Power-bus Noise Reduction Using Ferrite-covered Open Stub in Printed Circuit Board

For suppressing the power-bus resonance at higher frequencies, which causes propagation of electromagnetic noise and detraction of power integrity, we proposed a lossy resonator filter with frequency selectivity and low loss. To suppress noise propagation in the power-ground plane pair of a printed circuit board (PCB) at high frequencies (over 1 GHz), a ferrite-covered open stub was formed on a PCB as a lossy resonator filter. Its characteristics were verified by not only full-wave simulation but also measurement using a vector network analyzer. The simulation and measurement results show that the noise in the power bus of the PCB at frequencies over 1 GHz is suppressed. Through a series of investigations focusing on the input impedance characteristics, this paper clarified that low impedance of the open stub around resonant frequency helps prevent the impedance of the power-ground plane pair from increasing due to parallel plate resonances to achieve power-bus noise reduction.