A general formulation for connecting sources and passive lumped-circuit elements across multiple 3-D FDTD cells

A previous extension of the finite-difference time-domain (FDTD) method to include lumpedcircuit elements is further extended to model lumped-element circuits connected across multiple FDTD cells. This formulation is needed to model many kinds of circuits, like those with a transistor or other active device connected across a transmission line with more than one dielectric. The FDTD analysis of a shielded suspended microstrip transmission line excited by a current source in parallel with a resistance illustrates the usefulness of the formulation.