| 摘要 |
PURPOSE:To obtain a simple echo removing method reducing the scale of hardware by finding out the difference or sum between a current value and a value obtained before l.Tsec (l is a positive integer and 1/T is a data rate) as to a difference signal [=(residual echo)+(receiving signal)]. CONSTITUTION:The minimum value of propability for turning the sum between the current value and a sampled value before l.Tsec (l is a positive integer) to zero is a value except '0'. A difference signal which is the output of a subtractor 10 is supplied to a receiving part 6 and also supplied to an adder 18 and a delay element 17 for applying the delay of Tsec. The output of the delay element 17 is applied to one input of the adder 18. Therefore, the sum between the current value and the value obtained before Tsec appears in the output of the adder 18. Consequently, the probability of the precise output of the polarity of the current residual echo is detected as a certain positive value except zero by a polarity detector 12 inputting the output signal of the adder 18. Thus, the application operation of an adaptor digital filter 8 is guaranteed. |
