Dynamic Dithering of Delta-Sigma Modulators
The author has previously demonstrated the concept of noise-shaped dithering to a delta-sigma modulator. While such dithering successfully whitens the noise floor of the modulator, it is not without its faults. It will diminish the usable dynamic range by several decibels for large-magnitude inputs near full scale. For higher-order, single-stage modulators, it will also cause the threshold of instability to occur a few decibels sooner. These problems are ameliorated with dynamic noise-shaped dithering. This entails modulating the dither with a nonlinear function of the input signal in a manner that produces no additional distortion and is perceptually inaudible. This enables virtually all of the potential dynamic range and stability to be realized from the modulator while still whitening the quantization noise.
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