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Journal ArticleDOI

Near-field to near/far-field transformation for arbitrary near-field geometry utilizing an equivalent electric current and MoM

01 Mar 1999-IEEE Transactions on Antennas and Propagation (IEEE)-Vol. 47, Iss: 3, pp 566-573
TL;DR: In this article, a method for computing near and far-field patterns of an antenna from its near-field measurements taken over an arbitrarily shaped geometry is presented, where the measured data need not satisfy the Nyquist sampling criteria and an electric field integral equation is developed to relate the near field to the equivalent electric current.
Abstract: Presented here is a method for computing near- and far-field patterns of an antenna from its near-field measurements taken over an arbitrarily shaped geometry. This method utilizes near-field data to determine an equivalent electric current source over a fictitious surface which encompasses the antenna. This electric current, once determined, can be used to ascertain the near and the far field. This method demonstrates the concept of analytic continuity, i.e., once the value of the electric field is known for one region in space, from a theoretical perspective, its value for any other region can be extrapolated. It is shown that the equivalent electric current produces the correct fields in the regions in front of the antenna regardless of the geometry over which the near-field measurements are made. In this approach, the measured data need not satisfy the Nyquist sampling criteria. An electric field integral equation is developed to relate the near field to the equivalent electric current. A moment method procedure is employed to solve the integral equation by transforming it into a matrix equation. A least-squares solution via singular value decomposition is used to solve the matrix equation. Computations with both synthetic and experimental data, where the near field of several antenna configurations are measured over various geometrical surfaces, illustrate the accuracy of this method.
Citations
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Journal ArticleDOI
TL;DR: In this article, a technique for the determination of the equivalent currents distribution from a known radiated field is described, based on the representation of the radiating structure by means of a set of equivalent currents over a 3D surface that can be fitted to the arbitrary geometry of the antenna.
Abstract: A technique for the determination of the equivalent currents distribution from a known radiated field is described. This Inverse Radiation Problem is solved through an Integral Equation algorithm that allows the characterization of antennas of complex geometry both for near field to far field (NF-FF) transformation purposes as well as for diagnostic tasks. The algorithm is based on the representation of the radiating structure by means of a set of equivalent currents over a three-dimensional (3D) surface that can be fitted to the arbitrary geometry of the antenna. The innovative formulation uses an integral equation involving the electric field due to the currents tangential components to the represented antenna 3D surface. For that purpose, both the magnetic and electric equivalent currents are considered in the integral equations. Regularization techniques are also introduced to improve the convergence of the proposed iterative solution. The paper concludes with several results related to the practical verification of the Equivalence Principle and the characterization of a horn antenna.

222 citations


Cites background from "Near-field to near/far-field transf..."

  • ...domain [7], a circular domain [4], [15], a spherical domain [8], [12], [16], [17] or an arbitrary domain [6], [13], [14]....

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Journal ArticleDOI
TL;DR: In this paper, a simple method to obtain the equivalent radiation emitting sources of an electronic circuit using the near-field scanning method is presented, which is based on a set of elemental dipoles that substitutes the electronic circuit and radiates the same magnetic field.
Abstract: In this paper, a simple method to obtain the equivalent radiation emitting sources of an electronic circuit using the near-field scanning method is presented. The model is based on a set of elemental dipoles that substitutes the electronic circuit and radiates the same magnetic field. Two different approaches are presented: a set of electric dipoles and a set of magnetic dipoles. In order to build the model, both the magnitude and phase of the magnetic field are required. These measurements are carried out using the "near-field scanning method," and two procedures are presented: using the vector network analyzer and the spectrum analyzer. Finally, the model is applied to two different cases: to obtain the radiated near-field of a component (microcontroller) and to obtain the field of a complete electronic board.

201 citations


Additional excerpts

  • ...The same study [7] has been carried out by applying an equivalent electric current....

