Circularly Polarized Phased Array System with Pattern Optimization Algorithm for Low Side Lobe Level and Scanning Axial Ratio

This paper proposes the circularly polarized (CP) phased array system with a pattern optimization algorithm for low sidelobe level and scanning axial ratio. For mobile satellite communication, the low profile CP phased array system with a low axial ratio and low sidelobe level in the scanning region is necessary. However, the previously reported phased array system hardly has the required performances simultaneously. In this paper, we proposed the CP phased array system which can control the amplitude and phase of the received signal for low axial ratio and sidelobe level. The system employs the dual-polarized receiver and polarization control unit. In the proposed pattern optimization algorithm, low axial ratio and low sidelobe level are achieved simultaneously by controlling the gain of low noise amplifier and phase offset of the phase shifter of dual-polarization. In the simulation, the proposed system has under 1 dB of the axial ratio and under -20 dB of the sidelobe level at the 2-dimensional scanning region from -50° to 50°. For validation, the 1x8 CP phased array antenna system was implemented from 4.9 GHz to 6 GHz. The measured axial ratio in the frequency bandwidth is under 2 dB and the measured sidelobe level is under -20 dB at the elevation scanning region from -53° to 53°.