Novel total nonlinear distortion measure and a new Signal to Total Distortion Ratio FOM for evaluation and optimization of PAs and linearization techniques

Although nonlinear distortion outside (ACPR) and within (EVM) signal bandwidth can be related to each other, it would possibly require a cost function to make a unique Figure-Of-Merit (FOM) for the overall distortion that includes in and out of the band distortion. It may be complicated to evaluate both ACPR and EVM simultaneously and find the optimum between these two measures during an optimisation of a PA for linearity. A novel metric for the nonlinear distortion that simultaneously evaluates distortion inside and outside of the signal bandwidth, have recently been developed. It includes memoryless nonlinear distortion and distortion caused by the memory effects, if present. A FOM represented as Signal to Total Distortion Ratio (STDR) is derived from the metric, which can be used for optimization of various linearity improvement technique applied to the Power Amplifier or Transmitter architectures. Some interesting features of this is the derivation of the average complex linear Gain.