Adaptable ultra-high frequency RFID tag

Abstract

A radio-frequency identification (RFID) tag may include an antenna structure wrapped around a substrate. The antenna structure may include an inlay with a top surface and a bottom surface, and conductive patches laterally spaced apart on the top surface of the inlay with a gap between the conductive patches. The antenna structure may further include ground plates respectively connected to the conductive patches on the top surface of the inlay by metal strips. The antenna structure may be wrapped around the substrate so a portion of the inlay including the first and second conductive patches covers at least a portion of the top surface of the substrate. The portions of inlay including the metal strips are arranged along side surfaces of the substrate, and the portion of the inlay including the ground plates wrap around a bottom surface of the substrate so that one ground plate overlaps the other.

Description

ADAPTABLE ULTRA-HIGH FREQUENCY RFID TAGPRIORITY APPLICATION

[0001] This application claims priority to U. S. Provisional Patent Application Serial Number 63 / 580,750, filed on September 6, 2023, the disclosure of which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to Radio Frequency Identification (RFID) tags. Specifically, the present disclosure relates to an RFID tag with an antenna structure wrapped around a substrate.BACKGROUND

[0003] RFID tags are a type of tracking system to identify or track items. RFID tags are generally made of an RFID chip (e.g., an integrated circuit), an antenna, and a substrate. The antenna (also called a Tag Antenna) is connected to the RFID chip and receives signals from an RFID reader (also called an Interrogator Antenna). Depending on the type of the tag, the tag antenna either transmits or reflects the signal received from the RFID reader. The substrate is a material on which the RFID chip and the tag antenna are mounted. Substrate materials can include paper, polyester, polyethylene, and polycarbonate, for example. RFID tags can be active, passive, or semi-passive. Active tags have a power-source such as a battery on or connected to the tag while passive tags obtain power from radio energy radiated by the interrogator antenna. Semi-passive tags obtain power from the energy radiated by the interrogator antenna and include a battery to extend the communication range.SUMMARY

[0004] A radio-frequency identification (RFID) tag may include a substrate with a top surface, a bottom surface, a first side surface, and a second side surface. The RFID tag may further include an antenna structure wrapped around at least a portion of the substrate. The antenna structure may include an inlay having a top surface and a bottom surface. The antenna structure may further include a first conductive patch (e.g., a metal plate) and a second conductive patch (e.g., a second metal plate) located on a top surface of the inlay. Thefirst and second conductive patches may be laterally spaced apart from each other to form a gap therebetween. For example, a first edge of the first conductive patch may be laterally spaced apart from a first edge of the second conductive patch.

[0005] The antenna structure may also include first and second ground plates. The first ground plate may be located on the top surface of the inlay laterally spaced apart from a second edge of the first conductive patch and connected to the first conductive patch by a first metal strip. The second ground plate may be located on the top surface of the inlay and laterally spaced apart from a second edge of the second conductive patch. The second ground plate may be connected to the second conductive patch by a second metal strip

[0006] The antenna structure may be wrapped around the substrate such that a portion of the inlay including the first and second conductive patches covers at least a portion of the top surface of the substrate. A portion of the inlay including at least a portion of the first metal strip may be arranged along the first side surface of the substrate. A portion of the inlay including at least a portion of the second metal strip may be arranged along the second side surface of the substrate. The portions of the inlay containing the ground plates may be wrapped around the bottom surface of the substrate such that the one ground plate (e.g., the first ground plate) overlaps the other ground plate (e.g., the second ground plate) on the bottom surface of the substrate.

[0007] A method of fabricating the RFID tag may include providing the substrate, forming the antenna structure, and wrapping the antenna structure around the substrate as described above.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0009] FIG. 1A illustrates an example of an antenna structure for a radio-frequency identification (RFID) tag.

[0010] FIG. IB illustrates a view from above a top side of an RFID tag with the antenna structure of FIG. 1 A wrapped around a rectangular substrate.

[0011] FIG. 1C illustrates a view from above the bottom side of the RFID tag of FIG. IB.

[0012] FIGS ID and IE illustrate alternate embodiments of wrapping the antenna structure around the rectangular substrate.

[0013] FIG. IF illustrates an alternate view from above the bottom side of the RFID tag of FIG. IB showing partial overlap between the ground plates.

