External Admittance of an Axial Slot on a Dielectric Coated Metal Cylinder

An expression is derived for the external admittance of an axial slot cut in an infinitely long metal cylinder that is concentrically coated with a homogeneous dielectric of relative dielectric constant ∊r. The derivation is based on the mode expansion technique of Wait, in conjunction with Parseval's theorem. Determination of the axial surface waves that can be excited by this slot is also obtained. Additionally, azimuthal surface waves are discussed. Complete expressions in normalized form, ready to be computed, for the external conductance and susceptance of the slot are given for an ordinary dielectric coating (∊r ⩾), a plasma coating (0 ⩽ ∊r ⩽ 1), and no coating