A 400 MHz 12 b 18 mW IF digitizer with mixer inside a /spl Sigma//spl Delta/ modulator loop

One method of IF digitization consists of a down-conversion mixer followed by a lowpass /spl Sigma//spl Delta/ modulator. However, as one moves to high IF, the down conversion mixer´s distortion deteriorates rapidly and more power has to be dissipated to restore the mixer´s distortion to an acceptable level. In order to achieve low-distortion while maintaining low power dissipation, a new digitizer that suppresses this mixer distortion by placing the mixer inside a modified /spl Sigma//spl Delta/ feedback loop, and capable of operating at 400 MHz, is presented.