Radio frequency gate system

Abstract

The invention discloses a radio frequency gate system, and belongs to the technical field of radio frequency. The radio-frequency door system comprises a radio-frequency door, an electronic tag identification area and a radio-frequency door, wherein the radio-frequency door is internally provided with the electronic tag identification area; the antenna is arranged on the radio frequency door and is opposite to the electronic tag identification area; the refractive index gradient structure is positioned on one side, close to the electronic tag identification area, of the antenna; one side, close to the antenna, of the refractive index gradual change structure is provided with a first cambered surface structure protruding towards the antenna direction, and the refractive index of the first cambered surface structure in the direction away from the arc center is gradually reduced; and the left-handed material electromagnetic array covers the cambered surface of the first cambered surface structure. The antenna beam width can be reduced, the antenna main lobe direction gain can be enhanced, the antenna radiation energy can be concentrated to the electronic tag identification area, and the electronic tag group reading inventory success rate and efficiency can be improved.

Description

Technical Field

[0001] This application belongs to the field of radio frequency technology, and in particular relates to a radio frequency gate system. Background Technology

[0002] To improve inventory efficiency, an RFID gate system is used to scan multiple products with attached RFID tags in a group, quickly confirming product quantity and information.

[0003] The relevant technology achieves antenna coverage of the electronic tag identification area by activating antennas at different locations in the radio frequency gate system. However, the antenna's radiation direction is approximately an omnidirectional hemispherical shape, and the gain of a single antenna is low. This results in low antenna signal strength in some electronic tag identification areas, causing some electronic tags to fail to activate successfully, thus leading to the failure of electronic tag group reading and inventory. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a radio frequency gate system that can narrow the antenna beamwidth, enhance the antenna main lobe directional gain, concentrate the antenna radiated energy to the electronic tag identification area, and improve the success rate and efficiency of electronic tag group reading and inventory.

[0005] In a first aspect, this application provides a radio frequency gate system, comprising: Radio frequency gate, wherein the radio frequency gate has an electronic tag identification area; An antenna is disposed at the radio frequency gate and is positioned opposite to the electronic tag identification area; A refractive index gradient structure is located on the side of the antenna near the electronic tag identification area; the side of the refractive index gradient structure near the antenna has a first arc surface structure that convexes towards the antenna, and the refractive index of the first arc surface structure gradually decreases in the direction away from the arc center; A left-hand material electromagnetic array covers the arc surface of the first arc structure.

[0006] According to the radio frequency gate system of this application, a refractive index gradient structure is set on the side of the antenna near the electronic tag identification area. The side of the refractive index gradient structure near the antenna has a first arc surface structure. The refractive index of the first arc surface structure gradually decreases in the direction away from the arc center. A left-handed material electromagnetic array is set on the arc surface of the first arc surface structure. By utilizing the negative refractive index characteristics of the left-handed material electromagnetic array and the beam-focusing effect of the refractive index gradient structure, the spurious distribution of antenna radiated energy is reduced, the antenna beamwidth is narrowed, and the gain in the direction of the antenna main lobe is enhanced. The antenna radiated energy is concentrated in the electronic tag identification area, thereby improving the success rate and efficiency of electronic tag group reading and inventory.

[0007] According to an embodiment of the present application, the left-handed material electromagnetic array covers the antenna in the orthographic projection of the plane where the antenna is located.

[0008] According to an embodiment of the present application, the left-handed material electromagnetic array is in contact with the antenna. Alternatively, there is a gap between the left-handed material electromagnetic array and the antenna.

[0009] According to an embodiment of the present application, the left-handed material electromagnetic array is attached to the curved surface of the first curved surface structure. Alternatively, the radio frequency door system further comprises a support layer attached to the curved surface of the first curved surface structure, and the left-handed material electromagnetic array is located on the surface of the support layer close to the antenna.

[0010] According to an embodiment of the present application, the left-handed material electromagnetic array comprises a plurality of left-handed material electromagnetic units arranged in an array. The left-handed material electromagnetic unit comprises a combination structure of an open resonant ring and a metal rod, a double cross structure, a single-face double S / U type unit, a dendritic fractal structure, or a liquid crystal control unit. The array distribution comprises a rectangular array distribution, a circular array distribution, or a sparse array distribution.

[0011] According to an embodiment of the present application, the first curved surface structure comprises a plurality of dielectric layers arranged in sequence in the direction away from the arc center. In the direction away from the arc center, the dielectric constant of the plurality of dielectric layers decreases in sequence, the thickness of the plurality of dielectric layers decreases in sequence, and the refractive index of the plurality of dielectric layers decreases in sequence.

[0012] According to an embodiment of the present application, the dielectric layer comprises a polyurethane foam layer. In the direction away from the arc center, the porosity of the plurality of polyurethane foam layers increases in sequence.

[0013] According to an embodiment of the present application, the polyurethane foam layer is formed by injecting water and isocyanate into a polyurethane prepolymer and then foaming. In the direction away from the arc center, the amount of water required to form the plurality of polyurethane foam layers decreases in sequence, the isocyanate index required to form the plurality of polyurethane foam layers increases in sequence, and the foaming time required to form the plurality of polyurethane foam layers decreases in sequence.

[0014] According to an embodiment of the present application, the side of the refractive index gradient structure close to the electronic tag identification area has a second curved surface structure protruding towards the electronic tag identification area. The refractive index of the second curved surface structure gradually decreases in the direction away from the arc center. And / or, the refractive index of the second arc surface structure is between the minimum refractive index and the maximum refractive index of the first arc surface structure.

[0015] According to an embodiment of the present application, the refractive index gradient structure comprises a spherical structure or an ellipsoidal structure; and / or, The first arc surface structure and the second arc surface structure respectively comprise a hemispherical structure or a hemi-ellipsoidal structure.

