A novel DC-offset cancelling circuit for DCR

The paper describes a novel DC-offset canceling structure for a direct-conversion receiver (DCR). The proposed structure uses an I/Q tuning loop to remove DC-offset. The I/Q mismatch issue is discussed and, accordingly, a solution to suppress I/Q mismatch effects is adopted. A variable bandwidth technique is employed to accelerate the loop acquisition when the system is first turned on. Simulation results show that the differential DC-offset voltage is less than 3 mV after the loop becomes locked when a DC-offset of 100 mV is presented. Moreover, the tuning loop can efficiently suppress the effects of I/Q mismatch.