Multi-Frequency Parallel Touch Sensing for Lower Display Interference
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Solution Overview
Problem
Touch sensors utilizing absolute-capacitance and transcapacitive sensing face issues such as touch-to-display interference, sensitivity to temperature drift, and require significant computational complexity and silicon area.
Innovation Solution
Implementing a multi-frequency parallel transcapacitive sensing method using a subset of sensor electrodes as transmitter and receiver electrodes, driven with multiple frequencies to obtain capacitive touch profiles, and compensating for low-ground mass signal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transcapacitive sensing is used, then touch sensitivity is improved, but touch-to-display interference increases
Solution Approach 1:
The sensor array is segmented into multiple independent sensor electrodes that can be individually controlled as transmitter or receiver electrodes. This segmentation allows the system to perform sensing operations in discrete bursts, isolating the sensing process from display operations and reducing interference between the two functions.
Solution Approach 2:
The sensing system operates in periodic bursts rather than continuously. During sensing bursts, the sensor electrodes are activated to detect touch, while during non-burst periods, the display can operate without interference. This periodic operation allows the display and sensing functions to share the same physical space without simultaneous interference.
2Measurement precision
If multiple bursts are used to capture touch profiles, then measurement accuracy is improved, but computational complexity increases
Solution Approach 1:
The system performs preliminary sensing bursts to capture touch profile data before final processing is required. By obtaining the capacitive touch profile in advance during dedicated sensing bursts, the system can prepare the data for processing without delaying the overall touch response time, and the computational processing can be performed separately without increasing real-time complexity.
3Measurement precision
If absolute-capacitance sensing is used, then sensing capability is improved, but silicon area requirement increases
Solution Approach 1:
The sensor electrodes are designed to serve multiple functions: they can operate as both transmitter and receiver electrodes, and can be configured for different sensing modes (absolute capacitance, transcapacitive, or a combination). This multi-functionality allows the same physical silicon area to support multiple sensing approaches, maximizing the utility of the available sensor real estate without requiring additional dedicated areas for each sensing mode.
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
Reduces touch-to-display interference, minimizes sensitivity to temperature drift, optimizes silicon usage, and enhances computational efficiency by completing touch sensing in fewer bursts, while providing accurate capacitive touch profiles.
Implementation Method 1
operating a first plurality of sensor electrodes of the first subset as transmitter electrodes, including driving the transmitter electrodes with sensing signals of two or more different frequencies
Implementation Method 2
obtain a first capacitive touch profile based on the obtained resulting signals
Implementation Method 3
operating a second plurality of sensor electrodes of the first subset as receiver electrodes, including obtaining resulting signals via the receiver electrodes corresponding to the sensing signals
Data Source
AI summary
An input device includes: a plurality of sensor electrodes disposed in a sensing region of the input device; and a processing system configured to operate a first subset of the plurality of sensor electrodes in a multi-frequency parallel transcapacitive sensing manner to obtain a first capacitive touch profile. Operating the first subset of the plurality of sensor electrodes in the multi-frequency parallel transcapacitive sensing manner to obtain the first capacitive touch profile includes: operating a first plurality of sensor electrodes of the first subset as transmitter electrodes, including driving the transmitter electrodes with sensing signals of two or more different frequencies; operating a second plurality of sensor electrodes of the first subset as receiver electrodes, including obtaining resulting signals via the receiver electrodes corresponding to the sensing signals; and obtaining the first capacitive touch profile based on the obtained resulting signals.