Simple and accurate approaches to implement the complex trans-conductance suited for time-domain simulators for small-signal and large-signal table-based models

This paper focuses on the implementation of table-based models of high-frequency transistors for time-domain simulators at microwave and mm-wave frequencies. In this frequency range, the channel is not capable of responding to the excitation instantaneously therefore, a delay-time exists between the channel response and the channel excitation. This delay is represented by a complex trans-conductance in terms of circuit elements. The high-frequency models of transistors are required to have the implementation of complex trans-conductance, where the complex part accounts mathematically for the delay-time between the channel response and the channel excitation. This paper presents simple and accurate approaches to incorporate the complex trans-conductance in both small-signal and large-signal table-based models for time-domain simulators (MOS-AK International Meeting. Eindhoven, Netherlands, April 2008). Implementation approach for each model, small-signal and large-signal, is presented in separated sections. In the first step, the delay is realized by the introduction of an ideal transmission line between the channel excitation and the channel response. As transmission lines are not generally suitable for time-domain simulations, a lumped element equivalent network is introduced in the second step. The latter approach is fully compatible with time-domain simulators but frequency limitation, determined by the delay-time value itself, is introduced. Then the implementation of the complex trans-conductance in large-signal model is introduced. In terms of large-signal behavior, delay-time is important to achieve a non-quasi static model. Yet again there is limitation in terms of the frequency range that is determined by the delay value itself. The methodology is illustrated on the small-signal and the large-signal equivalent circuit of a Multi-Fin MOSFET transistor. Simulations are carried out by Cadence Spectre and Agilent ADS simulators, and comparisons are carried out between the simulation results and the measurements. Copyright © 2010 John Wiley & Sons, Ltd.