A low-power current-mode correlation detector with analog data storage

A low-power, limited accuracy analog correlation circuit is proposed primarily for biomedical applications that process low-frequency signals. For storing the sampled analog values, a series of current switched capacitors are used, which offer the lowest sensitivity to external disturbances during data readout. The correlation was implemented in fully analog form applying the Manhattan method. The analog part of the comparator requires less than 1.3 mA, excluding the timing and supervising microcontroller. Applying the circuitry for phonocardiographic fetal heart rate (FHR) measurements, exhaustive simulations with real input sound records have shown that it can reliably identify the correlation peaks to calculate FHR with more than 90% confidence.