Dielectric Resonant Antennas via Additive Manufacturing for 5G Communications

In this work, a variety of polymers with relatively low dielectric permittivity were used to fabricate 3D-shaped DRAs with identical geometry by means of two different Additive Manufacturing (AM) technologies. Three DRA prototypes made of polylactic acid (PLA), its conductive counterpart (conductive PLA) and glass-fiber filled polyamide (PA+GF) were manufactured via Fused Deposition Modelling (FDM). Other two prototypes were fabricated using photopolymer epoxy resins via stereolithography (SLA). All the DRAs were designed to operate in the 3.5 GHz band for 5G applications. The fabricated prototypes were characterized by means of a Vector Network Analyzer and an anechoic chamber, using the feeding monopole as reference. It is worth stressing that, since the two AM technologies feature different dimensional accuracy and surface quality, the effect of the polymer characteristics and manufacturing technologies on DRAs performance were evaluated. The experimental results show that PLA, PA+GF and epoxy resin-made DRAs have good performance in terms of scattering parameter S
₁₁
(-35 dB for PLA and PA+GF, and -40dB for epoxy resins) and gain up to +3dB over a bandwidth of 1 GHz centred at 3.5 GHz. Moreover, the lower dimensional accuracy and surface quality exhibited by the FDM-made samples show to have impact mainly on the intensity of scattering parameter S
₁₁
. Furthermore, although conductive PLA displays higher ε
_r
value and lower tan δ than the other considered polymers, this particular prototype shows worse overall performance: indeed, losses induced by low electrical conductivity (σ == 10
^-6
S) lead to a negative gain of about -5 dB.