The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
M.f Levy - One of the best experts on this subject based on the ideXlab platform.
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Parabolic Equation techniques for scattering
Wave Motion, 2000Co-Authors: M.f Levy, A.a ZaporozhetsAbstract:Abstract Parabolic Equation techniques for scattering are outlined for both acoustic and electromagnetic waves. Angular limitations are overcome by rotating the paraxial direction and solving for scattered fields that are accurate in sectors centered about the paraxial direction. These fields are then combined to obtain a scattered field that is accurate in all directions. This approach is efficient for bistatic scattering by objects that can be large compared to the wavelength. Parabolic Equation techniques are applied to electromagnetic scattering by a finitely conducting sphere and a large idealised aircraft shape and to acoustic scattering in the presence of an interface.
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Scattering with Parabolic Equation methods: application to RCS computation
IEE Colloquium on Common Modelling Techniques for Electromagnetic Wave and Acoustic Wave Propagation, 1996Co-Authors: P.-p. Borsboom, M.f LevyAbstract:We apply two-way Parabolic Equation (PE) techniques to compute the RCS of two-dimensional convex objects. Since the RCS calculations based on rigorous methods require considerable computational resources to model complex targets, asymptotic methods are applied (uniform theory of diffraction). These methods are not easily applied to complex scatterers. We present a method based on the wide-angle Parabolic Equation capable of solving scattering problems for large complex scatterers. The advantage of the PE models is that they require far less computing resources than full elliptic models while remaining accurate.
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Modelling of radiowave propagation in urban environment with Parabolic Equation method
Electronics Letters, 1996Co-Authors: A.a Zaporozhets, M.f LevyAbstract:Three-dimensional Parabolic Equation algorithms based on Pade finite difference schemes are used in combination with models for the scattering and diffraction of radiowaves by buildings. The Pade
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Radar cross-section computations using the Parabolic Equation method
Electronics Letters, 1996Co-Authors: M.f Levy, P.-p. BorsboomAbstract:Two-way Parabolic Equation (PE) techniques are used to compute the radar cross-section of two-dimensional objects. A finite-difference implementation of a wide angle PE in combination with non-local boundary conditions allows fast execution times on a desktop computer. The technique is applied to scattering by a cylinder and by an idealised aircraft shape. Numerical results are in good agreement with calculations using other methods.
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Diffraction studies in urban environment with wide-angle Parabolic Equation method
Electronics Letters, 1992Co-Authors: M.f LevyAbstract:The wide-angle Parabolic Equation gives a rigorous solution to the problem of diffraction by several buildings of arbitrary shape. Applications to propagation in urban microcellular environments are presented.
Yunliang Long - One of the best experts on this subject based on the ideXlab platform.
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Research on localization of emitter source in forest environment using inverse diffraction Parabolic Equation based on finite difference method
2015 Asia-Pacific Microwave Conference (APMC), 2015Co-Authors: Qinglong Zeng, Ci Zhou, Yunliang LongAbstract:The localization of non-cooperative emitter sources is a hot and difficult problem in the modern war. The arithmetic of Inverse Diffraction Parabolic Equation has a good applicability and stability characteristic for passive localization in complex environment. In this paper, an inverse diffraction Parabolic Equation model based on finite difference method (FDM) is constructed to research the localization of the emitter source over forested environment. The article introduces a handing method of forest vegetation and analyzes the effects of forest vegetation on accuracy of transmitter positioning. Simulation results proved that the Inverse Algorithm of Finite Difference Parabolic Equation does a good localization estimate of the emitter source.
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Reply to “Comments on 'Propagation modeling over irregular terrain by the improved two-way Parabolic Equation method'”
IEEE Transactions on Antennas and Propagation, 2014Co-Authors: Kun Wang, Yunliang LongAbstract:In this paper, we focused on deriving and refining the two-way Parabolic Equation (2WPE) formulations and developing the improved two-way split-step Parabolic Equation (2W-SSPE) method to model both forward- and backward-propagating waves over various lossy surfaces with impedance boundary conditions (IBC) in urban and tropospheric scenarios.
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Propagation Modeling Over Irregular Terrain by the Improved Two-Way Parabolic Equation Method
IEEE Transactions on Antennas and Propagation, 2012Co-Authors: Kun Wang, Yunliang LongAbstract:The two-way split-step Parabolic Equation (2W-SSPE) method is improved to be able to model both forward- and backward-waves propagation over irregular perfectly electrical conducting (PEC) surfaces and irregular lossy surfaces with impedance boundary conditions (IBC). The discrete mixed Fourier transform (DMFT) is applied in both forward- and backward- direction to deal with IBC, and the boundary shift (BS) method is used to dispose of the irregular terrain effects. Numerical results obtained by the improved 2W-SSPE algorithm for several typical scenarios with different ground types are compared with those got by the previous 2W-SSPE method and the one-way Parabolic Equation method.
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Improved fourier transform Parabolic Equation for wave propagation over rough sea surface
2008 International Conference on Microwave and Millimeter Wave Technology, 2008Co-Authors: Ke Zhang, Yunliang LongAbstract:Electromagnetic wave propagation over sea surface is affected by the surface roughness. In this paper, an improved impedance boundary method is presented and the initial field is calculated by Green function, which improves the stability and accurateness of the Parabolic Equation (PE). Eventually the forecast of propagation over rough sea surface has been presented with Parabolic Equation (PE). The results from PE are compared with Miller-Brown model, good agreement is shown.
Funda Akleman - One of the best experts on this subject based on the ideXlab platform.
