A computer-implemented method is disclosed for verifying impedance in a differential
via pair. A target differential via pair is identified in a design database. A
desired modal characteristic impedance for the target differential via pair is
obtained. A two-dimensional window is established around the differential via pair
in which neighboring vias will be included in a modal characteristic impedance
calculation for the target differential via pair. A modal characteristic impedance
for the target differential via pair is calculated based at least in part on the
neighboring vias in the two-dimensional window. The target differential via pair
is flagged if the calculated modal characteristic impedance does not match the
desired modal characteristic impedance.
