Modeling antennas near to and penetrating a lossy interface

A technique for modeling wire objects interacting across or penetrating the planar interface which separates two half space is described. The moment-method treatment is employed, based on the thin wire approximation to the electric-field integral equation, with the effect of the interface included via the usual Sommerfeld integrals. The computation time associated with evaluating the latter is substantially shortened by using an interpolation based technique plus asymptotic field expressions. Although developed specifically for the wire problem, the procedure is also applicable, with slight modification, to modeling surface objects as well. Special account is taken of the charge discontinuity that occurs at the point a wire penetrates the interface. Example calculations are shown for the antenna-ground stake problem; monopole antenna driven against a simple ground screen; the fields of buried objects; and a simple EMP simulator.