An RFID-based intelligent tracking method for building material storage

Abstract

The application discloses a kind of based on RFID's building material storage intelligent tracking method, the present application relates to RFID radio frequency identification and building material storage tracking technical field, material RFID tag is constituted by open resonant ring and capacitive coupling patch, directly attached to the surface of metal building material, read-write device antenna is aligned with the beam end surface of building material and emits inquiry signal, signal is converted into surface wave along the axial propagation of building material by end surface coupling, wakes up internal label and makes backscattering signal along the original path return end surface, read-write device records the received signal strength indication and phase data of return signal, according to surface wave attenuation model and phase delay model joint solution label axial position, combined with end surface radial coordinate obtains the three-dimensional position of label, the present application does not need to separate dielectric pad height antenna to solve the problem of metal failure, and break through the shielding effect formed by dense stacking metal building material, realize low-cost no leakage reading tracking.

Description

Technical Field

[0001] This invention relates to the field of RFID radio frequency identification and building material warehousing tracking technology, specifically to an RFID-based intelligent tracking method for building material warehousing. Background Technology

[0002] Passive UHF RFID tags typically consist of a chip and a dipole antenna, operating in the UHF band. They are powered by radio frequency energy emitted by the reader, which excites the tag to radiate backscattered signals into space, thereby enabling non-contact identification of objects. Metals have strong reflective properties to electromagnetic waves. When the tag antenna is in close contact with a metal surface, the metal will introduce a mirror current in the near-field region of the antenna, causing a sharp shift in the antenna impedance. This results in the tag almost completely losing its reading capability, which is the tag failure problem caused by metal contact.

[0003] To address this issue, existing technologies mainly employ two approaches. The first approach involves placing an isolation dielectric layer between the tag antenna layer and the metal surface, raising the antenna to a certain height to avoid strong reflections in the near-field of the metal and restoring antenna impedance matching. This approach requires increasing the thickness of the isolation dielectric layer, resulting in a bulky tag that is easily damaged by impacts during heavy-duty handling scenarios such as building material hoisting, rolling, and collisions. Furthermore, it is only suitable for single-layer exposed metal scenarios. The second approach involves deploying multiple reader antennas in the storage area and using an anti-collision algorithm to schedule and identify the responses of multiple tags. This approach only improves the efficiency of concurrent identification of multiple tags at the software scheduling level without changing the physical propagation path of electromagnetic waves. When metal building materials are bundled and stacked, the outer metal layer forms a Faraday cage shielding effect on the inner metal layer, shielding the radio frequency signals of the inner and bottom tags. Existing software scheduling algorithms struggle to penetrate this physical shielding, resulting in a persistently high tag miss rate in densely stacked scenarios.

[0004] The two existing technical solutions mentioned above attempt to solve the tag recognition problem in a metallic environment from the perspectives of hardware structure and software algorithm, respectively. However, neither of them can simultaneously take into account the tag size, mechanical reliability, and deep shielding penetration capability, making it difficult to meet the actual needs of low cost, low loss, and no missed reading tracking in building material storage scenarios. Summary of the Invention

[0005] To address the problems of existing anti-metal tag structures, such as bulky tags, susceptibility to damage from impacts, and applicability only to single-layer exposed metal scenarios, as well as the issue of high missed read rates due to the inability of software scheduling algorithms in multi-antenna array scanning and background anti-collision algorithms to penetrate the Faraday cage shielding effect formed by densely stacked metal building materials, this invention provides an RFID-based intelligent tracking method for building material warehousing. This method aims to solve the problem of tag failure when attached to metal without adding an isolation medium to elevate the antenna structure. Furthermore, it overcomes the shielding effect formed by densely stacked metal building materials at the physical link level, achieving low-cost, low-loss, and miss-free intelligent tracking of densely bundled and stacked metal building materials such as steel pipes, rebar bundles, wire rods, and scaffolding.

[0006] Technical solution

[0007] To solve the above-mentioned technical problems, the present invention provides an RFID-based intelligent tracking method for building material warehousing, comprising:

[0008] The reader antenna is deployed in front of the end face of the bundle of metal building materials to be tracked, so that the beam direction of the reader antenna is aligned with the cross-section of the end face of the bundle of metal building materials. The bundle of metal building materials is made up of multiple metal building materials bundled and stacked together. Each metal building material has a metamaterial RFID tag attached to its surface. The metamaterial RFID tag includes a resonant coupling network composed of an open resonant ring and a broadband capacitive coupling patch. The metamaterial RFID tag is directly attached to the surface of the metal building material.

