RFID Tag Amplitude Limiting Latch for Leakage-Free Discharge Control
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Solution Overview
Problem
Passive RFID tags face issues with voltage overload and signal saturation due to varying electromagnetic field strengths, leading to device damage and communication failures, and existing amplitude limiting circuits struggle to optimize amplitude limiting range and discharge path capability simultaneously.
Innovation Solution
A positive feedback latch amplitude limiting control circuit is introduced, comprising a signal generating circuit, signal processing circuit, and discharge circuit, which dynamically controls the discharge path based on magnetic field strength, using a MOS transistor with a latch-controlled gate voltage to prevent sub-threshold leakage and optimize power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amplitude limiting magnitude voltage is set high to protect devices under strong field conditions, then device reliability is improved, but leakage current increases under weak field conditions causing energy loss
Solution Approach 1:
The patent implements dynamic adjustment of the discharge path threshold voltage based on operating conditions. The amplitude limiting circuit dynamically changes its triggering threshold between a first threshold voltage (higher) for strong field conditions and a second threshold voltage (lower) for weak field conditions, allowing optimal performance across different operating ranges rather than using a fixed threshold
Solution Approach 2:
The patent changes the threshold voltage parameter of the discharge path based on field strength conditions. By detecting the amplitude of the received signal and adjusting the threshold voltage accordingly, the system adapts the discharge triggering point to match operating conditions, reducing leakage current in weak fields while maintaining protection in strong fields
2Reliability
If the discharge path is designed large to provide sufficient discharge capability under strong field conditions, then voltage protection is improved, but leakage current increases under weak field conditions reducing communication distance
Solution Approach 1:
The patent makes the discharge path capability dynamic by adjusting the threshold voltage based on field strength. Under strong field conditions, the higher threshold allows the discharge path to activate and provide necessary voltage protection. Under weak field conditions, the lower threshold prevents premature activation, minimizing leakage current and extending communication distance
Solution Approach 2:
The patent changes the operating parameter (threshold voltage) of the discharge path to match field conditions. This parameter adjustment allows the same discharge path structure to provide adequate protection capability when needed while minimizing its negative impact on communication performance when not needed
3Loss of energy
If the amplitude limiting magnitude voltage is set low to reduce leakage current under weak field conditions, then energy loss is reduced, but discharge timing is delayed under strong field conditions risking device damage
Solution Approach 1:
The patent dynamically adjusts the discharge threshold voltage based on detected field strength. When weak fields are detected, a lower threshold reduces leakage current. When strong fields are detected, a higher threshold ensures timely discharge activation to protect devices, eliminating the need to choose between these conflicting requirements
4Device complexity
If a fixed threshold voltage is used in the amplitude limiting circuit, then circuit simplicity is maintained, but optimal performance under both strong and weak field conditions cannot be achieved
Solution Approach 1:
The patent introduces dynamic threshold adjustment capability to the amplitude limiting circuit while maintaining reasonable structural simplicity. The threshold voltage is changed based on operating conditions, allowing the circuit to adapt to both strong and weak field environments and achieve optimal performance across different operating ranges
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 solution effectively reduces leakage current, enhances communication performance, and extends communication distance by ensuring the discharge path is fully turned off during weak field conditions and turned on during strong field conditions, thereby improving the energy management and reliability of passive RFID tags.
Implementation Method 1
the rectifier circuit rectifies the alternating current into a direct current
Implementation Method 2
the discharge circuit is turned on, and the voltage at the antenna terminal is discharged to the ground
Data Source
AI summary
A positive feedback latch amplitude limiting control circuit and method of the passive radio frequency identification tag of the present disclosure dynamically control the voltage between the first and the second antenna terminal. When the voltage between the antenna terminals is too high, the signal generating circuit turns on the discharge circuit, which reduces the rectified DC voltage. When the voltage between the antenna terminals is within the limited voltage, the signal generating circuit turns off the discharge circuit. The discharge circuit in the present disclosure includes a MOS transistor whose gate voltage is indirectly controlled by a latch. A positive feedback mechanism of the latch makes the first control signal S1 have a substantially strong strength when being pulled to a low level, such that the discharge path is fully turned off, which avoids a discharge of the MOS transistor being in a sub-threshold region, thereby improving communication performance.