Effect of additive dither on the resolution of ADCs with single-bit or multi-bit errors

Whereas the previous work by Wagdy et al. (1969, 1994) investigated the effects of additive dither on ideal A/D converters (ADCs) the topic of this paper is to investigate the effects on nonideal ADCs, i.e. ADCs with nonlinearity errors. To that end, the nonideal ADC transfer characteristics are considered as a superposition of the ideal characteristics plus nonlinearity errors. First the factor “D” developed in (1994) to assess the deviation of the transfer characteristics from the unity-gain line, is revisited. The nonlinearity spectra of the ideal quantization error function are then rederived using the appropriate scale factor. Second, “D” is derived for an ADC with error in any single bit. Some example dither forms, i.e. with various probability density functions (PDFs) are considered. Effects of dither for different error levels and bit orders are investigated, and the added resolution is computed via (1991). The analyst´s technique is entirely different from Carbone et al. (1994). Third, the paper investigates the effects of dither on ADCs with errors in more than one bit The deviation factor “D” is derived, which makes it possible to compute the added resolution. The paper thus presents, for the first time, a novel technique for quantifying the performance of ADC´s with multi-bit errors, in the presence of added dither. The approach is a streamlined one, which uses Fourier Transform and is fast to compute