Metal environment self-adaptive RFID tag system based on dual-frequency cooperative energy supply and temperature sensing

Abstract

The invention discloses a metal environment adaptive RFID tag system based on dual-frequency cooperative energy supply and temperature sensing, which adopts a three-layer modular architecture design, comprises an energy input layer, a temperature sensing layer and a data fusion transmission layer, and integrates a dynamic energy management strategy and a metal environment enhancement design. The energy input layer adopts dual-frequency cooperative energy supply, comprises a low-frequency energy capture module, an ultrahigh-frequency energy capture module and a self-adaptive switching controller, can automatically switch modes according to the environment, and improves the energy capture efficiency of the metal surface; the temperature sensing layer is provided with a digital temperature sensor and an intelligent sampling control module, supports wide temperature measurement, can intelligently adjust a sampling mode, and balances performance and power consumption; the data fusion transmission layer adopts a double-channel anti-interference modulation technology, identity (ID) and temperature data are transmitted in a separated mode, communication reliability is improved, and a coding protocol extension module can accurately represent temperature information. The method can adapt to different environmental conditions, widens the application range of the tag, and ensures that the tag can stably and efficiently obtain energy in various complex scenes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of intelligent radio frequency identification, and relates to a metal environment adaptive RFID tag system based on dual-frequency cooperative power supply and temperature sensing. BACKGROUND

[0002] With the rapid development of the Internet of Things technology, RFID (Radio Frequency Identification) technology as a key component has been widely used in identity recognition, logistics tracking, asset management and many other fields. Traditional RFID tags mainly realize identity recognition function based on a single frequency band (such as UHF 860-960MHz), and comply with EPC C1G2 (ISO 18000-6C) standard. However, in actual application, especially in metal environment, traditional RFID technology exposes many significant defects.

[0003] Under the metal environment, the eddy current effect generated by the metal surface will cause the antenna impedance mismatch, which seriously affects the energy capture efficiency. According to the ISO / IEC 18046-3 electromagnetic compatibility test standard, the energy capture efficiency of traditional RFID tags in metal environment is less than 30%. At the same time, the problem of multipath interference caused by signal reflection is also very prominent, which makes the reading success rate drop to below 70%, greatly limiting the application of RFID technology in metal related scenarios.

[0004] In the aspect of temperature measuring RFID tags, the existing technology mostly adopts the external battery scheme, such as TI SensorTag CC2650. Although this scheme can realize temperature collection function, it has obvious disadvantages. On the one hand, in the metal environment, the battery endurance will be seriously affected by electromagnetic shielding, with a decay amplitude of up to 70%, resulting in a significant reduction in device usage time. On the other hand, active devices do not conform to the development trend of low-cost and long-life passive RFID, increasing the use cost and maintenance difficulty.

[0005] The passive RFID temperature measurement scheme is an important direction of current research, which mainly relies on backscatter modulation technology. For example, in the EPC C1G2 standard, the temperature is indirectly calculated by carrier frequency offset. However, this temperature measurement method has a large error, with a measurement error of ±2℃. In high-end application scenarios such as medical cold chain and electronic chip manufacturing, the requirement for temperature precision is very high, with ±0.5℃ precision required for medical cold chain and ±0.3℃ precision required for electronic chip manufacturing. The existing passive RFID temperature measurement scheme obviously cannot meet these requirements. In addition, the energy management strategy of traditional passive tags is relatively single. When the super capacitor voltage is lower than 2.0V, the temperature measurement module will be forced to stop working due to insufficient power supply, resulting in interruption of data collection and inability to realize continuous and stable temperature monitoring.

[0006] Based on the above analysis, the existing RFID technology and temperature sensing technology have the following pain points: Single function: the function of traditional tags is limited, only ID identification is supported, and environmental parameters such as temperature cannot be synchronously obtained, which is difficult to meet the comprehensive monitoring demand in multiple scenes. The active temperature measurement tag relies on a battery, which goes against the development direction of passivity, and increases the cost and use limitation.

[0007] Poor metal adaptability: the energy capture efficiency of ordinary tags on the metal surface is low, which leads to unstable power supply of the temperature measurement module, the sampling interval exceeds 5 minutes, and real-time monitoring of metal environment or metal-related objects cannot be realized, which limits its application in metal-intensive fields such as metal industry and aerospace.

[0008] Insufficient temperature measurement accuracy: the passive backscattering temperature measurement scheme is affected by multipath interference and energy fluctuation, and the measurement error exceeds the industrial application standard, which cannot meet the production and management demand of industries with extremely high temperature precision requirements such as medicine and electronic chip manufacturing. SUMMARY

[0009] The purpose of the present application is to solve the problems of low energy capture efficiency of traditional RFID tags in metal environment, unstable power supply of temperature measurement module, insufficient temperature measurement accuracy and single function in the prior art, and to provide a metal environment adaptive RFID tag system based on dual-frequency collaborative energy supply and temperature sensing.

