信される。そこで、電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値がほぼ一定であることを検証するため、以下の測定を行った。
【００４５】
受信される合成波のうち、直接波のみを測定するために図９の測定系統図により、６面の電波暗箱において測定を行った。
【００４６】
図９において、１１は電波暗箱、１００は送信アンテナ、１０１は受信アンテナである。信号発生器７により発生した電波信号に基づき、送信アンテナ１００から受信アンテナ１０１へ電波を発信し、受信アンテナ１０１において受信された電波レベルをスペクトルアナライザ８で受信し、スペクトルアナライザ８の出力を統計量測定装置６で測定する。この場合、マルチパス波は存在せず直接波のみであるため、ρは∞に近く包絡線レベルの変動がない。
【００４７】
次に、マルチパス波のみを測定するため、反射箱内に金属フェンスを送受アンテナ間に設置し、攪拌翼を回転させ図１０に示す測定系統図により測定を行った。
【００４８】
図１０において、１３は反射箱、５７は金属フェンスである。なお、受信アンテナ５２には壁や攪拌翼から反射した電波が様々な角度から受信されるため、受信アンテナ５２の方向をＸ（Ｈｏｒｉｚｏｎｔａｌ ０ｄｅｇ）、Ｙ（Ｈｏｒｉｚｏｎｔａｌ ９０ｄｅｇ）、Ｚ（Ｖｅｒｔｉｃａｌ ０ｄｅｇ）と変えた場合それぞれについて測定を行った。この場合直接波は存在しないのでρは０に近い。
【００４９】
また、直接波とマルチパス波との合成波を受信するため、図１０の測定系統図の金属フェンス５７を取り除き、図１１に示す測定系統で反射箱５内の攪拌翼を回転させ測定を行った。なお、本来直接波は受信アンテナ５２がＸ方向のもののみ受信されるはずであるが、マルチパス波測定時と同様に受信アンテナ５２の方向をＸ，Ｙ，Ｚと変えて測定を行った。直接波とマルチパス波の電力比ρは不明であるが、理論によると累積確率６３．２％値はρに依存しないはずである。
【００５０】
図１２（Ａ）は図９の測定系統で測定した直接波の測定結果（ＣＤＦ）、図１２（Ｂ）は図１０の測定系統で測定したマルチパス波の測定結果（ＣＤＦ）、図１２（Ｃ）は図１１の測定系統で測定した合成波の測定結果（ＣＤＦ）である。横軸は電力和の平方根で規格化したＲである。
【００５１】
図１２（Ａ）に示す直接波は、受信アンテナ１０１がＸ方向のものである。また、図１２（Ｂ）に示すマルチパス波は、受信アンテナ５２の向きがＸ，Ｙ，およびＺ方向の場合の測定結果が重なっている。このことから、マルチパス波は受信アンテナ５２の向きを変えても一様な信号であることがわかる。
【００５２】
図１２（Ｃ）に示す合成波は、受信アンテナ５２の向きを変えた場合にレベルの変動がある。そこで、受信アンテナ５２の向きをＸ，Ｙ，およびＺと変えて受信した信号を平均することにより、受信アンテナ５２のすべての向きによる信号を受信していると考え、図１３（Ａ）に直接波のＣＤＦおよび受信アンテナ５２の向きがＸ方向，Ｙ方向，およびＺ方向の測定結果を平均したマルチパス波と合成波のＣＤＦ、図１３（Ｂ）に直接波のＰＤＦおよび受信アンテナ５２の向きがＸ方向，Ｙ方向，およびＺ方向の測定結果を平均したマルチパス波と合成波のＰＤＦを示す。
【００５３】
図１３（Ａ）によると、直接波、マルチパス波及び合成波が電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値において交叉しており、原理と同様に累積確率６３．２％値は直接波の電力とマルチパス波の電力との比ρに依拠しないことがわかる。このことから、電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値がほぼ一定であることが実証できたと言える。
【００５４】
図１４は、本発明の無線機の空中線電力の推定値の具体的な算出原理を示す図である。反射箱５内で、図１４（Ａ）に示すように、送信アンテナ５１のアンテナ端電力をＰ₁ としたときの受信アンテナ５２端での電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値をＰ₂ とする。また、図１４（Ｂ）に示すように、送信アンテナ５１の代わりに空中線電力Ｐ_x の無線機５８を入れたときの受信アンテナ５２端での電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値をＰ₃ とする。上記実証された原理より電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値がρに関わらず一定となるので、次式が成り立つ。
【００５５】
Ｐ_x ／Ｐ₁ ＝Ｐ₃ ／Ｐ₂ （８）
したがって、
Ｐ_x ＝Ｐ₃ （Ｐ₁ ／Ｐ₂ ） （９）
ここで、Ｐ₁ ／Ｐ₂ を反射箱損Ｌ_C と定義すると、
Ｐ_x ＝Ｐ₃ Ｌ_C （１０）
となり、無線機５８の電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値を測定し、この測定値と、予め求めておいた周波数毎の反射箱損Ｌ_C とに基づいて、空中線電力Ｐ_x を推定することができる。
【００５６】
図１５は、本発明の実施の形態における無線機空中線電力推定処理フローを示す図である。まず、反射箱５内で無線機から電波を発信する（ステップＳ１）。具体的には、図１６に示す測定系統における反射箱５内において、無線機５８から電波を発信する。なお、図１６に示す測定系統においては、例えば、反射箱５内の攪拌翼Ｂ５４の回転速度を１２０ｒｐｍ、攪拌翼Ｄ５６の回転速度を１１７ｒｐｍ、攪拌翼Ａ５３、攪拌翼Ｃ５５の回転速度を０ｒｐｍとし、１０秒を測定時間とする設定で解析を行う。
