Echo Cancellation Adaptation Gating for Full Duplex Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Full duplex communication circuits face challenges in echo cancellation due to undesirable echoes from transmitted signals, particularly when unobservable modes in the transfer function lead to impaired echo cancelation performance and signal saturation.
Innovation Solution
A mode cancelation circuit with an adaptation gating mechanism that detects notches in the transfer function, specifically at the Nyquist frequency, to selectively remove the contribution of the received signal from the echo cancelation signal, thereby improving echo removal and preventing signal saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If echo cancelation is performed using full duplex communication circuits, then transmitted signals can be sent and received simultaneously, but echo interference from transmitted signals degrades received signal quality
Solution Approach 1:
The patent uses the transmitted signal itself (the harmful echo source) to generate the echo cancelation signal. By processing the transmitted signal through the same transmission medium and combining it with received signals, the system creates an accurate echo model that can be subtracted from the received signal, converting the harmful echo into a useful cancelation reference.
Solution Approach 2:
The patent introduces an intermediary processing path that includes transmission path simulation, signal combination, and adaptive filtering. This intermediary system models the echo path and generates cancelation signals that mediate between the transmitted and received signals, effectively removing echo interference without directly modifying the original communication signals.
2Measurement precision
If adaptive filtering is used for echo cancelation, then echo removal performance improves, but unobservable modes in the transfer function cause signal saturation and impair performance
Solution Approach 1:
The patent performs preliminary detection of unobservable modes in the transfer function before adaptive filtering is applied. By identifying notches or regions of low gain in the transfer function ahead of time, the system can take preventive actions such as adjusting filter coefficients, scaling signals, or disabling adaptation in those frequency regions, thereby preventing signal saturation before it occurs.
Solution Approach 2:
The patent implements feedback mechanisms that continuously monitor the transfer function characteristics and adaptive filter output. When unobservable modes are detected or signal saturation is approaching, the system adjusts the adaptive filtering parameters in real-time, creating a closed-loop control system that maintains stable operation while preserving echo cancelation performance.
Data Source
AI summary
Methods and apparatus for echo cancelation in full duplex communication systems are disclosed. An example method includes generating data for transmission from the first communication device, generating a transmission signal based on the data for transmission, generating an echo cancelation signal based at least in part on the data for transmission and a received signal from a second communication device, and selectively removing a contribution of the received signal to the echo cancelation signal.