arXiv subjects

Amir Boag

Publications and source records attributed to Amir Boag.

17 recordsLinked to original sources

arXiv2026

A Methodology for Characterizing Underwater Radiated Noise from Submerged Electric Vehicles in a Coastal Environment: An AUV Test Case

Submerged electric vehicles (SEVs), including autonomous underwater vehicles (AUVs), remotely operated vehicles, and diver propulsion systems, may radiate distinct tonal, harmonic, and modulated acoustic components associated with electric propulsion drives and motor-control electronics. Characterizing these signatures is relevant to passive detection and engineering diagnostics, but remains challenging in coastal environments because ambient noise, shallow-water propagation, and aspect-dependent radiation can obscure vehicle-related features. Existing underwater radiated noise (URN) standards, developed primarily for surface vessels, do not address the spectral, operational, and geometric complexity of SEV measurements. This paper presents an eight-step methodology for SEV URN characterization, covering measurement design, cavitation assessment, frequency-band selection, ambient-noise characterization, spectral and time-frequency analysis, subsystem-oriented interpretation, propagation-corrected source-related estimation, and angular and operational analysis. The novelty lies in integrating calibrated pass-by acoustics with synchronized vehicle metadata, ambient-noise context, and subsystem-oriented analysis to resolve tonal and modulated features that broadband methods cannot capture. The methodology is demonstrated using an A18D AUV measured in coastal water. Drive-related tonal groups were observed near 5.56, 11.1, and 22.2 kHz, with harmonic structure up to 105 kHz. Source-related tonal PSD estimates ranged from 77 to 120 dB re 1 uPa^2/Hz at 1 m

eess.AS↗

arXiv2025

Sparse Phased Array Optimization Using Deep Learning

Antenna arrays are widely used in wireless communication, radar systems, radio astronomy, and military defense to enhance signal strength, directivity, and interference suppression. We introduce a deep learning-based optimization approach that enhances the design of sparse phased arrays by reducing grating lobes. This approach begins by generating sparse array configurations to address the non-convex challenges and extensive degrees of freedom inherent in array design. We use neural networks to approximate the non-convex cost function that estimates the energy ratio between the main and side lobes. This differentiable approximation facilitates cost function minimization through gradient descent, optimizing the antenna elements' coordinates and leading to an improved layout. Additionally, we incorporate a tailored penalty mechanism that includes various physical and design constraints into the optimization process, enhancing its robustness and practical applicability. We demonstrate the effectiveness of our method by applying it to the ten array configurations with the lowest initial costs, achieving further cost reductions ranging from 411% to 643%, with an impressive average improvement of 552%. By significantly reducing side lobe levels in antenna arrays, this breakthrough paves the way for ultra-precise beamforming, enhanced interference mitigation, and next-generation wireless and radar systems with unprecedented efficiency and clarity.

cs.LG↗

arXiv2025

Near-Field SAR Imaging of Moving Targets on Roads

This paper introduces a single-channel SAR algorithm designed to detect and produce high-fidelity images of moving targets in spotlight mode. The proposed fast backprojection algorithm utilizes multi-level interpolations and aggregation of coarse images produced from partial datasets. Specifically designed for near-field scenarios and assuming a circular radar trajectory, the algorithm demonstrates enhanced efficiency in detecting both moving and stationary vehicles on roads.

eess.SP↗

arXiv2024

Phase-Only Beam Shaping for Transmitting Array Antennas in Radar Applications

Two beam broadening methods for active electronically scanned array (AESA) antennas with uniform amplitude excitation are proposed and compared: phase tapering optimization (PTO) and a novel time-varying phase tapering (TPT). The PTO is a simple and efficient approach assuming continuous polynomial phase distribution and requiring optimization of only few parameters. The TPT is valid mainly for radar applications, taking advantage of the fact that radars typically transmit pulse trains for coherent integration. By varying the array elements' phases from pulse to pulse, the TPT achieves effective amplitude tapering, thus providing a method of beam shaping, occasionally with a simple analytic form. The TPT also makes it possible to produce beam shaping with very low side lobe levels in comparison to the PTO. As a preliminary step, the dimensionality of the radiation pattern characterization for all scan directions is reduced from five to only two variables. This is crucial for efficient optimization of the radiation pattern which needs to be evaluated over a judiciously specified two-dimensional domain.

