An all-digital spike-based ultra-low-power IR-UWB dynamic average threshold crossing scheme for muscle force wireless transmission

We introduce an Impulse Radio Ultra-Wide Band (IR-UWB) radio transmission scheme for miniaturized biomed-ical applications based on a dynamic and adaptive voltage thresholding of surface Electro Myo Graphy (sEMG) signals. The amplified sEMG signal is compared to a DAC-generated threshold computed from the previous 1-bit history by custom digital control logic running at 2kHz clock and implementing an ad-hoc algorithm (Dynamic Average Threshold Crossing, D-ATC). The resulting events and the associated digitized voltage level can be both asynchronously radiated through IR-UWB. Analyzes show that the scheme is robust w.r.t. the sEMG signal variability and correlates by ~96% with regard to raw muscle force information after signal is recomputed at the RX. This paper compares D-ATC with regard to a fixed threshold system and an Average Threshold Crossing (ATC) demonstrating improved robustness, and introduces the thresholding algorithm verified on a dataset of 190 sEMG recorded signals. The applied threshold resolution has been optimized to both minimize the size of transmitted data and to guarantee good correlation performance. The paper concludes with post-synthesis results of the D-ATC compact digital control logic in a 0.18μm CMOS process, demonstrating an extremely low power consumption at very low active area expenses.