Underground wireless communications systems using high temperature superconducting receivers
- Los Alamos National Lab., NM (United States)
The ability to effectively communicate with both people and equipment in underground environments such as mines, tunnels, and boreholes is important from both an operations and safety perspective. Radio waves with frequencies above 10Mhz, such as cellular phones, do not propagate more than a few meters in a typical rock mass. Although these systems can be used in tunnels for line-of-sight communications, signal strength decreases drastically around corners. Many mines rely on hard-wired phone systems, but this is expensive, requires constant changing as tunnel systems change, and fails easily during tunnel collapse or fire. Near-field wireless systems typically use a system of repeaters and poorly shielded wiring that allow the signal to radiate weakly to be picked up by a receiver a short distance from the wiring. Ground penetrating signals are much greater at low frequencies, but the receivers for these low frequencies usually require a very large antenna (on either the transmit or receive side) to overcome the electrical noise of typical semiconductor components. One common mine paging system uses a transmit antenna several kilometers in diameter to achieve sufficient amplitude to drive a conveniently sized wire-wound ferrite core receiver. Superconducting components are the lowest noise of any electronics technology and have traditionally been used in applications where a low noise floor is critical, such as radio astronomy and noninvasive magnetoencephalography. The authors have developed a receiver for deeply penetrating low frequency radio waves using high temperature superconducting quantum interference devices (SQUIDS). The receiver consists of a SQUID, a small dewar, control electronics, and a battery pack. The receiver is several orders of magnitude more sensitive than conventional receivers of the same size and weight. SQUIDs also allow the compact construction of 3-axis receivers that are necessary to overcome a dominant source of vibrational or motional noise. The goal is to demonstrate an effective and reliable two-way voice underground wireless communication system. The low noise compact receivers also have application in geophysical tool development, survey techniques, and underground structure detection.
- OSTI ID:
- 324779
- Report Number(s):
- CONF-970931-; TRN: IM9911%%476
- Resource Relation:
- Conference: 14. annual international Pittsburgh coal conference and workshop: clean coal technology and coal utilization, Taiyuan (China), 23-27 Sep 1997; Other Information: PBD: 1997; Related Information: Is Part Of Fourteenth annual international Pittsburgh coal conference and workshop: Proceedings; PB: [1500] p.
- Country of Publication:
- United States
- Language:
- English
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