Linearization of a sigma-delta modulator by a proper loop delay

The influence of a loop delay on the effective transfer characteristic of the quantizer and on the linearity of a first-order sigma-delta modulator is investigated. It is shown that the idle channel noise (ICN) of a first-order sigma-delta modulator acts as a dither signal and linearizes the transfer characteristic of the 1-bit quantizer. The ICN depends on the loop delay T_dl (conversion times inside the loop). Optimum values are Tdl=0.25 T and T_dl=0.75 T (T=sampling period). These results are confirmed by calculations and simulations