Aalborg Universitet Predicting Radiated Emission of Apparatus Configured of Modules by Means of Numerical Methods and Module Level Measurements Sørensen, Morten Publication date: 2018 Document Version Publisher's PDF, also known as Version of record Link to publication from Aalborg University Citation for published version (APA): Sørensen, M. (2018). Predicting Radiated Emission of Apparatus Configured of Modules by Means of Numerical Methods and Module Level Measurements. Aalborg Universitetsforlag. Ph.d.-serien for Det Tekniske Fakultet for IT og Design, Aalborg Universitet General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. ? 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Downloaded from vbn.aau.dk on: November 24, 2020 BY MEAN BY PREDICTING PREDICTING S OF OF R N ADIATED ADIATED U PREDICTING RADIATED EMISSION OF M ERICAL METHOD ERICAL APPARATUS CONFIGURED OF MODULES EM BY MEANS OF NUMERICAL METHODS AND I SS ION OF OF ION MODULE LEVEL MEASUREMENTS S AND MODULE MODULE AND APP BY ARATU MORTEN SØRENSEN S C DISSERTATION SUBMITTED 2018 L ONFIGURED OF MODULE OF ONFIGURED EVEL MEA EVEL S URE M ENT S S MORTEN SØREN MORTEN S EN Predicting Radiated Emission of Apparatus Configured of Modules by Means of Numerical Methods and Module Level Measurements Ph.D. Dissertation Morten Sørensen Dissertation submitted October 5, 2018 Dissertation submitted: October 5, 2018 PhD supervisor: Prof. Gert Frølund Pedersen Aalborg University Assistant PhD supervisors: Assoc. Prof. Hans Ebert Aalborg University Assoc. Prof. Ondrej Franek Aalborg University PhD committee: Associate Professor Ole Kiel Jensen (chairman) Aalborg University Associate Professor Ville Viikari Aalto University Project Leader Sven Kühn Schmid & Partner Engineering AG PhD Series: Technical Faculty of IT and Design, Aalborg University Department: Department of Electronic Systems ISSN (online): 2446-1628 ISBN (online): 978-87-7210-338-9 Published by: Aalborg University Press Langagervej 2 DK – 9220 Aalborg Ø Phone: +45 99407140 [email protected] forlag.aau.dk © Copyright: Morten Sørensen Printed in Denmark by Rosendahls, 2018 Abstract It’s a big problem in the industry when the final apparatus, few weeks before it is released for production, fails the legally mandatory EMC test. It can cause extremely complicated, expensive, and time-consuming modifications of an otherwise completed apparatus and, in worst case, delays. Conversely, the fear of failed legally mandatory EMC test late in a project phase can cause overdesign and, hence, unnecessary and costly improvements. Therefore, there is a need for methods to predict EMC properties early in the project phase. This thesis addresses different methods to estimate the radiated emission from an apparatus configured of modules early in the project phase and long time before the apparatus is finalized. The methods make use of both module measurements, simulations and a combination of these. Radiated emission from an apparatus can be divided into radiation due to common mode currents on attached cables (common mode emission) and di- rect radiation from modules. Regarding the common mode emission, the the- sis shows that the ”Workbench Faraday Cage” method (IEC standard 61967- 5) unfortunately cannot be used as pre-compliance test, because the Faraday cage itself interferes with both the voltage driven and current driven cou- pling to attached cables. In addition, it is shown that common mode emis- sion from even a simple microstrip board is too complicated to be described by a lumped element model and that the radiation can vary as much as 20 dB depending on the printed circuit board’s (PCB) orientation. By making a free space measurement of the module alone, it can be esti- mated how much direct radiated emission the module will cause in the final apparatus. However, when the module is mounted in an apparatus, the radi- ation can change significantly due to enclosure, cables and other obstacles. Therefore, the thesis will focus on near-field scans as source for simula- tions. The main idea is to measure the tangential electrical and magnetic fields on a ”Huygens’ box” (HB) that encloses the sources and use the mea- sured fields as source for simulation (the HB method). The thesis investi- gates how step size and uncertainty in the measurement of the phase affect the prediction of free space radiated emission. In addition, it is investigated iii whether attached cables