【００５７】
次に、反射箱５内で無線機５８から発信された電波を受信する（ステップＳ２）。具体的には、無線機５８から発信された電波を受信アンテナ５２において受信する。
【００５８】
そして、受信した電波に基づいて電界強度累積分布関数を算出する（ステップＳ３）。具体的には、受信アンテナ５２が受信した電波レベルをスペクトルアナライザ８が受信し、統計量測定装置６がスペクトルアナライザ８のビデオ出力信号をＡ／Ｄ変換し、電界強度累積分布関数（ＣＤＦ）を算出する。本発明の実施の形態においては、例えば、図１７に示すような電界強度累積分布関数（ＣＤＦ）が算出される。
【００５９】
次に、算出された電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値と予め算出された反射箱損の値とに基づいて無線機の空中線電力の推定値を算出する（ステップＳ４）。具体的には、ステップＳ３で算出された電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値Ｐ₃ を求め、予め算出された反射箱損Ｌ_C と上記式（１０）を用いて、無線機５８の空中線電力Ｐ_x を算出する。まず、ステップＳ３で算出された電界強度累積分布関数の累積確率６３．２％値Ｐ₃ は、図１７より、−４３．７ｄＢｍである。
【００６０】
また、反射箱損Ｌ_C は、予め以下の通り算出しておく。すなわち、図１１に示す測定系統において、反射箱５内の送信アンテナ５１から発信された電波を受信アンテナ５２において受信し、受信電波レベルをスペクトルアナライザ８で受信した後、統計量測定装置６がスペクトルアナライザのビデオ出力信号をＡ／Ｄ変換して、下記の図１８（Ａ）に示す電界強度累積分布関数を算出し、算出された電界強度累積分布関数に基づいて、反射箱５の反射箱損Ｌ_C を求める。
【００６１】
図１８（Ａ），図１８（Ｂ）は、それぞれ図１３（Ａ）、図１３（Ｂ）の横軸を規格化せず、図８のスペアナ指示値対ＡＤＣコード値をもとにデシベル表示したものである。受信アンテナ５２端での電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値Ｐ₂ は図１８（Ａ）より−２１．４ｄＢｍであり、また、送信アンテナ５１の入力端電力は−５．１ｄＢｍである。
【００６２】
従って、測定に用いた反射箱５の反射箱損Ｌ_C は１６．３ｄＢ（ただし、攪拌翼Ｂの回転速度１２０ｒｐｍ、攪拌翼Ｄの回転速度１１７ｒｐｍ，攪拌翼Ａ、攪拌翼Ｃの回転速度０ｒｐｍ，攪拌翼位置は壁面の中心、周波数１ＧＨＺの場合）と求まる。
【００６３】
よって、無線機５８の空中線電力Ｐ_x は、式（１０）より、Ｐ_x ＝−４３．７ｄＢｍ＋１６．３ｄＢｍ＝−２７．４ｄＢｍと推定される。
【００６４】
上記無線機５８のアンテナ入力端でのＳＧ出力は、実際には−２５．３ｄＢｍであり、上記空中線電力の推定値−２７．４ｄＢｍとは、上述の設定では２．１ｄＢの差が生じた。
【００６５】
なお、反射箱内で無線機５８を置く位置によりＣＤＦ６３．２％値がどの程度変動するのか図１９に示す反射箱１０を用いて検討を行った。５９は反射箱１０のドアである。図２０に無線機５８を＋ｙ１７５ｃｍから−ｙ１２５ｃｍまで移動させたときの統計量測定装置６で測定したＥ_x 、Ｅ_y およびＥ_z を示す。なお、Ｅ_x 、Ｅ_y およびＥ_z は、受信アンテナ５２がそれぞれＸ方向、Ｙ方向およびＺ方向の場合の電界強度累積分布関数（ＣＤＦ）の累積確率６３．２％値を示す。また、図２０における実線はＥ_x 、Ｅ_y およびＥ_z の平均値を示す。
【００６６】
その結果、今回測定したｙの範囲において、Ｅ_x 、Ｅ_y およびＥ_z は最大で４ｄＢ近い変動があるが、Ｅ_x 、Ｅ_y およびＥ_z の平均値に対して変動幅は最大で約１．５ｄＢあった。
【００６７】
反射箱損を測定するときにも同様の変動を与えるため、送信アンテナの位置、向き、放射パターンによる反射箱損の変動は空中線電力推定の主要な誤差要因となり得ることから、攪拌翼の回転周期を長くするなどして、反射箱内にランダムな電磁界を作る必要がある。
【００６８】
【発明の効果】
本発明は、反射箱内での電界強度時間変動分布の統計量に基づいて空中線電力を推定する。従って、本発明によれば、煩雑な操作を必要とせずに、送受信アンテナの向きにかかわらず、しかも安価に無線機の空中線電力を推定できる方法を提供することが可能となる。
【図面の簡単な説明】
【図１】本発明の無線機空中線電力推定方法の概要を示す図である。
【図２】電界強度累積分布関数を示す図である。
【図３】反射箱の諸元を示す図である。
【図４】統計量測定装置の諸元を示す図である。
【図５】確率密度関数（ＰＤＦ）を示す図である。
【図６】自己相関時間算出のための測定系統図である。
【図７】デジタルオシロスコープの時系列データを示す図である。
【図８】ＡＤＣコードに対応するスペアナ指示値を示す図である。
【図９】直接波の測定系統を示す図である。
【図１０】マルチパス波の測定系統を示す図である。
【図１１】合成波の測定系統を示す図である。
【図１２】直接波、マルチパス波及び合成波の測定結果（ＣＤＦ）を示す図である。
