RFID Tag Power Rectifier Bias Circuit for Low Signal Harvesting
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Solution Overview
Problem
Passive RFID tags face challenges in generating sufficient power from low-level RF signals, requiring efficient rectification and boosting mechanisms to operate, especially since the RF signal is not constantly available and needs to support high-voltage operations like memory programming.
Innovation Solution
The implementation of a power management unit with successive stages of switching transistors and bias voltage application to enhance rectification efficiency, utilizing alternating signal phases to generate rectified voltage, and employing charge pump circuits for boosted voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If passive RFID tags use rectifier circuits to convert RF signals to DC voltage, then power can be generated from the RF signal, but the rectified voltage may be insufficient to meet the operating voltage requirements of the tag circuits
Solution Approach 1:
The patent implements a voltage regulator circuit that dynamically adjusts its operation based on the rectified voltage level and power consumption requirements. The regulator includes control logic that monitors the voltage from the rectifier circuit and adjusts the power delivery accordingly, enabling the system to adapt to varying voltage conditions and ensure reliable operation even when rectified voltage fluctuates
Solution Approach 2:
The system changes operating parameters by adjusting the impedance matching between the rectifier and the tag circuitry based on detected voltage levels. The patent modifies electrical parameters such as resistance and capacitance values dynamically to optimize power transfer efficiency and ensure sufficient voltage delivery under different operating conditions
2Ease of operation
If the RFID tag uses a battery as a power storage device, then the tag can operate independently, but the tag size and complexity increase
Solution Approach 1:
The patent implements a power management system that enables the RFID tag to harvest and store energy autonomously from the RF signal environment. The system includes energy harvesting circuitry and a small energy storage element that work together to capture ambient RF energy and store it for later use, allowing the tag to operate independently without requiring an external battery or power source
Solution Approach 2:
The patent extracts the power storage function from a traditional battery and replaces it with an energy harvesting and storage system that uses minimal components. By taking out the battery and replacing it with RF energy harvesting circuitry and a small capacitor or supercapacitor, the system achieves independent operation while dramatically reducing size and complexity
3Loss of energy
If the RF signal is not constantly transmitted by the reader, then energy consumption is reduced, but the RFID tag cannot continuously harvest power
Solution Approach 1:
The patent implements an energy storage mechanism that accumulates harvested energy in advance during periods when RF signals are available. The system stores this energy in a capacitor or supercapacitor, creating a power reserve that can be drawn upon when the reader does not transmit, ensuring continuous operation and bridging the gaps between RF signal transmissions
Solution Approach 2:
The power management circuit maintains continuous power availability by seamlessly switching between harvested RF power and stored energy. The system ensures uninterrupted operation by keeping the energy storage element charged during RF signal presence and automatically drawing from storage during absence, maintaining continuous useful action without interruption
4Adaptability or versatility
If high voltage is needed for memory programming and erasing operations, then functionality is enhanced, but the rectifier circuit must generate significantly higher voltage from the low-level RF signal
Solution Approach 1:
The patent segments the voltage generation process into multiple stages: a rectifier circuit that converts RF to a preliminary DC voltage, followed by a voltage booster circuit that elevates this to the high voltages needed for memory operations. This segmentation allows each circuit to be optimized for its specific function, with the rectifier handling power conversion and the booster handling voltage elevation, reducing overall complexity
Solution Approach 2:
The patent introduces an intermediary voltage level between the low-voltage RF signal and the high-voltage memory operations. The rectifier first converts RF to a moderate DC voltage, which then serves as an intermediate step before the voltage booster generates the final high voltage. This intermediary approach simplifies the voltage conversion process compared to direct high-voltage generation
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 passive RFID tags to efficiently convert low-level RF signals into usable DC voltage, ensuring reliable operation even when the RF signal is intermittent and supporting high-voltage requirements, thereby improving the functionality and reliability of RFID systems.
Implementation Method 1
a first phase of the alternating signal is coupled to a gate and to a first non-controlling terminal of a first switching transistor... A first bias voltage is applied between the first non-controlling terminal and the first gate of the first switching transistor and a rectified voltage is received between the first non-controlling terminal and a second non-controlling terminal
Data Source
AI summary
A system and method for generating a rectified signal in a RFID tag. An alternating signal is received by the RFID tag, and a first phase of the alternating signal is coupled to a gate and to a first non-controlling terminal of a first switching transistor. The non-controlling terminal of the first switching transistor is one of a source and a drain of the first switching transistor. A first bias voltage is applied between the first non-controlling terminal and the gate of the first switching transistor and a rectified voltage is received between the first non-controlling terminal and a second non-controlling terminal of the first switching transistor.