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Electromagnetic characterisation of printed circuit boards

印刷电路板的电磁特性

基本信息

批准号：
EP/D048540/1
负责人：
David Thomas
金额：
$ 33.56万
依托单位：
University of Nottingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FD048540%2F1
关键词：
Electromagnetic characterisation printed circuit boards

项目摘要

Significant advances have been made in developing circuits driven by fast clocks, thus increasing dramatically processing speeds. Clock rates of a few GHz are now available. Even a few harmonics of the clock rate, takes designs well into the microwave region where printed circuit boards (PCBs) have dimensions of the order of several wavelengths and become efficient radiators of electromagnetic (EM) energy. The increase in clock speed in combination with the driving down of device switching voltage levels is making emissions and susceptibility critical issues in the next generation systems. It is becoming critically important to include electromagnetic compatibility (EMC) very early in the design phase of high speed systems. Design engineers are primarily concerned with circuit based currents and voltages and are normally only marginally aware of the EMC issues. EMC is primarily concerned with the emission of EM fields from devices and the susceptibility of a device to an external EM field. EM field driven issues make circuit geometry as well as network connectivity important for PCBs which are electrically large (compared to wavelength). PCBs are also becoming more complex so that quantifying their EM properties is more difficult. It is of course possible, through detailed 3D EM simulation, to accurately reproduce the EM fields around a PCB but this requires unrealistic computing power and simulation run times. Full field-based tools, although well developed for microwave circuits, cannot deal efficiently with the complexity of modern designs. EMC issues are frequently concerned with harmonic frequencies outside the operating frequency and beyond the range for which device characteristics are accurately quantified. The provision of efficient EMC CAD analysis tools and concepts would be a timely addition to advanced engineering design.The object of this project is to simplify the problem of EM emissions from PCBs as much as possible and to provide design engineers with a simple coherent measure of the performance of a PCB, which can be plugged and played in an EMC analysis package. By this we mean a formulation of simple and general emission equivalents, which can easily be incorporated into full-field EM models for the purpose of assessing EMC interaction of several PCBs in their operating environment. The method proposed is to echo the established IBIS approach for the port characterization of devices which engineers are familiar with. It is proposed to develop and evaluate a technique where the EM emissions and coupling of a PCB are characterized by an array of electric and magnetic dipoles. The way the PCB is segmented and represented by equivalent dipoles will be the subject of extensive investigations as it must offer an acceptable way of replicating emissions. These dipole structures may be active to represent on board sources or passive to represent the coupling between the PCB and the EM environment. Though PCB structures may be complex, resolution of the order of approximately a tenth of a wavelength is normally necessary to accurately represent a device's EM characteristics. An array of equivalent dipoles spaced a few cm apart with their source amplitudes and impedances should, therefore, be sufficient to accurately represent a PCB. Ideally this representation must be invariant under all changes in system conditions in the enclosure or the external environment. In this way the development engineer will have a simple and efficient model, which can be plugged into standard EM field solvers to rapidly prototype a system design for EMC. Also, realistic problems can be tackled at a reasonable computational cost. The proposed EM representation of a PCB will be very powerful as it would be completely general being valid not only for full EM field solvers but also for other semi-analytic intermediate EMC models. Such models allow what if studies to be conducted during the conceptual design phase.

在开发由快速时钟驱动的电路方面已经取得了重大进展，从而显著提高了处理速度。现在可以获得几GHz的时钟速率。即使是时钟频率的几个谐波，也可以很好地将设计带入微波区域，其中印刷电路板（PCB）具有几个波长量级的尺寸，并且成为电磁（EM）能量的有效辐射器。时钟速度的提高与器件开关电压电平的降低相结合，使得下一代系统中的发射和敏感性成为关键问题。在高速系统的设计阶段尽早考虑电磁兼容性（EMC）变得至关重要。设计工程师主要关注基于电路的电流和电压，通常只对EMC问题有一定的了解。EMC主要涉及设备的电磁场发射以及设备对外部电磁场的敏感性。EM场驱动的问题使得电路几何形状以及网络连接对于电学上较大的PCB（与波长相比）很重要。PCB也变得越来越复杂，因此量化其EM特性变得更加困难。当然，通过详细的3D EM仿真，可以准确地再现PCB周围的EM场，但这需要不切实际的计算能力和仿真运行时间。完全基于场的工具，虽然很好地开发了微波电路，不能有效地处理现代设计的复杂性。电磁兼容性问题通常与工作频率之外以及设备特性被准确量化的范围之外的谐波频率有关。提供有效的EMC CAD分析工具和概念将是对先进工程设计的及时补充。该项目的目标是尽可能简化PCB的EM发射问题，并为设计工程师提供一个简单的PCB性能的一致性测量，该测量可以在EMC分析包中即插即用。通过这一点，我们的意思是一个简单的和一般的排放当量，它可以很容易地被纳入全领域的EM模型，以评估EMC的相互作用的几个PCB在其操作环境的目的制定。所提出的方法是呼应既定的IBIS方法的端口特性的设备，工程师们都很熟悉。建议开发和评估一种技术，其中PCB的EM发射和耦合的特征在于由电偶极子和磁偶极子的阵列。PCB的分割方式和等效偶极子的代表方式将是广泛调查的主题，因为它必须提供一种可接受的复制排放方式。这些偶极结构可以是有源的以表示板上源，或者是无源的以表示PCB与EM环境之间的耦合。虽然PCB结构可能很复杂，但通常需要大约十分之一波长的分辨率才能准确表示器件的EM特性。因此，一个等效偶极子阵列（间距为几厘米）及其源振幅和阻抗应足以准确表示PCB。理想情况下，该表示必须在外壳或外部环境中的系统条件的所有变化下保持不变。通过这种方式，开发工程师将拥有一个简单而有效的模型，该模型可以插入标准EM场求解器，以快速原型化EMC系统设计。此外，现实的问题可以在一个合理的计算成本解决。所提出的PCB的EM表示将是非常强大的，因为它将是完全通用的，不仅适用于完整的EM场求解器，而且适用于其他半解析的中间EMC模型。这些模型允许在概念设计阶段进行假设研究。