[0009] The reader transmits an interrogation signal in the UHF band to the end face of the building material bundle. When the interrogation signal reaches the end face, it is converted into a surface wave signal that propagates along the axial direction of each metal building material through the coupling effect at the junction of each metal building material end and the air, and then propagates into the interior of the building material bundle.

[0010] When the surface wave signal propagated along the surface of the metal building material is transmitted to the attachment position of the metamaterial RFID tag, the energy of the surface wave signal is coupled into the metamaterial RFID tag by the open resonant ring and the broadband capacitive coupling patch, thus waking up the tag chip.

[0011] The awakened tag chip modulates its stored electronic identification information onto the reflection coefficient to form a backscattered signal. This backscattered signal is coupled back to the surface of the metal building material via a broadband capacitive coupling patch and an open resonant ring, and returns to the end face in the opposite direction to the interrogation signal and along the original surface wave propagation path.

[0012] The backscattered signal returned to the end face is received by the reader antenna, and the tag identification, received signal strength indication and phase delay data corresponding to the backscattered signal are recorded.

[0013] Based on the recorded received signal strength indication and phase delay data, the position information of each metamaterial RFID tag within the building material bundle is calculated.

[0014] Based on the above technical solutions, the present invention further provides a metamaterial RFID tag for attaching to the surface of metal building materials. The tag, from top to bottom, includes a protective film layer, a flexible microstrip printing layer, chip pads and an RFID chip, and an insulating adhesive layer. The flexible microstrip printing layer contains an open-ended resonant ring and a broadband capacitive coupling patch, which together form a resonant coupling network. The insulating adhesive layer is disposed between the flexible microstrip printing layer and the surface of the metal building material to fix the metamaterial RFID tag to the surface of the metal building material. The thickness of the insulating adhesive layer is less than the thickness of the electromagnetic isolation gap required to generate impedance matching. This resonant coupling network does not rely on radiating energy into the air, but instead couples electromagnetic energy directly into the surface of the metal building material through near-field capacitive coupling, exciting surface wave modes that propagate along the axial direction of the metal building material, so that the metal building material itself constitutes the secondary radiating antenna and waveguide medium of the tag.

[0015] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows:

[0016] 1. The metamaterial RFID tag of this invention consists of an open resonant ring and a broadband capacitive coupling patch forming a resonant coupling network. It can be directly attached to the surface of metal building materials to achieve impedance matching without the need for an isolation medium to raise the antenna. The tag structure is ultra-thin and can fit tightly to the surface of building materials. Compared with anti-metal tag structures that rely on an isolation medium layer, the tag volume is significantly reduced, and the impact resistance is improved in heavy-duty handling scenarios such as building material hoisting, rolling, and collision. The tag manufacturing cost is also reduced.

[0017] 2. The reader antenna of this invention illuminates only the cross-section of the end face of the building material bundle. The excitation signal is transmitted along the surface of the metal building material in the form of surface waves to the deep interior, waking up the internal and bottom tags. This transmission path relies on the surface of the metal building material itself rather than air. The Faraday cage shielding effect formed by the outer metal building material only shields spatial radiation waves and does not block the surface waves transmitted along the surface of the building material itself. Thus, it breaks through the shielding effect in densely stacked scenarios from the physical link level and reduces the tag miss rate of metal building materials in densely bundled and stacked states.

[0018] 3. This invention calculates the axial position of the tag by jointly using the received signal strength indication attenuation model and the phase delay model, and combines the radial coordinate information scanned by the reader end face to obtain the estimated three-dimensional spatial coordinates of the tag within the building material bundle. The result is then compared and verified with the preset geometric stacking model of the building material bundle to eliminate abnormal estimates, so that the tracking and positioning results meet the requirements of warehouse inventory and three-dimensional position estimation. Attached Figure Description

[0019] Figure 1 This is a flowchart of the overall method for intelligent tracking of building materials warehousing in an embodiment of the present invention;

[0020] Figure 2 This is a flowchart of the label 3D position calculation in an embodiment of the present invention;

