Band-Stop Filtering of Baseband Signals to Suppress Terminal EMI

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Solution Overview

Problem

Existing solutions for reducing interference signals in terminal devices, such as conductive cloth or copper sheets, degrade over time and fail to effectively shield interference, leading to continued radiation and conduction-based interference issues.

Innovation Solution

A band-stop filter is electrically connected to the interference source and grounded, specifically designed to filter baseband signals, including clock signals and display or camera signals, using inductors and capacitors to attenuate low-frequency harmonic components and effectively reduce interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conductive cloth or copper sheets are used to shield interference signals, then initial shielding effect is achieved, but shielding performance degrades over time and fails to effectively reduce interference

Engineering Contradiction:

Improveinterference signal radiationVSAvoidshielding effect durability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent changes the fundamental parameter of interference suppression from passive conductive shielding to active signal filtering. The band-stop filter modifies the electrical characteristics of the interference signal by targeting specific frequency ranges, transforming the approach from physical barrier to spectral selection. This resolves the durability issue because electronic filtering does not degrade like conductive materials do over time.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/physical shielding system (conductive cloth or copper sheets) with an electronic signal processing system (band-stop filter). Instead of relying on physical barriers to block interference, the solution uses electronic filtering to selectively remove interference frequency components from the signal, eliminating the degradation problem inherent in physical shielding materials.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If band-stop filter is used to filter baseband signals, then filtering effect is maintained over time, but device complexity increases

Engineering Contradiction:

Improvefiltering effect stabilityVSAvoidsignal processing structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts only the harmful frequency components from the baseband signal using a band-stop filter, while allowing the useful signal components to pass through unchanged. This selective extraction approach maintains reliability by consistently removing interference without affecting the underlying signal integrity, and the modular filter design keeps the added complexity manageable and localized.

Inventive Principle:

Principle #2Taking out (Extraction)

3Object-affected harmful factors

If shielding materials are used to block interference, then radiation interference is reduced initially, but conduction-based interference continues to affect the system

Engineering Contradiction:

Improveradiation interferenceVSAvoidconduction interference

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent replaces passive electromagnetic shielding with active electronic filtering. The band-stop filter processes signals through electrical circuitry that identifies and removes interference components based on their frequency characteristics, effectively addressing both radiation and conduction-based interference through a unified electronic approach rather than relying on physical shielding barriers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The band-stop filter maintains a strong filtering effect over time, significantly reducing radiation interference and ensuring compliance with electromagnetic compatibility standards, while allowing essential signal components to pass through, thus enhancing the performance and reliability of terminal devices.

Implementation Method 1

a band-stop filter, where a first terminal of the band-stop filter is electrically connected to the interference source, a second terminal of the band-stop filter is grounded, and the band-stop filter is configured to filter a baseband signal output by the interference source

Methodology Applied

Scientific EffectElectrical filtering: Filter (electronic)

Implementation Method 2

using inductors and capacitors to attenuate low-frequency harmonic components

Methodology Applied

Scientific EffectInductance: Inductor

Implementation Method 3

using inductors and capacitors to attenuate low-frequency harmonic components

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11652558B2Signal processing system and terminal device

Publication Date: 2023.05.16 NOKIA TECHNOLOGIES OY

AI summary

A signal processing system includes: an interference source; and a band-stop filter. A first terminal of the band-stop filter is electrically connected to the interference source, a second terminal of the band-stop filter is grounded, and the band-stop filter is configured to filter a baseband signal output by the interference source. The interference source includes a first main board; or the interference source includes a target module and a metal frame used for fastening the target module, and the target module is a display module or a camera module.