Capacitive Sensor Packet Weighting for Reduced Noise
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Solution Overview
Problem
Projected capacitive sensors face challenges in distinguishing signals from noise, particularly when noise frequencies overlap with signal frequencies, exacerbated by the need for quick scan times in touch screens and three-dimensional position detection systems.
Innovation Solution
The method involves acquiring multiple measurement samples with varying gain, integrating them into packets, and applying a weighting function that reduces the importance of samples near electrode changes, allowing for effective signal-noise separation through mathematical post-processing or variable gain amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurement samples are acquired and integrated with varying gain to improve signal clarity, then noise robustness is improved, but measurement time increases
Solution Approach 1:
The patent applies parameter changes by varying the gain for different measurement samples through a weighting function. Samples taken when the electrode is fully settled (middle of packet) receive higher weight, while samples near transitions receive lower weight. This selective weighting improves signal clarity by emphasizing high-quality samples without requiring equal processing of all samples, thus resolving the contradiction between measurement precision and time loss.
2Productivity
If scan time is reduced to maintain responsiveness, then productivity is improved, but noise separation capability deteriorates
Solution Approach 1:
The patent applies local quality by assigning different weights to different samples within the measurement packet based on their quality. Samples taken during stable electrode conditions (middle of packet) are weighted higher, while samples near transitions are weighted lower. This localized quality assessment allows the system to maintain fast scanning while improving signal-noise separation by focusing on high-quality samples, thus resolving the contradiction between productivity and measurement precision.
3Speed
If samples near electrode changes are included with equal weight, then measurement speed is maintained, but noise robustness deteriorates
Solution Approach 1:
The patent applies partial action by selectively weighting only the most reliable samples (those taken when the electrode is fully settled) rather than giving equal weight to all samples. By focusing measurement emphasis on the middle portion of the packet where stability is highest, the system achieves better noise robustness without significantly compromising measurement speed, as the weighted integration still processes all samples but with optimized contribution levels.
Data Source
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AI summary
A method or sensor arrangement for providing capacitive sensor detection with at least one capacitive sensor comprises a transmitting electrode and a receiving electrode. A stimulus at the transmitting electrode is generated and a signal is received from the receiving electrode and data packets are generated, each packet comprising a plurality of samples. The plurality of samples are weighted by providing less gain at a beginning and end of each packet with respect to a center of each packet; and the weighted samples are integrated to generate an output signal for each packet.