A quadrature sampling scheme with improved image rejection for complex-IF receivers

In complex-IF receivers, I/Q imbalances will limit their image rejection performance. In this paper, a quadrature sampling scheme combining the function of IF-to-baseband conversion is proposed to transform the image problem caused by I/Q imbalances in this stage to the less important self-image problem. With this scheme, signal is sampled at the IF stage but digitized at baseband. DC and other low-frequency noises are circumvented while baseband /spl Delta//spl Sigma/ modulators can be used. Circuit simulations show that the proposed method removes completely the image interference due to I/Q imbalances that exist after the IF input.