Elaboration and Experimental Characterization of New Low-loss Dielectric Composite Materials for Application in Dielectric Resonator Antennas

Abstract

Dielectric resonator antennas (DRAs) offer promising solutions for many advanced wireless communication systems due to their attractive features, including compact size, multiple feeding mechanisms, low loss, low cost, wide bandwidth, and high radiation efficiency. This thesis presents the design and investigation of several dielectric resonator antennas fabricated from binary composite materials consisting of epoxy resin (𝑅𝐸) and barium titanate (𝐵𝑎𝑇𝑖𝑂3). The first part is devoted to the characterization of the dielectric behavior of the binary composite. We studied the influence of barium titanate on the dielectric behavior of the binary composite with different volume fractions of epoxy resin (from 50% to 100% in steps of 5%), which were prepared at room temperature and under atmospheric pressure. The dielectric properties of composites were assessed using the time domain spectroscopy (TDS) technique to extract the dielectric properties of all samples. The experimentally obtained properties are suitable for meeting the practical requirements of manufacturing high-performance dielectric resonator antennas. The second part focuses on the design and study of dielectric resonator antennas using the dielectric properties of materials obtained experimentally. These antennas are designed, simulated, and optimized using the electromagnetic software Ansys HFSS. In total, four types of antennas are investigated. The first type of antennas is based on the effect of the dielectric properties on the performance parameters of cylindrical dielectric resonator antennas, using all the composite material samples. Three sets of antennas are obtained and classified according to the number of frequency bands: single-band, dual-band, and triple-band. For the second type of antennas, we studied the influence of compound structures on the performance parameters of dielectric resonator antennas. The structure consists of a combination of four dielectric resonator shapes: three identical rectangular joined with one cylindrical, all having the same height. A single sample containing 60% of 𝑅𝐸 and 40% of 𝐵𝑎𝑇𝑖𝑂3 was used. The proposed antenna gives a dual-band frequency, with one of the bands being wide. For the third type of antennas, we investigated the effect of multiple structures using two composite material samples on the performance parameters of the dielectric resonator antennas. The structure consists of four identical adjacent rectangular resonators, made from two samples: one with 60% 𝑅𝐸 and 40% of 𝐵𝑎𝑇𝑖𝑂3, and another with 50% of 𝑅𝐸 and 50% of 𝐵𝑎𝑇𝑖𝑂3. The suggested antenna provides three frequency bands. In the fourth type of antennas, we studied the effect of combining multiple dielectric resonator shapes (a hybrid structure), coupled through an aperture formed by two large rectangular slots and their offset positions. A composite material sample consisting of 60% of 𝑅𝐸 and 40% of 𝐵𝑎𝑇𝑖𝑂3 was used. The antenna offers an ultra-wideband with a relative bandwidth of 97% and two circularly polarized bands. The resulting antennas are suitable for use in frequency bands corresponding to centimeter wavelengths