On feeding slot susceptance of the electromagnetically coupled coaxial dipole antenna

The electromagnetically coupled coaxial dipole antenna (ECCDA) has an advantage of structural simplicity due to a novel use of an electromagnetically coupled feed for the radiating element. A simple expression for the self admittance of ECCDA is known, however, it still contains an infinite summation term for the susceptance of the feeding slot (see Miyashita, H. et al., IEEE Trans. Antennas Propagat., vol.47, no.11, p.1716-26, 1999). A simple approximately closed form expression of that term is obtained, and it is shown that the contribution is negligibly small for practical applications.