Absorber lined shielded enclosure (ALSE) method of automotive electromagnetic compatibility (EMC) standard CISPR 25, also called the antenna method, requires a large anechoic chamber. However, the main measure of this method is the common-mode current distribution of the test cable bundle. Since this current distribution can be measured easily by current clamps that have much lower demands to the environment, it is possible to predict the level of radiated fields from the measured current distribution. This paper presents a field prediction method, which combines a measured common-mode (CM) current distribution with numerical computations for the radiated fields in the frequency range of 30~1 000MHz. Accordingly, three major problems can be solved compared with ALSE method. First, fast Fourier transform (FFT) based time-domain current or fitting algorithm based frequency-domain current amplitude can derive the needed phase distribution, for estimating the electric fields. Second, the radiation level produced by the common mode current can be calculated based on the common-mode radiation models of a cable bundle and a ground plate. Third, a calibration method is proposed to take into account the actual test environment of ALSE. Different solution approaches have verified the proposed prediction method.%汽车电磁兼容标准CISPR 25中的线性吸收屏蔽室(ALSE)测试法,又称天线法,需要昂贵的半波暗室作为测试环境.文中方法的主要测试量是线束上共模电流所产生的辐射电场,而线束上的共模电流能通过低成本的电流探头直接测量得到,因此基于线束共模电流测量的辐射发射预测成为可能.相对于ALSE测量法,该方法具有低成本,便利的优势.为了与标准的ALSE测试法在30~1000MHz 的测量结果进行对比,主要解决了三方面的问题:首先,通过对时域电流信号的快速傅里叶变换(FFT)或对频域电流幅值的拟合获取辐射预测所必需的共模电流相位;其次,基于多电偶极子的线束辐射模型与基于表面电流法的导电桌面辐射模型能有效地计算出共模电流所产生的辐射水平;最后,提出的校准方法能将ALSE实际测试环境因素考虑到预测结果中.多个不同的实际测试案例,验证了基于共模电流测量的辐射预测方法的可行性与实用性.
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