Trapped surface wave and lateral wave on a conductor coated with a dielectric layer

The simple asymptotic analytical expressions of the electromagnetic fields induced by a vertical electric dipole on a planar or a spherical conductor coated with a dielectric layer have been obtained. These expressions show that the induced fields consist of the direct wave, reflected wave, lateral wave and trapped surface wave for the planar model, and consist of the trapped surface wave and diffractive wave for the spherical model. The propagation wave number of the trapped surface wave is between that of the wave number k/sub 0/ in the air and the wave number k/sub 1/ in the dielectric. The amplitude of the trapped surface wave attenuates as /spl rho//sup -1/2/ in the /spl rho/ direction near the surface and attenuates exponentially as e/sup -yz/ in the z direction. The expressions for the direct wave, reflected wave and lateral wave in this paper coincide with those in the paper by King and Sandler in the planar model. When the thickness of the dielectric layer is not small, the lateral wave and the trapped surface wave are combined the total field to produce an interference pattern in the planar model, but the trapped surface wave is dominant in the spherical model. And the comparison between both two models is given. The comparison show that the induced field in the spherical model is very different from that in the planar model.