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.