A Valid Evaluation Method for Electromagnetic Shielding Efficiency of Metallic Mesh Based on Free-Space Reflection Measurement

Metallic mesh is an important transparent electromagnetic shielding component with applications in many fields. When metallic mesh has been assembled to the shielding enclosure and in use, direct evaluation of the shielding efficiency (SE) through common transmission method becomes difficult. In this study, we proposed a valid evaluation method for the SE of metallic mesh based on reflection measurement for the first time, which allows measurement to be performed at one side of the shielding components. By modeling the metallic mesh as a two-port network, we established the relationship between the SE and reflection coefficient through the transmission matrix in the case that the equivalent admittance Y of the metallic mesh is unknown before testing. In a nonanechoic environment, the experiment demonstrated the maximum test deviation was 0.95 dB for the testing sample with SE greater than 15 dB in the Ku-band (12-18 GHz) compared with the normal SE measurement. Accuracy analysis was carried out to illustrate that it is important to reduce the phase error to control the entire uncertainty. Moreover, extra numerical studies further proved that the proposed method can apply not only to metallic mesh but also to other impedance film-substrate bilayer structures such as meshed frequency selection surface (FSS) and semiconductor films.