Real-Time Power Line Harmonics Suppression from MRS Based on Stacking and ANC

MRS (magnetic resonance sounding)) method is a direct method for underground water detecting which is easily disturbed by interferences according to its weak signal (nV). Time domain quantization methods require a good suppression of interferences for more accurate MRS signal parameter estimation. Of all interferences, power line harmonic interference is the most significant. To solve the problem, the paper analyzes the features of the MRS signal and the interference types and discusses two easily program integrated interference elimination method for MRS signal real time pretreatment. The stacking method based on random phase is an effective way to eliminate the interference but it requires massive stacks. Another method, adaptive noise cancellation (ANC) method is also proposed which is a more effective method especially in power line harmonic interference cancellation. Here an improved bidirection ANC method is proposed. The method can significantly eliminate the power line harmonic interference. Field test was carried out using JLMRS-I developed by Jilin University. With the method, the SNR of free induction decay (FED) records can be improved by 4 times with stacks 20 and nearly 100 times with stacks 160. The application of the bi-direction ANC method can improve the exploration efficiency under the same SNR of the FID records.