The analysis of near and far field pattern through mode analysis and FFT in a finite periodic dielectric gratings

Abstract

Purpose – The purpose of this paper is to analyze far and near field emitted field patterns throughmore exact calculation of the modes formed in finite periodic dielectric gratings.Design/methodology/approach – For the mode calculation, equations are newly defined byapplying vertical boundary condition on the assumption that transverse electric modes are generated inthe structure. After finding modes, near field patterns are calculated using the wave number andcoefficient of the mode.Findings – Additionally, the results from these calculations are compared with that of therigorous-coupled method. Finally, far field patterns are derived by applying fast Fourier transform tonear field patterns and also compared with the results of rigorous-coupled method.Research limitations/implications – For convenience of coordinate, we use rectangularcoordinate, though the shape of radome is a hemisphere.Practical implications – In this paper, the authors derive more exact near field patterns without theassumption of infiniteness so that these results can be used practically for a making realfrequency-selective structure.Originality/value – Conventional periodic finite dielectric gratings analysis has been done usingFloquet–Bloch wave theory, coupled-mode, rigorous-coupled method which is based on the assumptionof infiniteness of the structure. © Emerald Group Publishing Limited.