【作者】 郝翠；

【导师】 李邓化；

【作者基本信息】 北京交通大学 ， 电路与系统， 2014， 博士

【摘要】 摘要：为了抵抗电磁干扰对电子设备的影响,电磁屏蔽正不断发展起来,并广泛应用于各个领域。虽然现在有很多数值方法可以得到较为精确的电磁仿真数据,但其耗费时间长,CPU的计算量大。因此,应用解析法建立完善的电磁屏蔽模型正逐渐成为指导工程实践的快捷有效的方法。本文以光纤陀螺寻北仪为研究对象,应用解析法中的传输线理论,对实际工程中出现的典型屏蔽腔体分别进行了较为完整的建模。其中包括单层带孔缝腔体、双层带孔缝腔体、双面带孔缝腔体以及内置PCB板的腔体,并求解出了其中任意点的屏蔽效能,为工程实践中屏蔽腔体和孔缝的设计,及其内部器件的安排布局提供了很好的参考价值。论文的主要工作和创新如下：1.针对平面电磁波以任意角度射入腔体的实际情况,提出在建模中引入平面电磁波的竖直入射角、水平入射角与极化角的方法。把平面电磁波的坐标从入射源坐标系转换到矩形腔坐标系,并按照电磁波的水平极化分量和垂直极化分量分别对模型进行分析研究。此建模方法使得平面电磁波可以以任意角度射入腔体,增强了模型对实际情况的拟合性。2.针对孔缝处于腔体面的任意位置的实际情况,提出把孔缝建模成宽度不对称的共面带状线的方法。应用在平面电磁波辐射下的分布电源传输线模型对孔缝进行建模,并求出在孔缝中心处产生的等效电压,以此电压做为后续电路的电压源。此建模方法节省了计算时间,把孔缝从腔体面的中心位置扩展到了任意位置,扩大了模型对工程实践的适用性。3.针对探测点处于矩形腔内任意位置的实际情况,提出结合模式电压和模式电流来表示矩形谐振腔内电磁场分布的方法。把矩形腔体看成一端完全开放,另一端完全封闭的矩形波导。此波导与孔缝相结合,应用集总电源传输线模型进行分析,考虑TE模和TM模的高次模影响,并结合腔体内的电场分布,求解出腔体内任意点的屏蔽效能。此建模方法把探测点从腔体内孔缝中心线上的点扩展到了腔体内的任意点,增强了模型的工程实践价值。4.针对光纤陀螺寻北仪,依照以上建模方法,分别建模求取了单层、双层和三层带孔缝腔体的屏蔽效能。并研究了带孔缝腔体内屏蔽效能与探测点位置之间的关系以及腔体层数与屏蔽效能之间的关系。仿真结果表明：此模型得出的屏蔽效能值与实验测得的数据相吻合,证明了此模型的正确性。腔体的屏蔽效能随探测点的位置不同而不同,且均随腔体层数的增加而有所提高。为工程实践中对屏蔽效能要求比较高的设备或系统提供了很好的参考价值。5.针对光纤陀螺寻北仪,研究了在平面电磁波照射下的双侧面带孔缝的矩形腔以及内置PCB板的带孔缝矩形腔体的建模,并求出了腔体内任意点的屏蔽效能。仿真结果表明：腔体的屏蔽效能随探测点的位置不同而不同,此建模方法具有一定的工程实践价值。更多还原

【Abstract】 In order to resist electromagnetic interference, electromagnetic shielding becomes more and more popular in every field. Though there are many numerical methods which can obtain accurate simulation data, they cost too much long time and tremendous computing workload. It is an enormous waste of resources. So, the analytical method becomes the more effective method in the modeling of the electromagnetic shielding.The FOG North Seeker is taken as an object, and the application of transmission line theory is used in the modeling of typical shielding cavities in the real project, which include single-layer, double-layer, three-layer rectangular cavity with apertures, cavity with apertures in different sides, and cavity with PCB inside. The shielding effectiveness of any point in these cavities are researched respectively, which supplies good reference value for the cavity and aperture designing and devices layout in the real project. The main works and innovations are listed as follows:1. For the actual situation of the electromagnetic wave incidents into the cavity at an arbitrary angle, the method of introducing vertical incident angle, horizontal incident angle, and polarization angle is proposed. The coordinate of the plane electromagnetic wave is converted from the incident source coordinate system to the rectangular cavity coordinate system, and the model is analyzed based on the horizontally polarized component and the vertically polarized component especially. The electromagnetic wave can incident into the cavity at an arbitrary angle with this modeling method, which increases the fitness of the model and the practical situation.2. For the actual situation of the aperture locates at any position of the cavity face, the method of the aperture is taken as the asymmetrical coplanar stripline is proposed. The aperture is modelled according to the transmission line model with distributed voltage sources, and the equivalent voltage produced at the center of the aperture is taken as the voltage source of the whole circuit model. This modeling method saves calculation time. The location of the aperture is extended to any location on the cavity’s face from the center, which increases the applicability of the model.3. For the actual situation of the probe point locates at any position in the cavity, the method of describing the electromagnetic distribution with mode voltage and mode current is proposed. The rectangular cavity is taken as a rectangular waveguide with one end completely open and another end completely closed. The waveguide is combined with aperture, and the total power supply transmission line model is used in the analysis. Considering the higher-order modes of TE mode and TM mode, and combining the distribution of electric field in the cavity, the shielding effectiveness of any point in the cavity is solved. This modeling method extends the location of the probe point to any point in the cavity from the points on the center line of the aperture, which increases the engineering value of the model.4. Aiming at the FOG North Seeker, and according to the above methods, the shielding effectiveness of monolayer cavity, double layer cavity and three layers with apertures are modelled. The relationship between the shielding effectiveness and the location of the probe point and the relationship between the number of the layers and the shielding effectiveness are analyzed. The simulation results show that:the shielding effectiveness solved through the models agrees with the experimental data, which proves the accuracy of the models. The shielding effectiveness is different with the different probe point, and the shielding effectiveness is improved with the increase of the layers. That provides a good reference value for the devices or systems with high shielding effectiveness requirements in engineering practice.5. Aiming at the FOG North Seeker, the rectangular cavity with apertures in different directions and the rectangular cavity with printed circuit board (PCB) inside are modelled to solve the shielding effectiveness of the cavity. The simulation results show that:the shielding effectiveness is different with the different probe point, which gives good advice to the engineering practice.更多还原