Investigation of Fundamental EMI Source Mechanisms Driving Common-Mode Radiation from Printed Circuit Boards with Attached Cables

Fundamental EMI source mechanisms leading to common-mode radiation from printed circuit boards with attached cables are presented in this paper. Two primary EMI source mechanisms have been identified: one associated with a differential-mode voltage and another associated with a differential-mode current, both of which result in a common-mode current on an attached cable. These mechanisms can be used to relate printed circuit layout geometries to EMI sources. The two mechanisms are demonstrated through numerical and experimental results, and an example from a production printed-circuit design is presented

Maximum crosstalk estimation and modeling of electromagnetic radiation from PCB/high-density connector interfaces

This dissertation explores two topics pertinent to electromagnetic compatibility research: maximum crosstalk estimation in weakly coupled transmission lines and modeling of electromagnetic radiation resulting from printed circuit board/high-density connector interfaces. Despite an ample supply of literature devoted to the study of crosstalk, little research has been performed to formulate maximum crosstalk estimates when signal lines are electrically long. Paper one illustrates a new maximum crosstalk estimate that is based on a mathematically rigorous, integral formulation, where the transmission lines can be lossy and in an inhomogeneous media. Paper two provides a thorough comparison and analysis of the newly derived maximum crosstalk estimates with an estimate derived by another author. In paper two the newly derived estimates in paper one are shown to be more robust because they can estimate the maximum crosstalk with fewer and less restrictive assumptions. One current industry challenge is the lack of robust printed circuit board connector models and methods to quantify radiation from these connectors. To address this challenge, a method is presented in paper three to quantify electromagnetic radiation using network parameters and power conservation, assuming the only losses at a printed circuit board/connector interface are due to radiation. Some of the radiating structures are identified and the radiation physics explored for the studied connector in paper three. Paper four expands upon the radiation modeling concepts in paper three by extending radiation characterization when material losses and multiple signals may be present at the printed circuit board/connector interface. The resulting radiated power characterization method enables robust deterministic and statistical analyses of the radiated power from printed circuit board connectors. Paper five shows the development of a statistical radiated power estimate based on the radiation characterization method presented in paper four. Maximum radiated power estimates are shown using the Markov and Chebyshev inequalities to predict a radiated power limit. A few maximum radiated power limits are proposed that depend on the amount of known information about the radiation characteristics of a printed circuit board connector --Abstract, page iv

Development of Reduced Complexity Models for Electromagnetic Modeling

The current and field distributions of various structures can be calculated using full-wave numerical modeling codes. However, this approach is limited by the complex models and extensive computational resources required to analyze the details of each structure. In addition, brute-force modeling of the entire geometry provides relatively little physical insight into the electromagnetic interference (EMI) source mechanisms. Alternatively an effective equivalent model can be obtained by eliminating sources and structures that do not contribute significantly to the radiated emissions and focusing on the features that could possibly be significant sources of EMI. Equivalent models are generally much simpler than model-everything full-wave models and provide physical insight into the features that have the greatest impact on radiated emissions. This dissertation includes four chapters on development of reduced complexity models for the modeling of antennas and printed circuit board (PCB) structures. In the first chapter, a simplified model for normal mode helical antennas is proposed. In this model, the highly curved structure of the helix is replaced with straight wires and lumped elements. The simplified model can be used to reduce the complexity of full-wave models that include a helical antenna. It also can be used to estimate the performance of a helical antenna without full-wave modeling of the helical structure. The second chapter describes a model for determining the common-mode currents on cables attached to a PCB that is based on the concept of imbalance difference. The imbalance difference model is derived from research that shows that changes in geometrical imbalance cause differential- to common-mode conversion. The imbalance difference model can be used to estimate the radiated emissions from trace-board structures due to common-mode currents induced on attached cables. The third chapter introduces a new closed-form expression for estimating the maximum radiated emissions from the board-source-cable structure. This expression is based on two improvements to a closed-form expression in a 2008 paper published in the IEEE Transactions on EMC. The accuracy of the estimate for larger frequency ranges is improved by using an expression for the envelope of F(è, k, lant) that equals the maximum value at every resonant frequency. A modified expression for calculating the effective length of the board improves the accuracy of the estimate when applied to nearly square boards. In the forth chapter, a modeling technique is proposed to speed up the analysis of PCBs with coupled microstrip lines that induce common-mode currents on attached cables. Based on the concept of imbalance difference, differential-mode sources are converted to equivalent common-mode sources that drive the attached cable and the PCB reference plane. A closed-form expression is also developed based on the imbalance difference model to estimate the maximum radiated emissions from the PCB

