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CMOS Capacitive Fingerprint Sensor Based on Differential Sensing Circuit with Noise Cancellation
Hossam Hassan1,2, Hyung-Won Kim3
1Department of Electronic Engineering, College of Electrical and Computer Engineering, Chungbuk National University, Cheongju 28644, Korea. hossam@cbnu.ac.kr.
Sensors (Basel, Switzerland)
|July 11, 2018
Summary
This study presents a novel differential sensing technique for capacitive fingerprint detection, significantly enhancing sensitivity and speed. The new CMOS sensor architecture improves signal-to-noise ratio, even in noisy environments.
Area of Science:
- Electrical Engineering
- Biometrics
- Sensor Technology
Background:
- Capacitive fingerprint sensors are crucial for biometric authentication.
- Existing techniques face challenges with parasitic capacitances, noise, and varying finger conditions.
- Need for higher sensitivity and faster detection in CMOS fingerprint sensors.
Purpose of the Study:
- To introduce a novel differential sensing technique for CMOS capacitive fingerprint detection.
- To enhance sensitivity, reduce noise impact, and improve detection speed.
- To overcome limitations of conventional fingerprint sensing architectures.
Main Methods:
- Development of a new capacitive-sensing cell structure featuring charge sharing detection and a readout circuit.
- Implementation of a parasitic insensitive switched-capacitor structure to mitigate parasitic capacitances.
- Utilization of a differential integrator with adjustable integration counts to address finger surface variations.
- Design of an architecture enabling parallel detection across all sensing channels.
Main Results:
- The proposed differential sensing technique demonstrated a significant Signal-to-Noise Ratio (SNR) gain of 54 dB.
- A prototype sensor chip with a 20 × 16 array was implemented using a 130 nm CMOS process.
- Compared to conventional single-line sensing (13 dB SNR gain), the new architecture offers superior performance.
- The parallel detection capability substantially accelerates the fingerprint detection process.
Conclusions:
- The novel differential sensing technique offers a substantial improvement in CMOS capacitive fingerprint detection.
- The architecture effectively enhances sensitivity and overcomes performance degradation issues.
- The parallel processing capability significantly speeds up fingerprint acquisition, making it suitable for advanced biometric systems.
Keywords:
capacitive fingerprint sensorcapacitive-sensingcharge integrationcharge sharing detectiondifferential integratorMore Related Videos
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