Multiconfigurable Acoustic-Wave-Lumped-Resonator (AWLR)-Based Bandpass-to-Bandstop Filters With Continuously Tunable Characteristics

Multiconfigurable and continuously tunable acoustic-wave resonator (AWR)-based filters exhibiting bandpass (BP) and bandstop (BS) responses with continuously tunable center frequency ( ${f} _{\mathrm {cen}}$ ) and bandwidth (BW) alongside an all-pass (AP) and an all-stop (AS) mode of operation are reported in this work for the first time. They are based on multiresonant, multiconfigurable acoustic-wave-lumped-resonator stages. Each stage comprises one high-Q surface acoustic wave (SAW) resonator and three low-Q lumped element (LE) resonators and simultaneously supports: 1) a BP mode with tunable ${f} _{\mathrm {cen}}$ and BW, shaped by one pole and two transmission zeros (TZs); 2) a BS mode with tunable ${f} _{\mathrm {cen}}$ and BW, shaped by one TZ and two reflection zeros (RZs); 3) an AP state; and 4) an AS state. By cascading N acoustic-wave-lumped-element resonator (AWLR) stages, a highly selective quasi-elliptic BP transfer function (TF) with N poles and $2~{N}$ TZs, and a BS TF with N TZs and $2~{N}$ RZs can be created having fractional BWs (FBWs) greater than the electromechanical coupling coefficient ( ${k} _{t}^{2}$ ) of the AWR. A novel switchless tuning mechanism is introduced to enable BP-to-BS reconfigurability without the need for RF switches for the first time. The operating principles are demonstrated through various synthesized coupling-matrix (CM) and circuit-simulated design examples. This concept is experimentally validated at 916.4 MHz through single-, two-, and three-stage prototypes, demonstrating continuous ${f} _{\mathrm {cen}}$ and FBW tuning with BP/BS/AP/AS reconfigurability. The filters exhibit FBW between 0.3 and $1.78~{k} _{t}^{2}$ , and insertion loss (IL) ranging from 0.9 to 5.8 dB, corresponding to effective Q-factors ( ${Q} _{\mathrm {\mathrm { eff}}}$ ) between 1900 and 5200.