Multilayer anti-metal tag antenna and design method thereof

Abstract

The invention relates to a multilayer anti-metal tag antenna and a design method thereof. The multilayer anti-metal tag antenna comprises a surface tag antenna layer, a middle spacing layer and a bottom grounding resonance loading layer, the tag antenna layer comprises a double-inductance ring formed by a first inductance ring and a second inductance ring, a loading strip matched with the double-inductance ring, a T-shaped matching part and a bent dipole; the loading strip and the T-shaped matching part are arranged on the inner side of the double-inductance ring; the bent dipole is arranged on the outer side of the double-inductance ring; and the resonance loading layer comprises a plurality of resonance strips which are arranged in parallel. The method is suitable for RFID tags which need to work in a high-metal-content environment, such as metal goods shelves, metal containers, industrial equipment and other scenes in logistics storage. Stable read-write performance can be kept in complex environments, and the reliability and durability of the tag are ensured. Through the multi-layer structural design, the antenna can keep high performance in a metal environment, and the requirements of various industrial and application scenes are met.

Description

Technical Field

[0001] The invention relates to the field of tag antennas, and in particular to a multi-layer anti-metal tag antenna and a design method thereof. Background Art

[0002] RFID technology is a contactless automatic identification technology. In recent years, with the rapid development of the Internet of Things industry, RFID technology, as an important supporting technology of the Internet of Things, has also developed rapidly and is widely used in the fields of warehouse management, item tracking and positioning, drug anti-counterfeiting supervision, and traffic vehicle management. However, in heavy asset management and tool management, it is inevitable to encounter various metal environments. Conventional tags are limited by traditional dipole antennas. Such environments have a huge impact on the performance of tags. There are many problems: low sensitivity of conventional flexible anti-metal tags on metal surfaces, narrow bandwidth of ordinary anti-metal tags, too heavy material of ordinary PCB anti-metal tags, harsh requirements for the use environment of ordinary anti-metal tags, and too large size of PCB anti-metal tags with the same performance.

[0003] Therefore, how to optimize the tag antenna structure design to better adapt to the metal environment is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0004] In order to solve at least one of the above technical problems, the present invention provides a multi-layer anti-metal tag antenna, comprising: a surface tag antenna layer, an intermediate spacing layer and a bottom grounded resonant loading layer; The tag antenna layer includes: a double inductor loop formed by a first inductor loop and a second inductor loop, a loading bar matched with the double inductor loop, a T-type matching and a bent dipole; the loading bar and the T-type matching are arranged on the inner side of the double inductor loop; the bent dipole is arranged on the outer side of the double inductor loop; The resonant loading layer includes a plurality of resonant bars arranged in parallel.

[0005] Furthermore, the first inductor loop and the second inductor loop are nested in the middle of the tag antenna layer.

[0006] Furthermore, the loading bar is a U-shaped loading bar, which is arranged between the first inductor ring and the second inductor ring; the opening of the U-shaped loading bar faces the second inductor ring.

[0007] Furthermore, the U-shaped loading bar is close to the second inductor ring.

[0008] Furthermore, T-type matching is arranged at both ends of the second inductor loop; and the chip is arranged between the two T-type matchings.

[0009] Furthermore, the bent dipoles include two bent dipoles, which are respectively located on two sides of the double inductor loop.

[0010] Furthermore, the resonance bar comprises at least a first resonance bar and a second resonance bar of different widths; the first resonance bar and the second resonance bar are arranged at an interval.

[0011] Furthermore, the first resonant bar is 2.5 mm, the second resonant bar is 2 mm, the two are arranged at an interval, and each resonant bar is spaced at a gap of 1 mm and 0.5 mm.

[0012] On the other hand, the present invention also provides a design method of a multi-layer anti-metal tag antenna, which is used to design any of the above multi-layer anti-metal tag antennas, comprising: S1: According to the chip operating frequency and complex impedance, the tag antenna layer is simulated and designed so that the resonant frequency of the tag antenna layer reaches the first resonant frequency that matches the chip operating frequency; the complex impedance of the tag antenna layer is conjugate matched with the complex impedance of the chip; S2: According to the chip operating frequency, simulate and design the grounded resonant loading layer so that the resonant frequency of the loading layer reaches a second resonant frequency that matches the chip operating frequency, and the second resonant frequency covers the first resonant frequency; S3: Stack and merge the tag antenna layer and the grounded resonant loading layer. According to the simulation results, roughly adjust the thickness of the middle loading layer, and then fine-tune the intrinsic properties of the grounded resonant loading layer to meet the design requirements.

