Publication: IEICE TRANSACTIONS on Communications Publication Date: 2019/02/01 Vol. E102-BNo. 2pp. 174-181 Type of Manuscript: INVITED PAPER (Special Section on Recent Progress in Antennas and Propagation in Conjunction with Main Topics of ISAP2017) Category: Antennas Keyword: metasurface antennas, leaky waves, artificial surfaces, Floquet waves, impedance boundary conditions,