[0016] The one or more technical solutions in the embodiments of the present application have at least one of the following technical effects: By arranging the refractive index gradient structure on the side of the antenna close to the electronic tag identification area, the side of the refractive index gradient structure close to the antenna has the first arc surface structure, the refractive index of the first arc surface structure gradually decreases in the direction away from the arc center, and the left-handed material electromagnetic array is arranged on the arc surface of the first arc surface structure, the negative refractive index characteristics of the left-handed material electromagnetic array are utilized, and the beam converging effect of the refractive index gradient structure is combined, so that the antenna radiation energy distribution is reduced, the antenna beam width is narrowed, the antenna main lobe direction gain is enhanced, the antenna radiation energy is concentrated to the electronic tag identification area, and the electronic tag group reading and inventory checking success rate and efficiency are improved.

[0017] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the accompanying drawings. Figure 1 is one of the structural schematic diagrams of the radio frequency door system provided by the embodiments of the present application; Figure 2 is another structural schematic diagram of the radio frequency door system provided by the embodiments of the present application; Figure 3 is a structural schematic diagram of the left-handed material electromagnetic array in the radio frequency door system provided by the embodiments of the present application; Figure 4 is a structural schematic diagram of the left-handed material electromagnetic array and the refractive index gradient structure in the radio frequency door system provided by the embodiments of the present application; Figure 5 is one of the sectional views of the refractive index gradient structure in the radio frequency door system provided by the embodiments of the present application; Figure 6 is another sectional view of the refractive index gradient structure in the radio frequency door system provided by the embodiments of the present application; Figure 7 is a comparison diagram of the antenna gain direction in the related art and the embodiments of the present application. DETAILED DESCRIPTION

[0019] The embodiments of the present application are described below in detail, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only, for the purpose of explanation, and are not to be understood as a limitation of the present application.

[0020] The radio frequency door system provided by the embodiments of the present application is described below with reference to the drawings.

[0021] Figure 1 and Figure 2 The radio frequency door system provided by the embodiments of the present application is described below with reference to the drawings.

[0022] As Figure 1 and Figure 2 shown, the radio frequency door system provided by the embodiments of the present application includes a radio frequency door 1, an antenna 2, a refractive index gradient structure 3, and a left-handed material electromagnetic array 4.

[0023] The radio frequency door 1 has an electronic tag identification area 11 therein. The radio frequency door 1 includes a plurality of door bodies, and the electronic tag identification area 11 is located between the plurality of door bodies. For example Figure 1 shown, the radio frequency door 1 includes two door bodies arranged oppositely, and the electronic tag identification area 11 is located between the two door bodies. For another example Figure 2 shown, the radio frequency door 1 includes three door bodies, two of which (a first door body and a second door body) are arranged oppositely, and the other door body (a third door body) is located on top of the first door body and the second door body, and the area surrounded by the three door bodies can be the electronic tag identification area 11. The radio frequency door 1 is usually made of injection molding materials.

[0024] The electronic tag identification area 11 is an area for identifying electronic tags (RFID electronic tags). When a plurality of products enter the electronic tag identification area 11 and each product is attached with an electronic tag, the radio frequency door system can identify the electronic tags of the plurality of products in the electronic tag identification area 11 to conduct group reading and inventory of the plurality of products, and quickly confirm the product quantity and product information.

[0025] The antenna 2 is arranged on the radio frequency door 1. The antenna 2 can be arranged on the door body of the radio frequency door 1, such as being arranged on the surface of the door body near the electronic tag identification area 11. As Figure 1 and Figure 2 shown, the antenna 2 can also be arranged inside the door body of the radio frequency door 1.

[0026] The antenna 2 is arranged opposite to the electronic tag identification area 11. The antenna 2 emits electromagnetic waves of a specific frequency (e.g. 920-925 MHz) to form a radio frequency field covering the electronic tag identification area 11. When the signal intensity radiated by the antenna 2 reaches the activation sensitivity of the electronic tags in the electronic tag identification area 11, the electronic tags can be quickly identified and determined, thereby realizing the quick inventory of multiple products.

[0027] The number of the antenna 2 can be one or more. Multiple antennas 2 can be arranged at multiple door bodies of the radio frequency door 1, and each antenna 2 is arranged opposite to the electronic tag identification area 11.

[0028] The antenna 2 can include a patch antenna, which works independently and has a small volume and is easy to integrate. Multiple antennas 2 can also form a phased array antenna. By adjusting the phase of each antenna in the phased array antenna, the direction of the antenna beam can be changed, the radiation beam can be narrowed, and the maximum directional antenna gain can be improved, thereby realizing the scanning of the electronic tag identification area 11 by the antenna radiation beam.

[0029] The refractive index gradient structure 3 is arranged on the side of the antenna 2 close to the electronic tag identification area 11, i.e. the refractive index gradient structure 3 is arranged between the antenna 2 and the electronic tag identification area 11, and the refractive index gradient structure 3 is arranged close to the antenna 2. When the antenna 2 is arranged inside the door body of the radio frequency door 1, the refractive index gradient structure 3 can be arranged on the door body, as shown in FIG. 2, the refractive index gradient structure 3 is arranged on the surface of the door body close to the electronic tag identification area 11; as shown in FIG. 3, the refractive index gradient structure 3 can also be arranged inside the door body of the radio frequency door 1. Figure 1 Figure 2

[0030] The side of the refractive index gradient structure 3 close to the antenna 2 has a first arc surface structure 31 protruding towards the antenna 2. The surface of the side of the first arc surface structure 31 close to the antenna 2 is an arc surface, and the arc surface protrudes towards the antenna 2.

[0031] The refractive index of the first arc surface structure 31 gradually decreases in the direction away from the arc center, i.e. the refractive index of the first arc surface structure 31 is larger at the position close to the arc center and smaller at the position close to the arc surface. In the direction away from the arc center of the first arc surface structure 31, the refractive index of the first arc surface structure 31 can change uniformly or non-uniformly (e.g. gradient change). The first arc surface structure 31 is used to continuously refract the incident electromagnetic waves to focus on the electronic tag identification area 11.

[0032] ​​In the case that the number of antennas 2 is multiple, the number of refractive index gradient structures 3 can be multiple. The multiple refractive index gradient structures 3 are arranged one-to-one with the multiple antennas 2, each refractive index gradient structure 3 is located on the side close to the electronic tag identification area 11 of the corresponding antenna 2, and the side close to the corresponding antenna 2 of each refractive index gradient structure 3 has a first arc surface structure 31 protruding towards the corresponding antenna 2.

