Fields in the near zone of the multiple ring antenna arrays with arbitrary distance between radiators

Abstract

Background. The behavior of electromagnetic waves at a finite distance from multi-ring antenna arrays in their near and intermediate observation zones has not yet been studied to a degree sufficient for modern practice queries. For many applications, it is important to know the formation of the searchlight beam in the near zone of multi-ring antenna arrays and the amplitude, phase, and polarization characteristics of the fields in the near field when the electrical dimensions of the antenna and the distance between the radiators change. Objectives: The aim of the work is a theoretical study of the amplitude and phase characteristics of the electromagnetic field in the near and intermediate zones of multi-ring flat equidistant antenna arrays of isotropic radiators. Methods and methodology Research is based on the principle of superposition, methods of the theory of functions of a complex variable, and modern methods of computational mathematics. As a result of computer simulation, when changing the diameter of the aperture of the antenna, the distance between the radiators and the length of the working wave, the behavior of electromagnetic waves in the near zone of multi-ring antenna arrays is studied. Results: The software has been developed for calculating the amplitude and phase characteristics of electromagnetic fields in the near zone of multi-ring equidistant antenna arrays of isotropic radiators. The amplitudes and phases of the electric field vector are calculated with a change in the aperture diameter from 0.5 to 200 wavelengths. The distance between the radiators was chosen equal to half the wavelength for classical phased antenna arrays, 0.9 wavelength for unphased arrays with a global maximum gain and 1.23 wavelength for unphased arrays with a global minimum gain. It is shown that for aperture diameters smaller than 1 - 1.5 wavelengths, the field amplitude in the direction normal to the aperture decreases monotonously with increasing distance, which is typical for linear gratings. With large aperture diameters, a spotlight beam is formed in the near zone, in which large field amplitude oscillations take place (“dead zones” in the near zone of the antenna). The phenomenon of an abnormal increase in the field amplitude outside the searchlight beam in the near zone of rarefied ring gratings was discovered. Conclusions: The developed software for solving the problem of finding of the characteristic electromagnetic fields in the near zone of multi-ring antenna arrays, the results obtained and the discovered physical laws of field behavior must be taken into account when creating electronic devices and systems that use electromagnetic fields in the near zone of antennas. The results of the paper can be generalized to the case of multi-ring and other arrays of weakly directed radiators of any known type.