RFID antenna

Abstract

An RFID antenna for a container having an electrically conductive container part is disclosed. The RFID antenna comprises an antenna body having a surface that constitutes at least a portion of the electrically conductive container part. The antenna body is shaped to define an antenna volume for receiving one or more RFID tagged articles, the antenna body forming a single turn solenoid. The RFID antenna further comprises at least one current feed point and at least one current return point. The current feed point and the current return point are electrically connected to the antenna body such that a current flowing through the antenna body generates a magnetic field in the antenna volume for reading the RFID tag.

Description

[Technical Field]

[0001] The present disclosure relates generally to RFID readers, antennas and antenna systems, and more particularly to RFID antennas for containers having conductive container components such as metal walls. [Background technology]

[0002] Vaccine refrigerators and freezers, especially in third world and developing countries, can rely on intermittent and unreliable electricity, so they need to be efficient and minimize temperature changes when accessing their contents.

[0003] One type of vaccine refrigerator 100 is based on a "chest" type design as shown in Figure 1. The vaccine refrigerator 100 is accessed through a top 102 that has a top-opening lid 104 for accessing the refrigerator's stored contents in various compartments 106 within the refrigerator. This design provides good insulation and minimizes loss of cold air when the lid 104 is opened. Summary of the Invention [Problem to be solved by the invention]

[0004] Radio-Frequency Identification (RFID) tracking of vaccines requires reading RFID tags inside the refrigerator. Typically, the walls 108 of the refrigerator 100 are lined with metal to efficiently conduct heat away from the vaccine. As a result, installing any type of RFID system is problematic because the metal walls 108 block, cancel, or reflect radio waves. Installing RFID antenna shelves in the refrigerator (e.g., inserting shelves with integrated antenna systems) is relatively expensive, reduces available storage volume, and requires complex electronics with high power demands.

[0005] There is a need for a simple, low-cost, and reliable RFID antenna system that can be used in chest-type refrigerators and freezers and that can read RFID tags on items within the refrigerator or freezer. [Means for solving the problem]

[0006] Any discussion of documents, acts, materials, devices, articles or the like contained in this specification should not be construed as an admission that any or all of such matters formed part of the prior art base existing prior to the priority date of each claim of this application or were general general knowledge in the art relevant to the present disclosure.

[0007] In one aspect, an RFID antenna for a container having an electrically conductive container part is provided, the RFID antenna comprising an antenna body having a surface that forms at least a portion of the electrically conductive container part.

[0008] The antenna body may be shaped to define an antenna volume for receiving one or more RFID-tagged items. The antenna body may be shaped to form a hollow prism. The hollow prism may be a hollow cubic prism, a hollow cylindrical prism, or a hollow polyhedral prism.

[0009] The antenna body may form a single-turn solenoid. The antenna body may be unshielded within the enclosure.

[0010] The RFID antenna may further include at least one current supply point and at least one current return point, where the current supply point and the current return point are electrically connected to the antenna body, and a current flowing through the antenna body generates a magnetic field within the antenna volume for reading RFID tags.

[0011] The antenna body may include an electrical break, wherein at least one current supply point supplies current to the antenna body on a first side of the electrical break and at least one current return point provides a current return path on an opposite second side of the electrical break. The electrical break may define a dielectric gap in the antenna body. The antenna body may have a first edge and a second edge, wherein the first edge overlaps the second edge such that the electrical break is formed in the overlap region.

[0012] The antenna body may further include a conductive container compartment partition member. The conductive container compartment partition member may include a partition plate separating two adjacent RFID antennas. The partition plate may be fixed to the conductive container part via a dielectric element to form a capacitive member of the RFID antenna.

[0013] Two adjacent RFID antennas each generate a magnetic field, each of which is oriented in an opposite direction, and the sum of the two magnetic fields may be less than +42 dBμA / m at a distance of 10 m from the container.

[0014] In another aspect, there is provided an RFID antenna system comprising a plurality of RFID antennas as described above and an antenna controller configured to sequentially activate two adjacent RFID antennas at a time.

[0015] In another aspect, a tripartite RFID label is provided for application to an article having at least three adjacent surfaces, each surface being on a different plane. The RFID label includes a flexible antenna substrate having three adjacent regions configured relative to one another, and an RFID antenna disposed in each of the three adjacent regions, each RFID antenna connected to an RFID chip. Each of the three adjacent regions is associated with one of the three adjacent surfaces when the RFID label is applied around the vertices of the three adjacent surfaces. When activated, each of the RFID antennas has a magnetic field perpendicular to its respective substrate region such that, in use when the RFID label is applied to the article, the magnetic field of each antenna is perpendicular to its respective article surface.

[0016] Each of the RFID antennas may have its own RFID chip, or each of the RFID antennas may be connected to one shared RFID chip. [Brief explanation of the drawings]

[0017] Next, embodiments of the present disclosure will be described by way of example with reference to the accompanying drawings.

[0018] [Figure 1] FIG. 1 is a diagram showing an example of a chest-type vaccine refrigerator.

[0019] [Figure 2A] 1 illustrates an embodiment of a container having an RFID antenna configured for use with the container.

[0020] [Figure 2B] FIG. 2B illustrates the RFID antenna of FIG. 2A.

[0021] [Figure 3] 1 is a schematic diagram of a cylindrical embodiment of an RFID antenna.

