Circularly Polarized Transmitarray Antenna Using Low-Profile Dual-Linearly Polarized Elements

We propose a low-profile dual-linearly polarized unit cell in X-band, and its capability is demonstrated by a circularly polarized transmitarray. The unit cell comprises three metallic layers etched on two dielectric slabs without air gap. Cross strips are inserted in cross slots on the top and bottom layers, and the T-slot structure is etched on the middle layer. The proposed unit cell has high isolation between the dual polarizations, and its total thickness is only 1 mm. Prototype of a 341-element transmitarray, which transforms the incident linearly polarized wave into the outgoing circularly polarized wave, is also fabricated and tested. The measured results show that the proposed transmitarray realizes 3.5% (9.8-10.15 GHz) axial-ratio bandwidth and 4% (9.7-10.1 GHz) 1-dB gain bandwidth. The measured peak gain at 10 GHz is 21.9 dBi, with the aperture efficiency of 36%.