Delay compensation for analog-to-digital converter in sigma-delta modulators

A sigma-delta modulator having an input terminal and an output terminal, comprising:

• a direct chain connecting the input terminal of the modulator to the output terminal of the modulator and successively comprising an amplification unit comprising an amplification function with gain greater than unity on a predetermined frequency domain, the input terminal of the modulator being connected to a first direct input of the amplification unit, and an analog-to-digital converter;
• a feedback loop connecting the output of the analog-to-digital converter to a second inverter input of the amplification unit and comprising a digital-to-analog converter;
• and having a propagation delay between the input of the analog-to-digital converter and the output of the digital-to-analog converter;
• a subtractor located in the direct chain between the amplification unit and the analog-to-digital-converter, the output of the amplification unit being connected to a first direct input of the subtractor, an output of the subtractor being connected to the input of the analog-to-digital converter;
• a compensation filter located between the output of the subtractor and a second inverter input of the subtractor;
• and in that, when considering an impulse response of the modulator, at the output of the subtractor, to an impulse sent at the output of the subtractor, comprising a first part covering a first time interval 0;
• T with T≧Δt and a second part covering a second time interval T;
• ∝, the compensation filter is configured to contribute to the first part and the amplification unit is designed to contribute only to the second part.