Radiated emission from a multilayer PCB with traces placed between power/ground planes

Mechanism of radiated emission induced by traces placed between power/ground planes and the radiation reduction technique are described. Those internal traces can cause voltage bounce between the power/ground planes and this bounce results in high-level radiated emissions at resonant frequencies. Radiated emission characteristics depend on the trace location in the board; radiation level is high when the internal trace is located at a high voltage bounce area. Radiation reduction techniques are also investigated. Scattering of decoupling capacitors on the power distribution planes is not a useful technique to reduce the voltage bounce at higher frequencies. To reduce the voltage bounce narrowing space between these planes is effective.