Impact and digital estimation of nonlinear impairments in analog baseband processing stages

The digital compensation of RF imperfections is promising, but requires accurate models for the influence of the impairments on the baseband signals. To this end, this paper proposes a model for imperfections occurring in the popular direct conversion receiver architecture. It extends the previously applied IQ imbalance models by also taking DC offsets and nonlinearities from the output stage of the mixer up to the input stage of the ADC into account. Moreover, the impact of this more extended impairment model on the received baseband signals is derived. Finally, an estimation algorithm is presented to estimate the parameters of this model for digital compensation of the influence of these imperfections. Numerical results show that this estimation approach can achieve accurate estimates of the impairment parameters.