Noise and crosstalk reduction in analog to digital encoders

Abstract From the Canadian patent

A reduction in idle channel noise and crosstalk in a mid-riser-biased successive approximation encoder is achieved through the use of two polarity decisions. Encoder (401) assigns a sampled analog input signal to the closest one of a multitude of discrete signal levels or code steps. A comparator (109) provides this assignment by successive comparisons of the sampled signal with a series of reference signals (110). Each comparison produces a binary digit. The first comparison, or polarity decision is not transmitted and instead coupled to feedback circuitry (401) to reduce any d.c. component in the analog input signal to substantially zero. A second polarity decision is then made using a …