UHF Passive RFID Tag Circuit with Analog Sensor Interface
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Solution Overview
Problem
Passive RFID tags operating in the UHF band face limitations in reading distance and system size due to high energy consumption by external sensors with discrete electronics, leading to reduced reading efficiency and longer response times.
Innovation Solution
A circuit design that connects an analog sensor directly to the RFID tag, allowing energy recovery and measurement acquisition during the energy recovery phase, followed by sequential powering of the interface components for measurement amplification and digitization, enabling efficient energy use and reduced response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensors with discrete electronics are connected to the RFID tag via digital interface, then measurement capability is improved, but energy consumption increases and reading distance decreases
Solution Approach 1:
The patent extracts the digital interface and discrete electronics from the sensor system, replacing them with an analog interface that directly connects the sensor to the RFID tag circuit. This removal of unnecessary digital components significantly reduces power consumption while preserving measurement capability.
Solution Approach 2:
The patent changes the interface type from digital to analog, fundamentally altering the electrical parameters of the connection. The analog interface operates at lower voltage and current levels, reducing power consumption from potentially milliwatts to microwatts, thereby extending reading distance.
2Measurement precision
If external sensors with discrete electronics are connected to the RFID tag via digital interface, then measurement capability is improved, but system size increases
Solution Approach 1:
The patent removes the digital interface circuitry, analog-to-digital converters, and associated discrete electronics from the system. This extraction simplifies the overall architecture, reducing both the physical size and component count while maintaining sensor functionality through the direct analog interface.
3Use of energy by moving object
If energy is harvested during the energy recovery phase, then power availability is improved, but reading time increases
Solution Approach 1:
The patent performs energy harvesting during the energy recovery phase, which occurs before the communication phase. This preliminary energy accumulation ensures sufficient power is available when measurements need to be taken, eliminating the need to extend the reading interval and thus not increasing overall reading time.
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 approach allows for extended reading distances up to 3 meters, reduces system size, and enables quick reading of multiple tags by minimizing power consumption and optimizing the energy recovery and communication phases, while ensuring reliable data acquisition and transmission.
Implementation Method 1
These tags use the energy contained in the reader's signal carrier to send a modulated version of the reader's signal back to the RFID reader. At least some of the energy from the interrogation signal is harvested by an energy harvesting device to power the tag's components.
Implementation Method 2
The circuit includes, or is optionally connected via an interface with, a sensor to measure at least certain physical parameters related to this object, such as ambient temperature, humidity, or acceleration.
Data Source
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Figure 3
AI summary
The invention relates to a passive radio identification tag circuit operating in a UHF band, configured for radio communication with a reader that emits a periodic read signal, wherein one period of the read signal comprises an energy recovery phase and a communication phase. The circuit comprises: a control device configured to accumulate an energy reserve from the radio wave during the energy recovery phase and to communicate with the reader during the communication phase, an interface for connecting an external analogue sensor. The interface comprises: an electrical connection configured to connect and supply power to the external analogue sensor and to acquire the analogue measurement of the sensor, an amplifier configured to amplify the signal of the analogue measurement of the sensor, and an analogue-to-digital converter (ADC) configured to digitise the amplified analogue measurement of the sensor, wherein the energy recovery phase comprises an acquisition period during which the interface supplies power to the external analogue sensor, acquires, amplifies and digitises the measurement of the sensor. The invention further relates to a system and a method.