Improving the Signal-to-noise Ratio of Surface-NMR Measurements by Reference Channel Based Noise Cancellation

The technique of surface-NMR (also called Magnetic Resonance Sounding) as unique hydro-geophysical prospection method has shown several improvements in data processing, inversion and interpretation during the last years. But the applicability of surface-NMR is often limited due to bad signal-to-noise ratio, i.e., the measurable NMR signal is masked by electromagnetic noise. Therefore, improving s/n ratio is a demanded development. According to newly introduced improved instrumentation providing simultaneous multi-channel recording the development of reference techniques is possible. We present and describe a noise cancellation approach based on predictive filter. Our approach allows to handle amplitude and phase differences of the signals recorded at the detection and reference loop. Furthermore, size and shape of the loop may not be equal. The technique is assessed with synthetic and field examples that clearly show the signal improvements obtained using the presented noise cancellation approach.