Ocean acoustic tomography (OAT) is a method for mapping the physical characteristics of the world’s oceans. This technique enables the properties of a region of ocean – its temperatures, salinities, densities, and current speeds – to be inferred by measuring the propagation times of pulses transmitted between an array of transducers that surround the region. Central to the development of OAT is the availability of low frequency (< 500 Hz), low Q (< 4), light (< 250 kg), and efficient (> 50 %) sound sources that can operated at depths in excess of 500 m. Following a review of transducer motor and flextensional transformer technologies, the class I flextensional transducer driven by a piezoelectric ceramic stack is selected as being suitable for OAT. Finite element (FE) techniques are applied to the design of this transducer. By observing the change in pertinent performance characteristics of the device in response to altering various design parameters a set of design rules is established. In applying these rules an OAT projector has been designed. A scaled prototype has been constructed and the measured performance characteristics concur with FE predictions. Based on these results a full-scale device is expected to meet the requirements for an OAT projector, with the exception of weight, though this has to be verified. In order to accurately determine the performance characteristics of a transducer it is essential to know the phenomena that limit the acoustic power output of the transducer; these could be one or more of the following: (a) cavitation, (b) electrical failure, (c) mechanical failure, (d) thermal failure. Power limitations arising from (a) or (b) can be determined from empirical data, whilst those arising from (c) or (d) are best determined using numerical methods. FE software is readily obtainable for assessing the mechanical behaviour of transducers, however, no commercial software is currently available for determining thermal behaviour. To this end new FE software has been developed and applied to the analysis of various transducers. Experimental results are presented to validate the accuracy of this new software.

The advent of body worn devices and the use of them for a wide range of applications, from entertainment to military purposes, indicate the need to investigate to the behaviour of antennas and wave propagation on the body in depth. Knowledge and understanding and of the on-body channel can lead to the design of efficient antennas and systems for wearable devices. The objective of this work is to identify the propagation mechanism on the body for different polarisation states at 2.45 GHz. In particular, the effect of the body on the antenna performance with normal and parallel polarisation is studied and their capability in launching surface waves is evaluated. It is shown that both vertically and horizontally polarised antennas can launch a transverse magnetic (TM) Norton surface wave mode regardless of their polarisation states. However, horizontally polarised antennas do not launch the wave as strongly as vertically polarised antennas. Also, the change in the far field and near field behaviour of the antennas such as a dipole in proximity to the body is investigated and the observations lead to the design of a novel surface wave parasitic array. This new antenna is directive and can increase the path gain by almost 10 dB compared to other planar antennas. In addition, the effect of the polarization of the antenna on channel path gain is studied and channel cross polarization discrimination is quantified, using both simulation and measurement.

This thesis describes research into Negative Impedance Converters (NIC) for antenna matching. There are many applications that require small wideband antennas, from mobile phones and devices which are being required to cover larger frequency bands to cognitive radios that are expected to operate within any frequency band with minimum reconfiguration. However, fundamental limits on antennas such as the Chu-Harrington and Bode-Fano restricts the bandwidths obtainable from small antennas and antennas matched using conventional Foster reactive elements. However, non-Foster elements realised using NICs have been shown to provide wideband matching of antennas independent of frequency. In this thesis, a non-Foster element is designed based on Linvill’s model. A drawback on NIC is stability therefore a new stability analysis is developed and reported in this thesis which correctly predicts the frequency of oscillation. With the aid of this new stability analysis, a 1.5GHz NIC prototype is developed, operating up to 1.5 GHz. Its performance in terms of noise and linearity are also characterized. Another novel NIC schematic is also introduced in the thesis; it makes use of a single transistor and a pair of coupled lines. Because of its use of a single transistor, stability is less critical and hence it is able to achieve a working frequency of 6GHz. Its performance is compared with the NIC based on Linvill’s model. The coupled line NIC has been integrated with an antenna and this prototype shows the expected wideband performance with good gain. System implications of using NICs within an antenna is discussed.