eess.SP↗

arXiv2023

Fast calculation of retarded potentials in multi-domain TDDFT

A formulation for the efficient calculation of the electromagnetic retarded potential generated by time-dependent electron density in the context of real-time time dependent density functional theory (RT-TDDFT) is presented. The electron density is considered to be spatially separable, which is suitable for systems that include several molecules or nano-particles. The formulation is based on splitting the domain of interest into sub-domains and calculating the time dependent retarded potentials from each sub-domain separately. The computations are accelerated by using the fast Fourier transform and parallelization. We demonstrate this formulation by solving the orbitals dynamics in systems of two molecules at varied distances. We first show that for small distances we get exactly the results that are expected from non-retarded potentials, we then show that for large distances between sub-domains we observe substantial retardation effects.

physics.chem-ph↗

arXiv2022

Super-operator Linear Equations and their Applications to Quantum Antennas and Quantum Light Scattering

In this paper we developed the resolvent method for super-operator equations with their applications in quantum optics. Our approach is based on the novel concept of linear super-operator acting on the Hilbert subspace of vector or scalar linear operators satisfying physically reasonable commutation relations. The super-operator equations for the electromagnetic (EM) field operators are formulated for the problems of quantum antenna emission and quantum light scat-tering by a dielectric body. The general solution of super-operator equation is presented in terms of the classical resolvent. In contrast to the classical case, it includes the ancillary components associated with the quantum noise even in the absence of absorption. The reason for it lies in the energy exchange between different spatial regions with various bases for the field presentation (it looks like losses or gain from the point of view of the correspondent region). A number of examples (two-element dipole antenna, plane dielectric layer, and dielectric cylinder with circular cross section) which demonstrate the physical mechanism of the appearance of noise are considered. It is shown, that antenna emission or scattering transforms the coherent properties of quantum light. This opens a new way of controlling the coherence in a direction dependent manner, a feature that can be useful in various applications of quantum technologies, including, quantum radars and lidars, and quantum antennas.

quant-ph↗

arXiv2022

Quantum Radars and Lidars: Concepts, realizations, and perspectives

In this article, we review the basic concepts of quantum radars as such types of the devices while highlighting differences with their classical analogs. We discuss how several concepts from traditional radars technology, e.g., target detection sensitivity, noise resilience and ranging accuracy can be translated to quantum radars. We examine such new far-field sensing protocols as quantum illumination (QI), and engineering opportunities enabled by its different realizations. We consider possibilities of achieving super-sensitivity and super-resolution using quantum correlations, and discuss possibilities to create quantum correlated states in practice.

quant-ph↗

arXiv2021

Modeling of Multimodal Scattering by Conducting Bodies in Quantum Optics: the Method of Characteristic Modes

We propose a numerical technique for modeling the quantum multimode light scattering by a perfectly conducting body. Using the novel quantization technique, we give the quantum adaptation of the characteristic mode approach widely used in the classical electrodynamics. The method is universal with respect to the body's configuration, as well as its dimensions relative to the wavelength. Using this method and calculating the first- and the second-order field correlation functions, we demonstrate how scattering affects quantum-statistical features of the field. As an example, we consider scattering of the two single-photon incident Gaussian beams on the cylinder with circular cross-section. We show that the scattering is accompanied by the two-photon interference and demonstrates the Hong-Ou-Mandel effect. It is shown, that the scattered two-photon field and its correlations are able to manifest a varying directive propagation, which is controllable by various means (angles of incidence, configuration of the body, relations between its sizes with the frequency). We expect that this method will be useful for designing quantum-optical devices.

