【作者】 闫哲；

【导师】 杨嘉祥；

【作者基本信息】 哈尔滨理工大学 ， 高电压与绝缘技术， 2008， 博士

【摘要】 一个实际的电子系统都处于金属屏蔽腔体内,并不可避免地开有小孔及导线穿入腔体内,外部电磁波通过小孔及线耦合到腔体内,并在导线上感应出瞬态电流,在端接部分感应出电压。由此形成的干扰对系统具有破坏作用。随着电子系统的功能不断增加,相应的连接导线增多,系统的边界几何结构日趋复杂,整个空间也不是均匀媒质,外部干扰与其形成了复杂的电磁交互环境。以往对此方面的研究往往采用各自独立的孔耦合理论或多导体传输线理论分别来近似处理,显然该方法与实际情况存在较大误差。为解决上述问题,必须将孔耦合及多导体传输线基本理论相结合,形成系统化理论体系来揭示复杂电磁交互的本质规律。电磁拓扑法是按照屏蔽腔体的实际结构、屏蔽级别在三维空间对系统进行划分,用拓扑图来表示它们的相互作用关系,通过BLT (Baum-Liu-Tesche)方程的正交分解算法将整个系统分解成各个独立的子系统,由此来减小系统求解的计算量。本文应用电磁拓扑理论对电磁脉冲通过孔耦合到腔体内并与多导体相交互问题进行了研究,建立了多导体传输线孔耦合电磁拓扑理论模型。根据系统的实际结构建立了拓扑图及相应的电磁交互序列图,利用等效原理将孔等效为磁流源,并利用边界条件、镜像原理推导出孔上的等效偶极矩并作为腔体内的辐射源。对于腔体内的多导体传输线上的分布源可通过该辐射源来计算,通过对BLT方程求解,得到了电场屏蔽效能的频率特性、感应电压及其随孔的尺寸、激励源入射角变化规律等孔耦合重要特性参数的理论值及相应曲线。电磁脉冲模拟器作为孔耦合电磁拓扑模型的外部高能激励源,为实验研究复杂电磁环境中的耦合问题提供了必要的技术支持。该模拟器采用单片机控制,能够产生5个连续双指数脉冲波形,而且能够实现脉冲间隔、电压幅值连续可调等功能。为了计算模拟器工作空间内的电磁场,利用电磁场张量法推导出电磁脉冲模拟器工作空间内电磁场时域解析表达式,解决了激励源分布在含有折角突变结构中电磁波的时域解析法计算问题,为复杂边界环境中的电磁场计算奠定了基础。结果表明电磁场分布是由模拟器的前、后锥板及平行板上的均匀分布电流不同滞后位叠加所产生的,而且具有横电磁波特性。针对金属屏蔽腔体内导线上的感应电压瞬态响应实验数据,采用矩阵束算法和奇点展开法提取了瞬态响应晚期低频特征参数,采用分数付里叶变换技术求取了瞬态响应早期高频特征参数,并确定了耦合函数。电磁拓扑理论模型的计算结果与实验数据基本吻合,表明了所提出的模型可行性及有效性,并为今后进一步全面深入研究和应用电磁拓扑理论提供了基础。更多还原

【Abstract】 A practical electronic system is located within a metal shield cavity with unavoidable perforated apertures and conducting wires pass through the enclosure. Through an aperture and wires external electromagnetic pulse couples to the cavity, in which the transient current is induced on the lines and the transient voltage is induced on the line ends, and the interference formed by the transient current and voltage has destructive effect. With the increasing function of the electronic system and thousands of connecting wires, boundary geometric construction becomes more and more complicated, while the whole space is not a homogeneous medium, and the complicated electromagnetic interaction environment is also formed by the external electromagnetic pulse and the electronic system. The research on the above-mentioned problems used individual theories of the aperture coupling or the multiconductor transmission lines respectively to achieve approximate treatment. Obviously, in the method mentioned above there existed errors in practical situations. To solve the above problems, the aperture coupling theory and multiconductor transmission line theory should be combined to form a theoretics system to reveal essential rules of the complicated electromagnetic interaction.Electromagnetic topology divides the system in 3D space according to the system construction and shielding levels. The interactive relation can be represented as the electromagnetic topological diagram by using the orthogonal decomposition algorithm of the BLT (Baum-Liu-Tesche) equation to divide the whole system into the separate subsystems and therefore to reduce the computation of the systems’solution.Electromagnetic pulse (EMP) coupling through an aperture to multiconductor transmission lines inside cavity is considered by using electromagnetic topological theory in this dissertation. An electromagnetic topology theoretical model of multiconductor transmission-line aperture coupling is proposed. The topological diagram and the corresponding electromagnetic interaction sequence diagram in terms of the practical system are constructed. Using the equivalent theorem, the aperture is replaced by the equivalent magnetic sources. Utilizing boundary conditions and image theorem, the equivalent electric and magnetic dipole moments which can be exciting sources inside cavity are derivated. The calculation of the equivalent distribution sources on multiconductor transmission lines located inside the cavity can be expressed by the exciting sources. The theoretic calculation values and the measured waveforms for the electric field shielding effectiveness in frequency domain are obtained. The induced voltages vary with the aperture sizes and incident angles of the exciting sources, which describe the important characteristic parameters of the aperture coupling, obtained by finding the BLT equation solution.An electromagnetic pulse simulator, acting as the external high power electromagnetic pulse of the aperture coupling electromagnetic topological model, offers necessary technical support for the experimental research on the complicated electromagnetic interaction circumstance. The simulator controlled by the single chip microcomputer can generate five continuous double exponential pulse wavefroms, and pulse interval, voltage magnitude are adjustable. In order to compute the electromagnetic field of the simulator work volume, the electromagnetic field analytic expression of the simulator work volume is derived from the electromagnetic field tensor, and the computation problem of the electromagnetic wave analytic method is solved in the time domain for the exciting sources distributed in the abrupt bent construction. The computation result indicates that electromagnetic field distribution results from different retard potentials superimposed by the uniform currents from the front and back conical plates as well as middle parallel plate, and the field distribution has the feature of transverse electromagnetic wave.To the transient response experimental data of induced voltage on the lines located a metal shield cavity, the characteristic parameters are extracted for the transient later time response in low frequency by using the singularity expansion method (SEM) and the matrix pencil algorithm, and the characteristic parameters of the early time response in high frequency are also extracted by using the fractional Fourier transform technique, and coupling functions are obtained as well.The computation results are in good agreement with the electromagnetic topology theoretical model, indicate the feasibility and validity of the proposed model, and provide the foundation for further extensive research on and application to the electromagnetic topological theory.更多还原