小型化宽带磁场探头仿真与设计

提出了一种近场磁场探头,可用于集成电路电磁辐射发射测量,对电子设备中的辐射源定位。探头采用四层印刷电路板设计,介质材料采用高性能、低损耗的Rogers 4350B 材料,确保结构简单和小型化。多层板结构可以有效屏蔽外部空间中的电场耦合。通过使用过孔栅栏和同轴过孔结构实现良好的阻抗匹配,并且提高工作频率。同时,屏蔽过孔能够形成屏蔽腔,有效抑制谐振,提高电场抑制性能。采用HFSS 仿真软件得到磁场探头的性能参数,并进行实物加工。实验结果表明,探头工作频带可达到12 GHz,空间分辨率为2 mm,有良好的电场抑制度,仿真与实测结果吻合良好。     

Cavity Model for the Slot Radiation of an Enclosure Excited by Printed Circuit Board Traces With Different Loads

Traces on a printed circuit board (PCB) couple to the cavity consisting of the PCB ground plane and a metallic enclosure cover. We introduce this common-mode coupling of a PCB trace to the cavity field by an analytical model that is verified with 3-D simulations using HFSS. The cavity field causes radiated emission from the slots of the cavity. For an accurate calculation of the cavity field inside the enclosure and the radiated emission, we consider the radiation loss by a multiport approach. Comparisons of the analytical results for the radiated field to measurements show good agreement. Radiated emission can be calculated for arbitrary geometric enclosure shapes as a function of frequency, position of the trace on the PCB, and trace load/driver impedances.      

A theoretical investigation of the resonance damping performance of magnetic material coating in power/ground plane structures

Power bus structure, consisting of two parallel solid power and ground planes separated by an insulator, behaves as a cavity resonator at high frequencies. Noise on the power bus, due to a sudden change in the current drawn by an active component, can appear as an undesired spatial fluctuation in the voltage between power and ground, especially at resonant frequencies of the resultant cavity, which may lead to problems in signal integrity, excessive delays, false switching, and radiated emission. These resonances can be suppressed by introducing high-frequency loss into the structure. This paper investigates a simple method to reduce self-/transfer impedance of power/ground planes for mitigating power/ground bounce in high-speed printed circuit board design by adding a thin layer of magnetic material coating to the inside-facing surfaces of copper power and ground plates to increase their effective high-frequency surface impedance. The increased surface impedance will increase the attenuation constant of the propagating wave inside the cavity that benefits reduction of cavity's quality factor (Q factor). The simulation results obtained from a modified cavity resonator model show that increasing surface impedance can dramatically reduce self- and transfer impedances at board resonant frequencies.     

The radiation of a rectangular power-bus structure at multiple cavity-mode resonances

The radiation from power-bus structures on high-speed printed circuit boards due to the switching noise current of digital integrated circuits is investigated. The study is based on an analytical cavity-resonator model for a rectangular parallel-plate structure. Based on the application of the field-equivalence principle, the radiated field is calculated from the electric edge-field distribution. For typical board dimensions, several cavity-mode resonances occur within the typical frequency range of interest, leading to relatively high maximum values for radiated emission. The evaluation of the radiation patterns reveals that all (0, nth) resonances have equal maximum amplitudes in the whole mode spectrum. This allows the setting up of an engineering equation for quantifying the noise-current-related maximum radiated field strength, including the dielectric and ohmic loss. Among all geometrical and material parameters, the dielectric thickness is one of the most effective ones to control radiated emission. The theoretical results are well confirmed by accurate measurements carried out in an anechoic room.     

减弱高速PCB过孔影响的方法

介绍了过孔的分类与应用,并针对盲孔的阻抗突变作用、通孔的EMI辐射问题,通过仿真方法分析得出:实际电路避开盲孔谐振点即可减弱阻抗突变作用;增加接地过孔,可改变电流的回流路径,减小电路的环路面积即可减弱EMI,并验证了此方法的优越性.     

高速嵌入式系统中电源噪声抑制方法

根据平面腔体谐振模型理论推导出高速嵌入式电路电源平面对阻抗函数关系式,分 析了电源平面对的谐振特性与PCB板材、介质层厚度以及导体平面的电导率之间的关系,得 出可通过减小介质层厚度、使用高介电常数的介质材料以及增加介质损耗等3种方法来抑制 电源平面对的谐振效应,并使用全波仿真方法验证了可行性。从时域仿真了高速电路中的噪 声传播与电源平面谐振的相互关系,结果表明,通过抑制电源平面对谐振阻抗可将电源噪声 减 小至原有结构的15%,从而有效提高系统的电源完整性。     

高速多层PCB板中过孔的建模、仿真及分析

利用Hyperlynx软件对高速PCB板中所应用到的过孔进行建模与仿真,分析了过孔对流经其上信号的影响,并给出了改进、优化过孔的方法。仿真结果表明,在要求线上信号完整性高的情况下,使用过孔方式连接的电路得到了改善和优化。     

