Elizabeth J. Podlaha-Murphy, Edwin Marengo
Date of Award
Doctor of Philosophy
Department or Academic Unit
College of Engineering, Department of Electrical and Computer Engineering
electrical engineering, bandpass filters, ferrite films, Magnetic antennas, magneto-dielectric materials, phase shifters, self-biased magnetic films
Electrical and Computer Engineering
In this dissertation we have studied planar microstrip antennas and RF filters miniaturization and performance improvement with novel substrate, superstrate and hybrid substrate/superstrate structure. In particular, we have compared dielectric materials and magneto-dielectric materials, and used the magneto-dielectric materials to counteract the narrowing of bandwidth, and the impedance mismatch due to the use of high permittivity materials as antenna substrates. However, from materials perspective, it has been challenging to achieve self-biased magnetic materials for antenna substrate applications at frequencies>600 MHz range due to the well known Snoek limit.
Magnetic thin films provide a unique opportunity for achieving self-biased magnetic patch antenna substrates with relative permeability >1, at frequencies > 1 GHz due to the significantly extended Snoek limit. Spin spray process providing us those thin films with high permeability and ferromagnetic resonance (FMR) frequency in the GHz range which are suitable for RF application. We performed many different measurements on NiCo and NiZn ferrite films in regards to their dispersion characteristics, thermal stability, magnetization and optimal thicknesses.
The development of novel magnetic antennas, filters and phase shifters are the application employed to prove these new materials. Both calculated and measured results have shown that how utilizing ferrite films can help to improve a variety of different RF devices with their performances by frequency down shifting (miniaturization), bandwidth enhancement, directivity or gain improvement.
Yang, Guomin, "Tunable miniaturized RF devices on magneto-dielectric substrates with enhanced performance" (2010). Electrical Engineering Dissertations. Paper 29. http://hdl.handle.net/2047/d20000899
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