高频有损斜开孔腔体屏蔽效能研究

针对带孔屏蔽腔体工作时受复杂电磁干扰问题,基于电磁拓扑理论和BLT 方程,考虑开孔倾斜、偏 心、任意平面波照射、任意观测点位置等情况,提出用于计算斜开孔腔体屏蔽效能的解析模型。同时将腔体材料考 虑为有损导体,对BLT 方程中散射矩阵和传播矩阵进行修改;并利用电压和电场分布关系,考虑腔体内多种传播模 式,将模型的可计算频段拓展为0~3 GHz。最后,设计五组试验,对比CST 仿真值、Robinson 拓展算法计算值与文中 所提模型计算值,验证所提模型的准确性与优化性。为实际工程中孔缝腔体屏蔽问题的预测与计算提供方法。     

多面开孔腔体孔缝耦合效应研究

为研究任意入射角度平面波对多面开孔腔体的孔缝耦合效应,根据矢量分析和矩形波导内场强分布对等效传输线法进行了改进,计算了多面开孔腔体内任意位置的屏蔽效能。将改进等效传输线法计算结果与CST仿真结果、实验测量结果进行比较,验证了改进等效传输线法的正确性,相比数值计算方法,改进等效传输线法所需计算时间和内存更少。采用改进等效传输线法对相同体积不同尺寸的多面开孔腔体的屏蔽效能进行了研究,结果表明:在相同体积下,腔体为正方体时的屏蔽效能和其他尺寸腔体的屏蔽效能基本一致,但是正方形的屏蔽效能极小值点大大减少,从而减少了电子设备受电磁干扰的几率。     

有内置薄板腔体的HEMP屏蔽效能研究

在HEMP(高空核电磁脉冲)平面波照射下,依据传输线理论和波导理论,结合电路原理,分别建立了HEMP在金属腔内传播时的等效电路模型和信号流图,得到了腔体各部分的等效阻抗以及HEMP 在腔体内传播过程中的传输矩阵和散射矩阵。采用了传输线法(TLM)和广义Beam-Liu-Tesche(BLT)方程法两种快速算法计算有内置薄板的开孔矩形金属腔的屏蔽效能,与仿真计算进行了对比,验证了扩展算法的准确性,并分析了内置薄板的宽度和位置对腔体屏蔽效能的影响。结果表明:两种快速算法均能准确地计算腔体的屏蔽效能;内置薄板越宽,且越靠近中央位置,腔体的屏蔽效能越高,谐振频率越大。研究所得结论可以为电子设备的HEMP防护提供重要的理论依据。     

内置介质板开孔腔体电磁屏蔽效能拓扑模型

文中针对现有内置介质板腔体屏蔽效能拓扑模型中介质板等效导纳模型的局限性,考虑介质板高度、厚度与位置对介质板等效导纳模型的影响,建立内置介质板腔体屏蔽效能(BLT)方程拓扑模型。将传输线法、BLT方程拓扑模型与仿真结果进行对比,验证BLT方程拓扑模型的准确性和有效性。以300 mm×300 mm×120 mm开孔腔体为研究对象,分别探究其在3种不同谐振主模式下,介质板高度、厚度和位置对腔体屏蔽效能的影响。结果表明,改变介质板高度,腔体的谐振主模式不变,仅影响腔体屏蔽效能大小;腔体内部安装介质板可增强腔体屏蔽能力,但是介质板厚度过大,在一定范围内会削弱腔体屏蔽能力;距腔体孔阵0 mm～58 mm处安装介质板会削弱腔体屏蔽能力,距腔体孔阵100 mm～150 mm处安装介质板会增强腔体屏蔽能力。该结论可为机箱电磁屏蔽设计提供有效参考。     

带孔缝矩形金属腔体屏蔽效能研究

针对带孔缝矩形金属腔体在电磁辐射下的屏蔽效能问题,利用基于时域有限积分法的电磁仿真软件CST,建立了平面波辐照条件下含孔缝金属腔体的耦合模型,重点研究了电场极化方向,腔体材料,矩形孔缝的长度、宽度和深度,孔缝填充介质介电常数及其厚度等参数对屏蔽效能的影响规律.研究结果表明:典型金属材料对屏蔽效能的影响差别不大,垂直于电场极化方向的孔缝边长更能影响腔体的屏蔽效能,孔缝尺寸会影响矩形金属腔体的谐振点,孔缝深度能够通过衰减入射波在一定程度上影响屏蔽效能,孔缝填充介质会降低屏蔽效能,介质厚度及其介电常数会影响屏蔽效能峰值点.研究结果对金属腔体的电磁兼容设计有一定的指导意义.     

