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 paper, a technique of transforming the probe uncompensated near-field data to the near or far field is presented, which is useful in near field antenna measurements, when the probe antenna scans over an arbitrary surface enclosing the test antenna.
Abstract: A new technique of transforming the probe uncompensated near-field data to the near or far field is presented, which is useful in nearfield antenna measurements, when the probe antenna scans over an arbitrary surface enclosing the test antenna. The technique presented is analytically simple and sufficiently accurate.
4 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 background from "A new method of analysis of the nea..."
...A number of works deal with research into the field in nearfield zone (Narasimhan & Christopher, 1984; Fitzgerald, 1972; Houshmand et al., 1988; Watson, 1964)....
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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
01 Jan 1996
TL;DR: The method combines the WIPL code (entire-domain Galerkin method applied to geometrical model made of bilinear surfaces) and specific segmentation techniques, thus enabling efficient analysis of the reflectors the diameter of which is up to D=40¿ at personal computers.
Abstract: The paper presents a new method for the analysis of the reflector antennas together with their feeds and supporting structures. The method combines the WIPL code (entire-domain Galerkin method applied to geometrical model made of bilinear surfaces) and specific segmentation techniques, thus enabling efficient analysis of the reflectors the diameter of which is up to D=40? at personal computers. Good agreement with other theoretical and experimental results is observed. In addition, results illustrating the influence of feedsupport struts on the radiation pattern are presented.
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TL;DR: In this paper, a method is presented for evaluating the Q of an antenna, where the Q is defined as in conventional network theory, and the method consists of subtracting the energy density associated with the power flow from the total energy density, thus enabling the magnetic and electric reactive energy to be computed.
Abstract: A method is presented for evaluating the Q of an antenna, where the Q is defined as in conventional network theory. The method consists of subtracting the energy density associated with the power flow from the total energy density, thus enabling the magnetic and electric reactive energy to be computed. Specific application of the method is made to the evaluation of the Q of spherical and cylindrical modes. It is verified that the Q becomes very large when the order of the mode exceeds k_{0}a where a is the radius of the sphere or cylinder on which the sources are located.
479 citations
TL;DR: In this article, a new recursion relation is derived which reduces the computation effort by several orders of magnitude so that a quantitative analysis for spheres as large as 10 λ in radius at a spacing as small as two spheres in contact becomes feasible.
Abstract: Solution to the multiple scattering of electromagnetic (EM) waves by two arbitrary spheres has been pursued first by the multipole expansion method. Previous attempts at numerical solution have been thwarted by the complexity of the translational addition theorem. A new recursion relation is derived which reduces the computation effort by several orders of magnitude so that a quantitative analysis for spheres as large as 10\lambda in radius at a spacing as small as two spheres in contact becomes feasible. Simplification and approximation for various cases are also given. With the availability of exact solution, the usefulness of various approximate solutions can be determined quantitatively. For high frequencies, the ray-optical solution is given for two conducting spheres. In addition to the geometric and creeping wave rays pertaining to each sphere alone, there are rays that undergo multiple reflections, multiple creeps, and combinations of both, called the hybrid rays. Numerical results show that the ray-optical solution can be accurate for spheres as small as \lambda/4 in radius is some cases. Despite some shortcomings, this approach provides much physical insight into the multiple scattering phenomena.
306 citations
TL;DR: In this article, a general solution to the problem of determining first the aperture field distribution and then the transmission and reflection coefficients of an infinite planar conducting sheet perforated periodically with apertures has been formulated.
Abstract: A general solution to the problem of determining first the aperture field distribution and then the transmission and reflection coefficients of an infinite planar conducting sheet perforated periodically with apertures has been formulated. The excitation is considered to be a plane wave incident at any arbitrary angle. The aperture dimensions and array element spacings were assumed to be comparable with the wavelength of the incident electromagnetic field. The solution given can include the effect of a dielectric slab used to support the thin conducting sheet. The solution is obtained by matching the tangential field components at the surface of the screen. The resulting integral equation is solved by the method of moments which reduces the integral equation to a system of linear algebraic equations that can be solved with the use of a digital computer. Accurate results for both the magnitude and phase of the aperture field distribution and the transmission coefficients for the propagating modes are determined explicitly for a specific example of slots arranged in an equilateral triangular lattice. The balance of power flow between the reflected and the transmitted waves has been checked with satisfactory results. The solution can be applied to the problem of scattering from a conducting screen with periodic apertures and to the complementary problem of scattering from a set of conducting plates by the use of Babinet's principle.
265 citations
01 Dec 1973
TL;DR: In this paper, the aperture phase and amplitude distributions are sampled by a scanning field probe, and then the measured distributions are transformed to the far field by a plane wave that is created by a feed and large reflector in the immediate vicinity of the test antenna.
Abstract: In many cases, it is impractical or impossible to make antenna pattern measurements on a conventional far-field range; the distance to the radiating far field may be too long, it may be impractical to move the antenna from its operating environment to an antenna range, or the desired amount of pattern data may require too much time on a far-field range. For these and other reasons, it is often desirable or necessary to determine far-field antenna patterns from measurements made in the radiating near-field region; three basic techniques for accomplishing this have proven to be successful. In the first technique, the aperture phase and amplitude distributions are sampled by a scanning field probe, and then the measured distributions are transformed to the far field. In the second technique, a plane wave that is approximately uniform in amplitude is created by a feed and large reflector in the immediate vicinity of the test antenna. And in the third technique, the test antenna is focused within the radiating near-field region, patterns are measured at the reduced range, and then the antenna is refocused to infinity. Each of these techniques is discussed, and the various advantages and limitations of each technique are presented.
232 citations
TL;DR: The paper gives a survey of the literature concerning the electromagnetic properties of wire grids and some particular grid configurations are mentioned.
Abstract: The paper gives a survey of the literature concerning the electromagnetic properties of wire grids. As an introduction to the literature survey, a short description of the properties and applications of wire grids is given. Finally some particular grid configurations are mentioned.
132 citations