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An accurate derivation of spatial green's function for finite dielectric structures using characteristic green's function-perfectly matched layer method
, Article IEEE Transactions on Antennas and Propagation ; Vol. 62, Issue. 6 , 2014 , pp. 3201-3211 ; ISSN: 0018926X ; Shishegar, A. A ; Sharif University of Technology
Abstract
A closed-form spatial Green's function for a truncated dielectric slab is derived by using a combination of the characteristic Green's function (CGF) and perfectly matched layer (PML) method. The original structure is terminated by PML that is backed by perfect electric conductor (PEC) in semi-infinite layer at the top and/or bottom. The eigenmodes of the closed structure by PML construct the continuous spectrum contribution of the original structure efficiently. Derived Green's function is exact for separable finite structure while it is approximate for nonseparable one especially in the corners. Generalized scattering matrix (GSM) of truncating surface which contains possible conversions...
An efficient 2D rough surface scattering analysis using strong harmonics extraction and the Kirchhoff approach
, Article Applied Computational Electromagnetics Society Journal ; Volume 29, Issue 2 , 1 February , 2014 , Pages 163-169 ; ISSN: 10544887 ; Shishegar, A. A ; Sharif University of Technology
Abstract
An efficient method for scattering analysis from slightly rough surfaces is introduced. This method can be used in ray tracing algorithm where the computational efficiency is important due to the complexity and size of problems. In this method, the Kirchhoff approach is used for a periodic extension of the finite surface, which is approximated by strong harmonics of its Fourier series. Typical asphalt surfaces are analyzed by this method in millimeter-wave band and validated with the method of moments. The dominant scattering angles and ray widths of the scattered field can be easily used in ray tracing algorithm. The computation time and accuracy of results show that this method can be used...
Efficient and reliable ray tracing, some challenges and proposed solutions. ا
, Article 8th European Conference on Antennas and Propagation, EuCAP 2014 ; April , 2014 , PP. 1589-1592 ; ISBN: 978-8890701849 ; Shishegar, A. A ; Sharif University of Technology
Abstract
Ray tracing has been widely accepted as a versatile and reliable method for indoor propagation modeling. Several published articles have addressed the computational efficiency and reliability as the most challenging problems of ray tracing and have presented various solutions. Such challenges are discussed in this paper and some possible solutions are presented
Effects of inaccuracy of material permittivities on ray tracing results for site- Specific indoor propagation modeling
, Article Proceedings of the 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, IEEE APWC 2013 ; Sept , 2013 , Pages 1172-1175 ; 9781467356893 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
The complex dielectric constants of building materials are present in the reflection, transmission and diffraction coefficients of the ray tracing formulation. Any deviation of the dielectric constants included in ray tracing simulation from the actual material properties may be a source of inaccuracy of the simulation results. This paper explores the sensitivity of ray tracing results to the inaccuracy of the dielectric constants of building materials. To do this, the real and imaginary parts of the dielectric constants are considered as random variables to account for the present uncertainty. The propagation of uncertainty in the ray tracing simulation is then obtained by means of the...
Effects of geometrical uncertainties on ray tracing results for site-specific indoor propagation modeling
, Article Proceedings of the 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, IEEE APWC 2013 ; 2013 , Pages 836-839 ; 9781467356893 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
The plan of the environment used in a ray tracing simulation is not usually in exact accordance with the actual environment plan. Errors on the order of several centimeters may be present in describing the lateral wall positions. Such errors are comparable to the wavelength in indoor wireless applications and hence, can severely alter the phases of multipath components and lead to inaccurate electromagnetic field at the receiver. In this paper, the impact of this type of geometrical errors on the ray tracing results is investigated. Lateral wall positions are considered as random variables to account for possible geometrical errors. The statistical moments of some channel parameters are...
Efficient ultrawideband propagation modelling by using the cubic B-spline function in ray tracing calculations
, Article IET Microwaves, Antennas and Propagation ; Volume 6, Issue 12 , 2012 , Pages 1347-1358 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
IEEE
2012
Abstract
In site-specific ultrawideband propagation modelling, electromagnetic field calculations need to be performed by ray tracing at numerous frequencies of the band in order to properly include the frequency variations of the propagation mechanisms and antenna patterns. This is computationally intensive especially in calculating the coverage map or finding the statistics of the channel parameters where field calculations need to be carried out at a lot of receiver locations. In this study, the cubic B-spline function is incorporated in ray tracing to increase the computational efficiency of site-specific ultrawideband propagation modelling. This function can accurately reconstruct a signal from...
Modified wavefront decomposition method for fast and accurate ray-tracing simulation
, Article IET Microwaves, Antennas and Propagation ; Volume 6, Issue 3 , February , 2012 , Pages 295-304 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
This study presents the modified wavefront decomposition method as a new ray-tracing acceleration technique for indoor propagation modelling. In this method, the exact propagation paths of the rays that reach the receiver after multiple reflections and/or refractions are calculated. Thus, the electromagnetic field at the receiver is obtained with a high accuracy. When only reflections are considered, our method simplifies to the multiple image theory or shooting and bouncing ray/image approach already available in the literature. However, the modified wavefront decomposition method calculates the exact propagation paths toward the receiver even if the rays encounter multiple refractions or a...