开缝腔体场强增强效应抑制方法研究

开缝屏蔽腔体不能完全阻断能量耦合,导致在腔内局部区域、特定频点附近形成场强增强效应,对敏感器件或线路构成威胁。以分析腔内场强增强效应及研究抑制方法为出发点,建立3 种开缝腔体数值模型,提出并验证腔体涂覆吸波材料、内置吸波柱、内置双层PCB 板等谐振抑制方法的有效性。结果表明:在3 种腔体模型内表面涂覆吸波材料均能有效抑制场强增强效应,并且涂覆磁损耗型吸波材料效果最好;随着涂覆厚度的增加,谐振抑制效果也增强;腔体中心放置吸波柱,应使用电损耗型吸波材料。腔体内置PCB 板既能实现对电子器件和线路的承载功能,还可整体大幅度提升腔体屏蔽效能,对谐振效应的抑制体现在迫使腔体主谐振点偏移,结合使用吸波材料,高阶第2 谐振点处谐振抑制效果也明显改善。     

Modeling and Measurement of Interlevel Electromagnetic Coupling and Fringing Effect in a Hierarchical Power Distribution Network Using Segmentation Method With Resonant Cavity Model

A hierarchical power distribution network (PDN) consists of chip, package, and printed circuit board (PCB) level PDNs, as well as various structures such as via, ball, and wire bond interconnections, which connect the different level PDNs. When estimating the simultaneous switching noise (SSN) generation and evaluating PDN designs, PDN impedance calculation is an efficient criterion. In this paper, we introduce two new kinds of modeling approaches that are exceptionally suited to improving the accuracy of the PDN impedance estimation, especially for hierarchical PDN. First, we propose a modeling procedure to add an interlevel electromagnetic coupling effect between PDNs of different levels, based on the resonant cavity model and segmentation method. In order to effectively consider the interlevel electromagnetic coupling effect, we introduce a new concept of interlevel PDN, which is, for example, composed of a metal plate in the package-level PDN and a metal plate in the PCB-level PDN. Next, we present a modeling procedure to include the fringing field effect at the edge of small-size PDN structure, which causes a considerable shift of cavity resonance frequencies in the PDN impedance profile. In order to verify the proposed modeling approaches, we have fabricated a series of test vehicles by combining two package-level PDN designs with a PCB-level PDN design. Finally, we have successfully validated the proposed modeling approaches with a series of frequency-domain measurements in a frequency range up to 5 GHz.      

Polarization effects caused by diffraction of the radiated of an arbitrarily oriented electric dipole at the edge of a perfectly conducting half plane

Diffraction of the field radiated by an electric dipole at the edge of a perfectly conducting half plane is considered. The uniform representation of the field in the far zone is applied to analyze the polarization of the field depending on the orientation and position of the dipole relative to the edge. The analysis is performed in the entire observation space. It is shown that the linearly polarized radiation of the dipole with the axis perpendicular to the edge of the half plane is transformed into the elliptically polarized radiation.     

Coupling of vias in electronic packaging and printed circuit board structures with finite ground plane

A full wave method is presented for modeling and analyzing multiple interactions among vertical vias in densely packaged integrated circuits and printed circuit board with ground plane of finite extent. In such structures, the TEM mode in the planar structure is excited and can propagate and cause interaction of waves among vias. Reflections will also occur at the edges of the finite ground plane. The electromagnetic analysis methodology is an extension of the previous methodology in analyzing multiple scattering among vias for infinite ground plane . The analysis is based upon the cylindrical wave mode expansion of the magnetic field Green's function, the Foldy-Lax multiple scattering formalism and utilizing the resonator modes of a circular cavity. The circular resonator modes are transformed into cylindrical waves onto the cylindrical via structures. Numerical results illustrate the physics of the underlying resonance scattering problems. We consider the cases of a) two coupled active vias of differential mode and b) two coupled vias of common mode. Results are also illustrated for ground plane resonance and the effects of shorting vias on such resonance. The effects of off-centering and the presence of idle vias are also illustrated.     

使用发射信道模型降低液晶显示屏电磁干扰

本文介绍一种发射通道模型来仿真液晶显示屏所产生的电磁干扰噪声。通道模型包含基于IEC61967-2标准(横电磁波传输室的辐射发射)的封装、印刷电路板以及辐射柔性印刷电路板等模型来仿真电磁发射能量。最后,本文所用的仿真平台已经验证带有不同时序控制驱动器的真实37"液晶显示屏,而实验结果显示降低电磁干扰的效果极佳。配合所提出的发射通道模型,我们能够很容易的设计低发射驱动器,避免因电磁干扰问题所导致的成本增加。     

Radiation from a slot in an impedance surface

The effects of a lossy-ground plane on the radiation from a slot are analyzed by using a Green's function of an impedance surface. Numerical results of the radiation field, radiated power, and loss power are presented for various lossy ground planes. In particular, the radiation field and the radiated power from a short slot are given by simple closed expressions. The analytical model of a slot in an impedance surface is validated by radiation field measurements     

