DC power-bus design using FDTD modeling with dispersive media and surface mount technology components

DC power-bus modeling in high-speed digital design using the finite-difference time-domain (FDTD) method is demonstrated herein. The dispersive character of the dielectric layers used in printed circuit board substrates is taken into account in this study. In particular, FR-4 is considered. The complex permittivity of the dielectric is approximated by a Debye model. A wide-band frequency response (100 MHz-5 GHz) is obtained through a single FDTD simulation. Good agreement is achieved between the modeled and measured results for a typical dc power-bus structure with multiple surface mount technology (SMT) decoupling capacitors placed on the printed circuit board (PCB). The FDTD method is then applied to investigate some general approaches of power-bus noise decoupling.