Combined Guard Electrode for Long-Range Capacitive Proximity Sensing

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Solution Overview

Problem

Conventional electronic devices, especially smaller ones like cell phones, lack the space for a large enough proximity sensor to detect user presence without awakening the device, limiting the implementation of proximity detection features.

Innovation Solution

A capacitive sensing apparatus incorporating capacitive sensor electrodes and a combined guard and sensing electrode that operates in two modes: a sensing mode to detect objects at a greater distance than the capacitive sensor electrodes and a guarding mode to shield them from interference, allowing for proximity detection without additional space.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If a separate proximity sensor is added to enable proximity detection, then the detection capability is improved, but the device size increases

Engineering Contradiction:

Improveproximity detection capabilityVSAvoiddevice size

Core Design Contradiction:

Difficulty of detecting and measuringVSArea of stationary object

Solution Approach 1:

The patent combines the guard electrode and sensing electrode into a single electrode structure that can operate in different modes. The electrode serves dual purposes: as a guard electrode for shielding and as a sensing electrode for proximity detection, eliminating the need for separate dedicated proximity sensor hardware and reducing overall device footprint

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The electrode is designed to perform multiple functions depending on its operational mode. It can function as a guard electrode to shield against interference, as a sensing electrode for proximity detection, or in a combined mode where it performs both functions simultaneously, maximizing space utilization

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Length of stationary object

If the electrode operates in sensing mode to detect objects at greater distance, then the proximity detection range is improved, but the shielding capability deteriorates

Engineering Contradiction:

Improvedetection rangeVSAvoidshielding capability

Core Design Contradiction:

Length of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The electrode dynamically switches between different operational modes (guard mode, sensing mode, and combined mode) based on system requirements. The control circuit adjusts the electrode's function in real-time, allowing it to optimize between detection range and shielding capability as conditions change

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the electrical parameters of the electrode depending on the desired function. In guard mode, the electrode is biased to provide shielding; in sensing mode, the bias is adjusted to maximize detection range; in combined mode, intermediate parameter settings achieve both shielding and detection

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If the electrode operates in guarding mode to shield sensor electrodes, then the shielding capability is improved, but the proximity detection capability deteriorates

Engineering Contradiction:

Improveshielding capabilityVSAvoidproximity detection capability

Core Design Contradiction:

Object-affected harmful factorsVSDifficulty of detecting and measuring

Solution Approach 1:

The control circuit periodically switches the electrode between guard mode and sensing mode, or uses brief sensing intervals within an otherwise continuous guard mode operation. This periodic action allows the system to maintain shielding while occasionally performing proximity detection without continuous compromise of either function

Inventive Principle:

Principle #19Periodic action

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

Enables proximity detection in smaller devices, allowing the device to awaken and activate features before contact is made, while also protecting the sensors from interference, thus enhancing user experience and functionality without increasing device size.

Implementation Method 1

capacitive sensing apparatus that includes capacitive sensor electrodes (e.g., buttons, one-dimensional sensors, and two-dimensional sensors), and a combined guard and sensing electrode that is disposed proximate to the capacitive sensor electrodes

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

In the second operating mode, the combined guard and sensing electrode can electrically guard the capacitive sensor electrodes

Methodology Applied

Scientific EffectElectrical shielding: Faraday Cage

Data Source

PatentUS7583092B2Capacitive sensing apparatus that uses a combined guard and sensing electrode

Publication Date: 2009.09.01 SYNAPTICS INC

AI summary

A capacitive sensing apparatus includes capacitive sensor electrodes, and a combined guard and sensing electrode that is disposed proximate to the capacitive sensor electrodes. The combined guard and sensing electrode has at least a first operating mode and a second operating mode. In the first operating mode, the combined guard and sensing electrode can detect an object at a distance that is greater than the distance at which the object can be sensed by the capacitive sensor electrodes. In the second operating mode, the combined guard and sensing electrode can electrically guard the capacitive sensor electrodes.