平面波斜入射到有孔腔体的屏蔽效能分析

使用解析方法研究了缝隙偏离中心的有孔屏蔽腔屏蔽效能。将有孔腔体的屏蔽和传输特性用等效传输线的高次模进行分析,推导了平面波以任意角度和极化方向入射时,有孔腔体屏蔽效能的解析计算表达式。分析了入射角度、极化方向、孔缝尺寸、测试点位置、腔体壁损耗、工作频率等参量与腔体屏蔽效能的关系。经与腔体谐振频率比对,表明该解析方法得到的结果可信,而且解析公式计算速度快,利于参量分析,能为屏蔽腔体设计提供依据。     

含短贯通导体金属腔体电磁耦合规律研究*

为研究平面波辐照下含短贯通导体金属腔体电磁耦合规律,利用电磁仿真软件CST 搭建仿真耦合模型,从频域角度进行了仿真研究,并利用矢量网络分析仪、功率放大器、GTEM 室和电场测试探头搭建实验系统进行了验证。通过仿真研究了贯通导体长度、贯通孔尺寸和腔体内屏蔽效能监测点位置等因素对屏蔽效能的影响。结果表明:仿真和实验的结果具有一致性;贯通导体腔体外长度越长,屏蔽效能越低,腔体内长度越长,腔体谐振频点越低;贯通孔尺寸越大,腔体屏蔽效能越低;监测点位置离贯通导体越近,屏蔽效能越低。同时研究了吸波材料和开口金属环对含短贯通导体金属腔体的防护效果。此研究具有实用意义,能够指导电子设备的设计和安装。     

任意方向平面波入射下有孔箱体屏蔽效能的估算*

根据Robinson 等效传输线理论,估算了有孔屏蔽箱体在任意入射方向平面波照射下的屏蔽效能。该 方法将任意入射方向平面波的传播矢量和电场矢量分解,使得复杂模型等效为两个不同极化方向平面波垂直入射 箱体开孔平面的简单模型,从而推导了计算屏蔽效能的一般表达式。数值仿真结果与CST 软件仿真吻合较好,验证 了方法的有效性。分析了平面波入射仰角和方位角对有孔箱体屏蔽效能的影响,数值结果表明:在0°~90°范围内, 箱体屏蔽效能随着平面波入射仰角的减小而增大,随着平面波入射方位角的减小而减小。     

双层加载电路板屏蔽腔屏蔽效能研究

为了提高设备中电子元件抵御来自外界和内部其他元件的电磁干扰,根据传输线理论,将双层加载电路板屏蔽腔体模型转换为电路图,利用电路图推导出腔体中心屏蔽效能的等效公式。利用Matlab生成传输线法屏蔽效能曲线,并通过仿真软件CST建模仿真,仿真结果与Matlab输出曲线良好吻合,验证了公式的正确性。运用CST研究了一些因素如电路板大小、数量、放置方式以及距孔缝的距离对屏蔽效能的影响。为了更加贴合实际,采用加载集成运算放大电路的印制电路板来研究腔体屏蔽效能以及腔体对电路板功能的影响,最后提出了一些提高屏蔽效能的方法。     

基于BLT计算复杂腔体结构屏蔽效能的拓展方法

本文通过拓展BLT(Baum-Liu-Tesche)方法,计算了复杂结构腔体的屏蔽效能（Shielding Effectiveness,SE）. BLT方法最初被用于分析传输线模型,后被拓展到计算腔体屏蔽效能,然而其局限于计算矩形腔体和圆柱腔体的屏蔽效能,无法分析更加复杂的腔体结构.本文将BLT方法与数值方法相结合,同时利用机器学习的回归方法,将其拓展到复杂腔体结构的屏蔽效能计算中.本文首先计算了腔体二维截面的特征模;然后,基于电磁波传播规律建立了等效电路网络结构,结合BLT方法获得腔体屏蔽效能的频域响应分布;最后,利用机器学习方法训练支持向量回归模型（Support Vector Regression,SVR）,修正频域响应幅值,得到腔体目标的屏蔽效能.本文采用了3种不同结构的腔体对提出的方法进行了验证,频率范围为0.1～3 GHz.以商业软件仿真得到的结果为标准,本文提出的方法可以在85%的置信度条件下,实现均方根误差小于3,同时计算速度相比商业软件提升80倍以上.     

Coupling through an Aperture Containing an Anisotropic Ferrite

Coupling through an aperture containing anisotropic ferrites is investigated theoretically by a simple extension of Bethe's hole coupling theory to include the dipole moment of the body in the aperture. The magnetic dipole moment of the ferrite body is ordinarily a vector but becomes a tensor upon the application of a field. This new theory is applicable to any situation where Bethe's small-hole coupling theory is valid. Experimental verification was quite satisfactory and was obtained on two Bethehole couplers: one with the waveguides parallel, and the other with the waveguides perpendicular.     

