A Bio-Inspired Active Radio-Frequency Silicon Cochlea

Abstract

Fast wideband spectrum analysis is expensive in power and hardware resources. We show that the spectrum-analysis architecture used by the biological cochlea is extremely efficient: analysis time, power and hardware usage all scale linearly with , the number of output frequency bins, versus log() for the Fast Fourier Transform. We also demonstrate two on-chip radio frequency (RF) spectrum analyzers inspired by the cochlea. They use exponentially-tapered transmission lines or filter cascades to model cochlear operation: Inductors map to fluid mass, capacitors to membrane stiffness and active elements (transistors) to active outer hair cell feedback mechanisms. Our RF cochlea chips, implemented in a 0.13 m CMOS process, are 3 mm 1.5 mm in size, have 50 exponentially-spaced output channels, have 70 dB of dynamic range, consume 300 mW of power and analyze the radio spectrum from 600 MHz to 8 GHz. Our work, which delivers insight into the efficiency of analog computation in the ear, may be useful in the front ends of ultra-wideband radio systems for fast, power-efficient spectral decomposition and analysis. Our novel rational cochlear transfer functions with zeros also enable improved audio silicon cochlea designs with sharper rolloff slopes and lower group delay than prior all-pole versions.

A Power-Efficient Capacitive Read-Out Circuit With Parasitic-Cancellation for MEMS Cochlea Sensors

“…In the typical designs based on the unity-gain buffers, the voltage output from the buffer is given by (1). In comparison, the output level is increased by at least a factor of in this design as suggested by (13). Under the extreme circumstance that the parasitic capacitance is fully canceled, the output level is increased by a factor of as suggested by (14).…”

“…5(b), forms a positive feedback loop from the output to the input of the PCC. According to (2), the equivalent input capacitance of the PCC is given by (11) According to (1), the sensed output voltage is derived as (12) Thus the output from the PCC is given by (13) The output reaches maximum when equals so that is fully canceled. The output in this case is given by (14) is designed to be variable by tuning the current so that the negative capacitance can be adjusted to match the parasitic capacitance.…”

Tone-vs.-Noise Dichotomy in Psychoacoustics Could be Resolved by Careful Consideration of Cochlear Signal Processing

“…Signal processing methods inspired by cochlear mechanics have been developed both in analog [10] and digital [9] domains. Nonlinearity was not desired in Mandal et al's analog circuit, while cochlear nonlinearity was mimicked by terminating every filter stage with a half-wave rectifier in Lyon's work.…”

A compact digital gamma-tone filter processor

“…A silicon cochlea which provides a good approximation of the human cochlea was proposed by Mandal et.al. [6]. One of the most recent 25 approaches was focused on building a bio-realistic analog CMOS Cochlea with high tunability and ultra-steep roll-off.…”