[0033] The left-handed material electromagnetic array 4 covers the arc surface of the first arc surface structure 31. The left-handed material electromagnetic array 4 can be curved in an arc shape, and the arc surface of the left-handed material electromagnetic array 4 matches the arc surface of the first arc surface structure 31, so that the left-handed material electromagnetic array 4 is fitted with the arc surface of the first arc surface structure 31. The left-handed material electromagnetic array 4 is used to generate induced current by the antenna 2 electromagnetic wave, realize negative refractive index characteristics, and regulate the electromagnetic wave propagation path.

[0034] In the case that the number of refractive index gradient structures 3 is multiple, the number of left-handed material electromagnetic arrays 4 can be multiple. The multiple left-handed material electromagnetic arrays 4 are arranged one-to-one with the multiple refractive index gradient structures 3, and each left-handed material electromagnetic array 4 covers the arc surface of the first arc surface structure 31 in the corresponding refractive index gradient structure 3.

[0035] In some embodiments, the radio frequency door system further comprises a reader-writer (not shown in the figure), which is connected with the antenna 2. The reader-writer transmits electromagnetic waves of a specific frequency to the electronic tag identification area 11 through the antenna 2, when multiple products with attached electronic tags enter the electronic tag identification area 11, the electronic tags are activated by receiving electromagnetic wave energy, and feedback the stored information (such as ID, etc.) to the antenna 2, the antenna 2 transmits the information feedback by the electronic tag to the reader-writer, and the reader-writer decodes and processes the information to complete the identification of the electronic tag.

[0036] The radio frequency door system in the related art mostly uses patch antennas to work independently, and realizes signal coverage of the antenna to the electronic tag identification area by activating patch antennas at different positions respectively. However, the radiation direction of the patch antenna is approximately a hemispherical shape of omnidirectional radiation, the gain of a single antenna is low, and the signal strength of the antenna in part of the identification area is low, which leads to that part of the electronic tags cannot be activated smoothly, and further leads to the failure of electronic tag group reading and inventory. In order to improve the maximum directional antenna gain, the related art groups multiple patch antennas into a phased array antenna. However, the size of the radio frequency door is limited, and each door body of the radio frequency door usually has a phased array antenna composed of two patch antennas, at this time, the beam width of the phased array antenna is only reduced by 50% compared with the beam width of a single antenna, and part of the radiation energy of the antenna is still scattered and distributed and cannot be concentrated in the electronic tag identification area, which leads to the problem that the signal in part of the electronic tag identification area is still weak.

[0037] The embodiment is provided with a refractive index gradient structure 3 on the side of the antenna 2 (such as each antenna in a patch antenna or phased array antenna) close to the electronic tag identification area 11. The side of the refractive index gradient structure 3 close to the antenna 2 is provided with a first arc surface structure 31, the refractive index of the first arc surface structure 31 gradually decreases in the direction away from the arc center, and a left-handed material electromagnetic array 4 is arranged on the arc surface of the first arc surface structure 31. The negative refractive index characteristics of the left-handed material electromagnetic array 4 are utilized, and the beam converging effect of the refractive index gradient structure 3 is combined to realize the refraction of the large incidence angle electromagnetic beam to the inside of the refractive index gradient structure 3, reduce the stray distribution of the antenna radiation energy, effectively narrow the antenna beam width, enhance the main lobe direction gain, and concentrate the antenna radiation energy to the electronic tag identification area 11, thereby improving the success rate and efficiency of the electronic tag group reading and inventory checking.

[0038] In some embodiments, the left-handed material electromagnetic array 4 covers the antenna 2 in the orthographic projection of the plane where the antenna 2 is located. The size of the orthographic projection of the left-handed material electromagnetic array 4 in the plane where the antenna 2 is located can be greater than or equal to the size of the antenna 2, so as to ensure that the electromagnetic waves of the antenna 2 can pass through the left-handed material electromagnetic array 4 and the refractive index gradient structure 3 to be gathered to the electronic tag identification area 11.

[0039] The size of the orthographic projection of the left-handed material electromagnetic array 4 in the plane where the antenna 2 is located cannot be too large, for example, the size of the orthographic projection of the left-handed material electromagnetic array 4 in the plane where the antenna 2 is located is not more than twice the size of the antenna 2, so as to avoid the left-handed material electromagnetic array 4 and the refractive index gradient structure 3 occupying too much volume.

[0040] It should be noted that the size of the orthographic projection of the left-handed material electromagnetic array 4 in the plane where the antenna 2 is located can also be slightly smaller than the size of the antenna 2, but the size of the orthographic projection of the left-handed material electromagnetic array 4 in the plane where the antenna 2 is located is not less than 0.8 times the size of the antenna 2, so as to ensure that at least most of the electromagnetic waves of the antenna 2 pass through the left-handed material electromagnetic array 4 and the refractive index gradient structure 3 to be gathered to the electronic tag identification area 11, while reducing the volume occupied by the left-handed material electromagnetic array 4 and the refractive index gradient structure 3.

[0041] In some embodiments, the antenna 2 includes an antenna radiation patch. The antenna radiation patch is the core part of the antenna 2, and is used to capture and radiate electromagnetic waves. The antenna radiation patch is a metal sheet (such as copper), and the shape can include a rectangle, a circle, a ring, etc.

[0042] The size of the antenna radiation patch is smaller than the size of the antenna 2. The left-handed material electromagnetic array 4 covers the antenna radiation patch in the orthographic projection of the plane where the antenna 2 is located, and the size of the left-handed material electromagnetic array 4 in the plane where the antenna 2 is located is greater than or equal to the size of the antenna radiation patch, so as to ensure that the electromagnetic waves of the antenna 2 can be completely collected to the electronic tag identification area 11 through the left-handed material electromagnetic array 4 and the refractive index gradient structure 3, while reducing the volume occupied by the left-handed material electromagnetic array 4 and the refractive index gradient structure 3.

[0043] In some embodiments, the left-handed material electromagnetic array 4 is in contact with the antenna 2. The left-handed material electromagnetic array 4 can be located on the surface of the antenna 2 on the side close to the electronic tag identification area 11, so as to shorten the transmission path of the electromagnetic waves and reduce the loss.

