Fast Multilayer Radome Computation with Gaussian Beams

We propose a technique to compute the effect of a dielectric multilayer radome. This technique uses a gaussian beam expansion associated with an evaluation of the physical optics spectral integrals using the asymptotic steepest descent path method. Then, we compare an iterative and a global process to take into account the multiple reflections inside the radome. Finally, a numeric validation is performed on a spherical multilayer radome. INTRODUCTION A conventional method used to compute the transmitted and reflected fields by a radome combines plane wave spectrum (PWS), Physical Optics (PO) and Kottler integrals. This technique is however limited by its computation time and by the local planar multilayer approximation. We propose a new approach where the incident field and its interaction with the radome use a gaussian beam formalism. To reduce computation time, two new improvements are developed in this communication: the asymptotic steepest descent path method applied to thin dielectric multilayers and a fast process to take into account multiple reflections inside the radome. Finally, we present the radiation computation of a multilayer spherical radome. The results are compared to those obtained by the PWS-PO method. GAUSSIAN BEAMS EXPANSION Gaussian beams. Gaussian beams are approximate analytical solution to Maxwell’s equations. They depend on the paraxial approximation which requires low diverging beams. Generally, the maximum divergence angle θ from the propagation axis is assumed to be around 20°. The vectorial analytical formulation of a beam propagating along the z direction with an E field polarised along Ox is given by: ( ) ( ) ( ) ( ) ( ) ( ) ⎪ ⎪ ⎩ ⎪⎪ ⎨ ⎧ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ − = ∂ ∂ − =