Acoustic-Wave-Resonator-Based Bandpass Filters With Multiconfigurable and Continuously Tunable Transfer Function Capabilities

New architectures for multiconfigurable and continuously tunable acoustic-wave-resonator (AWR)-based bandpass filters (BPFs) are presented. They are based on the cascaded multiresonant acoustic-wave-lumped-element resonators (AWLRs) that are shaped by a high-quality factor (Q) resonating module (R_Hi), a tunable low Q-factor lumped element (LE) resonator (R_i), a tunable impedance inverter (Z_Ei), and a frequency-tunable low-Q LE resonator (R_L). R_Hi comprises a static one-port-type AWR in parallel with R_i and together with a tunable impedance inverter and R_L, it creates a quasi-elliptic response that is shaped by one pole and two transmission zeros (TZs). As such, by cascading N multiresonant modules, quasi-elliptic transfer functions with enhanced fractional bandwidth (FBW, i.e., greater than the electromechanical coefficient k_t²) shaped by N poles and 2N TZs can be created. A new tuning mechanism facilitating continuous center frequency (f_cen) of an AWR-based filter is demonstrated for the first time alongside a concept to facilitate additional tuning capabilities including FBW tuning, an all-pass, and an all-reject response. The operating principles of the tunable AWLR BPFs concept were experimentally validated at the L-band through the design and testing of: 1) a single-stage AWLR-based BPF; 2) a two-stage AWLR-based BPF; and 3) a three-stage AWLR that exhibits BPF responses with continuous f_cen and FBW tuning alongside all-pass and all-reject reconfigurability. All of the tuning states exhibit min-insertion loss (IL) ranging from 3.3 to 6.9 dB, corresponding to high effective Qs between 2600 and 6400.