Transmissive Metasurface With Independent Amplitude/Phase Control and Its Application to Low-Side-Lobe Metalens Antenna

Abstract

In this article, a single-sheet metasurface (MS) for independently manipulating the transmissive phase and amplitude of linearly polarized electromagnetic (EM) wave is proposed. The amplitude modulation is achieved via imposing a rotation angle to flexibly control the ratio of polarization conversion, while the phase modulation is realized by tuning the physical parameters of the unit cell to change its resonance. By integrating the proposed single-sheet MS, a low-profile metalens antenna operating around 12.2 GHz is designed, fabricated, and experimentally validated. In particular, spatially varying amplitude on the MS aperture is designed to meet the Taylor distribution, thus reducing the sidelobe level (SLL) of the metalens antenna. In addition, special MS elements rotation strategy is performed to maintain good polarization isolation-level (PIL) performance. The measured results show that the proposed metalens antenna achieves the peak gain of 25.3 dBi at 12.6 GHz with 3 dB gain bandwidth of 16.4% (11.2–13.2 GHz). Within the 3 dB gain bandwidth, this metalens antenna achieves SLL lower than −20.5 dB with an average value of −23 dB and PIL lower than −22.2 dB with an average value of −26.5 dB. Compared with metalens antenna with phase-only modulations, the proposed metalens antenna realizes a 5.7 dB average SLL suppression. The proposed metalens antenna is a promising candidate in point-to-point communications for wireless and satellite system applications.