Synthesis and design of direct-coupled rectangular waveguide filters with arbitrary inverter sequence

A framework for the design of direct-coupled waveguide filters with both impedance and admittance inverters is presented. Combinations of sequences of four different inverter structures permit the use of both half-wave and quarter-wave resonators as well as the creation of transmission zeroes to the left and right of the passband. Many different and new filter designs are presented for common filter specifications and demonstrate the variety of possible design realizations. The difference between synthesized and optimized responses is explained. The coupled-integral equation technique is used for fast component design, and final performances are validated by the commercial software package μWaveWizard. Filter dimensions are provided.