In our rapidly advancing electronic era, humans are becoming increasingly inundated with electronic devices, resulting in an unprecedentedly complex electromagnetic landscape. This has increased the demand for optical windows that can effectively shield against electromagnetic interference in fields such as aerospace, mobile communication, and optics. These optical windows must not only possess exceptional transmittance in the visible and near-infrared spectra, but also exhibit robust electromagnetic interference-shielding capabilities in the microwave range. The double-line ring metal mesh has attracted significant attention because of its superior transmittance in the visible and near-infrared spectra coupled with its formidable electromagnetic-shielding effectiveness in the microwave and radiowave ranges. Although grid metal meshes are widely used, they face inherent challenges in striking a balance between high optical transmittance and potent electromagnetic-shielding effectiveness. Additionally, periodic metal meshes can significantly affect the imaging quality of optical windows owing to the concentration of diffracted energy. To address these issues, we introduced an innovative random double-line ring metal mesh, which is based on a single-layer metal mesh design. Compared to a grid metal mesh, our proposed structure exhibits significantly improved electromagnetic interference-shielding effectiveness while ensuring a more uniform diffracted energy distribution. We believe that this novel structural design will significantly advance the practical application of metal meshes in the electromagnetic interference shielding of optical windows.

This study focused on the simulation analysis of a random double-line ring metal mesh. First, the shielding effectiveness of random double-line metal meshes with different degrees of randomness and gaps between the dual lines was simulated and analyzed. The shielding effectiveness of random double-line ring metal meshes with rings of different radii at different degrees of randomness were also examined. In addition, the effects of the period and line width on the shielding effectiveness of random double-line ring metal meshes and the influence of randomness on the shielding effectiveness and obscuration ratio of the metal meshes were compared. Furthermore, the diffraction energy distributions of square, double-line, and random double-line ring metal meshes with different degrees of randomness were compared and analyzed. Moreover, by restricting the random direction, the diffraction energy distribution of random double-line ring metal meshes in different random directions was analyzed.

Random double-line ring metal mesh demonstrated exceptional shielding effectiveness against electromagnetic interference. A comparative analysis of the electromagnetic interference-shielding effectiveness between random double-line metal meshes at different double-line gap levels indicates a significant improvement of 7.7617 dB when expanding the metal double-line gap of the mesh from 0 to 110 μm. Furthermore, an evaluation of the electromagnetic interference-shielding effectiveness curves of random double-line ring metal mesh with varying ring radii reveals an increased improvement of 5.2512 dB as the ring radius increases from 130 to 210 μm. On average, the shielding effectiveness of the random double-line ring metal mesh reaches an impressive value of 29.232 dB, representing about twofold improvement over the square metal mesh (Fig.2). In particular, the effect of randomness on the shielding effectiveness of the metal mesh is minimal (Fig.4). The diffraction distribution characteristics indicate that periodic structures, such as square metal meshes, double-line metal meshes, and double-line ring metal meshes, often exhibit concentrated diffraction patterns. However, the introduction of randomness effectively mitigates this issue, resulting in a more evenly distributed diffraction pattern (Fig.6). In addition, the limitations imposed by the introduction of randomness in higher-order diffraction were further elucidated by restricting the random orientation of the random double-line ring metal mesh (Fig.7).

In this study, we propose a transparent random double-line ring metal mesh structure that exhibits high electromagnetic interference-shielding effectiveness and strong antidiffraction capabilities. Compared with square metal meshes, the proposed structure composed of a double-line metal mesh and a circular metal mesh significantly improves the electromagnetic interference-shielding effectiveness. In addition, because of its unique random mechanism, the normalized diffraction energy distribution of the structure is more uniform than that of square metal meshes, and the maximum high-order diffraction energy decreases significantly. The simulation results show that the electromagnetic interference-shielding effectiveness of the random double-line ring metal mesh remains above 25.5666 dB within the frequency range of 5?35 GHz, and the normalized maximum high-order diffraction energy decreases by more than 0.4 dB compared to square metal meshes while maintaining an obscuration ratio higher than 87%. These findings highlight the tremendous value of random double-line ring metal meshes in research on optically transparent electromagnetic interference-shielding optical windows.