[0021] Figure 3 This is a flowchart illustrating the bidirectional signal processing flow of metamaterial RFID tags in an embodiment of the present invention. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1-3 The specific embodiments of the present invention will be further described below. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0023] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0024] System Overall Architecture

[0025] The tracking system involved in this invention is applied to a stack of building materials formed by bundling and stacking multiple metal building materials. Each metal building material in the stack has a metamaterial RFID tag attached to its surface. An end-face illumination reader antenna is deployed directly in front of the end face of the stack, with the beam direction of the reader antenna aligned with the cross-section of the end face of the stack. The reader antenna is connected to a radio frequency front-end signal acquisition module. The raw signal output by the radio frequency front-end signal acquisition module, including amplitude and phase data, is transmitted to a location resolution and tracking server. The location resolution and tracking server is internally divided into a signal preprocessing module, a location calculation module, and a tag identity and location database module. The processing result is finally connected to the upper-level warehouse management system to realize the visualization of inventory list and three-dimensional location information. The radio frequency signal is transmitted along the surface of the metal building materials into the stack, and the backscattered signal of the metamaterial RFID tag returns to the end face along the original transmission path and is received by the reader antenna, forming a two-way signal closed loop of the system.

[0026] Metamaterial RFID tag structure

[0027] The metamaterial RFID tag, from top to bottom, includes a protective film layer, a flexible microstrip printing layer, chip pads and an RFID chip, and an insulating adhesive layer. The insulating adhesive layer is attached to the surface of the metal building material. The flexible microstrip printing layer contains an open-loop resonant ring array and a broadband capacitive coupling patch. The open-loop resonant ring array and the broadband capacitive coupling patch together form a resonant coupling network. The insulating adhesive layer serves only for electrical isolation and mechanical fixation, used to firmly attach the metamaterial RFID tag to the surface of the metal building material. The thickness of the insulating adhesive layer does not constitute the electromagnetic isolation gap required for impedance matching. That is, the metamaterial RFID tag of this invention does not contain any isolation pad structure used to raise the antenna to avoid the strong near-field reflection zone of the metal.

[0028] The working principle of metamaterial RFID tags is as follows: the open resonant ring array and the broadband capacitive coupling patch together form a broadband resonant coupling network. When this resonant coupling network is attached to the surface of the metal building material, it does not rely on radiating energy into the air. Instead, it directly couples electromagnetic energy into the metal building material through near-field strong capacitive coupling, exciting the surface wave mode that propagates along the axis of the metal building material. This makes the metal building material itself the secondary radiating antenna and waveguide medium of the metamaterial RFID tag.

[0029] Similarly, surface waves on metallic building materials can also couple energy back to the chip pads and RFID chip of the metamaterial RFID tag, powering the chip and transmitting excitation information from the reader to it.

[0030] The resonant frequency of this resonant coupling network can be described by the following formula:

[0031] ;

[0032] In the formula, This represents the resonant frequency of the resonant coupling network composed of an open-loop resonant ring array and a broadband capacitive coupling patch. This represents the equivalent inductance of an open-loop resonant ring array. This represents the equivalent capacitance formed by the gap capacitance of the open-loop resonant array and the coupling capacitance generated on the surface of the metal building material by the broadband capacitive coupling patch. In practical implementation, the resonant frequency can be adjusted by changing the ring width, gap width of the open-loop resonant array, and patch size of the broadband capacitive coupling patch. It falls within the ultra-high frequency operating range of 860 MHz to 960 MHz, achieving impedance matching and efficient energy coupling between metamaterial RFID tags and the surface of metal building materials.

[0033] Principles of wave propagation and deep penetration on metal surfaces

[0034] The cross-section of the densely bundled metal building material bundle shows multiple metal building materials closely arranged. The outer layer of metal building materials forms a Faraday cage structure that shields and surrounds the inner layer of metal building materials. In the longitudinal section of the stacked building material bundle, the reader antenna is located directly in front of the end face of the bundle. Its radio frequency beam only illuminates the end face cross-section. The excitation signal extends from the end face to the inside of the bundle along the axial direction of each metal building material, forming a surface wave propagation path. Multiple metamaterial RFID tags attached to different depths of the metal building materials along this path are sequentially awakened. The backscattered signal of the tag returns to the end face along the original path and is received by the reader, forming a complete signal closed loop. Since the surface wave is propagated along the surface of the metal building material itself rather than radiated in the air, the shielding formed by the outer layer of metal building materials only shields against spatial radiation waves and does not block the surface waves propagated along the surface of the inner metal building materials themselves, thus achieving penetrating excitation of deep tags.

