Mining Contract: Low-Frequency Electromagnetic Noise Cancelling Antenna System

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

This contract was funded as part of an interagency agreement program, which provides a formal means for federal government agencies to share and further technology that could apply to and benefit mine safety and health. The Office of Mine Safety and Health Research (OMSHR) identifies other government agencies with the knowledge, skills, and abilities relevant to a health and safety gap and works collaboratively with these agencies to identify the type of technology solution desired and to determine specifications for this technology.

Communication between rescuers at the surface and workers in underground mines is particularly important during emergencies, when conventional communication systems may be interrupted if sufficient infrastructure is damaged. An alternative is to directly communicate to the surface through the overburden. Typical high-frequency wireless technologies cannot penetrate significant distances through the earth, but signals at frequencies below 10 kHz can penetrate the earth and offer promising capabilities to establish through-the-earth (TTE) connections. TTE systems are more likely to survive an underground explosion and provide a communications link to the surface for trapped or escaping workers.

Under this contract research, the Los Alamos National Laboratory field tested the ability of the geophysical technique of remote sensing to improve the signal-to-noise ratio of surface-located TTE communication receivers. The remote sensing technique involves the deploying of some surface receive antennas near the expected location of the underground transmission while others are deployed at greater distances away. Atmospheric noise is expected to be nearly uniform among all antennas while signal will appreciably reduce at points more distant from the transmission. Combining responses from both far and nearby antennas is expected to yield an improvement in signal reception through the reduction of atmospheric noise.

This contract resulted in the development of two prototype tri-axial receivers synchronized in time over a Wi-Fi connection. During testing, one receiver was placed approximately above the underground source while the other was placed several hundred feet away. The final successful field test was run at Monzano Mountain, Kirtland Air Force Base, in Albuquerque, New Mexico, in both shallow (~40 feet) and deep (~200 feet) overburden. An improvement in signal-to-noise ratio was demonstrated (approximately 12 dB, best case.) This contract also resulted in the manufacture of custom, physically small yet effectively sensitive, air core receive antennas.