Coupled stepped-impedance resonator based dual-band adaptable bandpass filter with tunable lower band central frequency and bandwidth

We report a microstrip coupled stepped-impedance resonators (CSIRs) based concurrent dual-band reconfigurable band-pass filter (BPF) with tunable lower band central frequency and bandwidth through a single DC bias control voltage. Semiconductor varactor diodes have been used as the tuning element for getting continuously tunable frequency and bandwidth response. Tuning has been introduced in lower band central frequency and lower frequency bandwidth by properly incorporating varactor diodes in the CSIR structure. Varactor diodes incorporated in series configuration with the resonator in the CSIR structure provides adaptability in lower frequency band while upper band is fixed. Design approach and analysis have been provided along with the measurement results for the validation of the proposed concept.