A continuous-time speech enhancement front-end for microphone inputs

In this paper, we propose a real-time noise suppression system implemented with analog VLSI. The algorithm implemented is designed to reduce stationary background noise while preserving the non-stationary signal component. Because the system relies on analog computation rather than digital, it has benefits such as extremely low power consumption and real-time computation. The algorithm is based on digital signal processing foundations that are slightly adjusted for use in the continuous-time domain. The analog components described as part of this system include a C⁴ second-order section bandpass filter, peak and minimum detectors, a translinear division circuit, and a differential multiplier. Floating-gate circuits are used to set bias points and adjust offsets.