Method and circuit arrangement for adaptive equalisation and adaptive echo cancellation in terminals for duplex transmission

摘要

The invention relates to a method and a circuit arrangement for adaptive equalisation and adaptive echo cancellation in terminals for duplex transmission. Methods and circuit arrangements of this type are used in electrical communication systems in the interface from a four-wire to a two-wire line via a hybrid circuit (G). Echo signals (e) and signal distortion occur due to shortcomings in the transmission paths (Ü). Cancellation of the echo signals is attempted by means of an adaptive echo canceller. The transmit signal (xA) is fed to a variable filter (VF). This filter delivers an echo cancellation signal (eL) at its output. The cancelled receive signal (xB + eR) is first fed via a changeover switch (U) to the variable filter (VF) as an error signal (fs), followed by the discriminator error signal (fE) once the changeover switch has been actuated. The variable filter (VF) coefficient calculation is carried out with a variable adjustment parameter (a) and is designed in such a way that the error signal (fs) is minimised via the echo cancellation signal (eL). This minimum must be reached within a defined short time. To achieve the high convergence speed required for this purpose, the invention describes an advantageous derivation of the variable adjustment parameter (a) and of a changeover signal (aU). <IMAGE>