Harmonized Rapid Prototyping of Millimeter-Wave Components using Additive and Subtractive Manufacturing

In this article, a harmonized fabrication and assembly process combining additive and subtractive manufacturing (SM) is introduced for the rapid manufacture of millimeter-wave components, especially those using hollow substrate integrated waveguide (HSIW). HSIW has been shown to have some significant advantages for millimeter-wave communications, radar, and sensing systems, but its fabrication can be challenging. To pattern the metallic layers that form the top and bottom HSIW walls, as well as other structures such as microstrip lines and landing pads for integrated circuits and passive components, a subtractive fabrication process using a water-jet laser cutter was employed. To fabricate the dielectric substrate using low-cost Acrylonitrile Butadiene Styrene (ABS), with cavities for the waveguides, a Stratasys PolyJet 3-D printer (Objet 1000) was used. The HSIW components were then assembled using commercially available through-substrate copper transitions, completely eliminating the process of through-substrate via-hole formation and metallization. The manufacturing techniques conventionally used for these vias are generally expensive and intricate at millimeter-wave frequencies. Therefore, the proposed fabrication and assembly process in this article decreases the overall fabrication cost and complexity, and it is shown that this is achieved without compromising the performance of the millimeter-wave HSIW components. The measurement results show that a propagation loss of 13.55 dB/m (0.01355 dB/mm) is achieved for the first HSIW prototype. Based on HSIW structures, it is believed to be among the lowest propagation losses ever reported at these frequencies. The proposed harmonized fabrication and assembly technique also has a strong potential, by combining the advantages of additive and SM techniques, to realize a new class of millimeter-wave components with the possibility of manufacturing conformal and flexible component shapes, based on the materials used.