Broadband and wide-angle RCS reduction using a 2-bit coding ultrathin metasurface at terahertz frequencies

Liu, Liang; Wei, Minggui; Yan, Xin; Wei, Dequan; Liang, Dachuan; Han, Jiaguang; Ding, Xin; Zhang, GaoYa; Yao, Jianquan

doi:10.1038/srep39252

Cited by 56 publications

(32 citation statements)

References 36 publications

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“…The reader is referred to refs. for a representative (but nonexhaustive) sample of recent studies on digital metasurfaces. Among the most prominent applications, besides the aforementioned RCS control, particularly worth of mention are those to field shaping in reverberating scenarios, computational imaging, and dynamic control of polarization, wavefront and scattering signature, as well as of information entropy .…”

Section: Introductionmentioning

confidence: 99%

Coding Metasurfaces for Diffuse Scattering: Scaling Laws, Bounds, and Suboptimal Design

Moccia

Liu

et al. 2017

Advanced Optical Materials

141

110

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and/or polarization) via the engineering of metallic or dielectric resonating elements suitably arranged on a 2D surface. Indeed, their inherent 2D character has played a major catalyzing role, by considerably simplifying the fabrication process, as opposed to "bulk" 3D metamaterials. [4] The reader is referred to refs. [5-9] (and references therein) for recent reviews on the modeling, design, and attainable physical effects, as well as the abundant applications, ranging from wavefront shaping and beam-forming to chemical and biological sensing.Of specific interest for the present study is the concept of "coding and digital" metasurfaces, recently put forward by Cui et al. [10] (see also ref. [11] for an analogous concept applied to bulk metamaterials), which relies on the exploitation of a limited number of element-types (unit cells). In its simplest form, only two elementtypes (labeled as "1" and "0") are employed, so that the metasurface design can be effectively associated with a 2D binary coding. This can be viewed, in a sense, as an evolution of the "checkerboard-surface" concept originally conceived by Paquay et al. [12] As implied by the name, the basic idea underlying a checkerboard surface is to alternate two types of unit cells (e.g., metallic and artificial-magnetic-conducting, at microwave frequencies) characterized by out-of-phase reflection coefficients, so as to suppress the specular reflection in view of the inherent cancellation effects. With suitable extensions and modifications of the unit cells as well as the spatial arrangement, this basic concept has been exploited in several subsequent studies [13][14][15][16][17][18] in order to attain broadband and wide-angle reduction of the radar cross-section (RCS) of planar surfaces.Within this framework, the digital-metasurface concept [10] introduces further levels of sophistication. First, the spatial arrangement (described by a coding) of the unit cells is far more general and flexible. Further versatility can be introduced by employing more than two unit cells, corresponding to multibit coding. Most important, by exploiting reconfigurable unit cells (whose response can be switched, e.g., by means of a biased diode or a microelectromechanical system), the coding is no longer irreversibly bound to the structure design, but can be controlled, e.g., via a field-programmable gate array. To date, this represents one of the first working examples of a programmable metamaterial platform for field manipulation and Coding metasurfaces, based on the combination of two basic unit cells with out-of-phase responses, have been the subject of many recent studies aimed at achieving diffuse scattering, with potential applications to diverse fields ranging from radar-signature control to computational imaging. Here, via a theoretical study of the relevant scaling-laws, the physical mechanism underlying the scattering-signature reduction is elucidated, and some absolute and realistic bounds are analytically derived. Moreover, a simple, deterministic suboptimal desi...

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Section: Introductionmentioning

confidence: 99%

Coding Metasurfaces for Diffuse Scattering: Scaling Laws, Bounds, and Suboptimal Design

Moccia

Liu

et al. 2017

Advanced Optical Materials

141

110

View full text Add to dashboard Cite

show abstract

“…The digital coding representation links the traditional metamaterials to information theory, giving us an opportunity to control EM performance through discrete digital states. Based on these concepts, many kinds of functions such as beam steering and reduction of radar cross‐sections have been achieved by switching coding sequences on coding metamaterials in microwave and terahertz regions. Recently, the concept of anisotropic coding metamaterials has been demonstrated, which can achieve two independent coding behaviors for different polarizations .…”

