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Description
All communications systems require band-limiting filters and antennas for proper operation. In space communications, strict requirements on size, weight, and power necessitate the use of low power, low loss components which are physically small and lightweight. Often times, higher frequencies are also desired in order to sustain higher data transfer rates. Circular polarization is a common need for space communications, as the atmosphere can unpredictably re-orient the polarization of a linearly polarized system. A need therefore exists for low loss, miniaturized high frequency filters and antennas for these applications. Moreover, the antenna must satisfy the circular polarization need. This thesis presents a study of dielectric resonator use for the design of a dielectric resonator filter and dielectric resonator antenna, both at Ku-band frequencies for satellite communications applications. Dielectric resonator filters can obtain very high quality factor (Q) responses due to their inherent low loss material, which is lucrative for communications systems, while dielectric resonator antennas can exhibit low loss and high radiation efficiency, but present a challenge in excitation for circular polarization from single feed designs. The filter designed in this research is a four element dielectric resonator filter operating at a center frequency of 13.029 GHz with a bandwidth of 89.5 MHz, and achieving a loaded Q of 145.58. The filter utilizes microstrip excitation of four dielectric resonators in the TE___ resonant mode in iris-coupled cavities mounted on a low loss substrate. An investigation of the substrate topology, parametric studies on the filter parameters, and filter tuning methodologies are presented. This thesis also presents a dielectric resonator antenna achieving right handed circular polarization centered at 12.935 GHz, with a 17.24% 3 dB axial ratio bandwidth. The antenna features a single feed design utilizing back-side microstrip excitation through novel bowtie cross slots, exciting the dielectric resonator in the HEM___ resonant mode. Parametric studies on the antenna parameters are presented and used to tune the final design. A prototype dielectric resonator antenna was fabricated and experimentally verified for impedance matching and radiation patterns showing reasonable agreement with the simulated data.
