A Novel Iris Waveguide Bandpass Filter Using Air Gapped Waveguide Technology

Ridge air-gapped waveguide and groove air-gapped waveguide are the most commonly used air-gapped waveguides. In this work, a full air-gapped waveguide (FGW) is first proposed. The four walls of the FGW are manufactured independently, which makes it possible to fabricate complex structures flexibly. To verify its electrical performances, a Ka-band FGW, a capacitive iris FGW BPF, and an iris rectangular waveguide (RW) BPF are designed and manufactured. The proposed FGW can connect with RW without any transition. The measured insertion loss of the FGW is less than 0.2 dB in most Ka band except frequencies lower than 28 GHz. The measured insertion loss of the FGW BPF is 0.2 dB in its operation band from 31.5 GHz to 35.1 GHz, while that of the RW BPF is also about 0.2 dB. In general, the performances of the proposed FGW and FGW BPF reach the performances of their RW counterparts.