1 THE USE OF AN ACTIVE TEST BOARD TO VALIDATE A METHOD THAT PREDICTS DIFFERENTIAL MODE RADIATED EMISSIONS FROM PRINTED CIRCUIT BOARDS E. Leroux, A. Giuliano, C. Giachino R. De Smedt, Jan De Moerloose, W. Temmerman P. Fogliati, P. Belforte, B. Demoulin Presentation at EMC ’98 ROMA - September 14-18, 1998

2 INDEX l INTRODUCTION l MODELLING OF DIFFERENTIAL MODE RADIATION FROM TRACES BY THE MEANS OF GREEN DYADIC OF STRATIFIED MEDIA l EXPERIMENTAL VALIDATION USING AN ACTIVE TEST BOARD l CONCLUSIONS

3 INTRODUCTION Consider Electromagnetic Compatibility (EMC) aspects in electronic equipments only through compliance testings on the first prototype raises some problems: completion date costs Printed Circuit Boards (PCBs) are the main sources of radiation A lot of effort must be spent on PCB design, taken into account EMC aspects

4 Predict the Radiated Emissions (RE) at the design stage by the means of a post-layout simulation The needs: l trade-off between computation time and realism of results l to be able to modify the layout to improve PCB quality for EMC, link with CAD design tools is necessary l a modelling methodology for components that can avoid uncertainty due to the dispersion of electrical parameters of compoments INTRODUCTION (con’t)

5 MODELLING OF DIFFERENTIAL MODE RADIATION FROM TRACES Hypothesis: current distribution is calculated from results given by a Signal Integrity algorithm: radiation losses are not considered each rectilinear trace is supposed to radiate independently Vectorial sum of contribution of each recilinear segment

6 MODELLING OF DIFFERENTIAL MODE RADIATION FROM AN EMBEDDED MICROSTRIP   h rd rcd w D t   P P' y x z r Observation point L w

7 are essentially plane-wave transfer functions of the dielectric layered medium, that combine TE and TM plane-wave modes. They depend on: the spherical coordinates of the measuring antenna position in the local reference system of the trace. the spatial Fourier transform of the current density on the trace. DIFFERENTIAL MODE RADIATION FROM AN EMBEDDED MICROSTRIP: analytical formulation

8 THE ACTIVE TEST BOARD Most of interconnections are:

9 COMPARISON BETWEEN THE SPECTRUM (FFT) OF MEASURED, SIMULATED VOLTAGE (U6 OUTPUT)

10 COMPARISON BETWEEN MEASUREMENT AND SIMULATION OF RE BY THE ACTIVE TEST BOARD BATTERIES HOLDERS BACK OF THE BOARD

11 MEASUREMENT OF H FIELD AT 1 CM FROM THE BACK SIDE OF THE BOARD NEAR THE BATTERIES Three-axis scanning set-up (the top layer of the board is shown)

12 MODIFICATIONS DONE ON THE ORIGINAL BOARD Plated-through holes Ground metallization TOP BOTTOM

13 COMPARISON BETWEEN MEASUREMENT OF RE BY THE ORIGINAL BOARD AND THE NEW ONE EMI shield soldered to the ground metallization (new board)

14 COMPARISON BETWEEN MEASUREMENT AND SIMULATION OF RE BY THE NEW BOARD

15 MODELLING OF COMMON MODE RADIATION FROM A CABLE ATTACHED THE GROUND PLANE OF A BOARD: computation time, perspectives 15 minutes: simulation time (SUN ULTRA 1 workstation) to obtain currents and RE results of the board which presents 107 nets and 177 components PRESPECTIVES: Include the RE from the power/ground distribution l 4-ports and package models:simulation of SSN on power and ground pins l TLM method:ground bounce on planes l dipoles:radiation

16 CONCLUSION l The presented method: l takes into account effects of dielectric layers in the field calculation l does not need to discretise traces in short segments l reachs a good tradeoff between realism of results and computation time when radiation of microstrips is concerned l The tools can be effectively used in the CAD design flow l Simulation software and near field equipment are included in the THRIS environment An evolution of this method will be the prediction of RE from the power/ground distribution