Using cubic B-spline interpolation for efficient ray-tracing-based ultrawideband propagation modeling
, Article Proceedings - IEEE International Conference on Ultra-Wideband, 14 September 2011 through 16 September 2011, Bologna ; 2011 , Pages 12-15 ; 21626588 (ISSN) ; 9781457717642 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
Site-specific ultrawideband propagation modeling involves dealing with frequency variations of the propagation mechanisms and antenna patterns in the ray tracing program. Typically, electromagnetic field calculations have to be performed in a lot of frequencies to accurately construct the frequency response of the channel at a receiving point. This imposes a heavy computational burden on ray tracing specially in calculating the coverage map or finding the statistics of channel parameters where the number of receiving locations is large. In this paper, the computational complexity of ray tracing in ultrawideband propagation modeling is reduced by using cubic B-spline interpolation. The...
Physical optics integrals evaluation using closed-form expressions and triangular boundary-rectangular mesh algorithm
, Article IET Microwaves, Antennas and Propagation ; Volume 9, Issue 15 , 2015 , Pages 1803-1808 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
In this study, the authors propose a novel Filon-type integration method that uses error-controllable and frequency-independent closed-form expression to evaluate highly oscillatory physical optics (PO) surface integrals on smooth conducting surfaces. In this method, the phase and amplitude functions of PO integrals for a general parametric surface and incident wave are approximated by second order polynomials, first. Although there are some complicated closed-form expressions for these integrals in the literature, the authors present simple and computationally efficient closed-form expressions for them. For this end, the parametric domain of each resulted integral is meshed by triangular...
Scattering analysis of human body modeled by NURBS surfaces in MM-wave band
, Article Conference on Millimeter-Wave and Terahertz Technologies, MMWaTT, 30 December 2014 through 1 January 2015 ; Volume 2015-March , December-January , 2015 ; 21570965 (ISSN) ; 9781479965915 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper, we propose a frequency-independent method for calculation of scattered electromagnetic (EM) fields by the human body in millimeter-wave (MMW) band. The surface of the body is accurately modeled by non-uniform rational B-spline (NURBS) surfaces and is illuminated by a plane wave. The scattered EM fields are formulated by physical optics (PO) approximation. This approximation yields PO surface highly oscillatory integrals that are solved by numerical steepest descent path (NSDP) method, frequency-independently. This paper provides an efficient and accurate method for considering human body in indoor propagation, surveillance and medical imaging, and detection of human body by...
Indoor ultrawideband propagation modelling using Chebyshev interpolation in 60 GHz band based on ray tracing technique
, Article Conference on Millimeter-Wave and Terahertz Technologies, MMWaTT, 30 December 2014 through 1 January 2015 ; Volume 2015-March , December-January , 2015 ; 21570965 (ISSN) ; 9781479965915 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
An efficient ray tracing technique for channel modeling of an ultrawideband signal in 60 GHz band is introduced. In the usual method, field calculations at many frequencies must be done where has a high computational cost. We have introduced a novel method using Chebyshev polynomials interpolation to reduce the computational cost. Some propagation parameters such as gain and root mean square (RMS) delay spread are obtained and compared to the other method
Electromagnetic wave scattering analysis from 2-D periodic rough surfaces using complex images technique
, Article IEEE Transactions on Geoscience and Remote Sensing ; Volume 53, Issue 2 , July , 2015 , Pages 862-868 ; 01962892 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
The integral equation technique, in combination with the method of moments, is widely used for treating the electromagnetic scattering from periodic rough surfaces. This method, however, requires the computation of a kernel (a periodic Green's function) that consists of a slowly converging infinite series of conventional Green's functions. To accelerate the convergence of this series, different methods have been proposed in literature. In this paper, we use a complex image (CI) technique to find a closed-form expression for the periodic Green's function, which is then used to analyze the electromagnetic scattering from arbitrary periodic rough surfaces. The resulting CI Green's function...
Vectorial Gaussian beam expansion for high-frequency wave propagation
, Article IET Microwaves, Antennas and Propagation ; Volume 4, Issue 12 , 2010 , Pages 2014-2023 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
Wide-waisted Gaussian beam (GB) expansion and point matching methods are discussed in this study as promising techniques for the expansion of electromagnetic waves into GBs. These methods combined with the GB tracing method provide an appropriate scheme for wave propagation analysis in large-scale problems. Details of the wide-waisted GB expansion and point matching methods are provided, and their accuracy and validity regions are discussed. A combination of the aforementioned expansion and tracing methods is utilised to analyse a simple outdoor high-frequency wave propagation problem. The results are compared to the results of the well-known ray tracing method, showing good agreement
Inaccurate path correction in ray tracing using ray expansion method
, Article IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 26 September 2010 through 30 September 2010, Istanbul ; 2010 , Pages 324-328 ; 9781424480166 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
2010
Abstract
This paper presents an efficient way for overcoming the inaccurate path error encountered in ray tracing for site-specific indoor propagation modeling. The source is modeled using triangular ray tubes each of which consists of three rays which do not lie in the same plane. Each possible source ray inside an arbitrary ray tube is expanded in terms of the three rays defining that ray tube. The variations of the expansion coefficients during the intersections of the ray tubes with dielectric media are derived and used for correcting the paths of the rays toward the receiver. A verification example is presented which proves that the presented method has the ability to be efficiently used in...
