686992 event 1766096978 1766097055 <![CDATA[Ph.D. Proposal Oral Exam - Sree Adinarayana Dasari]]>
Title:  Exploration Of Novel Materials For Highly Efficient Next Generation RF Systems

Committee:

Dr. Ghalichechian, Advisor

Dr. Ayazi, Chair

Dr. Tentzeris

]]> The objective of the proposed research is to explore applications of novel materials for next generation RF systems to achieve high efficiency, rapid reconfigurability, and low power consumption. Three works involving on-chip antenna, thin film permittivity measurements, and wireless power harvesting system are presented. On-chip antennas eliminate the lossy interconnects and parasitics arising from integrating the antenna with a chip. In harsh environments conditions in application spaces such as aerospace and automotive, reliability is a great concern for heterogenous integration. Therefore, to overcome these challenges, this work showcases an on-chip dielectric resonator antenna on silicon carbide substate (SiC) operating in the Ka-uplink band for high temperature applications. Vanadium dioxide is a phase change material that goes from an insulating state to a metallic state by application of stimuli such as heat. These films are used to create reconfigurable RF structures. The crystalline structure suggests anisotropy in the dielectric properties. Therefore, two structures are designed to be sensitive to in-plane and out-of-plane permittivity. An automated test setup was designed to measure the devices near the phase transition, enabling the extraction of temperature-dependent complex permittivity over a wide bandwidth covering 1–67 GHz. The extracted permittivity and loss tangent are modeled using sigmoid and exponential functions, respectively, to capture their nonlinear behavior at the phase transition and enable implementation in simulation tools. Future work on ambient wireless power harvesting is briefly discussed. An antenna in microwave band is fed to a resonant piezoelectric transformer to provide a large voltage gain to achieve a significant increase in RF-dc power conversion efficiency.

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