Spatial polarimetric time-frequency distributions and applications to direction-of-arrival estimation

Abstract—Time-frequency distributions (TFDs) are tradition-ally applied to a single antenna receiver with a single polarization. Recently, spatial time-frequency distributions (STFDs) have been developed for receivers with multiple single-polarized antennas and successfully applied for direction-of-arrival (DOA) estimation of nonstationary signals. In this paper, we consider dual-polar-ized antenna arrays and extend the STFD to utilize the source polarization properties. The spatial polarimetric time-frequency distributions (SPTFDs) are introduced as a platform for pro-cessing polarized nonstationary signals, which are received by an array of dual-polarized double-feed antennas. This paper deals with narrow-band far-field point sources that lie in the plane of the receiver array. The source signals are decomposed into two orthogonal polarization components, such as vertical and hori-zontal. The ability to incorporate signal polarization empowers the STFDs with an additional degree of freedom, leading to im-proved signal and noise subspace estimates for direction finding. The polarimetric time-frequency MUSIC (PTF-MUSIC) method for DOA estimation based on the SPTFD platform is developed and shown to outperform the time-frequency, polarimetric, and conventional MUSIC techniques, when applied separately. Index Terms—Array signal processing, direction-of-arrival (DOA) estimation, MUSIC, polarization, smart antennas, time-fre-quency distributions (TFDs). I