High-Performance Dual-Band Bandpass Filter Using SIPW and CSRRs

As frequency resources become increasingly scarce, the need to develop miniaturized, dual-band filters for improving spectrum utilization in broadband communications have become urgent. In this article, we introduce a novel approach for designing a dual-band bandpass filter (BPF) using a hybrid technique that combines substrate-integrated waveguide (SIW), spoof surface plasmon polariton (SSPP), and complementary split ring resonator (CSRR) technologies. The substrate-integrated plasmonic waveguide (SIPW) is created by etching meander-slot SSPP structures onto the top layer of the SIW. This design reduces both the lateral and longitudinal dimensions without adding complexity. By etching CSRRs onto the back of the SIW, the filter achieves strong electromagnetic coupling and narrowband suppression, resulting in a dual-band BPF with operating frequencies of 7–8.1 and 10–11.2 GHz. To validate this design, we fabricated and measured a prototype. The results demonstrate that the proposed SIPW BPF exhibits exceptional filtering performance, with a return coefficient of more than −10 dB and an insertion loss (IL) of less than 1.7 dB in both passbands. In adddition, the designed BPF features wide passband and stopband characteristics.