Optimal decoupling capacitors design for suppressing edge radiation of power/ground planes

Abstract

Stitching decoupling capacitors are utilized to suppress the edge electromagnetic radiation in a pair of power/ground planes in this paper. The parasitic effects, ESL and ESR, of decoupling capacitors connecting the power and ground in the board periphery are introduced into the normal mode waveguide theory to optimize the placements and specification of the decoupling capacitors. Applications to practical structures demonstrate an additional 18dB EMI suppression up to several GHz range by choosing suitable ESL and an ultra-high suppression at several hundred MHz by choosing suitable capacitor value. Both the full-wave simulation and experiment validate the design idea.