| A global modeling concept for modeling microwave circuits is described. This concept allows the modeling of electromagnetic (EM) and thermal effects to be included in the simulation of electronic circuits, by viewing EM and thermal subsystems as subcircuits. Then, circuit analysis techniques are developed from a general state variable reduction formulation. This general formulation, based on the state variables of the nonlinear devices, allows the analysis of large microwave circuits because it reduces the size of the nonlinear system of equations to be solved. One of the derived analysis techniques is based on convolution and therefore provides modeling of frequency-defined network elements not present in conventional circuit simulators. Another analysis technique based on wavelets that would enable the multiresolution analysis of circuits is investigated. Also, a reduced state variable formulation using conventional time marching schemes is developed. It is shown that this can achieve more than an order of magnitude improvement in simulation speed compared to that of traditional circuit simulation methods. All these developments are implemented in a circuit simulator program, called Transim. This program provides unprecedented flexibility for the addition of new device models or circuit analysis algorithms. Transim supports the local reference concept, which is fundamental to the analysis of spatially distributed circuits and also to simultaneous thermal-electrical simulations. Transim is applied to the transient simulation of a 47-section nonlinear transmission line considering frequency dependent attenuation for the first time and the transient simulation, also for the first time, of two quasi-optical power amplifier arrays. |