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Journal ArticleDOI
TL;DR: In this paper, the equivalence principle is applied to the inverse-source problem, where equivalent sources and/or flelds are computed on an arbitrary 3D closed surface from the knowledge of complex vector electric fleld data at a specifled (exterior) surface.
Abstract: This paper describes in detail difierent formulations of the inverse-source problem, whereby equivalent sources and/or flelds are to be computed on an arbitrary 3-D closed surface from the knowledge of complex vector electric fleld data at a specifled (exterior) surface. The starting point is the analysis of the formulation in terms of the Equivalence Principle, of the possible choices for the internal flelds, and of their practical impact. Love's (zero interior fleld) equivalence is the only equivalence form that yields currents directly related to the flelds on the reconstruction surface; its enforcement results in a pair of coupled integral equations. Formulations resulting in a single integral equation are also analyzed. The flrst is the single-equation, two-current formulation which is most common in current literature, in which no interior fleld condition is enforced. The single-current (electric or magnetic) formulation deriving from continuity enforcement of one fleld is also introduced and analyzed. Single-equation formulations result in a simpler implementation and a lower computational load than the dual-equation formulation, but numerical tests with synthetic data support the beneflts of the latter. The spectrum of the involved (discretized) operators clearly shows a relation with the theoretical Degrees of Freedom (DoF) of the measured fleld for the dual-equation formulation that guarantees extraction of these DoF; this is absent in the single-equation formulation. Examples conflrm that single- equation formulations do not yield Love's currents, as observed both with comparison with reference data and via energetic considerations. The presentation is concluded with a test on measured data which shows the stability and usefulness of the dual-equation formulation in a situation of practical relevance.

160 citations

Journal ArticleDOI
TL;DR: In this paper, a dual integral-equation formulation of the source reconstruction problem on arbitrary three-dimensional (3D) surfaces based on integral equations is presented. But the authors do not consider the problem of source reconstruction on arbitrary 3D surfaces, and they use boundary integral field identities to enforce that the unknown currents are Maxwellian on the reconstruction surface.
Abstract: This paper presents a novel formulation of the source reconstruction problem on arbitrary three-dimensional (3-D) surfaces based on integral equations. Rigorous boundary integral field identities are employed to enforce that the two unknown currents are Maxwellian on the reconstruction surface; this leads to a dual integral-equation formulation, in contrast to the single-equation formulation found in literature. Numerical tests against reference currents allow a quantitative assessment of the improvements in accuracy afforded by the novel formulation, with important benefits in diagnostic applications.

152 citations


Cites methods from "Near-field to near/far-field transf..."

  • ...[1] presents the application of the equivalent magnetic current approach in near-to-far-field transformation, discussing the possibility of obtaining a globally valid pattern representation; [2] and [3] present a similar application, and the method is compared to wave expansion techniques; [4] and [5] address global field extrapolation from its knowledge on a limited region using equivalent planar electric or planar magnetic currents....

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Journal ArticleDOI
TL;DR: In this article, a new method for predicting the far-field radiated emissions and for finding the radiation sources of a device from near-field measurements is presented, based on the substitution of the original device by an equivalent set of elemental dipoles, placed over the main radiating sources, which radiate the same near field (and therefore, farfield).
Abstract: A new method for predicting the far-field radiated emissions and for finding the radiation sources of a device from near-field measurements is presented. It is based on the substitution of the original device by an equivalent set of elemental dipoles, placed over the main radiating sources, which radiate the same near-field (and therefore, far-field). This equivalent set of elemental dipoles is generated using a genetic algorithm. From the position and type of the equivalent elemental dipoles, the position of the actual radiating sources is determined. Since the field produced by an elemental dipole is known, the far-field radiation of the actual radiating source can be calculated. The new method has been tested using synthetic data and real measurements from the radiation generated by a modem PCB demonstrating its viability and usefulness.

