A Dual Function Reconfigurable Bandpass Filter for Wideband and Tri-band Operations

A dual-functional reconfigurable filter is explored for the application in wideband and triple band pass filter. The wideband configuration is implemented by parallel combination of open stub loaded and short circuited stub loaded resonators to exhibit a passband from 2.0 GHz-6.1 GHz. Tight coupling generates transmission zeroes at the either side of passband, which enhances the selectivity. The proposed tri-band BPF offers passbands at 2.4 GHz, 3.5 GHz and 5.2 GHz where two-stepped impedance resonators (SIRs) and one uniform impedance resonator (UIR) are assembled to accomplish such behavior. The two short circuited stubs are connected to the feed line to extend the range of upper stopband. PIN diodes are effectively utilized to switch the operation from wideband to tri-band or vice versa. Detailed design guidelines are provided to design the proposed filter. The behavior of the proposed filter topology is investigated by even and odd mode analysis. The developed reconfigurable filter is fabricated and measured to verify the anticipated and simulated results. A close agreement is observed between them. The fabricated reconfigurable BPF has a very compact size, high selectivity, less insertion loss and good return loss profile.