K.R. Govind

Bio: K.R. Govind is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Parabolic reflector & Radiation pattern. The author has an hindex of 2, co-authored 2 publications receiving 12 citations.

Radiation characteristics of a corrugated circular cylindrical waveguide horn excited in the TE/sub 11/ mode

Abstract: The design and experimental studies on a corrugated circular cyclindrical waveguide antenna that is feed-excited in the TE/sub 11/ mode with suppressed far-out sidelobes are reported. To reduce the spillover in the region 90 degrees >

Front-to-back ratio of paraboloidal reflectors

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. >

Accurate simulation of reflector antennas by the complex source-dual series approach

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. >

Modal Analysis of All-Walls Longitudinally Corrugated Rectangular Waveguides Using Asymptotic Corrugations Boundary Conditions

Abstract: The asymptotic corrugations boundary conditions (ACBCs) are used together with classical theory of vector potentials and an innovative combination of matrix systems to analyze rectangular waveguides having all four walls being longitudinally (axially) corrugated. One matrix system is composed of the ACBCs of two opposite walls, while the other comprises those of the other pair of corrugated walls. A transcendental characteristic equation is derived, from which the modal dispersion diagram can be obtained, for all three modal wave-tyoes: fast space, slow surface, and evanescent waves. From the formulation, analytical modal field functions in closed form are also acquired. Results of dispersion graphs and modal field distributions generated by this method are compared favorably with those obtained by a commercial full-wave solver.

Front-to-back ratio of paraboloidal reflectors

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. >

Numerical Modeling of Reflector Antennas

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

Development of 2.5D Analytical Regularization Method for reflector antenna analysis

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.