[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Traditional methods of generating vortex beams based on metasurfaces consist mainly in modulating propagation phase or geometric phase. Here, by introducing detour phase, we propose the construction of dual-polarized vortex beam generators in the form of metasurface and metagrating (MG). The phase is modulated through moving the position of meta-atoms instead of varying the geometrical parameters or rotating the unit cells. To use detour phase, two kinds of unit cells are designed to achieve specific diffraction order. Each unit can arbitrarily and independently adjust the operation frequency and diffraction angle of transverse electric (TE) and transverse magnetic (TM) polarizations. Two vortex beam generators are designed and fabricated with different topological charges carried by orthogonal polarizations. To demonstrate the ability to independently manipulate, two polarizations of the generator based on MG are designed in different frequency bands. Both the simulation and experimental results validate the proposed method, showing great potential for polarization division multiplexing in orbital angular momentum (OAM) communication systems. 

Generating Dual-Polarized Vortex Beam by Detour Phase: From Phase Gradient Metasurfaces to Metagratings

A small size coplanar waveguide-fed dual wideband circularly polarized square slot antenna (CPSSA) is presented. It composed of an inverted C-shaped patch, grounded-L strip, a pair of grounded spiral slots and a horizontal rectangular grounded slot. The circular polarization (CP) is achieved by embedding grounded-L strip and a pair of grounded spiral slots. By engraving rectangular slot in left corner of CPW ground plane, the 3-dB axial ratio bandwidth (ARBW) of lower band is enhanced and it also generates another CP band at about 12 GHz and a notched band. From the experimental results, it is observed that the 3-dB ARBWs of the proposed antenna are 74.62% (5.01 GHz, 4.21–9.22 GHz) and 12% (1.37 GHz, 11.26–12.62 GHz) while the impedance bandwidths are 92.70% (6.48 GHz, 3.75–10.23 GHz) and 13.70% (1.63 GHz, 11.12–12.75 GHz) in lower and upper bands, respectively. The antenna has peak gain about 3.67 and 6.36 dBic in lower and upper CP bands, respectively, with good LHCP radiations. The overall size of antenna is 20 × 20 × 1 mm3.

Dual wideband circular polarized CPW-fed strip and slots loaded compact square slot antenna for wireless and satellite applications

Vortex beams have witnessed tremendous development in the past
decade by exhibiting profound implications for both fundamental physics
and a multitude of novel engineering applications. In this work, broadband
high-efficiency multiple vortex beams with independent topological modes
and inclination angles are generated leveraging an interleaved
geometric-phase multifunctional metasurface operating in a very broadband
frequency range. A set of meta-atoms are elaborately engineered to offer
broadband high-efficiency complete phase control covering the entire
2π range. Multiple geometric-phase sub-arrays implemented by the
designed meta-atoms are synthesized into one metasurface via a
shared-aperture interleaved manner, in which each sub-array can be
individually manipulated and serves as an independent channel for
launching a vortex beam. According to the established design methodology,
two vortex beams with topological modes of −1 and +2 and
distinct inclination angles are generated by one metasurface. Experimental
results are provided to corroborate the proposed mechanism for multiple
vortex beams generation, which exhibit broadband and high-efficiency
features. The presented multifunctional metasurface paves the way for the
generation of broadband high-efficiency multiple vortex beams in the
microwave, millimeter-wave and terahertz regions. This work is of
significance for high-capacity wireless communication applications,
high-efficiency manipulation of electromagnetic waves, and novel design of
radar and imaging systems.

Broadband high-efficiency multiple vortex beams generated by an interleaved geometric-phase multifunctional metasurface

Transmission–Reflection-Integrated Multiplexed Janus Metasurface

In this paper, an anisotropic holographic metasurface design is proposed, fabricated, and measured, to demonstrate that it can generate multiple beams with different orbital angular momentum (OAM) modes in the radio-frequency domain. The anisotropic holographic metasurface is composed of an array of quasi-periodic square particles with a rectangular slot in the upper metallic layer covered with a dielectric ground. The classic leaky-wave theory and a microwave holography method are introduced to construct the holograms that interfere with the surface waves excited by a monopole antenna and the objective waves represented by the desired multiple beams carrying different OAM modes. Moreover, the numerical simulations and experimental results are in very good agreement, which demonstrates the excellent performance of the design and provides a method of generating multiple OAM modes simultaneously. This lays a solid foundation for a channel-multiplexing method based on OAM-mode multiplexing to expand the capacity of wireless communication systems.

