Mutual coupling in MIMO systems

The drive towards greater efficiency in communications systems has led to the birth of many new technologies and considerable improvements in existing systems over the last 20 years. These developments have been underpinned by increasing demands for higher data speeds, capacity and reliability by end users on a global level. Wireless communications systems have witnessed rapid transformations with this regard. Numerous enhancements in data capacities have been the hallmark of these systems. One of the principal components in achieving improved performance in wireless systems is the antenna system. Single Input Single Output (SISO) antenna topologies have traditionally been employed in wireless links. As the demand for higher data rates have persisted various limitations have arisen. Multiple Input Multiple Output (MIMO) antenna topologies have provided promise of the desired system capacity and reliability. Since MIMO systems employ two or more antenna pairs simultaneously, the effects of mutual coupling become a significant consideration in the quest to achieve high system performance. Therefore a clear understanding of mutual coupling effects with varying conditions in necessary for practical purposes. A lot of work has already been done on this subject. This thesis shall seek to substantiate some fundamental evidence on the relationship between mutual coupling effects and antenna element separation. The procedure shall involve the use of proven computer aided design software to achieve this purpose. Microstrip antennas (used interchangeably with patch antennas), widely known for their efficacy in wireless communications applications will be used for the tests. Specifically the more common linearly polarized rectangular microstrip antenna shall be utilised

An evaluation of the performance of multi-static handheld ground penetrating radar using full wave inversion for landmine detection

This thesis presents an empirical study comparing the ability of multi-static and bi-static, handheld, ground penetrating radar (GPR) systems, using full wave inversion (FWI), to determine the properties of buried anti-personnel (AP) landmines. A major problem associated with humanitarian demining is the occurrence of many false positives during clearance operations. Therefore, a reduction of the false alarm rate (FAR) and/or increasing the probability of detection (POD) is a key research and technical objective. Sensor fusion has emerged as a technique that promises to significantly enhance landmine detection. This study considers a handheld, combined metal detector (MD) and GPR device, and quantifies the advantages of the use of antenna arrays. During demining operations with such systems, possible targets are detected using the MD and further categorised using the GPR, possibly excluding false positives. A system using FWI imaging techniques to estimate the subsurface parameters is considered in this work.A previous study of multi-static GPR FWI used simplistic, 2D far-field propagation models, despite the targets being 3D and within the near field. This novel study uses full 3D electromagnetic (EM) wave simulation of the antenna arrays and propagation through the air and ground. Full EM simulation allows the sensitivity of radio measurements to landmine characteristics to be determined. The number and configuration of antenna elements are very important and must be optimised, contrary to the 2D sensitivity studies in (Watson, Lionheart 2014, Watson 2016) which conclude that the degree (number of elements) of the multi-static system is not critical. A novel sensitivity analysis for tilted handheld GPR antennas is used to demonstrate the positive impact of tilted antenna orientation on detection performance. A time domain GPR and A-scan data, consistent with a commercial handheld system, the MINEHOUND, is used throughout the simulated experiments which are based on synthetic GPR measurements.Finally, this thesis introduces a novel method of optimising the FWI solution through feature extraction or estimation of the internal air void typically present in pressure activated mines, to distinguish mines from non-mine targets and reduce the incidence of false positives

Mutual coupling in MIMO systems

The drive towards greater efficiency in communications systems has led to the birth of many new technologies and considerable improvements in existing systems over the last 20 years. These developments have been underpinned by increasing demands for higher data speeds, capacity and reliability by end users on a global level. Wireless communications systems have witnessed rapid transformations with this regard. Numerous enhancements in data capacities have been the hallmark of these systems. One of the principal components in achieving improved performance in wireless systems is the antenna system. Single Input Single Output (SISO) antenna topologies have traditionally been employed in wireless links. As the demand for higher data rates have persisted various limitations have arisen. Multiple Input Multiple Output (MIMO) antenna topologies have provided promise of the desired system capacity and reliability. Since MIMO systems employ two or more antenna pairs simultaneously, the effects of mutual coupling become a significant consideration in the quest to achieve high system performance. Therefore a clear understanding of mutual coupling effects with varying conditions in necessary for practical purposes. A lot of work has already been done on this subject. This thesis shall seek to substantiate some fundamental evidence on the relationship between mutual coupling effects and antenna element separation. The procedure shall involve the use of proven computer aided design software to achieve this purpose. Microstrip antennas (used interchangeably with patch antennas), widely known for their efficacy in wireless communications applications will be used for the tests. Specifically the more common linearly polarized rectangular microstrip antenna shall be utilised

Keeping the lights on or off : tracking the progress of access to electricity for sustainable development in Nigeria

This paper is focussed on employing satellite night lights (SNLs) to investigate access to electricity across the geographical regions in Nigeria. Specifically, we explore how SNLs interact with human and socioeconomic development indicators (population, poverty, and household consumption) to demonstrate the implications of slow and/or delayed progress in closing the electricity access gap in Nigeria. Our findings suggest that minimal progress has been made and there remains significant evidence of disproportionate spread of electricity across the country with most of the electricity visibility concentrated in the Southern regions, state capitals and industrial centres. Crucially, policy challenges and trade offs emerge. On one hand, is the need to address the long-standing issue of stranded and underutilised assets around power generation, transmission, and distribution and how these balance (or not) against additional and new capacity to enable sufficient, reliable and sustained electricity supply. On the other hand, is the challenge of ensuring that closing the access to electricity gap in Nigeria is done in a way that is just, fair, and equitable, with no part of society becoming worse-off or excluded