In this paper, we report dispersion-engineered metasurfaces with distinct functionalities controlled by wavelength. Unlike previous approaches based on spatial multiplexing or vertical stacking of metasurfaces, we utilize a single phase profile with wavelength dependence encoded in the phase shifters’ dispersion. We designed and fabricated a multiwavelength achromatic metalens (MAM) with achromatic focusing for blue (B), green (G), yellow (Y), and red (R) light and two wavelength-controlled beam generators (WCBG): one focuses light with orbital angular momentum (OAM) states (l = 0,1,2) corresponding to three primary colors; the other produces ordinary focal spots (l = 0) for red and green light, while generating a vortex beam (l = 1) in the blue. A full color (RGB) hologram is also demonstrated in simulation. Our approach opens a path to applications ranging from near-eye displays and holography to compact multiwavelength beam generation.

Single-Layer Metasurface with Controllable Multiwavelength Functions

Coding representation of metamaterials builds up a bridge between the physical world and the digital world, making it possible to manipulate electromagnetic (EM) waves by digital coding sequences and reach field‐programmable metamaterials. Here, the coding space is extended to complex domain and proposed complex digital codes to provide closer essence of EM‐wave propagation. Based on the analytic geometry and complex variable functions, an addition theorem on complex coding is established, which reveals inherent connections among digital codes with different bits and enables all higher‐bit digital codes to be represented by the 1‐bit complex codes. According to the complex coding and addition theorem, multifunctional metamaterials can be directly designed and realized without considering mutual coupling. When two different coding patterns with different functions are added together via the addition theorem in complex form, the combined coding pattern will directly generate the two functions simultaneously without any perturbations. A series of realistic coding metasurfaces is presented to demonstrate the powerful and flexible performance of the complex coding and addition theorem for independent controls of EM waves to reach multiple functions. Good agreements between numerical simulations and experimental results prove the feasibility of the proposed concept and theorem in practical applications.

Addition Theorem for Digital Coding Metamaterials

Metasurfaces, the two-dimensional counterpart of metamaterials, have caught great attention thanks to their powerful capabilities on manipulation of electromagnetic waves. Recent times have seen the emergence of a variety of metasurfaces exhibiting not only countless functionalities, but also a reconfigurable response. Additionally, digital or coding metasurfaces have revolutionized the field by describing the device as a matrix of discrete building block states, thus drawing clear parallelisms with information theory and opening new ways to model, compose, and (re)program advanced metasurfaces. This paper joins the reconfigurable and digital approaches, and presents a metasurface that leverages the tunability of graphene to perform beam steering at terahertz frequencies. A comprehensive design methodology is presented encompassing technological, unit cell design, digital metamaterial synthesis, and programmability aspects. By setting up and dynamically adjusting a phase gradient along the metasurface plane, the resulting device achieves beam steering at all practical directions. The proposed design is studied through analytical models and validated numerically, showing beam widths and steering errors well below 10° and 5% in most cases. Finally, design guidelines are extracted through a scalability analysis involving the metasurface size and number of unit cell states.

/pdf/digital-metasurface-based-on-graphene-an-application-to-beam-jdqrxspncq.pdf

Digital Metasurface Based on Graphene: An Application to Beam Steering in Terahertz Plasmonic Antennas

We propose a low-profile broadband planar circularly polarized folded transmitarray antenna (CPFTA) based on well-designed top and bottom metasurfaces (MSs). The top MS is employed to reflect the $x$ -polarized wave as a ground and, at the same time, to convert the $y$ -polarized wave into circularly polarized waves with arbitrary phase shifts in the operation band. A bottom MS is applied to reflect the incident wave and twist its polarization by 90°. The whole CPFTA, including the feeding source of microstrip antenna, and the top and bottom MSs can be fully integrated and fabricated using low-cost printed circuit board technology. Both simulated and measured results demonstrate significant advantages of the proposed antenna, including broad bandwidth, high gain, lower profile, planar geometry, and easy integration. The fabricated sample shows 3 dB axial ratio (AR) bandwidth of 23.2%, 3 dBi gain bandwidth of 11.6%, and the maximum gain of 22.8 dBi at 10.3 GHz with the antenna efficiency of 21.8%. The proposed CPFTA is promising for applications in satellite communications with circularly polarized antennas.

