Mutual admittance between slots on a cylinder using the extended Poynting vector method

The extended Poynting vector method is used to derive formulas for the mutual admittance between two identical slots on a perfectly conducting circular cylinder. Formulas for this geometry have earlier been derived via the reaction theorem. A disadvantage with those expressions is the poor convergence of the integral for large axial slot separations. Through extensive manipulations one formula can be converted into the other but for large axial slot separations the Poynting vector method gives converging expressions directly. It is thus proved that the extended Poynting vector method provides an alternative way of obtaining the mutual admittance between apertures on a cylinder.