Micro-Analysis of the Radiation Mechanism of High-Gain Pyramidal Horn Antennas

Abstract The conventional model of horn-antenna radiation requires further examination to understand important aspects of the radiation process, particularly the formation of the far-field radiation pattern, the configuration and evolution of the electric field, and the formation of the closed-loop spherical wavefront. To address these aspects and examine the limitations of the conventional model, a new radiation model for a long pyramidal horn antenna is proposed. This model provides a qualitative and logical framework for describing the transition of the electromagnetic field from the guided region to the radiated field and for examining the formation of the resulting radiation pattern. The model consists of two complementary parts: (i) an electrostatic model, which describes the charge and electric-field distributions associated with the antenna structure at a given instant, and (ii) a dynamic radiation model, which describes the time-varying electromagnetic field structures and their propagation into free space through the horn antenna. The proposed new model establishes that the radiation mechanism of a pyramidal horn antenna solely depends on the radiation produced by an equivalent array of dipoles distributed along the inner surfaces of the horn antenna and responsible for radiation pattern formation.