An FDTD/MoMTD hybrid technique for modeling HF antennas located on lossy ground

For high frequency wave(2~30 MHz),calculating the current distribute and radiation pattern for antennas is a complex problem because of the interaction between the antenna, the ground, and any buried wire net. Typically, the finite-difference time-domain (FDTD) technique is well suited for modeling fields in heterogeneous media; the method of moments (MoM) is well suited for modeling complex antennas in free space. This paper introduces a hybrid technique, based upon the equivalence principle, and decomposes the problem of antennas located on ground into two coupled equivalent problems: one for the antenna geometry and the other for the ground geometry, with field information passing between them via a rapidly converging iterative procedure. The fields in each region may be modeled using numerical techniques best suited to them. Results for several test cases are presented, using FDTD to model the environment problem and MoM for the antenna problem, which demonstrates the accuracy of this hybrid technique.