Two 25 ns wideband HTS delay lines with a novel double-spiral meander line (DSML) structure are designed, fabricated and measured. One is based on the conventional coplanar waveguide (CPW), and the other based on a conductor-backed coplanar waveguide (CBCPW). Systematic design work is presented in this thesis on the calculations of transmission-line parameters, the selection and optimisation of delay line patterns, and the modelling of the transitions and connections at the input/output. Simulations show that the DSML structure has better transmission efficiency over a wide frequency range than the conventional double-spiral line (DSL). The bandwidth and dispersion of such a meander structure are investigated. The fabricated delay lines are first characterised as resonators with a fundamental mode at ~20 MHz. The surface resistances of the superconductors and the temperature- and power-dependent properties are investigated by measuring the Q-values of more than 1000 harmonics from 20 MHz to 20 GHz. Then, the delay lines are fully connected as they would be used in the application and measured thoroughly in both the frequency and time domain. The performance of the CBCPW delay line is the best ever demonstrated in terms of the widest resonance-free band (2 to 18 GHz), low insertion loss (0.06 dB/ns at 60 K and 10 GHz), small ripple (<1 dB up until 16 GHz), and small dispersion (< 2 ns in the variation of group delay between 2 and 18 GHz). This is the first coplanar delay line successfully demonstrated without using bonding-wires to join the in-plane grounds. The spurious reflecting elements in the DSML structure are identified by the time domain analyses. The results from this measurement are compared comprehensively with those from both resonance measurement and simulations.

Due to its increasing applications in personal communications systems, body-centric wireless communications has become a major field of interest for researchers. Fading and interference are the two concerns that affect the reliability and quality of service of wireless links. Diversity has been used to overcome these two problems. This thesis looks into the use of receive diversity for on-body channels. Space, pattern, and polarization diversity performance is analyzed and quantified by actual measurements in real environments. Significant diversity gains of up to 10 dB are achieved for most of the on-body channels. The on-body diversity channels have also been characterized by performing the statistical and spectral analyses. The fast fading envelope best fits the Rician distribution, with moderate K-factor values, and the slow fading envelope best fits the Log-normal distribution. Diversity has been found effective in the BAN-BAN interference rejection and significant rejection gain values are achieved. A new algorithm for BAN-BAN interference rejection has been proposed and compared with the conventional adaptive algorithms. The use of multiple antennas at both the transmitter and receiver end, i.e., MIMO has been investigated for on-body applications. It has been noticed that MIMO provides significant capacity increase for these channels despite the line-of-sight.

This study investigates the Internet's resilience to instabilities caused by the mismatch of its topological state and routing information. A first numerical analysis proves that the Internet possesses unused path diversity which could be employed to strengthen its resilience to failures. Therefore, a new routing framework called Chain Routing, which takes advantage of such path diversity, is proposed. This novel idea is based in the mathematical concept of complete order, which is a binary relation that is irreflexive, asymmetric, transitive and complete. More important is the fact that complete orders, when represented as a graph, are the most connected digraph that does not contain any cycles. Consequently, a complete order could be applied to route information from a source to a destination with the guarantee that cycles will not develop in a path. A second numerical analysis demonstrates the feasibility of implementing Chain Routing as part of a routing protocol. Finally, an analysis is presented on how network stability could be maintained if a routing protocol integrates complete orders in time and topology.

The research presented in this thesis explores the impact of Augmented Reality on human performance, and compares this technology with Virtual Reality using a head-mounted video-feed for a variety of tasks that relate to scene examination. The motivation for the work was the question of whether Augmented Reality could provide a vehicle for training in crime scene investigation. The Augmented Reality application was developed using fiducial markers in the Windows Presentation Foundation, running on a wearable computer platform; Virtual Reality was developed using the Crytek game engine to present a photo-realistic 3D environment; and a video-feed was provided through head-mounted webcam. All media were presented through head-mounted displays of similar resolution to provide the sole source of visual information to participants in the experiments. The experiments were designed to increase the amount of mobility required to conduct the search task, i.e., from rotation in the horizontal or vertical plane through to movement around a room. In each experiment, participants were required to find objects and subsequently recall their location. It is concluded that human performance is affected not merely via the medium through which the world is perceived but moreover, the constraints governing how movement in the world is controlled.

