RFID Rectifier Circuit With Mid-Trim Start-Up Matching
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Solution Overview
Problem
RFID tags face performance issues due to manufacturing tolerances and environmental variations, leading to antenna-to-tag mismatch and insufficient energy for initial start-up, which hampers the execution of automatic matching functions.
Innovation Solution
A rectifier circuit with differential stages and a voltage-dependent variable capacitor arrangement provides additional capacitance at start-up to emulate a mid-trimming condition, allowing for efficient energy harvesting and subsequent automatic matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a trimming algorithm is used to automatically adapt the input impedance of the rectifier circuit, then the adaptability of the RFID circuit to different frequencies and impedance conditions is improved, but the start-up capability deteriorates because insufficient voltage is available to initialize the switching functionality of the trimming capacitors
Solution Approach 1:
The patent applies preliminary action by pre-configuring the trimming capacitor arrangement with an initial capacitance value that corresponds to a mid-trim point frequency. This preliminary configuration enables the rectifier circuit to achieve adequate power transfer and generate sufficient voltage before the automatic matching function is activated, thereby resolving the start-up problem while maintaining adaptability.
Solution Approach 2:
The patent utilizes parameter changes by varying the capacitance value of the trimming capacitor arrangement based on the operating conditions. The capacitor arrangement is configured to provide different capacitance values: an initial mid-trim capacitance for start-up, and dynamically adjustable capacitance values during operation to optimize impedance matching across different frequencies.
2Adaptability or versatility
If the trimming capacitor arrangement is configured for extreme frequency trimming, then the adaptability to specific frequency ranges is improved, but the start-up power transfer efficiency deteriorates due to antenna-to-tag mismatch
Solution Approach 1:
The patent applies local quality by configuring different portions of the capacitance adjustment range for different operational phases. The lower portion of the capacitance range (mid-trim region) is optimized for start-up power transfer, while the upper and lower extremes are reserved for frequency adaptation during operation. This localized optimization ensures both efficient start-up and broad frequency adaptability.
Solution Approach 2:
The patent uses preliminary action by pre-setting the trimming capacitor arrangement to a mid-trim capacitance value that maximizes power transfer at the anticipated operating frequency. This preliminary configuration is established before the RFID tag becomes operational, ensuring optimal power transfer efficiency from the moment the tag is activated.
3Device complexity
If no voltage is available at start-up, then the simplicity of the circuit is maintained, but the ability to execute automatic matching function is lost
Solution Approach 1:
The patent applies preliminary action by pre-configuring the trimming capacitor arrangement with an initial capacitance value that enables adequate power transfer during the voltage build-up phase. This preliminary configuration allows the circuit to generate sufficient voltage to initialize the automatic matching function without requiring additional complex start-up circuitry.
Solution Approach 2:
The patent utilizes self-service by designing the trimming capacitor arrangement to automatically provide the necessary capacitance for voltage build-up and initialization of the automatic matching function. The capacitor arrangement serves dual purposes: it enables start-up power transfer and subsequently supports the automatic frequency matching process without requiring external intervention or additional components.
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 enables faster and more efficient energy harvesting and reduces tag antenna mismatch, ensuring successful initiation of the RFID circuit's automatic matching function.
Implementation Method 1
A voltage dependent variable capacitor arrangement is connected to the first stage input and connected to the second stage input. By way of the voltage dependent variable capacitor arrangement there is provided an additional or an excess capacitance, which is available directly at the start of the RFID circuit or rectifier circuit
Implementation Method 2
harvesting electrical energy from the external RF field
Implementation Method 3
By way of the trimming capacitor arrangement, the resonance frequency of the rectifier circuit can be modified electronically
Data Source
AI summary
A rectifier circuit (10) for a passive RFID circuit (1), including: a first rectifier stage (11) having a positive stage input (14) connectable to a first antenna port (6) and a negative stage input (15) connectable to a second antenna port (7); a first rectifying unit (12) connected to the positive stage input (14) and to a positive stage output (16); a second rectifying unit (18) connected to the negative stage input (15) and to a negative stage output (17); and a trimming capacitor (30) connected to the positive stage input (14) and to the negative stage input (15). The trimming capacitor (30) is electronically switchable to a first capacitance and to a second capacitance, and a voltage dependent variable capacitor (50) is connected to the positive stage input (14) and to the negative stage input (15).