Suppression of Cavity Resonant Edge Effects and PDN impedance using absorbing material

Cavity Resonant Edge Effects (CREE) in printed circuit boards (PCBs) and packages can cause severe power integrity (PI) and electromagnetic interference/compatibility (EMI/EMC) issues. Electromagnetic radiation from PCB edges are major sources of EMI/EMC problems in electronic devices. Power supply noise, in the form of fast changing currents (di/dt), traverses the power-return paths of PCBs and packages using power vias. CREE produces considerable level of noise along the edges of PCB and package power planes due to signal coupling between vias and reflection along PCB edges with transient currents. In this paper, we investigate an approach to minimize cavity resonant noise by placing absorbing material along the edges of a PCB board. The upper peak (anti-resonant) impedance of the power distribution network (PDN) is reduced significantly. In this paper the simulated example shows the absorbing material reduces the upper impedance peaks as much as to 8% comparing to the impedance peaks without absorption material. Conclusively, the results show that adding absorbing material along the PCB edges significantly improves the noise issues by suppressing CREE.