Capacitive Sensor Gain Correction for Fast Panel Scanning
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Solution Overview
Problem
Current touch-sensor technologies face challenges in achieving high fidelity and accuracy while maintaining fast scan times and low power consumption, particularly due to signal disparity and manufacturability issues in capacitive sensor arrays.
Innovation Solution
A capacitive sensor array with a totem pole pattern is implemented, featuring main traces and subtraces, which reduces signal disparity and manufacturability problems, allowing for decreased costs and increased yield rates, and includes a method for per-node gain correction to improve signal strength and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional capacitive sensor arrays are used, then manufacturing is simpler, but signal disparity and accuracy deteriorate
Solution Approach 1:
The sensor array is segmented into multiple trace types (main traces and subtraces) with different functions. Main traces provide signal routing while subtraces provide sensing functionality, allowing the system to achieve high signal accuracy through specialized trace configurations without requiring complete redesign of the entire sensor array structure.
Solution Approach 2:
Different regions of the sensor array use different trace configurations optimized for their specific functions. Main traces are optimized for signal transmission with appropriate impedance control, while subtraces are optimized for capacitive sensing. This local optimization allows each region to perform its function with maximum efficiency while maintaining overall system manufacturability.
2Speed
If fast scan times are implemented, then user interface responsiveness improves, but signal fidelity and accuracy deteriorate
Solution Approach 1:
The system performs preliminary calibration and characterization of each sensor node's signal characteristics during manufacturing or initialization. This preliminary action creates a lookup table or correction factors that are applied during fast scanning operations, allowing the system to maintain high signal fidelity even at reduced scan times by pre-computing the necessary corrections.
Solution Approach 2:
The patent replaces slow, sequential scanning methods with a parallel sensing architecture where multiple sensor nodes can be read simultaneously or in rapid succession. The totem pole trace configuration enables this by providing dedicated signal paths that minimize interference and allow faster readout without sacrificing signal quality.
3Measurement precision
If per-node gain correction is applied, then measurement precision improves, but computational complexity increases
Solution Approach 1:
The system changes the electrical parameters (gain factors) of individual sensor nodes based on their measured characteristics. By adjusting the gain parameter for each node according to its specific signal strength and noise characteristics, the system achieves uniform measurement precision across all nodes while using simple multiplicative correction factors that minimize computational complexity.
4Manufacturing precision
If totem pole trace pattern is used, then signal disparity reduces, but manufacturing complexity increases
Solution Approach 1:
The patent merges the signal transmission function and the sensing function into a single integrated trace structure. The totem pole configuration combines main traces for signal routing with subtraces for sensing in a unified pattern that can be fabricated using standard thin-film deposition and patterning processes, avoiding the need for separate fabrication steps for different trace types.
Data Source
AI summary
A method calculates a correction factor for one or more of capacitance sensors and generates a current from a mutual capacitance of one of the capacitance sensors. The method applies the correction factor to the generated current to generate a corrected current and converts the corrected current to a digital value. The method determines a position of one or more conductive objects in proximity to the one or more capacitance sensors based on the digital value.