A Reconfigurable Bandpass Filter Based on Novel Planar Integrated Switchable and Tunable Resonator With Improved Insertion Loss and Frequency Range

The tradeoff between the unloaded quality factor ( $Q_{\text {u}}$ ) and resonant frequency tunable range of a novel planar integrated switchable and tunable resonator is studied. The novel switchable and tunable resonators are designed based on a quarter-wavelength resonator with a floating strip loaded by a varactor diode and p-i-n diode, and the continuously switchable tuning characteristics of the resonant frequency are modeled and investigated. A reconfigurable bandpass filter (BPF) with continuously tunable frequency and stable bandwidth based on the switchable and tunable resonator with improved $Q_{\text {u}}$ is designed, fabricated, and measured. The developed component demonstrates a tuning range of 1.05–2 GHz with a typical bandwidth of 124 MHz and a minimum insertion loss (IL) of 1.8 dB.