perturb the HB method, and whether all six sides of the HB are needed. The thesis shows that in many cases, the effect of scattering and reflection from nearby obstacles can be simulated by includ- ing the ground plane and substrate of the PCB in the HB. The limitations of the latter method are also investigated and it is shown that the method fails when strong resonances occur or when ground plane resonances are a source of radiation. Finally, it is discussed how to calibrate and characterize near-field probes at high frequencies and how to reduce the number of measurement points in ”Emission Source Microscopy”, a measurement method that, contrary to near field scans, directly reveals the locations of the sources for emission. Resumé I industrien er det et stort problem, når et apparat, få uger før det skal gå i produktion, ikke består EMC-myndighedstesten. Dette kan give anledning til dyre forbedringer af apparatet og i værste fald forsinkelser. Omvendt kan frygten for fejl i EMC-myndighedstesten sent i en projektfase medføre, at der overdesignes, og at unødvendige og fordyrende tiltag indføres. Derfor er der brug for metoder til at forudsige EMC-egenskaber tidligt i projektfasen. Denne afhandling omhandler forskellige metoder til, tidligt i projektfasen og længe før apparatet står færdigt, at skønne udstrålingen fra et apparat sammensat af moduler. Metoderne gør brug både af modulmålinger, simu- leringer og en kombination af disse. Udstråling fra apparater kan deles op i ledningsbåret udstråling pga. common mode strøm på kabler og direkte udstråling fra moduler. Om den ledningsbårne udstråling viser denne afhandling, at ”Workbench Fara- day Cage”-metoden (IEC standard 61967-5) desværre ikke kan bruges som pre-compliance test, da selve Faraday kassen forstyrrer både den spændings- drevne og strømdrevne kobling til vedhæftede kabler. Tillige vises det, at ledningsbåret udstråling fra selv et simpelt microstrip printkort er for kom- pliceret til at kunne beskrives med kredsløbsteori, og at udstrålingen kan variere op til 20 dB afhængigt af, hvordan printkortet vender. Ved at lave en fritfelt-måling af modulet alene kan man få et estimat af den direkte udstråling, som modulet forårsager i det færdige apparat. Men når modulet monteres i et apparat, kan udstrålingen ændre sig signifikant pga. kabinet, kabler osv. Derfor er nærfeltsscanninger som kilde til simuleringer i fokus i denne afhandling. Hovedideen er at måle de elektriske og magnetiske tangen- tielle felter på en ”Huygens’ box” (HB), der omslutter kilderne, og bruge de målte felter som kilde til simulering (HB-metoden). Afhandlingen un- dersøger, hvad stepstørrelse og usikkerhed i målingen af fasen betyder for forudsigelsen af fritfelt-udstrålingen. Derudover undersøges det, om ved- hæftede kabler perturberer HB-metoden, og om alle seks sider af HB’en er nødvendige. Afhandlingen viser, at ved at inkludere printkortets ground plane og substrat i HB’en kan man i mange tilfælde simulere effekten af v spredninger og refleksioner. Sidstnævnte metodes begrænsninger under- søges også, og det vises, at metoden fejler, når der opstår stærke resonanser, eller når ground plane resonanser er kilde til udstrålingen. Endelig behandles også, hvordan man kan kalibrere og karakterisere nær- feltsprober ved høje frekvenser, og hvordan man reducerer antallet af målepunk- ter i ”Emission Source Microscopy” - en målemetode, der modsat nærfelts- scanninger, direkte viser lokationerne af kilderne til udstrålingen fra det test- ede modul. Contents Abstract iii Resumév Thesis Details ix Preface xi I Introduction1 Introduction3 1 Introduction..............................3 1.1 Background for the Thesis..................3 1.2 Definitions...........................3 1.3 What Does Radiate in an Apparatus?...........4 1.4 Conducted emission vs. radiation directly from the PCBs6 1.5 Module Level Measurement Methods...........7 1.6 Repeatability of Measurements...............7 1.7 Numerical Methods and Near-field Scan.........8 1.8 Near-field Probes and Calibration.............9 1.9 Emission Source Microscopy................9 2 Aims of the Work........................... 10 2.1 Common Mode Emission.................. 11 2.2 Direct Radiated Emission.................. 11 2.3 Emission Source Microscopy................ 12 2.4 Industrial Aim........................ 13 3 Thesis Contributions......................... 14 3.1 Common Mode Emission.................