Space–Time–Frequency Modulation Mechanisms of Monochromatic and Nonmonochromatic Electromagnetic Waves on a Digital Programmable Transmission Metasurface

Abstract

By dynamically configuring unit structures, a digital programmable metasurface (DPM) can perform space, time, and frequency modulations of electromagnetic (EM) waves directly on the aperture, and hence linking the metasurface physics to digital information worlds. However, the interactions between DPMs and EM waves have not yet been systematically and efficiently depicted. Based on the Huygens-Fresnel principle and Fourier analysis, here the authors demonstrate the foundations of space-time-frequency joint controls of monochromatic or nonmonochromatic EM waves by DPM. Due to linear superposition properties of Fourier transform in the analysis, the space-and time-frequency modulations are naturally decoupled, hence enabling simultaneous and independent space-time-frequency controls of the EM waves. A transmissive DPM is designed and fabricated to interpret the space-time-frequency joint modulations. This work will facilitate the researches on DPMs and promote the applications of DPMs in wireless communications, intelligent sensing, and radar systems.

Recent Advances in Reconfigurable Metasurfaces: Principle and Applications

“…Furthermore, when we change the states of metasurfaces in time domain, we can obtain different harmonic waves in the frequency domain, namely, the time-varying control of metasurfaces. Based on this principle, some studies have realized the frequency modulation of the incident wave, designed metasurface communication systems and successfully transmitted data [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ].…”

Asynchronous Space‐Time‐Coding Digital Metasurface

“…A wide variety of unique applications such as harmonic beam steering, beam shaping, efficient frequency conversion, nonreciprocal effect, and nonlinear information modulation have been presented, investigated and experimentally demonstrated. [23][24][25][26][27] To date, however, all the published STCMs were developed under the synchrony frame. Generally speaking, a digital coding metasurface is said to be synchronous if all metaatoms change their states with the same frequency based on a global clock signal.…”

A Single Metasurface Can Perform Range‐Velocity Detection and Target Imaging Simultaneously at Single Frequency

“…[8][9][10] This method is efficient for far-field target because communications. [30,[50][51][52][53][54] For target detection and imaging, DPMs can provide spatial resolution without using phased arrays or MIMO antennas, and spatial processing of radar signals can be decoupled to DPMs. Hence, DPMs can greatly decrease complexity of signal processing and simplify architecture of the detection and imaging systems.…”

“…By designing aperture codes of the DPMs, electromagnetic waves can be directly modulated in time-frequency domain and space domain. [30] Due to their extraordinary capability in manipulating electromagnetic waves, DPMs have been extensively researched in many areas such as compact signal computation processor, [31,32] dynamic beam control, [33][34][35][36][37] holographic imaging, [38][39][40][41][42] direction-ofarrival (DOA) estimation, [43,44] radar systems [44][45][46][47][48][49] and wireless Range, velocity, and geometric shape are primary features of a moving target. Obtaining these features usually needs high-cost system and complicated signal processing.…”