[0022] [Figure 4A]FIG. 1 is a schematic diagram of a cubic embodiment of an RFID antenna.

[0023] [Figure 4B] FIG. 4B is a plan view of the RFID antenna of FIG. 4A.

[0024] [Figure 4C] 1 is a schematic diagram of another cubic embodiment of an RFID antenna.

[0025] [Figure 5A] FIG. 1 is a perspective view of a metal refrigerator liner for a vaccine refrigerator.

[0026] [Figure 5B] FIG. 5B is a schematic diagram of a first embodiment of an RFID antenna system consisting of the metal refrigerator liner of FIG. 5A.

[0027] [Figure 6A] FIG. 5C is a perspective view of one embodiment of the RFID antenna system of FIG. 5B.

[0028] [Figure 6B] FIG. 5C is a perspective view of another embodiment of the RFID antenna system of FIG. 5B.

[0029] [Figure 7] 1 is a schematic diagram of an RFID antenna system having multiple RFID antennas.

[0030] [Figure 8A] FIG. 5B is a schematic diagram of a second embodiment of an RFID antenna system including the metal refrigerator liner of FIG. 5A.

[0031] [Figure 8B] 8B is an electrical circuit model of the RFID antenna embodiment of FIG. 8A.

[0032] [Figure 8C]8B is a simplified electrical circuit model of the RFID antenna embodiment of FIG. 8A.

[0033] [Figure 8D] 8B is a perspective view of an exemplary RFID antenna system according to the embodiment shown in FIG. 8A.

[0034] [Figure 9A] FIG. 10 illustrates an electrical circuit model for a multiple feed point embodiment.

[0035] [Figure 9B] 9B is a circuit model of a feed point balancing transformer according to the embodiment of FIG. 9A.

[0036] [Figure 10] 1 illustrates an embodiment of an RFID antenna having multiple feed points.

[0037] [Figure 11] 1 is a schematic diagram of an RFID reader for use with an RFID antenna.

[0038] [Figure 12A] FIG. 1 illustrates a plan view of a three-dimensional RFID tag for use with the RFID antennas described herein.

[0039] [Figure 12B] A diagram showing how the three-dimensional RFID tag of Figure 12A is applied to the corner of an item.

[0040] [Figure 12C] FIG. 1 illustrates a prior art RFID tag.

[0041] In the drawings, like reference numerals refer to like parts. DETAILED DESCRIPTION OF THE INVENTION

[0042] Antenna System

[0043] Figure 2A shows a container 202 (in this example, a refrigerator or freezer, such as might be used to store a vaccine). Container 202 has an electrically conductive container part 204. Figure 2B shows an RFID antenna 200 for container 202. RFID antenna 200 is comprised of an antenna body 206 having a continuous conductive surface 208 that forms at least a portion of electrically conductive container part 204.

[0044] In the refrigerator example, the conductive enclosure component 204 is a metal liner 210 of a refrigerator compartment 212. The metal liner 210 lines the side walls of the compartment 212 and, in this example, is in the shape of a rectangular cylinder with four metal walls and no floor or ceiling. In this example, the antenna body 206 is unshielded within the enclosure 202. In another embodiment, the enclosure is a cabinet with metal side walls and / or metal shelves. The metal walls and / or shelves of the cabinet are the conductive enclosure components that are incorporated into the RFID antenna system described herein.

[0045] Antenna body 206 is shaped to define an antenna volume 214 for receiving one or more RFID-tagged articles, for example, vaccine vials or boxes holding vaccine vials, to be placed in container 202 .

[0046] The antenna body 206 is shaped to form a hollow prism, such as the hollow cube prism 220 shown in Figures 2A and 2B. The hollow prism can have any hollow cross-sectional shape whose interior volume is used to hold an item. The hollow prism has one or more walls with surface areas. Thus, the hollow prism may be, for example, a hollow cylindrical prism 320 or a hollow polyhedral prism as shown in Figure 3 of the drawings.

[0047] 3, the antenna body forms a single-turn solenoid 322 with an air core. Current flowing on the metal surface 308 of the antenna body 306 forms a current sheet that generates electromagnetic waves that propagate radially inward and outward from the two surfaces of the sheet. The inwardly propagating waves set up standing waves inside the antenna volume 314, creating a uniformly distributed magnetic field H.

[0048] In an embodiment in which the antenna body 306 is in the form of a hollow cylindrical prism 320 as shown in Figure 3, the inductance L of the solenoid 322 is given by L = μA / l, where μ is 4π10 ー7 is the permeability of free space, which is equal to πr 2 where ℓ is the area of ​​the loop given by ℓ = 1 / 2 and ℓ is the length of the hollow cylindrical prism 320 (i.e., the longitudinal dimension perpendicular to the general direction of current flow).

[0049] Referring to FIG. 4A , an RFID antenna system 470 for monitoring multiple RFID tags within a container includes an RFID antenna 400. Some embodiments (as described elsewhere herein) can include multiple RFID antennas, each comprising an antenna body 406 formed by a conductive surface that constitutes at least a portion of the container's conductive components. The RFID antenna 400 includes an electrical gap 428 in the conductive surface, and at least one current feed point 430 and at least one current return point 432 on either side of the electrical gap 428. The antenna body 406 is shaped to form a one-turn solenoid that defines an antenna volume 414 for holding RFID-tagged items. The conductive surfaces are shaped and positioned in two of the three dimensions (there is no floor or ceiling at the bottom or top of the body), shown as sidewalls in FIG. 4A , to allow the internal magnetic field to pass from the inside to the outside of the antenna body 406 and form a magnetic return path. Furthermore, conductive floors or ceilings at the ends or walls of the tube should be avoided because they short-circuit the current sheet.

