On the Development of Metal 3D Printed Bandpass Filter With Wide Stopband Based on Deformed Elliptical Cavity Resonator With an Additional Plate

This paper presents a newly developed metal 3D printed waveguide bandpass filter based on a modified deformed elliptical cavity resonator with an additional plate. The modified resonator has excellent design freedom allowing semi-independent control of centre frequency, bandwidth, and transmission zeros. Furthermore, transmission zeros can be placed close and far from the passband to improve frequency selectivity and stopband’s width and rejection, respectively. Theory of the resonator, filter design with an example, and simulated and experimental results with extensive discussion are given. As proof of concept, a 5-pole Ku-band wideband filter was designed and manufactured using Selective Laser Melting, a metal 3D printing technique. Even though the prototypes were tested as-built, i.e. without any surface post-processing, the simulated and measured results have good agreement and consistency between all four printed prototypes. Moreover, the prototypes were manufactured in one piece, significantly improving measured results compared to the previous two-piece prototypes.