A dual‐band filtering structure for highly selective reconfigurable bandpass filter and filtering balun

This article proposes a filtering structure consisting of two half-wavelength resonators and open-stub loaded resonators, which generates third-order passbands. Multiple transmission zeros are introduced by the newly developed coupling scheme, resulting in extremely sharp roll-off desirable for highly selective filters. The proposed is applied to design PIN-diodes switch-controlled reconfigurable dual-band bandpass filter (BPF) with four-state responses: both passbands ON, OFF, high-frequency passband low-frequency ON. Stepped-impedance open stubs one-end-grounded coupled lines studied employed suppress unwanted responses. In addition, structures placed symmetrically balun BPF. Double-sided parallel-strip added input port filter, their inherent out-of-phase feature enables convert unbalanced signal balanced at desired frequencies. measured results fabricated devices agree well simulated results. switchable BPF have (2.8 4.8 GHz) high selectivity minimum roll-offs from −3 −15 dB 1.70 × 103 2.71 dB/decade, respectively. insertion loss 2.3/2.0 suppressions level OFF state as −18.2 dB. 1.8/1.4 dB, phase magnitude imbalances less than 0.3 5°, excellent performances implemented successfully demonstrate advantages efficacy different applications.