quant-ph↗

arXiv2019

A Lorenz gauge formulation for TDDFT

We describe the inclusion of electrodynamic fields in Time-Dependent Density Functional Theory (TDDFT) by incorporating both the induced scalar and vector potentials within the time-dependent Kohn-Sham equation. The Hamiltonian is described in both the Coulomb and Lorenz gauges, and the advantages of the latter are outlined. Integral expressions are defined for the retarded potentials of each gauge and a methodological approach to evaluate these nontrivial expressions with low computational cost is adopted. Various molecular structures of relatively small sizes are studied, including water, benzene, and conductive carbon chains. Absorption cross sections resulting from both pulse and boost excitations suggest a preserved gauge-invariance of the proposed formal approach to TDDFT in the weak magnetic field limit.

physics.chem-ph↗

arXiv2018

Metalized polymer tubes for high-frequency electromagnetic waveguiding

Low loss electromagnetic energy transport over long distances motivates the development of different types of waveguiding systems. Requirements of high quality optically polished waveguide surfaces needed in high-frequency applications and low-cost manufacturing are practically incompatible in current realizations. Here we demonstrate a new paradigm solution, based on surface functionalization with subsequent electroless plating of conductive micron smooth copper layer on the inner surface of flexible non-conducting poly-carbonate tubes. The structure was shown to support moderately low loss guiding performances (~5-10 dB/m) at Ku-band. The mechanically flexible design of the system allows shaping the waveguide network almost on demand. In particular, an efficient energy guiding over a closed loop with 8 lambda radius was demonstrated. The new platform of high quality metalized flexible waveguiding systems opens new opportunities in designs of cheap and efficient networks, operating over a broad spectral range, approaching tens of GHz and even higher.

physics.app-ph↗

arXiv2018

Volumetric 3D-printed antennas, manufactured via selective polymer metallization

Additive manufacturing paves new ways to an efficient exploration of the third space dimension, providing advantages over conventional planar architectures. In particular, volumetric electromagnetic antennas can demonstrate superior characteristics, outperforming their planar counterparts. Here a new approach to the fabrication of electromagnetic devices is developed and applied to antennas, implemented on curved surfaces. Highly directive and broadband antennas were 3D-printed on hemispherical supports. The antenna skeleton and the support were simultaneously printed with different polymer materials - PLA mixed with graphene flakes and pure PLA, respectfully. Weakly DC-conductive graphene PLA-based skeleton was post-processed and high-quality conductive copper layer was selectively electrochemically deposited on it. The antenna devices were found to demonstrate radiation performance, similar to that achievable with conventional fabrication approaches. However, additive manufacturing of RF antennas provides superior capabilities of constructing tailor-made devices with properties, pre-defined by non-standardized end users.

physics.app-ph↗

arXiv2018

Super Scatterers Based on Artificial Localized Magnon Resonances

The interaction between electromagnetic waves and objects is strongly affected by the shape and material composition of the latter. Artificially created materials, formed by a subwavelength structuring of their unit cells, namely metamaterials, can exhibit peculiar responses to electromagnetic radiation and provide additional powerful degrees of freedom to the scatterer design. In particular, negative material susceptibilities give rise to strong resonant interactions with deeply subwavelength particles. While the negative electrical permittivity of natural noble metals manifests itself in localized plasmon resonant oscillations, negative magnetic permeability is virtually non-existent in nature. Here the concept of artificial magnon resonance in subwavelength objects with effective negative permeability, designed based on the metamaterial approach, is demonstrated. Strong localized oscillations of the magnetic fields within an array of split ring resonators, forming a sphere, hybridize in a collective mode of the structure. As a result, extremely high scattering cross section, exceeding that of a steel sphere with the same radius by four orders of magnitude, was demonstrated. Furthermore, the scattering cross section of subwavelength metamaterial-based sphere was shown to be comparable to the low frequency (MHz) radar signature of a big military aircraft. Super scatterers, based on tunable resonances within artificially created materials, can find use in a broad range of electromagnetic applications, including wireless communications, radars, RFID, internet of things hardware and many others.

