Wave Propagation Between Buried Antennas

Abstract

Buried antennas can be used in a variety of applications. For surface communication, parameters such as the ground conductivity and the depth of the buried antenna affect the channel attenuation between the antennas. A buried conical antenna for surface communication was developed at Soreq NRC. The antenna is axis-symmetric with two metallic plates, where the upper plate is conical and the lower is a flat disc. The wave propagation from the buried antenna is studied using an axis-symmetric finite-difference time-domain approach. It was found that the energy is radiated from the buried antenna to above the ground, where it forms a spherical surface wave. Due to the wave propagating above the ground faster than below the ground, the penetration of the surface wave into the ground is shaped as a shock wakefield. This wakefield is absorbed into the ground due to the finite ground conductivity. The shock wavefront corresponds to the Cherenkov angle cos <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (1/ε <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rg</sup> ), where ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rg</sub> is the ground relative dielectric permittivity. The channel attenuation from the buried antenna to a receiving antenna located either above or below the ground surface scales as 1/r <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> . Experimental demonstration was performed at 900 MHz . A good correlation was obtained for the channel attenuation between the experimental and simulation results, irrespective of whether the receiving antenna was located above or below the ground surface.