[0014] FIG. 1G illustrates an alternate view from above the bottom side of the RFID tag of FIG. IB showing a gap between the ground plates.

[0015] FIGS. 1H and II illustrate alternate views of the antenna structure shown in FIGS. 1A and IB showing wider connecting strips connecting the conducting patches to the ground plates.

[0016] FIG. 2A illustrates a view from above a top side of a radio-frequency identification (RFID) tag with an antenna structure wrapped around a rectangular substrate.

[0017] FIG. 2B illustrates a view from above the bottom side of the RFID tag of FIG. 2A.

[0018] FIG. 3A illustrates an example of a cylindrical radio-frequency identification (RFID) tag.

[0019] FIGS. 3B-3F illustrate an assembly process for the cylindrical RFID tag of FIG. 3 A.

[0020] FIG. 4A illustrates an example of an asymmetrical RFID tag including antitampering features.

[0021] FIG. 4B illustrates an example of the asymmetrical RFID tag of FIG. 4A including a dielectric core.

[0022] FIG. 5 illustrates an example of a method of fabricating a radio-frequency identification (RFID) tag.DETAILED DESCRIPTION

[0023] RFID tags are used, for example, to track items. RFID tags can be active (including or connected to a power source such as a battery) or passive (which operate without a power source). Passive RFID tags can be especially useful for global supply chain management, access control, file tracking, or the like. One disadvantage of passive RFIDs is that they can use uneconomical dielectric materials as a substrate, such as FR4 laminate, which require the use of a large tag antenna and utilize a complex structure using discrete radio-frequency (RF) components (such as capacitors) to achieve better antenna matching. The uneconomical dielectric material and large tag antenna size result in an RFID tag that is large, heavy, and expensive. Therefore, there exists a need for an RFID tag with a simpler antenna structure that is smaller, lighter, and less expensive to produce.

[0024] An antenna for RFID communications, for example, in the Ultra-High Frequency (UHF) band, may include one or more conductive patches and one or more ground plates placed on an inlay (e g , on a top surface of the inlay) that can be wrapped around a substrate. The RFID tag may be rectangular prism shaped or cylindrically shaped (e.g., a three- dimensional rectangle or a three-dimensional cylinder) as shown and described in the Figures below. While the example RFID tags illustrated and described herein show a rectangular prism shaped tag and a cylindrically shaped tag, it is understood that the RFID tags described herein may include any suitable or desired shape and are not limited to rectangular or cylindrical shapes.

[0025] A potential advantage of the RFID tag disclosed herein is that the tag antenna may provide a wide bandwidth with high read range operating in the FCC RFID UHF (902-928 Mega-Hertz (MHz)) range while maintaining a small size. The tag may also be tuned to operate in other EPC Gen2 bands corresponding to the standards used in other countries (e.g., European: 865.5-868.5 MHz; Japan: 950-956 MHz) with similar performance. Another potential advantage to the presently disclosed RFID tag is that the fringing phenomenon (the loss of an electromagnetic wave or signal through the substrate) may be decreased due to the unique structure of the antenna, such as the use of two separate overlapping ground plates. Additionally, the substrate may be formed with one or more gaps, cavities, hollows, recesses, or the like in an interior portion without affecting antenna performance allowing for the tag to have a lighter weight and incur less materials cost.