[0010] To achieve the above purpose, the following technical solutions are adopted: The metal environment adaptive RFID tag system based on dual-frequency collaborative energy supply and temperature sensing adopts a three-layer modular architecture design, including an energy input layer, a temperature sensing layer and a data fusion transmission layer, and integrates a dynamic energy management strategy and a metal environment enhancement design; wherein: The energy input layer adopts a dual-frequency collaborative energy supply mechanism, including a low-frequency energy capture module, an ultra-high frequency energy capture module and an adaptive switching controller; wherein the low-frequency energy capture module adopts an LC resonant circuit with a resonant frequency of 125 kHz, and is configured with a magneto-electric composite antenna; the ultra-high frequency energy capture module integrates an impedance adjustable loop antenna; the adaptive switching controller is based on an LTC3588-1 energy management IC, and has a built-in environment electromagnetic intensity detection module; when in a metal surface environment and the metal surface magnetic field intensity > 5 μT, the adaptive switching controller automatically switches to a low-frequency dominant mode, the low-frequency energy proportion ≥ 75%, and the magneto-electric composite antenna of the low-frequency energy capture module enhances the magnetic field coupling through the magnetic core to improve the metal surface energy capture efficiency; when in a non-metal environment, the UHF band works preferentially, and the ultra-high frequency energy capture module plays a role, and its integrated impedance adjustable loop antenna dynamically adjusts the impedance through a switch type matching network according to the metal distance, and improves the data transmission rate through backscattering modulation; The temperature sensing layer comprises a digital temperature sensor and an intelligent sampling control module; wherein the digital temperature sensor supports a range of -40℃ to 125℃ and is built-in with a 16-bit ADC; the intelligent sampling control module intelligently controls and dynamically adjusts according to different super capacitor voltages, and its working modes include a real-time mode, a regular mode and an energy-saving mode; The data fusion transmission layer adopts a double-channel anti-interference modulation technology and is composed of an encoding protocol expansion module and a double-channel modulation module; wherein the encoding protocol expansion module is based on a 96-bit ID encoding of the EPC C1G2 standard, expands 8-bit temperature data by using reserved bits, the temperature range is -40℃ to 125℃, the step is 0.5℃, and a CRC-8 check code generation and detection function is provided, the CRC-8 check code is generated and attached to the transmission at the data sending end, and the CRC-8 check code is calculated and compared with the received check code at the data receiving end; the double-channel modulation module comprises two independent modulation channels, one channel is used for transmitting the identity ID through the UHF frequency band by using the ASK modulation mode and meets the ISO 18000-6C standard; the other channel is used for transmitting the temperature data through the low frequency band by using the PSK modulation mode, and the identity ID and the temperature data are independently and stably transmitted in different frequency bands and modulation modes.

[0011] The magnetoelectric composite antenna is composed of a ferrosilicon aluminum magnetic core with a thickness of 0.3 mm and a relative magnetic permeability of 200, a flexible ferrite substrate with a loss tangent <0.01 and a nanometer silver mesh radiator with a line width of 50 μm, and the antenna quality factor Q value is >60.

[0012] The intelligent sampling control module dynamically adjusts according to the super capacitor voltage V_cap. When V_cap>2.8V, the real-time mode is entered, the 16-bit ADC is started to sample data, the temperature is measured once per second + the double-channel real-time transmission; When 2.2V≤V_cap≤2.8V, the regular mode is entered, the 12-bit ADC is switched to sample, and the sampling interval is dynamically adjusted according to V_cap; When V_cap<2.2V, the energy-saving mode is entered, the temperature measurement is stopped, only the energy harvesting module and the adaptive controller work, and when V_cap rises to 2.2V, the temperature sampling is automatically woken up and reselected according to the V_cap value.

[0013] In the regular mode, the sampling interval is dynamically adjusted according to V_cap, and the adjustment formula is T_sample = 10×(2.5 - V_cap)+10 seconds.

[0014] The dynamic energy management strategy is provided with three-level energy storage units, specifically: The transient buffer layer selects a super capacitor with a specification of 2.7V / 100mF and an equivalent series resistance less than 50mΩ and a response time less than 5ms as a core energy storage element, for capturing high-frequency transient energy in the system operating environment; The main energy storage layer adopts a 3.0V / 10mAh thin film lithium battery with a volume of 10mm×8mm×1.5mm as an energy storage element, as the main energy storage unit of the system, continuously receiving external power energy input and converting it into chemical energy storage to provide energy guarantee for long-time operation of the system; under normal temperature conditions, when the system is in a dormant state or the external power is interrupted, stable power is provided for the system memory; The emergency backup layer selects a 0.1F gold capacitor with a working temperature range of -55℃~125℃ as an energy storage element, which can guarantee the system to complete the last data upload when the main power fails, and improve the system reliability and data security.

[0015] The metal environment enhancement design includes optimization of the composite antenna structure, specifically: The three-layer material design uses a μ = 200 iron-silicon-aluminum magnetic core in the bottom layer, which uses its high permeability to converge magnetic lines of force, enhance the magnetic induction intensity of the antenna, and improve the receiving and transmitting ability of low-frequency electromagnetic signals; the middle layer is a flexible ferrite substrate with a dielectric constant ε = 15, which is flexible and easy to install on different shaped metal surfaces, and can adjust the electromagnetic properties of the antenna to achieve impedance matching and resonant frequency adjustment, so that the antenna works well in a metal environment; the top layer is a nano silver mesh radiator with a square resistance <0.1Ω / □, which has low resistance characteristics and can efficiently radiate and receive electromagnetic waves, reducing energy loss, and its grid structure can adapt to the deformation of the metal surface, ensuring the stability of the antenna; The dual-band isolation technology is adopted, the low-frequency coil has an inner diameter of 8mm, an outer diameter of 12mm, and is provided with 5 turns, the UHF radiator and the low-frequency coil are arranged at 90°, and the distance between them is optimized to 2mm through electromagnetic simulation, so that the coupling coefficient is <0.05, realizing effective isolation of the low-frequency band and the UHF band, and ensuring independent work of the two frequency bands without interference.

