Loop coupling and field distribution in earth for horizontal positioning in VLF/ELF through-the-earth wireless mine communications

A through-the-earth (TTE) wireless communication system is the system most likely to survive after a mine disaster because its signal penetrates the earth directly and does not use wires connecting the surface and underground components. Typically, the transmit (Tx) and receive (Rx) antennas are vertically separated by the earth overburden in a coaxial arrangement. In this paper, we show that there are advantages to separating the Tx and Rx antennas horizontally (co-planar arrangement), hence, communicating within the mine itself, and offering the advantage of mobility for one of the antennas. In this paper, we present a two-layer model, with both Tx loop and Rx loop antennas buried at the same depth underground. The magnetic field distribution results at the Rx loop are obtained for various conditions, such as earth conductivity, conductivity contrast between two layers, and co-planar and co-axis for the same Tx and Rx separation distance, providing us with an understanding of the parameters that control the performance and a concise method to predict the performance of a co-planar TTE loop communication system.