Radio frequency devices using thin-film magnetic and magnetoelectric composites [electronic resource]
Keywords: Electrical Engineering.

One vision of the future predicts an immense, universal web connecting sensors on humans, phones, cars, and homes, among other objects. The sensors in this web will perpetually measure, store, and broadcast the status of the systems they are monitoring. In order for this vision of the Internet of Everything to materialize, these sensors must communicate wirelessly and share the limited communication channels in the wireless spectrum. One solution for this wireless communication is to utilize tunable transceivers (components that transmit and receive wireless signals), which can tune their operation from one channel frequency to another depending on the availability of spectrum "white spaces." This research addresses this need for broadband spectrum mobility by developing radio frequency (RF) integrated magnetic and magnetoelectric tunable transceiver components for use in wireless circuit modules. This research pushes the boundaries of magnetic high frequency operation in order to address the needs of current mobile technologies. An RF integrated circuit sets its mobile communication frequency most often by using an inductor-capacitor (LC) tank. Therefore, spectrum mobility can be achieved by means of integrating tunable inductors or resonators. The performance of an inductor directly relates to the permeability of its surrounding material. This work exploits this key property to create RF magnetic-core inductors and tunable coplanar waveguide resonators. The first part of this dissertation explores the methods by which the operating frequency of integrated magnetic-core inductors can be increased to reach suitable bands for mobile wireless technologies (1-5 GHz). Power amplifiers for mobile applications require inductors with small form factors, high quality factors, and high operating frequency in the single-digit GHz range. This work demonstrates the best performance at high frequencies for an integrated magnetic core inductor with a 1 nH inductance and peak quality factor of 4 at 3 GHz. Such compact inductors show potential for efficiently meeting the need of mobile electronics in the future. The second part of this research demonstrates the first fully-integrated, voltage-tunable RF coplanar waveguide resonator to allow dynamic access of the electromagnetic communication spectrum. The waveguide changes its resonance frequency through voltage-controlled tuning of the magnetic material's permeability. Often, magnetic materials exhibit magnetostriction, a property that enables their magnetization to respond to physical strain on the film. Similarly, piezoelectric materials will strain under an applied voltage. This work combines two such materials into a magnetoelectric composite, which couples an applied voltage to a change in magnetization and its associated permeability. These integrated RF tunable resonators experimentally showed resonance frequency tunability of up to 10 MHz per applied electric field of 1 V/um, representing a significant step towards future dynamic spectrum access. Simulations suggest that, with further optimization, such magnetoelectric resonators can achieve up to two orders of magnitude shift in the resonance frequency. Therefore, this dissertation research embodies the first step toward leading the way in hardware for an Internet of Everything.