Uniform Plane Wave Research Articles

Interception force assisted optical pulling of a dipole nanoparticle in a single plane wave

The optical pulling force is generally believed to originate from the recoil force due to the simultaneous excitation of multipoles in the particle, which overcomes the interception force contributing to the optical pushing force. However, we show that the interception force can induce optical pulling force on a small isotropic spherical particle with gain in a uniform electromagnetic plane wave, in which multipole excitation is negligible within the dipole regime. Based on the multipole expansion theory, a rigorous analytical expression is derived for optical force acting on a spherical particle of arbitrary size and composition illuminated by a single plane wave, regardless of its polarization. The analytical results show that the interception force, which is typically positive in a conventional dielectric particle under illumination of a single plane wave, undergoes a crossover from positive to negative by introducing appropriate gain into the dipolar dielectric nanoparticle, thereby giving rise to the optical pulling. It’s deserved to be noted that the optical pulling force assisted by the interception force does not weaken in magnitude, in fact, it exhibits a stronger magnitude compared to the optical pushing force experienced by a corresponding conventional dielectric particle.

Sub‐6 GHz plane wave generator design for automotive antenna over‐the‐air testing

AbstractAutomotive antennas are gaining importance due to their increasingly important role for autonomous driving with the development of the Internet of Vehicles. However, over‐the‐air testing on automotive antennas is difficult owing to its large volume and complex body structure. Plane wave generators can approximate uniform plane waves in the near field of the device under test, which can greatly reduce the measurement distance and thereby decreasing the cost compared with direct far‐field solutions. This letter designs three plane wave generators for three quiet zone sizes selected according to the vehicle structure at 5.9 GHz, achieving quiet zone sizes of 1.45 m m, 2.9m m, and 3.9 m m, respectively. Within the three quiet zones, amplitude deviations of 0.82, 0.34, and 0.34 dB and phase deviations of , and are realized, respectively, according to the numerical simulations. Uncertainty analysis is further implemented to investigate the robustness of the designed PWGs proposed in this letter.

Modular extremely large-scale array communication: Near-field modelling and performance analysis

This paper investigates the wireless communication with a novel architecture of antenna arrays, termed modular extremely large-scale array (XL-array), where array elements of an extremely large number/size are regularly mounted on a shared platform with both horizontally and vertically interlaced modules. Each module consists of a moderate/flexible number of array elements with the inter-element distance typically in the order of the signal wavelength, while different modules are separated by the relatively large inter-module distance for convenience of practical deployment. By accurately modelling the signal amplitudes and phases, as well as projected apertures across all modular elements, we analyse the near-field signal-to-noise ratio (SNR) performance for modular XL-array communications. Based on the non-uniform spherical wave (NUSW) modelling, the closed-form SNR expression is derived in terms of key system parameters, such as the overall modular array size, distances of adjacent modules along all dimensions, and the user's three-dimensional (3D) location. In addition, with the number of modules in different dimensions increasing infinitely, the asymptotic SNR scaling laws are revealed. Furthermore, we show that our proposed near-field modelling and performance analysis include the results for existing array architectures/modelling as special cases, e.g., the collocated XL-array architecture, the uniform plane wave (UPW) based far-field modelling, and the modular extremely large-scale uniform linear array (XL-ULA) of one-dimension. Extensive simulation results are presented to validate our findings.

Dual-Polarized Near-Field Plane Wave Generator Using an Offset-Optics Reflectarray Mm-Wave Band

In this work, a reflectarray antenna is presented as a dual-polarized plane wave generator (PWG) in mm-wave frequencies. The reflectarray produces a uniform plane wave within its near field in a volume close to the aperture. A dual-polarized pencil beam reflectarray is used as starting point to carry out a phase-only synthesis (POS) to reach a dual-polarized uniform plane wave. The synthesis aims to overcome the amplitude limitation due to the incident field while preserving the phase flatness. The phase distribution obtained in the POS is used to carry out a design based on sets of orthogonal-coplanar dipoles. This unit cell provides independent control of each polarization using a single-layer topology. The design is manufactured, and the prototype is measured in a planar acquisition range facility. The prototype shows discrepancies with simulation and further analysis is carried out. After finding out the proper value of the dielectric constant, a new design is carried out. The second prototype shows a good agreement with simulations, obtaining that reflectarray antennas are a suitable and low-profile solution to produce uniform plane waves within the near field.

