Using a C++ based simulation framework and automatic differentiation techniques for advanced non-linear modelling of microwave active devices

摘要

In this paper we describe the use of a novel, flexible, and highly modular simulation environemt called Sframe, for microwave device modelling and circuit simulation. The software architecture of Sframe (1, 2), is based on object orientation, automatic differentiation, and wide use of packaged numerical software. The use of automatic differentiation technidques in Sframe greatly simplifies device modelling: it leads to very compact model codes, simplifies the implementation process and eliminates many common sources of error. The same model code is suitable for all analyses of interest such as: DC, linear small-signal, non linear time domain, and harmonic balance. The paper presents tests with the implementation of an advanced non-linear GaAs FET model in Sframe. This equivalent circuit based model (5, 6), introduces novel soltuions with respect to the modelling of the non-linear gate charge and drain current, as well as the AC dispersion of transconductance and output conductance. DC, smallsignal AC, and single-tone large-signal simulation tests have been successfully carried out and the results are compared with experimental data, for the case of a 0.5 x 300mum GaAs MESFET. The large-signal tests are done using a novel implementation of the harmonic balance algorithm (4) which is briefly described in the paper.