[0013] Furthermore, step S1 includes: S11: determining a given electrical length and a given width of the bent dipole according to the operating frequency of the chip; S12: Determine the size of the first inductor loop according to the complex impedance of the chip; S13: determining a preset position of the chip, and under the preset condition, calculating a drop range of the inductive reactance of the antenna to determine a size of the second inductive loop; S14: Loading a simulation voltage at a preset position of the chip, and determining the position and size of the loading bar and the T-type matching according to the simulation results.

[0014] The multi-layer anti-metal tag antenna and its design method of the present invention, the surface tag antenna layer can maintain good impedance matching and radiation characteristics in a metal environment through the combined design of double inductance loops, loading strips, T-type matching and bent dipoles. The resonant strips of the bottom grounded resonant loading layer form a resonant loop through coupling with the surface tag antenna layer, further suppressing the influence of metal on the antenna, ensuring that the antenna can work normally on or near the metal surface. This multi-layer anti-metal tag antenna is suitable for RFID tags that need to work in environments with high metal content, such as metal shelves, metal containers, industrial equipment and other scenarios in logistics warehousing. It can maintain stable read and write performance in these complex environments, ensuring the reliability and durability of the tag. Through this multi-layer structural design, the antenna can maintain high performance in a metal environment and meet the needs of various industrial and application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a multi-layer anti-metal tag antenna of the present invention; Figure 2 It is a structural schematic diagram of an embodiment of the surface tag antenna layer of the tag antenna of the present invention; Figure 3 It is a structural schematic diagram of an embodiment of the bottom ground resonant loading layer of the tag antenna of the present invention; Figure 4 A flow chart of an embodiment of a method for designing a tag antenna of the present invention; Figure 5 This is a simulation result diagram of the multi-layer anti-metal tag antenna of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] It should be noted that if the embodiments of the present invention involve directional indications, such as up, down, left, right, front, back, etc., then the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly. In addition, if the embodiments of the present invention involve descriptions of "first, second", "S1, S2", "step one, step two", etc., then such descriptions are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of indicated technical features or indicating the execution order of the method, etc. Those skilled in the art can understand that anything that does not violate the gist of the invention under the technical concept of the invention should be included in the protection scope of the present invention.

[0018] like Figure 1-3 As shown, the present invention provides a multi-layer anti-metal tag antenna, comprising: a surface tag antenna layer 10, an intermediate spacer layer 20 and a bottom grounded resonant loading layer 30; The tag antenna layer 10 includes: a double inductor loop 11 formed by a first inductor loop and a second inductor loop, a loading bar 12 matched with the double inductor loop, a T-type matching 13 and a bent dipole 14; the loading bar and the T-type matching are arranged on the inner side of the double inductor loop; the bent dipole is arranged on the outer side of the double inductor loop; The resonance loading layer 30 includes a plurality of resonance bars arranged in parallel.

