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Purpose: This paper aims to discuss the classification of targets based on their radar cross-section (RCS). The wavelength, the dimensions of the targets and the distance from the antenna are in the order of 1 mm, 1 m and 10 m, respectively. Design/methodology/approach: The near-field RCS is considered, and the physical optics approximation is used for its numerical calculation. To model real scenarios, the authors assume that the incident angle is a random variable within a narrow interval, and repeated observations of the RCS are made for its random realizations. Then, the histogram of the RCS is calculated from the samples. The authors use a nearest neighbor rule to classify conducting plates with different shapes based on their RCS histogram. Findings: This setup is considered as a simple model of traffic road sign classification by millimeter-wavelength radar. The performance and limitations of the algorithm are demonstrated through a set of representative numerical examples. Originality/value: The proposed method extends the existing tools by using near-field RCS histograms as target features to achieve a classification algorithm. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is performing a global sensitivity analysis for automotive electromagnetic compatibility (EMC) measurements related to the CISPR 25 setup in order to examine the effect of the setup uncertainties on the resonance phenomenon. Design/methodology/approach: An integral equation formulation is combined with Darwin model and special Green's functions to model the configuration. The method of Sobol' indices is used to gain sensitivity factors enhanced with a polynomial chaos metamodel. Findings: The proposed model resulted in by orders of magnitude lower number of degrees of freedom and runtime compared to popular numerical methods, e.g. finite element method. The result of the sensitivity study is in good agreement with the underlying physical phenomena and improves the understanding of the resonances. Practical implications: The fast model supplemented by the sensitivity factors can be used in EMC design and optimization. Originality/value: The proposed method is original in the sense of combining a polynomial chaos metamodel with a low-cost integral equation model to reduce the computational demand for the sensitivity study. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to introduce a novel method for the measurement of electromagnetic material parameters. Design/methodology/approach: The main idea behind the approach is the fact that for slabs with elongated shapes, the intensity of the backscattered field and the electromagnetic resonance frequency corresponding to the length of the sample are dependent on the conductivity of the sample's material. Findings: It is shown that for a known scattered field and resonance frequency, it is possible to formulate an inverse problem as to the calculation of the conductivity of the sample's material at the considered frequencies. To investigate the applicability of the method, demonstrative experiments are performed during which the micro-Doppler effect is used to increase the measurement accuracy. The idea is extended to the case of anisotropic samples, with slight modifications proposed to the experimental setup in the case of significant anisotropy in the investigated material. Practical implications: The measurement method may prove useful for the investigation of the high-frequency conductive properties of certain materials of interest. Originality/value: To the best of the authors' knowledge, this is the first time the use of the micro-Doppler effect is proposed for the purpose of the measurement of material parameters. [ABSTRACT FROM AUTHOR]

Purpose The electromagnetic modeling of inductively coupled, resonant wireless power transfer (WPT) is dealt with. This paper aims to present a numerically efficient simulation method.Design/methodology/approach Recently, integral equation formulations have been proposed, using piecewise constant basis functions for the series expansion of the current along the coil wire. In the present work, this scheme is improved by introducing global basis functions.Findings The use of global basis functions provides a stronger numerical stability and a better control over the convergence of the simulation; moreover, the associated computational cost is lower than for the previous schemes. These advantages are demonstrated in numerical examples, with special attention to the achievable efficiency of the power transfer.Practical implications The method can be efficiently used, e.g., in the optimal design of resonant WPT systems.Originality/value The presented computation scheme is original in the sense that global series expansion has not been previously applied to the numerical simulation of resonant WPT. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to discuss a numerically efficient simulation method for the study of the high-frequency behaviour of air-cored coils. The self-resonance phenomenon of coils can be studied which is important, e.g., in wireless power transfer (WPT). Design/methodology/approach – A full-wave and a quasi-stationary integral formulation is introduced. The integral equation is solved by using the Method of Moments. The complex impedance of the coil is calculated and studied in a wide frequency band. Findings – The integral equation method is numerically efficient compared to finite element schemes, making possible its use in design optimisation problems. Research limitations/implications – The present model can treat homogeneous media only. Future research will focus on the extension of the approach to heterogeneous media. Practical implications – The method can be used in the design optimisation of WPT systems that apply magnetically coupled resonant coils. Originality/value – The presented computation scheme is original. Integral equation schemes have not been used for coil modelling before, to the best of the author’s knowledge. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is the development of an analytic computational model for electromagnetic (EM) wave scattering from spherical objects. The main application field is the modeling of electrically large objects, where the standard numerical techniques require huge computational resources. An example is full-wave modeling of the human head in the millimeter-wave regime. Hence, an approximate model or analytical approach is used. Design/methodology/approach: The Mie–Debye theorem is used for calculating the EM scattering from a layered dielectric sphere. The evaluation of the analytical expressions involved in the infinite sum has several numerical instabilities, which makes the precise calculation a challenge. The model is validated through an application example with comparing results to numerical calculations (finite element method). The human head model is used with the approximation of a two-layer sphere, where the brain tissues and the cranial bones are represented by homogeneous materials. Findings: A significant improvement is introduced for the stable calculation of the Mie coefficients of a core–shell stratified sphere illuminated by a linearly polarized EM plane wave. Using this technique, a semi-analytical expression is derived for the power loss in the sphere resulting in quick and accurate calculations. Originality/value: Two methods are introduced in this work with the main objective of estimating the final precision of the results. This is an important aspect for potentially unstable calculations, and the existing implementations have not included this feature so far. [ABSTRACT FROM AUTHOR]