[0035] Surface wave propagation in metals is based on the skin effect. High-frequency current and field energy are concentrated within the skin depth of the conductor surface for propagation. The skin depth can be expressed as:

[0036] ;

[0037] In the formula, Indicates skin depth. Indicates the angular frequency of a radio frequency signal. Indicates the magnetic permeability of metallic building materials. The skin depth represents the electrical conductivity of the metal building material. The above formula shows that the skin depth is related to the signal frequency, the material's electrical conductivity, and its magnetic permeability. In practical implementation, the skin depth can be estimated in advance based on the material of the metal building material to be tracked. Based on this, the coupling size of the broadband capacitive coupling patch in the metamaterial RFID tag is determined to ensure the surface wave excitation efficiency.

[0038] Tracking methods based on end-face illumination

[0039] The RFID-based intelligent tracking method for building material warehousing provided by this invention specifically includes the following processes:

[0040] The reader antenna is deployed in front of the end face of the bundle of metal building materials to be tracked, so that the beam direction of the reader antenna is aligned with the cross-section of the end face of the building material bundle, wherein the bundle of metal building materials is formed by bundling and stacking multiple metal building materials, each with a metamaterial RFID tag attached to its surface.

[0041] The reader transmits an ultra-high frequency interrogation signal to the end face of the building material bundle. When the interrogation signal reaches the end face, it is converted into a surface wave signal that propagates along the axial direction of each metal building material through the coupling effect at the junction of each metal building material end and the air, and is transmitted into the deep interior of the building material bundle.

[0042] When the surface wave signal is transmitted along the surface of the metal building material to the attachment position of each metamaterial RFID tag, the surface wave energy is coupled into the tag by the tag's open resonant ring array and wideband capacitive coupling patch, which powers the tag chip and transmits excitation information to wake up the tag chip.

[0043] The awakened tag chip reads the electronic identification information stored in itself and modulates the identification information onto the reflection coefficient to form a backscatter signal. In specific implementations, temperature and humidity status information can also be added to the identification information and modulated together.

[0044] The backscattered signal generated by the tag is coupled back to the surface of the metal building material via a broadband capacitive coupling patch and an open resonant ring array, and returns to the end face of the building material in the opposite direction to the excitation signal and along the original surface wave propagation path.

[0045] The reader antenna receives the backscattered signal returned to the end face and records the tag identification, received signal strength indication, and phase delay data corresponding to the signal.

[0046] Determine whether the current end-face scan covers the entire area of ​​the building material bundle end-face. If the entire area is not covered, adjust at least one of the illumination angle and position of the reader antenna and repeat the process of transmitting the interrogation signal to receiving the backscattered signal until the entire area of ​​the building material bundle end-face is covered.

[0047] All collected tag information, received signal strength indicators, and phase data are transmitted to the background location analysis and tracking server for location calculation and inventory results summary.

[0048] Tag location tracking algorithm based on joint calculation of received signal strength indication and phase

[0049] The label 3D position calculation algorithm provided by this invention specifically includes the following process:

[0050] The backend server receives the backscatter signal intensity of a certain tag during the current end-face scanning cycle. and phase The raw acquisition data is then filtered using a sliding window to eliminate instantaneous fluctuations caused by multipath interference.

[0051] Based on the power attenuation model of surface waves propagating along the axial direction of building materials, the estimated value of the first axial propagation distance of the tag relative to the end face of the building material is calculated. The power attenuation model is expressed as follows:

[0052] ;

[0053] In the formula, The surface wave propagation distance is represented as The received signal power at that time The initial signal power at the end-face excitation point can be obtained by pre-calibrating the reader's transmit power and coupling efficiency. The surface wave attenuation constant, determined by the building material and signal frequency, can be obtained through preliminary calibration experiments. This indicates the transmission distance of the label from the end face along the axial direction of the building material, which will be measured. Substituting into the model, the inverse solution yields the estimated value of the first axial distance. .

