Touch Electrode Driving With OFDM-CDMA for Faster Detection
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Solution Overview
Problem
Current touch detection devices in display devices face challenges in improving response speed and reducing false detections, particularly due to the complexity and cost associated with using excessive frequency filters in capacitive sensing systems.
Innovation Solution
The implementation of an orthogonal frequency division multiplexing (OFDM) scheme and a code division multiple access (CDMA) scheme to drive touch electrodes, allowing for efficient generation and processing of driving signals without the need for an excessive number of frequency filters, thereby enhancing response speed and reducing data processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive sensing systems use excessive frequency filters to improve touch detection accuracy, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the need for excessive frequency filters from the traditional capacitive sensing system. By using OFDM and CDMA schemes, the system achieves accurate touch detection without requiring multiple frequency filters, thus reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces the mechanical/filter-based frequency filtering system with a signal processing-based OFDM and CDMA system. This substitution eliminates physical frequency filters and uses mathematical transformations (FFT, correlation operations) to achieve the same or better touch detection accuracy with reduced hardware complexity.
2Reliability
If traditional touch detection systems use multiple frequency filters to reduce false detections, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the need for multiple frequency filters that increase manufacturing cost. The OFDM and CDMA schemes provide reliable false detection reduction through signal processing techniques (orthogonal codes, correlation operations) rather than through multiple physical filters, thereby reducing fabrication cost while maintaining reliability.
Solution Approach 2:
The patent replaces expensive physical frequency filters with computationally intensive but cheaper-to-implement digital signal processing operations. The OFDM and CDMA algorithms can be implemented in software or firmware, which is more cost-effective than manufacturing and assembling multiple precision frequency filters.
3Measurement precision
If traditional systems process touch signals sequentially through multiple filters, then measurement precision is maintained, but response speed decreases
Solution Approach 1:
The patent employs periodic orthogonal codes in the OFDM and CDMA schemes that enable parallel processing of multiple touch signals. The periodic nature of the orthogonal codes allows for efficient correlation operations that can be performed simultaneously, maintaining measurement precision while significantly improving touch response speed compared to sequential filter processing.
Solution Approach 2:
The patent applies preliminary signal modulation using orthogonal codes before the actual touch detection process. This preliminary action organizes the signals in a way that enables faster processing during detection, as the orthogonal structure allows for direct correlation-based extraction of touch information without requiring multiple sequential filtering steps.
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
This approach enables faster touch response times and reduces the number of elements and fabrication costs by utilizing OFDM and CDMA schemes to process touch driving signals, effectively addressing the limitations of existing touch detection technologies.
Implementation Method 1
The touch sensing circuit may include a plurality of sensing channels respectively connected to the plurality of sensing electrodes and configured to detect a change in capacitance at each of a plurality of touch nodes formed by intersections of the plurality of driving electrodes and the plurality of sensing electrodes
Data Source
AI summary
A touch detection device supplies driving signals generated based on orthogonal carriers and a CDMA scheme to driving electrodes. A touch driving circuit drives the driving electrodes in groups including a first group and a second group, supplies first driving signals based on a designated first frequency and first orthogonal codes set to correspond to the driving electrodes of the first group, respectively, to the driving electrodes of the first group, and supplies second multiple driving signals based on a second frequency orthogonal to the first frequency and second orthogonal codes set to correspond to the driving electrodes of the second group, respectively, to the driving electrodes of the second group.