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Abstract
In microwave applications where performance requirements dictate a high quality implementation, dielectric resonator filters are a welcome alternative to waveguide filters. Dielectric resonators can achieve unloaded quality factors comparable to waveguide resonators, but at a substantially lower weight and smaller volume. Dielectric resonators are also compatible with a micro strip environment, which eliminates the need for micro strip to waveguide adapters. Therefore, Dielectric resonators are primary components in modem microwave circuits, especially when a substantial reduction in size is required. This thesis presents the analysis of end coupling between micro strip lines and cylindrical dielectric resonator, the most popular shape, in a microwave integrated-circuit environment. The analysis is performed using the finite-difference time-domain method. In order to simulate open structures, an absorbing boundary condition is needed to truncate the computational domain properly. The perfectly matched layer technique is successfully applied. It is very efficient technique that produces negligible reflections when applied to unbounded problems. It is shown that the end coupling will excite the hybrid electromagnetic modes with respect to the axis of rotation. The coupling is accomplished through the magnetic field (magnetic coupling), where the magnetic field lines of the micro strip line link with those of the resonator. As a consequence of this, the end of the micro strip line is short-circuited in order to maximize the magnetic coupling. Numerical results of the insertion loss characteristic are obtained in case of short-, and open-circuited end of the micro strip line. The resonant frequencies of the hybrid modes excited in the frequency range of interest are obtained and hence the corresponding electric and magnetic field distributions arc drawn to assign an appropriate name and set of mode indices. The effect of the separation distance between the end of the micro strip line and the dielectric resonator on the loaded quality factor, as well as the coupling coefficient between them is studied. Finally, a comparison between micro strip half-wave filter and dielectric resonator filter reveals the advantage of using the dielectric resonators in microwave filters. Also, a comparison between end coupling and edge coupling is investigated.