Extraction of a Multi-Dimensional Polynomial Device Model for an Improved Distortion Contribution Analysis Technique

This paper presents a method to characterize a multi-dimensional polynomial current and charge source models needed for a distortion contribution analysis technique that can identify the dominant nonlinearities and different mixing mechanisms. A separate model characterization step with carefully chosen test signals is used to break the inherent input-output correlation that otherwise complicates the model fitting. The proposed Volterra-on-top-of-harmonic-balance technique and improved polynomial fitting are then verified through the analysis of a 100-W LDMOS RF Doherty amplifier, which showed that, in this circuit, the cubic nonlinearity of the gate capacitance is the main culprit of AM-PM distortion.