Oversampled, Linear Predictive and NoiseShaping Coders of Order N

Flrst-order predictive coders (e.g., DPCM) and first-order noise shaping coders (e.g., Interpolative coders) are familiar A/D eoaversion tedmlques. Using. feedback aetwork containing an A/D and a fint-order (single-pole) analog filter, they reduce the Dumber of A/D output levels, for a given SNR requirement, at the expense of the additional analog rilter complexity. Oversampling (i.e., sampling at higher than the Nyquist rate) provides excess bandwidth in the feedback loop, allowing further reductions in tbe number of A/D output levels at the expense of faster circuitry. This paper extends such first-order oversampled coders to inciude higher order analog filters under the constraint that the filters be independent of the statistical properties of the input analog sipal. The resulting robust Nth-order predictive and ooise-shaping coders allow N + 1/2 bits to be elimioated from the coder's A/D for each doubling of the sample rate. The design of such Nuch-order oversampled coders and an experimental third-order predictive coder are described.