Analysis of a circular aperture antenna and its covered dielectric hemispherical radome shell over ground plane: near- and far-zone patterns

Abstract

The analysis of electromagnetic fields radiated in the far zone from a circular aperture antenna has been one of the useful topics in classical antenna textbooks. In this paper, not only the far-zone radiated fields, but also the near-zone radiated fields are considered in this paper. Moreover, electromagnetic fields radiated by the circular aperture antenna in the presence of a dielectric hemispherical shell radome over the ground plane are formulated in closed form. Both the Fresnel and the Fraunhofer fields including and excluding the effects of the dielectric radome are obtained and discussed. Numerical computation is also made to show the difference between the antenna patterns for the near and far zones, and to demonstrate the effects of the dielectric radome on the radiation patterns. The results show the considerable effects due to the dielectric radome. The major and sidelobes of the power patterns in the E- and H-planes change significantly when the inner radius of the radome is comparable to the dimension of the aperture and its thickness is comparable to the wavelength.