الفهرس 
Accomplishment and Contribution
Defected Ground StructureOnly 14 pages are availabe for public view
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Abstract
Recently, vanous wireless communication services have been
available, which use many frequency spectrum allocations, e.g., WIMAX
(Worldwide Inter operability Microwave Access), BWA (Broadband
Wireless Access) and WlFI (Wireless Fidelity). For these applications,
microstrip antennas are preferred because of their advantages such as low
profile, light weight and easy design with multi frequency bands.
However, a common disadvantage of microstrip antennas is surface
wave, which is excited when ever the substrate has dielectric permittivity
greater than one. To suppress surface waves. several studies are
conducted including defected ground structure (~OS).
DOS is realized by etching the ground plane with a certain lattice
shape which disturbs the current distribution of the antenna. Many shapes
of DOS have been studied such as concentric ring, circle, spiral,
dumbbells, elliptical and U, V slots. DOS gives an extra degree of freedom
111 microwave circuit design and can be used for a wide range of
applications. In this thesis, first we designed, fabricated and measured a
proposed compact microstrip antenna with two new defected ground
structures (DOS). This antenna was simulated by using a suitable readymade
software package CZeland-1E3D) to investigate this design. then
fabricated by using thin film and photo-lithographic technique. Finally.
proposed compact microstrip antenna with different proposed DOS is
measured by using vector network analyzer. Good agreements were
found between measured and simulated results. Second, we suggested an equivalent circuit and equations formula for coupling coefficients for the
compact microstrip antenna with proposed DOSs. Third, we got a
negative value of equivalent circuit DOS lumped elements which is
perfectly allowed for the circuit modeling. This is similar to a lumpedelement
inverter with negative elements in which the negative elements
physically may be absorbed by the adjacent reactance components (Meta
Materials).