[0044] In some embodiments, there is a gap between the left-handed material electromagnetic array 4 and the antenna 2. The width of the gap can be 1mm-10mm. The left-handed material electromagnetic array 4 and the antenna 2 are slightly spaced apart, so as to reduce the reflection of the contact surface.

[0045] In some embodiments, the left-handed material electromagnetic array 4 is attached to the arc surface of the first arc surface structure 31. The left-handed material electromagnetic array 4 can be directly attached to the arc surface of the first arc surface structure 31, that is, the left-handed material electromagnetic array 4 is in direct contact with the first arc surface structure 31.

[0046] In some embodiments, the radio frequency door system further comprises a support layer, the support layer is attached to the arc surface of the first arc surface structure 31, and the left-handed material electromagnetic array 4 is located on the surface of the support layer on the side close to the antenna 2.

[0047] The support layer is used to carry the left-handed material electromagnetic array 4. The left-handed material electromagnetic array 4 is formed on the support layer, and the side of the support layer away from the left-handed material electromagnetic array 4 is attached to the arc surface of the first arc surface structure 31. The left-handed material electromagnetic array 4 is not in direct contact with the first arc surface structure 31, and the left-handed material electromagnetic array 4 is in contact with the first arc surface structure 31 through the support layer.

[0048] The material of the support layer can include polyimide, FR4 board, flexible ceramic, or polyvinyl chloride (PVC), etc.

[0049] In this embodiment, the left-handed material electromagnetic array 4 is first formed on the support layer, and then the left-handed material electromagnetic array 4 and the support layer are attached to the arc surface of the first arc surface structure 31 as a whole, so that the manufacturing is simpler.

[0050] In some embodiments, as shown in FIG. 6, the left-handed material electromagnetic array 4 is attached to the arc surface of the first arc surface structure 31, and the support layer is not provided. Figure 3As shown, the left-handed material electromagnetic array 4 includes a plurality of left-handed material electromagnetic units 41 arranged in an array. The left-handed material electromagnetic units 41 include a combination structure of an open resonant ring and a metal rod, a double-cross structure, a single-face double-S / U unit, a dendritic fractal structure, or a liquid crystal control unit.

[0051] A left-handed material is an artificially synthesized material with special electromagnetic properties, and its core feature is that the dielectric constant and the magnetic permeability are both negative. Through the combination of carefully designed magnetic resonant and electric resonant units, this type of material can realize the phenomenon that the electromagnetic wave propagation direction is opposite to the energy flow direction.

[0052] In the combination structure of an open resonant ring and a metal rod, the open resonant ring is used to generate magnetic resonance, and the metal rod array is used to generate electric resonance. Through the combination of the two, negative dielectric constant and negative magnetic permeability can be achieved.

[0053] The double-cross structure is a single-face structure in which two cross-shaped metal wires are placed side by side on a dielectric substrate, integrating electric resonators and magnetic resonators in one. By optimizing the structure size, wideband low-loss left-handed properties can be achieved.

[0054] The single-face double-S / U unit utilizes the coupling effect between the front and back structures of the unit dielectric plate to achieve negative magnetic permeability characteristics. It is simple to construct, has low loss, and has a wide bandwidth.

[0055] The dendritic fractal structure achieves multi-band resonance through multiple branches. For example, the large dendritic branches produce magnetic resonance (negative magnetic permeability) at low frequencies, and the small dendritic branches produce electric resonance (negative dielectric constant) at high frequencies. By adjusting the branch length, line width, and spacing, the resonance frequency can be controlled.

[0056] The liquid crystal control unit utilizes the electro-optic effect of liquid crystal materials, and through an external electric field, it controls the arrangement of liquid crystal molecules, thereby changing the electromagnetic properties of the left-handed material. It has dynamic adjustability and can adjust the performance parameters of the left-handed material in real time according to needs.

[0057] The left-handed material electromagnetic units 41 can also include other structure types, and the structure type of the left-handed material electromagnetic units 41 can be set according to actual needs, which is not specifically limited here.

[0058] The following will take the combination structure of an open resonant ring and a metal rod as an example to explain in detail.

[0059] As shown in FIG. 2, the left-handed material electromagnetic array 4 includes a plurality of left-handed material electromagnetic units 41 arranged in an array. The left-handed material electromagnetic units 41 include a combination structure of an open resonant ring and a metal rod. Figure 3As shown, the left-handed material electromagnetic unit 41 includes a combination structure of an open resonant ring and a metal rod 42. The open resonant ring includes an inner ring 43 and an outer ring 44, the inner ring 43 is located inside the outer ring 44, and the center points of the inner ring 43 and the outer ring 44 coincide. The inner ring 43 has an opening, the outer ring 44 has an opening, and the openings of the inner ring 43 and the outer ring 44 are arranged away from each other. The metal rod 42 is located outside the outer ring 44 and is arranged close to the opening of the outer ring 44. Among them, the inner ring 43 and the outer ring 44 can be circular or rectangular, and the metal rod 42 can be linear.

[0060] When the electromagnetic wave is vertically incident, the equivalent inductance formed by the openings of the open resonant ring and the inter-ring capacitance form an LC resonant circuit, which produces a strong electromagnetic response at a specific frequency. By adjusting the inter-ring spacing, opening width, metal wire width and other parameters, the resonant frequency point can be accurately controlled.

[0061] When the electric field component of the electromagnetic wave is parallel to the metal rod 42, the free electrons form an oscillating current in the metal rod 42, generating an equivalent electric dipole moment. At the resonant frequency, the equivalent permittivity of this structure can reach -4.5. The spatial arrangement of the two structures follows the complementary principle. A typical configuration uses a three-dimensional orthogonal stacking method, with the magnetic resonant unit plane perpendicular to the direction of electromagnetic wave propagation, and the electric resonant unit parallel to the direction of propagation.

