Powerline interference suppression of a textile-insulated capacitive biomedical sensor using digital filters

Abstract

This research evaluated a textile-insulated capacitive (TEX-C) biomedical sensor insulated by six types of textile materials namely cotton, linen, rayon, nylon, polyester, and PVC-textile. Each textile material creates a unique skin-electrode capacitance and affected the susceptibility of the TEX-C biomedical sensor towards the 50 Hz powerline interference (PLI) and its harmonics. Designing versatile TEX-C biosensor hardware that can tolerate different textile insulators while maintaining an optimum signal measurement quality proves to be a significant challenge. Five digital filters such as notch filter, comb filter, discrete wavelet transform, undecimated wavelet transform, and normalized least mean squares adaptive filter were implemented to compare their performance in suppressing the 50 Hz PLI and its harmonics. The comb filter yielded the best results in suppressing the 50 Hz PLI and its harmonics below -130 dB while improving the correlation coefficient of the EMG signals measured by TEX-C biomedical sensors and the wet contact electrode.