A WLAN direct up-conversion mixer with automatic image rejection calibration

A direct upconverter for 5 to 6 GHz WLAN is presented that includes circuitry for automatic output spectrum calibration. For calibration, the RF signal is down-converted by reusing the up-conversion mixers, making the up- and down-conversion errors correlated. The transmit errors are determined based on only low-frequency measurements. The realized mixer achieves >40 dB image rejection.