Cochlear filters design using a parallel dilating-biquads switched-capacitor filter bank

A parallel filter bank is proposed to implement cochlear filters using very-large-time-constant switched-capacitor (SC) biquads. Significant hardware reduction is achieved in three ways. First, the number of biquads is reduced by biquad-sharing such that each channel consists of three biquads in parallel, and a n-channel filter bank requires only n+2 biquads and n sum-gain amplifiers for implementation. Secondly, area-efficient SC biquads are used, and the capacitor spread of each biquad is approximately 1/√Ω₀T, where Ω₀ is the pole frequency and T is the sampling period. Finally, a lowpass notch biquad is used to avoid a zero at z=-1, which results in a very small capacitor in each biquad. Simulation results for a 32-channel filter bank are given to demonstrate the validity of this design