Low-Cost Microwave Components’ Fabrication in Hybrid Technology of Laminates and Additive Manufacturing on an Example of Miniaturized Suspended Directional Coupler

A low-cost approach for the fabrication of low-loss microwave components in hybrid technology of laminates and additive manufacturing is presented in this paper. A standard copper-cladded printed circuit board technology is used in combination with a basic stereolithographic 3D printing technology and industry-standard physical vapor deposition technology of aluminum for manufacturing one of the basic building blocks of microwave systems - a 3-dB coupled-line directional coupler in suspended technique operating at 2.0 GHz band. A thin laminate with the coupler traces' mosaic is suspended inside a metal-coated 3D printed enclosure. The presented study explores the performance of the circuit in terms of total power loss vs. the properties of deposited metallization layer serving as a ground plane. It is shown that when the surface roughness of the 3D printed enclosure is low enough, which can be achieved with the use of a layer of lacquer primer before metal deposition, the conductor-related power losses are lowered to an acceptable level. An exemplary directional coupler was developed along with three variants of the enclosure and the reference one. The measurement results validate the potential of this hybrid technique to deliver fully valuable microwave components at a very low manufacturing cost.