[0050] For the hollow (rectangular) cube 420 forming the antenna body 406 of the antenna 400, the area A is the width W multiplied by the depth D, as shown in Figure 5A. The inductance of the rectangular solenoid 422 is given by L = μDW / l.

[0051] The internal magnetic field H is aligned along the axis of the solenoid 422 in the direction l (the longitudinal dimension perpendicular to the general direction of current flow) and is given by Ampere's law: H=l / l, where l is the total current flowing in the solenoid sheet.

[0052] In the example refrigerator embodiment, the inductance and magnetic field calculations for the vaccine refrigerator liner are very accurate because there are no metal structures above or below the liner. Typical magnetic fields required to activate RFID tags range from 0.5 A / m to 1.0 A / m, depending on the size of the tag. A field strength of 2 A / m is sufficient for RFID interrogation of poorly oriented tags.

[0053] The dimensions, inductance, and field strength of the two models of vaccine refrigerators are shown in Table 1. [Table 1] Table 1: Mechanical and electrical parameters of refrigerator liners

[0054] An RFID antenna is a conductive structure with terminals that connect to an RFID reader. The RFID reader controls the operation of the RFID antenna (e.g., via an antenna controller) and receives information about RFID tags from the RFID antenna. The RFID reader provides a signal source to the RFID antenna and activates the RFID antenna to interrogate RFID tags.

[0055] 4A, the example mini-refrigerator includes a metal liner 410 with a substantially square cross section. The terminals of the RFID antenna 400 are a current supply point 430 and a current return point 432. The current supply point 430 and the current return point 432 are electrically connected to the antenna body 406, and the current flowing through the antenna body 406 generates a magnetic field H within the antenna volume 414 for reading RFID tags.

[0056] The antenna body 406 has an electrical break 434. A current feed point 430 supplies current to the antenna body 406 at a first side 436 of the electrical break 434, and a current return point 432 provides a current return path at an opposite second side 438 of the electrical break 434. The electrical break is formed by a longitudinal gap 428 within the antenna body, with air or another dielectric separating the two sides 436, 438 so that current can be applied to the antenna 400. The gap 428 can be small (e.g., 1 mm or less) as long as there is no electrical connection that would short out a signal source applied across the gap. The gap can be large (e.g., 5-20 mm), but if the gap is too large (e.g., a separation between the first side 436 and the opposite second side 438 of the electrical break 434 greater than 20 mm), the magnetic field H within the antenna volume 414 may be compromised because the magnetic field H may leak through the gap.

[0057] Figure 4B is a top view of the embodiment shown in Figure 4A. As can be seen, electrical disconnection 434 is in the form of a longitudinal gap 428. The smaller the gap 428, the less magnetic field leakage there will be.

[0058] As shown in the cross-sectional view of FIG. 4C, shaping the longitudinal gap 428 so that there is overlap between the two sides 436 and 438 can eliminate leakage through the electrical break 434. With sufficient overlap, the magnetic field is forced to run parallel to the liner surface and cannot pass through the gap 428. An overlap width of 5 to 20 times (e.g., about 10 times) the gap width provides adequate containment of the magnetic field lines. For example, if the first side 436 overlaps the second side 438 by 10 mm and there is a 1 mm gap 450 between the first side 436 and the second side 438, there is little or substantially no magnetic field leakage through the gap. A method for implementing overlap that prevents magnetic field leakage is described in International Patent Application WO 2016 / 038897, the contents of which are incorporated herein by reference.

[0059] In the example refrigerator embodiment, a simple way to create a current sheet is to conform the refrigerator's liner walls, for example, by cutting liner 410 and injecting a current into the liner at the cut point (shown in FIG. 4A in the center of one side wall, but which could be the corner between two walls, or anywhere around the circumference of the cylinder as shown in FIG. 3). A tuning capacitance or capacitor 440 may be connected in series with signal source 442 to adjust the inductance of the liner loop.

[0060] Multiple Compartments

[0061] In larger containers, there may be multiple areas, regions, or compartments within the container where RFID-tagged items are held and RFID antennas are implemented to read the RFID tags. Figure 5A shows a rectangular metal liner 510 used in large refrigerators. The large rectangular shape lends itself to injection across the center 546 of the liner 510, forming a figure-eight antenna 500 with two counter-rotating current loops 544.

[0062] The injected current I is divided between the two halves of the liner, forming two counter-rotating current loops 544 as shown. A tuning capacitor or capacitors 540 may be added in series with the signal source 542 to cancel the inductance of the liner.

