Dual Buffer Capacitor Layout for Faster RFID Tag Boot
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Solution Overview
Problem
Passive RFID tags face challenges in booting up quickly and reliably due to the time required for autonomous impedance matching and the need for a larger buffer capacitor, which slows down the charging process in limited RF protocols.
Innovation Solution
A system comprising an energy harvesting circuit, a buffer capacitor, and an auxiliary capacitor, where the auxiliary capacitor is charged during the autonomous matching procedure, allowing the system to start matching earlier and providing additional capacitance after matching is complete, reducing the overall charging time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a larger buffer capacitor is used to extend operation during RF field deficiencies, then the tag can operate longer without RF field, but the charging time increases which reduces boot speed
Solution Approach 1:
The buffer capacitor is divided into two separate capacitors: a first buffer capacitor (C1) that charges quickly during autonomous matching, and a second buffer capacitor (C2) that charges afterward to provide extended operation. This segmentation allows the system to achieve both fast booting and long operation duration by separating the charging phases of the two capacitors.
2Reliability
If autonomous matching procedure is executed first, then antenna matching is optimized, but the tag cannot boot quickly because the large buffer capacitor takes too long to charge
Solution Approach 1:
The system performs preliminary charging of the first buffer capacitor (C1) to a first voltage level before completing the autonomous matching procedure. This preliminary action ensures that enough energy is available to support the matching process and enable quick booting, while the second capacitor (C2) is charged afterward to provide extended operation capability.
3Reliability
If the buffer capacitor is charged to maximum level before autonomous matching, then sufficient energy is available for matching, but the charging time is excessive and reduces protocol efficiency
Solution Approach 1:
Instead of charging the entire buffer capacitance to maximum level before autonomous matching, the system only charges the first buffer capacitor (C1) to a sufficient first voltage level that provides adequate energy for the matching process. The second capacitor (C2) is charged to a second voltage level after matching is complete, providing partial charging in advance and avoiding excessive charging time that would reduce protocol efficiency.
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 faster and more reliable booting of RFID tags by initiating the autonomous matching procedure earlier and providing a larger effective capacitance for extended operation during RF field deficiencies, improving energy efficiency and sensitivity.
Implementation Method 1
The capacitor stores energy when there is excess RF energy and releases energy when there is a deficit of RF energy
Implementation Method 2
The control circuit comprises an auxiliary capacitor, which is chargeable during execution of the autonomous matching procedure
Data Source
Figure 1~3
Figure 4~6
AI summary
The disclosure concerns a system (10) comprising: - an energy harvesting circuit (12) connectable to an antenna (14) and configured to execute an autonomous matching procedure to match the antenna (14) to an electric load (15), - a buffer capacitor (16) connected to the energy harvesting circuit (14) and chargeable by the energy harvesting circuit (14), - a control circuit (20) connected to the energy harvesting circuit (14) and to the buffer capacitor (16) and connectable to the electric load (15), wherein the control circuit (20) is configured to control a supply voltage of the electric load (15), and - wherein the control circuit (20) comprises an auxiliary capacitor (22) chargeable during execution of the autonomous matching procedure.