Integration of an SCR in an active clamp

This paper presents the integration of an SCR into a HV power clamp. For low currents the structure operates in “active clamp” mode and clamps the voltage to a value above the maximum operating voltage. After snapback the structure clamps the voltage to a low value as an SCR.     

位于任意形状导体上的天线输入阻抗分析

分析位于任意形状导体上天线的输入阻抗是一个复杂的电磁边值问题，这类问题一般很难得到解析解。在数值分析中，矩量法是一个非常有用的工具。线栅法曾被用来分析这类三维问题。但对于天线的近场特性，它存在一定的不足和困难。面元剖分可以克服线栅法的缺点。Ｒａｏ采用三角面元剖分方法，分析了位于导体上的天线特性。然而，在Ｒａｏ的数值模型中，他将结点区对边边界上的电流假设为零。为此，我们对Ｒａｏ的这一结点模型进行了修正，修正后的结果表明，理论与实验符合得较好     

Realizing an Epitaxial Decorated Stanene with an Insulating Bandgap

The exploration of intriguing topological quantum physics in stanene has attracted enormous interest but is challenged by lacking desirable material samples. The successful fabrication of monolayer stanene on PbTe(111) films with low‐temperature molecular beam epitaxy and thorough characterizations of its atomic and electronic structures are reported here. In situ angle‐resolved photoemission spectroscopy together with first‐principles calculations identify two hole bands of p _xy orbital with a spin‐orbit coupling induced band splitting and meanwhile reveal an automatic passivation of p _z orbital of stanene. Importantly, material properties are tuned by substrate engineering, realizing a decorated stanene sample with truly insulating bulk on Sr‐doped PbTe. This finding paves a road for studies of stanene‐based topological quantum effects and electronics.     

Diffraction of an electromagnetic wave from an infinitely long slit in an infinite metallic sheet

The diffraction of anE-polarized and anH-polarized wave by an imperfectly conducting slit (on which impedance boundary conditions are imposed) in an infinite metallic plane is investigated. The two independent problems are solved by using integral transforms, the Wiener-Hopf technique and asymptotic approximations. It is found that the diffracted field consists of the sum of fields produced by the two edges of the planes formed by the slit and a field due to the interaction of the two edges.     

Equivalent currents for an aperture in an impedance surface

Expressions of equivalent magnetic and electric currents for an aperture in an impedance surface is derived in a self-consistent manner. Each equivalent current consists of the combination of the tangential electric and magnetic fields in the aperture, and is placed in front of the original aperture where the surface is extended to close the aperture. The result is particularly useful for problems involving apertures in an impedance ground plane     

Radiation from an aperture in an infinite conducting wedge

In this paper the problem of the far field radiation of an infinite aperture occupying one side of an infinite conducting wedge is solved. For uniform illuminations as well as for illuminations tapered to zero at the edges, it is shown that the radiated field can be effectively represented by line sources situated along the edge of the wedge. Also, for the special case of illuminations which taper to zero at the edges within a few wavelengths, it is shown that the shadow region radiation is proportional to the rate of taper.     

Control of an electrical prosthesis with an SSVEP-based BCI

Brain-computer interfaces (BCIs) are systems that establish a direct connection between the human brain and a computer, thus providing an additional communication channel. They are used in a broad field of applications nowadays. One important issue is the control of neuroprosthetic devices for the restoration of the grasp function in spinal-cord-injured people. In this communication, an asynchronous (self-paced) four-class BCI based on steady-state visual evoked potentials (SSVEPs) was used to control a two-axes electrical hand prosthesis. During training, four healthy participants reached an online classification accuracy between 44% and 88%. Controlling the prosthetic hand asynchronously, the participants reached a performance of 75.5 to 217.5 s to copy a series of movements, whereas the fastest possible duration determined by the setup was 64 s. The number of false negative (FN) decisions varied from 0 to 10 (the maximal possible decisions were 34). It can be stated that the SSVEP-based BCI, operating in an asynchronous mode, is feasible for the control of neuroprosthetic devices with the flickering lights mounted on its surface.     

Clinical application of an active electrode using an operationalamplifier

An active electrode (d10 mm, t6 mm) is presented, that functions as an impedance transformer (an input impedance > 10 G omega, an output impedance < 1 omega) by means of which we can derive surface EMG without any skin preparation and paste. This electrode was compared with a conventional one, and it was ascertained that the electrode could be replaced with the conventional one, and, moreover, it was preferable because it required less preparation time, and was less affected by environmental noise.     

电偶极子在无限大各向异性媒质中的辐射场

分析电偶极子在无限大各向异性媒质中的辐射场，得出了近区场地级数表达式。分析计算了电偶极子平行天于地磁场时在无限大均匀各向异性电离层中的远区场。