×

Digital echo canceller comprising a double-talk detector

  • US 5,278,900 A
  • Filed: 04/04/1991
  • Issued: 01/11/1994
  • Est. Priority Date: 04/27/1990
  • Status: Expired due to Fees
First Claim
Patent Images

1. Digital echo canceller which comprises:

  • a receive path between a receive input and a receive output anda send path between a send input and a send output;

    combining means for forming a send output signal as the difference between the signal applied to the send input and a replica signal used for cancelling an additive echo signal at the send input that has developed in response to a receive input signal applied to the receive input;

    first transforming means for performing an N'"'"'-point Discrete Orthogonal Transform (DOT) of each block m of N'"'"' time-domain points of the receive signal;

    second transforming means for performing an N'"'"'-point DOT of each block m of N'"'"' time-domain points of the send output signal;

    third transforming means for performing an N'"'"'-point Inverse Discrete Orthogonal Transform (IDOT) of each block m of N'"'"' frequency domain points of the replica signal;

    a digital frequency-domain block-adaptive filter having a block length of N'"'"' components, in which for each signal block m a number of N'"'"' frequency-domain filter coefficients W(p;

    m) is available with p=0, 1, 2, . . . , N'"'"'-1 for generating the replica signal as an estimate of the echo signal in response to the receive input signal and the send output signal;

    adaptation means for determining for each block m adaptation components for each of the filter coefficients in response to the receive input signal and the send output signal;

    controllable gate means for each of the N'"'"' frequency domain points, operating in the frequency domain, for selectively passing the adaptation components for each frequency component in the m signal blocks to the adaptive digital filter;

    control means for determining respective levels of the send output signal and the receive input signal for generating a separate control signal for the gate means for each of the N'"'"' frequency domain points in response to the respective levels of the receive input signal and the send output signal for the individual frequency domain point concerned which control signal depends in a predetermined manner on the difference between the levels concerned, whereby the adjustment of the adaptation components for each filter coefficient is inhibited only for that frequency component representing double talk in the system.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×