Digitale Signalverarbeitung

A sequence of N sine and/or cosine values, e.g. for Fourier Transforms, quadrature demodulation or test tone generation, is produced by interpolation from a geometrically-spaced table of initial sine values using a first interpolation formula. After being output, each sine value is replaced in the table by a further calculated value, so the sine table size is kept at M = (Log2N)+2 (where N is the number of sine values in the sequence). To avoid round-off errors at widely-spaced interpolations, a second interpolation formula is selectively used in which sine values are interpolated from cosine values. A cosine table is therefore maintained concurrently with the sine table.