In this thesis few new code sets and a multi-user interference (MUI) cancellation scheme have been proposed for Optical Code Division Multiple Access (OCDMA) systems, which can be employed in the next generation of global communication networks to enhance their existing systems’ performance dramatically. The initial evaluation of the proposed code sets shows that their implementation improves the performance, decreases the BER and increases security considerably. Also the proposed MUI cancellation scheme totally removes all the cross-talk and interference between the active users within the network. These novel schemes and codes can be easily implemented in the optical packet switched networks. Optical switching has the ability of bandwidth manipulation at the wavelength level (e.g. with optical circuit/packet/burst switching); the capability to accommodate a wide range of traffic distributions, and also to make dynamic resource reservations possible. This thesis first gives a brief overview of co-channel interference reduction in OCDMA networks, then proposes two novel code sets, Uniform Cross-Correlation Modified Prime Code (UC-MPC) and Transposed UC-MPC (T-UCMPC), along with their evaluation and analysis in various systems, including IP routing over an OCDMA network. Thereafter, the new MUI cancellation scheme is proposed and then the proposed code sets and the MUI cancellation scheme are implemented and analysed in a laboratory-based experimental test bed. Finally the conclusion of this research is discussed.

Forward Scatter Radar (FSR) is a subclass of the bistatic radar, where the received target signal occurs mainly due to the direct path signal shadowing by the target body. Employing a separate deployed transmitter and receiver at considerable distance, the FSR can achieve a number of advantages, such as enhanced radar cross section, inherent detection ability of stealth target, reasonably low complexity design of system, more than the conventional monostatic radar. All of these features are attractive to the modern remote sensing systems. This thesis presents the research results of the detection and speed estimation of the ground target in FSR, which is a vital procedure for automatic targets classification. The hardware was designed and assembled by the Microwave Integrated Systems Laboratory (MISL), University of Birmingham. The experimental data used in this thesis have been collected from real field environments at multiple locations and from various targets. The complex automatic target detection and speed estimation algorithm were integrated to achieve higher accuracy. The main problem investigated in this research and the appropriate results are dedicated to automatic target speed estimation in complex FSR operational scenario. The improved and originally proposed algorithms are discussed and shown throughout the chapters in great detail. The measurements are implemented in large load of work and the database is created for the validation of these algorithms.

Testing of digital VLSI circuits entails many challenges as a consequence of rapid growth of semiconductor manufacturing technology and the unprecedented levels of design complexity and the gigahertz range of operating frequencies. These challenges include keeping the average and peak power dissipation and test application time within acceptable limits. This dissertation proposes techniques to addresses these challenges during test. The first proposed technique, called bit-swapping LFSR (BS-LFSR), uses new observations concerning the output sequence of an LFSR to design a low-transition test-pattern-generator (TPG) for test-per-clock built-in self-test (BIST) to achieve reduction in the overall switching activity in the circuit-under-test (CUT). The obtained results show up to 28% power reduction for the proposed design, and up-to 63% when it is combined with another established technique. The proposed BS-LFSR is then extended for use in test-per-scan BIST. The results obtained while scanning in test vectors show up to 60% reduction in average power consumption. The BS-LFSR is then extended further to act as a multi-degree smoother for test patterns generated by conventional LFSRs before applying them to the CUT. Experimental results show up to 55% reduction in average power. Another technique that aims to reduce peak power in scan-based BIST is presented. The new technique uses a two-phase scan-chain ordering algorithm to reduce average and peak power in scan and capture cycles. Experimental results show up to 65% and 55% reduction in average and peak power, respectively. Finally, a technique that aims to significantly increase the fault coverage in test-per-scan BIST, while keeping the test-application time short, is proposed. The results obtained show a significant improvement in fault coverage and test application time compared with other techniques.

