Wireline Receiver EMI Cancellation via Adaptive Noise Subtraction

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Solution Overview

Problem

Wireline communication systems face challenges in mitigating electromagnetic interference (EMI) at high data rates, leading to signal degradation and safety issues, particularly in unshielded environments, where existing solutions like high-quality cables and common mode chokes are costly or ineffective, and notch filters attenuate both noise and signal.

Innovation Solution

A receiver chip with integrated EMI cancellation and monitoring circuitry that regenerates a replica of RFI noise and subtracts it from the equalizer output, eliminating the need for expensive cables and reducing signal loss, while also providing safety features by detecting EMI presence and altering system operation accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high-quality cable is used to mitigate EMC issues, then electromagnetic interference resistance is improved, but system cost increases

Engineering Contradiction:

Improveelectromagnetic interference resistanceVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts the EMI mitigation function from the cable itself and relocates it to the receiver circuitry. By using an adaptive equalizer to detect and cancel common-mode noise signals, the system removes the dependency on expensive high-quality cables while maintaining EMI resistance. The equalizer separates the desired differential signal from the unwanted common-mode EMI, allowing standard cables to be used effectively.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical/physical solution (high-quality shielded cable) with an electronic/software-based solution (adaptive equalizer with noise cancellation). The equalizer uses digital signal processing to identify and subtract EMI components from the received signal, substituting complex physical cable construction with algorithmic noise rejection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If common mode choke is used to reduce common mode signal, then EMI reduction is improved, but differential signal conversion occurs limiting effectiveness

Engineering Contradiction:

Improvecommon mode signal reductionVSAvoiddifferential signal integrity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent segments the signal processing into distinct components: the adaptive equalizer processes the differential signal while a separate noise cancellation path processes the common-mode signal. By maintaining separate processing paths, the system can reduce common-mode EMI without converting it into problematic differential signals, preserving signal integrity while achieving EMI mitigation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary adaptive equalizer that acts as a mediator between the received signal and the final decoded output. The equalizer independently processes common-mode and differential-mode components, using the common-mode signal as a reference to generate cancellation signals without allowing mode conversion that would corrupt the differential data signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If notch filter is used to attenuate RFI noise, then noise reduction is improved, but signal attenuation occurs reducing SNR

Engineering Contradiction:

ImproveRFI noise attenuationVSAvoidsignal to noise ratio

Core Design Contradiction:

Object-affected harmful factorsVSLoss of information

Solution Approach 1:

The patent converts the harmful RFI noise into a useful reference signal for cancellation. The adaptive equalizer captures the common-mode RFI signal, processes it through the noise cancellation path, and generates an inverted replica that is subtracted from the main signal. This transforms the harmful noise into a beneficial cancellation reference, reducing RFI without attenuating the desired signal and thus preserving SNR.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively mitigates EMI without additional signal loss, enhances system safety by detecting EMI presence, and reduces the need for costly shielding or external components, ensuring reliable data recovery even under high EMI conditions.

Implementation Method 1

a common mode of the two signals is generated and fed to an adaptive filter

Methodology Applied

Scientific EffectCommon mode signal filtering: Filter (electronic)

Implementation Method 2

The replica RFI is subtracted from the equalizer output prior to the data decision circuitry or slicer

Methodology Applied

Scientific EffectSignal subtraction:

Data Source

PatentUS11424776B2Electromagnetic interference cancellation for wireline receivers

Publication Date: 2022.08.23 AXONNE INC

AI summary

Embodiments of the present disclosure utilizes the natural properties of RFI noise on a wireline link. Since differential RFI noise in the system has some correlation with the common mode noise on the cable, a replica of RFI noise can be regenerated by an adaptive filter based on information about the common mode noise. The replica RFI is subtracted from the equalizer output prior to the data decision circuitry or slicer. In this method, the system does not require expensive cable, nor does the equalizer suffer additional loss due to an RFI notch filter. Since RFI can be detected and mitigated, this information can also be coupled to safety systems to increase functional safety under high EMI conditions.