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 TAs 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 <inline-formula> <tex-math notation="LaTeX">$10\lambda _{0}\times 10\lambda _{0}$ </tex-math></inline-formula>, to the 17.5% of the <inline-formula> <tex-math notation="LaTeX">$20\lambda _{0}\times 20\lambda _{0}$ </tex-math></inline-formula> 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 TA with a size of <inline-formula> <tex-math notation="LaTeX">$15.6\lambda _{0}\times 15.6\lambda _{0}$ </tex-math></inline-formula> 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.