[0063] 6A and 6B, a large refrigerator having a rectangular metal liner 610 uses centerline injection to generate the counter-circulating currents of FIG. 8 in two adjacent antennas within the liner 610. The interior metal liner 610, which forms part of the refrigerator, is adapted to include a conductive container compartment divider member. The conductive container compartment divider member may include a divider member separating two adjacent RFID antennas, for example, in the form of a conductive partition wall (also referred to as a "center divider" or "divider"), such as a metal plate 650, which bisects the liner cavity to form two equal cavities forming the antenna volume 614. Current source and return points 630 and 632 for the radio frequency (RF) signal are located on either side of a longitudinal gap 628 in the metal plate 650. The gap 628 may be located in the center of the metal plate 650 or offset to either end of the plate if convenient. The current supply point 630 and current return point 632 are located on a shared portion of adjacent antenna bodies such that a single current injection means is shared by adjacent RFID antennas. The injected current is split into two substantially equal portions, forming two counter-rotating current loops.

[0064] 6B, the connection between the metal plate 650 and the liner 610 can be made by a direct galvanic connection 652. The direct galvanic connection can be made using metal-to-metal contact via, for example, mounting screws, rivets, solder, or the like.

[0065] The idea of ​​using a metal divider to supply current to the conductive liner wall can be extended beyond two half dividers to multiple dividers. Instead of a single divider, a multi-compartment embodiment with multiple dividers creates multiple equal or similarly sized compartments.

[0066] 7, each metal plate 750 has a signal source 742 that can be either a source that injects a current I or a voltage source set to zero volts (which in this exemplary embodiment is a center-driven signal source). A zero volt signal source 746 acts as a short circuit that shorts both sides of the metal plate 750 on either side of the electrical gap 728.

[0067] The sources 742 are switched individually (and in some embodiments sequentially and / or sequentially) so that one source at a time is activated as the active source 754 and scans the contents of its two adjacent compartments 712. By activating a series of sources 742, one at a time, the RFID system scans through all compartments 712 of the multi-compartment container. The antenna controller is configured to sequentially activate two adjacent RFID antennas at a time.

[0068] By setting only one source active and all other sources to zero volts, the two compartments 712 adjacent to the active source 754 behave like the two-compartment embodiment described elsewhere herein, with all other compartments then acting as shorted loops and a net magnetic field of zero. In this way, large, multi-compartment metallic structures can be RFID-enabled in a low-cost, one-dimensional system.

[0069] 7 shows an embodiment with four compartments with three dividing walls and three sources. In an alternative four-compartment embodiment, the center wall has no source and allows for the reading of RFID tags in compartments 1 and 2 when a first source (on wall number 1) is activated, and allows for the reading of RFID tags in compartments 3 and 4 when a second source (on wall number 3) is activated.

[0070] The signal source and its impedance can be controlled using the principles described in International Patent Application WO2010 / 025516, the contents of which are incorporated herein by reference. s This can be achieved by controlling the signal source impedance to ensure a low short circuit impedance when .

[0071] The RFID antenna system 770 comprises a conductive body 706 having one or more side walls defining a container volume, and one or more conductive partition walls 750 dividing the container volume into compartments 712. Each partition wall 750 comprises an electrical gap 728 having a current supply point 730 and a current return point 732 on either side. The current supply point 730 comprises one or more current supply points, and the current return point 732 comprises two or more current return points. The conductive body 706 comprises at least a portion of the metal liner 710 of the container. Each conductive partition wall 750 comprises two wall portions on either side of the electrical gap 728. Each conductive partition wall 750 is affixed to the conductive body 706. In some embodiments, the conductive partition walls are affixed to the conductive body via a capacitive plate and a dielectric spacer disposed between the capacitive plate and the conductive body, as described elsewhere herein.

[0072] The RFID antenna system 770 includes a signal source for each partition wall. These signal sources are provided by an RFID reader and may consist of one or more RFID reader antenna signal sources.

[0073] In some embodiments, the RFID antenna system 770 includes an antenna controller configured to activate one signal source at a time so that current flows through a portion of the conductive body and a partition wall that surrounds and forms a compartment that shares the activated signal sources. In other embodiments, the antenna controller is separate and / or external to the RFID antenna system 770.

[0074] Capacitive Connection

[0075] A direct galvanic connection between the liner and the divider plate may not be possible. For example, the liner wall may not be conductive due to corrosion-resistant treatments such as anodizing, or the use of mechanical fasteners may not be permitted. In such cases, the divider member can be affixed to a conductive container member via a dielectric element to form the capacitive component of the RFID antenna. A capacitive connection between the metal divider plate and the liner can be used as shown in Figures 8A-8D.

[0076] 8A shows a circuit model of an antenna system 870 having two antennas 800 and incorporating capacitive plates 872. Each plate 872 has a width b and a height l (which is the longitudinal dimension of the antenna body 806 perpendicular to the general direction of current flow). A dielectric spacer 874 is used. The spacer 874 may be an insulating layer formed by anodization, or it may be a spacer (e.g., a plastic spacer) of a predefined thickness t selected to provide a specific capacitance between the plate 872 and the liner 810.

[0077] Plate capacitance C p is C p =ε0ε r bl / t, where ε0 is the permittivity of free space, ε ris the relative dielectric constant, typically 2.2 for non-polar plastics. Because of its small thickness, the dielectric spacer 874 has a relatively large capacitance and acts as an RF short circuit. In this case, a separate series tuning capacitance may be used to adjust the inductance of the liner loop. Alternatively, the correct tuning capacitance can be provided by selecting the spacer thickness and the size of the capacitive plate.