[0026] FIG. 1A illustrates an example of an antenna structure for a radio-frequency identification (RFID) tag. The antenna structure 100 may include an inlay 102. The inlay 102 may, for example, be a Polyethylene Terephthalate (PET), Polyvinyl Chloride (PVC), Polycarbonate (PC), Polyethylene (PE), a doped PE, PETE or any derivative of PE, synthetic paper (e.g., Teslin™) or any other paper inlay, Poly dimethyl siloxane (PDMS), cotton / noil, or the like. The inlay 102 may include a top surface and a bottom surface. However, the inlay may be made of any other suitable materials or combination of materials. The bottom surface of the inlay 102 can include an adhesive, thereby providing the inlay with an adhesive backing. The inlay 102 may be a relatively flat or thin structure, as would be appreciated by those of skill in the art. In an example, the inlay 102 may have a thickness of 0.0025 mm, 0.05 mm, 0.075 mm, 0.1 mm, or any suitable or desired thickness. A first ground plate 104 may be located on the top surface of the inlay 102 and may be laterally spaced apart from a first conductive patch 106. A side or edge of the first ground plate 104 may be connected to an edge of the first conductive patch 106 by a connecting strip 108. Similarly, a secondground plate 110 may be located on the top surface of the inlay 102 and laterally spaced apart from a second conductive patch 112. An edge of the second ground plate 110 may be connected to an edge of the second conductive patch 112 by a second connecting strip 114. The ground plates and connecting strips are also conductive and, as discussed below, may be formed from the same conductive material as the conductive patches. In an example, the first ground plate 104, first conductive patch 106, and connecting strip 108 may be formed from a single metal (e.g., aluminum, silver, or copper) piece or sheet. Similarly, the second ground plate 110, second conductive patch 112, and the second connecting strip 114 may be formed from a single metal sheet, which may be a different sheet and / or a same or different type of metal used to form the first ground plate 104, first conductive patch 106, and connecting strip 108. The assembled antenna structure 100 may be formed such that an edge (e.g., a second edge) of the first conductive patch 106 may be laterally spaced apart from a second edge of the second conductive patch 112 so that a gap 120 is formed between the first conductive patch 106 and the second conductive patch 112.

[0027] In an example, as illustrated in FIGS. 1A and IB, connecting strip 108 and connecting strip 114 can be thin strips that are narrower than the conductive patches and the ground plates. Alternatively, in some examples as shown in FIGS. 1H and II, , the width of the connecting strips can be any width desired or necessary. For example, as shown in FIGS. 1H and II, connecting strip 108 can be equal (or substantially equal) to the width of the associated conductive patch and ground plate (first conductive patch 106 and first ground plate 104). Similarly, the width of second connecting strip 114 can be equal (or substantially equal) to the width of second conductive patch 112 and second ground plate 110.

[0028] It should be noted that the connecting strips may be of any suitable width in any embodiment described herein providing flexibility in design and manufacturing. The width of the connecting strips can be adjusted to optimize various performance characteristics of the RFID tag, such as read range, bandwidth, or resistance to environmental factors.

[0029] In the configuration of FIGS. 1H and II, where the connecting strips have the same width as the conductive patches and ground plates, the conductive patches, the ground plates, and the connecting strips can, in some example, be a continuous piece of conducting material that wraps around the substrate 116. This configuration can provide a continuous conductive surface along the side of a substrate 116, which can offer several advantages. For instance, it may enhance the overall conductivity of the antenna structure, potentially improving signal strength and read range. Additionally, the continuous conductive surface may provide bettershielding against interference or environmental factors that could affect the RFID tag's performance.

[0030] The continuous conductive surface may also contribute to the structural integrity of the RFID tag, providing a more robust connection between the conductive patches and the ground plates. This could potentially increase the durability of the tag, making it more resistant to physical stress or environmental conditions that might otherwise compromise the antenna structure. Furthermore, the equal-width configuration may simplify the manufacturing process, potentially reducing production costs and improving consistency in the final product.

[0031] In an example, the conductive patches, the connecting strips, and the ground plates may be etched on the inlay, screen printed on the inlay, adhered to the inlay, or otherwise joined with or located on the inlay via any suitable fabrication method or process. The ground plate, the connecting strips, and the conductive patches may be generally rectangular as shown in FIG. 1 A, but it is understood that any suitable shape may be used for any of the inlay, the conductive patches, the ground plates, or the connecting strips. Furthermore, though not required, the first conductive patch 106 and the second conductive patch 112 may be a similar shape and size to one another, the first ground plate 104 and the second ground plate 110 may be a similar shape and size to one another, and the first connecting strip 108 and the second connecting strip 114 may be a similar shape and size to one another. The conductive patches, ground plates, and connecting strips may be located on the inlay so that structures on the opposite side of the gap 120 are substantially symmetrical.

