RF Tag Matching Circuit for Unstable Power Impedance Tuning
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Solution Overview
Problem
Existing RF tag circuits face challenges in impedance adjustment, particularly when the power supplied is unstable, making it difficult to ensure stable operation of loads such as sensors, LEDs, or microcomputers, due to impedance mismatch between the antenna and the RF tag circuit.
Innovation Solution
The RF tag circuit incorporates a rectification circuit, a matching circuit with variable impedance, and a control part that repeatedly activates and stops the load to adjust the impedance based on the comparison of initial and subsequent power levels, allowing for impedance matching even when power is unstable, using a rectification circuit, a matching circuit with variable impedance, and a control system that adjusts the impedance based on power comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance adjustment is performed when the load is not driven, then the voltage is saturated and the adjustment cannot be detected, but if the load is driven, then the electric power is consumed and the adjustment period is extended
Solution Approach 1:
The patent implements periodic impedance adjustment by controlling the load to operate in cycles (driving period and stopping period). During each cycle, the impedance is adjusted when the load is stopped, and the adjustment is evaluated when the load is driven. This periodic operation allows the system to perform impedance adjustment without requiring continuous load operation, thus reducing the overall adjustment period while maintaining detection accuracy.
2Stability of the object's composition
If the load driving period is extended to allow power stabilization, then the time until electric power is stabilized is secured, but loads that can be driven in shorter periods cannot utilize their full capability
Solution Approach 1:
The patent applies preliminary action by performing impedance adjustment during the load stopping period before the next driving period begins. The controller adjusts the impedance of the matching circuit in advance during the stopping period, and by the time the load starts driving again, the impedance is already optimized. This allows the system to maintain power stability without extending the actual load driving period, as the adjustment is prepared beforehand.
3Use of energy by moving object
If the impedance of the matching circuit is changed frequently to optimize power, then the power efficiency is improved, but the circuit complexity and adjustment overhead increase
Solution Approach 1:
The patent implements feedback control where the controller monitors the power generated by the rectification circuit during the load driving period and uses this information to adjust the impedance during the subsequent stopping period. The controller compares the detected power level with expected values and adjusts the matching circuit impedance accordingly. This feedback mechanism allows the system to optimize power efficiency through intelligent, data-driven impedance adjustment rather than frequent blind adjustments, reducing unnecessary complexity.
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 configuration enables the RF tag circuit to detect and adjust impedance mismatch in real-time, ensuring stable power supply to loads even when the power is unstable, thereby improving the efficiency and reliability of load operation.
Implementation Method 1
a rectification circuit that rectifies a radio wave received by the antenna and supplies DC power
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An RF tag circuit connected to an antenna and a load is provided. The RF tag circuit includes: a rectification circuit rectifying a radio wave received by the antenna and supplying DC power; a matching circuit having a changeable impedance and disposed between the antenna and the rectification circuit; a control part repeatedly controlling activation and stopping of the load; and an adjustment part changing the impedance of the matching circuit in a predetermined direction, storing a first electric power generated by the rectification circuit when a predetermined time has elapsed after the load is activated, and changing the impedance of the matching circuit based on a magnitude relationship between a second electric power generated by the rectification circuit when the predetermined time has elapsed after the load is activated at a timing after the first electric power is generated and the stored first electric power.