Data-Driven Self-Tuning in a Coordination Programming Language

Coordination programming is a paradigm for managing composition, communication, and synchronisation of concurrent components. AstraKahn is a new dataflow coordination language based on Gilles Kahn’s model of process network with some significant refinements. AstraKahn provides a mechanism of implicit data parallelism that is expected to rely on self-tuning, i.e. adaptive optimisation of execution parameters in order to improve the performance of the program. This is achieved by providing a programmer with a number of special network primitives that allow an AstraKahn runtime system to extract optimisation parameters and adjust them while monitoring the performance of execution. In this thesis, we present the architecture of an AstraKahn prototype including a compiler and a runtime system. On the runtime system level the built-in compound network primitives are constructed from simple ones. This approach allows us to make the implementation clear and easily extensible. As a minor contribution we present a number of potential self-tuning heuristics for a simple network pattern. Also, for illustrative purposes, a practical application of the morphism pattern is presented. The particle-in-cell problem, whose parallelisation requires load-balancing, is formulated this way

Antennas and beam-steering arrays for polarization diversity and full-duplex applications

This thesis presents new designs for polarization diverse dielectric resonator antennas (DRAs) as well as antennas that can offer efficient full-duplex (FD) functionality. Basically, this research effort has been completed to meet the demands of modern tracking systems as well as in-band full-duplex communication systems. For these applications antenna polarization control, compatibility, co-location, and isolation are the important parameters to support these high-performance systems. The first part of the thesis covers the challenges of modern radio frequency (RF) environments where the proposed polarization reconfigurable antennas are introduced. At first, a multi-port DRA is outlined as a possible candidate for the global positioning system (GPS) and the Global Navigation Satellite System (GNSS). To further advance this original design, and in an effort to reduce the size whilst maintaining polarization control, an integrated circuit was also proposed and tested. Advancing from the research work of phase polarization control using DRAs, the second part of the thesis studies other new antennas which are suitable for FD communications. Those antennas offer high isolation which makes the signal recoverable for those FD systems. To advance the state-of-the-art, an H-shaped slot antenna arrangement with parasitic patches and dual-differential feeding was proposed. The antenna architecture was investigated with both external and integrated feed systems and both prototypes offer high isolation levels. The single-element was further integrated into a 1×4 antenna array which was shown to offer similar isolation levels and with the capability to beam steer. Further research included high isolation antennas for operation in the 5G mm-wave band. In particular, a new FD pattern reconfigurable antenna was proposed which can be used in dual-polarized radars and other FD systems. Depending on the input phase excitation, the beam pattern control can be established with sum or difference patterns or both. Also, the antenna concept was further extended into a novel FD antenna array. This array has a similar common and/or differential feeding which can provide sum or difference patterns in the far-field. Also, an external Butler matrix was used to investigate the beam-steering capabilities of the array. These antenna systems also have applications for dual-polarized radars, retro-directive arrays, and other beam-tracking scenarios which require high inter-port isolation.James Watt Scholarshi

Printed Leaky-Wave Antenna with Aperture Control using Width-Modulated Microstrip Lines and TM Surface-Wave Feeding by SIW Technology

This letter presents a width-modulated microstrip line leaky-wave antenna (LWA) with substrate-integrated waveguide and microstrip feeding. In particular, the planar antenna system consists of an integrated surface-wave launcher and three identical rows of quasi-periodic width-modulated microstrip lines for TM leaky-wave excitation, which produces a tailored binomial-like aperture distribution on the guiding surface. The behavior of the antenna when changing the width-modulated lines for different aperture distributions is also analyzed and presented. The measured LWA demonstrates a fan beam pattern in the far field with realized gain values greater than 10 dBi and with a beam direction of about −20◦ from broadside at 23 GHz. Also, far-field measurements and near-field data indicate that the half-power beamwidth is below10◦, and the position of the main beam maximum is relatively stable, i.e., ranging from about −23◦ to −15◦ between 23 and 24 GHz. The measured prototype is also well matched over these frequencies and |S11| < −20 dB at 23.5 GHz