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.