Digital-to-digital code converter

Claim 1

A digital-to-digital code converter comprising: an input terminal for receiving an input signal including a series of groups, where each group comprises a sequence of N separate digital sample values occurring at a first predetermined rate and N>1; an output terminal; and processing means responsive to the input signal at the input terminal for performing sinc 3 processing on the N digital sample values of each input group to generate therefrom a representative single digital output value for each input group at a second predetermined rate at the output terminal, the second predetermined rate being slower than the first predetermined rate, the processing means comprising, first, second and third accumulation means disposed in a first, a second and a third stage, respectively, of the code converter, the accumulation means and the stages being arranged in cascade and each accumulation means includes means for adding each digital sample value received from the preceding stage during a current group period to a current accumulated value of the digital sample values received previously during that current group period; and first, second and third subprocessing means disposed in the first, second and third stages, respectively, for processing a resultant overall accumulated value obtained by the associated accumulation means at the end of each group period and generating a separate appropriately weighted intermediate value associated with each input group period, which intermediate values from each of the three stages, and associated with an input group, are combined to provide the sinc 3 processed representative single digital output value from the code converter.