Tunable and energy-efficient filters are key components in modern wireless communication, where RF front-end systems must operate across multiple frequency bands while minimizing power consumption.

This thesis focuses on the design and fabrication of miniature, narrowband, tunable bandpass and bandstop filters based on magnetostatic waves (MSW) in yttrium iron garnet (YIG) waveguides. A zero-static-power magnetic bias circuit is used to tune the filter’s center frequency, but the compact size of the magnetic bias circuit imposes stringent limits on the YIG waveguide dimensions. To address this challenge, microfabricated YIG thin films with aluminum meander-line transducers were developed. These designs improve the resonator figure of merit, reduce insertion loss, and enhance coupling. Increasing the YIG thickness further improves skirt selectivity, lowers propagation loss, and increases power handling. By integrating wideband tunability with nonreciprocal behavior, a single device can replace multiple RF switches, filters, and isolators, simultaneously controlling passband selection and directional isolation. This integration simplifies RF front-end design by reducing the number of required components.

In parallel, this thesis introduces a high-frequency surface acoustic wave (SAW) platform using aluminum scandium nitride (AlScN) on 4H-silicon carbide (SiC). This material system combines high sound velocity, high thermal conductivity, and strong piezoelectric response. Furthermore, the acoustoelectric effect (AE) was harnessed to achieve nonreciprocal RF amplification. A proof-of-concept AE delay line was realized by integrating Sezawa-mode SAWs in AlScN/SiC with ion-implanted SiC, supporting future applications for energy efficient RF amplifiers.