Adaptive - Noise - Cancellation Techniques for Through-the-earth Electromagnetics. Volume II.
NTIS: PB/85-111409 Available for Reference At Bureau Libraries :121 pages
An electromagnetic (em) system to locate trapped miners at coal mine depths was investigated. The use of such a system in deep mines requires transmission at extremely low frequencies (elf) and a reduction in the effective noise level beyond that which can be obtained by acceptable integration times. Automatic-noise- cancellation (anc) techniques reduce the efective noise level by combining several received signals that contain correlated noise. The signals can be obtained from either a remote magnetic antenna or a local electric antenna. This report presents the results of a simulation of the use of anc techniques in a through-the-earth em system. A multicomponent elf noise model that incorporates impulsivity, direction of arrival, and ground characteristics was developed. Nonlinear processors (nlp) for elf noise were compared and the adaptive clipper was found to be preferable. Direct-matrix- inversion (dmi) and least-mean-square anc techniques were compared and the dmi algorithm was preferable. The performance of the combined nlp-anc system was evaluated.
CP; Final Contract Report;
NTIS Accession No.
NTIS: PB/85-111409. Available for Reference At Bureau Libraries.
Green Mountain Radio Res.