Design of Circularly Polarized Transmit array Antenna using Low-Profile Dual-Linearly Polarized Elements

A low-profile dual-linearly-polarized unit cell in X-band, and its capability is demonstrated by a circularly polarized transmit array. 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 of the unit cell is only 1 mm. Prototype of a 341-element transmit array, the incoming incident linearly polarized wave is transformed into the outgoing circularly polarized wave, is simulated. The measured results show that the proposed transmit array 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%.