Compact Dual-Band Inverted-Microstrip Ridge Gap Waveguide Bandpass Filter

摘要

A compact dual-mode inverted microstrip ridge gap waveguide (IMRGW) resonator and a series of dual-band IMRGW bandpass filters (BPFs) with easily controllable passbands are proposed for the first time in this article. The resonator is embedded into the ridge of the IMRGW without disturbing the placement of the mushroom-type bed of nails. A metalized via-hole is introduced to the center of the IMRGW resonator to ground a central patch, resulting in an inverted microstrip resonance mode and a cavity resonance mode simultaneously. The cavity resonant mode is relatively insensitive to the dimensions of the central patch, while the inverted microstrip resonance is insensitive to the dimensions of the cavity enclosed by electromagnetic band-gaps (EBGs) and two rows of metalized via-holes. Therefore, the resonant frequency of the two modes can be tuned independently. The resonators can be cascaded easily with a short IMRGW transmission line. A series of IMRGW based dual-band BPF with different orders are designed, fabricated, and measured. The third-order BPF's simulated passbands are 13.07-13.41 and 18.46-18.91 GHz with a fractional bandwidth of 2.5% and 2.3%. Low insertion losses better than 1.7 and 2.1 dB are obtained on the two passbands. The measured passbands are 13.52-13.86 and 18.9-19.34 GHz with a fractional bandwidth of 2.3% and 2.2% while the insertion losses are better than 2.5 and 2.3 dB for the third-order BPF.