Calculating the normalised determinant function using non-linear models in microwave office

Stability of a circuit is a very important design criteria. Microwave designers commonly use the well known Linvill or Rollett criteria, known as B or K criteria to determine the stability of an N-port network. These criteria are limited to its accuracy and fail in many cases. A rigorous method of testing such as the Normalised Determinant Function (NDF) is required before the B or K criteria is applied. The Normalised Determinant Function is a robust test of circuit stability but can be complicated to implement in a circuit simulator because it requires access to all active controlled sources in a circuit and multiple simulations. Access to the necessary controlled sources has recently been implemented in a non-linear model (Meerkat pHEMT model) for the first time, but some problems remain with the implementation of this useful feature. This thesis provides further work to mathematically analyse and simplify the NDF analysis technique to implement in small signal models that will later on aid Macquarie University's industry partner, MACOM Technology Solutions with the NDF implementation in their preferred Meerkat pHEMT model.