Steerable photonic jet for super-resolution microscopy

A promising technique in optical super-resolution microscopy is the illumination of the sample by a highly localized beam, a photonic jet (also called photonic nanojet). We propose a method of computation of incident field amplitude and phase profiles that produce photonic jets at desired locations in the near field after interaction with a fixed micro-scale dielectric lens. We also describe a practical way of obtaining the incident field profiles using spatial light modulators. We expect our photonic jet design method to work for a wide range of lens shapes, and we demonstrate its application numerically using two-dimensional micro-lenses of circular and square cross-sections. We furthermore offer a theoretical analysis of the resolution of photonic jet design, predicting among other that a larger lens can produce a narrower photonic jet. Finally, we give both theoretical and numerical evidence that the waist width of the achieved designed jets is increasing linearly and slowly over a large interval of radial distances. With uniform plane wave illumination, the circular two-dimensional micro-lens produces a similar-sized jet at a fixed radial distance, while the square lens does not form a jet at all. We expect our steerable optical photonic jet probe to enable highly localized adaptive real-time measurements and drive advances in super-resolution optical microscopy and scatterometry, as well as fluorescence and Raman microscopy. Our relatively weak peak jet intensity allows application in biology and health sciences, which require high resolution imaging without damaging the sample bio-molecules.

Applied Electromagnetics Course with a Conceiving-Designing-Implementing-Operating Approach in Engineering Education

This paper describes and discusses the implementation of a project-based undergraduate course on applied electromagnetics in electronics engineering with a conceiving-designing-implementing-operating (CDIO) approach involving active project-based learning (PBL). The course, which requires a combination of mathematical and physics concepts for its completion, allows students to understand the principles of electromagnetic transmission theory in wireless communication systems. This paper presents the course proposal, its project description, and results hinting at the relationship with the CDIO process. The proposed projects allow students to engage in core concepts such as complex vectors, Maxwell’s equations, boundary conditions, Poynting's theorem, uniform plane waves, reflection and transmission of waves, waveguides, cavity resonators, and computer-assisted design. The proposed methodology results suggest that students lowered their perception of the difficulty of the course, and most students recognized a better learning process of the core concepts for this course. In addition, students’ final course grades showed an average improvement of approximately 6% compared with the final grades of other groups with different methodologies.

Near-Field Spatial Correlation for Extremely Large-Scale Array Communications

Extremely large-scale array (XL-array) communications correspond to systems whose antenna sizes are so large that the scatterers and/or users may no longer be located in the far-field region. By discarding the conventional far-field uniform plane wave (UPW) assumption, this letter studies the near-field spatial correlation of XL-array communications, by taking into account the more generic non-uniform spherical wave (NUSW) characteristics. It is revealed that different from the far-field channel spatial correlation which only depends on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">power angular spectrum</i> (PAS), the near-field spatial correlation depends on the scattered power distribution not just characterized by their arriving angles, but also by the scatterers’ distances, which is termed as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">power location spectrum</i> (PLS). A novel integral expression is derived for the near-field spatial correlation in terms of the scatterers’ location distribution, which includes the far-field spatial correlation as a special case. The result shows that different from the far-field case, the near-field spatial correlation no longer exhibits <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">spatial stationarity</i> in general, since the correlation coefficient for each pair of antennas depends on their specific positions, rather than their relative distance only. To gain further insights, we consider a generalized one-ring model for scatterer distribution, where the ring center may be flexibly located. Numerical results are provided to show the necessity of the near-field spatial correlation modelling for XL-array communications.

Near-Field Modeling and Performance Analysis of Modular Extremely Large-Scale Array Communications

This letter studies a new array architecture, termed as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">modular extremely large-scale</i> array (XL-array), for which a large number of array elements are arranged in a modular manner. Each module consists of a moderate number of array elements and the modules are regularly arranged with the inter-module spacing typically much larger than signal wavelength to cater to the actual mounting structure. We study the mathematical modelling and conduct the performance analysis for modular XL-array communications, by considering the non-uniform spherical wave (NUSW) characteristic that is more suitable than the conventional uniform plane wave (UPW) assumption for physically large arrays. A closed-form expression is derived for the maximum signal-to-noise ratio (SNR) in terms of the geometries of the modular XL-array, including the total array size and module separation, as well as the user’s location. The asymptotic SNR scaling law is revealed as the size of modular array goes to infinity. Furthermore, we show that the developed modelling and performance analysis include the existing results for collocated XL-array or far-field UPW assumption as special cases. Numerical results demonstrate the importance of near-field modelling for modular XL-array communications since it leads to significantly different results from the conventional far-field UPW modelling.

