Influence of via stubs with different terminations on time-domain transmission waveform and eye diagram in multilayer PCBs

Plated though-hole (PTH) vias are extensively adopted in multilayer printed circuit boards (PCBs). Unused portions of PTH vias become open stubs, which excite the resonance mode and degrade signal integrity (SI). This work investigates how open via stubs in multilayer PCBs affect the time-domain transmission (TDT) waveform and eye diagram. Exactly how time-domain reflection affects the open via stubs on TDT waveform is also studied using the lattice diagram. Additionally, the R and RL terminations of open via stubs are developed to improve SI in previous studies. Moreover, the RC termination of open via stubs is proposed to improve the performance of SI, which is the same as that of the R termination in this work. RC termination is also characterized by its nearly zero DC power consumption. Furthermore, different terminations are compared with respect to how they improve the TDT waveforms and eye diagrams.