الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
Multi-beam antenna systems operating in the millimeter-wave frequency
bands have attracted a lot of research interest with the demanding system
requirements for the fifth-generation (5G) wireless communications and
the severe spectrum shortage at conventional cellular frequencies.
This thesis introduces a study of design and analysis of multi-beam
antennas based on graphene. A single element and multiple element are
designed. The radiation characteristics of a wideband Magneto-electric
antennas based on graphene material are investigated. The antenna
introduces wideband impedance matching from 14 GHz to 32 GHz with
circular polarization of 61.2 %. The reconfigurable conductivity of
graphene patches controls the operating bandwidth of the antenna by
changing the graphene chemical potential. Octagonal array comprises of 8-
similar elements are constructed to produce electronic beam switching in
various directions. Single beam, dual-beams, and omni-directional beam is
achieved by controlling the graphene conductivity of single, two, and all
the ME-elements in the array. Electronic beam switching is achieved by
electronically control the biasing of the graphene ME-element in the array.
Dual-beams in different directions are designed with biasing the selected
two elements with μc=2 eV and with μc=0 eV for the other elements. Omnidirectional
pattern in x-y plane is achieved by activating all the array
elements with μc=2 eV.
The effect of curvature on the radiation characterstics of CP-ME-dipole
antenna with wideband characterstics is investigated. The effect of
graphene reconfigurable conductivity on the ME-dipole performance is
investigated. The impedance bandwidth is increased by increasing the chemical potential from10 GHz at μc=0.25 eV to 16.9 GHz at μc= 2 eV.
The effect of ME-dipole curvature is investigated on both cylinderical and
spherical surfaces.
A wideband graphene-based ME-antenna is optimized by using SIW
technology for using in PCB. The single SIW ME-dipole is designed and
A 2 × 2 ME-dipole subarray is designed to increase the CP bandwidth to
88 % and peak gain of 8.3 dBi. Different array arrangements based on
reconfigurable characteristics of the graphene have been investigated. In
the triangular prism array, a single beam is turned in three different
directions at 60°, 180°, and 330° when the graphene in the corresponding
face is tuned in and the graphene in the other faces is tuned out. By biasing
graphene in each face sequentially, the beam is turned in six directions
separated by 60° using a hexagonal prism array arrangement.
Terahertz (THz) technology, in recent few years, gained the interest of
researchers because of its increasing number of applications in earth and
space science, spectroscopy, communication, medical, defense, imaging,
sensing, and material characterization. An electronic beam switching using
graphene patch antenna with reconfigurable characteristics for end-fire
radiation for THz applications has been investigated. The graphene patches
are divided into two groups, each is operating to the directors in Yagi-Uda
antenna. The graphene conductivity can be controlled via changing the
voltages applied onto the patches. The copper patch at the antenna center
is a driven element whose shape is triangle. A graphene terahertz antenna
of pentagonal patch shape is also proposed. The beam is switched in four
different directions.