Generation of multiple beams carrying different orbital angular momentum modes based on anisotropic holographic metasurfaces in the radio-frequency domain

This communication presents a novel compact and wideband circularly polarized (CP) slot antenna fed by microstrip feedline. The proposed antenna consists of a corner-truncated square-ring slot patch and a novel bent strip. The CP radiation is formed by using the bent strip to excite CP resonance modes. By intruding several open stubs to the corners of the square-ring slot patch, the impedance matching and axial ratio (AR) bandwidth are improved. The measured results show that the proposed antenna has the advantage of wideband characteristics in terms of an impedance bandwidth of 90.59% (3.2–8.5 GHz) and 3-dB axial ratio bandwidth of 84.2% (3.3–8.1 GHz). The principle as well as simulated and measured results of the proposed antenna is revealed.

A single-layer and compact circularly polarized wideband slot antenna based on ``bent feed''

In this letter, theory concerning scattering of electromagnetic (EM) waves with orbital angular momentum (OAM) is presented, in which a metallic sphere illuminated by OAM waves is adopted to simplify the study. Based on the series expansion and the physical optics (PO) methods, expressions of incident and scattered OAM waves are obtained. To get the expansion coefficients of the scattered fields, boundary conditions and Debye potentials are applied to establish the relationship between incident and scattered fields. Besides, a full EM wave simulation of the scattered field has been accomplished by the computer simulation technology (CST), the measurement of scattered field is done in an anechoic chamber. The simulated results are in good consistency with numerical calculations, demonstrating the interaction between the OAM EM waves and the metallic target sphere effectively. This letter also paves the way for research on scattering of complex targets of OAM waves, and for future studies on target detection.

Scattering of Electromagnetic Waves With Orbital Angular Momentum on Metallic Sphere

A novel design method of harmonic suppression and size reduction of a circularly polarized (CP) microstrip patch antenna (MPA) is presented by using nondegenerate modes. Based on a circular MPA, a pair of orthogonal modes could be generated between these undesired resonant modes. Then, by loading the shorting pins in a quarter fan-shaped patch, all these undesirable high-order modes could be suppressed between them. After that, the higher and lower modes are moved closer to each other by cutting a long slot at the angle bisector of the fan-shaped patch, providing the CP radiation pattern. Finally, a prototype of this proposed antenna has been designed, produced, and measured to verify the design concept. The experimental results show that the proposed antenna has an impedance bandwidth of 286 MHz (13 774–14 060 MHz), axial ratio bandwidth of 80 MHz (13 900–13 980 MHz), and a left-hand CP peak gain of around 4.8 dBi. Most importantly, the CP antenna has realized the harmonic suppression of about 15 GHz, which has an obvious advantage as compared to the traditional CP MPA. Moreover, the antenna still holds the primary low-profile, single-radiator, simple structure, and high-efficiency simultaneously.

Harmonic Suppression and Size Reduction of a Low-Profile CP Patch Antenna by Using Nondegenerate Modes

Erratum: “Generation of multiple beams carrying different orbital angular momentum modes based on anisotropic holographic metasurfaces in the radio-frequency domain” [Appl. Phys. Lett. 114, 093504 (2019)]

Zhe Wu

Papers

Generation of multiple beams carrying different orbital angular momentum modes based on anisotropic holographic metasurfaces in the radio-frequency domain

A single-layer and compact circularly polarized wideband slot antenna based on ``bent feed''

Scattering of Electromagnetic Waves With Orbital Angular Momentum on Metallic Sphere

Harmonic Suppression and Size Reduction of a Low-Profile CP Patch Antenna by Using Nondegenerate Modes

Erratum: “Generation of multiple beams carrying different orbital angular momentum modes based on anisotropic holographic metasurfaces in the radio-frequency domain” [Appl. Phys. Lett. 114, 093504 (2019)]