Modeling and Measurements of Electrical and Thermal Memory Effects for RF power LDMOS

Accurate modeling of memory effects is important for design of amplifiers with high requirements on linearity. In this work, asymmetries in third order intermodulation distortion products (IM3) were measured for different tone-spacings and compared to simulations. An accurate large-signal model and careful modeling of the test circuit, especially the drain bias feeds is important for correct prediction of sideband asymmetries. Transient thermal measurements were employed to extract a thermal network with two time constants, one for the die and another one for the package. The IM3 asymmetries were found to be dominated by impedances in the output circuit for large tone-spacings; for very small tone-spacings (< 10 kHz), thermal effects have an important influence. The IM3 asymmetries agreed qualitatively well between simulations and measurements as a function of output power for different tone-spacings.