1,595 research outputs found
Integrated radio frequency synthetizers for wireless applications
This thesis consists of six publications and an overview of the research topic, which is also a summary of the work. The research described in this thesis concentrates on the design of phase-locked loop radio frequency synthesizers for wireless applications. In particular, the focus is on the implementation of the prescaler, the phase detector, and the chargepump.
This work reviews the requirements set for the frequency synthesizer by the wireless standards, and how these requirements are derived from the system specifications. These requirements apply to both integer-N and fractional-N synthesizers. The work also introduces the special considerations related to the design of fractional-N phase-locked loops. Finally, implementation alternatives for the different building blocks of the synthesizer are reviewed.
The presented work introduces new topologies for the phase detector and the chargepump, and improved topologies for high speed CMOS prescalers. The experimental results show that the presented topologies can be successfully used in both integer-N and fractional-N synthesizers with state-of-the-art performance.
The last part of this work discusses the additional considerations that surface when the synthesizer is integrated into a larger system chip. It is shown experimentally that the synthesizer can be successfully integrated into a complex transceiver IC without sacrificing the performance of the synthesizer or the transceiver.reviewe
Neural Models of Subcortical Auditory Processing
An important feature of the auditory system is its ability to distinguish many simultaneous
sound sources. The primary goal of this work was to understand how a robust, preattentive
analysis of the auditory scene is accomplished by the subcortical auditory system.
Reasonably accurate modelling of the morphology and organisation of the relevant auditory
nuclei, was seen as being of great importance. The formulation of plausible models and their
subsequent simulation was found to be invaluable in elucidating biological processes and in
highlighting areas of uncertainty.
In the thesis, a review of important aspects of mammalian auditory processing is presented
and used as a basis for the subsequent modelling work. For each aspect of auditory
processing modelled, psychophysical results are described and existing models reviewed,
before the models used here are described and simulated. Auditory processes which are
modelled include the peripheral system, and the production of tonotopic maps of the
spectral content of complex acoustic stimuli, and of modulation frequency or periodicity. A
model of the formation of sequential associations between successive sounds is described,
and the model is shown to be capable of emulating a wide range of psychophysical
behaviour. The grouping of related spectral components and the development of pitch
perception is also investigated. Finally a critical assessment of the work and ideas for future
developments are presented.
The principal contributions of this work are the further development of a model for pitch
perception and the development of a novel architecture for the sequential association of
those groups. In the process of developing these ideas, further insights into subcortical
auditory processing were gained, and explanations for a number of puzzling psychophysical
characteristics suggested.Royal Naval Engineering College, Manadon, Plymout
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