Transcapacitive Sensor Electrode Isolation via Non-Modulated Signals
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Solution Overview
Problem
Transcapacitive sensing methods using routing traces under sensor electrodes face challenges with high background capacitive coupling, leading to decreased signal-to-noise ratios and inaccurate touch sensing.
Innovation Solution
The proposed solution involves a processing system with a transmitter module, receiver module, and timing module that drives signals on sensor electrodes in a specific manner to isolate the receiver electrode from other electrodes, reducing background capacitance by applying a non-modulated signal to adjacent electrodes, thereby improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If routing traces are disposed under the sensor electrodes for transcapacitive sensing, then the sensor structure is simplified and manufacturing is easier, but high background capacitive coupling occurs between the traces and sensor electrodes, decreasing the signal to noise ratio
Solution Approach 1:
The sensor electrodes are divided into transmitter electrodes and receiver electrodes that are selectively activated at different times. This segmentation allows the system to isolate the measurement signal from background capacitive coupling by comparing signals taken during different phases of electrode activation.
Solution Approach 2:
The transmitter and receiver electrodes are activated in periodic alternating phases. During transmitter phases, transmitter electrodes are modulated while receiver electrodes are held constant; during receiver phases, the roles are reversed or receiver electrodes measure while transmitter electrodes are held constant. This periodic switching enables background subtraction and improves signal-to-noise ratio.
2Adaptability or versatility
If transcapacitive sensing methods are used to detect multiple input objects, then the detection capability is improved, but background capacitive coupling increases, making accurate touch sensing more difficult
Solution Approach 1:
The electrode array is segmented into multiple independent transmitter and receiver electrodes that can be selectively activated. This allows the system to perform multiple transcapacitive measurements simultaneously or sequentially, enabling multi-object detection while maintaining precision through selective measurement pairs.
Solution Approach 2:
The system uses feedback from background capacitance measurements to adjust and subtract background coupling effects from the actual touch signals. By continuously monitoring and comparing signals during different electrode activation phases, the system can differentiate between background coupling and actual touch events, improving accuracy for multiple objects.
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 enhances the signal-to-noise ratio, enabling more precise and robust determination of object location relative to the sensor electrodes, particularly in touch sensors with routing traces under the sensor electrodes.
Implementation Method 1
transcapacitive sensing methods based on changes in the capacitive coupling between sensor electrodes
Implementation Method 2
an input object near the sensor electrodes alters the electric field between the sensor electrodes, thus changing the measured capacitive coupling
Data Source
AI summary
Disclosed herein include a processing system, an input device, and methods for transcapacitive sensing. In one example, a processing system is configured to reduce the capacitive coupling between sensor electrodes arranged in a column of sensor electrodes and routing traces running below the sensor electrodes by isolating a receiver electrode selected from the sensor electrodes in the column from the other sensor electrodes in the column by applying a signal that is not modulated relative to the receiver electrode on sensor electrodes that are immediately adjacent the receiver electrode and not being utilized as a transmitter electrode.