  Terahertz (THz) band is currently envisioned as the key building block to
achieving the future sixth generation (6G) wireless systems. The ultra-wide
bandwidth and very narrow beamwidth of THz systems offer the next order of
magnitude in user densities and multi-functional behavior. However, wide
bandwidth results in a frequency-dependent beampattern causing the beams
generated at different subcarriers split and point to different directions.
Furthermore, mutual coupling degrades the system's performance. This paper
studies the compensation of both beam-split and mutual coupling for
direction-of-arrival (DoA) estimation by modeling the beam-split and mutual
coupling as an array imperfection. We propose a subspace-based approach using
multiple signal classification with CalibRated for bEAam-split and Mutual
coupling (CREAM-MUSIC) algorithm for this purpose. Via numerical simulations,
we show the proposed CREAM-MUSIC approach accurately estimates the DoAs in the
presence of beam-split and mutual coupling.