Communicating With Extremely Large-Scale Array/Surface: Unified Modeling and Performance Analysis

Wireless communications with extremely large-scale array (XL-array) correspond to systems whose antenna sizes are so large that conventional modeling assumptions, such as uniform plane wave (UPW) impingement, are no longer valid. This paper studies the mathematical modeling and performance analysis of XL-array communications. By deviating from the conventional modeling approach that treats the array elements as sizeless points, we explicitly model their physical area/aperture, which enables a unified modeling for the classical discrete antenna arrays and the emerging active continuous surfaces. As such, a generic array/surface model that accurately takes into account the variations of signal phase, amplitude and projected aperture across array elements is proposed. Based on the proposed model, a closed-form expression of the resulting signal-to-noise ratio (SNR) with the optimal single-user maximum ratio combining/transmission (MRC/MRT) beamforming is derived. The expression reveals that instead of scaling linearly with the antenna number <inline-formula> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> as in conventional UPW modeling, the SNR with the more generic model increases with <inline-formula> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> with diminishing return, which is governed by the collective properties of the array, such as the <i>array occupation ratio</i> and the physical sizes of the array along each dimension, while irrespective of the properties of the individual array element. In addition, we have derived an alternative insightful expression for the optimal SNR in terms of the <i>vertical</i> and <i>horizontal angular spans</i>, which are fully determined by the geometric angles formed by the array/surface and user location. Furthermore, we also show that our derived results include the far-field UPW modeling as a special case. One important finding during the study of far-field approximation is the necessity to introduce a new distance criterion to complement the classical Rayleigh distance, termed <i>uniform-power distance</i> (UPD), which concerns the signal amplitude/power variations across array elements, instead of phase variations as for Rayleigh distance. Extensive numerical results are provided to demonstrate the necessity of proper modeling for XL-array communications by comparing the proposed model with various benchmark models.

Exceptional points in lossy media lead to deep polynomial wave penetration with spatially uniform power loss.

Waves entering a spatially uniform lossy medium typically undergo exponential intensity decay, arising from either the energy loss of the Beer-Lambert-Bouguer transmission law or the evanescent penetration during reflection. Recently, exceptional point singularities in non-Hermitian systems have been linked to unconventional wave propagation. Here, we theoretically propose and experimentally demonstrate exponential decay free wave propagation in a purely lossy medium. We observe up to 400-wave deep polynomial wave propagation accompanied by a uniformly distributed energy loss across a nanostructured photonic slab waveguide with exceptional points. We use coupled-mode theory and fully vectorial electromagnetic simulations to predict deep wave penetration manifesting spatially constant radiation losses through the entire structured waveguide region regardless of its length. The uncovered exponential decay free wave phenomenon is universal and holds true across all domains supporting physical waves, finding immediate applications for generating large, uniform and surface-normal free-space plane waves directly from dispersion-engineered photonic chip surfaces.

Near-Field Modeling and Performance Analysis for Multi-User Extremely Large-Scale MIMO Communication

This letter studies the near-field modeling and performance analysis for multi-user extremely large-scale multiple-input multiple-output (XL-MIMO) communication. With the spherical wavefront phase modeling, and by taking into account the variations of signal amplitude and projected aperture across array elements, the performance of the three typical beamforming schemes are investigated, namely the maximal-ratio combining (MRC), zero-forcing (ZF), and minimum mean-square error (MMSE) beamforming. Compared to existing uniform plane wave (UPW) model where inter-user interference (IUI) can only be suppressed in angular domain, XL-MIMO enables a new degree-of-freedom (DoF) for IUI suppression by distance separation, even for users along the same direction. Simulation results are provided to validate the modeling and performance analysis of multi-user XL-MIMO communications.