[0016] The specific working mode of the composite antenna includes: Low-frequency working mode: when external low-frequency electromagnetic signals reach the antenna, the bottom layer iron-silicon-aluminum magnetic core first senses the signals and converges magnetic lines of force to enhance the magnetic field strength, the low-frequency coil generates an induced electromotive force in the changing magnetic field to convert the electromagnetic signals into electrical signals, and the middle layer flexible ferrite substrate adjusts the impedance of the low-frequency coil to match the signal source, improving the signal reception efficiency; UHF operating mode: For UHF band signals, the top layer of nano-silver mesh radiator acts as the main radiating and receiving element, converting electromagnetic waves into current signals, and interacting with the middle layer of flexible ferrite substrate to achieve impedance matching and signal transmission.

[0017] The metal environment enhancement design includes thermal coupling and thermal isolation, specifically: Temperature measurement point optimization: The temperature sensor is directly mounted on the metal surface contact point using thermally conductive silicone with a thermal conductivity of 3.5 W / m・K and a thickness of 0.2 mm. According to the thermal resistance calculation formula R_th = δ / λ, where δ is the thickness of the thermally conductive silicone and λ is the thermal conductivity of the thermally conductive silicone, the thermal resistance R_th = 0.2 mm / 3.5 W / m・K = 0.057 ℃ / W, ensuring that the temperature difference between the sensor and the metal surface is <0.1 ℃. The thermal isolation structure separates the antenna area from the sensing area through a polyimide thermal insulation layer, reducing heat transfer from the antenna area to the sensing area. Combined with a temperature difference compensation algorithm based on BP neural network training, the sensor measurement values ​​are corrected by input parameters of antenna current and ambient temperature, and the thermal crosstalk error is controlled to be less than 0.2℃.

[0018] The temperature measurement point is where heat is rapidly transferred to the temperature sensor through thermally conductive silicone when the metal surface temperature changes. The temperature sensor converts the temperature change into an electrical signal and transmits it to the subsequent data processing module. The low thermal resistance of the thermally conductive silicone enables the temperature sensor to reflect the metal surface temperature in real time and accurately, providing reliable data support for the system's temperature sensing function.

[0019] The thermal isolation structure uses a polyimide thermal insulation layer as a thermal barrier to reduce the transfer of heat generated by the current during antenna operation to the sensing area. A 0.5mm thick polyimide thermal insulation layer with a thermal conductivity of 0.15W / m・K is used for separation. The temperature difference compensation algorithm based on the BP neural network dynamically corrects the sensor measurement value according to the antenna current and ambient temperature, eliminates the influence of thermal crosstalk, and ensures accurate temperature measurement.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing in this invention adopts a dual-frequency collaborative power supply mechanism to achieve dynamic allocation of low-frequency and ultra-high-frequency energy. In specific environments with metal surfaces and magnetic field strength exceeding 5μT, the system can automatically switch to a low-frequency dominant mode, where the low-frequency energy accounts for no less than 75%. By leveraging the enhanced magnetic field coupling characteristics of the magnetic core of the magneto-electric composite antenna in the low-frequency energy capture module, the energy capture efficiency on metal surfaces is significantly improved, effectively overcoming the challenge of energy capture in metal environments for traditional RFID tags. When in a non-metallic environment, the system switches to a UHF band priority operating mode. The impedance-adjustable loop antenna of the ultra-high-frequency energy capture module dynamically adjusts its impedance based on the metal distance through a switching matching network, flexibly adapting to different environmental conditions and greatly expanding the application range of the tag, ensuring stable and efficient energy acquisition in various complex scenarios.

[0021] Intelligent optimization of temperature sensing and sampling: The digital temperature sensor supports a wide temperature range of -40℃ to 125℃ and features a built-in 16-bit ADC for high-precision temperature measurement. The intelligent sampling control module intelligently controls and dynamically adjusts based on different supercapacitor voltage conditions, providing three operating modes: real-time mode, normal mode, and energy-saving mode. When the supercapacitor voltage is sufficient, real-time mode is used for high-precision, high-frequency temperature measurement, meeting the needs of applications sensitive to temperature changes. When the voltage is low, it automatically switches to energy-saving mode, reducing power consumption while maintaining basic temperature monitoring functions. This adaptive sampling strategy cleverly balances performance and power consumption, extending tag lifespan and improving system stability and reliability.

