Front-to-back ratio of paraboloidal reflectors
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. >
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TL;DR: In this article, the problem is first formulated in terms of the dual series equations and then is regularized by the Riemann-Hilbert problem technique, and the resulting matrix equation is solved numerically with a guaranteed accuracy.
Abstract: The radiation from circular cylindrical reflector antennas is treated in an accurate manner for both polarizations. The problem is first formulated in terms of the dual series equations and then is regularized by the Riemann-Hilbert problem technique. The resulting matrix equation is solved numerically with a guaranteed accuracy, and remarkably little CPU time is needed. The feed directivity is included in the analysis by the complex source point method. Various characteristic patterns are obtained for the front and offset-fed reflector antenna geometries with this analysis, and some comparisons are made with the high frequency techniques. The directivity and radiated power properties are also studied. >
52 citations
30 Jan 2011
TL;DR: In this paper, Rahmat-Samii et al. presented a mathematical model of the single-reflector paraboloid antenna and double-reflectors Paraboloid Cassegrain antenna based on physical optics method.
Abstract: The numerical modeling of reflector antennas is a necessary stage of their design Due to numerical modeling dimensions of all antenna elements are defined The more factors are accounted during antenna numerical modeling the more accurately the antenna elements dimensions are defined There are many methods used in the programs of antenna numerical modeling: geometric optics method; aperture method; geometric theory method of diffraction; physical optics method, integral equations method; finite elements method By now there are many papers in which the different aspects of reflector antenna numerical modeling are discussed For determination of the field antenna reflector in regions of main lobe and first side lobes in front semi-space the aperture method is used; for determination of the field in full semi-space the physical optics method is used (Chen & Xu, 1990; Charles, 1975; Rusch, 1974) The geometric theory of diffraction (Narasimhan & Govind, 1991; Rahmat-Samii, 1986; Narasimhan et al, 1981) and moment method (Khayatian & RahmatSamii, 1999) are used for determination of the field in back semi-space, for determination of field features in front semi-space related with diffraction of the field on the edge of paraboloid and hyperboloid surfaces and for modeling the feed-horn In a number of papers different approaches are used for simplification of analytical expressions for calculation of antenna fields to reduce a mathematical model of antenna and to simplify modeling program (Rahmat-Samii, 1987) A number of works deal with research into the field in nearfield zone (Narasimhan & Christopher, 1984; Fitzgerald, 1972; Houshmand et al, 1988; Watson, 1964) But the results are not reduced to numerical data in that volume which is necessary for antenna design The field distribution in near-field zone is described in detail for plane aperture at uniform its excitation (Laybros et al, 2005), but for reflector antennas such research was not provided The reflector antenna in receiving mode is not discussed in literature, however at designing antenna for radioimaging systems it is necessary to know of field distribution in the focal region at receiving of the wave from near-field zone points The issue of isolation of channels in multi-beam reflector antenna at receiving of the wave from near-field zone is not analyzed too Without analysis of the isolation between channels it is impossible to analyze the quality of imaging in radioimaging systems In literature a number of works deal with describing the feed-horns in monopulse reflector antennas (Hannan, 1961; Scolnic, 1970) There is a little information on numerical characteristics description the regularity in monopulse reflector antenna In the present chapter the mathematical model of the single-reflector paraboloid antenna and double-reflector paraboloid Cassegrain antenna is based on physical optics method
3 citations
Cites methods from "Front-to-back ratio of paraboloidal..."
...The geometric theory of diffraction (Narasimhan & Govind, 1991; Rahmat-Samii, 1986; Narasimhan et al, 1981) and moment method (Khayatian & RahmatSamii, 1999) are used for determination of the field in back semi-space, for determination of field features in front semi-space related with diffraction…...
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TL;DR: In this paper, a two-and-a-half dimensional analytical regularization method (2.5D ARM) was proposed to analyze reflector antennas for microwave, millimeter wave or ultra wide band applications.
Abstract: A novel and efficient approach, which is called two-and-a-half dimensional Analytical Regularization Method (2.5D ARM), is proposed to analyse reflector antennas for microwave, millimeter wave or ultra-wide band applications. To present computational performance of the proposed method, its results are compared with well known Physical Optics (PO) and Method of Moments (MoM) solutions for a PEC hollow cylinder and an open-ended corner reflector. Moreover, radiation pattern of a ridged horn fed parabolic reflector antenna is measured to validate the method experimentally. It is observed that either the simulated or the measured data and the 2.5D ARM results are in close agreement with each other.
2 citations
28 Oct 2010
TL;DR: In this article, the authors proposed the method of analytical regularization (MAR) for 3D and 2D reflector antennas in both polarizations, which can provide finer accuracy within a reasonable computation time.
Abstract: The parabolic reflector antennas are widely used in the telecommunication systems and generally have large aperture sizes like 50λ to 80λ and larger Their reliable full-wave analysis with the conventional Method of Moments (MoM) or with the other numerical methods is difficult because of inaccessible speed and accuracy This statement is valid both for 3D and 2D reflector antennas in both polarizations The Method of Analytical Regularization (MAR) constitutes an alternative solution compared to the ordinary MoM, which can provide only 1–2 digit accuracy It provides finer accuracy within a reasonable computation time because the computational error can be decreased simply by increasing the matrix size in MAR We have previously developed this method for the accurate simulation of the arbitrary conical section profile 2D reflector antennas, and the corresponding codes have provided us with accurate benchmark data Here we study a similar problem however with the feed simulated by Complex Source Point (CSP) source located at an off-focus point on the symmetry axis of a front-fed reflector antenna The numerical results are presented for the radiation characteristics including the forward and backward directivities and the radiation patterns in all directions
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TL;DR: In this paper, the radiation characteristics of symmetric parabolic antennas with a peripherical flange are examined in detail in order to assess the effectiveness of such a flange in reducing the backward scattered field.
Abstract: The radiation characteristics of symmetric parabolic antennas with a peripherical flange are examined in detail in order to assess the effectiveness of such a flange in reducing the backward scattered field. It is shown that the best behavior is obtained by using a right-angled flange, which allows achievement af a significant field level reduction in a wide rear angular sector, without affecting the field radiated in the forward directions.
7 citations
TL;DR: In this paper, an analysis of the near or far-field patterns of an offset paraboloid illuminating a rotatable flat reflector for scanning the main beam of the offset reflector is presented.
Abstract: In this paper an analysis of the near- or far-field patterns of an offset paraboloid (fed at its focus) illuminating a rotatable flat reflector for scanning the main beam of the offset reflector is presented. This analysis is based on the near-field GTD analysis developed earlier and the known techniques for transforming near fields to far fields. Computed results on the far-field patterns of a typical offset paraboloid illuminating a flat reflector are presented. Further, the computed results on the far-field patterns of a typical paraboloid illuminating a square flat reflector satisfactorily correlate with the available measured results.
2 citations
TL;DR: In this paper, the radiation characteristics of a paraboloid with a square aperture were analyzed using the uniform geometrical theory of diffraction (UGTD) and the front-to-back (F/B) ratio for different square paraboloids were tabulated.
Abstract: Radiation characteristics of a paraboloid with a square aperture are described in this paper. A systematic analysis of the principal plane radiation patterns of the dish employing the uniform geometrical theory of diffraction (UGTD) [3], [4] reveals that for the square paraboloid the backlobes are weak because there is no caustic at the rear boresight as in the case of circular apertures. Based on the method enunciated in [7] the front-to-back (F/B) ratio for different square paraboloids are also tabulated.
2 citations