Embedded Antenna Fingerprint Sensor for Smart Card Power
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Solution Overview
Problem
Fingerprint sensors in smart cards face challenges due to cost constraints and limited power availability, requiring more efficient and cost-effective integration solutions compared to smartphone applications.
Innovation Solution
A fingerprint sensor module with an embedded RFID or NFC antenna that harvests energy from radio waves, eliminating the need for an external power supply and simplifying the manufacturing process by integrating the antenna within the substrate, which can encircle or be located below the sensor device, optimizing area utilization and signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external power supply is used for the fingerprint sensor module, then the sensor can be powered reliably, but the cost and complexity increase
Solution Approach 1:
The fingerprint sensor module harvests power from ambient radio frequency signals through the embedded antenna, enabling it to power itself without external power supply connections. This self-powered operation eliminates the need for separate power supply circuits and reduces overall system complexity while maintaining reliable operation.
Solution Approach 2:
The embedded antenna serves dual functions: it acts as both the communication antenna for RFID/NFC operations and as the power harvesting element for the fingerprint sensor. This multi-functionality eliminates the need for separate power supply infrastructure, reducing both cost and complexity.
2Area of stationary object
If the antenna is integrated within the substrate, then the area utilization is optimized and manufacturing is simplified, but the signal strength may be reduced
Solution Approach 1:
The antenna is nested within the substrate structure, with the fingerprint sensor device positioned within the antenna loop. This nested configuration allows the antenna to encircle the sensor opening, maximizing area utilization while maintaining adequate signal strength through the loop geometry.
Solution Approach 2:
The antenna is positioned on the opposite side of the substrate from the sensor array, utilizing the third dimension (depth/thickness) rather than competing for surface area. This vertical separation maintains signal strength while optimizing horizontal area utilization.
3Device complexity
If the fingerprint sensor waits for power from the controller chip, then power management is simplified, but the initialization time increases
Solution Approach 1:
The fingerprint sensor module performs preliminary power-up and initialization using harvested RF energy before the controller chip is ready to provide power. This preliminary action enables the sensor to be fully initialized and ready to operate as soon as the controller chip becomes available, eliminating waiting time.
4Reliability
If a separate antenna is fabricated on the smart card, then the signal strength is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The antenna function is merged with the substrate structure of the fingerprint sensor module itself, rather than being a separate component on the smart card. This integration eliminates the need for separate antenna fabrication processes on the card and simplifies the overall manufacturing workflow.
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 power-up of the fingerprint sensor module independently of the smart card's controller chip, reduces manufacturing complexity, and enhances area efficiency, making it suitable for cost-sensitive smart card applications while maintaining effective functionality.
Implementation Method 1
the antenna may be an RFID (Radio-frequency identification) antenna configured to communicate with a corresponding RFID device and also to provide power to the fingerprint sensor module by harvesting energy from radio waves transmitted by an RFID reader
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3E
AI summary
There is provided a fingerprint sensor module (100, 400) comprising a fingerprint sensor device (102). The fingerprint sensor device (102) comprises a sensing array (104) consisting of a plurality of sensing elements, the sensor device being configured to acquire an image of a finger placed on a sensing surface of the fingerprint sensor module. The fingerprint sensor module (100, 400) further comprises a substrate (108) comprising an opening (110, 401), wherein the fingerprint sensor device is arranged in the opening of the substrate and wherein the substrate comprises an antenna (112, 402) embedded in the substrate, the antenna being electrically connected to the fingerprint sensor device.