Echo Canceling System With Fixed Conditioning Filter
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Solution Overview
Problem
Current echo cancellation systems face challenges in effectively addressing impedance mismatch issues between four-wire and two-wire circuits, leading to intrusive echoes, especially when network delays exceed 36 ms, and require subjective manual adjustments that are time-consuming and inefficient.
Innovation Solution
An echo canceling system comprising a fixed echo conditioning filter and an adaptive filter, where the fixed filter uses a measured impulse response to cancel the constant echo path, while the adaptive filter handles the varying echo path, with a gain pad to enhance signal boosting and double talk decision-making.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hybrid is used to couple four-wire and two-wire circuits, then cost and cabling requirements are reduced, but impedance mismatch occurs causing echo
Solution Approach 1:
The patent converts the harmful echo caused by impedance mismatch into a beneficial effect by using the reflected signal to train an adaptive filter. The adaptive filter learns the echo characteristics from the reflected signal and generates an anti-echo signal that cancels the harmful echo, thereby transforming the harmful reflection into a useful training opportunity for echo cancellation.
Solution Approach 2:
The patent implements feedback by continuously monitoring the echo signal and using it to adjust the adaptive filter coefficients. The adaptive filter processes the reflected signal through iterative optimization (such as LMS or NLMS algorithms) to converge on the optimal filter coefficients that minimize echo, creating a closed-loop feedback system that dynamically adapts to changing impedance conditions.
2Reliability
If manual impedance matching is performed, then echo suppression is improved, but human effort and time consumption increase
Solution Approach 1:
The patent implements self-service by enabling the system to automatically adjust its own impedance matching parameters through adaptive filtering. The system monitors echo levels and autonomously modifies filter coefficients without human intervention, performing self-optimization to achieve optimal echo suppression while eliminating the need for manual adjustment and reducing time loss.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting filter coefficients and adaptation parameters in response to changing network conditions. The adaptive filter continuously modifies its internal parameters (such as filter coefficients and step-size parameters) to optimize echo cancellation performance under varying impedance conditions, replacing manual parameter adjustment with automated adaptive parameter modification.
3Reliability
If echo cancellation is applied to both constant and varying echo paths, then overall echo suppression is improved, but system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the echo cancellation task into separate functional components: a fixed filter for handling constant echo paths and an adaptive filter for handling varying echo paths. This segmentation allows each component to specialize in specific aspects of echo cancellation, improving overall effectiveness while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
The patent implements dynamics by using an adaptive filter that can dynamically adjust its coefficients in response to changing network conditions. The adaptive filter transitions from a static fixed filter to a dynamic system that automatically adapts to varying impedance conditions, network delays, and echo characteristics, enabling the system to handle both constant and varying echo paths effectively through adaptive parameter modification.
Data Source
AI summary
An echo canceling system has an adaptive filter connected to an echo source, for canceling echo from an echo path. A fixed echo conditioning filter is connected in series with the adaptive filter, intermediate the echo source and the adaptive filter. The fixed echo conditioning filter cancels the constant part of the echo path using a measured impulse response of the echo path.