Active Pen Frequency Switching for Noise-Resilient Touch Sync

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Solution Overview

Problem

Existing touch sensing devices face challenges in effectively communicating with active pens due to high in-band noise levels, leading to synchronization errors and reduced communication reliability.

Innovation Solution

The active pen and touch controller system employs multiple frequency communication methods, using filters to sample signals at different frequencies and a noise power calculating circuit to identify and adjust frequencies with minimal noise, ensuring reliable communication by alternating frequencies to mitigate noise interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single frequency is used for communication between the active pen and touch controller, then the communication protocol is simple, but in-band noise causes synchronization errors and reduces communication reliability

Engineering Contradiction:

Improvecommunication reliabilityVSAvoidcommunication protocol complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system dynamically switches between multiple frequencies (first frequency and second frequency) for communication. The touch controller and active pen can alternate frequencies based on noise conditions, making the communication protocol adaptive rather than static, thereby improving reliability without requiring a completely complex new protocol

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the frequency parameter of the communication signal. By using multiple frequencies instead of a single fixed frequency, the system can avoid in-band noise that occurs at specific frequencies, improving communication reliability while maintaining protocol simplicity through systematic parameter variation

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple frequencies are used for communication, then in-band noise impact is reduced and communication reliability improves, but the device complexity and processing requirements increase

Engineering Contradiction:

Improvecommunication reliabilityVSAvoidfilter and processing circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The communication process is segmented into different frequency segments. The system divides communication into phases using first frequency and second frequency, with dedicated filters for each frequency segment. This segmentation allows independent optimization of each frequency channel while maintaining overall system reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system employs periodic frequency switching between first and second frequencies. By alternating frequencies in a periodic manner and using corresponding filters, the system reduces continuous noise exposure while maintaining manageable processing requirements through rhythmic, predictable frequency transitions

Inventive Principle:

Principle #19Periodic action

3Stability of the object's composition

If frequency switching is implemented to avoid noise, then communication stability improves, but the timing synchronization becomes more difficult

Engineering Contradiction:

Improvecommunication stabilityVSAvoidsynchronization timing

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The system uses feedback mechanisms where the active pen and touch controller exchange information about frequency usage and timing. This feedback allows both devices to maintain synchronization awareness despite frequency switching, reducing timing loss while preserving communication stability through continuous coordination

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12487708B2Active pen, touch controller, and method of operating active pen

Publication Date: 2025.12.02 SAMSUNG ELECTRONICS CO LTD

AI summary

An active pen adapted for use with a touch pad includes: a receiving circuit configured to generate an internal signal in response to modulating a received uplink signal, a first filter configured to generate a first sampling signal by sampling the internal signal at a first frequency, a second filter configured to generate a second sampling signal by sampling the internal signal at a second frequency unequal to the first frequency, and a timing information generating circuit configured to generate timing information associated with the uplink signal from the internal signal. The receiving circuit is also configured to receive the uplink signal at the first frequency in a first frame, and at the second frequency in a second frame. A noise power calculating circuit is also provided to calculate a noise power level of the uplink signal at each of the first and second frequencies, in response to the first and second sampling signals.