EMI/EMC ANALYSIS OF ELECTRONIC SYSTEMS SUBJECT TO NEAR ZONE ILLUMINATIONS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Zulfiqar A. Khan, M.S., B.S. ***** The Ohio State University 2007 Dissertation Committee: Approved by Professor John L. Volakis, Adviser Professor Prabhakar H. Pathak Adviser Dr. Chi-Chih Chen Graduate Program in Electrical and Computer Engineering c Copyright by Zulfiqar A. Khan 2007 ABSTRACT There is an increasing interest to evaluate performance of electronic systems sub- ject to electromagnetic interference (EMI). To this end, an efficient technique for system level EMI/EMC analysis of electronic systems was recently proposed. This scheme, referred to as the hybrid S-matrix method, is based on introducing an ad- ditional port on the printed circuit board (PCB) and cable network to represent the plane wave excitation. The scattering matrix for the network (with the added port) is generated once the transmission line (TL) modes are extracted from the induced voltages. The resulting hybrid S-matrix allows for complete characterization of a mi- crowave network in presence of enclosures or other scatterers. It can then be ported into a circuit solver for complex EMI/EMC analysis of electronic devices. This dis- sertation extends the hybrid S-matrix approach to near zone sources. A key aspect of this generalization is the use of the FFT rather than the GPOF to identify the TL modes in presence of the continuous spectrum of forced modes introduced by the near zone sources. Examples are shown to validate the generalized hybrid S-matrix method. These include a multi-layered PCB in the presence of nearby cables and when enclosed by the metallic structures with openings. The final chapter of the dissertation contains numerous experimental examples that provide for the first time a set of realistic EMI/EMC reference data. Specifically, field penetration through apertures and coupling of penetrating wires onto the printed circuit boards (PCBs) ii enclosed by resonant structures are considered. In contrast to other measurements, we focus on multi-cavity enclosures in presence of cables and PCBs. The purpose of this experimental study is to provide accurate reference data for possible future validation of various computational tools and to test their accuracy and efficiency on realistic platforms. In particular, we validate the proposed hybrid S-matrix method. iii Dedicated to Laila iv ACKNOWLEDGMENTS I have so many reasons to thank Prof. Volakis that I can’t mention all of them here. He has not only guided me in my technical work, encouraged me to take risks in my research and helped me in improving my communication skills but also he also helped me resolve many personal challenges that I had to face during my PhD. For all these reasons and more, I will always remain grateful to him. I also want to thank Dr. Yakup Bayram for his guidance throughout my work and helping me understand very important details of the hybrid S-matrix approach. I am grateful to Prof. Prabhakar Pathak, Dr. Chi-Chih Chen and Professor Patrick Roblin for their valuable suggestions and agreeing to be on my PhD commit- tee. Throughout my stay in the Lab, I had a great time with fellow ESL students. I wish to thank all of them. Special thanks are to Brian Usner, Edwin Lim, Ming Lee, Ioannis Tzanidis, Tao Peng, Paul Chang, Salih Yarga, Gokhan Mumcu, Jae-Young Chung and Stylianos Dosopoulos; for the memorable time I spent with them. During these years, I had to face some very difficult challenges in my personal life. I could not have survived in these hardships if my wife, Laila, had not constantly supported me. I thank her for everything she did for me. Finally, I thank my parents who always supported and prayed for me. v VITA February 24, 1974 . Born - Sargodha, Pakistan December, 1997 . B.Sc. Electrical Engineering University of Engg. & Technology, Lahore, Pakistan December, 2001 . M.S. Electrical Engineering Oklahoma State University Stillwater, OK February, 1998 - July, 2001 . Assistant Manager R & D, Advanced Engineering Research Orga- nization - Pakistan January, 2002 - July, 2004 . Graduate Research Assistant, Oklahoma State University Stillwater, OK. October, 2004 - present . Graduate Research Assistant, Ohio State University Columbus, OH. PUBLICATIONS Research Publications Z. A. Khan, C. F. Bunting and M. D. Deshpande, “Shielding Effectiveness of Metallic Enclosures at Oblique Incidence and Arbitrary Polarizations.” IEEE Trans. Electro- magnet. Compat., vol. 47, no. 1, pp. 112-122, Feb. 2005. V. Rajamani, C. F. Bunting and M. D. Deshpande and Z. A. Khan, “Validation of Modal/MoM in Shielding Effectiveness Studies of Rectangular Enclosures with Apertures and a Preliminary Investigation of the Input Impedance of a Wire located inside the