【図１３】直接波およびＸ，Ｙ，およびＺで平均したマルチパス波と合成波のＣＤＦ、ＰＤＦを示す図である。
【図１４】無線機の空中線電力の推定値の具体的な算出原理を示す図である。
【図１５】本発明の実施の形態における無線機空中線電力推定処理フローを示す図である。
【図１６】本発明の実施の形態における測定系統図である。
【図１７】電界強度累積分布関数（ＣＤＦ）を示す図である。
【図１８】ＣＤＦまたはＰＤＦを示す図である。
【図１９】反射箱内で無線機を置く位置を変化させる場合の測定系統図である。
【図２０】無線機の位置を変化させた場合のＣＤＦ６３．２％値を示す図である。
【符号の説明】
１ 無線機電波発信ステップ
２ 無線機電波受信ステップ
３ 電界強度累積分布関数算出ステップ
４ 空中線電力推定ステップ
５、１０、１２、１３ 反射箱
６ 統計量測定装置
７ 信号発生器
８ スペクトルアナライザ
９ デジタルオシロスコープ
１１ 電波暗箱
５１、１００ 送信アンテナ
５２、１０１ 受信アンテナ
５３ 攪拌翼Ａ
５４ 攪拌翼Ｂ
５５ 攪拌翼Ｃ
５６ 攪拌翼Ｄ
５７ 金属フェンス
５８ 無線機
５９ ドア[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna power estimation technique, and more particularly, to an antenna power estimation method for a radio based on statistics of electric field strength time variation distribution in a reflection box.
[0002]
[Prior art]
With the development of electronics, wireless facilities are becoming smaller and lighter, and for example, devices that cannot be detached from antennas have been developed. As a conventional method for measuring the antenna power of a radio device, for example, measurement by the antenna replacement method in a six-surface non-reflective room or a test site where reflected waves are suppressed (1996, Telecommunication Technology Council report, “Antenna integrated type” "Technical conditions for measuring the radio power of radio equipment").
[0003]
There is also a method for estimating the antenna power of the radio based on the direct wave received from the radio using an anechoic box (see, for example, Non-Patent Document 1). There is also a method for adjusting the direction of the receiving antenna in the reflection box, receiving only the reflected wave from the radio, and estimating the antenna power of the radio by taking the average of the power of the received reflected wave.
[0004]
[Non-Patent Document 1]
Yoshiyuki Hamada, Yoshiyuki Miyazawa, Isao Sugiyama, Masayasu Tanaka, Yuki Shimizu, “Examination of test method for radio with integrated antenna,” 2001 Shingaku Sodai, B-4-28, Mar. 2001.
[0005]
[Problems to be solved by the invention]
However, among the above prior arts, the method of estimating the antenna power using a radio wave non-reflective room and an anechoic box has a problem that it is expensive. Moreover, the method of estimating the antenna power using only the reflected wave requires a complicated operation of adjusting the direction of the receiving antenna.
