WR-4.3 and WR-2.8 Band Waveguide Filters Using Micro Deformed Dual-Mode Cylindrical Resonators

This letter presents two WR-4.3 and WR-2.8 band fourth order waveguide dual-mode filters, fabricated by micro metal additive manufacturing technology. For the first time, microdeformed TM₁₁₀ dual-mode cylindrical resonators are employed to realize both mode coupling and frequency tuning. This structure is more compatible with additive manufacturing. One filter centered at 220 GHz has a bandwidth of 4.5% (referred to as filter A), while another one centered at 340 GHz has a bandwidth of 1.2% (referred to as filter B). To achieve tuning and coupling, a rectangular iris structure integrated with the cylindrical resonator is introduced. Compared to classical structures, such as inserting screws or using local small perturbations, the proposed design utilizes a globally distributed small deformation, minimizing abrupt features in the cavities. This approach significantly reduces sensitivity to random manufacturing errors, resulting in good agreement between theoretical and fabricated results. The best measured return loss within the passband is 19 dB for filter A and 13.5 dB for filter B, while the insertion loss is 0.5 dB for filter A and 1.7 dB for filter B. The average center frequency shift is about 0.1% of 220 GHz and 0.35% of 340 GHz, respectively.