Random coupling model for the radiation of irregular apertures

In this paper, we propose and investigate the radiation of chaotic apertures. It is assumed that an aperture is wide and its geometry is irregular enough to infer a random behavior of the tangential field, that is expanded in chaotic modes. Particular emphasis is devoted to the calculation of the freespace aperture admittance matrix, whose element average 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 a chaotic aperture radiating inside a chaotic cavity is analyzed by the random coupling model. Transmitted power distribution is generated in various loss conditions, upon oblique planewave excitation of the aperture. It is found that cavity loss and number of aperture modes influence symmetry and fluctuation law of the transmitted power distribution. Obtained results offer a mathematical framework for the physical understanding of scattering in extremely complicated environments, mode-stirred reverberation chambers, wireless channels, radar traces, and statistical optics.