[0006]
An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a method capable of estimating the antenna power of a radio at a low cost regardless of the direction of a transmission / reception antenna without requiring a complicated operation. To do.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention estimates the antenna power of the radio based on the statistics of the electric field strength time variation distribution in the reflection box.
[0008]
That is, the present invention is an antenna power estimation method for a radio, the step of transmitting radio waves from the radio in a reflection box, the step of receiving radio waves transmitted from the radio in the reflection box, Calculating an electric field strength cumulative distribution function in the reflection box based on the received radio wave; calculating an estimated value of the antenna power of the radio based on the calculated electric field strength cumulative distribution function; It is characterized by having.
[0009]
Further, the present invention is an antenna power estimation method of a radio, the step of transmitting radio waves from a radio in a reflection box, the step of receiving radio waves transmitted from the radio in the reflection box, A step of calculating a field distribution cumulative distribution function in the reflection box based on the received radio wave, a cumulative probability 63.2% value of the field distribution cumulative distribution function calculated in advance, and a value of the reflection box loss calculated in advance And calculating an estimated value of the antenna power of the radio based on the above.
[0010]
By using the present invention, it is possible to estimate the antenna power of the radio device at low cost by using both the direct wave and the reflected wave transmitted from the radio device without requiring a complicated operation.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of a radio antenna power estimation method according to the present invention. In FIG. 1, 1 is a radio wave transmission step, 2 is a radio wave reception step, 3 is an electric field strength cumulative distribution function calculation step, and 4 is an antenna power estimation step. Reference numeral 5 is a reflection box, and 6 is a statistic measuring device. Here, the reflection box 5 is a device that fluctuates the medium temporally with the rotating blades in the box, and the statistic measurement device 6 is a measurement device that measures the statistic of the changing radio signal.
[0012]
In radio wave transmission step 1, radio waves are transmitted from the radio in the reflection box 5. In the radio wave reception step 2, the radio wave transmitted from the radio is received by the receiving antenna in the reflection box 5. In the electric field strength cumulative distribution function calculation step 3, the statistic of the radio signal received by the radio device is measured using the statistic measuring device 6, and the electric field strength cumulative distribution function in the reflection box 5 is calculated. Further, in the antenna power estimation step 4, the antenna power of the radio is estimated based on the calculated electric field strength cumulative distribution function.
[0013]
First, the principle of the present invention will be described. FIG. 2 is a diagram illustrating the electric field strength cumulative distribution function. When a sensor that detects a wave source and an electromagnetic field generated by the wave source exists in the reflection box 5, a large number of reflected waves reach the sensor from the wave source in addition to the direct wave. The sensor receives these combined waves. If the wave source, the sensor, and the medium are all stationary, the envelope level of the synthesized wave detected by the sensor becomes constant, but the value varies greatly depending on the position of the wave source and the sensor.
[0014]
If the wave source / sensor moves or the medium changes, the envelope level changes, and the reception level can be regarded as a kind of random variable. A rotating blade is provided in the reflection box 5 to change the medium temporally.
[0015]
When the reception antenna output voltage of the composite wave is v (t) and the probability density function (PDF) of the envelope r (t) is p (r), a large number of reflected waves are regarded as multipath waves. Then, the probability that the envelope r enters the interval [r, r + dr] is r ≧ 0,
[0016]
[Expression 1]

[0017]
Given in.
[0018]
Here, sigma ² is the multipath wave power, A ^2/2 direct wave power, I ₀ is the zero-order (0th-order) modified Bessel function. Equation (1) includes two parameters A and σ. Here, a new parameter ρ (ratio between direct wave power and multipath wave power)
[0019]
[Expression 2]

[0020]
And the envelope r is normalized by the square root of the power sum of the direct wave and the multipath wave,
[0021]
[Equation 3]

[0022]
However,
[0023]
[Expression 4]

[0024]
It is expressed. Here, the coefficient 1 / √2 of the numerator is attached so that the square average of the envelope is 1.
[0025]
The mean square of the envelope is
E [r ² (t)] = A ² + 2σ ² (5)
Given in. Therefore,
[0026]
[Equation 5]

[0027]
It becomes.
[0028]
By integrating equation (3) with R, for example, a cumulative distribution function F (R) (CDF: Cumulative distribution function) shown in FIG. 2 is calculated. This cumulative distribution function F (R) (CDF) is the electric field strength cumulative distribution function in the present invention.