[0019] In this embodiment, the multi-layer anti-metal tag antenna of the present invention is provided, which can be optionally made by FPC printing, in order to improve the performance in a metal environment and ensure that the tag can work normally on or near a metal surface. It is worth noting that the tag antenna of the present invention is only for improving its anti-metal ability, but it is not limited to being used in this environment. It can achieve better performance in a metal environment, and its performance in other environments is bound to be better. Specifically, the tag antenna includes: 1. A surface tag antenna layer, which consists of a winding loop and a radiation patch. This design is designed and optimized for low dielectric constant surfaces, including: a dual inductor loop: It is the main radiating part of the antenna, responsible for the reception and transmission of electromagnetic waves. The dual loop structure helps to enhance the sensing capability of the antenna; a loading bar: The loading bar is used in conjunction with the dual inductor loop to adjust the impedance matching of the antenna, ensure that the antenna can effectively transfer energy to the tag chip, optimize the frequency response of the antenna, and make it work more stably within a specific frequency band; a T-type matching: The T-type matching structure can further optimize the impedance matching of the antenna, ensure that the energy transmission efficiency between the antenna and the tag chip is maximized, and fine-tune the antenna impedance by adjusting its geometric dimensions; a bent dipole: The bent dipole is arranged on the outside of the dual inductor loop, which can expand the radiation range of the antenna, enhance the gain and directivity of the antenna, and the bent structure forms a capacitive loading end, which helps to further reduce the size of the antenna and increase the effective length of the antenna in a limited space, thereby improving its performance. 2. The middle spacer layer is mainly used to isolate the surface tag antenna layer and the bottom ground resonant loading layer to prevent electromagnetic interference between the two; 3. The bottom ground resonant loading layer, the resonant strip: The resonant strip is the core part of the bottom ground resonant loading layer, usually composed of several parallel metal strips. These resonant strips form a resonant structure by coupling with the surface tag antenna layer, further optimizing the frequency response of the antenna and improving the bandwidth of the antenna. The design of the resonant strip can effectively suppress the negative impact of the metal surface on the antenna performance and improve the working stability of the antenna in a metal environment. Especially in a metal environment, it can effectively reduce the interference of metal on the antenna performance and provide good impedance matching for free space and low dielectric constant surfaces.

[0020] Generally speaking, when the tag antenna is close to a metal surface, the metal will reflect electromagnetic waves, causing the impedance of the antenna to change, thereby affecting its performance. The multi-layer anti-metal tag antenna of the present invention can maintain good impedance matching and radiation characteristics in a metal environment through the combined design of dual inductance loops, loading strips, T-type matching and bent dipoles. The resonant strips of the bottom grounded resonant loading layer form a resonant loop by coupling with the surface tag antenna layer, further suppressing the influence of metal on the antenna and ensuring that the antenna can work normally on or near a metal surface. This multi-layer anti-metal tag antenna is suitable for RFID tags that need to work in an environment with a high metal content, such as metal shelves, metal containers, industrial equipment and other scenarios in logistics warehousing. It can maintain stable read and write performance in these complex environments, ensuring the reliability and durability of the tag. Through this multi-layer structural design, the antenna can maintain high performance in a metal environment and meet the needs of various industrial and application scenarios.

[0021] Preferably, Figure 2 As shown, the first inductor loop 11a and the second inductor loop 11b are nested in the middle of the tag antenna layer.

[0022] More preferably, the loading bar 12 is a U-shaped loading bar, which is disposed between the first inductor ring and the second inductor ring; the opening of the U-shaped loading bar faces the second inductor ring. More preferably, the U-shaped loading slot is close to the second inductor ring.

[0023] More preferably, the T-type matching 13 is arranged at both ends of the second inductor loop; and the chip is arranged between the two T-type matchings.

[0024] More preferably, the bent dipoles 14 include two bent dipoles 14, which are respectively located on two sides of the double inductor loop.

[0025] More preferably, the middle spacer layer may be made of a material with a low dielectric constant to reduce energy loss, and preferably, is filled with polytetrafluoroethylene dielectric.

[0026] More preferably, for ultra-high dielectric constant surfaces and metal surfaces, parallel multi-resonance strips are loaded on a grounded substrate, and the substrate and the tag have the same length and width; the resonant strips may optionally include at least a first resonant strip 31a and a second resonant strip 31b of different widths; the two are arranged at intervals. On the other hand, the present invention also provides a design method for a multi-layer anti-metal tag antenna, which is used to design any of the above multi-layer anti-metal tag antennas, including: S1: According to the chip operating frequency and complex impedance, the tag antenna layer is simulated and designed so that the resonant frequency of the tag antenna layer reaches the first resonant frequency that matches the chip operating frequency; the complex impedance of the tag antenna layer is conjugate matched with the complex impedance of the chip; Specifically, in step S1, the tag antenna layer is simulated and designed, including how to design the dual inductor loop 11, the loading bar 12 matched with the dual inductor loop, the T-type matching 13 and the bent dipole 14; step S1 may optionally include: S11: determining a given electrical length and a given width of the bent dipole according to the operating frequency of the chip; Specifically, according to the working frequency of the chip, taking 920 as an example, according to the wavelength formula λ=c / f c , c is the speed of light, f c is the operating frequency of the chip; a half wavelength or a quarter wavelength can be selected to determine the given electrical length of the bent dipole; at this time, the frequency will not change much, and the width will only slightly affect its inductance value. Technical personnel in this field can determine the given width of the bent dipole based on experience according to the antenna impedance and radiation efficiency requirements, which is usually a few millimeters to tens of millimeters.

