Date of Award
Open Access Dissertation
College of Engineering and Computing
The wireless communication market has been ever-growing in the recent decades. Radios with high performance and capabilities to support wireless connections are increasingly demanded. Recent developments in wireless communications targeting ubiquitous connections have resulted in ever more complex system structures for supporting multiple frequency bands and standards. Reconfigurable and tunable RF/microwave technologies have the potential to significantly simplify the systems. The main objective of this dissertation is to develop tunable technologies and design concepts, and propose a new design methodology to implement dually electrically tunable microwave components by integrating both selectively patterned ferromagnetic and ferroelectric materials.
The first part of the dissertation demonstrates the concept and topology of selectively patterned ferromagnetic (Permalloy) thin film enabled electrical tunability. The properties of Permalloy are demonstrated in details, and electrically tuning mechanism and topology are introduced and analyzed with both magnetic simulation and measurement results. By integrating selectively patterned Permalloy thin film to the coplanar waveguide transmission line, electrically tunable microwave transmission line is achieved. The inductance density of tunable transmission line can be electrically tuned by dc current, and the feasibility of Permalloy enabled electrical tunability is proved. To further validate the efficacy and utilize the topology to design tunable microwave components, tunable inductors and a tunable bandpass filter are designed and fabricated. For the tunable inductors, a planar spiral inductor and a 3-D solenoid inductor are implemented. Permalloy thin film is integrated with inductors to enable the tunability, and more than 10% inductance tunability has been achieved. Design principle of the tunable bandpass filter is then analyzed and demonstrated, and by integrating Permalloy thin film, the center frequency can be continuously tuned by dc current.
Based on the topology of Permalloy enabled electrical tunability, the second part of the dissertation proposes and demonstrates the methodology of ferromagnetic (Permalloy) and ferroelectric (PZT) enabled dual tunability for electrically tunable microwave applications. The tunable microwave components have both inductive and capacitive tunability by simultaneously integrating Permalloy and PZT thin films. To validate the efficacy and prove the concept, two dually electrically tunable phase shifters are implemented, including a slow wave transmission line phase shifter and a 3-D lumped-element phase shifter, and the performance can be tuned by applying dc current and/or dc voltage. Compared with planar transmission line phase shifter, 3-D structure has significant higher tuning efficiency and more compact size, and thus the maximal length normalized phase tunability has reached to 210o/cm. The dual tunability enabled by Permalloy and PZT not only improves the design flexibility and electrical tuning range, but also, more importantly, realizes the capability of characteristic impedance retaining, by which when microwave components are tuned, the characteristic impedance can be kept constant. This design concept and methodology can be further developed and applied to implement other tunable microwave components and circuits to realize tunable communication systems.
Wang, T.(2017). Integrating Nano-Patterned Ferromagnetic and Ferroelectric Materials For Smart Tunable Microwave Applications. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/4448