Numerical models that account for realistic transmitter and receiver
antenna behavior are necessary to develop waveform-based inversion
methods for crosshole ground-penetrating radar (GPR) data. A challenge
in developing such models is simulating the antennae in a computationally
efficient manner so that inversions can be performed in a reasonable
amount of time. We present an approach to efficiently simulate crosshole
GPR transmission and reception in heterogeneous media. The core of
our approach is a finite-difference time-domain (FDTD) solution of
Maxwell's equations in 2D cylindrical coordinates. First, we determine
the behavior of the Current oil a realistic GPR antenna in a borehole
through detailed FDTD modeling of the antenna and its immediate surroundings.
To model transmission and reception, we then replicate this antenna
Current behavior on a much-coarser grid using a superposition of
point-electric-dipole Source and receiver responses. Results obtained
with our technique agree with analytical results, with numerical
modeling results where the transmitter antenna and borehole are explicitly
accounted for using a fine discretization, and with crosshole GPR
field data.