Multi-Shield Capacitive Sensing Circuit for Distant Proximity Accuracy

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Solution Overview

Problem

Existing capacitive touch sensing systems in mobile devices face challenges in accurately detecting proximity at distant areas without increasing the number of components, leading to reduced accuracy and increased size and cost due to the limitations of single sensing ICs with a single shield terminal.

Innovation Solution

A capacitive touch controller with separate shielding areas connected to distinct terminals, allowing for independent voltage control of each shielding area to reduce interference and improve accuracy, while using a single capacitive sensing circuit to manage multiple sensing elements and shielding areas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single sensing IC with a single shield terminal is used, then device complexity and cost are reduced, but proximity sensing accuracy at distant areas deteriorates due to increased interference and inability to independently control shielding voltages

Engineering Contradiction:

Improveproximity sensing accuracyVSAvoidsensing circuit configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent divides the single shielding area into multiple separate shielding areas (first shielding area and second shielding area), each connected to distinct shield terminals. This segmentation allows independent voltage control of each shielding area, enabling the system to maintain accurate proximity sensing at distant locations by reducing interference through targeted shielding rather than using a single centralized shield.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If multiple sensing ICs are used to improve proximity sensing accuracy at distant areas, then measurement precision improves, but device size, component quantity, and cost increase

Engineering Contradiction:

Improveproximity sensing accuracyVSAvoidnumber of components

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent makes a single sensing IC capable of supporting multiple sensing elements (first sensing element and second sensing element) with separate shielding areas. The sensing IC's shield control module can independently control multiple shield terminals, allowing one IC to perform the function that would otherwise require multiple ICs, thereby reducing component quantity while maintaining improved proximity sensing accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Object-affected harmful factors

If separate shielding areas with distinct terminals are implemented, then interference is reduced and sensing accuracy improves, but device complexity and manufacturing complexity increase

Engineering Contradiction:

Improveinterference levelVSAvoidmanufacturing complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent combines multiple shielding functions into a single integrated sensing IC chip. The shield control module within the IC independently controls multiple shield terminals, merging what would otherwise be separate discrete components into one unified device. This integration reduces manufacturing complexity compared to using multiple separate ICs or discrete shielding components, while still providing the interference reduction benefits of separate shielding areas.

Inventive Principle:

Principle #5Merging (Combining)

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 solution enhances proximity sensing accuracy at distant areas without adding components, reducing interference and maintaining a compact device design, thereby improving user interaction and functionality while minimizing costs.

Implementation Method 1

Proximity sensor 11 uses the self-capacitance of a sensing element to determine whether a user is in proximity. Self-capacitance of the sensing element changes as a user's body part moves nearby proximity sensor 11.

Methodology Applied

Scientific EffectSelf-capacitance: Capacitance

Implementation Method 2

Capacitive touch sensing utilizes shielding planes under the sensing elements to provide directionality of sensing and reduce interference from noise. The shielding planes for capacitive touch sensing are driven by the integrated circuit (IC) which senses the self-capacitance of the sensing elements.

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Data Source

PatentUS9542050B2Multi-shield capacitive sensing circuit

Publication Date: 2017.01.10 SEMTECH CORP

AI summary

A proximity sensor includes a capacitive touch controller. A first shielding area is coupled to a first shield terminal of the capacitive touch controller. A second shield area is coupled to a second shield terminal of the capacitive touch controller. A first sensing element is disposed adjacent to the first shielding area. The first sensing element is coupled to a first sensing terminal of the capacitive touch controller. A second sensing element is disposed adjacent to the second shielding area. The second sensing element is coupled to a second sensing terminal of the capacitive touch controller. The capacitive touch controller is configured to associate the first sensing element with the first shielding area. A self-capacitance of the first sensing element is measured while the second shielding area is inactive. The self-capacitance of the first sensing element is measured at a first frequency.