Rigorous 3D vectorial Gaussian beam modeling of demultiplexing performance of virtually-imaged-phased-arrays
, Article Progress In Electromagnetics Research M ; Volume 13 , 2010 , Pages 1-16 ; 19378726 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
2010
Abstract
We extend our previously-derived generalized closed-form representation for spectral dispersing performance of the Virtually- Imaged-Phased-Array (VIPA) based on a 3D vectorial Gaussian beam formulation to demultiplexing application. To analyze VIPA in the demultiplexer scheme, a spherical lens is added after the VIPA, so that the device plane is superimposed on the focal plane of the lens. The calculated output pro-le at previous step is reformulated ¿ in a matrix form in this step. Finally, the derived closed-form is simulated, and the numerical outcomes are compared with the previous results. The 3D output radiation of VIPA demultiplexer pattern is also depicted and found to be very...
Periodic rough surface scattering analysis using spectral FDTD method
, Article 2010 IEEE International Symposium on Antennas and Propagation and CNC-USNC/URSI Radio Science Meeting - Leading the Wave, AP-S/URSI 2010, 11 July 2010 through 17 July 2010 ; July , 2010 ; 9781424449682 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
2010
Abstract
SFDTD was first introduced as modified Finite Difference Time Domain method by Aminian et al in [1]. They used this method to calculate the TE reflection coefficient for grounded slab and also for periodic array of metallic patches. Later Aminian et al used SFDTD for bandwidth determination of soft and hard ground planes [2] and for determination of permittivity of metamaterials [3]. Yunfei Mao et al also used SFDTD for Solving Oblique incident wave on other kind of patches array [4]
Electromagnetic scattering from perfectly conducting periodic rough surfaces using complex images technique
, Article 2010 IEEE International Symposium on Antennas and Propagation and CNC-USNC/URSI Radio Science Meeting - Leading the Wave, AP-S/URSI 2010, 11 July 2010 through 17 July 2010 ; July , 2010 ; 9781424449682 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
2010
Abstract
Eelectromagnetic analysis of periodic structures is important in the electromagnetic theory. Among them, the electromagnetic wave scattering analysis from rough surfaces is of importance due to both theoretical and practical points of view. For slow variation periodic surfaces the solution can be obtained under the Rayleigh hypothesis in terms of Floquet modes [1]. Integral equation approaches in combination with the method of Moments are among the most frequently used in the solution of scattering problems related to periodic surface due to their flexibility in modeling different geometries [2-3]. Due to slowly convergence of infinite series periodic Green's function, these methods need...
Efficient shooting and bouncing ray tracing using decomposition of wavefronts
, Article IET Microwaves, Antennas and Propagation ; Volume 4, Issue 10 , 2010 , Pages 1567-1574 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
A new acceleration technique is presented for shooting and bouncing ray tracing in indoor environments. Tracing just a few rays, the algorithm finds the solid angles around the transmitter that transport electromagnetic power to the receiver. The accuracy is then improved by iteratively increasing the tessellation frequency of the source in the power-transporting solid angles. No rays will be sent through non-power-transporting solid angles, which results in significant reduction of the simulation time. An example of applying the method for studying indoor radio wave propagation is presented and the results are compared with a very high-resolution fully three-dimensional (3D) ray tracing...
A novel analysis of microstrip structures using the gaussian Green's function method
, Article IEEE Transactions on Antennas and Propagation ; Volume 58, Issue 1 , 2010 , Pages 88-94 ; 0018926X (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
A novel closed form expression is derived for spatial Green's functions of microstrip structures by expanding the spectral Green's function into a Gaussian series. This innovative method is called the Gaussian Green's function (GGF) method due to the Gaussian form in the closed form Green's function representation. The main advantage of the GGF method lies in its precision as well as rapid convergence. To demonstrate the versatility of this method, the current distribution of a microstrip antenna is achieved via the combination of the method of moments (MoM) and GGF method. It is shown that this method can be computationally very efficient with less than 1% error compared to the numerical...
Closed-form green's function of a 2-D rectangular room
, Article IEEE Transactions on Antennas and Propagation ; Volume 64, Issue 12 , 2016 , Pages 5291-5298 ; 0018926X (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Closed-form enough-accurate Green's function for wave-propagation modeling in a rectangular 2-D room is presented using the characteristic Green's function technique. This Green's function is first developed in an integral form. Then, its spatial-domain closed form is obtained using three fast methods. In the first method, the integral is computed by the stationary phase method. In the second one, the integral is computed analytically by expanding the integrand into a complex exponential series. In the third method, the integrand is approximated by a series of rational functions and the integral is computed using Cauchy's residue theorem. The results of these three methods are studied and...