Capacitive Sensor Loop Filter for Impedance Sensing
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Solution Overview
Problem
Current capacitive sensing technologies face challenges with high resolution sensing requiring expensive and area-intensive electronic instrumentation, and are susceptible to non-linearity and parasitic sensitivity issues, limiting their performance and manufacturing efficiency.
Innovation Solution
A capacitive sensor system utilizing a receiver stage with a loop filter that activates upon capacitance threshold changes, allowing for high resolution sensing with lower resolution electronic instrumentation, and employing multiple receiver and transmitter channels with specialized open loop transfer functions and weighted channel summation to achieve self-sustained oscillation and decaying burst modes, reducing sensitivity to parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high resolution sensing is implemented using conventional capacitive sensing technologies, then sensing precision is improved, but device complexity and manufacturing cost increase due to expensive and area-intensive electronic instrumentation
Solution Approach 1:
The patent replaces complex electronic measurement instrumentation with a field-based sensing approach using electromagnetic oscillation. Instead of using expensive electronic instruments to measure capacitance changes, the system uses a transmitter electrode to generate electromagnetic fields and receiver electrodes to detect field interactions with objects, substituting electronic measurement complexity with electromagnetic field-based detection.
Solution Approach 2:
The patent introduces electromagnetic fields as an intermediary between the sensing system and the object being detected. The transmitter electrode generates electromagnetic fields that interact with the object, and the receiver electrodes detect these field interactions, using the electromagnetic field as a mediator to transfer information about the object's presence and properties without requiring direct electronic contact or complex measurement instrumentation.
2Measurement precision
If conventional capacitive sensing is used to achieve high resolution, then measurement precision is improved, but parasitic sensitivity and non-linearity issues worsen
Solution Approach 1:
The patent substitutes direct capacitance measurement with electromagnetic field interaction detection. Instead of measuring capacitance directly (which is susceptible to parasitic effects and non-linearity), the system uses electromagnetic oscillation at specific frequencies to detect objects, replacing the vulnerable electrical measurement mechanism with a more robust electromagnetic field-based approach that is less sensitive to parasitic capacitance and non-linear effects.
3Measurement precision
If multiple receiver and transmitter channels are added to improve sensing capability, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the electrode array multi-functional by enabling each electrode to serve as both a transmitter and a receiver at different times. Instead of requiring separate dedicated transmitter and receiver channels, the same physical electrodes are used for both functions through time-multiplexed operation, reducing the overall number of components needed while maintaining the capability for precise multi-point sensing.
Solution Approach 2:
The patent employs periodic switching between transmitter and receiver modes in the electrode array. Electrons are activated in periodic intervals to transmit electromagnetic fields, while receiver electrodes periodically sample the field interactions, using time-division multiplexing to enable multiple sensing channels to operate sequentially rather than simultaneously, thereby reducing hardware complexity while maintaining measurement 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
Enables high resolution sensing with reduced electronic complexity and cost, while minimizing the impact of parasitic sensitivity and non-linearity, allowing for efficient detection of capacitance changes and object proximity in devices like touchscreens and mobile devices.
Implementation Method 1
a transmitter electrode to generate an electrical oscillation
Implementation Method 2
sense an impedance change in a local space between the transmitter electrode and the receiver electrode
Implementation Method 3
reducing sensitivity to parasitic effects
Data Source
Figure 1~2
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Figure 4
AI summary
A receiver stage of a sensor system includes a receiver electrode and a loop filter. The loop filter is configured to activate electrical oscillation and thus the receiver stage when a capacitance measurement reaches a threshold and issue the capacitance measurement upon activation of the receiver stage. The capacitance measurement includes capacitance with respect to an inactive transmitter electrode.