Capacitive Position Indicator Full-Duplex Signal Feedback
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Solution Overview
Problem
Existing position indicators for capacitance-type sensors face challenges in detecting fine input positions due to the need for high capacitance and the limitations of unidirectional signal transmission and half-duplex communication, which affect detection sensitivity and waveform continuity.
Innovation Solution
A position indicator with a full-duplex communication structure, featuring independent signal input and output channels, and a signal enhancing processing circuit that amplifies and modifies the AC signal received from the sensor, ensuring high sensitivity and waveform correlation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If unidirectional signal transmission is used in position indicators, then the structure is simpler, but detection sensitivity deteriorates because the indicator cannot actively enhance the signal for fine-tip styluses
Solution Approach 1:
The position indicator receives an AC reference signal from the position detecting sensor through its receiving electrode, processes this signal through amplification and phase inversion, and feeds back an enhanced AC signal through its output electrode. This feedback mechanism allows the indicator to actively enhance the capacitive coupling signal, thereby improving detection sensitivity for fine-tip styluses while maintaining structural simplicity.
2Device complexity
If half-duplex communication with switch circuits is used, then device complexity is reduced, but waveform continuity deteriorates due to switching interruptions
Solution Approach 1:
The position indicator employs separate receiving and output electrodes that are spatially segmented and functionally independent. The receiving electrode continuously receives the AC reference signal from the sensor, while the output electrode simultaneously transmits the enhanced AC signal back to the sensor. This segmentation eliminates the need for switching circuits, ensuring continuous waveform transmission and improving detection stability.
3Measurement precision
If fine-tip stylus is used for input, then input precision is improved, but capacitance decreases making position detection difficult
Solution Approach 1:
The position indicator acts as an intermediary device that receives the weak AC reference signal from the capacitance-type position detecting sensor through its receiving electrode, amplifies this signal through a signal amplifying circuit, inverts its phase, and transmits the enhanced signal back through its output electrode to the sensor. This intermediary function compensates for the low capacitance of fine-tip styluses, enabling precise position detection that would otherwise be impossible with such low capacitance values.
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 solution enhances detection sensitivity and versatility of the position indicator, allowing for precise position detection with high sensitivity and consistent waveform correlation, even with fine-tip styluses, while minimizing the need for complex switch circuits and ensuring real-time signal continuity.
Implementation Method 1
a position detecting sensor in which position detection is carried out by detecting a change in capacitance
Implementation Method 2
a signal enhancing processing circuit for amplifying the AC signal received from the position detecting sensor via the first electrode
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A position indicator is provided for use with a position detecting sensor that carries out position detection by detecting a change in capacitance. The position indicator includes: a first electrode configured to receive an alternating-current (AC) signal from the position detecting sensor; a signal enhancing processing circuit configured to subject the AC signal received via the first electrode to determined signal enhancing processing; and a second electrode different from the first electrode and configured to be supplied with a signal output from the signal enhancing processing circuit. An enhanced signal having a determined correlation with the AC signal received via the first electrode from the position detecting sensor is formed while the enhanced signal is sent out to the position detecting sensor via the second electrode.