Low-Loss and Compact SISL Bandpass Filter Using Multilayer Stacked DLDCR
Shuangxu Li, Lei Zhu, Kaixue Ma · IEEE Microwave and Wireless Technology Letters · 2025
In this letter, a low-loss and compact substrate-integrated suspended line (SISL) bandpass filter (BPF) is designed by the improvedQ-factor double layers and dielectric cutout resonator (DLDCR). Compared to the classical SISL single-layer resonator, DLDCR exhibits lower dielectric loss. By incorporating multiple metalized vias in the DLDCR, the desired improvedQ-factor quasi-TEM mode remains minimally impacted, while the undesired resonant induced by the substrate-integrated suspended parallel stripline (SISPSL) mode is effectively moved to a frequency far away from the operating frequency of BPF. Meanwhile, to further reduce the dielectric loss associated with the resonator coupling, DLDCRs are vertically stacked on multiple boards to achieve air coupling. As a verification, a high-selectivity cascaded quadruplet (CQ) SISL BPF operating at 8.1 GHz using the low-cost FR4 dielectric is synthesized, simulated, and measured. The proposed BPF has the advantages of low loss, compact, low cost, and self-packaging.