A new method of analysis of the near and far fields of paraboloidal reflectors
TL;DR: An analytical technique for predicting accurately the near (electric and magnetic) fields as well as the far fields of a reflector antenna with a pencil beam is presented in this article, which involves the near field geometrical theory of diffraction (GTD) analysis of reflector antennas developed earlier and spherical vector mode functions.
Abstract: An analytical technique for predicting accurately the near (electric and magnetic) fields as well as the far fields of a reflector antenna with a pencil beam is presented. The technique proposed involves the near-field geometrical theory of diffraction (GTD) analysis of reflector antennas developed earlier and spherical vector mode functions. The proposed technique does not place any restriction on the range of polar angles or radial distances of the observation point. It is demonstrated that the technique proposed can predict the fields radiated by the reflector with greater accuracy by comparing the calculated results with the available measured results. A few important applications of the analysis proposed are also highlighted.
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TL;DR: In this article, a simple geometric derivation of the equation for designing an offset dual reflector antenna with perfect rotational symmetry and zero cross polarization is given, which is the same as the one presented in this paper.
Abstract: A simple geometric derivation is given of the equation for designing an offset dual reflector antenna with perfect rotational symmetry and zero cross polarization.
18 citations
TL;DR: An exact analysis for deriving closed-form expressions for the coefficients of free-space spherical modes radiated by typical linear, array, and aperture type of antennas is presented in this article.
Abstract: An exact analysis for deriving closed-form expressions for the coefficients of free-space spherical modes radiated by typical linear, array, and aperture type of antennas is presented. This analysis is employed to determine the number of spherical modes required to reconstruct the near/ far fields (NF/FF) with a prescribed accuracy. The analysis developed together with the theory of probe-compensated spherical scanning is also employed to arrive at a criterion for the minimum distance of separation between the probe and test antenna which will enable accurate nonprobe corrected spherical scanning possible.
15 citations
TL;DR: The spherical near field geometrical theory of diffraction (SNFGTD) method as discussed by the authors is an extended aperture method by which the near field from an antenna is computed on a spherical surface enclosing the antenna using the Geometrical Theory of Diffraction.
Abstract: The spherical near-field geometrical theory of diffraction (SNFGTD) method is an extended aperture method by which the near field from an antenna is computed on a spherical surface enclosing the antenna using the geometrical theory of diffraction. The far field is subsequently found by means of a spherical near-field to far-field transformation based on a spherical wave expansion of the near field. Due to the properties of the SNF-transformation, the total far field may be obtained as a sum of transformed contributions which facilitates analysis of collimated beams. It is demonstrated that the method possesses some advantages Over traditional methods of pattern prediction, but also that the accuracy of the method is determined by the quasioptical methods used to calculate the near field.
12 citations
TL;DR: In this article, a type of spherical triangular array composed of turnstile elements is numerically analyzed and discussed, and it is found that the spherical array proposed here is able to scan its beam up to large angle without variation of the directivity and the circular polarization property.
Abstract: Radiation characteristics of a type of spherical triangular array composed of turnstile elements are numerically analyzed and discussed. It is found that the spherical array proposed here is able to scan its beam up to large angle without variation of the directivity and the circular polarization property.
9 citations
TL;DR: In this paper, the authors used the field correlation theorem to determine the power coupled by a prime focus feed associated with a paraboloid which is being illuminated by a uniform plane wave, and computed the front-to-back ratio of unflanged and flanged paraboloids.
Abstract: An analysis is presented which uses the uniform geometrical theory of diffraction for determining the near fields diffracted by a paraboloid either with or without a conical flange attached to its circular rim when an axially propagated plane wave is incident on the concave or convex portion of the paraboloidal reflector. The field correlation theorem is used to determine the power coupled by a prime focus feed associated with the paraboloid which is being illuminated by a uniform plane wave. Based on this analysis, the front-to-back ratio of unflanged and flanged paraboloids is computed. Computed results show satisfactory agreement with the available measured as well as computed results based on alternative procedures. The variation in the on-axis gain on a prime-focus reflector when the feed is displaced from the focus is studied. Typical computed results are presented and compared with the available measured data. Computed results on the front-to-back ratio of paraboloids (flanged or unflanged) illuminated by a PFF whose radiated field exhibits phase variation over a constant radius are also presented. >
5 citations
References
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TL;DR: In this paper, a generalized three-antenna approach is proposed for determining power gain and polarization of antennas at reduced range distances, and the required data are obtained by an extrapolation technique which includes provisions for rigorously evaluating and correcting for errors due to proximity and multipath interference effects.
Abstract: A new technique is described for determining power gain and polarization of antennas at reduced range distances. It is based on a generalized three-antenna approach which, for the first time, permits absolute gain and polarization measurements to be performed without quantitative a priori knowledge of the antennas. The required data are obtained by an extrapolation technique which includes provisions for rigorously evaluating and correcting for errors due to proximity and multipath interference effects. The theoretical basis provides a convenient and powerful approach for describing and solving antenna measurement problems, and the experimental method employed illustrates the utility of this approach. Examples of measurements are included which exhibit errors in gain as small as \pm0.11 dB ( 3\sigma ).
128 citations
01 Jan 1975
TL;DR: In this paper, the geometrical theory of diffraction and its application for thin-wire elements and arrays is discussed. But the authors focus on the application of the method of moments to thin-wires and arrays.
Abstract: Applications of the method of moments to thin-wire elements and arrays.- Characteristic modes for antennas and scatterers.- Some computational aspects of thin-wire modeling.- Stability and convergence of moment method solutions.- The geometrical theory of diffraction and its application.- Reflector antennas.
124 citations
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
01 Apr 1978
TL;DR: In this article, the authors discuss the techniques in antenna measurements and facilities which have evolved over the last decade, including the tapered anechoic chamber, the compact range, and the near-field probing range.
Abstract: This paper discusses the techniques in antenna measurements and facilities which have evolved over the last decade. The facilities include the tapered anechoic chamber, the compact range, and the near-field probing range. The significant advances in obtaining improved measurement accuracy for power gain, polarization, and swept-frequency techniques are also discussed.
95 citations
TL;DR: A procedure is presented for predicting by computer the radiation pattern of an antenna in the presence of a radome, and good agreement between theory and experiment is noted.
Abstract: A procedure is presented for predicting by computer the radiation pattern of an antenna in the presence of a radome. The case of a horn antenna radiating through an actual aircraft radome is treated in detail, and a comparison is made between computed and measured antenna patterns. Good agreement between theory and experiment is noted.
84 citations