A global modeling concept for modeling microwave circuits isdescribed. This concept allows the modeling of electromagnetic (EM)and thermal effects to be included in the simulation of electroniccircuits, by viewing EM and thermal subsystems as subcircuits. Then,circuit analysis techniques are developed from a general statevariable reduction formulation. This general formulation, based on thestate variables of the nonlinear devices, allows the analysis of largemicrowave circuits because it reduces the size of the nonlinear systemof equations to be solved. One of the derived analysis techniques isbased on convolution and therefore provides modeling offrequency-defined network elements not present in conventional circuitsimulators. Another analysis technique based on wavelets that wouldenable the multiresolution analysis of circuits is investigated. Also,a reduced state variable formulation using conventional time marchingschemes is developed. It is shown that this can achieve more than anorder of magnitude improvement in simulation speed compared to that oftraditional circuit simulation methods. All these developments areimplemented in a circuit simulator program, called Transim. Thisprogram provides unprecedented flexibility for the addition of newdevice models or circuit analysis algorithms. Transim supports thelocal reference concept, which is fundamental to the analysis ofspatially distributed circuits and also to simultaneousthermal-electrical simulations. Transim is applied to the transientsimulation of a 47-section nonlinear transmission line consideringfrequency dependent attenuation for the first time and the transientsimulation, also for the first time, of two quasi-optical poweramplifier arrays.