[0054] Based on the phase delay model in the surface wave propagation process, the estimated axial distance is corrected. The phase delay model is expressed as follows:

[0055] ;

[0056] In the formula, Indicates the conduction distance as The signal phase at that time, This indicates the initial phase at the end face excitation point. This represents the phase constant of a surface waveguide, and its value is equal to... Divide by the waveguide wavelength The measured phase Substituting into the model, we obtain the estimated value of the second axial distance. .

[0057] The first axial distance estimate Estimated distance from the second axial direction Weighted fusion is performed to obtain the estimated axial position of the label. The weighting coefficients are preset based on the reliability of the received signal strength indication estimate and the phase estimate in different distance ranges, in order to reduce the error of a single estimation method in a specific distance range.

[0058] By combining the current antenna illumination position and angle information recorded by the reader when scanning the end face of the building material bundle, the radial coordinate position of the building material corresponding to the tag on the end face cross section is determined.

[0059] axial position estimate The coordinates are fused with the radial coordinates to output the estimated three-dimensional spatial coordinates of the label within the building material bundle.

[0060] The estimated three-dimensional spatial coordinates of all labels are compared and verified with the preset geometric stacking model of building material bundles. Abnormal estimates that deviate significantly from the actual arrangement of building materials are eliminated. The results of building material location tracking and inventory are output and written into the backend database along with the label identification information for use by the warehouse management system.

[0061] Alternative implementation methods

[0062] In an alternative implementation, the broadband capacitive coupling patch of the metamaterial RFID tag can be replaced with an E-type or H-type slot coupling patch. The edge electric field generated by the slot boundary also achieves a strong capacitive coupling effect with the surface of the metal building material. While maintaining the ultra-thin bonding characteristics of the tag, it achieves the same surface wave excitation effect as the aforementioned implementation, and can be used as an equivalent alternative to the tag coupling structure design.

[0063] In another alternative implementation, the reader illuminates the end face of the building material bundle at two different frequencies in the same end face scanning cycle. The surface wave attenuation characteristics corresponding to the two different frequencies are different, covering different axial depth ranges in the building material bundle, which further improves the reading reliability of tags inside slender building materials and special materials, and serves as an effective supplement to the surface wave conduction excitation method.

[0064] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A smart tracking method for building material warehousing based on RFID, characterized in that, include: The reader antenna is deployed in front of the end face of the bundle of metal building materials to be tracked, so that the beam direction of the reader antenna is aligned with the cross-section of the end face of the bundle of metal building materials. The bundle of metal building materials is composed of multiple metal building materials bundled and stacked together. Each metal building material has a metamaterial RFID tag attached to its surface. The metamaterial RFID tag includes a resonant coupling network composed of an open resonant ring and a broadband capacitive coupling patch. The metamaterial RFID tag is directly attached to the surface of the metal building material. The reader transmits an ultra-high frequency interrogation signal to the end face of the building material bundle. When the interrogation signal reaches the end face, it is converted into a surface wave signal that propagates along the axial direction of each metal building material through the coupling effect at the junction of each metal building material end and the air, and is then transmitted into the interior of the building material bundle. When the surface wave signal transmitted along the surface of the metal building material is transmitted to the attachment position of the metamaterial RFID tag, the energy of the surface wave signal is coupled into the metamaterial RFID tag by the open resonant ring and the broadband capacitive coupling patch, thus waking up the tag chip; The awakened tag chip modulates its stored electronic identification information onto the reflection coefficient to form a backscattered signal. The backscattered signal is coupled back to the surface of the metal building material via the broadband capacitive coupling patch and the open resonant ring, and returns to the end face in the opposite direction to the interrogation signal and along the original surface wave propagation path. The backscattered signal returned to the end face is received by the reader antenna, and the tag identifier, received signal strength indication and phase delay data corresponding to the backscattered signal are recorded; Based on the recorded received signal strength indication and phase delay data, the position information of each metamaterial RFID tag within the building material bundle is calculated.

2. The method according to claim 1, characterized in that, The step of transmitting an interrogation signal in the UHF band from the reader to the end face of the building material bundle further includes: determining whether the current end face scan covers the entire area of ​​the end face of the building material bundle; if the entire area is not covered, adjusting at least one of the illumination angle and position of the reader antenna, and repeating the step of transmitting the interrogation signal to receiving the backscattered signal until the entire area of ​​the end face of the building material bundle is covered.