[0029]
When U is a unit step function (step function), F (R) = U (R-1) when ρ → ∞, and Rayleigh distribution when ρ = 0, so F (R) = 1. −exp (−R ² ). Therefore, the two intersect at the cumulative probability 1−e ⁻¹ = 0.632. For ρ between the two, the crossing point is off, but at a cumulative probability of 0.632, the deviation is at most 0.5 dB (see FIG. 2). That is, the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) is a substantially constant value regardless of ρ. This means that if the inside of the reflection box is normalized by the square root of the power sum, whether it is Rayleigh distribution or Rice distribution, it becomes a constant value.
[0030]
In the present invention, the radio antenna power is estimated using the fact that the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) is substantially constant. A specific estimation method will be described later.
[0031]
Next, it is specifically verified that the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) is substantially constant. FIG. 3 is a diagram showing specifications of the reflection box used for measurement in the embodiment of the present invention.
[0032]
The size of the reflection box 5 is 5.5 m × 4.5 m × 3 m. The size of the stirring blade (stirrer) in the reflection box 5 is 2 m x 0.7 m, the installation location is 70 cm away from the ceiling, front, right and left walls, and the maximum rotation speed is 120 rpm. Can be rotated separately. The shield characteristic is 100 dB or more for 150 MHz-10 GHz and 90 dB or more for 18 GHz.
[0033]
FIG. 4 is a diagram showing specifications of the statistic measurement device 6 used for measurement in the embodiment of the present invention. The statistic measurement device 6 is a device that A / D converts the video output signal of the spectrum analyzer (sparener) and measures various statistics in a specified time interval in real time.
[0034]
The unit of observation time of the statistic measuring device 6 is about 1 second, the missing time is about 10 milliseconds, the sampling speed is 20 Msample / second (50 ns), and the amplitude resolution is 256 steps. As the statistic measuring device 6, for example, an APD measuring device or the like can be used.
[0035]
In addition, measurable data include probability density distribution (PDF), amplitude probability distribution (corresponding to 1-CDF) (APD: Amplitude probability distribution), crossing rate distribution (CRD), pulse width distribution. (PDD: Pulse duration distribution), pulse interval distribution (PSD: Pulse separation distribution).
[0036]
Here, in the reflection box 5, the radio wave transmitted from the wireless device is reflected by the wall or the stirring blade, so that a signal whose amplitude varies randomly is received by the receiving antenna. However, this random signal has periodicity because it depends on the arrangement of the stirring blades. Therefore, appropriate data processing can be performed by acquiring data for a time corresponding to the cycle. Therefore, the autocorrelation function of the received signal was obtained in order to obtain an appropriate data acquisition time.
[0037]
The shaded portions in FIG. 5 are measured values (PDF) obtained by the statistic measuring device 6 when the rotation speed is set to 120 rpm and the stirring blade D: 117 rpm in the reflection box 5 shown in FIG. , Measurement time 1 second). Since each measurement data (300 lines, shaded portion) in 5 minutes is less than the period of the random signal, the variation is large, and it can be understood that appropriate data processing is impossible as it is.
[0038]
The period t of the received random signal depending on the arrangement state of the stirring blades is set so that the rotation speeds of the first stirring blade and the second stirring blade are f ₁ and f _2, and N ₁ and N ₂ are integers.
t = (N ₁ −N ₂ ) / 2 (f ₁ −f ₂ ) (7)
It is obtained by For example, the period of the random signal when the rotation speed of the first stirring blade is 120 rpm and the rotation speed of the second stirring blade is 117 rpm is calculated as t = 10 seconds from Equation (7). Hereinafter, the calculation result is verified using the measurement system of FIG.
[0039]
In FIG. 6, 7 is a signal generator for generating radio signals, 8 is a spectrum analyzer, 9 is a digital oscilloscope for measuring the video output of the spectrum analyzer, 51 is a transmission antenna for transmitting radio waves, 12 is a reflection box, and 52 is radio waves. , 53 is a stirring blade A, 54 is a stirring blade B, 55 is a stirring blade C, and 56 is a stirring blade D.
[0040]
An output of 1 GHz and 0 dB is applied from the signal generator 7 to the transmission antenna 51, and the reception level of the reception antenna 52 is received by the spectrum analyzer 8. The spectrum analyzer 8 is set to zero span, and the video output of the spectrum analyzer 8 is measured with a digital oscilloscope 9 (20 ksample / sec). When the autocorrelation time is obtained from the time-series data of the digital oscilloscope 9, as shown in FIG. 7, the autocorrelation is taken every 10 seconds as in the calculation result of the period of the random signal using the equation (7). Understand.
