A V-Band Inverted Microstrip Gap Waveguide End-Coupled Bandpass Filter

This letter presents an end-coupled bandpass filter (BPF) based on the recently introduced inverted microstrip gap waveguide technology. The inverted microstrip gap waveguide is advantageous for millimeter wave applications because of its low-loss, self-packaging characteristics, and cost-effectiveness. A fourth order Chebyshev-type end-coupled BPF is designed to provide a 2 GHz bandwidth at 60 GHz center frequency. The fabricated prototype embedded within a 10 cm inverted microstrip gap waveguide, containing two back-to-back transitions to rectangular waveguide, exhibits an insertion loss of 3 dB in the passband. However, the insertion loss of the filter itself is better than 1.6 dB.