[0078] Table 2 shows the capacitance of a metal plate with a 50 μm adhesive layer or a 1 mm plastic spacer. In the adhesive layer case, the capacitance is large enough to act as an acceptable RF short circuit, but in the 1 mm spacer case, the capacitance acts as part of the tuning capacitance. [Table 2] Table 2: Capacitance of metal plates with different dielectric thicknesses

[0079] Figure 8A is a plan view of a two-compartment antenna system with a capacitive plate 872 coupling a central metal section 850 to the liner wall. Figure 8B shows an electrical circuit model 876 of this arrangement, and Figure 8C shows a simplified electrical circuit model 878. Capacitance C is the plate capacitance, and inductance L is the inductance of liner 850, as shown in Table 1.

[0080] A current source point 830 and a current return point 832 are on either side of a signal source 842 .

[0081] Table 3 shows example circuit model parameters that show that a plate width of 108 mm with 1 mm plastic spacers on either end of the voltage divider plate provides adequate tuning capacitance for the voltage divider circuit. [Table 3] Table 3: Parameter values ​​for the voltage divider plate circuit

[0082] Figure 8D is a perspective view of an exemplary RFID antenna system 870 according to the embodiment shown in Figure 8A. A metal divider 850 has longitudinal flanges 871 on either side, which are shaped to form capacitive plates 872. In this exemplary embodiment, the divider 850 is affixed to the liner 810 via a layer of adhesive, such as a spray contact adhesive like Selleys Kwik Grip Spray Contact Adhesive, applied between the flanges and the central regions of the opposing sidewalls of the liner 810.

[0083] Electromagnetic Compatibility (EMC) Compliance

[0084] There are two types of electromagnetic radiation: near-field radiation, where the distance between the source and receiver is less than the wavelength of the emitted radiation divided by 2π, and far-field radiation, where the distance between the source and receiver is greater than the wavelength of the emitted radiation divided by 2π.

[0085] The current loop formed by the liner is radiated in the far field. The far field radiation depends on the area of ​​the liner loop and the current in the loop. There is a maximum allowed far field strength for EMC compliance, for example in Australia the maximum far field radiation measured at a distance of 10m is +42dBμA / m (126μA / m). The formula for calculating the far field strength is H=IπDW / rλ 2 where λ is the wavelength of the RFID frequency. The RFID frequency for high frequency (HF) systems is 13.56 MHz, with a wavelength of 22.124 m. Table 4 shows the far-field radiation intensity for two models of vaccine refrigerators. [Table 4] Table 4: EMC far-field radiation values

[0086] The compact model meets EMC compliance targets while maintaining an internal electric field sufficient to interrogate RFID tags (i.e., a field strength of approximately 0.5 A / m to 2 A / m, as described elsewhere in this document with reference to Table 1).

[0087] Larger models do not meet EMC compliance targets and require modification to meet EMC compliance while maintaining a sufficient internal electric field to match RFID tags.

[0088] Referring again to FIG. 5B, a large rectangular liner 510 is divided into two adjacent antenna volumes 514, with two counter-rotating current loops 544 generating two equal or substantially similar magnetic fields that cancel each other out in the far field.

[0089] The far-field radiation is the sum of the radiation from the individual counter-rotating currents. The centers of magnetic moment of each current loop are separated by half the total width (W / 2) of the antenna body 506. The far-field electric field decreases as the fields subtract from each other. The formula for calculating the far-field strength of a pair of counter-rotating currents is given below: H=IπDW((rW / 4) -1 -(r+W / 4) -1 )) / 2λ 2 .

[0090] Table 5 shows the far-field radiation intensity of the large vaccine refrigerator antenna 500 with a central current source 542. In this example embodiment, the feed current is doubled to maintain the same current in the current sheet circulating within the liner. [Table 5] Table 5: Long-distance radiation due to central current injection

[0091] Two adjacent RFID antennas each generate a magnetic field that is in opposite directions such that the sum of the two fields is less than +42 dBμA / m at a distance of 10 m from the container. In this example, the sum of the two fields is less than +19 dBμA / m. Thus, by injecting concentrated current through the splitter element 550, the far-field radiation can meet the EMC compliance target.

[0092] The RFID antenna 500 is for use with a container, such as a refrigerator, and includes an antenna body 506 defining at least first and second antenna volumes 514. Two opposing sides of each antenna volume are unshielded. The first antenna volume is defined by at least a first conductive component configured to generate a first magnetic field within the first antenna volume. The first magnetic field is oriented in a first direction. The second antenna volume is defined by at least a second conductive component configured to generate a second magnetic field within the second antenna volume. The second magnetic field is oriented in a second direction. The sum of the first and second magnetic fields is less than +42 dBμA / m at a distance of 10 m from the container. In some embodiments, the sum is substantially zero outside the container. In some embodiments, the first and second conductive components may be first and second portions of the same conductive body, such as first and second halves of a metal liner of a refrigerator (or first and second shelves of a cabinet with metal shelving).

[0093] current injection

[0094] The accuracy of the circuit model mentioned here requires uniformity of the current sheet through the RFID antenna body. Injecting current at a single central point can cause current "crowding" and result in a non-uniform electric field distribution.

[0095] A more uniform current distribution can be achieved by injecting current at multiple points across the divider using a current balancing circuit 980. This arrangement is shown in Figure 9A by power splitter 982. One method for implementing multiple current injection points is described in WO2016 / 121130, the contents of which are incorporated herein by reference.

