Synthesis of Passive Lossless Metasurfaces Using Auxiliary Fields for Reflectionless Beam Splitting and Perfect Reflection

Epstein, Ariel; Eleftheriades, George V.

doi:10.1103/physrevlett.117.256103

Cited by 308 publications

(242 citation statements)

References 31 publications

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“…To ensure maximum signal reflection, existing works on RIS-assisted systems set α = 1, justifying this choice with the significant research progress made on the development of lossless metasurfaces that can achieve unity reflection magnitude with arbitrary reflection phase [25]- [28].…”

Section: A Signal Modelmentioning

confidence: 99%

Asymptotic Max-Min SINR Analysis of Reconfigurable Intelligent Surface Assisted MISO Systems

Nadeem

Kammoun

Chaaban

et al. 2020

IEEE Trans. Wireless Commun.

466

426

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This work focuses on the downlink of a single-cell multi-user system in which a base station (BS) equipped with M antennas communicates with K single-antenna users through a reconfigurable intelligent surface (RIS) installed in the line-of-sight (LoS) of the BS. RIS is envisioned to offer unprecedented spectral efficiency gains by utilizing N passive reflecting elements that induce phase shifts on the impinging electromagnetic waves to smartly reconfigure the signal propagation environment.We study the minimum signal-to-interference-plus-noise ratio (SINR) achieved by the optimal linear precoder (OLP), that maximizes the minimum SINR subject to a given power constraint for any given RIS phase matrix, for the cases where the LoS channel matrix between the BS and the RIS is of rank-one and of full-rank. In the former scenario, the minimum SINR achieved by the RIS-assisted link is bounded by a quantity that goes to zero with K. For the high-rank scenario, we develop accurate deterministic approximations for the parameters of the asymptotically OLP, which are then utilized to optimize the RIS phase matrix. Simulation results show that RISs can outperform half-duplex relays with a small number of passive reflecting elements while large RISs are needed to outperform full-duplex relays.

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Section: A Signal Modelmentioning

confidence: 99%

Asymptotic Max-Min SINR Analysis of Reconfigurable Intelligent Surface Assisted MISO Systems

Nadeem

Kammoun

Chaaban

et al. 2020

IEEE Trans. Wireless Commun.

466

426

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“…For this purpose, we use a synthesis method based on generalized Snell's laws which intuitively allows for arbitrary control of reflected and transmitted waves through local phase shifts at the metasurface. It should be mentioned that this synthesize method suffers in terms of power efficiency due to spurious scattering and it has been recently found that the ideal required phase shift differs from the prescription of the generalized Snell's law [77][78][79]. However, due to the 2π phase span provided by the proposed design paradigm, it can be used flexibly in more sophisticated synthesis methods to improve the efficiency of functionality.…”

Section: Wavefront Engineering Of Generated Frequency Harmonicsmentioning

confidence: 99%

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

2018

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Modulation of metasurfaces in time gives rise to several exotic space-time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a timemodulated metasurface which is linearly proportional to the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonant regime. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2π span in the wavefronts of generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Teraherz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links with large isolations via modulationinduced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality.

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“…Based on this approach, however, transforming an incident wave towards an arbitrary direction with unitary efficiency in general requires locally active or strongly non-local metasurfaces [18]- [19]. Using the interference with auxiliary evanescent modes [23] or leaky modes [24], one can engineer passive impedance profiles that emulate the required non-local effects and get close to unitary efficiency. Such metasurfaces, however, are still subject to implementation difficulties when the limited fabrication resolution are considered, since they also require the discretization of a continuous, fastly varying, impedance profile.…”

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confidence: 99%

Metagratings: Beyond the Limits of Graded Metasurfaces for Wave Front Control

2017

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Graded metasurfaces exploit the local momentum imparted by an impedance gradient toMetasurfaces are thin structured arrays that have attracted significant attention for the level of control of electromagnetic waves that they enable [1]- [6]. Phase-gradient metasurfaces, in particular, have recently been explored to tailor the electromagnetic wavefront in unprecedented ways to realize low-profile lenses, holograms, beam steerers and other ultrathin optical devices.

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Synthesis of Passive Lossless Metasurfaces Using Auxiliary Fields for Reflectionless Beam Splitting and Perfect Reflection

Cited by 308 publications

References 31 publications

Asymptotic Max-Min SINR Analysis of Reconfigurable Intelligent Surface Assisted MISO Systems

Asymptotic Max-Min SINR Analysis of Reconfigurable Intelligent Surface Assisted MISO Systems

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

Metagratings: Beyond the Limits of Graded Metasurfaces for Wave Front Control

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