الفهرس 
Introduction to Finite Difference Time DomainOnly 14 pages are availabe for public view
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Abstract
The wireless communication systems had been grown with increasing applications
in wide range of electronic commerce, especially the antennas which took a great
interest in the field of wireless communications due to easy fabrications, low profile,
low power consuming, reduced size, multi-functions and multi-band for wireless
devices.
This thesis concentrates on major parts affecting the microstrip patch antennas
(MPAs) operation. In the first part, the mutual coupling effects between the elements
of microstrip patch antenna arrays (MPAAs) have a great interest and can affect the
performance of the microstrip antennas. first We design array antenna of two
elements with distance apart equals to λ0/2 on dielectric substrate FR4 with dielectric
constant 4.5 and height h=1.5mm to operate at resonance frequency f0=6.3 GHZ. The
mutual coupling between the elements of the array antenna can be measured by the
insertion loss, IL (dB) between the elements. Some techniques for reduction of the
mutual coupling between the elements of the MPAs were used before. Among these
techniques as we propose are the periodic structures of complementary Split Ring
Resonators (CSRRs) of Metamaterials (MTM) for reducing the mutual coupling
between the elements of microstrip antenna arrays. CSRR is firstly designed on a
dielectric substrate of FR4 with relative permittivity ɛr=4.5 and dielectric height
h=1.5 mm. They operate as Left Handed Materials (LHM) with negative permittivity
and permeability at the frequency of operation of the MPA (f0= 6.3 GHZ). Three
shapes of CSRR are proposed to reduce the mutual coupling effects between the
elements of the array antennas. The first shape is a single CSRR which is easily
etched in the ground plane of the array antenna and this can make isolation of 38 dB
under the original value of the conventional array antenna. The second shape is a
double CSRR and this can make isolation of 10 dB under the original value and the
[IV]
last shape is a triple CSRR which can give isolation of 14 dB under the original
values of the antenna. The gain and directivity are improved by about 1.1 dB due to
the suppression of the surface waves between the elements of MPAs. The feeding
method of the MPA is a 50Ω coaxial probe feed. This method of feeding is preferred
because of its advantage to give more guided waves under the patches and so the
mutual coupling is increased. The dimensions of the CSRR structures are selected
and modified to agree the MPA resonance frequency. For more verification, the
proposed antenna loaded with the CSRRs is fabricated and measured. The measured
data give good agreement with the simulation results.
In the second part of this thesis, the gain improvement of the MPA takes a great
interest. We propose a new MPA which designed on a dielectric substrate of Roger
4003C with relative permittivity 3.55 and thickness h= 0.813 mm to operate at
resonance frequency of 10 GHZ and has total gain 7 dB.
We suggest 2-D periodic structures of Complementary G-shape Split Ring
Resonator (CGSRR) and Separated Complementary G-shape Split Ring Resonators
by slots (SCGSRRs) of MTM for enhancing the gain and bandwidth of the MPA.
CGSRRs are designed on the same dielectric substrate of the MPA and can give
negative values of permittivity and permeability at the frequency of operation f0=
10GHZ. These periodic structures are loaded around the patch antenna to enhance the
gain of the antenna by about 2.5 dB over the original value of the conventional MPA
and the bandwidth increases from 350 MHZ to 510 MHZ. SCGSRRs are designed on
a dielectric substrate RT/duroid 5880 with dielectric constant equals to 2.2 and
thickness h= 1.575 mm and can be used as flat lenses over the MPA loaded with
CGSRRs. The total gain of the MPA will be improved by about 3.83 dB. The
proposed MPA loaded with CGSRRs are fabricated and measured. Good agreement
between the simulated results and measured data is achieved.
[V]
The finite difference time domain method is used in this thesis to analyze and
study the operation of the microstrip patch antenna. 3D simulation for Maxwell’s
equations is carried here with LIAO’s absorbing boundary conditions for the problem
space. The FDTD method is used to calculate the scattering parameters of the patch
antenna and visualize the EM waves through the patch. The calculated scattering
parameters from the FDTD equations are compared with the simulated results. Good
agreement between the calculated and simulated results is achieved.