Article
Computer Science, Hardware & Architecture
Zhiqiang Wei, Weijie Yuan, Shuangyang Li, Jinhong Yuan, Ganesh Bharatula, Ronny Hadani, Lajos Hanzo
Summary: The article introduces a recently proposed OTFS modulation scheme, which accommodates wireless communication in high-mobility scenarios, highlighting its advantages and potential applications.
IEEE WIRELESS COMMUNICATIONS
(2021)
Article
Computer Science, Information Systems
Yang Sun, J. Andrew Zhang, Kai Wu, Ren Ping Liu
Summary: In this paper, a frequency-domain sensing framework is proposed for OFDM JCAS systems to address the interference caused by large Doppler frequencies. The framework includes intra-block and inter-block sensing algorithms, exemplified pilot design, and periodogram sensing algorithm. Simulation results show the effectiveness of the proposed framework.
IEEE WIRELESS COMMUNICATIONS LETTERS
(2023)
Article
Computer Science, Information Systems
Yong Xu, Ran Sui, Junjie Wang, Dejun Feng
Summary: This paper discusses the possibility of using active frequency selective surface (AFSS) in the generation of multiple virtual targets and proposes an ISAR image modulation method.
Article
Engineering, Electrical & Electronic
Heeje Han, Soonwoo Park, Hongwoo Park, Hongjoon Kim
Summary: By utilizing varactor diodes in a metasurface, the reflection frequency can be modulated widely with up to a 1 MHz variation, resulting in a best spurious-free dynamic range of 20.7 dBc.
IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS
(2022)
Article
Chemistry, Analytical
Tian-Ci Yang, Ye Zhao, Guo-Shan Wu, Xin-Cheng Ren
Summary: This study numerically investigates the Doppler spectra of time-varying Kelvin wake on a time-varying sea surface, providing a reference for extracting motion features of ship wakes in a sea clutter environment. By establishing a linear superposition model and combining it with the facet scattering field model and Kirchhoff approximation, the changes in the Doppler spectra under different conditions were simulated and analyzed.
Article
Engineering, Electrical & Electronic
Jian Pan
Summary: This paper provides an exact and detailed formulation of the discrete-time system model for non-ideal pulse-shaping OTFS, and derives the CRLB of channel estimation for SCP-OTFS, MCP-OTFS, and MCPA-OTFS cases. This sets a benchmark for different channel estimation algorithms in high-mobility communication scenarios where OTFS is expected to outperform OFDM.
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2021)
Review
Optics
Emanuele Galiffi, Romain Tirole, Shixiong Yin, Huanan Li, Stefano Vezzoli, Paloma A. Huidobro, Mario G. Silveirinha, Riccardo Sapienza, Andrea Alu, J. B. Pendry
Summary: This review comprehensively discusses the recent progress of time modulation in photonic metamaterials, including temporal switching, photonic time-crystals, and spatiotemporal modulation. It also reviews and provides perspectives on the applications of time modulation in nonreciprocity, synthetic motion, giant anisotropy, etc.
ADVANCED PHOTONICS
(2022)
Article
Engineering, Electrical & Electronic
Kuntal Deka, Anna Thomas, Sanjeev Sharma
Summary: This paper proposes a multi-user OTFS system based on SCMA technique, and validates its performance through simulations and comparisons.
IEEE TRANSACTIONS ON COMMUNICATIONS
(2021)
Article
Physics, Multidisciplinary
Franz Lampel, Hamdi Joudeh, Alex Alvarado, Frans M. J. Willems
Summary: In OTFS modulation, symbols are placed in the delay-Doppler domain, allowing for time-invariant communication in high-mobility scenarios. This study proposes an OTFS system based on the discrete Zak transform, which simplifies derivation and analysis and shows that operating in the DD domain does not result in capacity loss.
Article
Engineering, Electrical & Electronic
Qiao Li, Zheng Xiang, Peng Ren, Wanlu Li
Summary: This paper presents a variational autoencoder (VAE) based receiver for OTFS modulation, achieving joint estimation and detection without pilot in delay-Doppler (DD) domain. The variational approach simplifies the problem and derives the evidence lower bound (ELBO) as the loss function, optimizing channel estimation process.
DIGITAL SIGNAL PROCESSING
(2021)
Article
Engineering, Electrical & Electronic
Luping Xiang, Yusha Liu, Lie-Liang Yang, Lajos Hanzo
Summary: Message passing aided detectors are designed for OTFS modulated system, with a joint factor graph designed to characterize the transmit-receive relationship in the DD domain. A novel GA-MP detector, modeling a posteriori probabilities through Gaussian distributions, outperforms state-of-the-art MP detector by at least 1.5 dB at a BER of 10^(-4).
