Excess loop delay compensation for continuous-time ΔΣ modulators using interpolation

A new excess loop delay compensation technique for continuous-time DeltaSigma-modulators by using signal interpolation is presented. This technique uses an auxiliary differentiator in the feedforward path to construct a signal interpolation at the input of the quantiser to enable an early decision that compensates for excess loop delay. A simple tuning for the interpolation coefficient makes this technique suitable for lowpass, as well as bandpass, modulators. The proposed technique enables the compensation of any amount of delay and does not impose modification on loop filter transfer function or circuitry.