Nonlinear Filter Coefficient Selection for Transceiver Distortion Cancellation
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Solution Overview
Problem
High-speed Ethernet networks face signal distortion due to non-linearities introduced by transmitter and echo signal processing, which are not effectively addressed by existing methods, leading to reduced performance in full-duplex transmission.
Innovation Solution
A method for selecting coefficients of a non-linear filter that generates a replica signal to cancel non-linear components in the receive signal, using periodic test patterns to determine coefficients for the filter, which reduces distortion by combining the replica signal with the received signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If full duplex transmission is implemented to increase data transmission speed, then network bandwidth is improved, but non-linear distortion in receive signals increases due to transmit signal coupling and echo cancellation
Solution Approach 1:
The patent applies preliminary anti-action by generating a non-linear replica signal that anticipates and counteracts the non-linear distortion before it degrades the receive signal. The replica signal is created by processing the transmit signal through a non-linear filter with coefficients derived from periodic test patterns, then subtracting this replica from the receive signal to prevent distortion accumulation.
Solution Approach 2:
The patent converts the harmful non-linear distortion into a beneficial cancellation process. By intentionally generating a replica of the non-linear distortion components through the non-linear filter and periodic test patterns, the system creates a signal that can be subtracted from the receive signal, thereby transforming the harmful distortion into a useful cancellation mechanism.
2Object-affected harmful factors
If echo signal cancellation is applied to reduce transmit signal coupling, then receive signal quality is improved, but non-linearities are introduced by the cancellation process itself
Solution Approach 1:
The patent introduces an intermediary non-linear filter that mediates between the echo cancellation process and the final receive signal. This filter, with coefficients determined by periodic test patterns, generates a non-linear replica signal that accounts for the non-linearities introduced during echo cancellation, allowing for more accurate distortion compensation without introducing additional harmful non-linearities.
3Measurement precision
If non-linear filter coefficients are optimized to reduce distortion, then receive signal fidelity is improved, but system complexity increases due to coefficient selection process
Solution Approach 1:
The patent employs periodic action by using periodic test patterns to determine the non-linear filter coefficients. These periodic patterns are applied to the transmit signal, and the resulting receive signals are analyzed to extract optimal coefficient values. This periodic approach simplifies the coefficient selection process compared to continuous optimization, while still achieving high receive signal fidelity.
Data Source
AI summary
Embodiments of a method and apparatus for selecting coefficients of a non-linear filter are disclosed. The non-linear filter receives a transmit signal and generates a non-linear replica signal of a transmit DAC of a transceiver. The method include applying a plurality of periodic test pattern signals to inputs of the transmit DAC, wherein the periodic test pattern signals include a stream of symbols. Receive symbols are collected at an output of a receiver ADC of the transceiver resulting from the plurality of periodic test pattern signals. A non-linear map is generated that provides a value for each of n consecutive symbols input to the transmit DAC. Coefficients of the non-linear filter are selected based on the non-linear map.