Optimal Phase Angle Rounding-Off for Forming Closely Spaced Beams for On-board Active Phased Array System

Modern on-board active Phased Array Antenna System (PAAS) uses Digital Phase Shifters (DPS) to perform electronic scanning. The DPS has limitation of phase angle quantization, which when employed in PAAS lead to quantization of beam scanning steps. When closely spaced beam are needed for target tracking, the quantization of phase angles due to DPS leads to rounding-off of phase angles, which causes errors in beam pointing. This paper proposes an optimal Rounding-Off approach, to form closely spaced beams with low beam pointing errors. The paper formulates an optimization problem of minimizing the beam pointing errors, and obtain the rounding-off of the required phase angles to achieve this minimization objective. The proposed method has been integrated with primitive scanning trajectories for the performance evaluation.