Choke Ring Circular Waveguide Antenna Analysis and Design Using Geometrical Theory of Diffraction

A simple choke antenna composed mainly of a circular waveguide surrounded by a ring is discussed. The main objective of this paper is developing an analytical model that obtains a wider, yet variable half power beamwidth (HPBW) of the antenna for different applications. By modeling the ring as a parasitic element and the circular waveguide as the feed, high-frequency field-based method Geometrical Theory of Diffraction (GTD) is proposed. Due to the curved geometry of the ring, caustics are present and introduce singularities in the far field radiation pattern solutions. A correcting factor is imported to overcome these discontinuities. At a selected operating frequency of 2.45 GHz, finite element method solver Ansys HFSS is utilized to validate the resulting radiation patterns of GTD. Antenna radiated power and tangential components constant are used to calibrate between GTD and HFSS.