Incorporating Directionality in Transversal-Resonator-Based Bandpass Filters With Tunable Transfer Function Characteristics

This paper introduces a detailed methodology for the realization of multi-functional transversal resonator-based non-reciprocal bandpass filters (NR-BPFs) that combine the functionality of a single-/multi-band BPF and an RF isolator. Directionality is achieved through spatiotemporal modulation (STM) whereas transfer function reconfigurability is obtained by only tuning the resonant frequency of its constituent resonators. A detailed design methodology to synthesize the response of transversal resonator-based STM arrays is introduced in this work for the first time, facilitating the synthesis of advanced RF filtering transfer functions based of transversal resonator arrays with incorporated directionality. The operating principles and scalability of the design method are demonstrated through the analysis of four distinct transversal resonator-based STM filtering topologies that facilitate the realization of high-order and highly-modular single-band and multi-band transfer functions with multiple levels of RF tuning including frequency tuning, bandwidth tuning, band controllability, and intrinsic switch-off capabilities. The concept has been validated at UHF band through the manufacturing and testing of four lumped-element NR-BPFs.