US 6,271,782 B1 · Delta-sigma A/D converter

Abstract

A delta-sigma modulator comprising a first quantizer providing a first digital signal d0(k) representing the input signal g(t); a loop filter with input signal paths; a loop quantizer providing a corrective digital signal d1(k) representing the loop filter's output signal y(t); an array of feedback DACs D/A converting the sum d(k)=df(k)=d0(k)+d1(k) of the first and the corrective digital signals and injecting feedback signals into the loop filter. The loop filter's input node is applied the difference of the input signal g(t) and the global analog feedback signal a3(t). The global feedback signal a3(t) is delayed several clock cycles with respect to the digital output signal d(k). The delay is used to carry out mismatch-shaping and deglitching algorithms in the feedback DACs. The feedback DACs' different delays and gain coefficients are designed such that the modulator is stable. The filter's input signal paths and the compensating DAC are designed such that the gain from the input signal g(t) to the loop quantizer is small, ideally zero. Thus, the loop quantizer's resolving range can be a fraction of the first quantizer's resolving range, whereby the output signal's d(k) resolution can be much higher than the individual resolutions of d0(k) and d1(k). The delta-sigma modulator is well suited for the implementation of high-resolution wide-bandwidth A/D converters. Important applications include digital communication systems.

Claims53

Dependent claims

An oversampled analog-to-digital converter receiving an analog input signal and providing a digital output signal comprising:

(a) a first quantizer receiving said analog input signal and providing a first digital signal;
(b) a loop quantizer receiving an analog compensation signal and providing a digital compensation signal;
(c) a digital circuit combining said first digital signal and said digital compensation signal to produce said digital output signal;
(d) a residue circuit providing an analog residue signal as the difference of a function of said analog input signal and a main analog feedback signal representing said digital output signal;
(e) an amplifying circuit receiving at least said analog residue signal and providing said analog compensation signal.

2 more elements

An oversampled analog-to-digital converter receiving an analog input signal and providing a multibit digital output signal comprising:

(a) a main digital-to-analog converter providing a main analog feedback signal representing said digital output signal;
(b) a residue circuit receiving said analog input signal and said main analog feedback signal and providing an analog residue signal;
(c) amplifying means receiving said analog residue signal and a secondary analog feedback signal and providing an analog compensation signal;
(d) a quantizer circuit receiving at least said analog compensation signal and providing at least said digital output signal;
an origin in time being defined as when said quantizer circuit effectively samples said analog compensation signal;
a first feedback signal component being obtained by sampling said analog compensation signal at and periodically with respect to said origin in time;
(e) a feedback circuit generating said secondary analog feedback signal comprising said first feedback signal component delayed by a first number of clock cycles;
said main analog feedback signal comprising said first feedback signal component delayed by a second number of clock cycles;
said second number of clock cycles being at least one higher than said first number of clock cycles.

6 more elements

A method for converting an analog input signal into a digital output signal comprising the steps of:

(a) generating a first digital signal representing said analog input signal;
(b) generating a second digital signal representing an analog compensation signal;
(c) combining said first digital signal and said second digital signal to produce said digital output signal;
(d) generating a main analog feedback signal representing a combination of said first digital signal and said second digital signal;
(e) generating a main analog residue signal by subtracting said main analog feedback signal from a function of said analog input signal;
(f) generating said analog compensation signal partially by amplifying said main analog residue signal.

3 more elements

Dependencies are inferred from the claim text.

Delta-sigma A/D converter

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Delta-sigma A/D converter

Life of this patent

Abstract

Claims53