Date of Award

2011

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

NIMBUS Centre for Embedded Systems Research

First Advisor

Dr. John Barrett

Abstract

Methods for shaping of sophisticated, transient, ultra wideband (UWB) waveforms and pulses are presented. The methods include novel circuits based on step recovery diodes (SRDs) and quasi-transversal filter concepts but the majority of the work focuses on UWB pulse shaping using completely passive nonuniform transmission lines (NUTLs). It is shown, for the first time, that NUTLs can be used to generate highly sophisticated arbitrary UWB pulse shapes, including modified Hermite polynomial (MHP) and approximate spheroidal wave function (APSWF) pulses which are not known to have been previously generated in practice, and a generalized methodology, verified by experiments, for design of NUTLs for UWB pulse shaping is presented. Also, a verified methodology for compensating for wideband loss and dispersion in NUTLs is demonstrated, believed to be the first time this has been achieved.

An extensive literature review demonstrates the need for more sophisticated UWB pulse shapes than can be generated using currently available approaches. The review examines these current approaches and, in particular, presents the state of the art in NUTL design and synthesis and in methods for compensating for NUTL non-idealities. It establishes that while NUTLs have the potential to be used for UWB pulse shaping, this has not been previously reported and that no satisfactory method for compensation for loss and dispersion in NUTLs exists.

Novel active circuits for UWB pulse shaping using SRD and quasi-transversal filter concepts are presented but these are shown to be limited in both the range and complexity of UWB pulses that can be generated. To overcome this, the development and verification are described of a novel methodology, assuming loss-free and dispersion-free lines, for synthesis of NUTLs capable of generating arbitrary UWB pulse shapes, including MHP and APSWF pulses which have previously only been described in theory. This methodology is then further extended to the first known verified methodology for compensation for the loss and dispersion that exist in practical NUTL. The scope of this last methodology has far greater applications than UWB as it is very general in its nature and its methodologies and techniques can be applied to the characterisation of non-uniform, one dimensional propagation inverse problems in known media e.g. transmission lines with known frequency-dependent propagation parameters and can also find use in, say, geology and acoustics.

Access Level

info:eu-repo/semantics/openAccess

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