金属通信电缆测试方法 第 4-4 部分：电磁兼容性（EMC） 测量高达 3 GHz 及以上的屏蔽衰减的测试方法，三轴法

[中文适用范围]： 本部分IEC 62153描述了确定金属通信电缆屏蔽层屏蔽衰减（a_s）的测试方法。由于同心外管的存在，测量结果独立于周长上的不规则性和外部电磁场。可以使用宽动态频率范围进行测试，即使对于超屏蔽电缆，也能使用普通仪器从低频一直测试到外电路中定义横波的限制（约4 GHz）。 [外文原描述]： IEC 62153-4-4:2015(E) describes a test method to determine the screening attenuation as of metallic communication cable screens. Due to the concentric outer tube, measurements are independent of irregularities on the circumference and outer electromagnetic field. A wide dynamic frequency range can be applied to test even super-screened cables with normal instrumentation from low frequencies up to the limit of defined transversal waves in the outer circuit at approximately 4 GHz. This second edition cancels and replaces the first edition, published in 2006 and constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - Impedance matching adapters are no longer required when measuring devices have a characteristic impedance different from the characteristic impedance of the test equipment; - The reflection loss due to a mismatch is taken into account by a (calculated) correction factor.