RF Tag Impedance Adjustment via Variable Load Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
RF tags with matching circuits and voltage limiters face challenges in adjusting impedance to optimal values due to environmental changes, leading to power supply voltage drops below operational limits, preventing stable operation.
Innovation Solution
An RF tag with a variable load unit and control unit that adjusts impedance by reducing the output voltage of the rectification circuit below the limiter voltage, allowing for satisfactory impedance adjustment of the matching circuit, even when power input drops, ensuring stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a limiter is added to prevent excessive voltage application to circuits, then circuit reliability is improved, but the impedance of the matching circuit cannot be adjusted to the optimal value
Solution Approach 1:
The patent applies preliminary action by adjusting the impedance of the matching circuit to its optimal value before the limiter becomes active. The control unit performs impedance adjustment by varying the variable capacitor value, and only after optimal impedance is achieved does the limiter engage to prevent excessive voltage. This sequence ensures both optimal circuit performance and protection against voltage damage.
2Device complexity
If the impedance of the matching circuit is not adjusted to an optimal value, then device complexity is reduced, but the power supply voltage becomes equal to or lower than the operation lower limit voltage under environmental changes
Solution Approach 1:
The patent implements dynamics by making the matching circuit impedance adjustable through a variable capacitor controlled by a control unit. The impedance can be dynamically optimized based on operating conditions, environmental changes, and input power levels. This dynamic adjustment capability allows the system to maintain stable power supply voltage despite variations in the operating environment.
3Ease of operation
If the output voltage of the rectification circuit is directly detected for impedance adjustment, then adjustment process simplicity is improved, but the impedance cannot be adjusted to optimal value when a limiter is present
Solution Approach 1:
The patent employs feedback by using a detector to monitor the output voltage of the rectification circuit and feeding this information back to the control unit. The control unit uses this feedback to iteratively adjust the variable capacitor value, optimizing the matching circuit impedance. This feedback mechanism enables accurate impedance adjustment even in the presence of a limiter, as the system can detect voltage changes and make precise adjustments accordingly.
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
The RF tag effectively adjusts the impedance of the matching circuit to optimal values, maintaining stable power supply and operation even under environmental changes or power input reductions, enhancing robustness in radio communication systems.
Implementation Method 1
an RF tag (10) that receives power wirelessly from a reader/writer (85)
Implementation Method 2
a rectification circuit (13) that rectifies an AC signal supplied from an antenna (20) and outputs a DC voltage
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
An RF tag (10) that includes a limiter (16) and is capable of satisfactorily adjusting an impedance of a matching circuit (11) is provided. The RF tag (10) includes a variable load unit (21) of which an amount of power consumption is changeable and a control unit (18) that is capable of executing an impedance adjusting process of adjusting the impedance of the matching circuit (11) such that an output voltage of a rectification circuit (13) becomes a maximum and executes the impedance adjusting process after reducing the output voltage of the rectification circuit (13) to a voltage less than a limiter voltage by adjusting the amount of power consumption of the variable load unit (21) when a predetermined condition is satisfied.