A low-side-lobe folded transmitarray antenna based on metasurface with independent amplitude/phase control

Abstract In this paper, a low-side-lobe folded transmitarray antenna (LSLFTA) based on metasurface (MS) that can independently control amplitude and phase is proposed. An MS, composed of two vertically placed polarization gates, can realize the efficient reflection of y-polarized waves, efficient transmission of x-polarized waves, and independently control of phase and amplitude is designed for the top surface. A polarization conversion surface (PCS) using an open resonant ring that can efficiently achieve cross polarization conversion is presented. The feed antenna is placed on the center of the top surface to obtain an accurate electromagnetic amplitude distribution. To the best of our knowledge, our work is thus the first one to achieve low-side-lobe FTA. The LSLFTA operating at 14.5 GHz is fabricated and measured to verify the design. After adding amplitude modulation (Taylor distribution), the side lobe level (SLL) is 5.2 dB and 7.5 lower than that of only phase modulation in the yoz plane and xoz plane, respectively. The 3 dB gain bandwidth of the antenna is 19.4% (13.5∼16.4 GHz), and the maximum aperture efficiency is 25.8%. Our work is a promising candidate in the design of high-gain, low SLL, and low-profile antenna.