Compact Single/Dual-Band Bandpass Filters with Independently Controllable Passbands Using Staircase Resonators

This paper reports compact single/dual-band bandpass filters with independently controllable passbands based on a novel microstrip staircase resonator. A parallel feeding mechanism is introduced to offer better harmonics suppression on the proposed single-band BPF and also to create a second independent resonance path between the parallel feeding lines, effectively implementing compact dual-band BPF structures. Furthermore, due to the independently separated resonance paths, the passbands can be controlled independently without affecting each other. Therefore, very close frequency passbands can be effectively obtained in the proposed dual-band configuration. For demonstration and validation purposes, three miniaturized single/dual-band BPFs are designed and fabricated.