Study, Design and Fabrication of an Analogue VLSI Ormia-Ochracea-Inspired Delay Magnification System
Creators: name: Kongpoon, Metha
Publisher: name: Imperial College London
Year: 2011

description: This Thesis entails the development of a low-power delay magnification system inspired by the mechanical structure of the ear of the parasitoid fly Ormia Ochracea (O2). The proposed system is suitable as a preprocessing unit for binaural sound localization processors equipped with miniature acoustic sensors. The core of the Thesis involves the study of a delay magnification system based on the O2 sound localization mechanism and the design and testing of a low-power analog integrated circuit based on a proposed, novel delay magnification system inspired by Ormia Ochracea. The study of the delay magnification system based on the O2 sound localization mechanism is divided into two main parts. The first part studies in detail the delay magnification mechanism of the O2 ears. This study sheds light and tries to comprehend what mechanical parameters of the O2 ears are involved in the delay magnification process and how these parameters contribute to the magnification of the delay. The study presents the signal-flow-graph of the O2 system which can be used as a generic delay magnification model for the O2 ears. We also explore the effects of the tuning of the O2 system parameters on the output interaural time difference (ITD). Inspired by the study of the O2 system, in the second part of our study, we modify the O2 system using simpler building blocks and structure which can provide a delay magnification comparable to the original O2 system. We present a new binaural sound localization system suitable for small ITDs which utilizes the new modified O2 system, cochlea filter banks, cross-correlograms and our re-mapping algorithm and show that it can be used to encode very small input delay values that could not be resolved by means of a conventional binaural processor based on the Jeffress’s coincidence detection model. We evaluate the sound localization performance of our new binaural sound localization system for a single sound source and a sound source in the presence of a competing sound source scenario through detailed simulation. The performance of the proposed system is also explored in the presence of filter bandwidth variation and cochlea filter mismatch. After the study of the O2 delay magnification system, we present an analog VLSI chip which morphs the O2 delay magnification system. To determine what topology is the best morphing platform for the O2 system, we present the design and comparative performance of the O2 system when log-domain and gm-C second order weak-inversion filters are employed. The design of the proposed low-power modified O2 system circuit based on translinear loops is detailed. Its performance is evaluated through detailed simulation. Subsequently the Thesis proceeds with the design, fabrication and testing of the new chip based on the modified O2 circuit. The synthesis and testing of the proposed circuit using 0.35μm AMS CMOS process technology parameters is discussed. Detailed measured results confirm the delay magnification ability of the modified O2 circuit and its compliance with theoretical analysis explained earlier in the Thesis. The fabricated system is tuned to operate in the 100Hz to 1kHz frequency range, is able to achieve a delay gain of approximately 3.5 to 9.5 when the input (physical) delay ranges from 0μs to 20μs, and consumes 13.1μW with a 2 V power supply.