Characterization of the Dielectric Properties of 3D Printing Filaments Using Cavity Perturbation Technique for 5G Applications

Cavity perturbation method is applied in this paper to assess the electric permittivity (ɛr) and loss tangent (tanδ) of dielectric materials at the 3.5 GHz microwave frequency of the 5G test band of the Global System for Mobile communications Association (GSMA) spectrum. These characteristics are important in the design of radomes, antenna fixture parts and spacers for airfilled multilayer structures for antennas and microwave circuits. A cylindrical cavity with two ports was designed and fabricated to operate in the TM010 mode. The characterization process includes the preparation of cylindrical samples with thickness of 12.5 mm with concentrations of 25%, 50%, 75% and 100% of the following materials: acrylonitrile butadiene styrene (ABS), Tritan, polyethylene ethylene glycol terephthalate (PETG), acrylonitrile styrene acrylate (ASA), polyamide (Nylon), Polylactic acid (PLA) and CRcarbon. The measured S-parameters allowed calculating the quality factor, the electrical permittivity and the loss tangent of the analyzed samples by comparison to numerical results obtained by the Finite Element Method (FEM) using Ansys HFSS. The results obtained demonstrate that the filling percentage of the samples is an efficient technique to control the effective dielectric constant of 3D printed parts, provided that the filling mesh dimensions are much smaller than the operating wavelength. Such a condition is easily achieved at 3.5 GHz with modern 3D printers. Finally, a dielectric resonator antenna has been designed and measured, whereby excellent agreement between the simulation predictions and measured results has been achieved, hence demonstrating the accuracy of the proposed dielectric measurement technique.