Acoustic Wave Resonator-Based Bandpass Filters With Continuously Tunable Fractional Bandwidth

Abstract

A new class of acoustic-wave resonator-based bandpass filters (BPFs) with continuously tunable fractional bandwidth (FBW) are presented. They are based on cascaded multi-resonant stages of hybridly-integrated surface acoustic wave (SAW) resonators with lumped element (LE) components. Each stage comprises one SAW resonator and one or more LE resonators that contribute to the overall transfer function to one pole and two transmission zeros (TZs). As such highly-selective quasi-elliptic transfer functions with N poles, 2N TZs and enhanced FBW can be created for two series and N-2 parallel stages. It is shown that by reconfiguring the resonant frequency of the LE resonators, continuously-tunable FBWs can be obtained. The operating principles of the multi-stage concept are demonstrated through design examples of multi-stage prototypes. The concept has been validated at 916.6 MHz through a fourpole/eight-TZ BPF with tunable BW between 0.63-1.32 MHz (i.e., FBW=0.57 -1.32kt 2 ), minimum in-band insertion loss (IL) 3.9-2.3 dB (Qeff =7700-6000) and out-of-band isolation > 27 dB. Index Terms-Acoustic wave resonator (AWR), high quality factor (Q), tunable bandpass filter (BPF), kt 2 -enhancement.

Resonator-Loaded Waveguide Notch Filters with Broad Tuning Range and Additive-Manufacturing-Based Operating Frequency Adjustment Procedure

“…These new applications are associated with requirements for high-performance devices, which are supposed to feature small sizes and low weights, exhibit a wide range of operating frequency tuning, and have efficient tuning mechanisms [4]. Electrical, magnetic, and mechanical tuning methods have been employed in the literature to create tunable planar and 3D filters [5]. The majority of research efforts have been focused on planar tunable notch filters based on substrate-integrated waveguides (SIW), coplanar waveguides (CPW), and cavity resonators [6][7][8][9][10][11].…”