The MINER Act of 2006 requires the installation of post-accident, two-way, communications and electronic tracking systems for all coal mines. A through-the-earth (TTE) wireless communication system sends its signal directly through the overburden of a mine but can have limitation relative to performance, reliability, and transmission range. The National Institute for Occupational Safety and Health (NIOSH) conducted experiments at a coal mine for different TX/RX antenna arrangements using a NOISH TTE prototype system. This system uses multi-turn, relative small TX loop antenna instead of single turn, relative large TX loop antenna. The objectives of the test are to evaluate the performance of the system, to evaluate the path loss and optimize working frequency for the mine, to characterize surface and underground electromagnetic noise, and to investigate the feasibility of horizontal TTE communication and its advantage over vertical TTE communications. In this paper, the performance of a magnetic loop TTE communication system was evaluated for various antenna arrangements. A fairly large communication range was achieved for horizontal TTE transmission. While vertical TTE communication between underground and the surface may be restricted by factors like deployment challenges of the surface TX antenna and short transmission ranges, horizontal TTE communication within the tunnel can reach relative large distances and can thus establish a more reliable communication. Moreover, the combination of vertical and horizontal TTE communication may provide a way to considerably increase communication range.
['Lincan Yan', 'Carl Sunderman', 'Bruce G. Whisner', 'Nicholas W. Damiano', 'Chenming Zhou']
Antenna arrangement investigation for through-the-earth (TTE) communications in coal mines