A Multimodal Hand Gesture Recognition System Utilizing PPG and Impedance Sensors

Impedance and Photoplethysmography (PPG) sensors are individually used for wide range of sensing applications. This paper presents a multimodal system for hand gesture recognition which combines these two sensors for the interpretation of signed languages. The impedance sensor is comprised of compact voltage and current comparators for extracting the capacitive and resistive components. The PPG sensor is based on a current steering DAC, LED driver driving two commercially available LEDs, and a single-photon avalanche diode (SPAD) based photodetector. A low-dropout (LDO) regulator maintains two different regulated supply voltages for the system. A mixer, whose local oscillation frequency is provided by a VCO, was also included. The system was designed in a 6 layer, 1 poly, 180 nm CMOS process. The total power consumption of the multimodal system is 100.5mW in 0.027 mm
²
area. The impedance sensor can measure from 1 to 10 kΩ and 1 to 250 nF of capacitance. The PPG sensor has a resolution of 0.75 mA/bit.