A novel high-Qu octave-tunable resonator with lumped tuning elements

This paper presents a novel design of high-quality factor (Q_u) continuously-tunable resonator compatible with standard PCB fabrication technology. The proposed resonator is tuned by lumped element varactors placed on the top surface of a substrate-integrated evanescent-mode cavity, thus significantly reducing the complexity of integration without sacrificing Q_u. The proposed design approach is compatible with a variety of tuning elements, including solid-state, ferroelectric, and RF-MEMS varactors. A tunable resonator with solid-state varactors is demonstrated to validate this design approach. The resonator surpasses the state-of-the-art with a frequency tuning range of 0.5-1.2 GHz (tuning ratio of 2.4 : 1) and Q_u of 82-197. An RF-MEMS varactor enabled tunable resonator based on the same design further shows Q_u of 240 at 6.6 GHz.