| 摘要 |
<p>Apparatus for reducing the risk of undesirable drifting of the parameters, so-called bursting, of an adaptive echo filter (15), which is coupled between a receiving branch (17) and a transmitting branch (16) included in a four-wire loop. A difference signal (E) which contains no echo from the receiving branch is generated in the transmitting branch in a known manner. The apparatus includes an adaptive filter (25) which is coupled between the transmitting branch and the receiving branch and which functions to generate a compensation signal from the difference signal (E) when transmitting narrowband signals from a near-end. The compensating signal is subtracted from a signal which appears in the receiving branch (17) and the filter is updated in a manner to minimize the correlation between the difference signal (E) and the input signal (X') of the echo filter. A relatively small filter (25) is sufficient to essentially eliminate this correlation when transmitting signals which, at maximum, consist of some few single sinusoidal tones.</p> |