Analysis of Radiated Emissions from a Printed Circuit Board Using Expert System Algorithms

Three algorithms developed for expert system electromagnetic compatibility tools are used to evaluate a printed circuit board design. The maximum radiated emissions estimated by the algorithms are compared to the measured data for various board configurations. The algorithms identify the most important electromagnetic interference source mechanisms, drawing attention to the design parameters that have the most significant effect on the radiated emissions

Electromagnetic Compatibility Research in Wire Harnesses and CAN Transceivers

This dissertation develops methods how to design wire harnesses reducing common mode components and to analyze the conversion from differential mode to common mode. The three chapters presented are design methods how to figure out the impact of the common-mode components, not only describe the test results but provide important insight as to how the design related to radiated emissions. In the first chapter of this dissertation, the method designing wire harnesses has been presented to match the electrical balance of the circuit board (PCB). This is accomplished via calculating the current division factor (CDF) of the wire harnesses and the PCB, which provides us with the electrical balance of a transmission line. To reduce the amount of common-mode currents induced on the harness, matching the imbalance of the wire harness to the imbalance of its source and termination is essential. The second chapter explores Controller Area Network (CAN) characteristics. Unintentional common-mode components of the CAN transceivers are analyzed and evaluated to determine how much common-mode voltage they produce in various circumstances. The final chapter provide valuable understanding such that ground proximity impacts on the common-mode currents of wire harnesses. The electrical balance change of the wire harness depending on the distance from ground structures is highlighted. It is also analyzed that losing the ground wire impacts on the common-mode excitation

A Method for Charactering EMI Coupling Paths and Source Properties in Complex Systems

A method for charactering EMI coupling paths in complex systems is presented. While it is relatively easy to determine the EMI antenna structures or the sources of EMI, it is often quite difficult to identify, and even more difficult to quantify coupling paths. This paper introduces a measurement-based method to quantify EMI coupling paths, and the source strengths can be indirectly determined by applying linear system theory. Circuit design guidelines, e.g., the permissible even-mode current in a differential signal, can be derived with the knowledge of the coupling path and EMI limits. Moreover, the EMI can be better predicted with the knowledge of the coupling paths, and the EMI source properties simulated with IBIS or SPICE circuit level simulations

Considerations for Magnetic-Field Coupling Resulting in Radiated EMI

Parasitic inductance in printed circuit board geometries can worsen the EMI performance and signal integrity of high-speed digital designs. Partial-inductance theory is a powerful tool for analyzing inductance issues in signal integrity. However, partial inductances may not adequately model magnetic flux coupling to EMI antennas because the EMI antennas are typically open loops. Therefore, partial inductances may not always accurately predict radiated EMI from noise sources, unless used in a full-wave analysis such as PEEC. Partial inductances can be used, however, to estimate branch inductances, which can be used to predict EMI. This paper presents a method for decomposing loop or self inductances into branch inductances. Experimental as well as analytical investigations are used to compare branch- and partial-inductances

