Adaptive Harmonic Notching for Fast EMI Frequency Identification
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Solution Overview
Problem
Current methods for canceling electromagnetic interference (EMI) in local area networks, particularly in high-speed data transmission over twisted-pair copper cables, are inefficient due to the impracticality of prior art adaptive notch filtering techniques which require time-consuming computations, leading to potential link drops from severe EMI noise.
Innovation Solution
A cascaded-harmonic-notching circuit method that uses adaptive spectral enhancement and harmonic notching to generate a cascaded-harmonic-notched signal, which is then used as an error input for an adaptation circuit to identify the fundamental frequency, improving convergence speed and effectiveness in filtering EMI noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior art adaptive notch filtering techniques are used to cancel EMI, then EMI cancellation is achieved, but computation time is excessive causing link drops
Solution Approach 1:
The patent segments the EMI cancellation process into multiple parallel notching circuits, each handling a specific frequency component (fundamental and harmonic). This parallel segmentation allows simultaneous processing of different frequency components, dramatically reducing total computation time compared to sequential processing while maintaining effective EMI cancellation across the full spectrum.
Solution Approach 2:
The patent applies partial action by implementing notching circuits for only the most significant frequency components (fundamental and selected harmonics) rather than processing the entire spectrum. This selective approach reduces computation time while still achieving sufficient EMI cancellation to prevent link drops, trading complete spectral processing for timely intervention.
2Reliability
If traditional adaptive notch filtering is used, then EMI cancellation is provided, but convergence speed is slow leading to delayed response
Solution Approach 1:
The patent divides the adaptive filtering task into multiple parallel notching circuits, each independently adapting to its assigned frequency component. This segmentation enables simultaneous convergence on multiple frequency components rather than sequential adaptation, significantly accelerating overall convergence speed while maintaining effective EMI cancellation across all targeted frequencies.
Solution Approach 2:
The patent implements preliminary action by using fixed notching circuits with predetermined center frequencies corresponding to expected EMI harmonics. These circuits are pre-configured to target likely interference frequencies, allowing immediate filtering action without waiting for full adaptive convergence, thereby speeding up the initial response while adaptation fine-tunes performance over time.
3Object-affected harmful factors
If comprehensive spectral filtering is applied, then all EMI components are removed, but device complexity increases
Solution Approach 1:
The patent applies partial action by implementing notching circuits for only the fundamental frequency and selected harmonic components rather than covering the entire spectral range. This selective filtering removes the most problematic EMI components while avoiding the complexity of comprehensive full-spectrum filtering, achieving practical EMI cancellation with manageable device complexity.
Solution Approach 2:
The patent implements universality by designing notching circuits that can be configured to target multiple frequency components (fundamental and various harmonics) using a standardized circuit architecture. This multi-functional approach allows a single circuit design to handle diverse EMI scenarios across different frequency ranges, reducing overall system complexity compared to designing separate specialized circuits for each frequency component.
Data Source
AI summary
A circuit and method perform adaptive spectral enhancement at a frequency ω1 (also called “fundamental” frequency) on an input signal y which includes electromagnetic interference (EMI) at an unknown frequency, to generate a fundamental-enhanced signal φ1 (or its complement). The fundamental-enhanced signal φ1 (or complement) is thereafter used in a notching circuit (also called “fundamental notching” circuit) to generate a fundamental-notched signal y−φ1. The fundamental-notched signal y−φ1 is itself enhanced to generate a harmonic-enhanced signal φ2 that is used to notch the fundamental-notched signal y−φ1 again, in one or more additional notching circuits that are connected in series with the fundamental notching circuit. The result (“cascaded-harmonic-notched” signal) is relatively free of EMI noise (fundamental and harmonics), and is used as an error signal for an adaptation circuit that in turn identifies the fundamental frequency ω1. Use of a cascaded-harmonic-notched signal as the error signal improves speed of convergence of adaptation.