A Low-Cost Ultrathin Metal-Only Transmitarray Antenna at X-Band

This letter presents a low-cost ultrathin metal-only transmitarray (MOTA) antenna based on polarization rotation elements at X-Band. The unit-cell comprises only dual metal layers etched with a pair of perpendicularly orientated fan-shaped slits and separated by an air gap of 2 mm, featuring an ultrathin configuration of 0.067λ at 10 GHz. It twists the polarization of transmission wave orthogonally with regard to the incidence. By tuning the length of fan-shaped slits along with mirroring the bottom layer of the unit-cell, a 360° phase span and a high transmission magnitude are realized. To validate the design concept, an ultrathin MOTA accommodating 361 elements is fabricated and measured. In terms of testing results, 7% 1 dB gain bandwidth and 42% peak aperture efficiency are realized. Moreover, the sidelobe level and cross-polarization level are 22 and 25 dB at 10 GHz, respectively. In comparison with existing MOTAs, the proposed design features a remarkably lower profile with reduced fabrication complexity and cost while preserving a desirable overall performance. Furthermore, the proposed ultrathin unit-cell can also be adopted in a metal-only folded transmitarray for an even thinner and compact structure.