Adaptive Compensation Filtering for Common-Mode Signal Reduction

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Solution Overview

Problem

Existing wired data communication systems face issues with transmitter-originated common mode signals causing electromagnetic radiation due to inherent mismatches in transmitter front-end blocks, leading to complex and costly calibration techniques and increased electromagnetic emission.

Innovation Solution

A method and apparatus that detect and adaptively filter common mode signals using a compensation filter, adjusting filter coefficients based on detected signals to reduce electromagnetic radiation without significantly increasing PHY complexity or power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If intensive calibration is performed to minimize mismatches among blocks, then manufacturing precision is improved, but device complexity increases and silicon area overhead increases

Engineering Contradiction:

Improvemismatch minimizationVSAvoidcalibration complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts the common mode signal from the differential signal path by detecting it at the termination resistor, separating the harmful component from the useful signal for independent processing and cancellation

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a compensation filter as an intermediary component that processes the detected common mode signal and generates a cancellation signal, mediating between the detected interference and the final signal output

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If common mode filter is used to attenuate common mode signal, then electromagnetic emission is reduced, but bill-of-materials cost increases due to off-chip component

Engineering Contradiction:

Improveelectromagnetic radiationVSAvoidbill-of-materials cost

Core Design Contradiction:

Object-generated harmful factorsVSEase of manufacture

Solution Approach 1:

The patent merges the common mode signal detection and cancellation functionality directly into the on-chip PHY structure, combining multiple functions (detection, filtering, cancellation) in a single integrated solution rather than using separate off-chip components

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces the physical/common mode filter hardware component with a digital signal processing-based cancellation mechanism, substituting mechanical/electrical filtering with computational filtering implemented through software or FPGA

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If on-the-fly mismatch calibration is performed, then manufacturing precision is improved, but design effort and complexity increase resulting in high cost and time-to-market

Engineering Contradiction:

Improvemismatch calibrationVSAvoiddesign complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Instead of attempting to correct the underlying mismatches in the transmitter blocks through complex calibration, the patent inverts the approach by accepting the mismatches as inherent and focusing on detecting and canceling their effects in the output signal

Inventive Principle:

Principle #13The other way round (Inversion)

4Object-generated harmful factors

If calibration is performed to reduce common mode signal, then electromagnetic emission is reduced, but loss of time increases due to calibration time

Engineering Contradiction:

Improvecommon mode signalVSAvoidcalibration time

Core Design Contradiction:

Object-generated harmful factorsVSLoss of time

Solution Approach 1:

The patent performs preliminary detection of the common mode signal characteristics during normal operation, allowing the cancellation filter to be configured in advance before the actual emission problem occurs, eliminating the need for time-consuming calibration procedures

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12519681B2Apparatus and method for reduction of common mode signal in wired data communication link

Publication Date: 2026.01.06 HUAWEI TECH CO LTD

AI summary

An apparatus for reduction of transmitter originated common mode signal in a wired data communication link includes a digital front-end configured to generate a differential transmit signal based on transmit data, and pulse-shape the differential transmit signal by a pulse-shaping filter to obtain a pulse-shaped differential transmit signal. The digital front-end includes a compensation filter configured to filter the differential transmit signal in order to reduce a common mode signal distortion. The apparatus further includes an analog front-end configured to convert the pulse-shaped differential transmit signal into an analog signal for transmission over the wired data communication link, a common mode signal detector configured to detect the common mode signal in the analog signal, and a filter coefficient determiner configured to determine filter coefficients of the compensation filter based on the detected common mode signal for common mode signal reduction and provide the filter coefficients to the compensation filter.