[0096] In the illustrated embodiment, each terminal (Feed 0, Feed 1, Feed 2, and Feed 3) is fed from a transformer 984 (as shown in FIG. 9B) to provide a balanced differential current on each side of the divider. Driving points x and y, which are current source points 930 and current return points 932, correspond to current source points 830 and current return points 832 shown in FIG. 8A.

[0097] Transformer 984 can also be used for impedance transformation to adjust driving point impedance and / or current magnitude.

[0098] FIG. 10 illustrates an exemplary embodiment of an RFID antenna 1000, adapted for use within a container. The RFID antenna 1000 has an antenna body formed by a conductive surface 1008 having a first edge 1036 and an opposite second edge 1038. The conductive surface 1008 is positioned such that the first edge 1036 is substantially adjacent to the second edge 1038. The antenna body 1006 is shaped to define a volume 1014 for receiving one or more RFID-tagged items. The second edge 1038 is separated from the first edge 1036 by an electrical gap 1028. The RFID antenna 1000 has two or more current feed points 1030 at the first edge 1036 for feeding current to the antenna body 1006 and two or more current return points 1032 at the second edge 1038 for providing a return current path from the antenna body 1006. The conductive surface 1008 constitutes at least a portion of a conductive area of ​​a container, for example, an inner metal liner 1010 of a refrigerator.

[0099] In some embodiments, the locations of the current source points are aligned with the locations of the current return points so that the current source points and current return points are substantially adjacent. This is shown, for example, in FIG. 4A. In other embodiments, the locations of the current current return points are offset from the locations of the current source points so that the line connecting the current source point and its nearest current return point is not the shortest distance from the first edge 1036 to the second edge 1038. This is shown in FIG. 10 and may be done for mechanical or structural convenience.

[0100] RFID Surveillance System

[0101] In some embodiments, the RFID antenna described herein is provided as a separate device for incorporation into the container or is already incorporated into the container and incorporates a conductive component of the container. For example, a refrigerator (such as a chest-style vaccine refrigerator) may have an inner metal liner adapted to function as an RFID antenna by having terminals located on either side of an electrical break in the liner or an electrical break in a divider wall disposed within the liner. In such embodiments, the container is adapted so that the antenna terminals can interface with a separate external RFID reader via an RF cable, such as a coaxial cable, connecting between the RFID antenna and the reader's antenna interface.

[0102] In some embodiments, an RFID antenna system includes one or more RFID antennas as described herein, as well as an antenna controller. The antenna controller controls the operation of the RFID antennas. For example, the antenna controller may be configured to sequentially activate two adjacent RFID antennas at a time, as described elsewhere herein.

[0103] In some embodiments, an RFID reader is provided in, next to, connected to, or in some other manner associated with the container, and the RFID reader is electrically connected to an RFID antenna via an antenna terminal.

[0104] In these embodiments, an RFID monitoring system (for monitoring multiple RFID tags in a container, such as a refrigerator) includes an RFID reader and at least one antenna for transmitting and receiving RF signals for communicating with the RFID tags. The at least one antenna is in communication with the RFID reader. As described herein, the at least one antenna configures at least a portion of a conductive periphery of the container. The portion of the conductive periphery has a first edge and an opposing second edge. The portion of the conductive periphery is formed such that the first edge is substantially adjacent to the second edge and spaced apart from the second edge. The first edge is spaced apart from the second edge, forming an electrical gap between the first edge and the second edge. The electrical gap may include a dielectric.

[0105] FIG. 11 is a schematic diagram of an RFID reader 1100 for use with the antennas described herein. The RFID reader 1100 includes a processor 1190, an antenna controller 1192, a data interface 1194, an antenna interface 1196, and a signal source 1198. The processor 1190 is configured to cause the antenna controller to control the operation of the RFID antenna, e.g., provide power and activate one or more RFID antennas. The processor 1190 is configured to receive RFID tag information from the RFID antenna via the antenna interface 1196. The processor 1190 is configured to process the received RFID tag information and transmit the processed RFID tag information via the data interface 1194. The processor may be in the form of a microcontroller, such as, for example, an Atmel AT91RM9200-CI®. The antenna controller 1192 may be implemented as part of the processor 1190 and / or via the same microcontroller. Alternatively, the antenna controller may be implemented using a programmable gate array. The antenna interface 1196 provides an electrical connection to the RFID antenna with an RF cable connecting to the RFID antenna, and also provides a signal source to a signal feed point and a signal return point using an RF switch such as a PIN diode or RF relay to direct the signal from the signal source as directed by the antenna controller 1192 under the control of the processor 1190.

[0106] In one embodiment, the RFID reader can be mounted within the compressor and controller compartment of the refrigerator. In another embodiment, the reader is connected to an antenna by a coaxial cable. The refrigerator has an interface for controlling the reader and triggering tag reading, such as a user interface (e.g., buttons and / or a screen) or a data interface configured to receive read commands. In some embodiments, the refrigerator includes a GSM and / or GPS module and may be configured to transmit data such as the refrigerator's location, temperature, and RFID tag information to a server daily or several times a day. In some embodiments, the RFID tag information is associated with the tagged item by the processor 1190 of the RFID reader 1100. In other embodiments, the RFID tag information is associated with the tagged item by a server that receives the information from the refrigerator.