The growing demand for development and deployment of new wireless services has influenced the hardware design procedure including antennas and radio frequency (RF) front end, particularly in portable devices. Hence, novel solutions that are multiband, multimode, low profile, low cost and easy to integrate into the feature-rich compact devices are required. The research described in this thesis concerns integrating wideband and narrowband functionality and therefore adding to the versatility of the antenna systems in various wireless scenarios. The integration concept is based on sharing some sections of one antenna between several other antennas. This approach may be useful in designing multimode wireless terminals while keeping the required antenna footprint small. Based on this concept a demonstrator antenna is designed and verified. The power coupling between the two modes is studied and several solutions are presented. To demonstrate the versatility of this concept, the possibility of frequency reconfiguration is explored for narrowband mode using matching circuits with fixed elements. Wideband and reconfigurable narrowband functionality may potentially be of advantageous in emerging wireless communication systems such as software defined radio and cognitive radio for wideband sensing and reconfigurable narrowband communication procedure. Furthermore, the antenna integration within a device platform is studied. A technique is proposed to mitigate the unwanted effects of printed circuit board on the printed wideband antenna characteristics. As a result the radiation pattern, gain and group delay are stabilised across the band.

This study presents a novel synthesis technique for Butler matrices that include filter transfer functions through a circuit based only on resonators. The Butler matrix is the fundamental building block to split and recombine the signals in Multi-port Power Amplifiers, where multiple inputs are delivered to a bank of amplifiers sharing them, and later recombined through an output network. However, to suppress spurious frequencies generated by the amplifiers or to provide near-band rejection in order not to interfere with other transmission/receiving bands, separate filtering is often required. Here, the traditional properties of the Butler matrix are included together with filtering selectivity into one single device based only on coupled resonators. An analytical synthesis procedure of the coupling matrix is presented here for the first time. The proposed solution has shown significant advantages in terms of size reduction compared to the traditional baseline consisting of a Butler matrix plus a bank of band-pass filters. Based on the technique proposed, three prototypes are designed and manufactured: a 180° hybrid coupler based on resonators and two versions of a 4x4 Butler matrix with filtering, built with additive manufacturing and with milling. Experimental measurements are in good agreement with simulations and theoretical expectations.

Wireless Sensor Networks (WSNs) use geographic routing to deliver measurement data to one or more sink nodes. In employing geographic routing, where data packets are forwarded along approximate geodesic (shortest) paths, WSNs can distribute the forwarding task unevenly between nodes. Nodes closest to the data sinks, or the geographic centre of the network coverage area, as well as nodes at the periphery of void areas, carry significantly more traffic. Consequently, their batteries deplete at a faster rate than the remaining nodes, causing void areas to form and grow, thus decreasing the overall network lifetime below its potential value. This thesis proposes a novel power-aware routing protocol inspired by the propagation of light-rays in graded-index media, aiming to balance the load over the network and to extend the overall network lifetime with minimal, local coordination overheads only. The idea has been implemented in a custom-built network simulator, where two versions of the algorithm were constructed: Curvy routing, which uses a fixed refractive index distribution and Energy Aware routing, which takes into account energy level changes to update the refractive index. Comparisons have been made between those, a baseline protocol and existing solutions in the literature, where simulation results have shown that the proposed protocols perform better in sparse networks, providing a realistic and plausible solution which can be applied successfully in real-life scenarios.

An augmented reality (AR) system needs to track the user-view to perform an accurate augmentation registration. The present research proposes a conceptual marker-less, natural feature-based AR framework system, the process for which is divided into two stages - an offline database training session for the application developers, and an online AR tracking and display session for the final users. In the offline session, two types of 3D reconstruction application, RGBD-SLAM and SfM are integrated into the development framework for building the reference template of a target environment. The performance and applicable conditions of these two methods are presented in the present thesis, and the application developers can choose which method to apply for their developmental demands. A general developmental user interface is provided to the developer for interaction, including a simple GUI tool for augmentation configuration. The present proposal also applies a Bag of Words strategy to enable a rapid "loop-closure detection" in the online session, for efficiently querying the application user-view from the trained database to locate the user pose. The rendering and display process of augmentation is currently implemented within an OpenGL window, which is one result of the research that is worthy of future detailed investigation and development.