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2021)
Article
Engineering, Electrical & Electronic
Junjie Wang, Dejun Feng, Yameng Kong, Sinong Quan, Shiqi Xing
Summary: In this article, a nonperiodic time-varying active frequency selective surface (AFSS) is proposed to manipulate the spectral distribution of harmonics. The validity of the proposed method is verified through radar imaging experiments.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2022)
Article
Physics, Applied
D. Ramaccia, A. Alu, A. Toscano, F. Bilotti
Summary: Temporal metamaterials are artificial materials with electromagnetic properties that change over time, allowing for the realization of non-homogeneous temporal media or stepwise transitions. By modeling wave propagation through a generalized temporal multilayer structure, higher-order transfer functions can be synthesized, enabling the design of novel electromagnetic and optical devices with tailored scattering responses. This approach leverages the temporal dimension instead of the spatial dimension typically used in optical and electromagnetic multilayered structures.
APPLIED PHYSICS LETTERS
(2021)
Article
Engineering, Electrical & Electronic
Grigorii Ptitcyn, Mohammad Sajjad Mirmoosa, Amirhosein Sotoodehfar, Sergei A. Tretyakov
Summary: In recent years, there has been increasing interest in using time-modulation techniques to realize new phenomena and create new applications by varying system properties. This field, which originated in the middle of the previous century, has gained revitalized attention. In this tutorial article, the authors provide a historical overview and review the basic concepts in this field. They introduce the general theory of linear time-varying systems, discuss accounting for frequency dispersion in nonstationary systems, and elucidate models of time-varying electrical circuits and materials.
IEEE ANTENNAS AND PROPAGATION MAGAZINE
(2023)
Article
Engineering, Electrical & Electronic
Saif Khan Mohammed
Summary: The paper rigorously derives Orthogonal Time Frequency Space (OTFS) modulation using the ZAK representation, providing robustness to channel induced Doppler shift. The received basis signals in the delay-Doppler (DD) domain are localized, reducing interference and allowing for joint equalization of information symbols. Compared to OFDM, DD domain modulation exhibits better robustness to channel induced Doppler shift.
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
Nikita Nefedkin, Ahmed Mekawy, Jonas Krakofsky, Yongrui Wang, Alexey Belyanin, Mikhail Belkin, Andrea Alu
Summary: Engineered intersubband transitions in multi-quantum well semiconductor heterostructures exhibit high second-order nonlinear susceptibilities in metasurfaces. By optimizing the design, the saturation limits in mid-infrared frequency upconversion in nonlinear metasurfaces are significantly extended. This has important implications for night-vision imaging and compact nonlinear wave mixing systems.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Julian Klein, Zhigang Song, Benjamin Pingault, Florian Dirnberger, Hang Chi, Jonathan B. Curtis, Rami Dana, Rezlind Bushati, Jiamin Quan, Lukas Dekanovsky, Zdenek Sofer, Andrea Alu, Vinod M. Menon, Jagadeesh S. Moodera, Marko Loncar, Prineha Narang, Frances M. Ross
Summary: Atomic-level defects in van der Waals (vdW) materials are essential for quantum technologies and sensing applications. The magnetic semiconductor CrSBr, with a direct gap and rich magnetic phase diagram, exhibits optically active defects that are correlated with the magnetic environment. The narrow defect emission in CrSBr is related to both the bulk magnetic order and an additional defect-induced magnetic order. This study establishes vdW magnets like CrSBr as an exceptional platform for studying defects and creating tailor-made magnetic textures with optical access.
Article
Physics, Applied
X. Fang, M. Li, D. Ramaccia, A. Toscano, F. Bilotti, D. Ding
Summary: Self-adaptive retro-reflective planar Doppler cloak is designed to compensate the Doppler effect of a moving scatterer and maintain a stable radar cross section. It uses space-time modulated metasurfaces for frequency conversion and retro-reflection. This self-adaptive Doppler cloak enhances the undetectability of cloaked moving objects.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
L. Stefanini, D. Ramaccia, A. Toscano, F. Bilotti
Summary: In this Letter, a rainbow-like scattering process is reported at the interface of a boundary-induced temporal metamaterial realized by instantaneously opening the boundary conditions of a parallel plate waveguide. By changing the conductivity of one of the metallic plates, an equivalent temporal interface between two different media is created, and the monochromatic wave propagating into the waveguide gets scattered into a polychromatic rainbow in free space. The relationships between the waveguide mode and the raising rainbow are derived, and the underlying physics is applied to control the temporal rainbow by design.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Alessio Monti, Stefano Vellucci, Mirko Barbuto, Davide Ramaccia, Michela Longhi, Claudio Massagrande, Alessandro Toscano, Filiberto Bilotti
Summary: Recently, the use of deflecting covering meta-domes has been suggested to increase the scanning range of phased arrays. However, this solution has inherent limitations including significant reduction in broadside gain and the complexity of implementation due to the need for continuous phase profile. In this work, technical solutions are proposed to maximize meta-dome performance and reduce gain loss at broadside by discretizing and engineering the phase profile along the dome and considering the different angles of incidence on the meta-cells.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2023)
Article
Nanoscience & Nanotechnology
Guangwei Hu, Weiliang Ma, Debo Hu, Jing Wu, Chunqi Zheng, Kaipeng Liu, Xudong Zhang, Xiang Ni, Jianing Chen, Xinliang Zhang, Qing Dai, Joshua D. Caldwell, Alexander Paarmann, Andrea Alu, Peining Li, Cheng-Wei Qiu
Summary: Various optical crystals with opposite permittivity components have been observed and characterized in the mid-infrared regime. These crystals possess hyperbolic polaritons with large-momenta optical modes and wave confinement, making them promising for nanophotonic on-chip technologies. Monoclinic CdWO4 crystals are shown to exhibit symmetry-broken hyperbolic phonon polaritons and offer new opportunities for polaritonic phenomena.
