Estimating the via-plane capacitance for differential vias with shared-antipad based on analytical equations

Shared-antipad via structure is commonly used for high-speed printed circuit board (PCB) design. Therefore, an accurate via-plane capacitance evaluation for this kind of geometry is critical to facilitate engineering design. In this paper, the analytical equation of via-plane capacitance for separated-antipad via structure is extended to the shared-antipad via structure case, by using the equivalent area of antipad and ratio revision method. The proposed method is validated with numerical methods in HFSS for a typical structure widely used in practical high-speed PCB design.