Characterization and comparison of envelope detectors for wake-up sensor interfaces at audio frequencies

Ultra-low-power analog hardware interfaces are becoming often used for continuous monitoring of weak, rarely and randomly occurring (spurious) acoustic events. Detection often requires interfaces for analog-domain time-frequency decomposition. These interfaces most often have a generic structure incorporating the same processing blocks, such as amplification, filtering, rectification, quantization and rudimentary classification. A critical processing block of the wake-up sensor interface is the envelope detector. In this paper we select four envelope detector topologies and show simulation and measurement results of their key parameters for their application in wake-up sensor interfaces. The selected envelope detectors must have short transient times (< 100 ms), used to rectify weak input signals (under 10 mV) in the lower audio frequency range and have a low power consumption to make them applicable in wake-up sensor interfaces.