Active Pen Detection via Frequency Multiplexing
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Solution Overview
Problem
Existing input devices face challenges in simultaneously detecting the presence and location of actively modulated input objects, such as active pens, while performing display updating, due to the interference between capacitive sensing and display operations.
Innovation Solution
A capacitive input device with a processing system that drives sensor electrodes with modulated signals of different frequencies to demodulate signals corresponding to both input objects and display updates, allowing for simultaneous capacitive sensing and display operations by using a modulated power supply and dual-gate line routing to integrate capacitive sensing into display panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If capacitive sensing and display updating are performed simultaneously using the same sensor electrodes, then device complexity is reduced and productivity is improved, but signal interference occurs between sensing signals and display update signals
Solution Approach 1:
The patent applies periodic action by using different frequencies for display update signals and capacitive sensing signals. The sensor electrodes are driven with modulated signals at specific frequencies, allowing the system to distinguish between display update effects and input object effects through frequency-based signal separation. This enables simultaneous operation without signal interference.
Solution Approach 2:
The patent changes the frequency parameter of the signals to resolve interference. By operating the capacitive sensing at a different frequency than the display update operation, the system can simultaneously perform both functions using the same sensor electrodes while maintaining signal integrity through frequency discrimination.
2Measurement precision
If separate sensing periods are used for capacitive sensing and active pen detection, then measurement precision is improved, but loss of time increases due to sequential operation
Solution Approach 1:
The patent merges capacitive sensing and active pen detection into a single simultaneous operation using the same sensor electrodes and processing system. By using frequency-modulated signals and a unified processing approach that can distinguish between different signal types, the system achieves both detection functions without requiring separate time periods, thus eliminating time loss while maintaining measurement precision.
Solution Approach 2:
The sensor electrodes are designed to perform multiple functions simultaneously: they serve as both display update electrodes and capacitive sensing electrodes. The processing system is configured to handle both display update signals and sensing signals through a unified architecture that uses frequency discrimination to separate and process different signal types independently.
3Productivity
If modulated signals of different frequencies are used for simultaneous sensing and display updating, then productivity is improved by eliminating separate sensing periods, but device complexity increases due to dual receiver systems
Solution Approach 1:
The processing system is designed with multi-functionality, where a single system handles both display update operations and capacitive sensing operations simultaneously. The receiver architecture, while comprising multiple receivers, is part of a unified processing system that uses frequency-based signal separation to manage multiple functions without requiring entirely separate hardware subsystems.
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 efficient and accurate detection of actively modulated input objects during capacitive sensing and display updating, improving usability and reducing the need for separate sensing periods, thus enhancing the overall performance of input devices.
Implementation Method 1
a capacitive sensing device having a plurality of sensor electrodes organized into a plurality of sets
Implementation Method 2
drive the plurality of sensor electrodes with modulated signals having a first frequency... obtain first resulting signals comprising effects corresponding to the modulated signals... obtain second resulting signals comprising effects corresponding to active signals having a second frequency... demodulate the first resulting signals based on the first frequency and the second resulting signals based on the second frequency
Data Source
AI summary
A capacitive sensing device detects the presence of an actively modulated input object, such as an active pen, using a matrix of sensor electrodes. The capacitive sensing device include receiver channels configured to perform capacitive sensing of the active pen based on one frequency, and other receiver channels configured to perform capacitive sensing of other input objects based on another frequency. The receiver channels for sensing the active pen may be multiplexed across the matrix of sensor electrodes to track the location of the active pen in a tracking window manner. The receiver channels for sensing the active pen may also be multiplexed across the matrix of sensor electrodes to broadly search for the location of the active pen.