Undesired-resonance Analysis and Modeling of Differential Signals Due to Narrow Ground Lines Without Stitching Vias

Undesired resonances on high-speed differential signals are studied in this paper, which is caused by the adjacent narrow ground line without stitching vias. Due to space limitations in the high-speed channel layouts of certain package applications, the ground (GND) line is often narrow and has insufficient stitching vias, potentially causing undesired resonance in high-speed differential signals. In this study, these undesired resonances were investigated using 3D simulations, revealing that they can be modeled as parallel-coupled half-wavelength resonance. The resonance frequency of the parallel-coupled half-wavelength resonance structure can be predicted well using the formula based on the GND line length. Moreover, three potential solutions to undesired resonance are proposed, providing a practical guide for GND line routing in specific applications.