The use of multi tone dither in high speed A/D conversion

The use of `dither´ to extend the dynamic range of an analogue to digital converter is well known in digital audio. Dither signals are usually either noise or a sinewave. Noise performs a better dithering action than a sinewave, but cannot be removed by filtering. This paper describes the use of a three tone dither signal that has an improved dithering action and can be removed by filtering. Results are presented that show approximately 9 dB more spurious free dynamic range than for sinewave dither when applied to a practical high speed A/D converter