Deterministic approach to decoupling amplitude from phase via a single-layered metasurface

Controlling the phase and amplitude of reflected waves has been challenging due to the inherent coupling between them. Changes in the phase of a wave often result in changes in its amplitude, and vice versa. This coupling makes it difficult to control both parameters independently. Here we report a deterministic approach, illustrated by an equivalent circuit model, to decouple the phase from the amplitude of reflected waves based on a single-layer metasurface. With the variables conversion and appropriate impedance patterns, this approach allows for the generation of 1-bit phase meta-atoms with a natural phase difference of 180° and controllable amplitude ranging from 0 to 0.9. Furthermore, the decoupling frequency can be customized by using different permittivities and dielectric thickness. These 1-bit phase meta-atoms, whose amplitude can be independently controlled, have potential in wavefront manipulation such as multi-beam antennas and hybrid radar cross section reduction metasurfaces. As a proof of concept, a metasurface for backscatter suppression is demonstrated and measured. The reflected wave is scattered by wavefront modulation with phase control in the spatial domain, while the energy is absorbed by amplitude control in the energy domain, resulting in extremely low backward scatterings in a wideband. In addition to the discussion of passive metasurfaces, the active case is also expanded on. The results of our paper demonstrate the potential of the phase- and amplitude-decoupled approach in designing multi-function metasurfaces for wavefront manipulation and radar applications.