Noise canceller of ELF-band electromagnetic noise for underground transmission of EM-MWD

A real-time adaptive noise canceller (ANC) based on the least mean square algorithm was developed for the cancellation of ELF-band noise for the transmission system of an electromagnetic measurement-while-drilling (EM-MWD) system. To estimate the canceling ability of the ANC, the simulated signal, which was corrupted by additive noise actually recorded in the drilling fields, was estimated by the ANC and was demodulated using the testing set. For the purpose of deciding the optimal transmitting parameters of the EM-MWD system, such as carrier frequency or baud rate, it was necessary to estimate the noise canceling ability of the ANC using the spectrum of the ANC main input and the coherence function between ANC inputs. According to the experiment using the noise recorded in the drilling fields, the ANC reduces the noise by up to 20 dB, and this noise canceling ability agrees with the estimate made using the primary and the reference input.<
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