DFE and FFE Narrowband Notch Filter for EMI Cancellation
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Solution Overview
Problem
Conventional decision feedback equalization (DFE) systems suffer from error propagation and increased complexity when attempting to cancel electromagnetic interference (EMI) in data communication systems, leading to bursts of errors and higher power usage.
Innovation Solution
Implementing a combination of decision feedback equalization (DFE) and feed-forward equalization (FFE) as a narrowband notch filter, along with fractionally-spaced equalizers and Tomlinson-Harashima precoding, to effectively cancel EMI while mitigating error propagation through filter optimization engines and algorithms like LMS or MMSE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional decision feedback equalization (DFE) is used to cancel electromagnetic interference (EMI), then EMI cancellation capability is improved, but error propagation and device complexity increase
Solution Approach 1:
The equalization system is segmented into multiple independent filter banks, each handling specific frequency bands or interference components. This segmentation allows the system to target EMI cancellation in specific bands without requiring complex full-band processing, thereby reducing overall system complexity while maintaining effective EMI cancellation capability.
Solution Approach 2:
An intermediary processing stage is introduced between the received signal and the final decision output. This intermediary stage includes preprocessing filters and selective equalization paths that simplify the main DFE processing by pre-conditioning the signal, reducing the computational burden and complexity of the core equalization algorithm.
2Object-affected harmful factors
If stronger DFE coefficients are used to improve EMI cancellation, then EMI suppression is improved, but error propagation increases
Solution Approach 1:
Different filter coefficients and equalization strengths are applied to different frequency bands or signal components based on local interference characteristics. Rather than using uniformly strong coefficients across all bands, the system applies targeted coefficient adjustments only where EMI is present, achieving effective suppression while minimizing error propagation in clean signal bands.
Solution Approach 2:
The system applies partial equalization action by selectively processing only the portions of the signal contaminated by EMI, rather than applying full-strength equalization to the entire signal. This partial action approach achieves sufficient EMI suppression in affected bands while avoiding the excessive processing that would amplify errors in unaffected bands.
3Object-affected harmful factors
If longer DFE filter length is used to enhance EMI cancellation, then EMI removal is improved, but implementation complexity and power usage increase
Solution Approach 1:
The long filter is segmented into multiple shorter filter banks, each processing specific time delays or frequency ranges. This segmentation achieves the equivalent of a long filter for EMI removal while implementing multiple manageable short filters that are computationally more efficient and easier to optimize individually.
Solution Approach 2:
Rather than implementing a uniformly long filter across all signal components, the system uses partial filtering action with varying filter lengths adapted to local interference characteristics. Shorter filters are used where minimal EMI is present, while longer effective filtering is applied only where needed, reducing overall implementation complexity and power consumption.
Data Source
AI summary
Various embodiments described herein provide for data communications using decision feedback equalization (DFE) for electro-magnetic interference (EMI) cancellation in a received signal, such as a signal received over a data communication medium and at a receiver of a communication system. In particular, some embodiments use a DFE and a feed-forward equalizer (FFE) to equalize a signal received by a first physical layer device from a second physical layer device over a data communication medium, and to operate as a narrowband notch filter to cancel EMI from the received signal.