Near Field Shaping with Space-Time-Coding Digital Metasurface

In recent years, space-time-coding digital metasurface (STCM) has been widely studied for its ability of simultaneously manipulating wavefronts and spectrums of the electromagnetic (EM) wave. However, researchers usually focus on the far-field characteristics of the EM waves reflected from the STCM, such as the scattering pattern for beam shaping. Here, we expand our scope to the near field manipulating with STCM. Actually, in many scenarios, STCM can be a good candidate for shaping near field. For example, for the synthesis of plane wave in the compact antenna test range (CA TR), the parabolic reflector can be replaced by the low-cost, light-weight STCM. Moreover, as STCMs can control the EM wavefronts at both fundamental and harmonic frequencies, it can generate near field plane waves along arbitrary directions at multiple frequencies. In this article, we will illustrate the mechanism of linear and nonlinear near field shaping with STCM. Then, we will consider the synthesis of quasi-plane wave in the near field for the 1
^st
order harmonic.