Multi-touch Sensor Noise Reduction via Mutual Signal Detection
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Solution Overview
Problem
Current user input systems face challenges in achieving low-latency and noise reduction in fast multi-touch sensors, particularly in distinguishing real touch events from noise and phantom touches, especially in environments with electromagnetic interference.
Innovation Solution
The system employs a configuration where both rows and columns transmit and receive unique signals, requiring mutual signal detection to confirm touch events, and uses signal processing techniques like frequency modulation and direct sequence spread spectrum modulation to reduce interference, along with dynamic assignment of signal channels to minimize noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast multi-touch sensors are used to achieve low-latency touch detection, then response speed is improved, but noise and phantom touches increase
Solution Approach 1:
The system uses mutual signal detection where row signals are detected by column receivers and column signals are detected by row receivers. This feedback mechanism allows the system to verify touch events through cross-validation, distinguishing real touches from noise by requiring consistent signal detection in both row and column directions.
Solution Approach 2:
The patent introduces unique orthogonal signals as intermediaries that are transmitted along rows and columns. These signals act as mediators that can be independently detected and verified, enabling the system to filter out electromagnetic noise while maintaining fast response times through structured signal validation.
2Reliability
If signal processing techniques like frequency modulation are used to reduce interference, then noise reduction is improved, but device complexity increases
Solution Approach 1:
The system changes the frequency parameter of transmitted signals using frequency modulation and direct sequence spread spectrum techniques. By varying signal frequencies and using orthogonal coding schemes, the system can distinguish between different signal sources and filter out noise without requiring complex hardware modifications.
Data Source
AI summary
A low-latency touch sensitive device provides a method for determining a location of a touch event thereon. The touch sensitive device row conductors and column conductors, the path of each of the row conductors crossing the path of each of the column conductors. Each of a set of orthogonal row signals are simultaneously transmitted on a respective one of at least some of the row conductors and an amount of each of the plurality of orthogonal row signals present on each of the plurality of column conductors is detected. A set of orthogonal column signals are simultaneously transmitted on a respective one of at least some of the column conductors. An amount of each of the orthogonal column signals present on each of the plurality of row conductors is detected. The detected amount of each of the plurality of orthogonal row signals and the detected amount of each of the plurality of orthogonal column signals is used to determine the location of a touch event on the device.