[0022] The data fusion transmission layer employs dual-channel anti-interference modulation technology, separating the transmission channels for identity ID and temperature data. One channel utilizes the UHF band, employing ASK modulation to transmit identity ID and meeting the ISO 18000-6C standard; the other channel transmits temperature data via a low-frequency band using PSK modulation. This effectively avoids interference between different data types, significantly improving communication reliability in metallic environments and ensuring independent and stable transmission of identity ID and temperature data. Simultaneously, the encoding protocol extension module, based on the 96-bit ID encoding of the EPC C1G2 standard, extends 8 bits of temperature data using reserved bits, covering a temperature range of -40℃ to 125℃ with a step size of 0.5℃, accurately representing temperature information. The equipped CRC-8 checksum generation and detection function generates and appends a checksum at the data sending end, and performs verification calculations and comparisons at the receiving end, effectively detecting and correcting errors during data transmission, further improving the accuracy and integrity of data transmission. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a system architecture block diagram of the present invention; Figure 2 This is a schematic diagram of the dynamic energy management state machine of the present invention; Figure 3 This is a cross-sectional view of the metal mounting structure of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 The diagram below shows the system architecture of the present invention. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing is characterized by a three-layer modular architecture design, including an energy input layer, a temperature sensing layer, and a data fusion and transmission layer, and integrates dynamic energy management strategies and metal environment enhancement design; wherein: The energy input layer adopts a dual-frequency collaborative power supply mechanism, including a low-frequency energy harvesting module, an ultra-high-frequency energy harvesting module, and an adaptive switching controller. The low-frequency energy harvesting module uses an LC resonant circuit with a resonant frequency of 125kHz and is equipped with a magnetoelectric composite antenna. The magnetoelectric composite antenna consists of an iron-silicon-aluminum magnetic core with a thickness of 0.3mm and a relative permeability of 200, a flexible ferrite substrate with a loss tangent of <0.01, and a nano-silver mesh radiator with a linewidth of 50μm. The antenna quality factor Q value is >60. The UHF energy harvesting module integrates an impedance-adjustable loop antenna and employs a switching matching network with three PIN diode switching units, offering an impedance adjustment range of 50Ω - 200Ω. The adaptive switching controller, based on the LTC3588-1 energy management IC, incorporates an environmental electromagnetic intensity detection module. When in a metallic environment with a magnetic field strength >5μT, the adaptive switching controller automatically switches to a low-frequency dominant mode, with low-frequency energy accounting for ≥75%. The magnetoelectric composite antenna of the low-frequency energy harvesting module enhances magnetic field coupling through a magnetic core, increasing the metal surface energy harvesting efficiency to 68%. In a non-metallic environment, the UHF band operates preferentially, and the UHF energy harvesting module takes effect. Its integrated impedance-adjustable loop antenna dynamically adjusts the impedance based on the distance to the metal surface through the switching matching network, achieving a transmission distance of up to 10 meters in non-metallic environments. Simultaneously, backscatter modulation enhances the data transmission rate to 40kbps.

[0029] The temperature sensing layer includes a digital temperature sensor and an intelligent sampling control module. The digital temperature sensor features an ultra-low operating current of 1.8μA (under 3.3V power supply), supports operation within a range of -40℃ to 125℃, and has a built-in 16-bit ADC, achieving a theoretical resolution of 0.1℃. The intelligent sampling control module performs intelligent control and dynamic adjustment based on different supercapacitor voltage conditions, and its operating modes include real-time mode, normal mode, and energy-saving mode. The intelligent sampling control module dynamically adjusts based on the supercapacitor voltage V_cap. When V_cap > 2.8V, the system enters real-time mode, starting a 16-bit ADC for data sampling, performing temperature measurements once per second and transmitting data in real-time via dual channels. This mode utilizes a high-precision ADC to achieve relatively accurate temperature data acquisition, suitable for scenarios requiring high temperature monitoring accuracy and where the supercapacitor has sufficient charge.

[0030] When 2.2V ≤ V_cap ≤ 2.8V, the system enters normal mode and switches to a 12-bit ADC for sampling. The sampling interval is dynamically adjusted according to V_cap. The adjustment formula is T_sample = 10 × (2.5 - V_cap) + 10 seconds. This dynamic adjustment of the sampling interval effectively saves power while ensuring a certain sampling frequency meets the basic requirements of temperature monitoring.

[0031] When V_cap < 2.2V, the system enters energy-saving mode, stops temperature measurement, and only keeps the energy harvesting module and adaptive controller working. When V_cap rises back to 2.2V, the system automatically wakes up and re-selects the corresponding working mode to sample the temperature based on the V_cap value.

[0032] The data fusion transmission layer employs dual-channel anti-interference modulation technology, consisting of an encoding protocol extension module and a dual-channel modulation module. The encoding protocol extension module is based on the 96-bit ID encoding of the EPC C1G2 standard, utilizing reserved bits to extend 8 bits of temperature data. The temperature range is -40℃ to 125℃, with a step size of 0.5℃, corresponding to binary values ​​from 00000000 (representing -40℃) to 11111111 (representing 124.5℃). The highest bit serves as the sign bit, accurately encoding the temperature information into the reserved bits of the ID encoding, thus achieving the fusion of temperature data and identity ID. It also features CRC-8 checksum generation and detection. At the data sending end, a CRC-8 checksum is generated based on the encoded data and transmitted. At the data receiving end, CRC-8 verification is performed and compared with the received checksum, ensuring a data transmission error rate of less than 10⁻⁻⁶. 6 The dual-channel modulation module contains two independent modulation channels. One channel is used for the transmission of identity ID via the UHF band using ASK modulation, and meets the ISO18000-6C standard. The other channel is used for the transmission of temperature data via the low-frequency band using PSK modulation, so as to realize independent and stable transmission of identity ID and temperature data under different frequency bands and modulation methods.

