On the computation of Infeld’s function used in evaluating the admittance of prolate spheroidal dipole antennas

The Infeld function expressed in terms of the outgoing prolate spheroidal radial wave function and its derivative, and employed in the expression of the input self-admittance of prolate spheroidal antennas, has accurately been calculated by using a newly developed asymptotic expression for large degree $n$. This asymptotic power series has been derived by using a perturbation method with a perturbation parameter $\epsilon = 1/\left ( {\lambda _{1n}} - {h^2} \right )$, where ${\lambda _{1n}}$ is the spheroid’s eigenvalue for the given parameter $h$ of the spheroidal wave function.