Adjustable Resolution for Localized FSS-Based Sensing by Synthetic Beamforming

Recently, frequency-selective surface (FSS)-based sensors have shown potential for structural health monitoring due to their sensitivity to changes in element geometry, interelement spacing, substrate properties, and local environment. In addition, these sensors are remotely interrogated and are planar in design, thereby providing a wireless sensing solution that can cover large areas. Traditionally, FSS sensors are analyzed assuming a uniform (plane wave) illumination. However, practically speaking, the sensor will be illuminated with a nonuniform excitation. In this way, the resolution of the sensor is limited to the illumination pattern (footprint) on the sensor. As such, an adjustable illumination pattern is advantageous as it relates to the ability to interrogate the sensor on a localized or comprehensive basis. To this end, this article considers a synthetic beamforming approach to adjust the beamwidth of the focused illumination beam on the sensor as a solution for localized sensing applications. This approach is proposed to generate an arbitrary beam shape with a desired footprint. Moreover, the illumination and spillover efficiencies of the synthetic beam (SB) are defined, simulated, and discussed. The results show that a minimum focal area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\lambda _{0} \times 1\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times3$ </tex-math></inline-formula> unit cells for the FSS sensors considered here) is essential to achieve a spillover efficiency of greater than 80%, thereby reducing the contribution of other neighboring unit cells on the sensor response. In addition, the illumination efficiency when an SB is utilized for illumination is greater than 80% due to the uniformity of the SB. Representative measurements were also performed on a sensor with a simulated strain profile.

Teaching the concept of the uniform plane wave from mathematical modeling

The discovery of electromagnetic waves enabled us to understand electricity, magnetism, and optics under the same field; therefore, it is important for electronic and related engineers to understand the concept of the uniform plane wave, which represents the simplest case of an electromagnetic wave propagating through a medium. However, this concept is taught with a theoretical approach, shows a need for a methodological change towards experimentation to mitigate poor learning in students causing a high failure rate in electromagnetism courses. In this context, this work presents a methodological alternative for teaching the concept of the uniform plane wave, combining the CUVIMA model with the didactics of mathematical modelling, to link experimentation and provide cognitive support to the conceptualization of the physical phenomenon. For it, a single-group design is implemented, with pre-test and post-test, to know about previous ideas and identify the conceptual change achieved for the students. When applying the Student’s t-test at a significance level of 5%, a significant difference is evident between the means of the study groups. It is concluded that there is a favorable and representative conceptual change in the students, with respect to the understanding of the physical phenomenon represented by the concept of the uniform plane wave.

Methods for studying «antenna-radome» system using planar and cylindrical scanners

The paper presents the method for studying an antenna with a radome based on measurements in the near zone. Cases of planar and cylindrical scanning are considered. For both planar and cylindrical scanning, the study of the «antenna-radome» system is supposed to be carried out in two stages: by the amplitude and phase measurements the components of the vector amplitude spectra of uniform plane waves of antenna without radome are determined, and then for antenna with a radome. In contrast to the planar case, in the case of cylindrical scanning the components of vector amplitude spectra of the «antenna-radome» system are determined through the amplitudes of homogeneous vector cylindrical waves. To assess the effect of the radome on the antenna located under it, it is proposed to use the spectral tensor characteristic of the transmission, and ways how determine its elements are proposed. One of the possible ways to reduce the influence of the radome on the characteristics of a phased antenna array by correcting the amplitude-phase distribution of its radiating elements is considered.

Generalized Lorenz-Mie theory in the analysis of longitudinal photophoresis of arbitrary-index particles: On-axis axisymmetric beams of the first kind

The uniform plane wave is the reference solution of Maxwell’s equations when it comes to rigorous theoretical investigations of photophoretic forces from the Mie theory. Here, we address the theory of photophoresis for a more general class of on-axis axisymmetric beams of the first kind. To do so, the generalized Lorenz-Mie theory (GLMT) is introduced for the first time in the calculation of analytic and closed-form expressions for the asymmetry factor assuming arbitrary-index micro-sized spheres of arbitrary size parameters. The behavior of the asymmetry factor is illustrated for non-volatile particles illuminated by Gaussian and circularly symmetric zero-order Bessel beams. The theory here presented is valid for arbitrary size parameters and is a first attempt towards the incorporation of real optical wave fields into photophoresis of absorbing particles using the GLMT for arbitrary-shaped beams.

Asymmetric Diffraction in Plasmonic Meta-Gratings Using an IT-Shaped Nanoslit Array.

