An Approximate Model for Near-Field Calculation of Phased Array

Abstract

This paper presents the application of an effective aperture (EA) model for the near-field (NF) calculation on the main beam axis of a scanned phased array (PA) with arbitrary aperture shape and uniform amplitude distribution. An EA model presents a realistic approximation of PA functioning principles that had earlier been applied for only far-field calculations. The proposed method is based on the scalar wave theory and a representation of a two-dimensional Rayleigh-Sommerfeld diffraction integral for the field intensity of flat aperture in the form of a one-dimensional parametric integral around the perimeter of the aperture, as obtained by Dubra and Ferrari. The method attempts to simplify the near-field calculations of PA using the general parameters of an antenna. An accuracy analysis of NF simulation results for elliptical and rectangular PA has been completed. The limitations for the minimal NF distance and the maximal scan angle as a function of array dimensions have been obtained. A comparison of the EA results of the NF calculation with NF simulations using electromagnetic software FEKO demonstrates a positive correlation. The method shows that the NF of PA with a scanned beam, as a rule, has greater field intensity in comparison with the broadside direction of radiation at the same distance from the aperture. Therefore, PA presents an increased risk of human exposure and electromagnetic interference in the NF region.