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Title: Novel design and measurement methodologies of millimeter wave smart antennas
Author: Ahmad, Ghulam
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2018
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Next generation wireless communication systems are expected to support unprecedented extremely high data transfer rates. This objective requires wider bandwidths which are presently only available at the millimeter waves (mm-waves) spectrum (30-300 GHz). Due to stringent propagation impairments, mm-waves mainly rely on the line of sight communication links which require high gain and wide angle beamsteeering smart antennas to maintain their performance. Owing to the complexity and losses in array beamformers, the realization of a high gain wide angle electronic beamsteering antenna solution at mm-waves becomes a key challenge. This research provides a potentially competing novel high gain electronic beamsteering antenna solution for mm-waves in the form of a phase quantized smart reflectarray consisting of high performance reconfigurable unit cells. Novel contributions of this research are: (a) Analysis of mm-wave reflectarray unit cells including the effects of fringing fields, surface waves, finite metal conductivity and metal surface roughness. (b) New measurement techniques for mm-wave reflectarray unit cells to ease the alignment, orientation, and DC biasing issues. (c) Characterization of PIN diodes at 10 GHz and 60 GHz for their ON/OFF state models extraction from measurements. (d) Design of three state implicit phase shifter reflectarray unit cell at 60 GHz, reduction in its DC bias lines, and an optimization technique to improve polarization purity of a multi-state reconfigurable unit cell. (e) A fast algorithm to prepare the electromagnetic simulation model of large reflectarrays. (f) Conception and measurement based validation of phase quantized reflecarrays and their performance matrix. (g) Conception and measurement based analytical solution of low DC power consuming smart reflectarrays. The resulting solution is agile, simple to implement, do not necessarily require multiple RF chains, enables wide angle electronic beamsteering (+-78 degree), is scalable for any gain/frequency requirements, can be made foldable for smaller satellite platforms, is very reliable, and consumes low DC power. This smart reflectarray platform can implement any phase only synthesis technique for radiation pattern control including single/multiple pencil beams, contoured beams, and their scanning over wider angles. Findings of this research would potentially benefit next generation terrestrial/air/space communication systems and radars.
Supervisor: Brown, Tim ; Underwood, Craig ; Loh, Tian H. Sponsor: Surrey Space Centre (SSC) ; National Physical Laboratory (NPL)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral