ANALYSIS ALGORITHMS FOR A FIRST-AID SENSOR - Detecting Vitality Parameters such as Pulse and Respiration

A stream of demodulated data is converted to unidirectional pulses, multiplied by two clock reference signals separated by 90 degrees to form two products, which products are low pass filtered and cross multiplied by the same two clock reference signals, and the products produced are summed together to provide a clock reference which is in-phase with the switching times of the data pulses. The in-phase clock pulses operate a sampling circuit to sample the data at each switching point.