الفهرس 
Chapter 2: BLC Literature ReviewOnly 14 pages are availabe for public view
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Abstract
For decades, engineers have been searching for ways to reduce the size of electronic circuits while maintaining the efficiency and effectiveness of the circuits. At low frequencies of the microwave band, the size of the conventional transmission line becomes larger. Metamaterials are synthetic materials engineered to have a property that is not found in nature. They gain their properties not from their composition, but from their designed structures, and it could be used to reduce the sizes of the electronic components.
In this thesis, miniaturization of the Branch-Line Couplers BLCs are investigated. Firstly, two proposed structures of the BLC based on classical methods for minimizing the circuit area of the BLC are designed and simulated using CST full wave simulator.
Later, a new proposed compact 3dB Branch-Line Coupler (BLC) is designed and implemented, based on coupled line D-CRLH Metamaterial. The size of the proposed BLC occupies only 52 % of the area of the conventional design to operate at 1.8 GHz. The structure with optimum parameters is fabricated and the comparison between the measured and the simulation results shows very good agreement.
High Temperature Superconductor HTS is used rather than a copper microstrip conductor. The CST full wave EM simulator has been used to simulate the proposed BLCs. All the parameters of this design are enhanced compared to the BLC in copper conductor.
Moreover, the tunable frequency BLC is designed using a thin film layer of BST ferroelectric material, the layer is sandwiched between the LAO substrate and HTS microstrip line, The dielectric properties of the ferroelectric thin film, and the thickness of the ferroelectric film, play a fundamental role in the frequency or phase tunability and the overall insertion loss of the circuit. The response shows a variation of electromagnetic characteristics with the applied electric field, ferroelectric thickness and the operating temperature.