Large-signal distributed millimeter-wave multifinger pHEMT modeling using time-domain technique

Abstract

The finite-difference time-domain (FDTD) method is used for the large-signal modeling of a multifinger pHEMT, which is considered as five nonlinear coupled distributed transmission lines. The developed model, which is based on the exact physical layout of multifinger pHEMT, not only accurately describes the propagation effects along the electrodes at higher frequencies but it also includes major nonlinearities of the I–V and Q–V characteristics. Using the transmission line theory, a proper nonlinear equivalent lumped circuit model is allocated for the differential length of the quintuple-line transistor and the nonlinear active multiconductor transmission line (NAMCTL) equations are derived. These nonlinear, coupled differential equations are numerically solved using the FDTD method. The proposed model is applied to a 100 nm GaAs pHEMT and the simulation results are compared with the results of conventional sliced model in Keysight ADS simulator. The developed transient nonlinear model accurately predicts both the S-parameters (1–150 GHz) and large-signal power performances especially at millimeter wave frequency range. The proposed model can be useful in design and analysis of various types of high-frequency nonlinear integrated circuits.