3-D Printed Noninterleaved Reflective Metasurfaces Supporting Dual-Band Spin-Decoupled Quadruplex Channel Independent Beam-Shaping With Controllable Energy Distribution

This article presents 3-D printed noninterleaved reflective metasurfaces (MSs), which support millimeter-wave (mm-wave) dual-band spin-decoupled quadruplex channels with independent beam-shaping. The MS's unit cell (UC) is made of a cross-bar structure mounted on a circular-shaped patch antenna, which connects to short-ended time delay lines (TDLs). Pancharatnam-Berry (P-B) and dynamic phases are used to decouple the two spin states. Specifically, rotating the top cross-bar structure and adjusting its size provides the high-band's P-B and dynamic phases. Rotating the circular patch antenna and adjusting the length of the TDL introduce the P-B phase and dynamic phase for the low band, respectively. In addition, the mutual interference between the dual bands is minimal. The size of the noninterleaved UC is only 4 mm, corresponding to 0.33 and 0.48 free space wavelength of the center frequency for low band (25 GHz) and high band (36 GHz), respectively. For proof of concept, an MS generating orbital angular momentum (OAM) with different topological charges in four channels is fabricated and measured. Furthermore, in addition to the independent wavefront shaping, the energy distribution ratio (EDR) in the reflected co-pol and cross-pol channels can also be independently controlled over dual-band under a circularly polarized incident wave. An MS, which generates near-field focusing with different energy distribution ratios in dual bands, is fabricated and experimentally verified for demonstration. The MS samples are prototyped using a multimaterial 3-D printing technique on a single substrate.