Method of adaptively adjusting the coefficients of a digital filter in an echo canceller

US6041290A · kind A · utility

Assignee

• ALCATEL · FR

Inventors

• Hans Jurgen Matt · Waiblingen, DE
• Michael D. Walker · San Francisco, US
• Uwe Ackermann · Delbrück, DE

Key dates

• Filing date: Nov 13, 1997
• Grant date: Mar 21, 2000
• Expiry date: Nov 13, 2017

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04M9/082
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

Digital filters are used to compensate for echoes in a transmission system in which unwanted couplings occur between a signal value in the receiving direction and a signal value in the transmitting direction. The correct adjustment of the filter coefficients has a considerable influence on the achievable echo compensation. Disturbance signals such as background noises, nonlinear effects in A/D converters or an active local speaker can briefly change the adjustment of the filter coefficients in a way so that the digital filter does not compensate for the echoes and causes additional echoes in unfavorable cases. In accordance with the invention a set of filter coefficients (C(j)) are weighted with an envelope curve (H(j)) and an error measurement (F(j)) is determined therefrom. Depending on the magnitude of the error measurement (F(j)), the filter coefficients (ci) are used for further processing or are discarded. The pertinent arrangement comprises a first digital filter (1) for which the filter coefficients (ci) are continuously calculated in accordance with the NLMS algorithm. These filter coefficients (ci) are stored, weighted and the best values are used to adjust a second digit…