Design Considerations to Reduce Conducted and Radiated EMI

Schneider, Matthew J. M.S., Purdue University, May 2010. Design Considerations to Reduce Conducted and Radiated EMI. Major Professor: John P. Denton. This work evaluates the effects of conducted and radiated EMI due to improperly designed circuits or printed circuit board (PCB) layouts. Common circuits used in a wide range of electronic devices are evaluated using both good and poor design techniques. Additional evaluations are performed to measure the effects of EMI on cabling used for digital communication or RF purposes. Finally, a consumer product is evaluated which must pass regulatory agency requirements in order to be sold in the consumer market. Potential solutions to common EMI problems are then implemented and discussed. This work will look at individual circuits and evaluate design flaws that contribute the largest amount of radiated emissions. Avoiding poor circuit designs and PCB layout mistakes reduces the amount of radiated emissions from any product. This work discusses the theory of electromagnetics and how it pertains to EMI events, then addresses the practical problems associated with EMI using common circuits to illustrate EMI effects. It is important to understand why EMI related effects are becoming more critical, and to show why EMI problems should be corrected within the design phase.