[0033] The dynamic energy management strategy includes a three-tiered energy storage unit, specifically: The transient buffer layer uses a supercapacitor with specifications of 2.7V / 100mF, an equivalent series resistance of less than 50mΩ, and a response time of less than 5ms as the core energy storage element to capture high-frequency transient energy in the system's operating environment. Working process: During the energy capture phase, high-frequency transient energy is generated when the reader emits a pulse signal. Because the transient buffer layer uses a 2.7V / 100mF supercapacitor with an equivalent series resistance (ESR) of less than 50mΩ, it exhibits fast response characteristics, with a response time of less than 5ms. This allows the supercapacitor to instantly capture the high-frequency transient energy carried by the reader's pulse signal, rapidly storing this energy and preventing energy waste and loss.

[0034] During the energy release phase, the captured high-frequency transient energy is released when the system needs it. When other circuit modules in the system (such as data acquisition modules, communication modules, etc.) experience a momentary peak in energy demand during operation, the supercapacitor in the transient buffer layer can quickly release the stored energy to provide timely power support to these modules, ensuring the stable operation of the system. At the same time, the supercapacitor can also smooth out power supply voltage fluctuations, reducing interference to the system caused by unstable energy supply.

[0035] The main energy storage layer uses a 3.0V / 10mAh thin-film lithium battery with dimensions of 10mm×8mm×1.5mm as the energy storage element. As the main energy storage unit of the system, it continuously receives external power input and converts it into chemical energy for storage during normal system operation, providing energy assurance for long-term system operation. Under normal temperature conditions, when the system is in hibernation mode or the external power supply is interrupted, it provides stable power to the system's memory. Working process: During the conventional energy storage phase, as the system operates normally, the 3.0V / 10mAh thin-film lithium battery in the main energy storage layer continuously receives energy input from an external power source, converting electrical energy into chemical energy for storage. Thin-film lithium batteries have the advantage of small size, making them suitable for use in systems with limited space.

[0036] During the data retention phase, under normal temperature conditions, the thin-film lithium battery in the main energy storage layer can support the system for 72 hours of data retention. When the system is in hibernation mode or when the external power is interrupted, the thin-film lithium battery provides stable power to the system's memory, ensuring that the data stored therein is not lost. For example, in a temperature sensing system, the collected temperature data is stored in the memory, and even if the system experiences a short-term power outage, the thin-film lithium battery can ensure the safe preservation of this data.

[0037] During the system power supply phase, when the supercapacitor in the transient buffer layer cannot meet the system's energy demands, the thin-film lithium battery in the main energy storage layer begins to provide the primary power support. This ensures a continuous and stable power supply to all modules within the system, guaranteeing its long-term normal operation.

[0038] The emergency backup layer uses 0.1F gold capacitors with an operating temperature range of -55℃ to 125℃ as energy storage components. In the event of main power failure, this ensures the system completes its final data upload, improving system reliability and data security. Operating process: The 0.1F gold capacitor in the emergency backup layer monitors the status of the main power supply and the thin-film lithium battery in the main energy storage layer in real time. The gold capacitor has a wide operating temperature range (-55℃~125℃), which can work normally in various harsh environments and ensure accurate monitoring of the main power supply status.

[0039] In the main power failure response, when a main power supply (thin-film lithium battery) failure is detected, the gold capacitor in the emergency backup layer immediately activates the emergency power supply mechanism. At this time, the gold capacitor releases its stored energy to provide the power required for the final data upload. It is known that the final data upload requires 0.5 mJ of energy, and the gold capacitor can support three transmissions. This means that after a main power failure, the system has sufficient opportunity to upload important data to external devices, avoiding data loss.

[0040] Energy depletion and system status: After completing the final data upload, the emergency backup layer's key capacitors ran out of power. At this point, the system ceased operation due to power loss, but the emergency backup layer ensured the secure transmission of critical data, improving system reliability and data security.

[0041] Metal environment enhancement design includes optimizing the composite antenna structure, specifically: The three-layer material design features a bottom layer of iron-silicon-aluminum magnetic core with a permeability of μ = 200. Its high permeability helps to concentrate magnetic lines of force, enhancing the antenna's magnetic flux density and improving its ability to receive and transmit low-frequency electromagnetic signals. The middle layer is a flexible ferrite substrate with a dielectric constant of ε = 15. Its flexibility allows for easy mounting on metal surfaces of various shapes and enables adjustment of the antenna's electromagnetic characteristics, achieving impedance matching and resonant frequency adjustment, ensuring good antenna operation in metallic environments. The top layer is a nano-silver mesh radiator with a sheet resistance of <0.1Ω / □. Its low resistance allows for efficient radiation and reception of electromagnetic waves, reducing energy loss. Its mesh structure adapts to metal surface deformation, ensuring stable antenna performance. The dual-band isolation technology is adopted. The low-frequency coil has an inner diameter of 8mm and an outer diameter of 12mm, with a total of 5 turns. The UHF radiator and the low-frequency coil are arranged at 90° orthogonal. The distance between the two is optimized to 2mm through electromagnetic simulation, so that the coupling coefficient is <0.05, which realizes effective isolation between the low-frequency band and the UHF band, ensuring that the antennas of the two bands work independently and do not interfere with each other.

