Circuit arrangement for adaptive echo cancellation in terminals for duplex transmission

摘要

The invention relates to a circuit arrangement for adaptive echo cancellation in terminals for duplex transmission by obtaining an echo cancellation signal (ê) from a transmit signal (xA) by means of a first (AF) and a second (F) filter, the first filter being designed as an adaptive transverse filter and the second filter being connected downstream of the first. If a relatively long echo is intended to be completely cancelled with an echo canceller comprising a single adaptive transverse filter, this filter must have an economically unviable number of elements. It is known for the transverse filter to be equipped with fewer elements than are needed for complete echo cancellation. Only part of the echo is thereby cancelled. A second filter is connected downstream of the transverse filter to cancel the echo end which thus remains. According to the invention, the second filter (F) is operated non-adaptively and is connected downstream of the first filter in such a way that the output of the last multiplier (Mn) of the first filter (AF) is connected to the input of the second filter (F) (Fig. 1). <IMAGE>