RF Characterization of 3-D-Printed Material for Antenna Applications

The 3-D additive printing technology has been employed recently for the manufacturing of a wide variety of radio frequency (RF) circuits; in particular, it is very attractive for complex structures manufactured in planar and conformal shapes, such as antennas for both civilian and military applications. The complex permittivity extraction of 3-D-printed filaments for an associated printing pattern is required for accurate design and modeling of antennas, as the commercially available filaments lack RF properties information. Accurate extractions of various 3-D-printed filaments are presented using curve fitting of simulated to measured scattering parameters of custom-designed test circuits. Extracted complex permittivity of implemented circuits depends on various 3-D-printer settings, infill percentage, and 3-D-printing patterns for different materials. The extraction was performed over broadband (1–10 GHz) using a microstrip transmission line (TL) and narrowband using an annular ring resonator (ARR) (2.4 and 5.4 GHz) enclosed in a metallic cavity package for popular polylactide (PLA) and acrylonitrile butadiene styrene (ABS) filaments. A statistical analysis of three test circuits of each category is performed to have an accurate extraction process. According to our extraction, the ABS filament had a lower loss tangent than PLA. The complex permittivity of ABS filaments with a triangular pattern and a 10% infill had an average value of 1.36-j0.006 and 1.34-j0.012, whereas with 100% infill, it was an average of 2.5-j0.012 and 2.52-j0.016 at 2.4 and 5.4 GHz, respectively. The 3-D-printed probe-fed annular ring antennas (ARAs) of three different infills were designed, simulated, manufactured, and evaluated against baseline performance using RT/Duroid for Wi-Fi bands of 2.4 and 5.4 GHz. A gain of about 5–8 dBi on the broadside was achieved for 3-D-printed planar structure antennas in Wi-Fi bands for 100%–10% infill with a triangular pattern using the optimized setting.