NATURE NANOTECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
Andrea Cordaro, Brian Edwards, Vahid Nikkhah, Andrea Alu, Nader Engheta, Albert Polman
Summary: As traditional microelectronic technology reaches its limits in speed and power consumption, there is a strong demand for novel computing strategies. Analogue optical computing has the advantage of processing large amounts of data at high speeds with negligible energy costs. Researchers have recently explored ultrathin optical metasurfaces for real-time image processing, particularly for edge detection. By incorporating feedback, they have also demonstrated that metamaterials can be used to solve complex mathematical problems, although this has been limited to guided-wave systems and large setups. This study presents an ultrathin Si metasurface-based platform for analogue computing, capable of solving Fredholm integral equations of the second kind using free-space visible radiation. The device combines an inverse-designed Si-based metagrating with a semitransparent mirror to perform the required Neumann series and solve the equation in the analogue domain at the speed of light. The use of visible wavelength operation enables a compact, ultrathin device that can be integrated on a chip and has high processing speeds.
NATURE NANOTECHNOLOGY
(2023)
Editorial Material
Materials Science, Multidisciplinary
Andrea Alu
Summary: Optical Materials Express Editor-in-Chief, Andrea Ali, has introduced new topic categories for the Journal, redefining the Journal scope and better reflecting the current state of this dynamic field of research.
OPTICAL MATERIALS EXPRESS
(2023)
Article
Nanoscience & Nanotechnology
Nikita Nefedkin, Michele Cotrufo, Andrea Alu
Summary: Nonreciprocity originating from classical interactions among nonlinear scatterers is explored in this work, offering a promising tool for quantum information processing and quantum computing. It is shown that large nonreciprocal responses can be achieved in nonlinear systems by controlling the position and transition frequencies of the atoms, without requiring a nonreciprocal environment. The connection between this effect and the asymmetric population of a slowly decaying dark state is demonstrated.
Article
Engineering, Electrical & Electronic
Samiran Pramanik, Saikat Chandra Bakshi, Chaitali Koley, Debasis Mitra, Alessio Monti, Filiberto Bilotti
Summary: We develop a new concept of three-states polarization converting metasurface (TS-PCM) based on p-i-n diodes. The proposed structure can achieve three distinct wave manipulation functionalities: linear polarization to orthogonal linear polarization (LP-OLP), linear polarization to circular polarization (LP-CP), and linear polarization to full reflection (LP-FR) state. Unlike previous structures, these conversion features are simultaneously achieved in different frequency ranges based on the on/off state of diode. Experimental results from a fabricated prototype match well with the simulated ones.
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Mirko Barbuto, Andrea Alu, Filiberto Bilotti, Alessandro Toscano
Summary: To achieve a smart electromagnetic environment, researchers propose a new design strategy to add reconfigurability to reflective metasurfaces, enabling the implementation of reconfigurable intelligent surfaces. By controlling the scattering pattern of reflective metasurfaces, the complexity of the control system is reduced, resulting in a more practical solution.
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Samiran Pramanik, Saikat Chandra Bakshi, Chaitali Koley, Debasis Mitra, Alessio Monti, Filiberto Bilotti
Summary: We propose a new metasurface-based wideband polarization converter with a switchable notch band. Unlike previous structures, our design utilizes the properties of p-i-n diodes to provide switchable functionalities between single/dual-frequency bands. The structure converts incident linearly polarized plane waves into orthogonally linearly polarized waves in different frequency ranges depending on the state of the diodes. The notch band within the structure can be exploited for stealth antenna applications due to its LP-full reflection behavior.
IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY
(2023)
Article
Engineering, Electrical & Electronic
Emanuele Maiorana, Davide Ramaccia, Luca Stefanini, Alessandro Toscano, Filiberto Bilotti, Patrizio Campisi
Summary: In this article, the feasibility of using electromagnetic scattering to recognize users is evaluated. A recognition framework that utilizes X-band antennas and measured scattering parameters is proposed. Results show that this approach can be used to implement a robust biometric system or enhance recognition performance when combined with other hand characteristics.
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
(2023)
