On the impact of analog-to-digital conversion on blind I/Q imbalance parameter estimation in low-IF receivers

The low-IF receiver is very attractive, because the need for an analog image rejection filter is avoided. Instead, the image rejection is realized by I/Q signal processing. However, unavoidable imbalances between the I- and Q-branch in the analog part of the receiver result in a limited image attenuation. In previous work a blind I/Q imbalance compensation scheme for low-IF receivers was presented and its performance was analyzed. However, the impact of the analog-to-digital conversion (ADC) was not taken into consideration. In particular, the quantization noise, which is unavoidable in practical implementations, has been neglected. In this paper this blind I/Q imbalance compensation scheme is analyzed regarding to its sensitivity to an imperfect ADC. It can be shown by means of analysis as well as simulation, that the compensation scheme is robust against ADC effects.