As digital circuits became faster, direct coupling among power planes in multilayer printed circuit boards (PCB) became a major concern for signal integrity/power integrity and electromagnetic interference (EMI). Fast signals produce electromagnetic waves that can propagate by means of the parallel plates in the PCB, induce noise on the signals passing through the power bus (vias) and radiate from the edge of the board. The present study focuses on the analysis of the noise that propagates from a power plane to another power plane due to their proximity. To mitigate this problem, proper design of both power and ground planes in the stack-up is illustrated. A test board is fabricated and measurements are performed in order to validate the numerical electromagnetic model.
Reprinted with permission of MICROWAVE JOURNAL® from the February 2012 ©2012 Horizon House Publications, Inc.