振动模式混响室内部电磁特性仿真与试验研究

The deficiency of the available test space, test cycle, maintenance and other aspects of the mechanical stirring reverberation chamber has played a negative role of the popularization and application in the field of electromagnetic compatibility testing. In this project, the electromagnetic field in the reverberation chamber is studied, and a method of making a reverberation chamber by a high performance shielding fabric is proposed. The electromagnetic parameters of materials obtained by the method of testing and inversion prediction model, then the electromagnetic shielding fabric reverberation chamber model could be established; The loss of the antenna, cavity and boundaries were instead of the uniform air loss, then the convergence would be faster, and the computation time could be reduced. The vibrating reverberation chamber was built by disperse the vibrating wall into multiple fixed shape of the reverberation chamber. The vibrate influence of the electric field distribution inside the cavity was calculated, then the relationship between the vibration frequency and the vibration amplitude of the screen and the quality factor of the cavity, the mode density and the electric field distribution could be established. An auxiliary device and automatic control system were manufactured, which were used to vibrate the wall of the cavity. The experimental research can be carry out, to verify the validity and rationality of the theoretical model, and improve the theoretical model, promote the theory and experiment, so as to establish a practical test and effective vibrating reverberation chamber, and provide a new method for the research of electromagnetic compatibility of electronic system.

机械搅拌式混响室在可用测试空间、测试周期、维修保养等方面的不足影响了该技术在电磁兼容测试领域的推广使用。本项目通过研究振动模式混响室内部的电磁场特性，进而提出一种由高性能屏蔽布制作混响室的方法。通过测试和预测模型反演的方法得到材料的电磁特性参数，建立屏蔽布混响室电磁模型；以空气均匀损耗代替天线、腔体、边界等部位的损耗，使得混响室模型计算更快收敛，从而缩短计算时间；通过将腔壁振动离散化为多个外形固定的混响室，建立振动模式的混响室模型；探索屏蔽布的振动频率和振动幅度以及腔体品质因数、模密度、电场分布特性的优化方法，确立屏蔽布振动对腔体内部电场分布的影响规律。研制一种通过步进电机控制腔壁振动辅助装置和自动控制系统，开展试验研究，验证理论建模的有效性和合理性，并改进理论模型，使理论和试验相互促进，从而建立经过实践检验和行之有效的振动模式混响室，为开展电子系统电磁兼容性研究提供一种新方法。

针对现在的机械搅拌器存在的造价昂贵、无法应用于现场测试等现状，开展了振动模式混响室仿真和试验研究，主要研究结论：一是建立了振动模式混响室电磁仿真模型，计算结果显示偶极子天线比对数周期天线对振动模式混响室均匀性改善效果好；场均匀性和天线数量并不严格正相关，单纯增加辐射天线数量并不能改善混响室的统计特性；形变深度和形变表面数量的增加，能够起到增大搅拌效率的效果，最佳形变深度为混响室最短棱边长度的20%。基于电磁计算软件FEKO并结合Python，开发了一套振动模式混响室仿真控制与数据处理软件，可用于预估振动模式混响室的性能，计算结果对于构建振动模式混响室具有参考借鉴意义。二是完成了混响室空间电场测试系统硬件设计和控制软件开发，构建了振动模式混响室空间电场分布自动测试系统。能够远程操控常用的信号源、功率计、场强计、频谱分析仪和振动控制系统，根据所设参数自动开展测试并存储数据，快速计算振动模式混响室的空间电场特性。可减少测试人员的手动操作，节省测试时间，使得振动模式混响室的性能测量和数据处理实现了自动化。三是建立了振动模式混响室并验证其有效性。试验发现几何尺寸为3m×2m×1.5m的混响室的下限工作频率为350MHz，测试带宽满足预期；当振动深度为混响室棱边尺寸的20%时，最大标准偏差小于2.5dB，所有分量的标准偏差的平均值为1.44dB，场均匀性优于机械搅拌混响室；混响室品质因数在GHz频段能够达到106量级，在开展小型设备试验时不会损失小输入功率大场强的优势。试验证明振动模式混响室可应用于材料在复杂电磁环境下的屏蔽效能测试和防护性能评估，以及易燃易爆品的辐射抗扰度研究。另外，由于振动模式混响室对场地要求不严苛，也可用于大型互联系统辐射发射超标的现场测试；以及野外装备的电磁兼容性现场测试和评估。