Metal-Only Huygens' Metasurface With Independent Phase and Amplitude Control for Sidelobe Suppression

In this paper, a dual-layer metal-only Huygens' metasurface (HMS) based on air medium is proposed to achieve independent phase and amplitude control of linearly polarized electromagnetic (EM) wave for sidelobe suppression in a transmissive metasurface configuration. The unit cell consists of two identical layers, each containing an inner concentric extended split-ring slot (CESS) and an outer concentric split-ring slot (CSS). Phase modulation based on Huygens' principle is realized by adjusting the physical parameters of the slots to manipulate the orthogonal electric and magnetic resonances, while amplitude is controlled by rotating the structure to modulate the co-polarized transmission based on its polarization selectivity. To validate the design concept, a phase and amplitude modulated transmissive metasurface called TM-II is designed and fabricated. For comparison, a base design employing phase-only modulation called TM-I is also realized. The measured results show that the TM-II with amplitude tailored to follow the Taylor distribution improves the sidelobe level (SLL) by 1.6 dB in the xoz plane and 6.1 dB in the yoz plane compared to the phase-only modulation design. This proposed HMS offers a new approach for independent phase and amplitude control, which could be applied to point-to-point communications, satellite systems, and high-power applications.