DELTA-SIGMA MODULATOR FOR FRACTIONAL-N FREQUENCY SYNTHESIS

摘要

A delta sigma modulator which uses at least one quantizer having a dead zone, The dead zone quantizer outputs a zero when its input is within the dead zone range, It outputs a predetermined value if the input is above the dead none range. If the input is below the dead zone range, the quantizer outputs another predetermined value. Ideally, the quantizer dead zone thresholds are complimentary in that the upper threshold for an input is the positive value of the lower threshold. Also, to save on accumulator bits, the delta sigma modulator selects a predetermined number of most significant bits at different stages.