Cavity for Varying Positions.” IEEE Trans. Electromagnet. Compat., vol. 48, no. 2, pp 348-353, May 2006. vi Z. A. Khan, Y. Bayram and J. L. Volakis, “EMI/EMC Measurements and Simulations for Cables and PCBs enclosed within Metallic Enclosures,” submitted to IEEE Trans. Electromagnet. Compat., Z. A. Khan, Y. Bayram and J. L. Volakis, “Hybrid S-parameters Analysis of PCBs and Cables subject to Non-Plane Wave Illuminations.” IEEE APS International Symposium, 10-15 June 2007. Z. A. Khan, Y. Bayram and J. L. Volakis, “An Integrated Hybrid Solver and Mea- surements for EMI/EMC Analysis of Cables and PCBs Enclosed within Metallic Structures.” IEEE EMC International Symposium, vol. 2, pp. 534-538, 14-18 August 2006. Z. A. Khan, J. L. Volakis, “Experimental and Analytical Study of EMC/EMI effects on PCBs and Cables enclosed within Metallic Structures.” IEEE APS International Symposium, pp. 49-52, 9-14 July 2006. Z. A. Khan, Y. Bayram and J. L. Volakis, “Experimental Study of Electromagnetic Interference (EMI) on PCBs and Cables enclosed in Complex Structures.” National Radio Science Meeting, 4-7 January 2006. Y. Bayram, Z. A. Khan and J. L. Volakis, “Experimental and Theoretical Study of Digital Circuits Subject to Electromagnetic Interference,” URSI Boulder Meeting, January 2005 Z. A. Khan, C. F. Bunting, “Shielding Effectiveness Studies of Rectangular En- closures with Apertures against EM Fields with Arbitrary Angles of Incidence and Polarizations,” IEEE EMC International Symposium, vol. 1, pp. 209-212, 18-22 August 2003. Z. A. Khan, Shih-Pin Yu and C. F. Bunting, “Statistical Shielding Effectiveness - a Modal/Moment Method Approach to Characterize the Average Shielding Effective- ness Over a Wide Frequency Range including Resonances,” IEEE EMC International Symposium, vol. 2, pp. 532-536, 18-22 August 2003. vii FIELDS OF STUDY Major Field: Electrical and Computer Engineering Studies in: EMI/EMC Analysis of Mixed Signal Circuits Professor John L. Volakis EMI/EMC Analysis of Shielding Enclosures Dr. Charles F. Bunting viii TABLE OF CONTENTS Page Abstract . ii Dedication . iv Acknowledgments . v Vita . vi List of Figures . xii Chapters: 1. EMI/EMC Analysis of Electronic Systems . 1 1.1 Introduction and motivation . 1 1.2 Challenges in EMI/EMC analysis of electronic systems . 2 1.3 Mixed signal EMI/EMC analysis of complex electronic systems using a decomposition approach . 3 1.4 Hybrid S-matrix approach for concurrent on/off board EMI/EMC analysis of electronic systems . 4 1.5 Contributions of this dissertation . 6 1.6 Dissertation layout . 6 2. Hybrid S-Parameters for External Plane Wave Excitation of Electronic Circuits . 7 2.1 Hybrid S-matrix Approach . 9 2.2 Derivation of the hybrid S-matrix . 12 2.2.1 Decomposition of the induced transmission line voltage . 12 2.2.2 Extracting VTL and Vforced from Vtotal ............ 14 ix 2.2.3 Incorporating VTL into S-parameters . 15 2.2.4 Calculating the hybrid S-parameters {HS} ......... 16 2.2.5 Algorithm for calculating the hybrid S-matrix . 18 2.3 Plane wave coupling to non-uniform transmission lines . 22 2.3.1 Plane wave coupling to PCBs with connecting planar wires 24 2.3.2 Plane wave coupling to PCBs with connecting vertical wires 28 2.4 Hybrid S-matrix for PCBs and wires enclosed by cavities . 29 2.4.1 Rectangular cavity enclosing a PCB with connecting planar wires . 29 2.4.2 PCB connected with vertical wires and enclosed by a rectan- gular cavity . 36 2.4.3 PCB connected to oblique wires and enclosed by a rectangu- lar cavity . 38 2.5 Conclusions . 38 3. Hybrid S-matrix Approach for Non plane wave EMI Excitations . 42 3.1 A spectral domain approach for extracting TL and forced modes from the EMI induced voltages on a transmission line . 45 3.1.1 Bandwidth approximation of the induced forced modes . 48 3.1.2 Algorithm for extracting the hybrid S-matrix for near-zone EMI excitations . 49 3.2 Validation Study . 50 3.2.1 Multi-layered PCB exposed to EMI from a near zone wire . 51 3.2.2 Enclosed PCB exposed to EMI from a near zone source . 56 3.3 Conclusions . 57 4. Experimental Validation of the Hybrid S-matrix Approach for Complex Structures . 59 4.1 Measurement setup: Description of cavities, PCB and the field sens- ing probe . 61 4.2 EMI coupling onto enclosed cables via apertures and penetrating wires 64 4.2.1 Field penetration through apertures into the empty multi- section enclosure . 65 4.2.2 EMI coupling onto enclosed cables via apertures and pene- trating wires: . 65 4.3 Validation of the scattering matrix approach for EMI/EMC analysis of PCBs enclosed by multi-cavity structures . 70 4.3.1 EMI coupling to PCB traces enclosed by multi-cavity structures 70 4.4 Conclusions of the experimental study . 74 x 5. Conclusions and Future Work . 76 Appendices: A. Agrawal’s Coupling Method .