A core problem with digital Pulse Width Modulators is that effective sampling occurs at signal-dependent intervals, falsifying the z-transform on which the input signal and the noise shaping process are based. In a first step the noise shaper is reformulated to operate at the timer clock rate instead of the pulse repetition frequency. This solves the uniform/natural sampling problem, but gives rise to new non-linearities akin to ripple feedback in analogue modulators. By modifying the feedback signal such that it reflects only the modulated edge of the pulse train this effect is practically eliminated, yielding vastly reduced distortion without increasing complexity.
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