Analogue-digital echo canceller based on the DAFIC building block

An echo canceller architecture in which the filtering function is performed in a mixed analog-digital mode together with the D/A (digital-to-analog) conversion is described. Adaptation of such architecture is based on the three-steps fast-sign algorithm, a proposed improved extension of the sign algorithm that yields faster convergence. A design example of a 10-tap echo canceller where, according to functional simulation results, a minimum attenuation of 40 dB is reached in less than 25000 iterations is given