A sigma-delta modulator having a propagation delay &Dgr;t between an input of an analog-to-digital converter and an output of the digital-to-analog converter. A subtractor is located in a direct chain between an amplification unit and the analog-to-direct converter. The output of the amplification unit is connected to a first direct input of the subtractor. An output of the subtractor is connected to the input of the analog-to-digital convertor. The modulator also includes a compensation filter located between the output of the subtractor and a second inverter input of the subtractor. When considering an impulse response of the modulator, at the output of the subtractor, to an impulse sent at the output of the subtractor, including a first part covering a first time interval 0; T with T≧&Dgr;t, and a second part covering a second time interval T; ∝, the compensation filter is designed to contribute to the first part and the amplification unit is designed to contribute only to the second part. Such a sigma-delta modulator may be used in a radar processing chain.