Dual Buffer Capacitor Layout for Faster RFID Tag Boot-Up
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Solution Overview
Problem
Passive RFID tags face challenges in booting up quickly and reliably due to the time required to ramp up the supply voltage and match the energy harvesting circuit with the antenna, especially with limited continuous wave (CW) RF field availability and the need for a larger buffer capacitor that slows down the charging process.
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 the matching process earlier and providing additional capacitance after matching is complete, reducing the size of the buffer capacitor and optimizing energy harvesting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a larger buffer capacitor is used to extend operation time during low RF field conditions, then the operation duration is improved, but the charging time increases which slows down the boot-up process
Solution Approach 1:
The buffer capacitor is divided into two separate capacitors: a first buffer capacitor that charges quickly during the autonomous matching procedure, and a second buffer capacitor that charges afterward. This segmentation allows the system to achieve both fast boot-up (using the first capacitor) and extended operation duration (using both capacitors together), resolving the contradiction between charging time and operation duration.
2Reliability
If the autonomous matching procedure is delayed to allow complete charging of the buffer capacitor, then the charging completeness is improved, but the boot-up time increases
Solution Approach 1:
The system performs preliminary charging of the first buffer capacitor before the autonomous matching procedure completes. This preliminary action ensures that sufficient charge is available to start the matching procedure without delay, while the second buffer capacitor continues to charge in the background, maintaining both boot-up speed and charging completeness.
Solution Approach 2:
The system dynamically switches between different capacitor configurations during operation. Initially, it uses only the first buffer capacitor for fast response during boot-up, then transitions to using both capacitors for extended operation. This dynamic approach allows the system to optimize performance at different stages of operation.
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
This solution enables faster boot-up and reliable operation of RFID tags by initiating the autonomous matching procedure earlier and utilizing excess energy for efficient charging, reducing the time to reach operational voltage and extending operation time during low RF field conditions.
Implementation Method 1
The purpose of the buffer capacitor is to provide an energy reservoir allowing the tag to continue to operate when the RF field is not present such as during modulation, backscatter, or low RF field conditions. 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 further comprises an auxiliary capacitor, which is chargeable during execution of the autonomous matching procedure. In a function mode of the system and in particular after completion of the autonomous matching procedure, the auxiliary capacitor may act and behave as a supplemental buffer capacitor
Data Source
AI summary
A system (10) including 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), and 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.