Direction and polarization estimation with modified quad-quaternion music for vector sensor arrays

In this study, we describe the modified quad-quaternion MUSIC (QQ-MUSIC) for two-dimensional direction finding and signal polarization estimation with electromagnetic vector sensor arrays. Firstly, a detailed analysis of the regular QQ-Model, based on the framework of quad-quaternion, is presented to clarify the exact reason why the regular QQ-MUSIC cannot estimate polarization parameters. Subsequently, we construct the modified QQ-MUSIC to estimate directions of the incident signals, as well as their polarizations. Compared with the traditional methods, simulations on an `L-shaped' array are shown and discussed to illustrate the effectiveness of the proposed method.