1.1 本试验方法提供了测量平面材料对平面远场电磁波的电磁（EM）屏蔽效能（SE）的程序。根据测量数据，可以计算出电薄试样的磁性（H）源的近场SE值。 2. , 3. 电场SE值也可以从相同的远场数据中计算出来，但其有效性和适用性尚未确定。 1.2 该测量方法在30 MHz至1.5 GHz的频率范围内有效。这些限值并不精确，但基于在较低频率下由于电容耦合减少而导致的位移电流减少，以及在本试验方法中所述试样夹持器尺寸的较高频率下的过度调制（除横向电磁模式（TEM）外的模式激励）。 在此范围内选择任意数量的离散频率。对于导电性、介电常数和磁导率与频率无关的电薄各向同性材料，可能只需要在少数频率下进行测量，因为远场SE值与频率无关。如果材料不是电薄的，或者如果任何参数随频率变化，则在感兴趣的频带内的多个频率下进行测量。 1.3 本试验方法不适用于电缆或连接器。 1.4 单位- 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 本试验方法适用于在垂直入射、远场和平面波条件下（E和H与材料表面相切）测量平面材料的SE。 4.2 测量SE值的不确定性是材料、整个传输线路径的不匹配、测量系统的动态范围和辅助设备精度的函数。 不确定性分析见 附录X1 说明经验丰富的操作员使用良好设备实现不确定性的概率。偏离本试验方法中的程序会增加这种不确定性。 4.3 通过使用远场SE的测量值，可以计算E或H源SE的近似近场值。可以从中的源代码生成程序 附录X2 这适合在个人电脑上使用。 4.4 本试验方法测量反射和吸收引起的净SE。反射和吸收功率测量通过在支架输入端添加校准的双向耦合器来完成。

1.1 This test method provides a procedure for measuring the electromagnetic (EM) shielding effectiveness (SE) of a planar material for a plane, far-field EM wave. From the measured data, near-field SE values can be calculated for magnetic (H) sources for electrically thin specimens. 2 , 3 Electric (E) field SE values are also able to be calculated from this same far-field data, but their validity and applicability have not been established. 1.2 The measurement method is valid over a frequency range of 30 MHz to 1.5 GHz. These limits are not exact, but are based on decreasing displacement current as a result of decreased capacitive coupling at lower frequencies and on overmoding (excitation of modes other than the transverse electromagnetic mode (TEM)) at higher frequencies for the size of specimen holder described in this test method. Select any number of discrete frequencies within this range. For electrically thin, isotropic materials with frequency independent electrical properties of conductivity, permittivity, and permeability, measurements will possibly be needed at only a few frequencies as the far-field SE values will be independent of frequency. If the material is not electrically thin or if any of the parameters vary with frequency, make measurements at several frequencies within the band of interest. 1.3 This test method is not applicable to cables or connectors. 1.4 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 This test method applies to the measurement of SE of planar materials under normal incidence, far-field, plane-wave conditions (E and H tangential to the surface of the material). 4.2 The uncertainty of the measured SE values is a function of material, mismatches throughout the transmission line path, dynamic range of the measurement system, and the accuracy of the ancillary equipment. An uncertainty analysis is given in Appendix X1 to illustrate the probability of uncertainty achieved by an experienced operator using good equipment. Deviations from the procedure in this test method will increase this uncertainty. 4.3 Approximate near-field values of SE can be calculated for both E or H sources by using measured values of far-field SE. A program can be generated from the source code in Appendix X2 that is suitable for use on a personal computer. 4.4 This test method measures the net SE caused by reflection and absorption. The reflected and absorbed power measurement is accomplished by the addition of a calibrated bidirectional coupler to the input of the holder.