Technological Investigation of Metal 3-D Printed Microwave Cavity Filters Based on Different Topologies and Materials

This article presents metal 3-D printed wideband bandpass filters based on a deformed elliptical cavity resonator. The resonator can produce a wide stopband response by realizing arbitrary real-frequency transmission zero (TZ) at prescribed frequencies. The design procedure of canonical filtering functions is detailed. Six design examples of bandpass filters are presented to validate the design methodology. Three of the designed filters were metal 3-D printed using selective laser melting (SLM) in AlSi10Mg and commercially pure copper for experimental verification. Copper filter prototypes were printed in one piece and electro-polished to improve the surface finish. Aluminum filters were printed in three different orientations to the wiper to investigate the influence on radio frequency (RF) performance. All measured results have a good agreement with simulations. Furthermore, an in- depth review and discussion of additive manufacturing (AM) techniques for producing complex microwave components and strategies to mitigate the drawbacks of AM are given.