Capacitive Pen Detection in Low Ground Mass Input Devices

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Solution Overview

Problem

In low ground mass states, capacitive pens fail to detect beacon signals due to the user's palm or fingers short-circuiting the signal, leading to synchronization failures and lack of responsiveness in user interfaces.

Innovation Solution

The system focuses the transmission of the beacon signal onto specific subsets of sensor electrodes, changing for consecutive frames to locate and track the capacitive pen, and switches to a continuous tone mode to ensure pen signal transmission, even in low ground mass conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the beacon signal is transmitted using conventional methods across all sensing electrodes, then the signal can be detected under normal ground mass conditions, but the signal is short-circuited and fails to detect the capacitive pen in low ground mass states

Engineering Contradiction:

Improvebeacon signal detection reliabilityVSAvoidsignal short-circuiting by palm or fingers

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent divides the sensing electrodes into multiple subsets (first subset and second subset) that are activated alternately in different frames. This segmentation allows the beacon signal to be transmitted through specific subsets while avoiding areas where the user's palm or fingers may be short-circuiting the signal, thereby maintaining detection reliability in low ground mass states.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs periodic transmission of the beacon signal through different subsets of sensing electrodes in alternating frames. By switching between the first subset in one frame and the second subset in the next frame, the system periodically samples the capacitive pen's presence, ensuring detection despite low ground mass conditions caused by user contact.

Inventive Principle:

Principle #19Periodic action

2Area of stationary object

If the system uses all sensing electrodes for beacon signal transmission, then comprehensive coverage is achieved, but the ground mass is insufficient causing signal failure

Engineering Contradiction:

Improvesensing electrode coverage areaVSAvoidcapacitive pen detection reliability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent segments the sensing electrodes into multiple subsets that are activated alternately. This allows the system to maintain comprehensive coverage over time through periodic switching while ensuring that at any given moment, the active subset provides sufficient ground mass for reliable signal transmission and detection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent dynamically switches between different subsets of sensing electrodes based on frame timing. This dynamic activation pattern allows the system to adapt to low ground mass conditions by selecting subsets that provide adequate grounding, thereby maintaining reliable capacitive pen detection throughout the sensing area.

Inventive Principle:

Principle #15Dynamics

3Object-affected harmful factors

If the beacon signal transmission is interrupted in low ground mass states, then signal short-circuiting is avoided, but synchronization between the capacitive pen and input display device fails

Engineering Contradiction:

Improvesignal short-circuiting preventionVSAvoidsynchronization information loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of information

Solution Approach 1:

The patent uses periodic transmission of the beacon signal through alternating subsets of sensing electrodes. This periodic action ensures that synchronization information is continuously provided to the capacitive pen without interruption, even in low ground mass states, by switching to subsets that provide adequate grounding for each frame.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent maintains continuous synchronization between the capacitive pen and input display device by ensuring the beacon signal is transmitted every frame through appropriate subsets. This continuity of useful action prevents synchronization loss while avoiding signal short-circuiting through intelligent subset selection.

Inventive Principle:

Principle #20Continuity of useful 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

This approach effectively detects and tracks capacitive pens, maintaining interface responsiveness even when the device is in a low ground mass state, preventing signal short-circuiting and ensuring reliable communication.

Implementation Method 1

The sensing circuitry is configured to transmit, during a first frame, a beacon signal on a first subset of sensing electrodes... and receive a pen signal transmitted responsive to the beacon signal

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS12019832B2Low ground mass mitigation for pens

Publication Date: 2024.06.25 SYNAPTICS INC

AI summary

Low ground mass mitigation for pens includes sensing circuitry configured to transmit, during a first frame, a beacon signal on a first subset of sensing electrodes, the first subset being along a first axis of an input device, transmit, during a second frame, the beacon signal on a second subset of the sensing electrodes, the second subset being along the first axis and different from the first subset, and receive a pen signal transmitted responsive to the beacon signal. The processing circuitry is configured to detect a location of a capacitive pen using the pen signal.