[0107] 3D RFID tag

[0108] Described herein is an RFID antenna comprising an antenna body having a surface that forms at least a portion of a container component, such as a metal liner of a container. The container component may be, or may include, a metal liner of a container. The antenna body has antenna terminals configured to provide at least one current supply point and at least one current return point to the antenna body. The surface of the antenna body is shaped to define at least one volume for holding one or more RFID-tagged articles.

[0109] The internal magnetic field H within the volume of the antenna body is a one-dimensional field aligned along the axis of the solenoid. Therefore, RFID-tagged items are required to function in a one-dimensional magnetic field. This means that it is desirable for the tagged items to be properly positioned (e.g., stacked in a box or carrier in a defined, fixed orientation) so that the tag properly couples to the magnetic field.

[0110] The embodiments described herein relate to the use of passive RFID tags, however the techniques described herein are equally applicable to active RFID tags.

[0111] In some embodiments, when the placement of tagged items cannot be guaranteed, one solution is to use multiple RFID tags, each with a different orientation. For example, an RFID tag can be placed on the bottle lid and another RFID tag on the sidewall of the bottle, thereby containing RFID tags in at least two axes. This increases the probability of detection by the one-dimensional magnetic field inside the body of the RFID antenna.

[0112] In the example of a vaccine refrigerator storing vaccine vials, the vials can be placed inside a box and an RFID tag placed on the box. In one embodiment, three RFID tags are placed on the box to place tags on the X, Y, and Z planes of the box. Advantageously, the extra cost of tagging the box is only two additional tags. In contrast, tagging each vial would require significantly more tags, and if the vials are not placed in the box with the correct orientation, it is likely that all tags will not be read within a single dimension of the magnetic field. Tagging the box allows verification that the box of vials is in the refrigerator.

[0113] In other embodiments, RFID labels configured to operate in three dimensions can be affixed to items located within the RFID antenna volume. A first embodiment of such a tripartite RFID label 1200 is shown in Figure 12A of the drawings. The tripartite RFID label 1200 is adapted to be affixed to an article 1202 having at least three adjacent surfaces 1204. Each surface is in a different plane (e.g., aligned with the X, Y, and Z axes when the surfaces are perpendicular to one another, as in the case of a typical square or rectangular box). The RFID label has a flexible antenna substrate 1206 with three adjacent regions 1208, 1210, 1212 configured relative to one another such that, when affixed around a vertex 1214 of the three adjacent surfaces 1204 in the three planes, each of the three adjacent regions is associated with one of the three adjacent surfaces 1204. The flexible antenna substrate 1206 may be any suitable dielectric or non-conductive material that is flexible and suitable for application to an article, such as a flexible plastic. In the illustrated embodiment, the RFID label includes a lower adhesive surface 1216 for adhering the label to an article.

[0114] The tripartite RFID label 1200 has RFID antennas 1218, 1220, 1222 located in three adjacent regions 1208, 1210, 1212, respectively, each connected to an RFID chip 1228, 1230, 1232.

[0115] The shape and configuration of the tripartite RFID label 1200 is such that each RFID antenna 1218, 1220, 1222, when activated, has a magnetic field perpendicular to a respective one of the substrate regions 1208, 1210, 1212, such that when RFID label 1200 is affixed to item 1202 in use, the magnetic field of each antenna is perpendicular to the surface of its respective item. In this way, if (for example) a conventional holder, i.e., a box with orthogonal sides, were to have label 1200 affixed around one of its corners, each antenna would be located in a different one of three orthogonal planes. As a result, regardless of the orientation in which the holder is placed within a container described herein (e.g., a refrigerator or freezer such as those used to store vaccines), there will be at least one antenna oriented such that it is sufficiently aligned with the magnetic field generated by the container's RFID antenna for that antenna to operate.

[0116] 12A, each RFID antenna 1218, 1220, 1222 has its own respective RFID chip 1228, 1230, 1232. When the RFID label is manufactured or initialized, the three RFID chips 1228, 1230, 1232 are associated with each other so that when a label read by an RFID reader picks up any of the chips, the read is associated with the single shared RFID label 1200.

[0117] Placing three antennas on the same L-shaped label provides a simple and reliable RFID label, allowing three separate RFID tags to be easily applied via the same shared RFID label and substrate.

[0118] 12B shows an alternative embodiment of a tripartite RFID label 1240. In this embodiment, each RFID antenna 1218, 1220, 1222 is connected to a single shared RFID chip 1242, for example, via a pair of antenna leads 1248, 1252. In this embodiment, a single chip is associated with all three antennas, reducing the complexity of managing the information associated with the RFID label 1240.

[0119] Figure 12C shows a prior art embodiment of a label shaped to be applied around the corner of a box. However, because the label 6 contains a single antenna 8, with the antenna conductor looping around the edge of the label on all three sides 3, 4, and 5 of the box, this configuration does not work because there is a field direction where the net magnetic field in the coil is zero. The arrangement of Figure 12C is no different from a simple coil and is not suitable for 3D operation.

[0120] Described herein is a simple, reliable, and cost-effective method for mounting RFID antennas in containers such as metal-walled cabinets and chest refrigerators without the RFID antenna being adversely affected by the interior metal walls of the cabinet walls or refrigerator liner.

