Abstract

In this article, we review the topic of Huygens' metasurfaces with an emphasis on existing and emerging applications at microwave frequencies. Huygens' metasurfaces have demonstrated unprecedented capabilities of controlling electromagnetic wavefronts by means of electric and magnetic dipole moments arranged in a thin sheet. We present the fundamental principles of Huygens' metasurfaces based on the boundary conditions governing their operation. Then, we discuss the aspect of practical realization of Huygens' metasurfaces and the different types of constituent subwavelength scatterers (unit cells). Moreover, we summarize recent developments in several areas related to metasurfaces, such as perfect anomalous refraction, polarization control, antenna beamforming and reconfigurable metasurfaces. Lastly, we provide a brief outlook on emerging metasurface-based microwave technologies that are expected to further grow in the future.

Highlights

  • In the past few years, research in the field of ‘artificial’ electromagnetic materials or ‘metamaterials’ has seen an explosive growth

  • One of the most sought-after applications of metasurfaces is for the enhancement of antenna systems, metasurface lenses for enhancing the gain of a feed antenna

  • Controlling the polarization states of electromagnetic (EM) waves is another important aspect in many practical applications such as satellite communications and imaging systems

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Summary

INTRODUCTION

In the past few years, research in the field of ‘artificial’ electromagnetic materials or ‘metamaterials’ has seen an explosive growth. By combining the scattered fields from these two structures, the wire-loop unit cell is able to directly realize a Huygens’ source Due to this property, some of the earliest demonstrations of metasurface designs utilized the wire-loop topology, such as with the refractive designs shown in [9], [21]. The first demonstrations of refraction were achieved with symmetric wire-loop unit cells as seen in [9], [21] These designs realized non-bianisitropic boundary conditions and were able to demonstrate the desired refraction with negligible reflections utilizing passive and lossless structures. Through demonstration via both microwave network and full field theory approaches, it was revealed that Omegabianisotropy would allow perfect matching of arbitrary input and output impedances, even for passive and lossless designs [15], [16] Such Omega-bianisotropy could be physically realized through asymmetry of the unit cell design. Such scattering efficiency would not be possible with non-bianisostropic designs for the same desired angle

THIN LENSES
Findings
POLARIZATION CONTROL
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