Surface Field Measurements From a Buried UHF Transmitter: Theory, Modeling and Experimental Results

Electromagnetic interference between a direct ray and a lateral wave was postulated theoretically but has been only observed near to the ground surface in a forest canopy. This communication reports surface measurements of the electric field profile from a 433 MHz transmitter buried up to 600 mm in sand (relative permittivity 2.13, conductivity 10
⁻⁴
S/m). A strong interference pattern with nulls greater than −20 dB were observed extending laterally to more than 5 m. This interference was evident when both the transmitter and receiver lay on the surface and when separated by an above ground conducting shield. Forward modeling using the impedance method and the finite integral technique adequately predict the interference pattern. These observations impact open-pit mining, surface and buried wireless sensor networks, and under-road communications systems.