Bandpass-to-Bandstop Reconfigurable Tunable Filters with Frequency and Bandwidth Controls

A novel method is proposed for designing bandpassto-bandstop reconfigurable tunable filters. The proposed method employs standard bandpass and bandstop design theory which does not require complex coupling synthesizing process, and can be applied for arbitrary-order bandpass-to-bandstop reconfigurable filters with both frequency and bandwidth control. Second-order and third-order bandpass-to-bandstop reconfigurable filters from 2 to 2.7 GHz were built to demonstrate the proposed method. The filters offer wide frequency and bandwidth tuning flexibility in both bandpass and bandstop modes, and occupy an area smaller than 20 mm × 20 mm on a substrate with relative dielectric constant εr= 10.8 substrate. Theory and measured results are presented with good agreement.