| 摘要 |
PURPOSE:To reduce the disorder of the echo path estimation of an echo canceler by monitoring the instantaneous value of a residual signal and detecting a double talk due to the power ratio of a receive and an echo signal in combination. CONSTITUTION:The residual signal e(k) is made into ¦e(k)¦ by an absolute value circuit 501 and compared by a comparator 502 with the upper limit LS of the residual signal during predetermined convergence, and logic ''1'' is obtained when the residual signal exceeds the upper limit. Inverters 507-510 output ''1'' when a double talk occurs, so the output pulse of the comparator 502 is obtained at the output of an AND gate 503. A monostable MV504 generates pulses with width T*. The pulses become pulses for compensating the detection time delay of a double talk detection circuit due to the power ratio detection and are inputted to an OR circuit 511, which generates an output (INH) as a new double talk signal to inhibit the echo path estimation of the echo canceler. The monostable MV504 generates the pulses with width T* even at the time of circuit variation. At this time, there is no double talk, so the inverter 510 outputs ''1'' and pulses with width T# are outputted. |
