金属通信电缆试验方法.第4-9部分:电磁兼容性（EMC）.屏蔽平衡电缆的耦合衰减.三轴法

[中文适用范围]： 本部分IEC 62153适用于金属通信电缆。它规定了一种测试方法，用于确定屏蔽平衡电缆的耦合衰减a_C。由于同轴外管的存在，测量结果不受圆周不规则性和外部电磁场的影响。 可以应用宽动态范围和频率范围来测试甚至超屏蔽电缆，使用普通仪器从低频到外电路中定义的横向波的极限，大约4 GHz。然而，当使用平衡器时，上限频率受到平衡器特性的限制。 测量可以采用标准管程序（即标准测试头）按照IEC 62153-4-4进行，或者采用开管（开放测试头）程序。 本文描述的测量耦合衰减a_C的程序基于测量屏蔽衰减a_S的程序，按照IEC 62153-4-4。 [外文原描述]： IEC 62153-4-9:2018 RLV contains both the official IEC International Standard and its Redline version. The Redline version is available in English only and provides you with a quick and easy way to compare all the changes between the official IEC Standard and its previous edition. IEC 62153-4-9:2018 applies to metallic communication cables. It specifies a test method for determining the coupling attenuation aC of screened balanced cables. Due to the concentric outer tube, measurements are independent of irregularities on the circumference and external electromagnetic fields. A wide dynamic and 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. However, when using a balun, the upper frequency is limited by the properties of the balun. Measurements can be performed with standard tube procedure (respectively with standard test head) according to IEC 62153-4-4 or with open tube (open test head) procedure. The procedure described herein to measure the coupling attenuation aC is based on the procedure to measure the screening attenuation aS according to IEC 62153-4-4. This second edition cancels and replaces the first edition published in 2008. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: – two test procedures, open head and standard head procedure; – measuring with balun or with multiport respectively mixed mode VNA; – extension of frequency range up to and above 2 GHz.