Blind image suppression and carrier tracking in direct conversion receivers based on I/Q signal separation

The current trend in receiver architecture design is to simplify the RF front-end to get better integrability. One good example is the so-called direct-conversion receiver in which the desired RF channel is I/Q downconverted directly to baseband. In this paper, the I/Q mismatch problem in direct-conversion receivers is considered in detail, together with the more traditional carrier tracking task. It is shown that the fundamental effect of both the I/Q mismatch as well as carrier offsets is to create dependence between the I and Q signals. Based on this, a novel blind structure for joint carrier tracking and I/Q mismatch compensation is devised stemming from I/Q signal separation principle. The performance of the proposed approach is assessed using computer simulations and shown to be efficient and robust in the face of different imbalance and noise levels.