一种二叉树状分形偶极子天线的设计

提出了一种基于二叉树状分形结构的分形偶极子贴片天线。该天线的介质基片采用相对介电常数为4.4,介电损耗角正切为0.02的FR4介质板,由微带线经阻抗变换后进行馈电。该天线利用分形技术实现了33%的尺寸缩减;通过平行双线结构和开U型槽技术,优化了阻抗匹配,降低了天线的谐振频率。通过仿真分析与模型优化,天线的最终尺寸为35 mm×22 mm×1.6 mm,中心工作频率为2.87 GHz,工作频率为2.77~2.97 GHz,-10 dB阻抗相对带宽为6.9%,工作频带内最小回波损耗可达-49 dB,最大增益可达2.36 dB。该天线具有小型化、阻抗匹配良好的优点,在当代小型化通信系统中具有良好的应用前景。     

Squeezing Via Spontaneous Rotational Symmetry Breaking in a Four-Wave Mixing Cavity

We predict the generation of noncritically squeezed light through the spontaneous rotational symmetry breaking occurring in a Kerr cavity. The model considers a $chi^{(3)}$ cavity that is pumped by two Gaussian beams of frequencies $omega_{1}$ and $omega_{2}$. The cavity configuration is such that two signal modes of equal frequency $omega_{s}=(omega_{1}+omega_{2})/2$ are generated, these signal fields being first-order Laguerre–Gauss modes. In this system, a spontaneous breaking of the rotational symmetry occurs as the signal field corresponds to a Hermite–Gauss TEM mode. This symmetry breaking leads to the perfect and noncritical (i.e., nondependent on the parameter values) squeezing of the angular momentum of the output TEM mode, which is another TEM mode spatially orthogonal to that in which bright emission occurs.      

GB/T 22630—2008新增要求和验证

介绍了车载音视频设备电磁兼容标准中增加的有用信号、受试设备工作状态、抗扰度测试的功能状态分类要求及其特殊规定,并对标准中的瞬态电压发射、天线端骚扰电压、辐射骚扰场强、输入抗扰度、天线端射频电压（共模）的抗扰度、典型波形传导抗扰度、辐射抗扰度、静电放电抗扰度进行了测试和验证。     

Effects on signal integrity and radiated emission by split reference plane on high-speed multilayer printed circuit boards

Power/ground partitioning has been used to supply multivoltage levels and to isolate power/ground noise in high-speed multilayer printed circuit boards. However, the partitioning of the power/ground plane breaks the current return path of the signal current through either the power plane or the ground plane, which causes undesired effects such as signal distortion, crosstalk, and radiation. To control and suppress these undesired effects, we should understand the electromagnetic mechanism associated with them. In this paper, the mechanism of the reflection and the transmission of the signal by the slotted power/ground plane is well understood through an analysis of measurements based on time-domain reflectometry. Considering the propagation of a slot wave through the slot line on the power/ground plane, we have successfully explained the changes of the transmitted and reflected waveforms. Furthermore, we have numerically and experimentally investigated the effects of the power/ground partitioning on the radiated emission in various structures. Finally, it is confirmed that the employment of a stitching capacitor on the power/ground slot suppresses the signal distortion and the radiated emission significantly. When the size and the location of the stitching capacitor are designed, there should be a compromise between the noise isolation and the guarantee of the return current path, with considering the resonance frequencies of planes by the capacitor.     

Self-induced heterodyne: The interaction of a frequency-swept pulse with a resonant system

The behavior of a pulse whose frequency sweeps through the resonance of a linear system, although first studied in spin resonance, is widely applicable to many wave phenomena. A frequency-swept optical pulse transmitted through a resonant medium develops intensity oscillations, which are the result of heterodyning the input pulse with the field radiated by the resonant system. This self-induced heterodyne signal allows the determination of the relative phase between the input pulse and the single frequency field radiated by the resonant system. A simple approximate model which very accurately describes the time evolution of the output pulse is given a physical and mathematical basis. Results for the optically thin case are extended to include the effects of propagation, revealing phenomena which have no spin-resonance analogy.     

新型亚波长光栅横向腔面发射激光器

本文报道一种新型的横向腔面发射激光器,基于亚波长光栅平面内的横向谐振与垂直发射。器件采用不含DBR结构的商用波导外延材料,不需要晶片键合技术。在1552.44 nm处获得了23.0 dB的边模抑制比,最高输出功率5.32 mW。此单模激射与带边模式计算相吻合。在3维的模拟中,我们观察到光栅表面的光输出。     

使用双绞差分结构减小印刷电路板上的串扰和辐射发射

随着发展的需要,高速数字电路PCB板上信号速度越来越快,由于差分信号有较强的抗干扰能力,因此用的得越来越普遍。但是,随着上升时间的进一步减小,差分信号的信号完整性问题也变得越来越重要。由于双绞的结构在一定程度上使得干扰相互抵消,从而提高系统对串扰和辐射发射的抵抗能力,因此,近两年来有一种新的双绞差分传输线被引入到布线中。本文从理论上分析了双绞差分线结构减小串扰和辐射发射的机理,并且通过建模仿真验证了其正确性．