Random coupling model for the radiation of irregular apertures

Abstract

AbstractIn this work, we extend results on the coupling of radiation through apertures inside wave chaotic electromagnetic cavities to the short‐wavelength limit. The aperture is assumed to have irregular and smooth boundary geometry. A statistical approach is then used to model both fields in the aperture and in the plane of the aperture. Particular emphasis is devoted to the calculation of the free‐space or radiation aperture admittance matrix, whose ensemble averaged element takes a simple closed‐form expression. The radiation admittance matrix is found to be purely diagonal at relatively short wavelength, and it exhibits unusual frequency behavior. The extreme scenario of an irregular aperture radiating inside an irregular cavity is represented through the random coupling model. This mathematical framework uses a limited number of details of both the aperture and the environment in those problems involving the coupling of an external radiation. The universal fluctuation of the effective area of an electrically large aperture is found for a wave chaotic cavity at variable losses. Results are expected to be useful for the physical understanding of scattering in extremely complicated environments, mode‐stirred reverberation chambers, wireless channels, radar traces, and statistical optics.