Patent ID: 6927716

Claim:
A variable modulus interpolator for interpolating a fraction to a varying digital code representative of the fraction, the variable modulus interpolator comprising an Nth order sigma-delta modulator having N cascaded sigma-delta stages, where N is an integer greater than one, the sigma-delta modulator being responsive to the numerator and the denominator of the fraction for outputting the varying digital code, each sigma-delta stage having a stage input, the stage input to the first sigma-delta stage being adapted for receiving a selected value of the numerator of the fraction, and each sigma-delta stage comprising a feedback loop, a multiplier being located in each feedback loop for multiplying a value represented by a feedback signal in a corresponding feedback loop by a selected value of the denominator of the fraction prior to summing of a negative value of the feedback signal with the input to the stage input of the corresponding sigma-delta stage, so that the values of the numerator and the denominator are independently selectable.