For small or medium size conformal array antennas in terms
of the wave length, modal solutions in spectral domain for
mutual coupling analysis are convenient for canonical shapes
such as circular cylinder [1] or sphere [2], but as the antenna dimensions increase a large number of terms are necessary.
For large structures the uniform theory of diffraction (UTD)
is commonly used to solve this problem for canonical and
arbitrarily convex shaped perfect electric conductor (PEC)
surfaces [3]. A UTD solution for mutual coupling on an
impedance cylinder has been introduced in [4], [5] but using
a constant surface impedance