a conventional demodulator for digital transmission includes means for splitting the received hf signal into two identical auxiliary signals , mixers for transposing the auxiliary signals into in - phase and quadrature baseband components by multiplying them with in - phase and quadrature output signals from a local oscillator , and respective filter and amplifier means and analog - to - digital converters on the in - phase and quadrature channels . in addition , the demodulator includes estimation means suitable for estimating faults on groups of samples taken from the outputs of the analog - to - digital converters , with the faults being estimated in the form of five parameters , and correction means for correcting current samples on the basis of the parameters estimated on an earlier group of samples .