Diffraction is a fundamental phenomenon that reveals the wave nature of light. When a plane wave is transmitted or reflected from a grating or other periodic structures, diffracted light waves propagate at several angles that are specified by the period of the given structure. When the optical period is shorter than the wavelength, constructive interference of diffracted light rays from the subwavelength-scale grating forms a uniform plane wave. Many studies have shown that through the appropriate design of meta-atom geometry, metasurfaces can be used to control light properties. However, most semitransparent metasurfaces are designed to perform symmetric operation with regard to diffraction, meaning that light diffraction occurs identically for front- and back-side illumination. We propose a simple single-layer plasmonic metasurface that achieves asymmetric diffraction by optimizing the transmission phase from two types of nanoslits with I- and T-shaped structures. As the proposed structure is designed to have a different effective period for each observation side, it is either diffractive or nondiffractive depending on the direction of observation. The designed structure exhibits a diffraction angle of 54°, which can be further tuned by applying different period conditions. We expect the proposed asymmetric diffraction meta-grating to have great potential for the miniaturized optical diffraction control systems in the infrared band and compact optical diffraction filters for integrated optics.

Natural Mode Series Expansion of Transient Transmission Field Through an N-Layer Structure

Time-domain (early- and late-time) transmission response of an $N$ -layer composite structure has been analytically investigated using contour integration for uniform plane waves with perpendicular and parallel polarizations. It has been shown that whereas the late-time transmission response of an $N$ -layer structure is a sum of damped sinusoids provided that it is terminated in a lossless medium (e.g., air medium), its early-time response can be represented as the summation of individual subregional responses, which can be expressed by natural series if any subregion is surrounded by lossless media (assuming that the last layer is lossless). Numerical examples are presented to investigate the early- and late-time transmission responses, and thus validate the results obtained from contour integration, of transparent $N$ -layer composite structures for perpendicular and parallel polarization cases.

Communication and Localization With Extremely Large Lens Antenna Array

Achieving high-rate communication with accurate localization and wireless environment sensing has emerged as an important trend of beyond-fifth and sixth generation cellular systems. Extension of the antenna array to an extremely large scale is a potential technology for achieving such goals. However, the super massive operating antennas significantly increases the computational complexity of the system. Motivated by the inherent advantages of lens antenna arrays in reducing system complexity, we consider communication and localization problems with an ex tremely large lens antenna array, which we call “ExLens”. Since radiative near-field property emerges in the setting, we derive the closed-form array response of the lens antenna array with spherical wave, which includes the array response obtained on the basis of uniform plane wave as a special case. Our derivation result reveals a window effect for energy focusing property of ExLens, which indicates that ExLens has great potential in position sensing and multi-user communication. We also propose an effective method for location and channel parameters estimation, which is able to achieve the localization performance close to the Cramer-Rao lower bound. Finally, we examine the multi-user communication performance of ExLens that serves coexisting near-field and far-field users. Numerical results demonstrate the effectiveness of the proposed channel estimation method and show that ExLens with a minimum mean square error receiver achieves significant spectral efficiency gains and complexity-and-cost reductions compared with a uniform linear array.

Time-domain analysis and experimental investigation of electromagnetic wave coupling to RF/microwave nonlinear circuits

ABSTRACT This paper presents an efficient time-domain analysis of RF/microwave nonlinear circuits in the presence of the incident uniform plane wave. In this paper, a set of differential equations, including the linear equations due to incident field coupling and nonlinear state equations for the active part of the circuit, are derived and simultaneously solved using the finite difference time domain (FDTD) method. Moreover, a numerical approach with global convergence is used to guarantee the stability of the proposed algorithm. Furthermore, for validation of the proposed method, the theoretical and experimental studies using a measurement setup, including a transverse electromagnetic (TEM) cell, are carried out for performance analysis of a low noise amplifier illuminated by the high-power incident plane wave. By comparison with measurement results, satisfactory accuracy is obtained, which indicates the ability of the proposed method in dealing with the radiated susceptibility of RF/microwave circuits, involving the electromagnetic interference (EMI) problem.

Design of XOR/NOT gate and power-phase comparator by gold air-gap composition in silicon wiring technology

The large differences between the refractive index of Si and SiO2 in the SOI composite (silicon on insulator) and, as a result, its high ability to trap lasers, have led to the construction of valuable optical equipment in recent years. In this paper, with a new idea, by adding two reciprocating golden walls and a transverse air gap, the SOI structure is developed in such a way that equipment made with the new method, such as XOR and NOT gates and power-phase comparators, have a dreamy speed and a super small size. This structure is only compatible with linear polarization so that the axis of polarization, which is the direction of the electric field, is parallel to the gold plates. In the multifunctional structure presented in this paper, if the inputs are uniform plane waves, the output will be uniform plane wave with high accuracy and that the inputs can be phase or power while the output is only power. Simulation in this paper is done using finite-difference-time-domain method.