DB Boundary

This chapter discusses how boundary conditions involve normal field components. A class of electromagnetic boundaries not belonging to that of impedance boundaries can be defined in terms of normal field components of fields. While all resonance modes of the spherical DB‐resonator can be decomposed in two sets which coincide with the TE_r and TM_r modes of the respective PEC and PMC resonators, in the case of the circular waveguide, modes polarized TE_ρ and TM_ρ with respect to the radial direction ρ do not form a complete set. The basic reason for this lies in the fact that the general fields cannot be derived from the vector potential components F_ρ and A_ρ.