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Title: Artificial materials for microwave applications
Author: Bukhari, Syed S.
ISNI:       0000 0004 7971 0100
Awarding Body: Loughborough University
Current Institution: Loughborough University
Date of Award: 2017
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This thesis has focussed on the properties and manufacturing techniques of artificial RF materials. These artificial materials can be divided into two types depending on the whether their individual unit cell is resonant or non-resonant. Both these types have been discussed. It has been shown that the efficiency and bandwidth of a patch antenna using a flexible 3D printed substrate can be improved by using composite materials as heterogeneous substrates. Composite materials with a large range of relative permittivity values were manufactured by combing 3D printing with commercial laminates. An equation to design such composite materials has been presented. The engineering tolerance and repeatability of 3D printing as a manufacturing process to fabricate 'on demand' dielectrics has been presented. For materials with resonant unit cells, 2D materials known as metasurfaces have been considered. Metasurfaces presented in this thesis have been developed by close coupling of two Babinet's complements. It has been shown that the unit cell of a dipole-slot metasurface can be miniaturized by adding an additional layer of dipoles, making a dipole-slot-dipole metasurface. The response of both these metasurfaces was explained with a qualitative circuit model. Miniaturization has been achieved by using square loops as the building blocks for a Babinet complementary metasurface. A λ/17 structure was designed, fabricated and measured by using square loops; however the two layers should be shifted with respect to each other toachieve strong inter-layer coupling, thus miniaturization. The width-optimization of a dipole-slot metasurface has been achieved by maximising the coupling co-efficient. The expression for optimum length to width ratio of a dipole-slot metasurface has been derived. A generalised analytical circuit model, for any Babinet complementary metasurface, has been derived based on integral equations. This analytical model has been used to explain the pass band and compact nature of these metasurfaces. The comparison between this analytical model and full wave analysis showed excellent agreement with high numerical accuracy.
Supervisor: Not available Sponsor: Loughborough University
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Mechanical Engineering not elsewhere classified ; Artificial materials ; Metamaterials ; Metasurfaces ; 3D printing ; Microwaves