An Analysis of the Rotational Symmetry of the Inner Field of Radial Line Slot Antennas

Masaharu TAKAHASHI  Makoto ANDO  Naohisa GOTO  

IEICE TRANSACTIONS on Communications   Vol.E77-B   No.10   pp.1256-1263
Publication Date: 1994/10/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Antennas and Propagation
RLSA,  radial waveguide,  planar antenna,  method of moment,  rotational symmetry,  inner field,  

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A radial line slot antenna (RLSA) is a slotted waveguide planar array for the direct broadcast from satellite (DBS) subscriber antennas. A single-layered RLSA (SL-RLSA) is excited by a radially outward traveling wave. The antenna efficiency of more than 85% has already been realized. These antennas are designed on the assumption of perfectly rotationally symmetrical traveling wave excitation; the slot design is based upon the analysis of a slot pair on the rectangular waveguide model with periodic boundary walls. However, the slots perturb the inner field and the actual antenna operation is not perfectly symmetrical. This causes the efficiency reduction especially for very small size antenna. This paper presents a fundamental analysis of the inner field of the radial waveguide. It is impossible to analyze all the slot pairs in the aperture as it is and only the slots in the inner few turns are considered since these provide dominant perturbation. The calculated results are verified by the experiments and reasonable agreement is demonstrated. Some design policies are suggested for enhancing the rotational symmetry.