Two-Stage 3D Beam Training for Wideband THz MIMO with Frequency-Dependent Beamforming - Yu, Jiacheng; Ren, Jie; Xiao, Ying; Jiang, Ting; Xiao, Ailing (2025 IEEE Wireless Communications and Networking Conference (WCNC), Wireless Communications and Networking Conference (WCNC), 2025 IEEE, 2025)