Capacitive Touch Interface Stylus Signal Amplification

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Solution Overview

Problem

Touch screens struggle to detect input from styluses due to their smaller surface area, which results in insufficient disturbance of the stimulation signal, and data transfer through touch screens is unreliable due to noise sources and capacitance coupling.

Innovation Solution

A receiving unit is integrated into the touch interface to amplify input signals from styluses, allowing them to communicate digital data, including touch location and additional sensor data, by using band pass, high pass, or low pass amplification, and transmitting data at a different frequency from touch event scanning, enabling bi-directional communication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a stylus with a small touch surface area is used, then the precision of input is improved, but the ability to disturb the stimulation signal sufficiently for detection deteriorates

Engineering Contradiction:

Improvetouch location detection precisionVSAvoidtouch surface area

Core Design Contradiction:

Measurement precisionVSArea of moving object

Solution Approach 1:

The patent changes the electrical parameters of the stylus by incorporating a capacitor that can store and release electrical charge. This allows the stylus to generate sufficient electrical disturbance in the stimulation signal despite having a small physical surface area, enabling detection precision without requiring large contact area.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary electrical coupling mechanism where the stylus capacitively couples with the touch sensor panel. This intermediary coupling allows signal transfer and detection without direct mechanical contact, enabling small surface area stylus to be detected effectively through electrical field interaction.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If data transfer through the touch screen interface is implemented, then the functionality of the input device is improved, but the reliability of data transfer deteriorates due to noise and capacitance coupling

Engineering Contradiction:

Improvedata transfer capabilityVSAvoiddata transfer reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements feedback mechanisms where the computing device sends acknowledgment signals back to the stylus to confirm successful data reception. This feedback loop allows for error detection and retransmission, significantly improving data transfer reliability through the noisy capacitive coupling interface.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent employs error correction coding and data validation protocols before transmission to preemptively protect against noise-induced errors. By preparing redundant information and validation checks in advance, the system cushions against the unreliable capacitive coupling channel.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Measurement precision

If the receiving unit amplifies the input signal, then the detection capability is improved, but the power consumption increases

Engineering Contradiction:

Improvesignal detection capabilityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic sampling and amplification rather than continuous operation. The receiving unit amplifies signals only when touch events are detected or at scheduled intervals, significantly reducing overall power consumption while maintaining detection precision when needed.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent employs dynamic gain adjustment where the amplification level is automatically adjusted based on the detected signal strength. When signals are strong, amplification is reduced; when signals are weak, amplification is increased. This dynamic adaptation maintains detection precision while minimizing power consumption.

Inventive Principle:

Principle #15Dynamics

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 receiving unit enhances the detection of stylus input and reliable data transfer by overcoming signal attenuation and noise, allowing for accurate location sensing and simultaneous touch event scanning, reducing power usage and increasing data transmission efficiency.

Implementation Method 1

The touch interface is configured to detect an input signal corresponding to an object approaching or contacting a surface, such as through capacitive coupling

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS9652090B2Device for digital communication through capacitive coupling

Publication Date: 2017.05.16 APPLE INC

AI summary

A computing device configured to communicate with an input device. The computing device includes a processor, a touch interface, such as a touch screen, and a receiving unit. The touch interface is configured to detect an input signal corresponding to an object approaching or contacting a surface. The receiving unit is configured to receive, through the touch interface, at least one input signal from the input device, and the receiving unit amplifies the at least one input signal creating at least one amplified input signal. Additionally, at least one of the processor or the receiving unit analyzes the at least one amplified input signal and creates at least one output digital signal corresponding to the at least one input signal.