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
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