Incremental length diffraction coefficients for arbitrary cylindrical scatterers

Convenient expressions are derived for incremental length diffraction coeff icients (ILDCs) in terms of the far fields of arbitrary cylindrical canonic al scatterers composed of linear electromagnetic material. The derivation o f these general expressions for ILDCs is based on a surface-current equival ence theorem that states that the electromagnetic fields outside cylindrica l sources can be generated to any degree of accuracy by localized electric and magnetic surface currents that lie in a single plane within the source region. This equivalence theorem is proven with the help of cylindrical wav e expansions and the Kottler-Franz formulas. It combines with a general eve n and odd decomposition of cylindrical electromagnetic fields to allow the use of previous formulas for planar surface-current ILDCs in the derivation of the general expressions for ILDCs in terms of cylindrical far fields.