Exploitation of the terahertz frequency region offers tantalising rewards over other parts of the congested spectrum, however current technologies and manufacturing methods are not yet commercially effective to capitalise on its riches. This thesis is concerned with developing new techniques to enable and improve radio frequency engineering design for tomorrow’s terahertz applications. The techniques in this thesis will provide engineer’s the knowledge to creatively tackle some of the challenges when designing at the terahertz scale. A novel design of a 9 to 18 GHz microstrip diode frequency doubler using the coupling matrix method is presented, which demonstrates new techniques for matching and integration of the circuit components. It illustrates a new approach for diode doubler design and provides a guide for solving the matching and integrating of passive circuits, such as input and output filters, to the active part of a circuit. Complex circuit interactions are controlled in the design, without the traditional reliance on circuit optimisation. Terahertz manufacturing technologies are investigated, and a 150 GHz E field plane terahertz waveguide using a polymer (SU-8) etching, layering and metal coating technology, is designed, constructed and measured. Such a device would be a fundamental component in a future terahertz frequency communication system.

A new multiple-model filter for target tracking has been developed and performed well in this thesis. The procedure of the new multiple model (MM) filter has no compromises between non-manoeuvre and manoeuvre, and between manoeuvres except in the ambiguous cases. The operation of the new MM filter is simple like VD filter but with no need for reconstruction of manoeuvre, and the new MM filter also considers all kinds of motions like interacting multiple model (IMM) filter but with a small number of models and significantly reduced computational load. The scheme of the new multiple-model tracking filter consists of manoeuvre detection, construction of manoeuvre filters, construction of safeguard filter, and filter selection. The performance of the proposed tracking filter mainly relies on manoeuvre detection, construction of manoeuvre model filter, and construction of safeguard model filter. In order to improve the tracking, several manoeuvre detection methods have been developed. One of the manoeuvre detection methods is to test the statistic of normalised optimally squared smoothed accelerations, and gives quicker detection than classical manoeuvre detection by testing normalised squared-innovation statistic, in spite of the smoothing lag. This thesis suggests that the manoeuvre be detected by testing the changes of the statistic of normalised squared innovations to give effective manoeuvre detection, based on Chen and Norton's (1986) detection by testing rapid parameter changes. The thesis also modifies Weston and Norton's (1997) change detection with the fixed-lag smoothing instead of the fixed-interval smoothing used by Weston and Norton's method, and obtains more accurate and quicker manoeuvre detection. According to the features of target motion, the target manoeuvres are modelled as straight-line acceleration motion, cross-track acceleration motion, and curvilinear acceleration motion. Thus the manoeuvre model filters can be constructed by these three kinds of motions with a limited number of manoeuvre model filters and reduced computational load. To avoid the risk of the loss of track, a safeguard filter is used in the case of uncertain manoeuvre. The safeguard filter is constructed by combining Singer's (1970) filter and input estimation, to provide at least comparable performance to IMM filter. Further improvement for multiple-model tracking is provided by using the fixed-lag smoothing technique. In comparison with the multiple-model filter alone, the fixed-lag smoothing multiple-model filter provides much better performance (even with fixed lag d=1), and can be implemented in a real time at the costs of a small delay and slight increase in computational load.

