Control of Shielding Effectiveness of Optically Transparent Films by Modification of the Edge Termination Geometry

Abstract

This article deals with the design, fabrication, and characterization of optically transparent electromagnetic screens to protect optical sensors against high-intensity radiated fields. To ensure the best tradeoff between high optical transparency over the entire visible light spectrum and high shielding effectiveness at microwaves, micrometric mesh metal films printed on glass substrates were selected. Changing the micrometric mesh pattern allows reaching various shielding effectiveness values required for different applications, but implies important adjustments of the design and fabrication processes. The variation of the number of contact ribbons between the mesh screen and its direct peripheral area consists of an alternative solution to modify the screen shielding effectiveness, while keeping the meshed part of the screen identical. An analytical model, which predicts the shielding effectiveness variation measured under statistically uniform illumination in a reverberation chamber as a function of the number of metal ribbons and the aperture sizes between them was specifically developed. Experimental results follow the trend predicted by the analytical model. As a result, adjusting the number of peripheral contact ribbons enables the shielding effectiveness to be fitted to specified requirements at constant optical transparency.