2素子エスパアンテナの指向性可変性能の素子長・素子間隔依存性

摘要

In this paper, we investigate element spacing and length dependence of beam steering performance of of 2-element ESPAR antenna. And, we define ΔFBR (Front to Back Ratio), ΔEBR (End-fire to Broadside Ratio), ΔCBW (Cumulative Beam Width), ΔLLL (Locus Line Length), Ipod (Index of Pseudo-Orthogonal Directivity) and RDC (Reactance Domain Correlation) as beam steering performance indexes. In addition, we forcus on ratio of current distribution on each antenna elements and indicate a relation between it and beam steering performance indexes. As simulation result using an FDTD method and aerially distributed matrix immittance method, we obtain the optimum values of ΔEBR, ΔCBW, ΔLLL are obtained in the vicinity of element length 0.45λ. And, the optimal values of ΔFBR, Ipod, RDC are obtained in the vicinity of element length 0.6λ. Furthermore, ratio of current distribution on antenna elements in the case that reactance X = 0 Ω serves as a structural design guideline of an antenn of high beam steering performance useless to vary reactance.%本稿では，2素子エスパアンテナの指向性可変性能の素子間隔および給電素子長依存性を調べる.このため，指向性可変性能指標として，ΔFBR（Front to Back Ratio），ΔEBR（End-fire to Broadside Ratio），ΔCBW（Cumulative Beam Width），ΔLLL（Locus Line Length），Ipod（Index of Pseudo-Orthogonal Directivity），RDC （Reactance Domain Correlation）を定義する.さらに，各アンテナ素子に流れる電流分布の比と，指向性可変性能指標の関係を示す.FDTD法および空間分布イミタンス行列法によるシミュレーションの結果，給電素子長が0.45λ近傍において，ΔEBR，ΔCBW，ΔLLLは最適値となる.また，給電素子長0.6λ近傍において，ΔFBR，Ipod，RDCは最適値を得る.さらに，リアクタンスX＝0Ωに固定した電流分布の比は，高い指向性可変性能を有するアンテナ構造の設計指針となる.