Modeling and analysis on pass-through current decoupling method for multi-layer printed circuit board

It is well known that pass-through current, caused by the output buffer circuit of an IC during its transient state, can be a dominant source of the radiated field from the printed circuit board (PCB). In this paper, a modeling method is proposed to analyze this radiated field with a full-wave electromagnetic simulator using the method of moments (MOM). An analysis on the decoupling method, specifically for the case in which the IC is placed on a multi-layer PCB with segmented power and ground plane structure, has been carried out and found that there is close relationship between the PCB layer structure and the adequate location of decoupling capacitors. Our simulated results showed that there is a case that a general rule "decoupling should be placed close to VCC pin" is not adequate. Measurements have also been done with experimental model and the results are presented.