148 citations

References
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Book
01 Jan 1968
TL;DR: This first book to explore the computation of electromagnetic fields by the most popular method for the numerical solution to electromagnetic field problems presents a unified approach to moment methods by employing the concepts of linear spaces and functional analysis.
Abstract: From the Publisher: "An IEEE reprinting of this classic 1968 edition, FIELD COMPUTATION BY MOMENT METHODS is the first book to explore the computation of electromagnetic fields by the most popular method for the numerical solution to electromagnetic field problems. It presents a unified approach to moment methods by employing the concepts of linear spaces and functional analysis. Written especially for those who have a minimal amount of experience in electromagnetic theory, this book illustrates theoretical and mathematical concepts to prepare all readers with the skills they need to apply the method of moments to new, engineering-related problems.Written especially for those who have a minimal amount of experience in electromagnetic theory, theoretical and mathematical concepts are illustrated by examples that prepare all readers with the skills they need to apply the method of moments to new, engineering-related problems."

6,593 citations

Book
01 Jun 1961
TL;DR: In this paper, a revised version of the Revised edition of the book has been published, with a new introduction to the concept of plane wave functions and spherical wave functions, as well as a detailed discussion of the properties of these functions.
Abstract: Foreword to the Revised Edition. Preface. Fundamental Concepts. Introduction to Waves. Some Theorems and Concepts. Plane Wave Functions. Cylindrical Wave Functions. Spherical Wave Functions. Perturbational and Variational Techniques. Microwave Networks. Appendix A: Vector Analysis. Appendix B: Complex Permittivities. Appendix C: Fourier Series and Integrals. Appendix D: Bessel Functions. Appendix E: Legendre Functions. Bibliography. Index.

5,655 citations


"Near-field to near/far-field transf..." refers background or methods in this paper

  • ...Since we are interested only in the electromagnetic field in the region where , we place a perfect magnetic conductor in front of the radiating antenna extending to infinity in the and directions on the plane of the antenna....

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  • ...In this approach, by using the equivalence principle [13], an equivalent electric current replaces the radiating antenna....

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Journal ArticleDOI
TL;DR: In this paper, a brief history of near-field antenna measurements with and without probe correction is outlined, beginning with ideal probe scanning on arbitrary surfaces and ending with arbitrary probes scanning on planar, cylindrical, and spherical surfaces.
Abstract: After a brief history of near-field antenna measurements with and without probe correction, the theory of near-field antenna measurements is outlined beginning with ideal probes scanning on arbitrary surfaces and ending with arbitrary probes scanning on planar, cylindrical, and spherical surfaces. Probe correction is introduced for all three measurement geometries as a slight modification to the ideal probe expressions. Sampling theorems are applied to determine the required data-point spacing, and efficient computational methods along with their computer run times are discussed. The major sources of experimental error defining the accuracy of typical planar near-field measurement facilities are reviewed, and present limitations of planar, cylindrical, and spherical near-field scanning are identified.

950 citations

Journal ArticleDOI
TL;DR: In this article, an electric field integral equation (EFIE) is developed to relate the near fields to the equivalent magnetic currents, and the method of moments is used to transform the integral equation into a matrix one.
Abstract: An alternative method is presented for computing far-field antenna patterns from near-field measurements. The method utilizes the near-field data to determine equivalent magnetic current sources over a fictitious planar surface that encompasses the antenna, and these currents are used to ascertain the far fields. Under certain approximations, the currents should produce the correct far fields in all regions in front of the antenna regardless of the geometry over which the near-field measurements are made. An electric field integral equation (EFIE) is developed to relate the near fields to the equivalent magnetic currents. The method of moments is used to transform the integral equation into a matrix one. The matrix equation is solved with the conjugate gradient method, and in the case of a rectangular matrix, a least-squares solution for the currents is found without explicitly computing the normal form of the equation. Near-field to far-field transformation for planar scanning may be efficiently performed under certain conditions. Numerical results are presented for several antenna configurations. >

260 citations