physics.class-ph↗

arXiv2018

A Fast Algorithm for the Analysis of Scattering by Elongated Cavities

The electromagnetic scattering from elongated, arbitrarily shaped, open-ended cavities have been studied extensively over the years. In this paper we introduce the fast encapsulating domain decomposition (EDD) scheme for the analysis of radar cross section (RCS) of such open-ended cavities. Problem definition, key principles, analysis, and implementation of the proposed solution scheme are presented in detail. The EDD advantages stem from domain decomposition along the elongated dimension and representing the fields on the cross-sections in the spectral domain, which enables us to separate the fields into in- and out-going waves. This diagonolizes the translation between the cross sections, thus reducing the per segment computational complexity from $O((N^A)^3)$ to $O(N^W(N^A)^2)$, where $N^A$ is the number of aperture unknowns and $N^W$ is the number of wall unknowns per segment, satisfying $N^W<<N^A$, since we construct the segmentation step to be small compared to the cross section. The results of the EDD are demonstrated on an S-shape elongated open-ended cavity.

physics.comp-ph↗

arXiv2017

Designing high-transmission and wide angle all-dielectric flat metasurfaces at telecom wavelengths

Recent advances in holography, wireless sensing and light fidelity technologies have resulted in the need for antennas that can support highly efficient beam directivity for a broad angular range. Transmitarrays have been shown to be promising candidates for the determination of such structures. Here, we present a comprehensive methodology for the design of subwavelength all-dielectric flat metasurfaces with high transmission and deflection range. The metasurfaces are CMOS compatible and can be fabricated using conventional processing of silicon-on-insulator technology. The optimized structures exhibit up to 95% efficiency for a wide-angle deflection range from 20° to 60° in air, at operating wavelengths near 1550 nm. Furthermore, we propose the potential multi-wavelength and muti-mode excitation capabilities of the designed supercell. This is achieved by shifting the resonance of each post of the metasurface to the wavelength of interest opening up opportunities for wavelength multiplexing with a single structure. Our results facilitate the realization of broad angle flat deflectors and holographic devices but also indicate that today's bulky and expensive light fidelity optical routers could be substituted by ultra-small chips that are inexpensive to fabricate and can be commercially implemented.

physics.optics↗

arXiv2017

Size dependent electronic properties of silicon quantum dots - an analysis with hybrid, screened hybrid and local density functional theory

We use an efficient projection scheme for the Fock operator to analyze the size dependence of silicon quantum dots (QDs) electronic properties. We compare the behavior of hybrid, screened hybrid and local density functionals as a function of the dot size up to $\sim$800 silicon atoms and volume of up to $\sim$20nm$^3$. This allows comparing the calculations of hybrid and screened hybrid functionals to experimental results over a wide range of QD sizes. We demonstrate the size dependent behavior of the band gap, density of states, ionization potential and HOMO level shift after ionization. Those results are compared to experiment and to other theoretical approaches, such as tight-binding, empirical pseudopotentials, TDDFT and GW.

physics.chem-ph↗

arXiv2017

Degeneracy breaking of Wood's anomaly for enhanced refractive index sensing

We introduce an ultrasensitive detection technique for refractive index (RI) sensing based on an array of nanometer scale slot-antennas milled in a thin gold layer using a single lithographic step. Our experimental figures of merit (FOMs) of 140-210 in the telecom wavelength range approach the fundamental limit for standard propagating SPR sensors (~250).The underlying mechanism enabling this is the combination of a narrowband resonance of the slot-antennas with degeneracy breaking of Wood anomaly under slightly non-perpendicular illumination. In addition, we explore the sensitivity of the device to the depth of the analyte layer. This concept can be easily tuned to any desired wavelength and RI range by modifying the slot dimensions and the array spacing, thus rendering it highly useful for numerous sensing applications.

physics.optics↗

arXiv2017

Highly efficient and broadband wide-angle Holography Using Patch-Dipole Nano-antenna Reflectarrays

We demonstrate wide-angle, broadband and efficient reflection holography by utilizing coupled dipole-patch nano-antenna cells to impose an arbitrary phase profile on of the reflected light. High fidelity images were projected at angles of 450 and 200 with respect to the impinging light with efficiencies ranging between 40%-50% over an optical bandwidth exceeding 180nm. Excellent agreement with the theoretical predictions was found at a wide spectral range. The demonstration of such reflectarrays opens new avenues towards expanding the limits of large angle holography.

physics.optics↗