Investigation of Electromagnetic Wave Diffraction at the Edges of the Pyramidal Horn Irradiator of the Antenna, as One of the Causes of Scattering

Abstract

The solution to modern practical radio engineering problems involves studying the diffraction of a plane electromagnetic wave at military facilities of complex shapes. Usually, such objects include antenna systems. If an electromagnetic wave falls on them, the primary waves can occur (dissipate), refract, and some of the energy can be absorbed. Consequently, the wave structure changes. Problems of this type are quite complex, and even modern calculation methods based on new computer technologies in combination with current numerical methods do not provide sufficient efficiency in the calculation.
To solve such problems, the causes of scattering are analyzed using the example of aperture antennas. One of these reasons is due to the impact of sharp edges, or the edges of the Horn irradiator. It turned out that it can be complicated to understand the influence of individual edges since an expression describing the shape of an edge can depend on several coordinates. Getting new rigorous analytical solutions is also very difficult, especially for three-dimensional bodies. Numerical solutions do not have analytical expressions, so it is impossible to select formulas components describing the influence of individual parameters or parts of the scatter plot. In this regard, developing new heuristic methods based on knowledge of the physical laws of the diffraction phenomenon is of great importance.
Derivation of a formula for calculating the electric (magnetic) components of an electromagnetic field scattered from the edges of the Horn irradiator with a rectangular opening shape in two main causes of a plane electromagnetic wave incident.
Since antennas are a significant source of secondary radiation and contribute significantly to the scattering of military objects, the Radar cross-section (RCS) of the Horn irradiator is considered, taking into account the edges.
To test the obtained expressions, an experiment was performed to measure a single-position RCS, that is if the angle of incidence of the wave coincides with the observation angle for two cases of the incident of a plane wave on the opened Horn. The RCS measurement of the antenna was performed when it was connected to a matched load, a short-circuited output, and an open feeder, provided that the electromagnetic wave is vertically polarized. Theoretical and experimental results satisfactorily coincide not only qualitatively, but also quantitatively.
The results of the article allow us to develop recommendations for accelerating and clarifying numerical calculations when solving various practical problems, to reduce losses in the antenna by reducing the reflection coefficient.
From the point of view of designing new antennas, it is advisable to use methods to suppress reflection from the edges to eliminate edge scattering. It is recommended to use resistive cone loads, coating the edges with absorbing materials, or corrugating the edges of the horn or other antenna openings.