Independently Tunable Compact Dual-Band Bandpass Filter With High Selectivity and Wide Stopband Using Multilayer Folded Dual-Mode SIDGS Resonator

In this paper, a multilayer folded substrateintegrated defected ground structure (SIDGS) resonator is proposed for tunable dual-band bandpass filter (BPF) design. Such resonator allocates two independently tunable resonant modes in a miniaturized size. In addition, lowpass units (LPUs) are embedded in the microstrip feed-lines to further improve the stopband rejection level. To verify the mechanism, a tunable dual-band BPF is fabricated and measured. The first passband can be tuned from 0.94 to 1.12GHz, and the second passband varies from 2.29 to 2.92GHz. The proposed dual-band BPF features high selectivity in a miniaturized size (i.e., 15.4mm ×15.6mm). Besides, it exhibits a stopband rejection of 22dB up to 12.3f1max for all tuning cases.