Adaptive Nonlinear Filter for Signal Equalization
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Solution Overview
Problem
High-speed serial transmissions in communication systems suffer from inter-symbol interference (ISI) and nonlinearities introduced by system components, which distort signals and limit the effectiveness of equalization circuitry, making it challenging to accurately detect data symbols.
Innovation Solution
An adaptive nonlinear filter is implemented in the data receiver, which generates a linearized signal by dynamically adjusting its transfer function based on error signals from equalization circuitry, using multipliers and filter taps to produce polynomial signals and adjust scalar quantities, thereby counteracting nonlinearities and filtering ISI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equalization circuitry is used to filter inter-symbol interference, then signal quality is improved, but nonlinearity in the received signal reduces the effectiveness of equalization
Solution Approach 1:
The patent applies preliminary action by introducing a nonlinearity compensation filter before the equalization circuitry. This filter pre-processes the received signal to compensate for nonlinearities introduced by system components (VGA, AGC, transmitter, channel) before the signal reaches the equalizer, thereby improving the equalizer's effectiveness and overall signal quality
Solution Approach 2:
The nonlinearity compensation filter acts as an intermediary component between the communication channel and the equalization circuitry. It mediates the signal by transforming the nonlinear received signal into a more linear form that is more suitable for subsequent equalization processing, thus bridging the gap between the distorted input and the equalization requirements
2Productivity
If system components (VGA, AGC, transmitter) are used to process signals, then signal processing functionality is improved, but nonlinearities are introduced that distort the voltage relationship
Solution Approach 1:
The patent converts the harmful nonlinear distortion into a benefit by designing a nonlinearity compensation filter with transfer function H(x) that intentionally introduces a complementary nonlinearity to cancel out the system-induced nonlinearity. The filter uses polynomial expansion and adaptive coefficients to transform the distorted signal back toward linearity, turning the problem of nonlinearity into a solution mechanism
3Speed
If high-speed serial transmission is used, then data transmission speed is improved, but inter-symbol interference and signal distortion increase
Solution Approach 1:
The nonlinearity compensation filter performs preliminary signal conditioning before equalization, pre-compensating for distortions that would otherwise require more aggressive equalization processing. This allows the system to maintain high transmission speeds while reducing the burden on the equalizer and improving overall signal integrity
Solution Approach 2:
The patent employs adaptive feedback mechanisms where the filter coefficients are dynamically adjusted based on the received signal characteristics and error signals from the equalization process. This feedback loop continuously optimizes the nonlinearity compensation to match the actual system conditions, improving performance at high transmission speeds
Data Source
AI summary
An equalizer circuit including a filter, equalization circuitry, and a filter adaptation circuit. The filter is configured to produce a linearized signal based at least in part on a received input signal and a nonlinear transfer function. The equalization circuitry is configured to filter inter-symbol interference (ISI) and detect one or more data symbols in the linearized signal. The equalization circuitry is further configured to produce an error signal indicating an amount of error in the detected data symbols. The filter adaptation circuit is configured to dynamically adjust the nonlinear transfer function of the filter based at least in part on the error signal from the equalization circuitry.