| Abstract
|
:
|
This research focuses on biologically inspired audio signal processing usingprogrammable analog circuitry. This research is inspired by the biology of the humancochlea since biology far outperforms any engineered system in converting audio signalsinto meaningful electrical signals. The human cochlea eciently decomposes anysound into the respective frequency components by harnessing the resonance natureof the basilar membrane, essentially forming a bank of bandpass filters. In a similarfashion, this work revolves around developing a filter bank composed of continuoustime,low-power, analog bandpass filters that serve as the core front end to this siliconaudio-processing system. Like biology, the individual bandpass filters are tuned tohave narrow bandwidths, moderate amounts of resonance, and exponentially spacedcenter frequencies. To overcome mismatch and osets inherent in CMOS processes,floating-gate transistors are used to precisely tune the time constants in the filtersand to allow programmability of analog components.Like the biological cochlea, this audio front end serves to eciently convert incomingsounds into information useful to the subsequent signal-processing elements, andit does so by performing a frequency decomposition of the waveform with extremelylow-power consumption and real-time operation. This frequency decomposition canbe used to replace discrete Fourier transforms which are expensive computationallyand consume large amounts of power. As portable electronics progressively pervadeeveryday life, power constraints become increasingly important; the power savings ofthis analog frequency-decomposition block will be able to greatly extend battery lifein consumer electronics and embedded sensors, such as hearing aids and cohclear implants.Additionally, the floating-gate programmability of this filter bank, especiallywhen incorportated in a reconfigurable architecture, will allow versatility so that avariety of algorithms can be produced by the same integrated circuit.xiCHAPTER 1INTRODUCTIONBiological systems far outperform any engineered system at perceiving the outsideworld and making useful decisions based upon those perceptions. Biology is ableto perform these immensely complex perception and classification tasks at real-timespeeds yet only consume the little power that the body can provide. I believe that bylooking to biology for inspiration and by developing solutions that mimic biologicalstructures, engineers will be able to develop improved solutions to a variety of problemsthat will reduce power consumption, operate at real-time speeds, and performbetter than present techniques. Thus, in my research, I am focusing on developingbio-inspired analog circuits and systems for signal-processing applications.The human auditory system is capable of astonishing feats of recognizing words,adapting to dierent sound levels, and localizing sounds, all of which are dicult tasksto engineer well. However, the ability to incorporate these tasks into portable electronicswould revolutionize the marketplace. The market for portable audio devices(e.g. music players and cell phones) is steadily increasing, but standard methods forperforming the complex auditory algorithms consume far too much power and needtoo much overhead for inexpensive portable applications. If these tasks could be.,..tested for theQ1 PC1 bus cardBoth these projects mere sofixare des elopment efforts tonards contributing to dlfferentaspects of Roboucs and lZ1echatronics projects m the Controls and Roboucs Group..
|