A carrier leakage auto-calibration circuit with a direct DC-offset comparison technique for a WiMAX transmitter

We propose an RF-detector-less carrier leakage suppressor for a WiMAX transmitter. The proposed circuit directly detects the DC offset of a transmitter path and minimizes it, thus reducing carrier leakage. The correct DC-offset feedback to a baseband is achieved by performing an absolute offset comparison after the general binary search technique. The suppressor is integrated in the direct-conversion transceiver of a WiMAX fabricated in 90-nm technology. The measured carrier leakage is better than -32 dBc over the complete transmitter power range.