An Efficient Algorithm for Combining Linear Lumped Networks with the FDTD Method

In this study, an efficient approach is presented for processing two terminal networks consisting of arbitrary linear lumped elements into a single grid of FDTD (finite difference time domain) method. The relation of the node voltage to current of the networks can be expressed as a rational function (transfer function) in frequency domain. Field-updating equations and the rational function can be combined together into a new rational function since a single FDTD grid can be regarded as a Norton (or Thevenine) equivalent circuit. The proposed method is based on control theory and leads to an explicit efficient updating algorithm. A six-order circuit terminated with a transmission line is simulated to demonstrate the accuracy and efficiency of the proposed method. The simulation time of the proposed methods is about 30% less than a similar configuration using the equivalent current source (ECSM). method. Simulation results agree well with data from the ECSM and Agilent's commercial software ADS.