Theory and Design of Low-Insertion Loss Fin-Line Filters

A design theory is described for low-insertion loss fin-line filters that includes both higher order mode propagation and finite thickness of the dielectric substrate and the metallic fins. Design data for three-resonator type fin-line filters with several substrate thicknesses are given for midband frequencies of about 15, 34, and 66 GHz. The measured insertion losses in the passband are 0.25, 0.5, and 1.3 dB, respectively, for these three frequencies.