RF Characterization of 3D-Printed Material for Antenna Applications

Three-dimensional (3D) 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 3D printed filaments for an associated printing patterns is required for accurate design and modeling of antennas, as the commercially available filaments lack RF properties information. Accurate extractions of various 3D 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 3D-printer settings, infill percentage, and 3D printing patterns for different materials. The extraction was performed over broadband (1-10GHz) using microstrip transmission line (TL) and narrowband using annular ring resonator (ARR) (2.4GHz and 5.4GHz) enclosed in a metallic cavity package for popular PLA and 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 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 2.4GHz and 5.4GHz respectively. The 3D printed probe fed annular ring antennas (ARA) of three different infills were designed, simulated, manufactured, and evaluated against baseline performance using RT/Duroid for WiFi bands of 2.4GHz and 5.4GHz. A gain of about 5-8dBi on the broadside was achieved for 3D printed planar structure antennas in WiFi bands for 100%-10% infill with triangular pattern using the optimized setting.