A new decoupling technique for suppressing radiated emissions arising from power bus resonance of multilayer PCBs

This paper presents a new decoupling technique for suppressing radiated emissions that arise from power bus resonance in multilayer printed circuit boards (PCBs). The technique utilizes a decoupling circuit composed of two decoupling capacitors and a power trace. The capacitors are placed at the power pin of an active device and at a common power bus in the board. They are connected to the power trace. The characteristic impedance of the trace is much higher than the impedance of the capacitor. The length of the trace between the capacitors is slightly shorter than 1/4 the wavelength of 1 GHz. Our tests of the four-layer PCB confirm suppression of the resonance, reduction of the amplitude of the power bus current and voltage, and suppression of radiation.