Section: Introductionmentioning

confidence: 99%

“…In the existing work on coding metamaterials, however, all digital codes come from the absolute values of scattering phase ϕ. Here, according to the expression of EM waves from Maxwell's equations and wave equations, we propose a novel principle for digital codes, which relates to the complex phase term e jϕ instead of ϕ itself.…”

Section: Introductionmentioning

confidence: 99%

Addition Theorem for Digital Coding Metamaterials

Shi

Liu

et al. 2018

Advanced Optical Materials

165

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Recently, 2D versions of metamaterials, metasurfaces, have attracted more attention, [11] due to their advantages of low cost, low profile, and strong abilities to manipulate spatial and surface waves. Novel generalized sheet transition condition method [12] and transverse resonance method [13] were first presented to analyze the EM performance of metasurfaces. Then generalized Snell's law [14] was proposed to introduce the concept of abrupt phase when designing metasurfaces. By changing the size, shape, or orientation of unit cells, the abrupt phase provided by the metasurface can be tailored accordingly, and the outgoing EM waves are engineered arbitrarily. Metasurfaces have offered more convenience and freedom for manipulating EM wavefronts, and have been widely applied in the microwave, [15][16][17][18][19][20] terahertz, [21][22][23][24] visible, [25][26][27][28] and even acoustic [29,30] frequencies.Metamaterials and metasurfaces described by continuously effective medium parameters and phase distributions have powerful capabilities in controlling EM waves, but in static ways. That is to say, once a metamaterial or metasurface is fabricated, its function will be fixed. In order to reach real-time controls to EM waves, digital coding characterization has been proposed to describe metamaterial, resulting in the concepts of coding, digital, and programmable metamaterials. [31] The binary 1-bit digital codes "0" and "1" are adopted to indicate the reflection phases of 0° and 180°, from which one can manipulate EM waves using different coding sequences. The digital codes have been extended to 2-bit and more to bring more freedom for controlling scattering beams. The digital states "0." "1," "2," and "3" represent the reflection phases of 0°, 90°, 180°, and 270°, respectively.By designing a unit cell controllable by a diode to achieve either "0" or "1" state, the digital and programmable metamaterials have been realized to reach real-time manipulations to EM waves. [31] The digital coding representation links the traditional metamaterials to information theory, giving us an opportunity to control EM performance through discrete digital states. Based on these concepts, many kinds of functions such as beam steering [31][32][33] and reduction of radar crosssections [34] have been achieved by switching coding sequences on coding metamaterials in microwave and terahertz regions. Recently, the concept of anisotropic coding metamaterials has been demonstrated, which can achieve two independent coding behaviors for different polarizations. [35] Furthermore, convolution operations on coding metasurfaces were presented to 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 geometr...

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“…In this context, Cui et al provided an analytic model that allows the computation of the backscatter far-field by considering the coding metasurface as a passive antenna array [3]. This approach was used and step-wise improved in recent years [14][15][16]. Yet, the calculations have only accounted for backscattering of waves that were normally incident on the metasurface.…”

Section: Introductionmentioning

confidence: 99%

Analysis of coding metasurfaces for incident radiation at oblique incidence angles

Kappa¹,

Dang²,

Sokoluk³

et al. 2019

OSA Continuum

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Radar cross section reducing (RCSR) metasurfaces or coding metasurfaces were primarily designed for normally incident radiation in the past. It is evident that the performance of coding metasurfaces for RCSR can be significantly improved by additional backscattering reduction of obliquely incident radiation, which requires a valid analytic conception tool. Here, we derive an analytic current density distribution model for the calculation of the backscatter far-field of obliquely incident radiation on a coding metasurface for RCSR. For demonstration, we devise and fabricate a metasurface for a working frequency of 10.66 GHz and obtain good agreement between the measured, simulated, and analytically calculated backscatter far-fields. The metasurface significantly reduces backscattering for incidence angles between −40 • and 40 • in a spectral working range of approximately 1 GHz.

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Broadband and wide-angle RCS reduction using a 2-bit coding ultrathin metasurface at terahertz frequencies

Cited by 56 publications

References 36 publications

Coding Metasurfaces for Diffuse Scattering: Scaling Laws, Bounds, and Suboptimal Design

Coding Metasurfaces for Diffuse Scattering: Scaling Laws, Bounds, and Suboptimal Design

Addition Theorem for Digital Coding Metamaterials

Analysis of coding metasurfaces for incident radiation at oblique incidence angles

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