Tri-mode adaptive filter and method

A method of adaptive filtering, comprising the steps of:

• (a) providing initial adaptive filtering for an incoming signal, by one of a fast convering mode, a slow converging mode and a freezing mode;
• (b) measuring non-convergence and a near-end signal;
• (c) comparing the measured values of non-convergence and near-end signal with pre-determined threshold values;
• (d) when the near-end signal is above the corresponding threshold value and the non-convergence is below the corresponding threshold value, freezing coefficients in the currently used adaptive filtering mode;
• (e) when non-convergence is above the corresponding threshold value and the near-end signal is below the corresponding threshold value, providing adaptive filtering in accordance with a fast converging adaptive filtering mode;
• (f) when non-convergence and near-end signal are both below the corresponding threshold values, providing adaptive filtering in accordance with a slow converging adaptive filtering mode;
• and
• (g) repeating steps (b) to (f).

An adaptive filter, comprising:

• means for providing operation of the adaptive filter in one of the three modes, the modes including fast converging mode, slow converging mode, and a freezing mode;
• means for measuring non-convergence of the filter and a near-end signal, and generating a feedback signal;
• and
• means for switching between the modes of operation of the filter in response to the feedback signal.

An adaptive filter, comprising:

• first, second and third sub-filters, operable respectively in a fast convergence mode, a slow convergence mode, and a freezing mode;
• a quality detector for measuring non-convergence and a near end signal, comparing the non-convergence to a non-convergence threshold value and comparing the near end signal to a near end signal threshold value, and generating a feedback signal;
• a switching means responsive to the feedback signal to provide switching between sub-filters;
• when the non-convergence is above the corresponding threshold value and the near end signal is below the corresponding threshold value, switching to the fast converging mode;
• when the near end signal is above the corresponding threshold value and the non convergence is below the corresponding threshold value switching to the freezing mode;
• when the non-convergence and near end signal are both below the corresponding threshold values, switching to the slow converging mode;
• and when both the non-convergence and the near end signal are above the corresponding threshold values, operating the filter in any one of the sub-filters modes according to system requirements.