Antenas helicoidales

European Journal of Scientific Research ISSN 1450-216X Vol.31 No.3 (2009), pp.446-490 © EuroJournals Publishing, Inc. 2009 http://www.eurojournals.com/ejsr.htm

Compact Theory of the Broadband Elliptical Helical Antenna
S. Adeniyi Adekola Corresponding Author Professor (also Head of Department, Electrical/Electronics Engineering Department, Niger Delta University, Wilberforce Island, Yenegoa,Nigeria) Communications Group, Department of Electrical and Electronics Engineering University of Lagos, Akoka, Lagos, Nigeria E-mail: sulaiman_adekola@yahoo.com A. Ike Mowete Associate Professor, Communications Group Department of Electrical and Electronics Engineering University of Lagos, Akoka, Lagos, Nigeria E-mail: mowete@mac.com A. Ayotunde Ayorinde Lecturer Communications Group, Departmentof Electrical and Electronics Engineering University of Lagos, Akoka, Lagos, Nigeria E-mail: aaayorinde@yahoo.com Abstract The compact theory described in this presentation develops a robust elliptical integro-differential operator, through which, in a novel manner, an expression is derived for the field radiated by a thin-wire elliptical-cylindrical helical antenna, as a general case forthin-wire antennas of regular geometrical shapes. Using the circuit-geometric approach offered by the Method of Moments, analysis in the paper first derives an expression for the radiation field of a thin-wire antenna, whose geometrical shape is an elliptical-cylindrical helix; and then demonstrates that the expression reduces to those for other thin-wire antennas of regular geometrical shapes, whenconditions that change the ellipticalcylindrical helical geometry to those other geometries are imposed. Having in this manner, validated the correctness of the formulation, a numerical evaluation is undertaken for the helical antenna mounted on a ground plane of infinite extent, which ground plane serves the purposes of a counterpoise, among a few others, in practical applications. In addition, othercomputational results are presented in the form of response curves for the ‘exclusionmode’ and balanced helixes, and the results are in excellent agreement with experimental data available in the open literature. A number of practical applications are highlighted in the paper, including applications in satellite-, wireless-, and deep-space communications. Keywords: Method of Moments,Elliptical-Cylindrical Helical Antennas, Satellite Communications

Compact Theory of the Broadband Elliptical Helical Antenna

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1. Introduction
First, this introduction focuses particular attention on the major thrust of the paper, including a summary of the main analytical and computational results, which is then followed by a comprehensive literature survey to provide perspective, and thereafter,a description of the organization of the paper. The well-known property of the ellipse as a most versatile geometry has been exploited with a high degree of success to precisely formulate a flexible linear operator in terms of an integrodifferential equation for the radiation field of an elliptical-cylindrical helical antenna. From this operator expression, whose form appears for the first time,to the best of our knowledge, integral equation expressions describing the radiation fields for eight different thin-wire antennas – circular and planar helixes, multi-turn elliptical and circular loops, single-turn elliptical and circular loops, and linear vertical and horizontal elements, are readily recovered. And it is a matter of interest to observe that these expressions coincide exactlywith analytical results reported in the literature for those antenna structures; thus serving as a check of the correctness of the formulation presented in the paper. Using the Method of Moments (MoM) as an analytical tool and through an application of the image theory, numerical results are computed for the special case of a right-circular helix mounted on a ground plane of infinite extent. For...