Wannamaker, R.A., S.P. Lipshitz and J. Vanderkooy, "Dithering to Eliminate
Quantization Distortion," Proc. of the Annual Meeting of the Canadian Acoustical
Association, Halifax, Nova Scotia, 1989 Oct. 16-19, pp. 78-86. (invited
review paper).
ABSTRACT
Practical digital storage and transmission systems require the
representation of infinite precision analog information with
finite bit-length binary words. The attendant loss of resolution
introduces distortion into the signal unless appropriate
preventive measures are taken. This paper will provide a survey
of the "dithering" technique, in which a small additive dither
noise is introduced into the signal before analog-to-digital
conversion. It will be shown that with properly chosen noise
characteristics it is possible to retain the resolution of the
analog system and eliminate distortion in the output at the
expense of a small decrease in output signal-to-noise ratio. It
will also be seen that subsequent digital signal processing can
destroy the benefits thus attained if truncation or rounding are
applied to the results of internal arithmetic in order to yield an
acceptable output wordlength. Application of a proper digital
dither before the final length reduction will ensure that this
does not occur. Spectral shaping of the dither to decrease the
output noise audibility in audio applications will be explored.
In addition, the imminent technology of noise-shaping converters
will be discussed, and the possible role of dither in such systems
examined.