[0041]
Here, the rotation speed of the stirring blade B54 in the reflection box 5 of FIG. 11 described later is 120 rpm, the rotation speed of the stirring blade D56 is 117 rpm, the rotation speed of the stirring blade A53 and the stirring blade C55 is set to 0 rpm, and 10 seconds. The result of PDF measurement for 5 minutes when the measurement time is taken is shown by the solid line (black line portion) in FIG. Although this data corresponds to 30 lines, they are almost overlapped, and it seems that data processing appropriate for obtaining statistics can be performed.
[0042]
From the above autocorrelation analysis results, in the embodiment of the present invention, data is used in which the rotation speeds of the stirring blades B54 and D56 in the reflection box are 120 rpm and 117 rpm, respectively, and the unit measurement time is 10 seconds. Analysis.
[0043]
Further, the statistic measurement device 6 used in the embodiment of the present invention A / D converts the signal intensity and obtains a probability distribution corresponding to the ADC code. FIG. 8 shows a spectrum indicator value corresponding to the ADC code. From this figure, it can be seen that the ADC code and the spectrum indicator value correspond to each other with good linearity.
[0044]
When the transmitting antenna and the receiving antenna are opposed to each other in the reflection box, the radio wave radiated from the transmitting antenna is not only the direct wave but also the multipath wave (multipath wave) reflected by the stirring blade or the wall at the receiving antenna. The synthesized wave is received. Therefore, in order to verify that the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) is substantially constant, the following measurement was performed.
[0045]
In order to measure only the direct wave among the received synthetic waves, the measurement was performed in a six-sided anechoic box according to the measurement system diagram of FIG.
[0046]
In FIG. 9, 11 is an anechoic box, 100 is a transmitting antenna, and 101 is a receiving antenna. A radio wave is transmitted from the transmitting antenna 100 to the receiving antenna 101 based on the radio wave signal generated by the signal generator 7, the radio wave level received at the receiving antenna 101 is received by the spectrum analyzer 8, and the output of the spectrum analyzer 8 is a statistic. Measure with the measuring device 6. In this case, since there is no multipath wave and only a direct wave, ρ is close to ∞ and there is no fluctuation in the envelope level.
[0047]
Next, in order to measure only multipath waves, a metal fence was installed in the reflection box between the transmitting and receiving antennas, and the stirring blades were rotated to perform measurement according to the measurement system diagram shown in FIG.
[0048]
In FIG. 10, 13 is a reflection box, and 57 is a metal fence. Since the reception antenna 52 receives radio waves reflected from walls and stirring blades from various angles, the direction of the reception antenna 52 is changed to X (Horizontal 0 deg), Y (Horizontal 90 deg), and Z (Vertical 0 deg). Each case was measured. In this case, since there is no direct wave, ρ is close to zero.
[0049]
Further, in order to receive the composite wave of the direct wave and the multipath wave, the metal fence 57 in the measurement system diagram of FIG. 10 is removed, and the stirring blade in the reflection box 5 is rotated by the measurement system shown in FIG. It was. Originally, the direct wave should be received only when the receiving antenna 52 is in the X direction, but the measurement was performed by changing the direction of the receiving antenna 52 to X, Y, and Z as in the case of multipath wave measurement. The power ratio ρ of the direct wave and the multipath wave is unknown, but according to theory, the cumulative probability 63.2% value should not depend on ρ.
[0050]
12A shows the measurement result (CDF) of the direct wave measured by the measurement system of FIG. 9, FIG. 12B shows the measurement result (CDF) of the multipath wave measured by the measurement system of FIG. C) is a measurement result (CDF) of the synthetic wave measured by the measurement system of FIG. The horizontal axis is R normalized by the square root of the power sum.
[0051]
In the direct wave shown in FIG. 12A, the receiving antenna 101 is in the X direction. In the multipath wave shown in FIG. 12B, the measurement results when the direction of the receiving antenna 52 is in the X, Y, and Z directions are overlapped. This indicates that the multipath wave is a uniform signal even if the direction of the receiving antenna 52 is changed.
[0052]
The synthesized wave shown in FIG. 12C has a level fluctuation when the direction of the receiving antenna 52 is changed. Therefore, it is considered that signals received in all directions of the receiving antenna 52 are received by averaging the signals received by changing the direction of the receiving antenna 52 to X, Y, and Z, and FIG. Waveform CDF and receiving antenna 52 are multipath waves and synthetic CDFs obtained by averaging measurement results in the X, Y, and Z directions. FIG. 13B shows direct wave PDF and receiving antenna 52 orientations. Shows the PDF of the multipath wave and the synthesized wave obtained by averaging the measurement results in the X direction, Y direction, and Z direction.
[0053]
According to FIG. 13A, the direct wave, the multipath wave, and the combined wave intersect at the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF), and the cumulative probability 63.2% as in the principle. It can be seen that the value does not depend on the ratio ρ of the direct wave power and the multipath wave power. From this, it can be said that it was proved that the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) is almost constant.
