Cable Interface PCB Layout for Common-Mode Noise Reduction

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Solution Overview

Problem

In electronic devices with compact designs, the proximity of antenna circuits and high-speed connectors leads to challenges in reducing radio frequency interference (RFI) and electromagnetic interference (EMI), particularly due to common mode noise induced by mismatched impedances and ground level inconsistencies, which can interfere with other components and degrade performance.

Innovation Solution

The electronic device incorporates a printed circuit board with an integrated circuit, a choke module, and a compensation module, where the choke module reduces second common mode noise near the integrated circuit, and the compensation module, comprising passive components like resistors, inductors, and capacitors, is placed between the choke module and the connector to minimize first common mode noise by adjusting scattering parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the antenna circuit and high-speed connector interface are located close to each other in a compact electronic device, then the device size is reduced, but radio frequency interference and electromagnetic interference between the components increase

Engineering Contradiction:

Improvedevice sizeVSAvoidradio frequency interference and electromagnetic interference

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

A choke module is introduced as an intermediary component between the integrated circuit and the connector. The choke module includes a common mode choke that blocks common mode noise signals while allowing differential mode signals to pass through, thereby mediating the electromagnetic interaction between the IC and connector to reduce interference

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful common mode noise is extracted and removed from the signal path using the common mode choke in the choke module. The choke selectively extracts the unwanted common mode components while preserving the useful differential mode signals

Inventive Principle:

Principle #2Taking out (Extraction)

2Object-affected harmful factors

If a choke module is added between the integrated circuit and connector to reduce common mode noise, then electromagnetic interference is reduced, but device complexity increases

Engineering Contradiction:

Improvecommon mode noiseVSAvoidcircuit structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The choke module integrates multiple functions into a single compact component: the common mode choke suppresses interference, while the compensation network (comprising capacitors and resistors) corrects signal integrity issues. This merging of EMI suppression and signal compensation functions reduces the need for separate components

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The choke module serves multiple purposes simultaneously: it acts as an EMI filter, a signal integrity compensator, and an impedance matcher. The compensation network components serve dual roles in both signal conditioning and noise suppression

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If a compensation module is added between the choke module and connector to adjust S-parameter, then differential to common mode conversion is reduced, but device complexity increases

Engineering Contradiction:

Improvesignal integrityVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The compensation module adjusts the S-parameters of the interface by changing the electrical characteristics through the compensation network. Capacitors and resistors are selected with specific values to achieve desired impedance matching and minimize differential to common mode conversion at the connector interface

Inventive Principle:

Principle #35Parameter changes

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 configuration effectively reduces common mode noise, minimizing interference and improving signal integrity by compensating for impedance imbalances and differential to common mode conversions, thereby enhancing the performance of electronic devices connected via high-speed interfaces.

Implementation Method 1

The choke module is disposed on the printed circuit board and coupled between the integrated circuit and the connector

Methodology Applied

Scientific EffectElectromagnetic interference filtering: Electromagnetic Induction

Implementation Method 2

the compensation module is positioned between the choke module and the connector to further mitigate common mode noise by adjusting the S-parameter of differential to common mode conversion

Methodology Applied

Scientific EffectSignal parameter adjustment:

Data Source

PatentUS20230402793A1Electronic device with cable interface and manufacturing method thereof

Publication Date: 2023.12.14 HTC CORP

AI summary

An electronic device includes a printed circuit board, an integrated circuit, a connector, a choke module and a compensation module. The integrated circuit is disposed on the printed circuit board. The connector is disposed on the printed circuit board. The choke module is disposed on the printed circuit board and coupled between the integrated circuit and the connector. The compensation module is disposed on the printed circuit board and coupled between the choke module and the connector.