PROPAGATION OF EM PULSES EXCITED BY AN ELECTRIC-DIPOLE IN A CONDUCTING MEDIUM

Exact solutions are given for the transient electromagnetic (EM) fields excited by an electric dipole antenna with an impulsive current in a conducting medium. There exists an optimum waveform for the antenna current which can generate an EM pulse with a maximum intensity at a particular distance from the antenna. It is found that the EM fields of an EM pulse excited by an antenna in a conducting medium can be divided into two parts. The first part is an impulse wave which propagates with the speed of light (1/square-root muepsilon) and decays exponentially. The second part builds up gradually and propagates slowly, and more importantly this part attenuates as an inverse power of distance which is a much slower rate than an exponential decay.