This letter introduces stepped-impedance bandpass filters based on the slab air-filled substrate integrated waveguide (SAFSIW), which provides a compromise in terms of loss and footprint between substrate integrated waveguide (SIW) and air-filled SIW (AFSIW). First, the theoretical unloaded quality factor of the SAFSIW guided-wave structure is presented. Then, a design procedure of SAFSIW stepped-impedance bandpass filters is introduced. Finally, for demonstration purposes, a third-order Chebyshev filter, centered at 30 GHz, is synthesized, optimized, fabricated, and measured. With a low-cost FR-4 to enclose the structure, a return loss better than 15 dB with a minimum insertion loss of 0.99 dB in the passband is obtained in experiments.

中文翻译：

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介质板充气基板集成波导 (SAFSIW) 带通滤波器

这封信介绍了基于平板充气衬底集成波导 (SAFSIW) 的阶梯阻抗带通滤波器，它在衬底集成波导 (SIW) 和充气 SIW (AFSIW) 之间的损耗和占用空间方面进行了折衷。首先，介绍了SAFSIW导波结构的理论卸载品质因数。然后，介绍了 SAFSIW 阶跃阻抗带通滤波器的设计过程。最后，出于演示目的，合成、优化、制造和测量了一个以 30 GHz 为中心的三阶切比雪夫滤波器。使用低成本的FR-4封装结构，实验中获得了优于15dB的回波损耗，通带中的最小插入损耗为0.99dB。