[0062] The working frequency band of RFID is 920MHz to 925MHz. In order to match this working frequency band, the sizes of the inner ring 43, the outer ring 44 and the metal rod 42 are set. Among them, the inner ring 43 and the outer ring 44 are circular. The size of the outer ring 44 is approximately 0.5 times the wavelength, the radius of the outer ring 44 can be 25mm, the line width can be 2mm, and the width of the opening of the outer ring 44 can be 1.5mm. By adjusting the size of the outer ring 44, the capacitance value can be controlled, and the resonant frequency is affected. The size of the inner ring 43 is about 83% of the size of the outer ring 44, and the radius of the inner ring 43 can be 21mm. By adjusting the size of the inner ring 43, the unit dual-negative bandwidth can be optimized. The length of the metal rod 42 can be 13mm, the width can be 2mm, and the spacing between the metal rod 42 and the outer ring 44 can be 1mm. The metal rod 42 is parallel to the electric field polarization direction, and adjusting the size of the metal rod 42 can adjust the negative permittivity performance of the unit at the frequency point of 920MHz.

[0063] In addition, the unit period is less than 0.25 times the wavelength to avoid Bragg scattering and meet the subwavelength condition. The unit period can be 27mm, that is, the spacing between the center points of the adjacent two left-handed material electromagnetic units 41 can be 27mm.

[0064] In some embodiments, the array distribution includes a rectangular array distribution, a circular array distribution, or a sparse array distribution.

[0065] The rectangular array distribution refers to that the plurality of left-handed material electromagnetic units 41 are arranged in a regular grid of rows and columns to form a rectangular structure, as shown in FIG. 8. Figure 3 The circular array distribution refers to that the plurality of left-handed material electromagnetic units 41 are uniformly distributed on a circumference to form a circular structure. The sparse array distribution reduces the number of left-handed material electromagnetic units 41 through non-uniform distribution (such as random, spiral, or optimization algorithm).

[0066] The distribution mode of the plurality of left-handed material electromagnetic units 41 can be set according to actual needs. By optimizing the arrangement mode of the left-handed material electromagnetic units 41, the beam directivity can be optimized, and the gain can be improved.

[0067] In some embodiments, the material of the left-handed material electromagnetic unit 41 can include copper, aluminum, silver paste, or conductive ink, etc.

[0068] It should be noted that the left-handed material electromagnetic units 41 in the left-handed material electromagnetic array 4 can be individually made and then pasted on the arc surface of the first arc surface structure 31 according to the array distribution. The left-handed material electromagnetic array 4 can also be divided into multiple petals and pasted as an integrated structure.

[0069] In some embodiments, in combination with FIG. 9, the first arc surface structure 31 includes a plurality of dielectric layers (i.e., a first dielectric layer) arranged in sequence in a direction away from the arc center O. Figure 4 to Figure 6 In the direction away from the arc center O, the dielectric constant of the plurality of dielectric layers decreases in sequence, the thickness of the plurality of dielectric layers decreases in sequence, and the refractive index of the plurality of dielectric layers decreases in sequence.

[0070] Among the plurality of dielectric layers, the closer to the arc center O of the first arc surface structure 31, the greater the refractive index; the closer to the arc surface of the first arc surface structure 31, the smaller the refractive index. The refractive index of the plurality of dielectric layers can change uniformly or non-uniformly (such as gradient change).

[0071] The refractive index of the plurality of dielectric layers can be adjusted by the dielectric constant and the thickness. Among the plurality of dielectric layers, the closer to the arc center O of the first arc surface structure 31, the greater the dielectric constant and the thickness, so that the refractive index is greater; the closer to the arc surface of the first arc surface structure 31, the smaller the dielectric constant and the thickness, so that the refractive index is smaller.

[0072] For example, Figure 5 and Figure 6As shown, the plurality of dielectric layers of the first curved surface structure 31 includes, in order from the direction away from the arc center O, the dielectric layer 31a, the dielectric layer 31b, the dielectric layer 31c, the dielectric layer 31d, the dielectric layer 31e, the dielectric layer 31f, and the dielectric layer 31g. The dielectric constant of the dielectric layer 31a to the dielectric layer 31g decreases in order, the thickness decreases in order, and the refractive index decreases in order, that is, the dielectric constant of the dielectric layer 31a is the largest, the thickness is the largest, and the refractive index is the largest; the dielectric constant of the dielectric layer 31g is the smallest, the thickness is the smallest, and the refractive index is the smallest.

[0073] The dielectric constant of each dielectric layer of the first curved surface structure 31 can be ε(r) = 2-(r / R) 2 , where ε(r) is the dielectric constant of the dielectric layer, r is the distance between the dielectric layer and the arc center O, and R is the distance between the curved surface of the first curved surface structure 31 and the arc center O. In the case of a spherical structure of the first curved surface structure 31, r is the radius of the dielectric layer, and R is the radius of the first curved surface structure 31. The refractive index of each dielectric layer of the first curved surface structure 31 is n(r) = ε(r) 1 / 2 . Since the first curved surface structure 31 needs to achieve a focusing effect, in the direction away from the arc center O, the refractive index of the plurality of dielectric layers decreases in order, and at this time the propagation path of the electromagnetic wave in the first curved surface structure 31 satisfies the equal optical path condition.

[0074] The dielectric constant of the first curved surface structure 31 is between 1 and 2. For example, the dielectric constants of the dielectric layer 31a to the dielectric layer 31g can be 1.97, 1.81, 1.58, 1.36, 1.19, 1.08, and 1.02, respectively. In order to better reduce the reflection of electromagnetic waves between layers, in the direction away from the arc center O, the thickness of the plurality of dielectric layers decreases in order to reduce the impedance matching loss. For example, the thicknesses of the dielectric layer 31a to the dielectric layer 31g can be 32 mm, 28 mm, 21 mm, 15 mm, 10 mm, 6 mm, and 3 mm, respectively. It should be noted that in the case of a spherical structure of the first curved surface structure 31, the dielectric layer 31a is in a spherical structure, and the thickness of the dielectric layer 31a is the diameter of the dielectric layer 31a.

[0075] In some embodiments, the number of dielectric layers of the first curved surface structure 31 can be greater than or equal to 7 to improve the beam convergence effect of the first curved surface structure 31.

[0076] In some embodiments, the dielectric layer includes a polyurethane foam layer. In the direction away from the arc center O, the porosities of the plurality of polyurethane foam layers increase in order.

