Analysis of vertical via current increase due to via cylinder-to-ground capacitance

In this paper, we propose an enhanced network model for vertical via ground holes in planar microstrip circuits which includes the increase of vertical via current density in the direction of the ground plane. The increase of vertical via current occurs in the case when the width of the via pad is nearly equal to the via diameter and the inhomogenous fraction of the microstrip mode is incident on the via cylinder, so the vertical current can not be assumed as constant. The surface wave radiation of vertical dipoles close to the ground plane is much higher than from dipoles lying above, so the correct estimation of the current density on the via cylinder is essential.