Nonlinear Steady-State III–V FET Model for Microwave Antenna Switch Applications.

A nonlinear III–V field-effect transistor model is proposed for designing microwave antenna switches and related circuits. off-state gate and drain capacitance values of a pseudomorphic high-electron-mobility transistor (HEMT) derived from pulsed S-parameters with a deep off-state quiescent gate voltage are found to be much less voltage dependent than capacitance values measured by a nonpulsed bias owing to trap-induced dispersion effects. Our device model based on pulsed-bias CV characteristics accurately simulates switch nonlinearity. Both gate and drain capacitance values are assumed to be nonlinear, and a charge expression is developed for model implementation. For both capacitance values, a nonpulsed-bias CV curve is also utilized to maintain accurate capacitance at the quiescent voltage and, thus, accurate simulation of off-switch isolation. Additional terms are introduced to an existing drain current model to improve accuracy at high Vgs/\low\ Vds and subthreshold regions. Furthermore, the model is extended to multiple-gate devices. Harmonics generated from both off- and on -state switches, insertion loss, and isolation are accurately predicted for both single- and multiple-gate HEMTs. [ABSTRACT FROM AUTHOR]