[0042] The specific operating modes of composite antennas include: Low-frequency operating mode: When an external low-frequency electromagnetic signal reaches the antenna, the bottom iron-silicon-aluminum magnetic core first senses the signal and gathers magnetic lines of force to enhance the magnetic field strength. The low-frequency coil generates an induced electromotive force in the changing magnetic field to convert the electromagnetic signal into an electrical signal. The middle layer flexible ferrite substrate adjusts the impedance of the low-frequency coil to match the signal source and improves the signal reception efficiency. The top layer nano-silver mesh radiator has little impact on low-frequency signal radiation and mainly plays a protective and support role.

[0043] UHF Operating Mode: For UHF band signals, the top layer of nano-silver mesh radiator serves as the main radiating and receiving element, converting electromagnetic waves into current signals. It interacts with the middle layer of flexible ferrite substrate to achieve impedance matching and signal transmission. Because the low-frequency coil is orthogonally arranged with optimized spacing to the UHF radiator, the low-frequency coil has minimal interference to the UHF signal, ensuring stable reception and transmission of the UHF signal.

[0044] The metal environment enhancement design includes thermal coupling and thermal isolation, specifically: The temperature measurement point was optimized. The temperature sensor was directly mounted on the metal surface contact point using thermally conductive silicone with a thermal conductivity of 3.5 W / m・K and a thickness of 0.2 mm. According to the thermal resistance calculation formula R_th = δ / λ, where δ is the thickness of the thermally conductive silicone and λ is the thermal conductivity of the thermally conductive silicone, the thermal resistance R_th = 0.2 mm / 3.5 W / m・K = 0.057 ℃ / W, ensuring that the temperature difference between the sensor and the metal surface is <0.1 ℃. When the temperature of the metal surface changes, heat is rapidly transferred to the temperature sensor through the thermally conductive silicone. The temperature sensor converts the temperature change into an electrical signal and transmits it to the subsequent data processing module. The low thermal resistance of the thermally conductive silicone enables the temperature sensor to reflect the metal surface temperature in real time and accurately, providing reliable data support for the system's temperature sensing function.

[0045] The thermal isolation structure separates the antenna area from the sensing area via a polyimide thermal insulation layer, reducing heat transfer from the antenna area to the sensing area. Combined with a temperature difference compensation algorithm trained on a BP neural network, the sensor measurements are corrected based on the antenna current and ambient temperature, controlling thermal crosstalk error to <0.2℃. The thermal isolation structure uses a 0.5mm thick polyimide thermal insulation layer with a thermal conductivity of 0.15W / m・K as a thermal barrier to reduce the heat generated by the antenna current during operation. The BP neural network-based temperature difference compensation algorithm dynamically corrects the sensor measurements based on the antenna current and ambient temperature, eliminating thermal crosstalk and ensuring accurate temperature measurements.

[0046] Example 1: Monitoring of Metal Shelves in Medical Cold Chain (I) System Deployment Label installation: Fix the label to the surface of the 304 stainless steel shelf (2mm thick) with thermally conductive double-sided adhesive (0.1mm thick, 2.0W / m・K thermal conductivity). The sensor is attached 10mm away from the antenna area (separated by a thermal insulation layer).

[0047] Reader configuration: Deploy UHF readers (model Impinj Speedway R420, transmit power 33dBm) at 6-meter intervals, and install low-frequency activators (125kHz, field strength 8μT) on the shelf uprights, covering a range of 3 meters.

[0048] (II) Work Process Initialization phase: When the tag enters a metallic environment, the Hall sensor detects a magnetic field strength of 8μT, triggering a low-frequency dominant mode. The low-frequency module completes energy accumulation within 5 seconds, the supercapacitor voltage rises to 3.0V, and the EPC code reading is activated (ID: 32-bit manufacturer code + 32-bit product code + 32-bit serial number).

[0049] Normal monitoring phase: When V_cap>2.8V, high-precision mode is activated: TSYS01 samples at 1-second intervals, and after CRC verification, the 16-bit data is transmitted via low-frequency PSK modulation, and the ID information is transmitted via UHF ASK modulation. The reader synchronously parses the dual-channel data.

[0050] When the reader signal is interrupted due to shelf movement, the main energy storage layer lithium battery continues to supply power to maintain data acquisition for 72 hours (during which sampling is performed at 10-second intervals with 12-bit precision).

[0051] Exception handling phase: When a temperature >8℃ (the upper limit for medical cold chain) is detected, the tag immediately switches to the UHF band and sends an alarm signal at maximum power (60% backscatter efficiency). At the same time, it continuously transmits real-time temperature data through a low-frequency channel (at 200ms intervals) to ensure that the alarm response time in a metal environment is <2 seconds.

[0052] (III) Verification of key parameters Energy efficiency test: Using an Agilent N5244A vector network analyzer, the test was conducted on a metal surface (10cm×10cm stainless steel plate). The energy capture efficiency in low frequency mode was 68% (28% for traditional single-frequency tags), and the transmission distance in ultra-high frequency mode was 8 meters (10 meters in non-metallic environments).

