Power handling of high-Q evanescent-mode tunable filter with integrated piezoelectric actuators

This paper investigates for the first time the power handling versus tuning ratio trade-off for high-quality-factor (high-Q) evanescent-mode tunable cavity bandpass filters with piezoelectric actuators. A non-linear circuit model is proposed to prescribe the high-power effects on the filter performance. A new parameter, distortion ratio (DR), is utilized to quantify the non-linear frequency-response distortion induced by unwanted displacements of the filter's piezoelectric actuators due to high-power RF signals. Both experimental and theoretical results yield a nearly linear relationship between the filter tuning ratio and the input power (in dBm). The presented filter can successfully handle a 1-W power while being tuned from 1.7–2.8 GHz (1.65 ∶ 1 tuning ratio) with less than 10% distortion ratio. For a 10-W operation, the tuning range is reduced to 2.2–2.8 GHz (1.28 ∶ 1) with the same distortion ratio.