Ultrafast Feedback A/D Conversion Made Possible by a Nonuniform Error Quantizer

The paper presents a means of increasing the speed of a tracking (feedback) A/D converter by replacing the single comparator with an error quantizer having exponentially spaced representative levels. The technique is particularly suited to digitizing the class of signals which exhibit a large covariance between temporally adjacent samples. An n bit converter realized in this way incorporates a quantizer which has a maximum of 2n comparators. Data compression may be simply realized by encoding the quantizer output to produce a DPCM word stream.