High order correction for pulse width modulation (PWM) digital/analog converters with reduced computation

A method for correcting distortion in a delta sigma modulator of at least second order, having at least two state variables responsive to feedback from an output quantizer and operating at an operating clock rate, comprising the steps of:

• determining a system equivalent to the modulator, the system operating at a higher clock rate, the higher clock rate being a multiple of the operating clock rate, wherein the output of the system is substantially linear at the higher clock rate;
• modeling the response to a system operation at the higher clock rate;
• modeling a correction to be applied to each integrator feedback path at the higher clock rate to correct the modelled distortion;
• computing the correction to be applied within the modulator at the operating clock rate such that the modulator operating at the operating clock rate substantially matches the operation of the system operating at the higher clock rate in response to the same outputs;
• and
• implementing the computed correction by applying at least two mutually nonlinear functions to the feedback from the quantizer, and adding the respective results to at least two state variables, wherein at least one of the at least two nonlinear functions comprises approximately zero when a modulator output signal is a maximum modulator output signal capable of being output by the quantizer or when the modulator output signal is a minimum modulator output signal capable of being output by the quantizer.