Reconfigurable dual-band bandpass filter with fully-switch operation using λ/2 folded-resonator with varactor-loaded open-stub

In this paper, a prototype of reconfigurable dualband bandpass filter is proposed. It features independently frequency-controllable quasi-elliptic-type passbands with stopband transmission zeros that can be intrinsically switched on/off. Tunable dual-resonance (i.e., f i and f 2) is introduced in this filter by the half-wavelength (λ/2) folded-resonator with series varactor-loaded open-stub. To verify the operational mechanism above, a tunable dual-band bandpass filter with added passband-switching capability is fabricated and measured. It exhibits frequency-tuning ranges of 38.2% and 33.1% for the dual-band, respectively.