小型机箱屏蔽效能测试技术研究

发布时间：2018-07-10 07:01

本文选题：屏蔽效能 + 混波室　；参考：《东南大学》2016年硕士论文

【摘要】：本文依据IEEE STD 299.1-2013使用嵌套混波室测试小型机箱屏蔽效能的方法,对IEEE STD299.1-2013标准中未能明确的某些方面进行研究。使用嵌套混波室测试小型机箱屏蔽效能的方法已经成为主流的测试方法。由于混波室以及小型机箱内部的电磁场为统计性均匀场,故在测试小型机箱屏蔽效能的时候,机箱内部的电磁场会影响屏蔽效能测试结果,本文分析了频率搅拌方法以及联合搅拌方法测试小型机箱屏蔽效能的重复性问题,以及研究了混波室法测试小型机箱的置信区间和不确定度。实验发现,在搅拌带宽为100 MHz时,使用联合搅拌的采样次数至少为3次,才能够使得测试的置信区间小于3 dB。除此之外,小型机箱内部接收天线为单极子天线,针对单极子天线阻抗匹配不良好的情况,利用小型宽频带的微带天线测试小型机箱的屏蔽效能,实验发现,使用单极子天线测试小型机箱屏蔽效能的结果与使用小型宽带微带天线测试机箱的屏蔽效能的结果相一致,说明单极子天线较大的反射系数对测试小型机箱屏蔽效能没有影响;同时,提出使用网络分析仪的时域功能测试小型机箱的屏蔽效能,利用时域法测试小型机箱屏蔽效能验证嵌套混波室测试小型机箱屏蔽效能的准确性,也提供测试非均匀场分布机箱屏蔽效能的一种方法。不仅如此,为了讨论腔体壁面对机箱屏蔽效能测试的影响,本文从理论上推导了机箱内部靠近机箱金属壁面的接收天线所接收到的功率,通过实验,比较了接收天线距离壁面较近时所测机箱屏蔽效能与理论计算结果之间的关系,当在单极子与腔体壁面的距离为O.15λ的时候,嵌套混波室法测试屏蔽效能比理想情况下测试小型机箱屏蔽效能大3 dB左右。最后,当小型机箱内部含有加载物体的时候,研究加载物体对测试小型机箱屏蔽效能的影响,研究加载物体对机箱内部场分布造成的影响；实验发现,当机箱的Q值大于Q值限值的5倍时,机箱内部的电磁场的场分布仍为瑞利分布。
[Abstract]:Based on IEEE STD 299.1-2013 method of testing shielding effectiveness of small chassis using nested mixing chamber, this paper studies some aspects of IEEE STD299.1-2013 standard which are not clear. The method of using nested mixing chamber to test the shielding efficiency of small chassis has become the mainstream test method. Because the electromagnetic field in the mixing chamber and the small chassis is a statistical uniform field, the electromagnetic field inside the box will affect the shielding effectiveness test results when testing the shielding effectiveness of the small chassis. In this paper, the repeatability of the frequency mixing method and the combined mixing method for testing the shielding effectiveness of small chassis is analyzed, and the confidence interval and uncertainty of the mixing chamber method for testing the small chassis are studied. The experimental results show that when the mixing bandwidth is 100MHz, the sampling frequency of the joint mixing is at least 3 times, so that the confidence interval of the test can be less than 3 dB. In addition, the inner receiving antenna of the small chassis is a monopole antenna. In view of the unfavorable impedance matching of the monopole antenna, the shielding efficiency of the small chassis is tested by using the small broadband microstrip antenna, and the experimental results show that, The results of using monopole antenna to test the shielding efficiency of small chassis are consistent with those of using small wideband microstrip antenna, which shows that the large reflection coefficient of monopole antenna has no effect on the shielding efficiency of small chassis. At the same time, the time domain function of the network analyzer is used to test the shielding effectiveness of the small chassis, and the accuracy of the nested mixing chamber to test the shielding effectiveness of the small case is verified by using the time domain method. A method for testing shielding effectiveness of non-uniform field distribution chassis is also provided. Moreover, in order to discuss the influence of the cavity wall on the shielding effectiveness test of the chassis, this paper theoretically derives the power received by the receiving antenna near the metal wall of the chassis. The relation between the shielding efficiency of the chassis measured when the receiving antenna is close to the wall is compared with the theoretical results. When the distance between the monopole and the cavity wall is 0. 15 位, The shielding effectiveness of the nested mixing chamber is about 3 dB higher than that of the ideal test of small chassis. Finally, when there is a loading object in the small chassis, the effect of the loading object on the shielding effectiveness of the small chassis is studied, and the effect of the loading object on the distribution of the field inside the chassis is studied. When the Q value of the chassis is more than 5 times the limit value of the Q value, the field distribution of the electromagnetic field in the chassis is still Rayleigh distribution.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN03

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