[0077] The embodiment adjusts the dielectric constant of the polyurethane foam layer by adjusting the porosity of the polyurethane foam layer, thereby adjusting the refractive index of the polyurethane foam layer. In the O direction away from the arc center, the porosities of the plurality of polyurethane foam layers increase in turn, so that the dielectric constants of the plurality of polyurethane foam layers decrease in turn, and the refractive indexes of the plurality of polyurethane foam layers decrease in turn.

[0078] For example Figure 5 and Figure 6 As shown in FIG. 31, the porosities of the first dielectric layer 31a to the seventh dielectric layer 31g increase in turn, the dielectric constants decrease in turn, and the refractive indexes decrease in turn, that is, the porosity of the first dielectric layer 31a is the smallest, the dielectric constant is the largest, and the refractive index is the largest; the porosity of the seventh dielectric layer 31g is the largest, the dielectric constant is the smallest, and the refractive index is the smallest.

[0079] The embodiment adjusts the refractive index change of the first arc surface structure 31 by adjusting the porosity of the polyurethane foam layer, reduces the complexity of material production, and improves production efficiency and production accuracy.

[0080] In some embodiments, the polyurethane foam layer is formed by foaming after injecting water and isocyanate into the polyurethane prepolymer. In the direction away from the arc center O, the water injection amount required to form the plurality of polyurethane foam layers decreases in turn, the isocyanate index required to form the plurality of polyurethane foam layers increases in turn, and the foaming time required to form the plurality of polyurethane foam layers decreases in turn.

[0081] Taking the first arc structure 31 as a spherical structure as an example, in the process of preparing the first arc structure 31, a foaming mold and a polyurethane foam material are prepared, a plurality of semicircular ring molds are provided for each dielectric layer, one end of which is for feeding and the other end is for discharging and exhausting, a spiral semicircular arc structure is provided at the feeding port for stirring the foaming material, and a hollow semisphere is used as the inner core mold. The feeding port, the exhaust port and the stirring structure are the same as those of other layers.

[0082] In the direction away from the arc center O, a plurality of polyurethane foam layers are sequentially prepared. When preparing each polyurethane foam layer, water and isocyanate are injected into the polyurethane prepolymer under room temperature conditions, and foaming is performed based on the foaming time. The foaming rate is controlled by controlling the water injection amount and the isocyanate index, and the porosity of the formed polyurethane foam layer is controlled by controlling the foaming time, so as to adjust the dielectric constant. After forming the polyurethane foam layer, the polyurethane foam layer is demolded from the mold and the excess foam at the discharge port is removed.

[0083] Wherein, the greater the water injection amount, the smaller the isocyanate index, the longer the foaming time, the smaller the foaming rate, the smaller the porosity of the formed polyurethane foam layer, and the larger the dielectric constant; the smaller the water injection amount, the larger the isocyanate index, the shorter the foaming time, the greater the foaming rate, the greater the porosity of the formed polyurethane foam layer, and the smaller the dielectric constant.

[0084] For exampleFigure 5 and Figure 6 As shown in FIG. 6, the greater the water injection amount required by the first dielectric layer 31a to the seventh dielectric layer 31g, the smaller the isocyanate index, the smaller the foaming time, the greater the porosity, and the smaller the dielectric constant. For example, the water injection amount required by the first dielectric layer 31a to the seventh dielectric layer 31g can be 3 parts, 2.8 parts, 2.6 parts, 2.4 parts, 2.1 parts, 1.7 parts, and 1.5 parts, respectively. The isocyanate index required by the first dielectric layer 31a to the seventh dielectric layer 31g can be 0.98 parts, 1 part, 1 part, 1.01 parts, 1.02 parts, 1.03 parts, and 1.05 parts, respectively. The foaming time required by the first dielectric layer 31a to the seventh dielectric layer 31g can be 240s-250s, 210s-220s, 180s-200s, 150s-160s, 120s-130s, 90s-100s, and 60s-70s, respectively. Among them, the interlayer foaming time difference is greater than or equal to 25s.

[0085] After forming each polyurethane foam layer, the plurality of polyurethane foam layers form the first arc surface structure 31. The plurality of polyurethane foam layers can be bonded by glue, or bonded by adhesive film, or connected by hollow tube column structure.

[0086] This embodiment utilizes different water injection amounts, isocyanate indexes, and foaming times in the polyurethane foam foaming process to form polyurethane foam layers with different porosities, greatly reducing the complexity of material production, and improving production efficiency and production accuracy.

[0087] In some embodiments, the first arc surface structure 31 includes a hemispherical structure or a hemi-ellipsoidal structure, and the arc center O of the first arc surface structure 31 is the center of the sphere. When the first arc surface structure 31 is a hemispherical structure, the dielectric layer located at the arc center O (such as the first dielectric layer 31a) is a hemispherical structure, and the other dielectric layers (such as the second dielectric layer 31b to the seventh dielectric layer 31g) are respectively half-ring structures. When the first arc surface structure 31 is a hemi-ellipsoidal structure, the dielectric layer located at the arc center O (such as the first dielectric layer 31a) is a hemi-ellipsoidal structure, and the other dielectric layers (such as the second dielectric layer 31b to the seventh dielectric layer 31g) are respectively hemi-ellipsoidal ring structures.

[0088] It should be noted that the refractive index gradient structure 3 can only include the first arc surface structure 31, that is, the first arc surface structure 31 constitutes the refractive index gradient structure 3. The refractive index gradient structure 3 can also include the first arc surface structure 31 and other structures, and the other structures are located on the side of the refractive index gradient structure 3 close to the electronic tag identification area 11.

[0089] In some embodiments, in combination with Figure 4 to Figure 6As shown, the refractive index gradient structure 3 has a second arcuate structure 32 that protrudes towards the electronic tag recognition area 11 on the side near the electronic tag recognition area 11. The surface of the second arcuate structure 32 near the electronic tag recognition area 112 is arcuate, and this arcuate surface protrudes towards the electronic tag recognition area 11.

