To optimize the linearity of mixers, one needs to recognize the origins and mixing mechanisms of dominant nonlinearities. This article presents a time-varying (TV) nonlinear analysis, where TV polynomial models are used to yield harmonic mixing functions in four simple mixer structures. Local oscillator (LO) waveform engineering has been utilized to tailor the nonlinearity coefficients, which were later fed into a numerical distortion contribution analysis tool to calculate the nonlinearity using a Volterra series-based approach. The spectra of the nonlinear voltages have been drawn, followed by plots breaking the final IM3 distortion down into its contributions. The effect of filtering on distortion has been illustrated in the end.