EMI analysis of DVI link connectors

EMI problems are not uncommon in high speed communication systems. As the system clock frequencies increases, so does the challenges in controlling the EMI in such systems. A connector is a very important part of a high speed communication system. Electromagnetic interference (EMI) is found to be tightly correlated to mode conversion: from differential-mode (DM) signals to common-mode (CM) currents and further to antenna-mode (AM) currents on the outside of cables or enclosures. Moreover, in such high speed systems, coupling to an adjacent cable-connector system is not uncommon. It is essential to understand and quantify this coupling path in order to mitigate the coupling. Though simulation based methods are widely used, such an approach is generally very time consuming and computationally resource hungry and an effort is made to quantify the coupling paths using measurement-simulation combinations with minimal simulation aid. This thesis presents a systematic approach to isolate and identify the different coupling paths in a high speed interface (in this case we show DVI), as well as identify which discontinuity (and hence the coupling path) is most critical to mitigate EMI. A transfer function based method is implemented to quantify the coupling in the connector cable system. The method developed in this study can be used for any high-speed interface in modern communication systems. --Abstract, page iii

An Expert System for Predicting Radiated EMI from PCB\u27s

This paper describes an expert systems approach, based on symbolic reasoning techniques, to the problem of predicting radiated EMI levels from printed circuit boards. The expert system, currently under development at the University of Missouri-Rolla, USA, starts by extracting board geometry information from the board layout files. This information is fed into the classification algorithm, which determines the signal properties and nature of each net, using the knowledge stored in the knowledge base. The evaluation algorithm uses the available in formation to identify and evaluate critical circuit geometries, and then estimates the effect that these geometries have on system radiation levels. The expert system also looks for violations of basic EMC design rules. The main advantage of such a system over conventional software is that the expert system does not require the user to be an expert in EMC or circuit design

