Robust adaptive filter for echo cancellation
AssigneeAcoustic Technologies, Inc.
InventorsCharles Anthony Lipari, II, Alexander Volkov
Life of this patent
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Abstract
An adaptive filter is programmed with an algorithm based on a normalized Least Mean Squares (nLMS) algorithm that adapts each sample time. The algorithm is modified to be more efficient in a variety of DSPs by computing multiple errors, one per sample, before updating coefficients. The update equation utilizes the multiple errors to achieve adaptation at a similar performance to known nLMS algorithms that adapt each sample time but without the instability that is observed in low echo-to-near-end-noise ratio (ENR) input conditions. Varying the relaxation step size prevents divergence. The DSP utilizes either one or more MAC units.
Claims10
In a telephone including an audio frequency circuit having a transmit channel, a receive channel, and at least one echo canceling circuit coupled between said channels, the improvement comprising:
- an adaptive filter in said echo canceling circuit;
- and
- a coefficient update circuit coupled to said adaptive filter for modifying the coefficients in said adaptive filter in steps in response to an error signal and in accordance with a multiple error per sample over plural samples, least mean squares algorithm for reducing said error signal.
A method for reducing echo in a telephone, said method comprising the steps of:
- filtering a first signal with a filter having adaptive coefficients;
- detecting an error signal based on a difference between the filtered first signal and a second signal;
- and
- modifying the adaptive coefficients in steps in response to the error signal and in accordance with a multiple error per sample over plural samples, least mean squares algorithm.
Dependencies are inferred from the claim text.