Design principles for modeling and simulations of microwave circuits

It has often proven difficult to simulate microwave and RF circuits accurately. This paper presents an easy method for modeling and simulation of nonlinear active microwave circuits using the Ansoft Serenade 8.0 Design Environment. Starting with some simple circuits (MESFET mixer circuits, GaAs BJT feedback microwave amplifier), the authors describe the main principles of simulating RF and microwave circuits and a new method for modeling active RF devices (such as MESFETs and GaAs BJTs) in order to obtain the best results for multitone nonlinear analysis. The new proposed method also covers the stability problems, based on the Nyquist stability criteria, and the matching impedance Smith plots of the RF circuits.