3D-Printable Dielectric Transmitarray with Enhanced Bandwidth at Millimeter-Waves

In this paper, a three-layer dielectric structure is presented as innovative unit-cell element for Transmitarray (TA) Antennas with enhanced bandwidth. It consists of a central layer, with a varying size square hole, used to compensate the phase of the incident field and located between two other identical layers with linearly tapered square holes, acting as matching circuits. The effectiveness of this unit-cell is demonstrated by the numerical and the experimental results here presented. As a first step, three different transmitarrays with increasing size are designed and simulated: their 1-dB gain bandwidth, centered at 30 GHz, varies from the 30.9% of the smallest configuration, having size of 10λ0×10λ0, to the 17.5% of the 20λ0×20λ0 TA. A slightly modified unit-cell is then designed, with the aim of realizing a prototype with an Additive Manufacturing (AM) technique. A 3D-printed dielectric Transmitarray with a size of 15.6λ0×15.6λ0 has been manufactured and experimentally characterized. The measured prototype shows excellent performances, achieving a 1-dB gain bandwidth of 21.5%: these results prove the enhanced features of the introduced unit-cell and demonstrate the TA feasibility with AM techniques.