Capacitive Sensor Noise Compensation via Grouped Offset Adjustment
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Solution Overview
Problem
Proximity sensor devices face challenges in accurately distinguishing input objects from noise sources due to common noise affecting multiple sensor electrodes, leading to inaccurate capacitive sensing measurements.
Innovation Solution
The solution involves categorizing sensor electrodes into groups affected by common noise sources, calculating offsets when no input object is detected, and compensating for noise by adjusting the resulting signals using these offsets to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor electrodes are grouped to compensate for common noise sources, then measurement precision is improved, but device complexity increases due to additional signal processing requirements
Solution Approach 1:
The sensor electrode array is segmented into multiple groups where each group is affected by a common noise source. This segmentation allows independent noise compensation for each group by calculating group-specific offsets, thereby improving measurement precision without requiring complete system redesign
Solution Approach 2:
The system calculates offsets based on measured signals from sensor electrodes and uses these offsets to compensate for common noise sources in subsequent measurements. This feedback mechanism continuously refines measurement accuracy by adapting to noise patterns, resolving the contradiction between precision improvement and processing complexity
2Measurement precision
If offsets are calculated and applied to compensate for common noise, then measurement precision is improved, but processing time increases
Solution Approach 1:
Offsets are calculated in advance during periods when no input object is present or during calibration phases. By performing this preliminary action before actual sensing operations, the system avoids adding processing time during critical measurement periods, thus improving precision without significant time loss
Solution Approach 2:
The noise compensation process is implemented periodically - calculating offsets during idle periods or calibration cycles, then applying them continuously during sensing operations. This periodic approach separates the computationally intensive offset calculation from the continuous measurement process, minimizing time impact while maintaining high precision
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 accuracy of capacitive sensing by effectively removing noise from measurements, allowing for better detection of input objects and generating more reliable capacitive images.
Implementation Method 1
A proximity sensor device... determines the presence, location and/or motion of one or more input objects... capacitive sensing measurements
Implementation Method 2
calculate at least one offset using the resulting signals based on a determination that the input object is not proximate to the sensor electrodes in the first group and compensate for an effect of the common noise source by adjusting the resulting signals using the at least one offset
Data Source
AI summary
This disclosure generally provides an input device with a matrix sensor that includes a plurality of sensor electrodes arranged on a common surface or plane. Moreover, the input device includes routing traces that electrically couple the sensor electrodes to analog front ends (AFEs). Because of the spatial relationships between these electrical components, the sensor electrodes can be categorized into groups where each of the sensors in the group is affected by a common noise source. The capacitive measurements for the sensor electrodes in each of the groups are compared to a touch threshold to determine if an input object (e.g., finger or stylus) is proximate to the sensor electrodes. If the capacitive measurements are below the touch threshold, the input device calculates an offset value that compensates for the noise. After the offset is applied, the compensated capacitive measurements are used to generate a capacitive image.