Electromagnetic shielding characteristics of composite microstructures mesh

To solve the difficulty in achieving that strong electromagnetic shielding and high infrared transmission of traditional square metal meshes, composite microstructures, i.e., circle-square, square-circle, hexagon-square, and honeycomb-square structures, exhibiting high electromagnetic interference shielding efficiency (EMI SE) comprising nonhomogeneous nested units have been constructed and demonstrated theoretically and experimentally. These composite microstructures, which are characterized by longer periods and wider line widths, are equivalent to square metal mesh with smaller structural parameters utilizing an equivalent period and line width model that resulted in enhanced EMI SE. Compared with single structures, composite microstructures exhibit a smaller dimensional span. Numerical simulation results demonstrate that an increase in the metal mesh within the composite microstructure reduces the local electric field value, thereby leading to an increased EMI SE value. Practical measurements indicate that, under conditions of comparable infrared transmittance, the average EMI SE values of the circle-square and honeycomb-square structures on a double-sided polished silicon substrate were 33.5 and 34.6 dB at 4-12 GHz, respectively, which are 3.3 and 4.4 dB higher than that of the traditional square structure. Thus, the constructed composite microstructures (circle-square and honeycomb-square) can realize enhanced EMI SE performance while maintaining comparable levels of infrared transmittance. The findings of this study are expected to be of considerable significance in terms of improving the comprehensive performance of graphical optical windows.