Title :
An approach to tackle quantization noise folding in double-sampling ΣΔ modulation A/D converters
Author :
Rombouts, Pieter ; Raman, Johan ; Weyten, Ludo
Author_Institution :
Electron. & Inf. Syst. Lab., Ghent Univ., Gent, Belgium
fDate :
4/1/2003 12:00:00 AM
Abstract :
ΣΔ-modulation is a proven method to realize high- and very high-resolution analog-to-digital converters. A particularly efficient way to implement such a modulator uses double-sampling where the circuit operates during both clock phases of the master-clock. Hence, the sampling frequency is twice the master-clock frequency. Unfortunately, path mismatch between both sampling branches causes a part of the quantization noise to fold from the Nyquist frequency back in the signal band. Therefore, the performance is severely degraded. In this paper, we show that the problem is reduced but not eliminated by employing multibit quantization. Next, we present an in-depth solution for the problem. The approach consists of modifying the quantization noise transfer function of the overall modulator to have one or several zeros at the Nyquist frequency. This way the effect of noise folding can nearly be eliminated. It is shown that this can be implemented by a simple modification of one of the integrators of the overall modulator circuit. Finally, several design examples of single-bit and multibit modulators are discussed.
Keywords :
integrated circuit noise; integrating circuits; quantisation (signal); sigma-delta modulation; transfer functions; A/D converters; Nyquist frequency; clock phases; double-sampling ΣΔ modulation; integrators; multibit modulators; multibit quantization; path mismatch; quantization noise folding; sampling frequency; single-bit modulators; transfer function; Analog-digital conversion; Capacitors; Circuit noise; Clocks; Delta modulation; Feedback; Frequency; Quantization; Sampling methods; Transfer functions;
Journal_Title :
Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on
DOI :
10.1109/TCSII.2003.810485