[0090] The second arc-shaped structure 32 may have the same or different structure as the first arc-shaped structure 32, and the curvature of the second arc-shaped structure 32 may be the same or different from that of the first arc-shaped structure 32. The second arc-shaped structure 32 may be a single-layer structure or a multi-layer structure.

[0091] In some embodiments, the refractive index of the second arcuate structure 32 gradually decreases in the direction away from the arc center; that is, the refractive index of the second arcuate structure 32 is greater closer to its arc center and smaller closer to its arc surface. In the direction away from the arc center of the second arcuate structure 32, the refractive index of the second arcuate structure 32 can vary uniformly or non-uniformly (e.g., gradient variation).

[0092] In some embodiments, the second arcuate structure 32 may include a plurality of dielectric layers (i.e., second dielectric layers) sequentially disposed in a direction away from its arc center. In the direction away from the arc center, the dielectric constant of the plurality of second dielectric layers decreases sequentially, the thickness of the plurality of second dielectric layers decreases sequentially, and the refractive index of the plurality of second dielectric layers decreases sequentially.

[0093] The number of dielectric layers in the second arc surface structure 32 and the first arc surface structure 31 may be the same or different, and the dielectric constant and thickness of each dielectric layer in the second arc surface structure 32 and the first arc surface structure 31 may be the same or different.

[0094] As an example, the number of dielectric layers in the second arc-shaped structure 32 is the same as that in the first arc-shaped structure 31, and the multiple dielectric layers in the second arc-shaped structure 32 are arranged one-to-one with the multiple dielectric layers in the first arc-shaped structure 31. The dielectric constant and thickness of the dielectric layers arranged in the second arc-shaped structure 32 and the first arc-shaped structure 31 are the same. The dielectric layers arranged in the second arc-shaped structure 32 and the first arc-shaped structure 31 can be integrally formed structures.

[0095] like Figure 5 As shown, the second arcuate structure 32 comprises multiple second dielectric layers, namely dielectric layer 32a, dielectric layer 32b, dielectric layer 32c, dielectric layer 32d, dielectric layer 32e, dielectric layer 32f, and dielectric layer 32g, arranged sequentially in a direction away from the arc center. The dielectric constant, thickness, and refractive index of dielectric layers 32a to 32g decrease sequentially, i.e., dielectric layer 32a has the largest dielectric constant, the largest thickness, and the largest refractive index; dielectric layer 32g has the smallest dielectric constant, the smallest thickness, and the smallest refractive index.

[0096] The dielectric constant and thickness of the dielectric layer 32a and the dielectric layer 31a are the same, and the dielectric layer 32a and the dielectric layer 31a can be an integrally formed structure. The dielectric constant and thickness of the dielectric layer 32b and the dielectric layer 31b are the same, and the dielectric layer 32b and the dielectric layer 31b can be an integrally formed structure. Similarly, the dielectric constant and thickness of the dielectric layer 32g and the dielectric layer 31g are the same, and the dielectric layer 32g and the dielectric layer 31g can be an integrally formed structure.

[0097] It can be understood that the number of dielectric layers in the second arc surface structure 32 can also be greater than or less than the number of dielectric layers in the first arc surface structure 31, as long as the refractive index of the plurality of dielectric layers in the second arc surface structure 32 decreases in the direction away from the arc center.

[0098] The plurality of dielectric layers in the second arc surface structure 32 in the embodiment have refractive indexes that decrease in the direction away from the arc center, which can further narrow the antenna beam width and concentrate the antenna radiation energy to the electronic tag identification area 11.

[0099] In some embodiments, each dielectric layer in the second arc surface structure 32 includes a polyurethane foam layer. In the direction away from the arc center of the second arc surface structure 32, the porosity of the plurality of polyurethane foam layers in the second arc surface structure 32 increases in turn.

[0100] The preparation method of the polyurethane foam layer in the second arc surface structure 32 is the same as that of the polyurethane foam layer in the first arc surface structure 31, which will not be described in detail here.

[0101] In some embodiments, as shown in FIG. 2B, the refractive index of the second arc surface structure 32 is between the minimum refractive index and the maximum refractive index of the first arc surface structure 31. Figure 6

[0102] The second arc surface structure 32 can be a single-layer structure. The refractive index at each position of the second arc surface structure 32 is the same. The refractive index of the second arc surface structure 32 can be the intermediate refractive index of the first arc surface structure 31 or close to the intermediate refractive index of the first arc surface structure 31. The intermediate refractive index of the first arc surface structure 31 can be the average of the minimum refractive index and the maximum refractive index of the first arc surface structure 31. For example, the first arc surface structure 31 includes the dielectric layer 31a to the dielectric layer 31g, the minimum refractive index of the first arc surface structure 31 is the refractive index of the dielectric layer 31g, i.e., 1.02, the maximum refractive index of the first arc surface structure 31 is the refractive index of the dielectric layer 31a, i.e., 1.97, and the refractive index of the second arc surface structure 32 can be 1.5.

[0103] ​The second curved surface structure 32 can also be a multi-layer structure. The refractive index of the second curved surface structure 32 gradually decreases in the direction away from the arc center, and the refractive index of the second curved surface structure 32 is between the minimum refractive index and the maximum refractive index of the first curved surface structure 31. For example, the second curved surface structure 32 includes a plurality of dielectric layers (i.e., second dielectric layers) arranged in order in the direction away from the arc center thereof. In the direction away from the arc center, the refractive index of the plurality of second dielectric layers decreases in order, and the maximum refractive index of the plurality of second dielectric layers is less than the maximum refractive index of the first curved surface structure 31, and the minimum refractive index of the plurality of second dielectric layers is greater than the minimum refractive index of the first curved surface structure 31.

[0104] The refractive index of the second curved surface structure 32 in the embodiment is between the minimum refractive index and the maximum refractive index of the first curved surface structure 31, so as to ensure that the antenna radiation energy covers the electronic tag identification area 11 while narrowing the antenna beam width and increasing the antenna gain.

[0105] In some embodiments, the second curved surface structure 32 can include a hemispherical structure or a hemi-ellipsoidal structure.