[0027] S12: Determine the size of the first inductor loop according to the complex impedance of the chip; Specifically, according to the complex impedance Z of the chip c =R c +jX c , according to the inductance formula L=X L / 2πf c , calculate the required inductance value, determine the inductive reactance value range of the antenna loop, and then determine the approximate size of the antenna loop based on the inductive reactance value range, and then determine the size of the outermost inductive loop, i.e., the first inductive loop, in combination with the size requirements of the tag antenna to be designed.

[0028] S13: determining a preset position of the chip, and under the preset condition, calculating a drop range of the inductive reactance of the antenna to determine a size of the second inductive loop; Specifically, the chip can be selected as follows Figure 2 As shown, it is designed in the middle position of the antenna. After the preset position of the chip is determined, due to the loading of the chip, the antenna as a whole is reduced due to the loop, so the inductance value will be reduced. In order to increase the inductance value, it is necessary to embed an inductor ring inside, that is, the second inductor ring; specifically, the specific range of decrease of the inductance value can be calculated according to the reduction degree of the loop, and then the size (diameter, line width, number of turns, etc.) of the second inductor ring can be determined, so that it can basically make up for the decrease in inductance value caused by setting the chip.

[0029] S14: Loading a simulation voltage at a preset position of the chip, and determining the position and size of the loading bar and the T-type matching according to the simulation results.

[0030] Specifically, the dual inductor design will increase the overall inductive reactance of the antenna, and the inductive reactance value will be too large. Therefore, in this step, an analog voltage is loaded at a preset position of the chip. According to the simulation results, the impedance change of the antenna is observed. Through U-shaped loading, there is no contact with the wire to couple with the outer and inner inductive rings. It is preferred to design the U-shaped loading closer to the inner layer and couple more with the chip inductive ring, that is, the second inductive ring, to reduce the overall inductive reactance of the antenna, exchange energy, and couple the collected energy to the chip as much as possible, further increase energy collection, and reduce the inductive reactance value; then fine-tune the T-type matching (fine-tune) to form a strong capacitive coupling with the side of the U-shaped loading.

[0031] S2: According to the chip operating frequency, simulate and design the grounded resonant loading layer so that the resonant frequency of the loading layer reaches a second resonant frequency that matches the chip operating frequency, and the second resonant frequency covers the first resonant frequency; Specifically, step S2 includes: S21: Determine the type, size and arrangement of the resonance bars of the ground resonance loading layer according to the resonance frequency and bandwidth requirements.

[0032] Preferably, first determine how many types of resonant bars are needed based on the resonant frequency and bandwidth requirements; then determine the width of each type of resonant bar based on the frequency; for balanced processing, generally arrange the various types of resonant bars at intervals, and then determine the interval gaps between the resonant bars based on the simulation results.

[0033] Specifically, through simulation optimization, two widths of the resonance bar can be selected, the first resonance bar 31a is 2.5 mm, the second resonance bar 31b is 2 mm, the two are arranged at intervals, and each resonance bar is spaced apart by a gap of 1 mm and 0.5 mm.

[0034] S3: stack and merge the tag antenna layer and the ground resonant loading layer, roughly adjust the thickness of the middle loading layer, and then fine-tune the intrinsic properties of the ground resonant loading layer to meet the design requirements.

[0035] Specifically, due to the combination of the two, a certain degree of coupling will occur. At this time, the thickness of the middle loading layer is roughly adjusted first, and the simulation results are continuously observed. When the thickness of the loading layer makes the simulation results almost close to the design requirements, the gap between the resonant bars is adjusted to fine-tune the eigenmode of the grounded resonant loading layer so that the entire antenna meets the design requirements. The simulation results are shown in Figure 2. Figure 5 shown.