[0054]
FIG. 14 is a diagram illustrating a specific calculation principle of the estimated value of the antenna power of the wireless device of the present invention. In the reflection box 5, as shown in FIG. 14 (A), the cumulative probability 63.2 field intensity cumulative distribution function of the receiving antenna 52 ends when the antenna end power of the transmitting antenna 51 and the P ₁ (CDF) the percentage value is set to P _2. Further, FIG. 14 (B), the cumulative probability 63 of the field intensity cumulative distribution function of the receiving antenna 52 edge when inserting the radio 58 of the antenna power P _x instead of transmitting antennas 51 (CDF). 2% value is P _3. Since the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) is constant regardless of ρ according to the proven principle, the following equation holds.
[0055]
P _x / P ₁ = P ₃ / P ₂ (8)
Therefore,
P _x = P ₃ (P ₁ / P ₂ ) (9)
Here, if P ₁ / P ₂ is defined as a reflection box loss L _C ,
P _x = P ₃ L _C (10)
Then, the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) of the radio 58 is measured, and the antenna is calculated based on the measured value and the reflection box loss L _{C for} each frequency obtained in advance. The power P _x can be estimated.
[0056]
FIG. 15 is a diagram showing a radio antenna power estimation process flow in the embodiment of the present invention. First, radio waves are transmitted from the wireless device in the reflection box 5 (step S1). Specifically, radio waves are transmitted from the radio 58 in the reflection box 5 in the measurement system shown in FIG. In the measurement system shown in FIG. 16, for example, the rotation speed of the stirring blade B54 in the reflection box 5 is 120 rpm, the rotation speed of the stirring blade D56 is 117 rpm, the rotation speed of the stirring blade A53 and the stirring blade C55 is 0 rpm, Analysis is performed with a setting of 10 seconds as the measurement time.
[0057]
Next, the radio wave transmitted from the wireless device 58 is received in the reflection box 5 (step S2). Specifically, the reception antenna 52 receives the radio wave transmitted from the wireless device 58.
[0058]
Then, an electric field strength cumulative distribution function is calculated based on the received radio wave (step S3). Specifically, the spectrum analyzer 8 receives the radio wave level received by the receiving antenna 52, the statistic measurement device 6 performs A / D conversion on the video output signal of the spectrum analyzer 8, and the electric field strength cumulative distribution function (CDF) is obtained. calculate. In the embodiment of the present invention, for example, a field strength cumulative distribution function (CDF) as shown in FIG. 17 is calculated.
[0059]
Next, an estimated value of the antenna power of the radio is calculated based on the cumulative probability 63.2% value of the calculated electric field strength cumulative distribution function (CDF) and the value of the reflection box loss calculated in advance (step S4). ). Specifically, a cumulative probability 63.2% value P ₃ of the electric field strength cumulative distribution function (CDF) calculated in step S3 is obtained, and the reflection box loss L _C calculated in advance and the above equation (10) are used. Then, the antenna power P _x of the radio 58 is calculated. First, the cumulative probability 63.2% value P ₃ of the electric field strength cumulative distribution function calculated in step S3 is −43.7 dBm from FIG.
[0060]
The reflection box loss L _C is calculated in advance as follows. That is, in the measurement system shown in FIG. 11, after the radio wave transmitted from the transmission antenna 51 in the reflection box 5 is received by the reception antenna 52 and the received radio wave level is received by the spectrum analyzer 8, the statistic measurement device 6 performs the spectrum measurement. The video output signal of the analyzer is A / D converted to calculate the electric field intensity cumulative distribution function shown in FIG. 18A below, and based on the calculated electric field intensity cumulative distribution function, the reflection box loss of the reflection box 5 is calculated. Find L _C.
[0061]
18 (A) and 18 (B) are displayed in decibels based on the spectrum indicator indicated value vs. ADC code value in FIG. 8 without normalizing the horizontal axis in FIG. 13 (A) and FIG. 13 (B), respectively. It is a thing. The cumulative probability 63.2% value P ₂ of the electric field strength cumulative distribution function (CDF) at the receiving antenna 52 end is −21.4 dBm from FIG. 18A, and the input end power of the transmitting antenna 51 is −5. .1 dBm.
[0062]
Therefore, the reflection box loss L _C of the reflection box 5 used for the measurement is 16.3 dB (however, the rotation speed of the stirring blade B is 120 rpm, the rotation speed of the stirring blade D is 117 rpm, the rotation speed of the stirring blade A and the stirring blade C is 0 rpm, The stirring blade position is obtained as the center of the wall surface and the frequency is 1 GHz.
[0063]
Therefore, the antenna power P _x of the radio device 58 is estimated as P _x = −43.7 dBm + 16.3 dBm = −27.4 dBm from the equation (10).
