| 摘要 |
PURPOSE:To shorten a focussing time, by adaptively changing the correcting quantity of the tap factor of an adaptive filter in accordance with the correlative value of the code of an echo replica with the code of the difference signal between a received signal and the echo replica. CONSTITUTION:A binary data sequence from a terminal 1 is supplied to a transmitting section 3 and adaptive digital filter (ADF)6. At the transmitting section 3 the data sequence is converted into transmission line codes and sent to a two-wire transmission lien 17 through a hybrid (HYB)4. The output of a multiplier 13 is also inputted in the ADF6 and an echo replica corresponding to an echo produced at the HYB4 is generated and inputted in a subtractor 8 after D/A conversion 7. An error signal produced by subtracting the echo replica from the mixed signal of a received signal inputted through an LPF5 and the echo component of a transmitting signal is produced at the subtractor 8 and inputted in a receiving section 14 and code detector 9. Then the correlation 11 between the code detected value 10 of the echo replica and code detected value 9 of the error signal is taken and the correcting value of the tap factor of the ADF6 is updated in accordance with the correlated value during the period when transmitting signals exist only. |