Folded Transmitarray Antenna With Circular Polarization Based on Metasurface

The advancement in the current communication technology makes it incumbent to analyze the conventional features of reflectarray antenna for future adaptability. This paper thoroughly reviews the design and experimental features of reflectarray antenna for its bandwidth improvement in microwave and millimeter wave frequency ranges. The paper surveys the fundamental and advanced topologies of reflectarray design implementations, which are needed particularly for its broadband features. The realization of its design approaches has been studied at unit cell and full reflectarray levels for its bandwidth enhancement. Various design configurations have also been critically analyzed for the compatibility with the high-frequency 5G systems.

A Review of Wideband Reflectarray Antennas for 5G Communication Systems

A wideband folded reflectarray antenna (FRA) operating in a frequency band of 11–15 GHz is proposed in this communication. It consists of novel dual-polarization elements with high orthogonal polarization isolation. A two-layer element structure is used to control the reflection phase of two orthogonally polarized waves independently and the element presents a large phase variation of about 700° and approximately linear phase curves. Meanwhile, the multifrequency phase matching method is applied in the FRA design. A 30% bandwidth for a 1-dB gain drop, a peak aperture efficiency of 49.1%, and sidelobe levels below −14 dB are achieved. Factors with strong influences on the aperture efficiency are discussed. The simulated results are experimentally verified by an FRA prototype fed by an open-ended waveguide.

Wideband Folded Reflectarray Using Novel Elements With High Orthogonal Polarization Isolation

A novel single-layer reflectarray element with three resonances, showing a linear phase curve and a large phase variation range over 800° is proposed for a broadband operation. Different size of elements are selected by using a simple guideline to achieve the required phase distribution in a given frequency band. Two offset-fed 10 × 10 reflectarrays with different scattering angles are designed. Simulations and measurements show the bandwidth of 28% for a 3-dB gain drop and 44% for −10-dB side lobe level inspite of the large F/D of 2.1. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:950–954, 2014

Single‐layer reflectarray with novel elements for wideband applications

The invention discloses a frequency-control wave beam/focal point scanning plane reflective array/reflector. The basic structure of the plane reflective array and the basic structure of the reflector respectively comprise a printed patch array, a primary feed source and a corresponding supporting structure. The plane reflective array is irradiated by spherical waves, focusing of wave beams is realized in a far field, and the plane reflective array can be used in a modern wireless communication system and a modern radar system. The reflector is irradiated by plane waves or cylindrical waves or spherical waves, can realize wave beam focusing in a near field and can be applied to an imaging system. The plane reflective array and the reflector respectively enable the phase value actually obtained on each frequency point to meet the theoretically required value through selection of the size and freedom degree parameters of each unit, therefore, in-phase superposition, in different directions, of the array at different frequency points is realized, and the function of wave beam or focal point scanning is achieved. The frequency-control wave beam/focal point scanning plane reflective array/reflector has the advantages that electric wave beam/focal point scanning and high gain are realized through the simple array surface structure, and the cost, the loss and the complexity of a current scanning array/imaging system are greatly reduced.

Frequency-control wave beam/focal point scanning plane reflective array/reflector

The invention discloses an electronic control beam scanning reflection array antenna and a beam scanning method thereof. The antenna is low in cost and loss and simple in structure. The antenna is characterized in that two initial feed sources are adopted in the antenna to perform irradiation excitation on a reflective array plane, and the excitation amplitude ratio of the feed source 1 to the feed source 2 is changed to change the phase value distribution of a total incident field in the array plane so that electronic control beam scanning can be achieved. The antenna is simple in structure and does not need extra biasing circuits, so that machining is convenient, and stability is high. High-gain beam scanning can be achieved just through the two initial feed sources without extra T/R modules, so that the manufacturing cost is effectively lowered. The antenna is suitable for microwave or millimeter wave or terahertz frequency bands and can be used in wireless communication and radar systems.

Electronic control beam scanning reflection array antenna and beam scanning method thereof

The invention discloses a broadband foldable reflective array antenna, and belongs to the technical field of antennas. The broadband foldable reflective array antenna employs a foldable reflective array antenna structure, and provides a brand new reflective array unit, so that the foldable reflective array of the reflective array unit solves the problem that breakthrough on gain bandwidth of a conventional foldable reflective array antenna is hard to achieve. The characteristics of high gain, low loss, compact structure and low cross polarization of a foldable reflective array antenna are fully explored. The broadband foldable reflective array antenna is suitable for microwave, millimeter wave, THz frequency ranges and applicable to high performance communication or radar systems.

Broadband foldable reflective array antenna

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