Polarization-diversity Dielectric Resonator Antennas for Wireless Communications

Today, wireless communications have played an important role in both business and social activities. In wireless systems, antennas are very important because they directly affect signal transmissions and receptions. Recently, dielectric resonator (DR) antennas (DRAs) have been investigated extensively because of a number of advantages such as their small size, low loss, low cost, and ease of excitation.In mobile communications, a transmitted wireless signal will normally travel to the receiver along different paths, leading to different wave components at the receiver. As a result, received signals have amplitude and phase fluctuations, which is known as fading. Fading is an inevitable problem in mobile communications. A common technique to tackle it is to deploy diversity antenna systems. Diversity antenna systems can improve the channel performance and, thus, increase the quality of received signals. In this project, new polarization-diversity antennas will be designed using DRAs.Most of the polarization-diversity DRAs are excited in their broadside radiation modes, and only a couple of designs can provide omnidirectional field patterns. Those omnidirectional designs, however, make use of monopole-antenna modes instead of DR modes, causing inconvenience in matching the antennas. In this project, fundamental TM DR modes will be used to design omnidirectional polarization-diversity DRAs for the first time. Novel dual-polarized designs with omnidirectional/broadside and omnidirectional/ omnidirectional field patterns for their two ports will be given. Engineering formulas that determine DR dimensions for the new dual-polarized DRAs will be obtained. Since TM DR modes are used, matching can be achieved easily by simply varying the length of the excitation probe.All reported polarization-diversity DRAs have been limited to single-band designs. In this project, dual-band dual-polarized DRAs will be studied for the first time to meet the need of modern wireless systems. Also, since circularly polarized (CP) systems are extensively used in wireless communications, novel full-CP dual-polarized DRAs that have CP fields for both ports will be investigated.Thus far, only one three-port polarization-diversity DRA has been reported, and no attempt has even been made to investigate any four-port designs. In this project, both three- and four-port polarization-diversity DRAs will also be covered to provide more choices for engineers.Ansoft HFSS will be used to simulate the various polarization-diversity DRAs, and measurements will be carried out to verify the simulations. Design guidelines will be provided to facilitate designs of the polarization-diversity DRAs.