Techniques for preventing tonal behavior of data weighted averaging algorithm in /spl Sigma/#x03A3;-/spl Delta/#x0394; modulators

Abstract

Two techniques for prevention of in-band tones in DWA mismatch noise shaping algorithm are presented. "Offset technique" moves in-band tones away from baseband, improving SNR by 10 dB, and attenuates maximum in-band tone by as much as 25 dB. "Randomized DWA" is a combination of simultaneous randomization and DWA, which attenuates tonal behavior in all frequencies, preventing aliasing of tones or tone shifting for any arbitrary input signal.Index Terms-A/D and D/A converters, data-weighted averaging, sigma-delta modulators.

A Bandpass Mismatch Noise-Shaping Technique for<tex>$Sigma$</tex>–<tex>$Delta $</tex>Modulators

“…The state variable " " acts in a way that gives the units already selected less priority for re-selection so the rest of the units get the chance for selection. This results in low-pass noise shaping because of (3) as discussed in [11]. For bandpass case as discussed in Section II we require the summation of "difference" in the errors in consecutive outputs (6-a) be small and not grow with time.…”

“…From [11] and [13], the average total mismatch noise power in the time domain is (12) We know that the noise shaping for center frequency is of the form with to be determined. Using Parceval's relation one could find (13) Assuming that an over-sampling ratio is represented by , the total mismatch noise in the normalized pass band ( ) for notch frequency at is…”

BandPass Dynamic Element Matching for low OSR high resolution Delta Sigma Modulators

“…As a result, the periodic input becomes an obstacle , hence, Some modified DWA techniques, have been reported to eliminate the in-band tonal behavior of the DWA, Dither [11], Rotation, RDWA [8], RnDWA [11], DIA [11] , IDWA [11,7], Bi-directional DWA (BI-DWA) [5], partial DWA [8], pseudo-DWA [11].…”

Review and advances in delta-sigma DAC error estimation based on additive noise modelling

“…Since the input to the DEM is typically the output from a DSM REQ, which has a strong noise component, tones are not as severe as for a first-order normal DSM, but they may be unacceptable. Dithering techniques to remove tones at the expense of shaping efficiency have been proposed [23].…”