Recently there has been a renewed interest in improving power amplifier performance via input waveform engineering. In order to support this development it is important that non-linear behavioral device models can accurately describe and fully account for the high levels of input harmonic signal injection necessary. The work presented in this paper introduces an adapted mixing model formulation, which was used to extract input second harmonic model coefficients from a set of simultaneous active fundamental load-pull and harmonic sourcepull measurements at 9 GHz. It was observed that a fourth order model was sufficient to capture the response of the scattered travelling b 2,1 and b 2,2 waves to a confidence of 99.46% and 97.62% respectively of the measured data. Hereafter the behavioral model was used to accurately generate the full fundamental output impedance space and the respective port current and voltage waveforms within a CAD environment.