GTEM小室交叉极化特性及三维场均匀性FDTD分析

Analysis of cross-polarization performance and three-dimensional field uniformity in GTEM cell using FDTD method

采用时域有限差分法评价了1GHz以内吉赫兹横电磁波(GTEM)小室的交叉极化特性和三维场均匀性.根据IEC61000-4-20标准,采用9点网格法分别对测试区的1/3和1/2内导体高度区的场分布特性进行了宽频带分析,并以测试区中心截面的名义场强为参考评估了沿纵向的场均匀性.计算结果表明:在1/3内导体高度区,三维场均匀性满足6dB限制,但工作频率超过一定频带后,交叉极化分量满足小于主分量6dB要求较为困难;随频率和测试区的增大,交叉极化特性和场均匀性下降,但较易满足放松要求.经实验证实计算结果准确可靠.

Both cross-polar coupling and three-dimensional field uniformity of gigahertz transverse electromagnetic （GTEM） cell were evaluated using finite-difference time-domain （FDTD） method at frequencies of up to 1 GHz. A 9-point grid was used to analyze the characterization of electric field distribution within the 1/3 and 1/2 septum height area of the test volume respectively in broad frequency band range according to IEC standard 61000-4-20. The numerical results show that within the 1/3 septum height area, the three-dimensional field uniformity fulfills the required 6 dB limit, but out of certain frequency band the cross-polar components are difficult to meet the 6 dB requirement relative to the primary field strength; moreover, with the increase of frequency or test volume, the cross-polarization performance and field uniformity will degrade but they are relatively easy to satisfy the relaxed requirements. The obtained results are validated by measurements.