[0064]
The SG output at the antenna input terminal of the wireless device 58 is actually −25.3 dBm, and a difference of 2.1 dB is generated in the above setting from the antenna power estimated value −27.4 dBm.
[0065]
It was examined using the reflection box 10 shown in FIG. 19 how much the CDF 63.2% value varies depending on the position where the radio 58 is placed in the reflection box. Reference numeral 59 denotes a door of the reflection box 10. FIG. 20 shows E _x , E _y, and E _z measured by the statistic measurement device 6 when the wireless device 58 is moved from + y 175 cm to −y 125 cm. E _x , E _y, and E _z represent the cumulative probability 63.2% value of the electric field strength cumulative distribution function (CDF) when the receiving antenna 52 is in the X direction, the Y direction, and the Z direction, respectively. The solid line in FIG. 20 shows the average value of E _x, E _y and E _z.
[0066]
As a result, in the range of y measured this time, E _x , E _y, and E _z vary up to 4 dB at maximum, but the fluctuation range is about 1 at maximum with respect to the average value of E _x , E _y, and E _z. .5 dB.
[0067]
Since the same fluctuation is given when measuring the reflection box loss, the fluctuation of the reflection box loss due to the position, orientation, and radiation pattern of the transmitting antenna can be a major error factor in the antenna power estimation. It is necessary to create a random electromagnetic field in the reflection box, for example, by lengthening.
[0068]
【The invention's effect】
The present invention estimates the antenna power based on the statistic of the electric field strength time variation distribution in the reflection box. Therefore, according to the present invention, it is possible to provide a method capable of estimating the antenna power of a radio device at a low cost regardless of the direction of the transmission / reception antenna without requiring a complicated operation.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a radio antenna power estimation method according to the present invention.
FIG. 2 is a diagram showing an electric field strength cumulative distribution function.
FIG. 3 is a diagram showing specifications of a reflection box.
FIG. 4 is a diagram showing specifications of a statistic measuring apparatus.
FIG. 5 is a diagram showing a probability density function (PDF).
FIG. 6 is a measurement system diagram for calculating autocorrelation time.
FIG. 7 is a diagram showing time-series data of a digital oscilloscope.
FIG. 8 is a diagram illustrating a spectrum indicator value corresponding to an ADC code.
FIG. 9 is a diagram showing a direct wave measurement system;
FIG. 10 is a diagram showing a measurement system for multipath waves.
FIG. 11 is a diagram showing a synthetic wave measurement system;
FIG. 12 is a diagram showing measurement results (CDF) of a direct wave, a multipath wave, and a synthesized wave.
FIG. 13 is a diagram showing CDF and PDF of a direct wave, a multipath wave averaged by X, Y, and Z, and a synthesized wave.
FIG. 14 is a diagram showing a specific calculation principle of an estimated value of antenna power of a radio device.
FIG. 15 is a diagram showing a radio antenna power estimation process flow in the embodiment of the present invention;
FIG. 16 is a measurement system diagram according to the embodiment of the present invention.
FIG. 17 is a diagram showing an electric field strength cumulative distribution function (CDF).
FIG. 18 is a diagram showing a CDF or a PDF.
FIG. 19 is a measurement system diagram in the case where the position where the wireless device is placed in the reflection box is changed.
FIG. 20 is a diagram illustrating a CDF 63.2% value when the position of the wireless device is changed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Radio wave transmission step 2 Radio wave reception step 3 Electric field strength cumulative distribution function calculation step 4 Antenna power estimation step 5, 10, 12, 13 Reflection box 6 Statistics measuring device 7 Signal generator 8 Spectrum analyzer 9 Digital oscilloscope 11 Anechoic box 51, 100 Transmitting antenna 52, 101 Receiving antenna 53 Mixing blade A
54 Stirring blade B
55 Stirring blade C
56 Stirring blade D
57 Metal fence 58 Radio 59 Door

Claims (2)

A radio antenna power estimation method,
Sending radio waves from the radio in the reflection box;
Receiving radio waves transmitted from the radio in the reflection box;
Calculating a field strength cumulative distribution function in the reflection box based on the received radio wave;
A method of estimating an antenna power of a radio, comprising: calculating an estimated value of the antenna power of the radio based on the calculated electric field strength cumulative distribution function. A radio antenna power estimation method,
Sending radio waves from the radio in the reflection box;
Receiving radio waves transmitted from the radio in the reflection box;
Calculating a field strength cumulative distribution function in the reflection box based on the received radio wave;
Calculating an estimated value of the antenna power of the radio based on a cumulative probability value of 63.2% of the calculated electric field strength cumulative distribution function and a value of a reflection box loss calculated in advance. An antenna power estimation method for a radio.

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