Beam Refraction with an Isotropic and Ultrathin
Huygens’ Metasurface
Zhengbin Wang
1, 2, 3
, Yin Zhang
2, 3
, Yijun Feng
2, 3*
, Zhi Ning Chen
4
1
College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing,
China
2
School of Electronic Science and Engineering, Nanjing University, Nanjing, China
3
State Key Laboratory of Millimeter Waves, Nanjing, China
4
Department of Electrical and computer Engineering, National University of Singapore, Singapore
*Correspondence author: yjfeng@nju.edu.cn
Abstract
—
We propose an isotropic and ultrathin Huygens’
metasurface that can refract normally incident
electromagnetic waves efficiently to a predefined angle at 25
GHz. The phase gradient of the surface is controlled by five
subwavelength (with dimensions of 0.5λ
0
× 0.5λ
0
, λ
0
is the free-
space wavelength at 25 GHz) non-resonant spatial phase
shifters, which have metallic structures etched on both sides of
an ultrathin dielectric substrate (with the thickness of 0.07λ
0
).
The peak value of the transmission efficiency of the device
approaches 60%. The proposed metasurface may find
applications in designing various electromagnetic lenses, or
beam-steerable devices.
I. I
NTRODUCTION
Metasurfaces are electrically thin sheets composed of
subwavelength meta-atoms, which have extraordinary
wavefront manipulation capabilities, and have been
intensively studied throughout the microwave, terahertz
(THz), and optical bands in applications such as high-gain
beam-steerable antenna arrays, ultrathin focusing lenses,
and near-field modulating plates [1-6]. Compared with its
traditional counterpart — bulk metamaterials, the reduction
of the geometry makes the metasurface much compacted
and light-weighted, which in turn significantly decreases the
fabrication complexity and the propagation loss. To date,
most reported metasurface designs relied on electrical
resonant elements, such as V-shaped antennas [6-8], H-
shaped antennas [4] and dipole antennas [9, 10]. These
engineering skills are based on the mechanism of
electromagnetic (EM) resonance and electrical polarization
rotation, which limits the operation bandwidth and
transmission efficiency, and the polarization direction of the
applied EM waves also has to be along a single direction. In
microwave engineering field, there is another approach to
construct subwavelength composites and Huygens’
metasurfaces, which is based on bandpass frequency
selective surface (FSS) technology [11, 12]. The physical
mechanism of such designs is based on both the electric and
magnetic responses. However, in order to acquire the full
phase-shift coverage (0~2π), stacked parallel FSSs have to
be used [13], which complicate the fabrication processes.
In this paper, we present a novel design of highly
efficient, isotropic Huygens’ metasurface, which is
composed of subwavelength metallic patterns etched on a
single-layer substrate. The equivalent magnetic current in
the middle of the metasurface unit cell is generated by
circulating, longitudinal currents supported by the metallic
sheets on both sides of the substrate, as is shown in Fig. 1(a).
These proposed structures can realize large phase coverage
and high transmission efficiency. Then, as an example to
verify the proposed metasurface unit cells, a refract-array
based on the single-layer Huygens’ metasurface is designed
and fabricated to convert normally incident EM wave to a
predefined angle from normal at the working frequency
around 25 GHz.
(a)
(b)
Figure 1. (a) 3D topology of a spatial-phase-shift unit cell and (b) the
equivalent transmission line circuit model, where periodic boundary
conditions are assumed.
978-1-4799-8766-5
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