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Journal ArticleDOI

An efficient technique for spherical near-field to far-field transformation and evaluation of far fields of perfectly conducting scatterers

01 Dec 1989-IEEE Transactions on Antennas and Propagation (IEEE)-Vol. 37, Iss: 12, pp 1529-1536
TL;DR: In this paper, an efficient probe-directivity-uncompensated, spherical, near-field-to-far-field (NF-FF) transformation is presented, which does not make use of the spherical vector waver functions (SVWF) in the conventional manner, but views it as an electromagnetic scattering problem.
Abstract: An efficient technique for probe-directivity-uncompensated, spherical, near-field-to-far-field (NF-FF) transformation is presented. The technique does not make use of the spherical vector waver functions (SVWF) in the conventional manner, but seeks to obtain the NF-FF transformation exactly, viewing it as an electromagnetic scattering problem. The problem is formulated by considering the NF-FF transformation, when the FF observation points are restricted to a single phi -plane at a time. The analytical expressions derived toward this end assume a considerably simplified form offering a high level of computational efficiency. The technique is validated by considering arrays as test antennas with a maximum dimension of 150 lambda . Based on the principles employed for the spherical NF-FF transformation, an efficient technique for computing the FF patterns of a perfectly conducting scatterer illuminated by an arbitrary source using the technique of physical optics (PO) is also developed. In order to validate this, typical numerical computations are performed, and the results are discussed. >
Citations
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Patent
02 Aug 2000
TL;DR: In this article, the authors proposed a method for near-field measuring enabling to measure in normal operating conditions, and accurately, all the radiating characteristics of an equipment being tested, including the power radiated, the radiated field pattern at every distance, and the form of the emitted signals associated with the radiiated field patterns of each of said signals.
Abstract: The invention concerns systems for measuring the electric field emitted by any electronic equipment. The invention aims at providing a method for near-field measuring enabling to measure in normal operating conditions, and accurately, all the radiating characteristics of an equipment being tested, including the power radiated, the radiated field pattern at every distance, and the form of the emitted signals associated with the radiated field pattern of each of said signals. The method for determining the radiation emitted by an equipment consists in: producing at least one radiation measurement in the radiating field of the equipment; in performing several sets of simultaneous near-field measurements, within a measuring surface located at a short distance from the equipment; and using a method for processing said sets of performed measurements which consists in estimating the statistical properties of the radiated field at any point outside the measuring surface.

19 citations

Dissertation
11 Jan 2013
TL;DR: In this article, a modelo de canal is proposed to evaluate the degradación caused by the presence of a parque eolico in the difusion of television digital DVB-T debida a the presencia of an aerogenerador.
Abstract: La presencia de un parque eolico provoca una serie de efectos sobre las senales electromagneticas que pueden dar lugar a una degradacion de la calidad de los servicios de telecomunicaciones proporcionados en sus cercanias. En lo que respecta a la difusion de television, el efecto de un parque eolico en la difusion de television digital no habia sido determinado hasta ahora.Por otra parte, la evaluacion de la posible degradacion de estos servicios se ha realizado tradicionalmente mediante modelos que caracterizan la senal dispersada por las aspas del aerogenerador. Estos modelos clasicos de dispersion no contemplan ni la contribucion del mastil a la senal dispersada, ni la variabilidad temporal de la senal dispersada debida a la rotacion de las palas, ni la influencia conjunta de un parque eolico compuesto por varias maquinas.En este contexto, se plantea el primero de los objetivos principales de esta tesis: la evaluacion empirica de la degradacion causada en la recepcion de senales de television digital DVB-T debida a la presencia de un parque eolico. Del estudio realizado, basado en medidas de campo, se concluye que las condiciones de recepcion mas criticas se dan en la zona de backscattering, donde la propagacion responde a las caracteristicas de un canal multitrayecto discreto variante con el tiempo.El segundo objetivo principal de esta tesis se centra en la propuesta un nuevo modelo de canal para caracterizar la propagacion multitrayecto tipica en los alrededores de un parque eolico en esta banda. Este modelo de canal se adapta a las condiciones particulares de cada caso en estudio: posicion relativa transmisor-turbina-receptor, dimensiones del aerogenerador, velocidad maxima de rotacion de las aspas, caracteristicas de los sistemas radiantes del transmisor y receptor, y frecuencia de trabajo.

3 citations

References
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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 paper, a compact approximate asymptotic solution for the field radiated by an antenna on a perfectly conducting smooth convex surface was developed for the GPDD field.
Abstract: A compact approximate asymptotic solution is developed for the field radiated by an antenna on a perfectly conducting smooth convex surface. This high-frequency solution employs the ray coordinates of the geometrical theory of diffraction (GTD). In the shadow region the field radiated by the source propagates along Keller's surface diffracted ray path, whereas in the lit region the incident field propagates along the geometrical optics ray path directly from the source to the field point. These ray fields are expressed in terms of Fock functions which reduce to the geometrical optics field in the deep lit region and remain uniformly valid across the shadow boundary transition region into the deep shadow region. Surface ray torsion, which affects the radiated field in both the shadow and transition regions, appears explicitly in the solution as a torsion factor. The radiation patterns of slots and monopoles on cylinders, cones, and spheroids calculated from this solution agree very well with measured patterns and with patterns calculated from exact solutions.

164 citations

Journal ArticleDOI
TL;DR: In this article, the authors used spherical-wave expansions as a numerical technique for expressing arbitrary fields specified by analytical, experimental, or numerical data, and found that the generally accepted wave order cutoff value corresponds to 99.9 percent or more of the power in the input pattern.
Abstract: Spherical-wave expansions are a well-known technique of expressing electromagnetic field data. However, most previous work has been restricted to idealized cases in which the expansion coefficients are obtained analytically. In this paper spherical-wave expansions are used as a numerical technique for expressing arbitrary fields specified by analytical, experimental, or numerical data. Numerical results on the maximum wave order needed to expand fields arising from a source of a given size are given for two practical cases, and it is found that the generally accepted wave order cutoff value corresponds to 99.9 percent or more of the power in the input pattern. Near-field patterns computed from far-field data are compared to measured data for the two cases, demonstrating the excellent numerical accuracy of the technique.

116 citations

Journal ArticleDOI
TL;DR: In this paper, the radiated far field is determined from a rapidly convergent series representation of the radiation integral, where the coefficients of the series are independent of the observation angles, and the field may be determined very rapidly at large numbers of points.
Abstract: Given the true or any approximate current on a reflector, the radiated far-field is determined from a rapidly convergent series representation of the radiation integral. The leading term is a well-shaped J_{1}(x)/x beam pointing in a desired direction. Higher order terms provide perturbations to the leading term. The coefficients of the series are independent of the observation angles. Hence, once they are computed, the field may be determined very rapidly at large numbers of points. Initially, a suitable small angle approximation is made that places the radiation integral in the form of a Fourier transform on a circular disk. The theory is then extended such that the results are valid in both the near and the wide angle regions. Application to a rotationally symmetric paraboloid is presented herein. Other applications include the offset and dual reflectors and near- to far-field integrations. A modified form of the series can also be used for Fresnel zone computations.

110 citations