Additive Manufactured Dual-Mode X-Shaped Filter Realized by High-Permittivity Ceramics

In this paper, a lithography based additive manufacturing (AM) technique is used for the realization of a ceramic X-shaped dual-mode filter. The fourth order filter consists of two identical ceramics which are mounted in a copper housing and which are coupled by an aperture. Due to the arrangement of the ceramics and the associated coupling scheme, a negative cross-coupling between the first and fourth resonance is realized, leading to two transmission zeros (TZs), one above and one below the passband. The digital light processing process used for fabrication of the ceramics is described and compared to the stereolithography approach. Subsequently, the filter design process is addressed. The measurement results are compared to the simulation and reveal good agreement.