Design Workflow of Frequency Variation Coupling for Waveguide Filter

A synthesis method for dual-band in-line waveguide filters using frequency-variant coupling (FVC) is proposed. By applying a generalized admittance matrix transformation based on low-pass prototype characteristics, multiple cross-couplings are eliminated while introducing FVCs in a single step. The method enables compact dual-band responses using coupling irises to realize FVCs and introduce transmission zeros. A synthesized and simulated dual-band filter validates the approach for advanced waveguide applications.