# Beam Scanning Capabilities of a 3D-Printed Perforated Dielectric Transmitarray
## 1 Introduction
This cell element was firstly introduced in [10; 11; 12; 13], which consists of three perforated layers: the central presents a square hole, which is used to control the phase of the transmission coefficient, while the external layers are equal and have a truncated pyramid hole, which allow for improving the bandwidth and the efficiency. This cell element was firstly introduced in [10], where its wideband behavior was tested only with numerical simulations of a medium size TA, designed using a conventional dielectric material and without considering the possible limitations introduced by the manufacturing process. In [11], the enhanced performances of the same unit-cell were compared with those of a conventional unit-cell having just a single layer with a square hole; in this case, a material usable for the realization of the TA with an Additive Manufacturing (AM) technique was considered, since this seemed to be the only adoptable method for the TA fabrication, but also in that work the designed antenna was only numerically analyzed, neglecting the constraints imposed by the AM process. The results in [11] proved that the TA with the tapered unit-cells provided a 1-dB bandwidth doubled (27.6%) with respect to that of the TA using the single layer cells (13.4%). The unit-cell was instead experimentally validated in [12]: firstly, several numerical tests were conducted to find the optimum geometric parameters and transmitarray configuration at Ka-band; then, the unit-cell was modified to make it 3D-printable in view of the limitations introduced by AM techniques; finally, a 15.6\(\lambda_{0}\)\(\times\) 15.6\(\lambda_{0}\) antenna was designed, manufactured with 3D-printing techniques and experimentally characterized in the anechoic chamber. All of the configurations considered in [10; 11; 12], were designed neglecting the effect of the direction of arrival of the incident field on the unit-cell and they are only center-fed transmitarrays that generate a main beam in the broadside direction. In [13], some very preliminary considerations on the possibility to realize a mechanically steerable transmitarray are summarized: two different unit-cells are considered, one of which is the dielectric one; small size TAs working at 5.6 GHz were designed without taking into account any manufacturing limitations and considering the possibility to design a bifocal configuration or to use a global optimizer, and then characterized numerically. In this paper, a systematic analysis of the scanning beam capabilities of the unit-cell is first performed and the obtained results are presented in Section 2; the unit-cell has then been used for the design of a medium size TA, considering the steering of the incident field varying between \(-30^{\circ}\) and \(+30^{\circ}\): the adopted design procedure is described in detail in Section 3. A prototype has been therefore manufactured and measured: the results collected in Section 4 prove that the TA provides excellent radiation performances for different scanning angles, still maintaining for each of them a large bandwidth behavior; the 1-dB bandwidth remains almost the same for the different pointing angles, which are very stable over the entire bandwidth. Finally, in Section 4, some concluding remarks and possible future actions devoted to further improve the transmitarray features are discussed.