الفهرس 
Time-modulated linear arraysOnly 14 pages are availabe for public view
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Abstract
This thesis introduces the synthesis of linear and planer arrays using practical
elements. Full-wave simulations in frequency and time domain are considered. It is
focused on studying the shaped patterns synthesis in time-modulated antenna arrays
(TMAA) based on the sideband radiation. Shaped beam patterns can be realized by only
controlling the switch-on time sequences of the TMAAs. It introduces the theory of
TMAAs and the power losses associated to sideband radiation. Many examples are
considered to investigate the exploration of the technique including binomial,
Chebyshev, Taylor, uniform, and sum-difference linear arrays. A method based on
particle swarm optimization (PSO) technique to integrate the failed-elements detection
and the correction of the damaged patterns of TMLA is investigated. PSO technique is
an artificial intelligence (AI) technique that can be used to find approximate solutions
to extremely difficult for impossible numeric maximization and minimization problems.
The efficiency of the PSO technique in element failure detection and the corresponding
distorted pattern correction is validated using a Chebychev TMLA of 32 elements with
SLL= -35 dB. The pattern correction is achieved via recalculating the timing sequence
of the non-fault elements of the array using PSO technique. Different numerical
examples of failed-elements detection in different positions are investigated. An
approach for the synthesis of desired patterns taking into account practical elements
models is introduced. The approach is based on the combination of the PSO technique
and frequency domain full-wave analysis carried out in the method of moments, and
time domain full-wave analysis in finite integral method. Three examples are designed.
In the first example, a design of 4D parabolic 16-dipole elements TMAA linear array
with the effects of the mutual coupling between the elements. MoM is used to simulate
the array response and is compared with the TMLA of isotropic elements. Several
switching time sequences are investigated for the 4D parabolic array to radiate multiplebeams
in different directions. In the second example an investigation to the radiation
characteristics of plasma based ME-dipole antenna with circular polarization for 5G
applications is considered. TMAAs are constructed by connecting the elements with RF-switches with specific timing sequence for beam shaping applications. Different
shapes are designed according to predetermined requirements of gain, beamwidth, and
SLL. Planar array consists of 64- elements arranged in an 8×8 arrangement connected
with switches for time-modulation is proposed. A sequential arrangement of 2×2
elements with designed time switching is introduced for circular polarization. In the
third example, the employment of time-modulation technique in beam steering and
beam-shaping applications using linear SIW-DRA array of 16 SIW-DRA elements
spaced by 0.45λ is investigated. It is compact in size and introduces good beam forming
capabilities. Analytical solution and the PSO are used to estimate the on-time sequences
of the linear array for 1st-harmonic component. Beam-steering and multi-beam radiation
are obtained. Synthesis approach based on the combination of PSO and FIT technique
has been successfully used to optimize a time-modulated planar array antenna. 8×8 MEdipole
array is designed for 5G mobile applications. The time sequences are optimized
by the PSO technique and the patterns at the fundamental and sidebands frequencies are
all synthesized by using FIT. Different beam shaping constrains are investigated such
as uniform, Chebyshev, and Taylor arrays are designed. The main objective is
controlling the SLL of the array in single plane, two planes and all planes. Finally,
conclusion remarks and future works are introduced.