Ultrathin active polarization-selective metasurface at X-band frequencies

In this paper, we study resource allocation design for secure communication in intelligent reflecting surface (IRS)assisted multiuser multiple-input single-output (MISO) communication systems. To enhance physical layer security, artificial noise (AN) is transmitted from the base station (BS) to deliberately impair the channel of an eavesdropper. In particular, we jointly optimize the phase shift matrix at the IRS and the beamforming vectors and AN covariance matrix at the BS for maximization of the system sum secrecy rate. To handle the resulting nonconvex optimization problem, we develop an efficient suboptimal algorithm based on alternating optimization, successive convex approximation, semidefinite relaxation, and manifold optimization. Our simulation results reveal that the proposed scheme substantially improves the system sum secrecy rate compared to two baseline schemes.

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“…Employing reflection-type amplifiers [10] driven by a common power supply, the signal reflected and amplified by the active IRS is given by…”

Section: System Modelmentioning

confidence: 99%

Resource Allocation for Secure IRS-Assisted Multiuser MISO Systems

Sun

et al. 2019

2019 IEEE Globecom Workshops (GC Wkshps)

173

135

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“…Typical metasurface-based configurations exhibit static polarization responses once the geometrical parameters are fixed, whereas dynamic control is highly desirable in many practical applications. Programmable or tunable metasurfaces [23,24] incorporating active elements (e.g., diodes, graphene, phasechange materials) can be exploited to this aim. For instance, anisotropic reflective metasurfaces [14] based on voltage-controlled varactors have been demonstrated to realize independent dualpolarization wavefront control, and transmission-type metasurfaces with dynamically tunable properties [25] have been shown to rotate the incident-wave polarization without altering its axial ratio.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Conversion of Polarization and Frequency via Time‐Division‐Multiplexing Metasurfaces

Yang

Cao

et al. 2021

Advanced Optical Materials

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Metasurfaces are artificially engineered two‐dimensional materials composed of sub‐wavelength meta‐atoms, which have shown unprecedented capabilities in manipulating the amplitude, phase, frequency, and polarization states of electromagnetic waves. Specifically, polarization control can be attained via suitable anisotropic, linear, and time‐invariant designs, while frequency conversion is realized via nonlinear or time‐varying platforms. Simultaneous manipulations of polarization and frequency would be of considerable practical interest in many application scenarios, but remain unattainable with current approaches. Here, a time‐division‐multiplexing metasurface is proposed to realize the simultaneous conversion of polarization and frequency. The platform relies on time‐modulated polarization switches and, by varying the duty cycle and time delays of the polarization channels, can arbitrarily rotate the polarization at the central frequency of operation, and synthesize various polarization states at selected harmonic frequencies. Theoretical predictions are validated via measurements on a prototype operating at microwave frequencies, providing the first experimental evidence of simultaneous polarization and frequency conversions via time‐division‐multiplexing metasurfaces. The outcomes open a new pathway in manipulating the electromagnetic waves via time‐varying metasurfaces, and may be of interest for a broad variety of applications in scenarios ranging from polarization imaging to quantum optics.

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“…Magnet-free nonreciprocal metasurfaces provide huge degrees of freedom for arbitrary alteration of the wavevector and temporal frequency of electromagnetic waves 8,12,[14][15][16][17][18][19][20][21][22][23][23][24][25] . They may be classified into two main categories, that is, space-time metasurfaces 12,17,19,21,21,23,[25][26][27][28][29] and transistor-loaded metasurfaces 8,15,[30][31][32][32][33][34] . Among these nonreciprocity approaches, transistorbased nonreciprocity is of high interest thanks to its immense capability for efficient nonreciprocal electromagnetic-wave amplification while breaking the time reversal symmetry.…”

Section: Introductionmentioning

confidence: 99%

Full-duplex Reflective Beamsteering Metasurface Featuring Magnetless Nonreciprocal Amplification

Taravati

Eleftheriades

2021

Preprint

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Nonreciprocal radiation refers to electromagnetic wave radiation in which a structure provides different response under the change of the direction of the incident field. Modern wireless telecommunication systems demand versatile apparatuses which are capable of full-duplex nonreciprocal wave processing and amplification, especially in the reflective state. Here, we propose full-duplex reflective beamsteering metasurfaces for magnetless nonreciprocal wave amplification. To realize such a unique, extraordinary and versatile functionality, we propose a completely new architecture in which a chain of series cascaded radiating patches are integrated with nonreciprocal phase shifters, providing an efficient mechanism for wave reception, signal amplification, nonmagnetic nonreciprocal phase shifting and steerable wave reflection. Having accomplished all these functionalities in the reflective state, the metasurface represents a conspicuous apparatus for efficient, controllable and programmable wave engineering for wireless telecommunications. Such an ultrathin reflective metasurface can provide directive and diverse radiation beams, and steerable beams by simply changing the bias of the gradient active nonmagnetic nonreciprocal phase shifters. The proposed structure provides large wave amplification and is immune to undesired time harmonics, yielding a highly efficient full-duplex reflective beamsteering apparatus.

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Ultrathin active polarization-selective metasurface at X-band frequencies

Cited by 35 publications

References 30 publications

Resource Allocation for Secure IRS-Assisted Multiuser MISO Systems

Resource Allocation for Secure IRS-Assisted Multiuser MISO Systems

Simultaneous Conversion of Polarization and Frequency via Time‐Division‐Multiplexing Metasurfaces

Full-duplex Reflective Beamsteering Metasurface Featuring Magnetless Nonreciprocal Amplification

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