Central Receiver Capacitive Sensing With Reference Voltage Modulation
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Solution Overview
Problem
Existing input devices face challenges in efficiently performing capacitive sensing while maintaining low power consumption and accurately detecting input objects, particularly in low ground mass conditions, due to interference from environmental capacitances.
Innovation Solution
The implementation of a reference voltage modulator that modulates reference voltage rails to enable capacitive sensing by isolating them from the power source, allowing for simultaneous signal acquisition from display and sensor electrodes, and using a central receiver to normalize signals and mitigate the effects of low ground mass conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive sensing is performed without reference voltage modulation, then the sensing operation can be performed, but environmental capacitances cause interference and reduce measurement precision
Solution Approach 1:
A reference voltage modulator is introduced as an intermediary component that modulates the reference voltage rails coupled to the sensor electrodes. This modulation creates a differentiated signal pattern that allows the receiver to distinguish between environmental capacitances and actual input objects, thereby eliminating interference while maintaining sensing accuracy
Solution Approach 2:
The reference voltage rails are modulated by changing their voltage parameters in a specific pattern. This parameter change creates a time-varying signal that enables the system to differentiate between static environmental capacitances and dynamic input object signals, improving measurement precision by filtering out environmental interference
2Measurement precision
If multiple receivers are used for signal acquisition, then sensing coverage is improved, but power consumption and device complexity increase
Solution Approach 1:
The reference voltage modulator serves multiple functions simultaneously: it modulates the reference voltage rails for signal differentiation, provides a timing reference for the receiver, and enables both environmental capacitance cancellation and input object detection using the same hardware infrastructure, thereby achieving improved sensing without proportionally increasing power consumption
Solution Approach 2:
The system combines environmental capacitance measurement and input object detection into a unified capacitive sensing framework. By measuring total capacitance through the modulated reference voltage and subtracting the environmental component, the system achieves accurate input detection using integrated circuitry rather than separate dedicated receivers for each function
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 allows for efficient power management, accurate detection of input objects, and reduced interference from environmental capacitances, enhancing the overall performance of capacitive sensing in input devices.
Implementation Method 1
perform capacitive sensing
Implementation Method 2
acquire second resulting signals from each of the sensor electrodes simultaneously
Data Source
AI summary
This disclosure generally provides an input device that includes multiple sensor and display electrodes and a processing system. The processing system includes a plurality of local receivers coupled to respective ones of the sensor electrodes, where the local receivers are configured to acquire first resulting signals from the sensor electrodes. The processing system also includes a central receiver coupled to the sensor electrodes and configured to acquire second resulting signals from each of the sensor electrodes.