Low-Frequency Equalizer Tuning for DFE Error Propagation
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Solution Overview
Problem
Error propagation in decision feedback equalizer circuits is exacerbated by large equalizer coefficients, which amplify decision errors in the comparator, particularly due to attenuation of low-frequency components by DC isolation circuits.
Innovation Solution
A low-frequency equalizer circuit is introduced to pre-compensate for attenuation, with coefficients determined by setting and iteratively adjusting gain and corner frequency to minimize the sum of absolute values of decision feedback equalizer coefficients and maximize signal-to-noise ratio, reducing error propagation risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large equalizer coefficients are used in the decision feedback equalizer circuit, then post-cursor inter-symbol interference is effectively compensated, but error propagation is amplified and decision errors in the comparator increase
Solution Approach 1:
The equalizer function is divided into two separate circuits: a low-frequency equalizer circuit that handles low-frequency components, and a decision feedback equalizer circuit that handles post-cursor inter-symbol interference. This segmentation allows each circuit to operate with optimized coefficients for its specific function, preventing error propagation while maintaining compensation effectiveness.
Solution Approach 2:
The low-frequency equalizer circuit acts as an intermediary between the DC isolation circuit and the decision feedback equalizer circuit. It pre-compensates for the attenuation caused by the DC isolation circuit, ensuring that the decision feedback equalizer receives signals with appropriate frequency content and amplitude, thereby reducing error propagation.
2Object-affected harmful factors
If DC isolation circuit is used to block DC components, then DC offset is eliminated, but low-frequency components are attenuated causing equalizer coefficient amplification
Solution Approach 1:
The low-frequency equalizer circuit performs preliminary compensation for the attenuation caused by the DC isolation circuit. By pre-adjusting the frequency response before the signal reaches the decision feedback equalizer, it ensures that low-frequency components are restored to appropriate levels without requiring large equalizer coefficients in the decision feedback path.
Data Source
AI summary
A method for determining equalizer coefficients includes the following operations: (a) setting low-frequency equalizer coefficients of a low-frequency equalizer circuit; (b) establishing a network connection via the low-frequency equalizer circuit and a decision feedback equalizer circuit, in which the decision feedback equalizer circuit operates according to an output of the low-frequency equalizer circuit; (c) recording a sum of absolute values of decision feedback equalizer coefficients of the decision feedback equalizer circuit and a signal-to-noise ratio; (d) repeatedly performing the operations (a) to (c) to obtain sums of absolute values and signal-to-noise ratios; (e) selecting a first sum of absolute values from sums of absolute values according to a predetermined threshold value and signal-to-noise ratios; and (f) setting low-frequency equalizer coefficients as a value combination corresponding to the first sum of absolute values.