Additive Manufacturing of E-Plane Cut Dual-Mode X-Band Waveguide Filters With Mixed Topologies

In this article, the design and realization of low-loss 3-D printed waveguide filters in the X-band are discussed. Multiple transmission zeros (TZs) are introduced by using symmetrical TE
₃₀₁
/TE
₁₀₂
dual-mode cavities. The design flexibility is enlarged by adding classical triplet and quadruplet sections that are combined with the dual-mode blocks. The coupling matrices of all topologies are derived, and the fundamental limitations are presented. All proposed filter setups are symmetrical and can, therefore, be cut in the E-plane. This allows the application of low-cost fused deposition modeling (commonly known as FDM) additive manufacturing techniques. The galvanization process to achieve a high conductivity surface will be discussed as well. The measurements show good agreement with the simulation, while Q-factors of up to 2000 can be achieved.