[0121] Advantageously, in the chest refrigerator embodiment, the metal liner of the refrigerator is used as part of the RFID antenna, allowing the RFID antenna to be designed without modifying the refrigerator design.

[0122] The interior metal liner that forms the refrigeration cavity of a chest-style refrigerator provides a thermally conductive layer for removing heat from the interior cavity to a cooling system mounted behind and on the outside of the metal liner wall. The antenna system described herein uses the interior metal liner of the refrigerator / freezer as part of an excitation loop (i.e., antenna coil) to generate a magnetic field for reading RFID tags associated with items stored in the refrigerator / freezer.

[0123] The liner is made of aluminum sheet and provides radio wave shielding. In multi-compartment refrigerators, the liner forms a large, electrically short, rectangular metal tube. Small bucket refrigerators have a similar liner design, where the liner is a smaller, square or rectangular tube. The RFID antenna system described here takes advantage of the liner's metallic conductivity to conduct the RFID signals used to read RFID-tagged items within the refrigerator, rather than being hindered by the liner's electrical properties.

[0124] Advantageously, the solution described herein works across the full range of vaccine refrigerator sizes, from the smallest bucket-sized units to large chest refrigerators and freezers.

[0125] It will be apparent to those skilled in the art that many modifications may be made without departing from the spirit and scope of the invention.

[0126] In the claims and the foregoing description, unless otherwise required by context, express language, or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in the inclusive sense, i.e., to identify the presence of stated features, but are not used to exclude the presence or addition of further features in various embodiments of the invention.

Claims

1. 1. An RFID antenna for a container having a conductive container part, comprising: an antenna body having a surface that forms at least a portion of the conductive enclosure part; An RFID antenna, wherein the antenna body is shaped to define an antenna volume for receiving one or more RFID tagged items.

2. 2. The RFID antenna according to claim 1, wherein the antenna body is shaped to form a hollow polyhedron.

3. 3. The RFID antenna according to claim 2, wherein the hollow polyhedron is either a hollow cube or a hollow cylinder.

4. 4. The RFID antenna according to claim 1, wherein the antenna body forms a single-rotation solenoid.

5. 5. The RFID antenna according to claim 1, wherein the antenna body is not shielded within a container.

6. further comprising at least one current supply point and at least one current return point; the current supply point and the current return point are electrically connected to the antenna body; 6. The RFID antenna according to claim 1, wherein a current flowing through the antenna body generates a magnetic field within the antenna volume for reading an RFID tag.

7. The antenna body includes an electrical disconnect; the at least one current feed point supplies current to the antenna body on a first side of the electrical break; 7. The RFID antenna of claim 6, wherein the at least one current return point provides a current return path on a second, opposite side of the electrical break.

8. The RFID antenna of claim 7 , wherein the electrical break defines a dielectric gap in the antenna body.

9. the antenna body has a first edge and a second edge; 9. The RFID antenna of claim 7, wherein the first edge overlaps the second edge such that the electrical disconnection is formed in the overlapping area.

10. 10. The RFID antenna of claim 1, wherein the antenna body further comprises a conductive container compartment divider member.

11. The RFID antenna according to claim 10 , wherein the conductive container compartment partition member comprises a partition plate separating two adjacent RFID antennas.

12. 12. The RFID antenna of claim 11, wherein the partition plate is secured to the conductive enclosure part via a dielectric element to form a capacitive member of the RFID antenna.

13. Each of the two adjacent RFID antennas generates a magnetic field; Each magnetic field is oriented in the opposite direction, 13. An RFID antenna according to claim 11 or 12, characterized in that the sum of the two magnetic fields is less than +42 dBμA / m at a distance of 10 m from the container.

14. 1. An RFID antenna system comprising: a plurality of RFID antennas according to any one of claims 1 to 13; an antenna controller configured to sequentially activate two adjacent RFID antennas at a time; An RFID antenna system comprising:

15. 1. A tripartite RFID label having at least three adjacent surfaces for application to an article, each surface being on a different plane, comprising: a flexible antenna substrate having three adjacent regions configured relative to one another; an RFID antenna disposed in each of the three adjacent regions, each RFID antenna connected to an RFID chip; Equipped with each of the three adjacent regions being associated with one of the three adjacent surfaces when pasted around the vertices of the three adjacent surfaces; each of the RFID antennas, when activated, has a magnetic field perpendicular to its respective substrate area such that, in use when the RFID label is affixed to an article, the magnetic field of each antenna is perpendicular to the surface of the respective article; An RFID label, wherein each of said RFID antennas has its own RFID chip.

16. A tripartite RFID label for application to an article having at least three adjacent surfaces, each surface being on a different plane, comprising: a flexible antenna substrate having three adjacent regions configured relative to one another; an RFID antenna disposed in each of the three adjacent regions, each RFID antenna connected to an RFID chip; Equipped with each of the three adjacent regions being associated with one of the three adjacent surfaces when pasted around the vertices of the three adjacent surfaces; each of the RFID antennas, when activated, has a magnetic field perpendicular to its respective substrate area such that, in use when the RFID label is affixed to an article, the magnetic field of each antenna is perpendicular to the surface of the respective article; An RFID label, wherein each of said RFID antennas is connected to one shared RFID chip.

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