A Low Sidelobe Liquid Metal Reflectarray Antenna using a FFT-based Algorithm

This paper presents a windwill-shaped liquid metal unit cell, which has a reflection phase variation more than 360°. A $10 \times 10$ liquid metal reflectarray antenna is proposed by utilizing the above unit cells. It can achieve a ± 60° beam scanning with a low sidelobe level (SLL) by using a FFT-based optimization algorithm. The array factor for the proposed reflectarray is obtained by performing IFFT on the electric field of the array element. Then a window function is applied on the array factor to optimize the SLL. At last, FFT is used to get the optimized phase distribution. The SLL can be improved by more than $3 \mathrm{~dB}$ for large scanning angle.