A Wideband Metal-Only Transmitarray With Two-layer Configuration

This letter presents a novel wideband metal-only transmitarray (TA) design. Up to date, existing works on metal-only TAs use at least three layers spaced by air gaps. Compared to these designs, the presented TA only has two layers but with wider bandwidth and low insertion loss. The TA unit cell consists of two metal layers connected by a metal post, and the unit cell provides a 360 phase shift range. This type of configuration increases the mechanical robustness of the TA surface and improves the alignment accuracy of the layers. Through mirroring the slots on the bottom layer, the electrical field of the transmitted wave is rotated by 180 which is equivalent to a phase shift of 180. Using this characteristic and simultaneously adjusting the lengths of the slots, a continuously 360 phase shift range is obtained. To verify this design method, a prototype consists of 256-unit cells was designed, fabricated, and measured. The experimental results show that the TA has 14.6% 1-dB gain bandwidth and 47.6% aperture efficiency at 8.5 GHz. The proposed TA has the advantages of wideband, no dielectric loss, and robust performance.