High-frequency electromagnetic wave propagation phenomena associated
with borehole georadar experiments are complex. To improve our understanding
of the governing physical processes, we present a suitable finitedifference
time-domain (FDTD) solution of Maxwell's equations in cylindrical
coordinates. An important feature of this algorithm is the use of
a powerful grid refinement technique that enables us to account efficiently
for detailed design aspects of georadar antennas as well as materials
with very high dielectric permittivities. This type of modeling provides
the basis for improving the ray-based inversion of the first-cycle
amplitudes and/or for performing the full-waveform inversion of crosshole
georadar data. We first validate the accuracy of the algorithm with
respect to the solutions for an infinitesimal electric dipole source
as well as a wire-type dipole antenna and then apply it to explore
the radiative properties of realistic antenna designs used in borehole
georadar.