Surface currents and diffraction of whispering gallery modes by a spherical impedance cap

Surface currents induced by high-frequency whispering gallery waves on a spherically curved impedance sheet having different impedance faces are obtained. The influences of several diffraction phenomena on surface currents are given explicitly. The causes and forms of surface currents are described, and the scattered fields are determined from those currents. The results explain the contribution of surface currents to the scattered field in a quite simple form. When the impedance tends to zero the expressions reduce to those of the perfectly conducting sheet. The results are independent of the actual source configuration and applicable to more complicated scattering and inverse scattering phenomena.