UCLA

Magnetic materials offer a unique combination of properties such as non-reciprocity, highpermeability, broad tunability, strong frequency dispersion, and nonlinearity. These characteristics made them uniquely valuable in various linear RF devices such as inductors, circulators, isolators, phase shifters, filters, and antennas. Nonlinear RF magnetic devices such as frequency selective limiters and signal-to-noise enhancers have also received significant attention lately. Leveraging on the recent advances in the fabrication of thin film and thick film magnetic materials, many traditional RF magnetic devices can now be integrated on-chip, which opens up ways to supply high-quality factor passives on-chip that are lacking in existing semiconductor-based integrated circuit (IC) process. This dissertation delves into the modeling and design of RF magnetic devices through equivalent circuit models derived from micromagnetic theory. These models provide concise and intuitive representations of the linear and nonlinear spin dynamics and spin wave propagations within RF magnetic materials.

The research demonstrates the efficacy of these equivalent circuit models by applying them to various RF devices, including ferrite-loaded strip lines, small antennas, andfrequency-selective limiters (FSLs). These models have shown high accuracy in predicting device performance, aligning well with full-wave simulations and empirical data. A significant focus is placed on millimeter-wave resonators and filters using M-type barium hexagonal ferrite, with operational frequencies reaching up to 45 GHz. These devices are optimized for better energy coupling and exhibit promising potential for millimeter-wave applications. This dissertation significantly advances the understanding and application of RF magnetic devices, laying a robust foundation for future innovations.