Investigation of the Surface Roughness Effect on the Performance of an X-Band RF Filter Manufactured by Laser Powder Bed Fusion

Additive manufacturing (AM) offers the advantage of producing parts layer by layer, enabling the creation of intricate geometries with shorter production times. These benefits provide an opportunity to manufacture complex-shaped microwave technology parts, such as waveguides and radio frequency (RF) filters, which are conventionally difficult, costly, or impossible to manufacture. However, certain challenges, such as surface roughness, electrical conductivity, and dimensional consistency, must be addressed to meet the high-performance requirements of RF parts. This study evaluates the effects of design, manufacturing, and postprocessing of X-band RF filters manufactured with laser powder bed fusion (L-PBF) on the performance of RF microwave parts. Six filters were printed and results were compared to a reference filter manufactured by conventional methods to determine whether metal AM, with appropriate surface treatments and plating, can serve as an alternative for microwave components. The results of this study demonstrate that the RF filter produced by metal AM showed similar performance to the original filter after undergoing surface roughness improvements using the electrochemical method, Hirtisation, resulting in an average of 50% improvement in roughness compared to raw production and the silver-plating application. The average insertion loss (IL) difference between the reference and the additively manufactured filters is minor, 0.1 dB, leading to an almost identical performance.