Application of weak signal nonlinear detection on MWD electromagnetic wave

In the electromagnetic wave logging engineering, as the depth of exploration deepens, the signal goes weaker and weaker. Therefore, the effective extraction of weak electromagnetic signals in the strong noise background is of great significance for guiding the exploration while drilling. The traditional filtering methods only filter the out-of-band noise, not the in-band noise. Therefore, this paper designs an out-of-band hardware filter circuit and in-band adaptive line enhancement(ALE) algorithm that based on the least mean square algorithm to construct the combination filtering algorithm. Theoretical analysis and simulation show that this algorithm can improve the calculation accuracy of weak signal with high dynamic range and low signal to noise ratio(SNR), effectively enhancing SNR and noise suppression ability. In addition, to filter the out-of-band noise, the in-band Gaussian white noise rejection is improved by about 10 dB in this algorithm, which helps to solve the actual engineering problem.