Extending the Best Linear Approximation to Characterize the Nonlinear Distortion in GaN HEMTs

In this paper, the best linear approximation (BLA) is extended to include second order nonlinearities. This extension is particularly useful for the analysis of low frequency distortion due to self-mixing. The self-mixing of a modulated signal due to even order nonlinear distortion creates a spectrum around DC as well as around the high order even harmonics. The frequency response at DC can be used to determine long term memory effects such as trapping and self-heating. The extended BLA is extracted for a GaN based HEMT to analyze the low frequency distortion and demonstrate the possibilities with the proposed method