Echo Cancellation via K-Path Pre-Distortion and Minimum Fusion
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Solution Overview
Problem
In audio systems, especially handheld devices, acoustic echo cancellation is challenging due to nonlinearities and distortions caused by small micro speakers, leading to unstable echo cancellation and reduced audio quality.
Innovation Solution
A method and apparatus that perform K-path amplification and pre-distortion on downlink reference signals, followed by filtering using self-adaptive filters, and minimum-value fusion to achieve high-amplitude echo loss, effectively addressing the distortion and instability in echo cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-adaptive filter is used for echo cancellation in handheld devices, then echo cancellation is achieved, but the cancellation becomes unstable and echo loss is very small due to nonlinear distortion from small micro speakers
Solution Approach 1:
The patent applies pre-distortion processing to the reference signal before it enters the self-adaptive filter. This preliminary action compensates for the nonlinear distortion that will occur in the acoustic echo path, allowing the filter to work with a pre-corrected signal and achieve stable cancellation with higher echo loss.
Solution Approach 2:
The patent transforms the reference signal through nonlinear pre-distortion functions that modify its parameters (amplitude, phase) in advance. This parameter transformation compensates for the expected distortion in the acoustic path, enabling the self-adaptive filter to achieve better performance despite the small speaker's nonlinear characteristics.
2Volume of moving object
If the micro speaker works in a nonlinear region to satisfy volume requirements, then compact size is achieved, but audio distortion becomes more serious and echo cancellation performance deteriorates
Solution Approach 1:
The patent converts the harmful nonlinear distortion produced by the small micro speaker into a beneficial effect by applying pre-distortion. The pre-distortion function intentionally introduces the opposite distortion to cancel out the speaker's nonlinearities, turning the distortion problem into a solution that enables compact device design while maintaining audio fidelity.
Data Source
AI summary
Method and apparatus for reducing distortion echo are provided. K-path amplification and pre-distortion process are performed to the downlink reference signal to obtain K-path pre-distorted signals. Afterwards, filtering is performed using the self-adaptive filters which correspond to the downlink reference signal x(t) and the K-path pre-distorted signals to obtain the filtering signals. Error signals are obtained by calculating differences between the target signal and each of the filtering signals. The minimum-value fusion process is performed to the error signals to obtain the residual signal which is then output as the final self-adaptive echo cancellation. In embodiments of the present disclosure, the residual signal is relatively small as the minimum-value fusion process is performed to the error signals. That is to say, echo loss is relatively great. Therefore, the method may provide echo loss with high amplitude under a situation that a speaker has relatively serious distortion.