A heuristic model for the transmission cross section of wire-mesh covered apertures

Abstract

A simple and low-cost solution for protecting sensitive equipment located behind an aperture in an enclosure, such as a ventilation or display panel, is to use a metallic wire-mesh to cover the aperture(s). At high frequencies, where the aperture transmission coefficient is close to one, the transmission properties depend almost exclusively on the wire-mesh properties. Analytic models for the transmission coefficient of periodic (infinite) wire-meshes can then be used to provide a good approximation of the transmission properties of the wire-mesh covered aperture. At lower frequencies, however, the situation is more complex, since the transmission properties depend also on the size and shape of the aperture. An analytic model for the transmission cross section of wire-mesh covered apertures is proposed in this paper. At low frequencies this is based on a combination of the transmission cross section of a single wire-mesh cell calculated using the magnetic polarizability and a power relation, derived from antenna theory, relating the power transmitted through an array of apertures to the power transmitted through a single aperture. At intermediate frequencies the model assumes a frequency dependence found heuristically through numerical simulations. The proposed model provides results in very good agreement with numerical results over a wide range of frequencies and wire-meshes.