This standard specifies the measurement method for the shielding effectiveness of electromagnetic shielding materials in the frequency range of 10kHz to 40GHz. This standard is applicable to the measurement of the shielding effectiveness of electromagnetic shielding materials such as metal mesh, conductive film, conductive glass, conductive cloth, conductive medium plate, conductive rubber plate, surface coated or coated with conductive layer, conductive pad, etc. The measurement of shielding effectiveness of ventilation waveguide can also refer to this method 2 Normative References: The clauses in the following documents become the clauses of this standard through reference in this standard. For dated reference documents, all subsequent amendments (excluding corrected content) or revisions are not applicable to this standard. However, parties to agreements based on this standard are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest version applies to this standard. GB/T 12190 Measurement Method for Shielding Effectiveness of Electromagnetic Shielding Rooms GJB 72 Electromagnetic Interference and Electromagnetic Compatibility Terminology 3 Definitions GJB 72 establishes and the following terms and definitions apply to this standard. 3.1 Shielding effectiveness The ratio of the power or field strength received without shielding material to the power or field strength received with shielding material at the same excitation level, expressed in logarithm. 4 General requirements 4.1 Measurement conditions Laboratory environmental requirements: a) Environmental temperature: 15 ℃~30 ℃; b) Environmental relative humidity: less than 80%. 4.2 Measurement Equipment and Facilities 4.2.1 Shielding Room Shielding room is used for measuring shielding effectiveness between 10kHz and 40GHz. The shielding effectiveness of the shielding room should be at least 6dB greater than the shielding effectiveness of the tested material. Shielded semi darkrooms or shielded fully darkrooms can also be used. The shielding room test window is square, with a side length of no less than 0.6m, and the applicable frequency range is_ 10KHz~40GHz, the center of the square hole should be no less than 1m from the ground of the shielding room, and the boundary of the square hole should be no less than 0.5m from the side wall. The width of the flange along the edge of the square hole should not be less than 25mm, and the flange should be treated with conductivity. If only used for 1GHz~40GHz shielding effectiveness measurement, the test window size can be 0.3m × 0.3m, with a boundary distance of no less than 0.1m from the sidewall, and a flange width of no less than 25mm along the edge of the square hole. The flange should be conductive and ensure that the edge of the antenna in the shielding room is no less than 0.1m from the sidewall. Shielded black boxes can also be used. 4.2.2 Flange coaxial device The flange coaxial device is suitable for measuring shielding effectiveness between 30MHz and 1.5GHz, and its technical specifications are as follows: a) Characteristic impedance: 50Q2; b) Voltage standing wave ratio: less than 1.2; c) Transmission loss: less than 1dB