As signal vias pass through a cavity, coupling can occur. Unfortunately, this source of impedance is often overlooked, resulting in problems with the power distribution network (PDN) that can be difficult to diagnose. At the high data rates of today’s designs, it is very easy to excite the low-frequency resonances and high-frequency resonant modes that are intrinsic to the geometry of a cavity. As a signal loses energy to such resonances it can fall victim to coupling to them. This paper provides an understanding of this phenomena along with methods for suppressing such noise.
noise, PCB, coupling vias