DOAMatrix法とSAGEアルゴリズムを併用した近傍波源位置推定のアレー素子間隔に関する改善

摘要

移動通信や室内無線通信において，周囲の状況や環境に応じて電波伝搬構造を詳細に把握するには，アレーアンテナを用いた到来彼の高分解能到来方向（DOA）推定が重要な技術となる.更に，近傍波源に対しては入射波が球面波となることから，遠方界到来方向推定とは異なる受信信号モデルが必要となる．本稿では，近傍波源からの距離減衰がアレー内で一定であると仮定した近傍界DOA-Matrix法に着目する．これはESPRITのような数値計算により直接推定値が得られる．しかし，この手法はアレーの素子間隔が波長の4分の1以下であることを要求するため，強い素子間相互結合が生じ推定精度の劣化が予想される．そこで，近傍界DOA-Matrix法を改良した新たなアルゴリズム，およびこれをSAGEアルゴリズムに導入した近傍界SAGE-DOA-Matrix法を提案し，素子間隔が波長の4分の1以上でも有効に動作することを計算機シミュレーションにより確認する．%It is important to understand the radio wave propagation structures in mobile or indoor wireless communications. One of useful methods for the purpose is high-resolution DOA estimation using array antenna. Furthermore, for the near field sources, different signal models are required since the incident wave fronts are spherical. This paper deals with the near field DOA-Matrix method for source localization, which assumes that the distance attenuation is constant in the array antenna. This method is an ESPRIT-like method and does not need peak search. However, this algorithm requires that array element spacing is equal to or less than a quarter of wavelength, and therefore it is supposed that strong mutual coupling among array elements causes serious degradation of estimation accuracy. To solve the problem, we propose an algorithm obtained by improving the near field DOA-Matrix method, and also propose near field SAGE-DOA-Matrix method which uses the improved method in SAGE algorithm. Via computer simulation, we show that the proposed methods provide successful estimation in the case of array element spacing larger than a quarter of wavelength.