[0053] Temperature measurement accuracy test: Tested in a constant temperature chamber (accuracy ±0.1℃), within the range of -20℃ to 50℃, the error of this invention is ±0.3℃, while the error of the traditional solution is ±1.8℃ (according to ISO 13485 medical device temperature measurement standard).

[0054] Transmission reliability test: In a metal mesh environment (simulating multipath interference), the dual-channel transmission success rate is 99.7% (10,000 tests, 3 bit errors), while the traditional single-channel solution has a success rate of 82% (1,800 bit errors).

[0055] Example 2: Temperature Monitoring of Industrial Equipment (Extended Application Scenarios) Application scenario: Installed on the surface of copper busbars in high-voltage switchgear (temperature range -40℃~125℃) to monitor the operating temperature of the equipment.

[0056] Technical compatibility: High-temperature resistant materials are used (the antenna substrate is polytetrafluoroethylene, which can withstand temperatures up to 200°C). Dynamic energy management strategy adjustment: When the temperature is >100℃, the sampling frequency is automatically increased to 2 times per second (V_cap>3.0V required).

[0057] Actual test results: Even at a high temperature of 125℃, it can still maintain two effective samples per minute, and the data retention time is up to 48 hours (traditional active tags only last 6 hours).

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing, characterized in that, It adopts a three-layer modular architecture design, including an energy input layer, a temperature sensing layer, and a data fusion and transmission layer, and integrates dynamic energy management strategies and metal environment enhancement design; among which: The energy input layer employs a dual-frequency collaborative power supply mechanism, comprising a low-frequency energy harvesting module, an ultra-high-frequency energy harvesting module, and an adaptive switching controller. The low-frequency energy harvesting module uses an LC resonant circuit with a resonant frequency of 125kHz and is equipped with a magneto-electric composite antenna. The ultra-high-frequency energy harvesting module integrates an impedance-adjustable loop antenna. The adaptive switching controller is based on the LTC3588-1 energy management IC and incorporates an environmental electromagnetic intensity detection module. When in a metal surface environment with a magnetic field strength >5μT, the adaptive switching controller automatically switches to a low-frequency dominant mode, with low-frequency energy accounting for ≥75%. The magneto-electric composite antenna of the low-frequency energy harvesting module enhances magnetic field coupling through a magnetic core, improving the energy harvesting efficiency from the metal surface. When in a non-metallic environment, the UHF band operates preferentially, and the ultra-high-frequency energy harvesting module takes effect. Its integrated impedance-adjustable loop antenna dynamically adjusts the impedance based on the metal distance through a switching matching network, and improves the data transmission rate through backscatter modulation. The temperature sensing layer includes a digital temperature sensor and an intelligent sampling control module. The digital temperature sensor supports operation in the range of -40℃ to 125℃ and has a built-in 16-bit ADC. The intelligent sampling control module performs intelligent control and dynamic adjustment according to different supercapacitor voltage conditions. Its working modes include real-time mode, normal mode and energy-saving mode. The data fusion transmission layer employs dual-channel anti-interference modulation technology, consisting of an encoding protocol extension module and a dual-channel modulation module. The encoding protocol extension module is based on the 96-bit ID encoding of the EPC C1G2 standard, extending 8 bits of temperature data using reserved bits, with a temperature range of -40℃ to 125℃ and a step size of 0.5℃. It also features CRC-8 checksum generation and detection functions. At the data sending end, a CRC-8 checksum is generated based on the encoded data and appended for transmission. At the data receiving end, CRC-8 checksum calculation is performed and compared with the received checksum. The dual-channel modulation module contains two independent modulation channels. One channel is used for ID transmission via the UHF band using ASK modulation, meeting the ISO 18000-6C standard. The other channel is used for temperature data transmission via the low-frequency band using PSK modulation, enabling independent and stable transmission of ID and temperature data across different frequency bands and modulation methods.

2. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 1, characterized in that, The magnetoelectric composite antenna consists of an iron-silicon-aluminum magnetic core with a thickness of 0.3 mm and a relative permeability of 200, a flexible ferrite substrate with a loss tangent of <0.01, and a nano-silver mesh radiator with a linewidth of 50 μm. The antenna quality factor Q value is >60.

3. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 1, characterized in that, The intelligent sampling control module dynamically adjusts based on the supercapacitor voltage V_cap: When V_cap > 2.8V, it enters real-time mode, starts a 16-bit ADC to sample data, and performs temperature measurement once per second + dual-channel real-time transmission; When 2.2V≤V_cap≤2.8V, it enters normal mode and switches to 12-bit ADC for sampling. The sampling interval is dynamically adjusted according to V_cap. When V_cap < 2.2V, the system enters energy-saving mode, stops temperature measurement, and only keeps the energy harvesting module and adaptive controller working. When V_cap rises back to 2.2V, the system automatically wakes up and re-selects the corresponding working mode to sample the temperature based on the V_cap value.

4. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 3, characterized in that, In the normal mode, the sampling interval is dynamically adjusted according to V_cap, and the adjustment formula is T_sample = 10 × (2.5 - V_cap) + 10 seconds.

5. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 1, characterized in that, The dynamic energy management strategy includes a three-tiered energy storage unit, specifically: The transient buffer layer uses a supercapacitor with a specification of 2.7V / 100mF, an equivalent series resistance of less than 50mΩ, and a response time of less than 5ms as the core energy storage element to capture high-frequency transient energy in the system operating environment. The main energy storage layer uses a 3.0V / 10mAh thin-film lithium battery with a volume of 10mm×8mm×1.5mm as the energy storage element. As the main energy storage unit of the system, it continuously receives external power input and converts it into chemical energy for storage during normal system operation, providing energy guarantee for long-term system operation. Under normal temperature conditions, when the system is in a dormant state or the external power is interrupted, it provides stable power to the system memory. The emergency backup layer uses 0.1F gold capacitors with an operating temperature range of -55℃ to 125℃ as energy storage components to ensure the system completes the final data upload when the main power supply fails, thereby improving system reliability and data security.

6. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 1, characterized in that, The metal environment enhancement design includes optimizing the composite antenna structure, specifically: The three-layer material design features an iron-silicon-aluminum magnetic core with a permeability of μ = 200 at the bottom layer. Its high permeability helps to concentrate magnetic lines of force, enhance the antenna's magnetic induction intensity, and improve its ability to receive and transmit low-frequency electromagnetic signals. The middle layer is a flexible ferrite substrate with a dielectric constant of ε = 15. Its flexibility allows for easy mounting on metal surfaces of different shapes and enables adjustment of the antenna's electromagnetic characteristics, achieving impedance matching and resonant frequency adjustment, thus enabling the antenna to work well in metallic environments. The top layer is a nano-silver mesh radiator with a sheet resistance of < 0.1Ω / □, which has low resistance characteristics, can efficiently radiate and receive electromagnetic waves, reduce energy loss, and its mesh structure can adapt to the deformation of the metal surface, ensuring the stability of the antenna performance. The dual-band isolation technology is adopted. The low-frequency coil has an inner diameter of 8mm and an outer diameter of 12mm, with a total of 5 turns. The UHF radiator and the low-frequency coil are arranged at 90° orthogonal. The distance between the two is optimized to 2mm through electromagnetic simulation, so that the coupling coefficient is < 0.05, which realizes effective isolation between the low-frequency band and the UHF band, ensuring that the antennas of the two bands work independently and do not interfere with each other.

7. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 6, characterized in that, The specific operating modes of the composite antenna include: Low-frequency operating mode: When an external low-frequency electromagnetic signal reaches the antenna, the bottom iron-silicon-aluminum magnetic core first senses the signal and gathers the magnetic lines of force to enhance the magnetic field strength. The low-frequency coil generates an induced electromotive force in the changing magnetic field to convert the electromagnetic signal into an electrical signal. The middle flexible ferrite substrate adjusts the impedance of the low-frequency coil to match the signal source, thereby improving the signal reception efficiency. UHF operating mode: For UHF band signals, the top layer of nano-silver mesh radiator acts as the main radiating and receiving element, converting electromagnetic waves into current signals, and interacting with the middle layer of flexible ferrite substrate to achieve impedance matching and signal transmission.

8. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 1, characterized in that, The metal environment enhancement design includes thermal coupling and thermal isolation, specifically: Temperature measurement points were optimized. The temperature sensor was directly mounted on the metal surface contact point using thermally conductive silicone with a thermal conductivity of 3.5 W / m・K and a thickness of 0.2 mm. According to the thermal resistance calculation formula R_th = δ / λ, where δ is the thickness of the thermally conductive silicone and λ is the thermal conductivity of the thermally conductive silicone, the thermal resistance R_th = 0.2 mm / 3.5 W / m・K = 0.057 ℃ / W, ensuring that the temperature difference between the sensor and the metal surface is < 0.1 ℃. The thermal isolation structure separates the antenna area from the sensing area through a polyimide thermal insulation layer, reducing heat transfer from the antenna area to the sensing area. Combined with a temperature difference compensation algorithm based on BP neural network training, the sensor measurement values ​​are corrected by input parameters of antenna current and ambient temperature, and the thermal crosstalk error is controlled to be less than 0.2℃.

9. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 8, characterized in that, The temperature measurement point is where heat is rapidly transferred to the temperature sensor through thermally conductive silicone when the metal surface temperature changes. The temperature sensor converts the temperature change into an electrical signal and transmits it to the subsequent data processing module. The low thermal resistance of the thermally conductive silicone enables the temperature sensor to reflect the metal surface temperature in real time and accurately, providing reliable data support for the system's temperature sensing function.

10. The metal environment adaptive RFID tag system based on dual-frequency collaborative power supply and temperature sensing as described in claim 8, characterized in that, The thermal isolation structure uses a polyimide thermal insulation layer as a thermal barrier to reduce the transfer of heat generated by the current during antenna operation to the sensing area. A 0.5mm thick polyimide thermal insulation layer with a thermal conductivity of 0.15W / m・K is used for separation. The temperature difference compensation algorithm based on the BP neural network dynamically corrects the sensor measurement value according to the antenna current and ambient temperature, eliminates the influence of thermal crosstalk, and ensures accurate temperature measurement.

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