Over the past few years, numbers of research have been carried out to investigate the clutter characteristic especially for conventional monostatic and bistatic radar detection (mostly in maritime and airborne using Ultra Wide Band radar and Synthetic Aperture Radar) and not specifically on Forward Scatter Radar (FSR). FSR provides an efficient approach for detection of stealth target, the simplicity of the hardware design, increase the power budget and work in all weather operation. One of the limitations in forward scatter radar is the range resolution. Clutter mainly from the surrounding vegetation is picked up from a large area illuminated by transmitter and receiver which is located on the ground. Vegetation clutter is a significant factor that limits the performance of ground based Forward Scatter Radar. In this research, the analysis is focused on clutter on ground-based Forward Scatter Micro Radar system network where the clutter characteristics are studied for different environmental conditions such as different land sites, wind and weather conditions for different carrier frequencies. These comprehensive analyses are used eventually, to determine the clutter characteristics and are used for clutter modelling in order to create similar clutter-like signal that can be used to develop a synthetic environment for Forward Scatter Radar detection performance analysis in the future. Three main works have been done; 1) real measurements to determine the Clutter characteristic for FSR based on statistical analysis of a number of experiments; 2) modeling and simulation of clutter signal based on real signal characteristics and 3) the comparison of simulated and measured signals.

This thesis is dedicated to the study of innovative forward scatter radar (FSR) configurations and techniques. FSR is a specific kind of bistatic radar having bistatic angle equal or close to 180 ̊. The goal of this PhD project is to investigate techniques and configurations which would improve FSR performance, making it a more appealing system. This thesis proposes an initial radar overview with deep focus on forward scatter capabilities. FSR principles, radar cross section and target signature are widely discussed. Thus, numerous innovative studies done during this PhD project are presented. FSR passive mode, MIMO geometry and moving transmitter/ moving receiver configurations are here investigated for the first time. Numerous experimental campaigns have been undertaken and a big quantity of data has been collected. Comprehensive analyses on measured and simulated results are presented. Moreover, various novel techniques to estimate target motion parameters have been developed and tested on real and simulated data. Results show a good match between measured and estimated kinematic information. Finally, clutter in moving ends FSR is discussed. In fact, the innovative moving ends configuration is affected by Doppler shift and clutter Doppler spread. Thus, it is important to understand how this issue limits the system performance.

The Power Amplifier is the most challenging module of a wireless network to design and it is the highest power consumer. Lots of research has been dedicated to design highly efficient and linear power amplifiers. The high demand for wireless communication systems creates the requirement for multiband transmitters and receivers. Providing high efficiency for power amplifiers in multiband applications is even more challenging. The work presented in this thesis is focused on designing high efficiency frequency adaptive power amplifiers. Frequency adaptive power amplifiers are categorized in three groups: broadband, multi-band and switched-band power amplifiers. Two main design methodologies of frequency adaptive power amplifiers are proposed in this thesis. They are dual-band and switched-band power amplifiers. The advantages and limitations of their output performances are evaluated. The main goals in this thesis are achieving high efficiency and required output power over all working bands and maintaining consistent performance over the bandwidth. In the dual-band power amplifiers, the distributed matching network is designed without any switches. Both of the switched-band Class-E power amplifiers have switched shunt capacitor values. The results demonstrate the tradeoffs between achieving consistent high performance in each band and introducing losses and complexity in the switching design.

The work described in this thesis concerns the integration of push-pull class B amplifier and antenna modules. Push-pull class B is well-known with its fruitful advantages of using differential feeding technique, resulting in low distortion, reasonably high efficiency and high output power. Meanwhile, the antenna module in this work is adapted from the aperture-coupled antenna structure due to its degree of freedom to control the variables which provide the best possible topology that could be realised in system on chip or system in package. More generally, the variables allow good coverage of the Smith Chart so that a wide range of odd-mode matching requirements could be met, for different devices and bias condition of a given transistor. The approach also offers additional filtering up to 3rd harmonic in that it comprises identical harmonic traps on both sides of the aperture using resonant stubs to form bandstop filters, which reduce the ripples at the output waveforms, giving them a significant advantage of neat and tight integration of a push-pull transmitting amplifier.