Evaluation of 3-D Printed Monolithic G-Band Waveguide Components

This article presents a comprehensive evaluation of 3-D-printed monolithic waveguide components fabricated by a high-precision micro laser sintering (MLS) process. The investigated devices are two 180-GHz bandpass filters and a straight
$G$
-band (140–220 GHz) waveguide section. All were made of stainless steel, which was later gold coated using an electroless process. One of the filter samples was characterized using micro X-ray computed tomography (XCT) to inspect the printing quality as well as measure the internal dimensions. The sample was then sectioned to allow measurement of the surface roughness of the inner surfaces and inspect the gold coating quality. The as-manufactured stainless steel components showed high insertion losses: over 3 dB in the filter passbands and between 4.7 and 7 dB for the waveguide section, increasing with frequency over the
$G$
-band. This loss is due to the electrical conductivity of stainless steel as well as the surface roughness. Gold plating significantly reduced the insertion losses to 0.5 dB for the filters and to between 0.6 and 1 dB for the waveguide section. The investigative study showed the high-dimensional accuracy and good printing quality achieved by MLS, demonstrating the value of the technique in producing monolithic metal waveguide components with fine geometrics.