An investigation into the simulation and performance of low-profile, electrically-small antennas for unattended ground sensor (UGS) networks is featured in this study. Because UGS transceivers are intended for operation near the ground, ground proximity effects become extremely important for considerations related to antenna efficiency, input matching, radiation pattern, and the overall path loss between the transmitter and receiver nodes. While vertical wire antennas are shown to be less susceptible to path loss, a low-profile alternative is desired for UGS applications and is often required in the fabrication of low-cost, monolithic on-chip, miniaturized systems. In this work, the performances of different transceiver systems utilizing different types of near-ground antenna structures including the dipole, loop, ordinary circular slot, and cavity-backed circular slot are analyzed using a full-wave hybrid approach consisting of the moment method in conjunction with a near-ground asymptotic field propagation model. The figure of merit for comparison among the various configurations is identified as the efficiency factor calculated from the ratio of the input power at the transmitting antenna terminal to the received power at the receiving antenna terminal. The unique features of ground proximity effects as pertaining to near-ground operation are discussed and an optimal radiator is identified from the set of structures analyzed.Index Terms-Ground proximity effects, hybrid full-wave analysis, low-profile antennas, near-earth radiowave propagation modeling and simulation, unattended ground sensor (UGS) networks.
