FILTERS FOR CANCELING MULTIPLE NOISE SOURCES IN BOREHOLE ELECTROMAGNETIC TELEMETRY SYSTEM

摘要

An electromagnetic borehole telemetry system providing improved signal to noise ratio. Adaptive filters (74) use noise channels (68) as references to remove noise from the signal channel (66). Multiple noise channels are coupl ed to series connected adaptive filters (74) for removing each noise source fro m the signal channel. The order of noise removal is selected to remove the mos t significant first.