Low-Loss Circularly Polarized Transmitarray for Beam Steering Application

We present the design and demonstration of a low-loss circularly polarized (CP) transmitarray. The proposed transmitarray is composed of a receiver cell with a 180° analog phase shifter and a transmitter cell integrating 1-bit phase shifting and linear-circular polarization transformation properties. By the analysis of numerical simulation, the transmitarray is verified to transform the incident linearly polarized (LP) wave into outgoing CP wave in the frequency band of 4.75-4.85 GHz. In addition, it can realize the 360° continuous phase modulation, and its insertion loss is less than 2 dB for all the transmission phases. We fabricate a fully reconfigurable 6 × 6 CP transmitarray, and it is experimentally demonstrated to achieve 360° phase tuning range with the average loss of ~2.2 dB. When the proposed CP transmitarray is excited by a LP horn antenna, it produces a CP pencil beam at 4.8 GHz and its measured broadside gain is 14.8 dBi with axial ratio (AR) of 0.65 dB. By tuning its transmission phase, the CP transmitarray can also achieve beam steering at the angle of ±45°, and the value of AR is less than 3 dB at most of the scan angles.