3-D Printed Air Substrates for the Design and Fabrication of RF Components

This paper presents the fabrication and characterization of radio frequency (RF) and microwave passive structures on an air substrate using additive manufacturing (3-D printing). The air substrate is realized by 3-D printing RF structures in two separate pieces and snapped together face to face using a LEGO-like process. Spacers printed on the periphery provide the desired air substrate thickness. Metal patterning on nonplanar printed plastic structures is carried out using a damascene-like process. Various RF structures such as low dispersion transmission line, T-line resonator, high-gain patch antenna, slot antenna, and cavity resonator are demonstrated using this process. Good performance is achieved; for example, measured 50-Ω transmission line shows low loss of 0.17 dB/cm at 4 GHz, and a patch antenna (center frequency of 4.5 GHz) shows gain and bandwidth of 7.6 dB and 0.2 GHz, respectively. Details of both measured and simulation results are presented.