3. The method according to claim 1, characterized in that, The step of calculating the position information of each metamaterial RFID tag within the building material bundle based on the recorded received signal strength indication and the phase delay data includes: calculating an estimated first axial transmission distance of the metamaterial RFID tag relative to the end face of the building material bundle based on a power attenuation model for surface waves propagating along the building material axis, wherein the power attenuation model is expressed as: ； In the formula, The surface wave propagation distance is represented as The received signal power at that time This represents the initial signal power at the end face excitation point. This represents the surface wave attenuation constant, which is determined by the building material and the signal frequency. This represents the estimated value of the first axial transmission distance to be determined.

4. The method according to claim 3, characterized in that, Also includes: Based on the phase delay model in the surface wave propagation process, the estimated second axial propagation distance of the metamaterial RFID tag relative to the end face of the building material bundle is calculated. The phase delay model is expressed as follows: ； In the formula, Indicates the conduction distance as The signal phase at that time, This indicates the initial phase at the end face excitation point. This represents the phase constant of the surface waveguide. This represents the estimated value of the second axial transmission distance to be determined; The first axial transmission distance estimate and the second axial transmission distance estimate are weighted and fused to obtain the axial position estimate of the metamaterial RFID tag.

5. The method according to claim 4, characterized in that, Also includes: By combining the antenna illumination position and angle information recorded when the reader antenna scans the end face of the building material bundle, the radial coordinate position of the metal building material corresponding to the metamaterial RFID tag on the cross-section of the end face is determined; the axial position estimate is fused with the radial coordinate position to obtain the three-dimensional spatial coordinate estimation result of the metamaterial RFID tag within the building material bundle.

6. The method according to claim 5, characterized in that, Also includes: The three-dimensional spatial coordinate estimation results of all the metamaterial RFID tags are compared and verified with the preset building material bundle geometric stacking model. The three-dimensional spatial coordinate estimation results that deviate from the arrangement rules of the building material bundle geometric stacking model are eliminated to obtain the building material location tracking and inventory results.

7. The method according to claim 1, characterized in that, The metamaterial RFID tag comprises, from top to bottom, a protective film layer, a flexible microstrip printing layer, chip pads and an RFID chip, and an insulating adhesive layer; the flexible microstrip printing layer contains the open resonant ring and the broadband capacitive coupling patch; the insulating adhesive layer is disposed between the flexible microstrip printing layer and the surface of the metal building material, and is used to fix the metamaterial RFID tag to the surface of the metal building material, the thickness of the insulating adhesive layer being less than the thickness of the electromagnetic isolation gap required to generate impedance matching.

8. The method according to claim 1, characterized in that, The broadband capacitive coupling patch is replaced by a slot coupling patch, which achieves capacitive coupling with the surface of the metal building material through the edge electric field generated at the slot boundary.

9. The method according to claim 1, characterized in that, The step of transmitting an interrogation signal in the UHF band to the end face of the building material bundle by the reader includes: the reader irradiating the end face of the building material bundle at two different frequencies in the same end face scanning cycle, the two different frequencies corresponding to different surface wave attenuation characteristics, respectively used to cover different axial depth ranges in the building material bundle.

10. A metamaterial RFID tag for attaching to the surface of metal building materials, characterized in that, This includes a protective film layer, a flexible microstrip printing layer, chip pads and RFID chips, and an insulating adhesive layer; The flexible microstrip printed layer is disposed between the protective film layer and the chip pad and RFID chip. The flexible microstrip printed layer contains an open resonant ring and a broadband capacitive coupling patch. The open resonant ring and the broadband capacitive coupling patch constitute a resonant coupling network. The insulating adhesive layer is disposed between the flexible microstrip printing layer and the surface of the metal building material, and is used to fix the metamaterial RFID tag to the surface of the metal building material. The thickness of the insulating adhesive layer is less than the thickness of the electromagnetic isolation gap required to generate impedance matching. The resonant coupling network is configured to couple electromagnetic energy into the surface of the metal building material through near-field capacitive coupling, thereby exciting surface waves that propagate along the axial direction of the metal building material, making the metal building material a secondary radiating antenna and waveguide medium for the metamaterial RFID tag.

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