Noise Coil For Improving Sensitivity in a Fully Passive Bio-Magnetic Signal Detection System

Human emitted bio-magnetic signals are beneficial for several healthcare applications, yet they are difficult to capture due to their low magnitude. Overcoming limitations in the state-of-the-art, we previously reported a sensing system that can capture these signals in a non-contact, non-shielded, and low-cost manner. In this work, we take a major step further and demonstrate a noise coil subtraction scheme that successfully increases the sensitivity of the system. In vitro experimental results confirm that a reduced number of notch filters (10 vs. 13) are required to retrieve an 8.76 pT, 100–1000 Hz emulated evoked compound action potential (eCAP) signal with 30 minutes of averaging time when using the noise coil subtraction scheme. In the future, more advanced Digital Signal Processing (DSP) can be applied to adjust the level of noise for subtraction and further boost the sensitivity.