This paper describes a rigorous and systematic procedure to derive a n
on-linear distributed FET model that can easily be implemented in CAD
routines of simulators based on harmonic balance techniques. The new m
odel is derived from a knowledge of the conventional linear lumped equ
ivalent circuit, from non-linear current sources extracted with pulsed
measurements, and from the physical dimensions of the FET. For fundam
ental and haromonic frequencies, the FET is modelled by N identical ce
lls. Each cell is made up of a non-linear two-port section inserted be
tween two linear four-port sections that simulate the coupling and the
distributed effects along the electrodes of the FET in the width dire
ction only. This non-linear distributed scaling approach to FET modell
ing has been applied to the analysis of a submicrometre-gate GaAs FET
at millimetre-wave frequencies, and the results were compared to the n
on-linear lumped element approach. This approach can be applied to oth
er transistors used in non-linear regions at microwave and millimetre-
wave frequencies.