Abstract-In this paper, the region of interest consists of the spherical dielectric earth, coated with a dielectric layer under the air. The simple explicit formulas have been derived for the electromagnetic fields of a vertical electric dipole and vertical magnetic dipole in the presence of three-layered spherical region, respectively. Next, basing on the above results, the formulas for the six components of the field in the air generated by a horizontal electric dipole are derived by using reciprocity. The computations show that the trapped surface wave of electric type can be excited efficiently and the trapped surface wave of magnetic type can not be excited when the thickness l of the dielectric layer is somewhat and satisfies the condition 0 < âˆš(k21-k20)*l < Ï€/2.When the thickness l of the dielectric layer is somewhat and satisfies the condition Ï€/2 < âˆš(k21-k20)*l < Ï€, the trapped surface wave of magnetic type can be excited. These formulas and the computations can be applied to the surface communications at the lower frequencies.
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