Digital Differential Detection for Capacitive Touch Sensors
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Solution Overview
Problem
Conventional touch and fingerprint sensing technologies face challenges in mitigating noise effectively, particularly in mobile devices, due to the high power and area consumption of analog-based circuits used for differential sensing, which are not feasible for large-scale implementations.
Innovation Solution
A digital differential detection system for capacitive sensors that converts analog signals from multiple nodes to digital signals and performs difference calculations in the digital domain, using analog-to-digital converters and digital signal processing circuits to mitigate noise and accurately detect touch and fingerprint features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog-based circuits with operation amplifiers are used for differential sensing, then noise mitigation is improved, but power consumption and area requirements increase significantly
Solution Approach 1:
The patent replaces the analog-based operation amplifier circuits with a digital signal processing approach. The system uses analog-to-digital converters to transform analog signals into digital signals, then performs differential detection through digital subtraction in a processor. This substitution of analog mechanical/electronic systems with digital systems eliminates the need for numerous operation amplifiers, dramatically reducing power consumption and chip area while maintaining noise mitigation capabilities.
Solution Approach 2:
The patent changes the fundamental parameter of signal representation from analog voltage levels to digital bit representations. By converting signals to the digital domain and performing differential detection through digital arithmetic operations rather than analog voltage comparison, the system achieves the same noise rejection function with significantly reduced hardware complexity and power requirements.
2Reliability
If analog-based circuits with operation amplifiers are used for differential sensing, then noise mitigation is improved, but chip area increases significantly
Solution Approach 1:
The patent replaces the analog-based operation amplifier circuits with a digital signal processing approach. The system uses analog-to-digital converters to transform analog signals into digital signals, then performs differential detection through digital subtraction in a processor. This substitution of analog mechanical/electronic systems with digital systems eliminates the need for numerous operation amplifiers, dramatically reducing power consumption and chip area while maintaining noise mitigation capabilities.
Solution Approach 2:
The patent changes the fundamental parameter of signal representation from analog voltage levels to digital bit representations. By converting signals to the digital domain and performing differential detection through digital arithmetic operations rather than analog voltage comparison, the system achieves the same noise rejection function with significantly reduced hardware complexity and power requirements.
3Measurement precision
If 50 receivers with 10 reference nodes each are implemented, then measurement precision is improved, but the number of operation amplifiers required increases to 500
Solution Approach 1:
The patent replaces the analog-based operation amplifier circuits with a digital signal processing approach. The system uses analog-to-digital converters to transform analog signals into digital signals, then performs differential detection through digital subtraction in a processor. This substitution of analog mechanical/electronic systems with digital systems eliminates the need for numerous operation amplifiers, dramatically reducing power consumption and chip area while maintaining noise mitigation capabilities.
Solution Approach 2:
The patent merges the differential detection function with the existing receiver architecture by implementing digital signal processing in the processor rather than requiring separate analog difference circuits for each receiver. This consolidation approach maintains the ability to perform precise differential measurements across all 50 receivers without requiring 500 separate operation amplifiers, as the digital processing can handle multiple signals sequentially or in parallel through software implementation.
Data Source
AI summary
A system and method for digital differential detection includes a capacitive sensor having a first node and a second node, a transmitter configured to transmit an input signal through the first node and the second node, and a receiver coupled to the first node and the second node. The receiver is configured to receive a first modified input signal from the first node and a second modified input signal from the second node. The receiver includes first and second analog-to-digital converters configured to convert the first modified input signal to a first digital signal and the second modified input signal to a second digital signal. The receiver also includes a first differencing circuit configured to calculate a first difference between the first digital signal and a second digital signal and a decision circuit configured to output a result according to the first difference.