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Groundwave propagation in a nonhomogeneous atmosphere: Prediction using 3D Parabolic Equation
2017 International Applied Computational Electromagnetics Society Symposium - Italy (ACES), 2017Co-Authors: Zeina El Ahdab, Funda AklemanAbstract:The analysis of groundwave propagation over long distances in an atmosphere with non-homogeneous electromagnetic properties is conducted by using a three-dimensional Parabolic Equation method (3D-PE) based approach. The inhomogeneities in the atmosphere imply the formation of ducts which result in modifying the propagation direction and range of the waves. The signal is excited by a vertical line source, and the waves are marched in range by using the Fourier split-step algorithm. Multiple tests are conducted in which different types of ducts are considered in order to analyze and validate the results obtained by the 3D algorithm. These results are compared to those obtained from two-dimensional Parabolic Equation based algorithm (2D-PE).
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Radiowave Propagation Analysis With a Bidirectional 3-D Vector Parabolic Equation Method
IEEE Transactions on Antennas and Propagation, 2017Co-Authors: Zeina El Ahdab, Funda AklemanAbstract:A 3-D bidirectional solution to the Parabolic approximation of the wave Equation is investigated by using a vector field representation. The backward propagating wave is integrated to the classical Parabolic Equation approach, which represents the forward propagating wave. Propagation over flat terrain in the presence of knife-edges is considered as well as over irregular terrain consisting of hills modeled by the succession of knife-edges. At each knife-edge, appropriate boundary conditions are enforced, and the wave is partly reflected in the backward direction. The wave is marched in both directions by using the split-step algorithm. Different tests are conducted in order to analyze and validate the results obtained by the proposed algorithm. Comparisons with results from both, 2-D Parabolic Equation-based algorithm, and 3-D finite-difference time domain-based algorithm, are presented in this paper.
A. E. Barrios - One of the best experts on this subject based on the ideXlab platform.
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A Comparison of Rough Surface Parabolic Equation Models
1994Co-Authors: A. E. BarriosAbstract:Abstract : Several Parabolic Equation models currently exist that model radiowave propagation over the ocean. Few of these models can accurately account for rough surface effects over an ocean environment. Several techniques to account for these effects, implemented within the split-step Parabolic Equation (PE) algorithm, are investigated.
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Parabolic Equation modeling in horizontally inhomogeneous environments
IEEE Transactions on Antennas and Propagation, 1992Co-Authors: A. E. BarriosAbstract:A Parabolic Equation model has been developed for use in tropospheric radiowave propagation. A simple technique to model range-dependent environments has been implemented. Results from the model are compared with experimental data at 170, 520, 3240, 3300, and 9875 MHz in measured range-dependent environments. The experimental data are taken from two separate experiments performed during 1947 and 1948. Measurements were made on overwater paths from Guadalupe Island to San Diego, CA, in one experiment, and the other was located in the South Island of New Zealand, also known as the Canterbury Project. The results are presented as one-way propagation factor in decibels versus height. The technique used to model range-dependent environments is shown to give a reasonably good estimate of the environment between measurements, leading to excellent agreement between the predicted fields and observed radio data. >
Qingliang Li - One of the best experts on this subject based on the ideXlab platform.
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Applying perfectly absorbing thin screen to the 3D Parabolic Equation method
2017 Sixth Asia-Pacific Conference on Antennas and Propagation (APCAP), 2017Co-Authors: Xiaowei Guan, Yajiao Wang, Qingliang LiAbstract:In this paper, perfectly absorbing thin screen is applied to the three-dimensional (3D) Parabolic Equation method in order to predict the propagation of electromagnetic waves in urban environments. The impedance boundary condition is used to represent the lossy nature of the ground and the Tukey window is adopted to attenuate the fields smoothly at the upper boundary without reflections. Besides, buildings are equivalent to a series of perfectly absorbing thin screens arranged along the direction of propagation and we use the split-step Fourier transform algorithm to solve the 3D Parabolic Equation. Finally, in order to validate the proposed method, several numerical simulations of a typical building on a flat ground are made and the results are compared with those in the literature. As a result, good agreements are observed.
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A narrow-angle Parabolic Equation model in atmospheric ducts
2016 11th International Symposium on Antennas Propagation and EM Theory (ISAPE), 2016Co-Authors: Yajiao Wang, Qingliang LiAbstract:In this paper, the narrow-angle Parabolic Equation (NAPE) model applied on atmospheric ducts is solved by using the improved discrete mixed Fourier transform (IDMFT) method which is an efficient form of the split-step Fourier transform (SSFT) algorithm under the impedance boundary conditions. In order to verify the accuracy of the narrow-angle Parabolic Equation method, the numerical results are compared with the experimental data in the literature as well as the results of mode theory and the Advanced Refractive Effects Prediction System (AREPS) software. Finally, the effects of the receiving antenna height and the evaporation duct height on the propagation loss in the evaporation duct are analyzed in details.
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A vector Parabolic Equation method for propagation predictions over flat terrains
2016 11th International Symposium on Antennas Propagation and EM Theory (ISAPE), 2016Co-Authors: Xiaowei Guan, Qingliang LiAbstract:Starting from a Parabolic approximation to the Helmholtz Equation, a three-dimensional (3-D) vector Parabolic Equation (PE) method for propagation predictions over flat terrains is presented. The split-step Fourier transform (SSFT) algorithm is adopted to solve the vector Parabolic Equation obtained. Besides, the impedance boundary condition is studied, as well as the absorbing boundary condition. Finally, in order to validate the proposed method, several numerical simulations of a typical flat terrain are made by using the 3-D PE method and some other methods respectively, and as a result, great agreements are observed.
