Nova Patents
EP0803990A2

Echo canceller with double talk detector

Abstract

The echo canceller of the present invention comprises a means for estimating an echo gain from a reception signal level and a transmission signal level; a first level calculating means (5) for calculating logarithmically converted power of a reception signal level; a second level calculating means (16) for calculating logarithmically converted power of a transmission signal level; an echo gain estimation means (19) for estimating an echo gain based on the reception signal level and the transmission signal level; and an echo level estimating means (18) for adding the estimated echo gain to said reception signal level to obtain an estimated echo level, a third level calculating means (6) for calculating logarithmically converted power of a residual signal level; and a comparison means (19) for comparing the estimated echo level with the residual signal level after the echo cancellation; wherein the echo of the reception signal contained in the transmission signal is canceled when said estimated echo level exceeds the value obtained by adding a margin to the residual signal level.

EP0803990A2, drawing sheet 1
Sheet 1 of 97

Term

Term ended

Projected expiry passed 30 January 2017, 9.6 years ago.

  1. Priority
  2. Filed
  3. Published
  4. Projected expiry
  5. Today

14 claims: 2 independent, 12 dependent

  1. 1
    An echo canceller including an echo level estimating means in an adaptation control means, the echo level estimating means comprising:a first level calculating means (5) for calculating logarithmically converted power of a reception signal level;a second level calculating means (16) for calculating logarithmically converted power of a transmission signal level;an echo gain estimation means (17) for estimating an echo gain based on the reception signal level and the transmission signal level;and an echo level estimating means (18) for adding the estimated echo gain to the reception signal level to obtain an estimated echo level.
  2. 8
    An echo canceller comprising:an adaptive memory (10) for storing a first filter coefficient for adaptation which is updated from a transmission signal and a residual signal after echo cancellation, a refuge memory (13) for storing a second filter coefficient in the adaptive memory in parallel for predetermined sections while the adaptation is judged to be proper;a coefficient substitution means (15) for controlling whether the filter coefficient for the adaptation of the adaptive filter is needed to be updated or not according to the difference between the transmission signal and the residual signal level;an interpolating means (23) for interpolating after comparing the value of the first filter coefficient in the adaptive memory with the value of the second filter coefficient in the refuge memory;a filter coefficient updator (14) for updating the first filter coefficient of the adaptive memory according to the transmission signal and the residual signal;a sum/ product calculator (11) for generating a pseudo echo signal by carrying out the convolution operation according to the reception signal and the first filter coefficient stored in the adaptive memory;and an echo subtracter (2) for subtracting the pseudo echo signal from the transmission signal to generate a residual signal;wherein, when said coefficient substitution mean controls to substitute the value of the first filter coefficient by the value of the second filter coefficient in case that the adaptation is not proper, and said interpolation means carries out interpolation and updates for a predetermined timing number so that the value of the first filter coefficient is continuous to the value of the second filter coefficient.
Independent claims2