[0106] When the first curved surface structure 31 and the second curved surface structure 32 are both hemispherical structures, the radii of the first curved surface structure 31 and the second curved surface structure 32 can be the same, so that the first curved surface structure 31 and the second curved surface structure 32 form a complete spherical structure, and the arc centers of the first curved surface structure 31 and the second curved surface structure 32 are the same, both being the sphere center. When the first curved surface structure 31 and the second curved surface structure 32 are both hemi-ellipsoidal structures, the radii (three half-axis lengths) of the first curved surface structure 31 and the second curved surface structure 32 can be the same, so that the first curved surface structure 31 and the second curved surface structure 32 form a complete ellipsoidal structure, and the arc centers of the first curved surface structure 31 and the second curved surface structure 32 are the same, both being the sphere center.

[0107] In some embodiments, the refractive index gradient structure 3 includes a spherical structure or an ellipsoidal structure.

[0108] When the refractive index gradient structure 3 is a spherical structure, the first curved surface structure 31 and the second curved surface structure 32 can both be partial spherical structures. When the refractive index gradient structure 3 is an ellipsoidal structure, the first curved surface structure 31 and the second curved surface structure 32 can both be partial ellipsoidal structures.

[0109] Figure 7 The following is a comparison chart of the E-plane and H-plane gain directions of the related art and the antenna in the embodiment. The antenna in the related art is a patch antenna, the antenna in the embodiment is a patch antenna, the refractive index gradient structure is a spherical structure, and the structures of the first curved surface structure 31 and the second curved surface structure 32 are the same. From the chart, it can be seen that the antenna in the embodiment has a wider beam width and a higher gain than the antenna in the related art. Figure 7It can be seen that, compared with the related art, the beam width of the embodiment is significantly reduced, the forward maximum gain is increased from 11.68dB to 17.29dB, the antenna gain of the embodiment in the range of ±30° is better than that of the related art, and the gain at 36° angle is decreased from 8.32dB to 1.82dB. The embodiment effectively improves the antenna radiation directivity, and improves the group reading success rate through the improvement of the antenna gain.

[0110] According to the radio frequency door system provided by the embodiment of the application, the refractive index gradient structure is arranged on the side of the antenna close to the electronic tag identification area, the side of the refractive index gradient structure close to the antenna has a first curved surface structure, the refractive index of the first curved surface structure gradually decreases in the direction away from the arc center, and a left-handed material electromagnetic array is arranged on the curved surface of the first curved surface structure. The negative refractive index characteristics of the left-handed material electromagnetic array are used, and the beam is converged by the refractive index gradient structure, so that the antenna radiation energy distribution is reduced, the antenna beam width is narrowed, the antenna main lobe direction gain is enhanced, the antenna radiation energy is concentrated to the electronic tag identification area, and the electronic tag group reading inventory success rate and efficiency are improved.

[0111] The terms "first", "second", and the like in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are usually a class, not limited to the number of objects, for example, the first object can be one or more.

[0112] In the description of the present application, the meaning of "a plurality of" is two or more.

[0113] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0114] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A radio frequency gate system, characterized by The application relates to a radio frequency door system. The radio frequency door system comprises: a radio frequency door having an electronic tag identification area; an antenna arranged on the radio frequency door and opposite to the electronic tag identification area; a refractive index gradient structure arranged on one side of the antenna close to the electronic tag identification area; the refractive index gradient structure has a first arc surface structure protruding towards the antenna on one side close to the antenna; 2. The radio frequency gate system of claim 1, wherein, the refractive index of the first arc surface structure gradually decreases in a direction away from the arc center; 3. The radio frequency gate system of claim 1, wherein, a left-handed material electromagnetic array covering the arc surface of the first arc surface structure. The left-handed material electromagnetic array covers the antenna in the orthogonal projection of the plane where the antenna is located.

4. The radio frequency gate system of claim 1, wherein, The left-handed material electromagnetic array is in contact with the antenna. Alternatively, the left-handed material electromagnetic array has a gap with the antenna.

5. The radio frequency gate system of claim 1, wherein, The left-handed material electromagnetic array is attached to the arc surface of the first arc surface structure. Alternatively, the radio frequency door system further comprises a supporting layer attached to the arc surface of the first arc surface structure, and the left-handed material electromagnetic array is arranged on the surface of the supporting layer close to the antenna. The left-handed material electromagnetic array comprises a plurality of left-handed material electromagnetic units arranged in an array.

6. The radio frequency gate system of claim 1, wherein, The left-handed material electromagnetic unit comprises a combination structure of an open resonant ring and a metal rod, a double-cross structure, a single-face double-S / U type unit, a dendritic fractal structure or a liquid crystal control unit. The array distribution comprises a rectangular array distribution, a circular array distribution or a sparse array distribution.

7. The radio frequency gate system of claim 6, wherein, The first arc surface structure comprises a plurality of dielectric layers arranged in sequence in a direction away from the arc center. In the direction away from the arc center, the dielectric constant of the plurality of dielectric layers decreases in sequence, the thickness of the plurality of dielectric layers decreases in sequence, and the refractive index of the plurality of dielectric layers decreases in sequence.

8. The radio frequency gate system of claim 7, wherein, The dielectric layer comprises a polyurethane foam layer. In the direction away from the arc center, the porosity of the plurality of polyurethane foam layers increases in sequence.

9. The radio frequency gate system according to any of claims 1-8, characterized in that, The polyurethane foam layer is formed by injecting water and isocyanate into a polyurethane prepolymer and then foaming. In the direction away from the arc center, the water injection amount required for forming the plurality of polyurethane foam layers decreases in sequence, the isocyanate index required for forming the plurality of polyurethane foam layers increases in sequence, and the foaming time required for forming the plurality of polyurethane foam layers decreases in sequence. The refractive index gradient structure has a second arc surface structure protruding towards the electronic tag identification area on one side close to the electronic tag identification area; 10. The radio frequency gate system of claim 9, wherein, The refractive index of the second arc surface structure gradually decreases in a direction away from the arc center. And / or, the refractive index of the second arc surface structure is between the minimum refractive index and the maximum refractive index of the first arc surface structure. The refractive index gradient structure comprises a spherical structure or an ellipsoidal structure; and / or The first arc surface structure and the second arc surface structure respectively comprise a hemispherical structure or a hemi-ellipsoidal structure.

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