Digital filter design for peak detection of surface EMG.

A simple Low-Pass Differential (LPD) filter is often used for the Motor Unit Action Potential (MUAP) peak detection in needle EMG decomposition. Decomposition of surface EMG is much more difficult since surface EMG is more mixed than needle EMG. A successful peak detection of MUAPs is a first important step for EMG decomposition. We found that a simple LPD filter is not suitable for surface MUAP detection; instead the Weighted Low-Pass Differential (WLPD) filters are proposed. The filter performance is analyzed based on different window selection and varying MUAPs from simulated and recorded surface EMG. The sinusoidal WLPD filter is found to have better SNR improving factors, and to be more robust under the varying conditions.