Multi-functional use of cylindrical dielectric resonator for microwave circuits and antenna applications.

摘要

The main objective of this PhD dissertation is to investigate the ability of utilizing a single cylindrical dielectric resonator in realizing multi-functional devices to be used for filtering, oscillating as well as radiating purposes by exciting multi-independent modes simultaneously. The complete work is devoted in three main categories or contributions. First contribution is mainly working on the use of dielectric resonators in multi-function realizations. A design of dielectric resonator antenna in a polarization filtering cavity for dual function applications is studied where a cylindrical dielectric resonator is enclosed by a hypothetical resonant cavity that acts as a shielding for the resonating mode while transparent for the radiating mode. A possible application of this device is a receiving antenna at the frequency of the radiating mode and can incorporate a local oscillator operating at the resonant frequency of the resonating mode. Moreover, a design of dielectric resonator antenna for GPS and WLAN applications is introduced where both a broadside circularly-polarized antenna and an omni-directional antenna are obtained simultaneously by exciting two independent modes. Since the previous work dealt with the dual use of a dielectric resonator, a new challenge was to go for the triplet functioning. Therefore, part of the work is devoted to study the triple mode operation using a single dielectric resonator for filtering and radiating purposes. The design utilized the dielectric resonator simultaneously as a dual band radiator and as a filter operating for the lower frequency radiating mode band. Traditionally, mechanical direction finding antennas were built with either loop or dipole antenna elements. In radar applications, spiral and horn antennas have been used for the precision direction finding. The second contribution of this dissertation work is studying the use of dielectric resonator antennas in the design of direction finding systems. The direction finding operation is achieved by comparing the received signal with the two generated dielectric resonator antenna patterns. Those patterns are obtained by exciting certain mode through two different ports, once out of phase and once in phase, to produce a broadside type and a monopole type of radiation patterns. Because of its small size, the DRA can be used for an approximate hand-held target tracking, but it could also be used as a feed for reflector antenna for an accurate direction finding in point-to-point applications. The intended application of this antenna is to track a position of a source of radiation.;Since the previous parts of the dissertation work are mainly all about the implementation of multi-functional devices with a single dielectric resonator, it was of interest to investigate the use of higher order modes and explore the ability of incorporating such modes in the implementation of new microwave devices. Cylindrical dielectric resonators sustain high-Q electromagnetic modes called "Whispering Gallery Modes" (WGMs). Such high order modes have attracted the attention due to their intensive applications in quantum electrodynamics (QEM), photonics, and telecommunications. The third contribution of this dissertation is mainly studying the ability to excite a WGM transverse magnetic type of mode and use it for the realization of an equally distributed power dividers to be used later in the feeding of antenna array. An X-band WGM excited dielectric resonator enclosed by a cylindrical cavity was designed built and measured to perform as a 5-way uniformly distributed power divider. The excitation of the transverse magnetic WGH3,1,1 mode was carried out by using microstrip feeding technology integrated with electric probe coupling technique or magnetic slot coupling for different design realizations.