Wideband Circularly Polarized Transmitarray Antenna Based on Differential Unit Cell

In this letter, a new differential receiving-transmitting (R-T) unit cell for a wideband circularly polarized transmitarray antenna (CPTA) is presented. The proposed unit cell consists of a rotational symmetric half U-slot patch (HUSP) pair for the receiving part and a two-arm spiral antenna for the transmitting part. The rotational symmetric HUSP pair generates the wideband differential currents. To produce high-gain CP directive radiation based on the phase compensation principle, a spatially dependent rotation angle is imposed on the transmitter, and a mirror symmetry is applied in the y-direction for the receiver to implement the required transmission phase. The proposed CPTA based on the designed element not only exhibits a wide-measured 3 dB axial ratio (AR) bandwidth of 61.9% (15.5 GHz to 29.4 GHz), but also yields a significant 3 dB gain bandwidth of 47.4% (17.7 GHz to 28.7 GHz). In addition, the CPTA demonstrates an acceptable peak aperture efficiency (50.7%).