[0036] In this embodiment, a design method for a multi-layer anti-metal tag antenna is provided. The method is based on a single-layer design simulation and then combines the overall idea of ​​coupling optimization. First, the operating frequency and complex impedance of the chip are determined, and the tag antenna layer is simulated and designed. Electromagnetic simulation software (such as HFSS, CST, etc.) can be used to design the tag antenna layer. The geometric parameters (such as length, width, shape, etc.) and material properties of the entire antenna layer are adjusted to make its resonant frequency reach fc; the structural parameters of the antenna layer (such as the position of the feeding point, the shape of the antenna, etc.) are adjusted to make its complex impedance conjugate with the complex impedance of the chip. Then, the structure (such as size, shape, material, etc.) of the grounded resonant loading layer is designed to make its resonant frequency (second resonant frequency) cover the first resonant frequency of the tag antenna layer, ensuring that the range of the second resonant frequency can effectively enhance the antenna performance. Finally, the tag antenna layer and the grounded resonant loading layer are stacked and combined, and the thickness of the intermediate loading layer and the intrinsic parameters of the grounded resonant loading layer are adjusted to verify whether the resonant frequency, impedance matching and radiation performance of the overall structure meet the design requirements through simulation.

[0037] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A multi-layer anti-metal tag antenna, characterized in that: include: A surface tag antenna layer, an intermediate spacer layer, and a bottom ground resonant loading layer; The tag antenna layer includes: a double inductor loop formed by a first inductor loop and a second inductor loop, a loading bar matched with the double inductor loop, a T-type matching and a bent dipole; the loading bar and the T-type matching are arranged on the inner side of the double inductor loop; the bent dipole is arranged on the outer side of the double inductor loop; The resonant loading layer includes a plurality of resonant bars arranged in parallel.

2. The tag antenna according to claim 1, characterized in that: The first inductor loop and the second inductor loop are nested and arranged in the middle of the tag antenna layer.

3. The tag antenna according to claim 1, characterized in that: The loading bar is a U-shaped loading bar, which is arranged between the first inductor ring and the second inductor ring; the opening of the U-shaped loading bar faces the second inductor ring.

4. The tag antenna according to claim 3, characterized in that: The U-shaped loading bar is close to the second inductor ring.

5. The tag antenna according to claim 1, characterized in that: T-type matching is arranged at both ends of the second inductor loop; and a chip is arranged between the two T-type matchings.

6. The tag antenna according to claim 1, characterized in that: The bent dipoles include two bent dipoles, which are respectively located on both sides of the double inductor loop.

7. The tag antenna according to claim 1, characterized in that: The resonant bar comprises at least a first resonant bar and a second resonant bar of different widths; the first resonant bar and the second resonant bar are arranged at an interval.

8. The tag antenna according to claim 7, characterized in that: The first resonant bar is 2.5 mm, the second resonant bar is 2 mm, and they are spaced apart, with a gap of 1 mm and 0.5 mm between each resonant bar.

9. A design method for a multi-layer anti-metal tag antenna, characterized in that: The multi-layer anti-metal tag antenna according to any one of claims 1 to 8 is designed, comprising: S1: According to the chip operating frequency and complex impedance, the tag antenna layer is simulated and designed so that the resonant frequency of the tag antenna layer reaches the first resonant frequency that matches the chip operating frequency; the complex impedance of the tag antenna layer is conjugate matched with the complex impedance of the chip; S2: According to the chip operating frequency, simulate and design the grounded resonant loading layer so that the resonant frequency of the loading layer reaches a second resonant frequency that matches the chip operating frequency, and the second resonant frequency covers the first resonant frequency; S3: Stack and merge the tag antenna layer and the grounded resonant loading layer. According to the simulation results, roughly adjust the thickness of the middle loading layer, and then fine-tune the intrinsic properties of the grounded resonant loading layer to meet the design requirements.

10. The design method according to claim 9, characterized in that: Step S1 includes: S11: determining a given electrical length and a given width of the bent dipole according to the operating frequency of the chip; S12: Determine the size of the first inductor loop according to the complex impedance of the chip; S13: determining a preset position of the chip, and under the preset condition, calculating a drop range of the inductive reactance of the antenna to determine a size of the second inductive loop; S14: Loading a simulation voltage at a preset position of the chip, and determining the position and size of the loading bar and the T-type matching according to the simulation results.

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