New broadband, low cost and compact MIMO radar frontends

En esta disertación industrial, se han abordado una variedad de nuevas ideas. En el capítulo 2, se expone una breve introducción a la teoría básica de los radares tipo MIMO, así como también conceptos esenciales como FMCW, TDM o la estimación de ángulos. En el siguiente capítulo, un radar de tipo MIMO es presentado. En el varias tarjetas de circuitos impresos son apiladas, creando de esta forma, una agrupación de antenas de gran ancho de banda bidimensional. Mis trabajo es presentado en este capítulo, así también como las imágenes radar finales. Al final, el incremento de resolución debido a la técnica MIMO se demuestra exitosamente. Una iteración de el prototipo es presentado en el capítulo 4. Este radar sustituye las múltiples tarjetas impresas por una sola, la cual contiene RSPA basadas en cavidades de aire. Este circuito se ha diseñado con dos cadenas de conmutadores independientes, de tal forma que se dos formas de onda podrían ser enviadas de forma simultánea. Por ello, un radar en tiempo real, como por ejemplo un radar OFMD puede ser probado con este hardware. La característica zona vacía de los radares MIMO ha sido ocupada con una segunda funcionalidad. Primero, con antenas espirales para las comunicaciones y después a cámara, la cual mejora la detección, clasificación y el rastreo de objetivos. El capítulo 5 introduce novedosos componentes de RF, de muy ancho de banda e integrables con tarjetas de circuito impreso como un Divisor Wilkinson y una antena impresa en 3D. Estos componentes han sido diseñado, fabricado y medido de forma satisfactoria. El gran ancho de banda objetivo permite a estos componentes operar para múltiples funciones. El capítulo 6 introduce nuevos componentes clave de bajas pérdidas como el acoplador Moreno y la antena de guía de ondas ranurada en una nueva y prometedora tecnología. ESIW reduce las pérdidas de las guías de ondas integradas eliminando el dieléctrico interno. Estos componentes han sido diseñados, fabricados y medidos. Los prototipos producidos son un primer paso antes de un refinamiento final antes de introducir el producto al mercado. Además, se han explorado tecnología más disruptivas para futuros proyectos.In this industrial dissertation, a variety of new and creative ideas has been adressed. In Chapter 2, a brief introduction to an existing MIMO radar theory as well as to the neccessary basic concepts of FMCW, TDM and angle estimation has been given. After that, in Chapter 3 a complete and fully functional MIMO radar has been presented. The sandwich approach enabled to stack PCBs to make up a modular bi-dimensional array of very wideband TSA antennas. My contributions to this radar have been presented in detail as well as the final imaging results, in which the increment of the resolution due to the MIMO technique has succesfully been tested. A next iteration of the portotype has been introduced in Chapter 4. This radar replaces the multiple stacked PCBs by a single one, which is populated with air-cavity-based RSPAs. This PCB has been designed with two independent switch chains, in such a manner that the two different waveforms can be sent simultaneously. Therefore, a real time radar, as for instance OFMD can be tested with this hardware. The characteristic inoccupied space at the center of a bidimentional MIMO array is filled with a second funtionality. Firstly, spiral antennas for communication have been designed, integrated and tested. Secondly, the spiral antennas have been cut off. In the remaining hole, a camara, which improves the detection, clasification and tracking of targets, has been placed. Chapter 5 presents new, very broadband (4-40 GHz) and integrable-with-PCBs RF components as a Wilkinson divider and a 3D printed TEM horn antenna. These components have succesfuly been designed, fabricated and tested. The targeted wide frequency range allows the usage of these components for multiple functions. In Chapter 6 new low losses key components as the Moreno cross-guide coupler and slotted waveguide antenna are presented in a new very promising technology. ESIW reduces the loss of the integrated waveguides (SIW) by removing the inner dielectric, following a very interesting fabrication process. These two components have been, designed, fabricated and measured. On one hand, the produced prototypes are the first step towards further Airbus refinement before introducing a product to the market. On the other hand, some disruptive technologies and components have been explored in order to keep track of the following advances in terms of innovation.En aquesta dissertació industrial, s'han abordat una varietat de noves idees. En el capítol 2, s'exposa una breu introducció a la teoria bàsica dels radars tipus MIMO i conceptes essencials com FMCW, TDM o l'estimació d'angles. En el següent capítol, un radar de tipus MIMO és presentat. Diverses targetes de circuits impresos són apilades, creant d'aquesta manera, una agrupació d'antenes bidimensional de gran ample de banda. El meu treball és presentat en aquest capítol, així també com les imatges radar finals. Al final, l'increment de resolució a causa de la tècnica MIMO es demostra amb èxit. La següent iteració del prototip és presentada al capítol 4. Aquest radar substitueix les múltiples targetes impreses per una sola, la qual conté RSPA basades en cavitats d'aire. Aquest circuit s'ha dissenyat amb dues cadenes de commutadors independents, de tal manera que dues formes d'ona podrien ser enviades de forma simultània. Per això, un radar en temps real, com per exemple un radar OFMD pot ser provat amb aquest radar. La característica zona buida dels radars MIMO ha estat ocupada amb una segona funcionalitat. Primer, amb antenes espirals per a les comunicacions i després per a càmera, la qual millora la detecció, classificació i el rastreig d'objectius. El capítol 5 introdueix nous components de RF, de molt ample de banda i integrables amb targetes de circuit imprès com un Divisor Wilkinson i una antena impresa en 3D. Aquests components han estat dissenyats, fabricats i mesurats de forma satisfactòria. El gran ample de banda objectiu permet a aquests components operar per a múltiples funcions. El capítol 6 introdueix nous components clau de baixes pèrdues com el acoblador Moreno i l'antena de guia d'ones ranurada en una nova i prometedora tecnologia. ESIW redueix les pèrdues de les guies d'ones integrades eliminant el dielèctric intern. Aquests components han estat dissenyats, fabricats i mesurats. Els prototips produïts són un primer pas abans d'un refinament final abans d'introduir el producte al mercat. A més, s'han explorat tecnologia més disruptives per a futurs projectes.Miralles Navarro, E. (2018). New broadband, low cost and compact MIMO radar frontends [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107960TESI