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EMI-EMC Analysis and Noise Reduction on PCB

EMI-EMC Analysis and Noise Reduction on Printed Circuit Board
Cristian Gozzi, Application Engineer ANSOFT CORPORATION, Italy E-mail: cgozzi@https://www.sodocs.net/doc/115062249.html, Phone: +39 06 5916845

Agenda
Brief overview of EMI-EMC noise contribution on PCB EMI/EMC analysis
Ansoft Solutions & Simulation capabilities 5 Steps for EMC Analysis and Noise Reduction Simulation review
Question and Answers

Elements of EMC
EMI source EMI source Emission
Coupling process
EMI Filters EMI Filters Shields Shields
Conduction
Conductive Capacitive
Space & Field
Middle High Inductive Radiative Frequency Application
Shields Shields Shields Shields
EMI Filters EMI Filters
Shields Shields
EMS Immunity Immunity

PCB EMI Sources
Intentional Sources
Expected or easily predicted sources for radiation Emissions from intentional signals include loop-mode sources.
Unintentional Sources ( more than 90% of EMI *)
Unexpected or “surprise” sources Emissions from unintentional signals include common-mode, crosstalk coupling to I/O traces (PCB, PKG, and IC levels), power planes, and other board structures.
*Reference from “ PCB Design for RealWorld EMI Control ” Bruce Archambeault

Radiated EMI Basics
Loops in which currents flow act as antennas Area of loop determines radiation efficiency Injecting a realistic current excitation can predict radiation
i i i

Radiated EMI Basics
Current is the primary cause of loop radiation High impedance power distribution systems generate noise in proportion to current Inductive paths generate noise in proportion to current switching speed
V = IZ
PCB pwr/gnd layers
di V =L dt

Near-Fields from PCB
High |Z| at 137 MHz Low |Z| at 50 MHz

MIXED SIGNAL PCB Example
GPS
GPS
USB Digital Processing
Bluetooth

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