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Title: Miniaturisation of ultra-wideband filters using e-shape microstrip structure
Author: Hammed, Raaed Thaaban
ISNI:       0000 0004 2736 4023
Awarding Body: University of Essex
Current Institution: University of Essex
Date of Award: 2012
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Due to a high demand for high-speed wireless connectivity applications, the ultra- wide-band (UWB) technology is proposed, having frequency limits of 3.1 GHz to 10.6 GHz and a power transmission of -41 dBm. Since UWB systems are extremely low power, the miniaturization ofUWB systems is desirable. Normal'ry.ttre front-end passive components part (antenna, bandpass filter, and balun circuit) of the UWB systems occupy a large space. Therefore, the research and development of miniaturised UWB bandpass filters with a high performance is the subject of this thesis. Based on its attractive features; compactness and low production cost, the E-shape microstrip structure with shorted and open middle stubs is analysed and their equivalent circuits, for the first time, are presented to show their responses. Using the equivalent circuit of the E-shape microstrip structure with shorted middle stub and considering that the input/output ports are directly connected to the structure, several second-order narrow and UWB bandpass filters are researched and developed. The proposed equivalent circuit of the miniaturised E-shape micro strip structure is then generalised for the case of E-shape microstrip structures directly cascaded through very short microstrip line. Several highly compact high-order UWB bandpass filters are developed including third, fifth, and seventh-order bandpass filters. These filters are realized with one transmission zero in the upper stop band attenuation. ill order to increase the lower stop band attenuation, a new design technique generating a transmission zero in the lower stop band too is introduced. This has led to a new generation of miniaturised UWB bandpass filters. These filters are realised using two lower order bandpass filters employing E-shape microstrip structure, coupled through a top-layer providing A./4 tight coupling structure. All the simulated examples are fabricated and their responses from measurement, simulation and equivalent circuit are found to be in agreement as discussed in the thesis. , Next, the development of notched attenuated band in the UWB pass band is studied. As a result, a novel design technique to generate single and multiple notched bands in the miniaturised UWB bandpass filters employing E-shape microstrip structures is proposed. This is achieved by using IJ4 short-circuited micro strip resq"na or or the E-shape microstrip structure capacitively coupled to the main filter structure. Generally, the measured results of the design examples are in excellent agreement with the theoretical results. Reasons for any discrepancies are elaborated and discussed. Finally, the realisation of the balance-unbalance (balun) circuit required in UWB systems to connect the passive to active front-end is investigated. Based on a traditional Marchand balun circuit, a technique to design a miniaturised differential ·coupler for UWB bandpass application is presented. In this technique, the Marchand balun circuit is realised in a double layer structure in order to obtain tight coupling for broadband balun. The simulated results for a balun are supported by the practical realisation. The results from measurement and simulation are generally in good agreement.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available