Mining Contract: Low-Frequency Electromagnetic Noise Cancelling Antenna System
A receiver antenna system is needed that reduces the atmospheric background noise encountered at frequencies that are deeply earth penetrating. Field demonstration is desirable of the improved receiver technology using through-the-earth signals from coal mines.
Contract Status & Impact
This contract is ongoing.
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. 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.
Research under this contract will field test 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.
The prototype system developed under this contract will be demonstrated at both a shallow and deep mine. The antennas will be easy to deploy—i.e., one person will exit a vehicle, place a unit on the ground, activate a power switch, and then drive away. The antennas will also be easy to carry, as the necessary locations will not always be immediately accessible from a vehicle. This method of deployment also suggests that the receivers must have their own power source, likely a battery, and a wireless data link.
The research is currently in the hardware and software validation phase in preparation for the mine field tests. Prototype antennas have been fabricated and characterized, and the radio frequency (RF) networking solution has been assembled and validated. Surface-only tests have been performed with the prototype system at a remote, electromagnetically quiet rural location. Preparations are being made to perform testing at mine sites.