[0032] When wrapping the antenna structure 100 around a substrate, such as a substantially rectangular prism substrate (e g., a three-dimensional rectangular substrate), as illustrated in FIG. IB, the edges of the first ground plate 104, first conductive patch 106, second ground plate 110 and second conductive patch 112 can generally provide folding axes (as denoted by the dashed lines in FIG. 1 A). In particular, FIG. IB illustrates a view from above a top side of an RFID tag with the antenna structure of FIG. 1 A wrapped around a rectangular prism substrate. To fold the antenna structure 100 around the substrate 116, the inlay 102 may be folded such that a portion of the inlay 102 including the first conductive patch 106 and the second conductive patch 112 covers at least a portion of a top surface of the substrate 116 so that the gap 120 between the first conductive patch 106 and the second conductive patch 112 extends across or spans at least a portion of the width of the substrate 116 approximately in the middle thereof (measuring from the sides or ends of the substrate 116). In other examples, the gap 120 may not be located at or near the middle of the top surface of the substrate 116but may be located closer to one of the sides or ends of the substrate 116. An integrated circuit (IC) chip 118 may be located at any position along the length of the gap 120 to span the gap 120 between the first conductive patch 106 and the second conductive patch 112. In an example, the IC chip 118 may be an IC of any type or form factor, including but not limited to a die or packaged IC. Furthermore, when the antenna structure 100 is wrapped around the substrate 116, a portion of the inlay 102 including at least a portion of the second connecting strip 114 may be arranged along a side surface or end 122 of the substrate 116. Similarly, at least a portion of the inlay 102 including at least a portion of the connecting strip 108 may be arranged along the other side surface of the substrate 116 opposite the side surface or end 122 of the substrate 116 including the second connecting strip 114. Stated differently, the first and second connecting strips 108 and 114 may span generally between the top and bottom surfaces of the substrate 116 along opposite ends of the substrate 116

[0033] FIG. IC illustrates a view from below the bottom side of the RFID tag of FIG. IB. As discussed above, as the antenna structure 100 is wrapped around the substrate 116, the first ground plate 104 and the second ground plate 110 may be folded over such that they at least partially overlap on a bottom side or surface of the substrate 116. In an example, the first ground plate 104 can be wrapped on the bottom side of the substrate 116 so that the first ground plate 104 substantially or completely covers (or substantially completely covers) the second ground plate 110. In such an example, the portion of the inlay 102 including the second ground plate 110 may be in direct contact with the bottom side of the substrate 116 and the portion of the inlay including the first ground plate 104 may be in direct contact with the second ground plate 110. Alternatively, the portion of the inlay including the first ground plate 104 may be folded to be in direct contact with the bottom side or surface of the substrate 116 and the portion of the inlay including the second ground plate 110 may be folded over the top of the first ground plate 104 so as to fully or completely overlap or cover (or substantially fully overlap or cover) the first ground plate 104.

[0034] FIGS. 1 A-1C illustrate that the inlay 102 can be wrapped around the substrate 116 so that the conductive patches 106 and 112 form the gap 120 substantially in the middle of the top surface of the substrate 116 and the connecting strips 108 and 114 are located on the side end surfaces of the substrate 116. However, as illustrated in FIGS. ID and IE below, the inlay may be wrapped around the substrate 116 so that the conductive patches and connecting strips are shifted around (e g., laterally, circumferentially, or the like) so that they are located on different portions of the substrate 116 (e.g., are offset from the positions shown in FIGS. 1A-1C).

[0035] FIGS ID and IE illustrate alternate example embodiments of wrapping the antenna structure around the rectangular substrate. For example, as illustrated in FIG. ID, the inlay 102 may be wrapped around the substrate 116 so that the first conductive patch 106 wraps over the end of the substrate 116. similarly, at least a portion of the second ground plate 110 may wrap around the opposite end of the substrate 116 so that it is not located entirely on the bottom surface of the substrate 116. Such a shifting may cause the second connecting strip 114 to be shifted so that a portion of the second connecting strip 114 is located on the side end between the top surface and the bottom surface of the substrate 116, and another portion of the second connecting strip 114 extends over the top surface of the substrate.

[0036] FIG. IE shows the structure of FIG. ID with the substrate 116 made transparent, which shows the first conductive patch 106 wrapped around the edge of the substrate 116 and the connecting strip 108 located on the bottom surface of the substrate 116. It is understood that the inlay 102 may be wrapped around the substrate 116 and the conductive patches, the connecting strips, and the conductive plates may be positioned in any suitable or desired location on the substrate. Furthermore, the sizes (length or width) of the conductive patches, connecting strips, and conductive plates may be adjusted (e.g., made smaller or larger) as suitable or desired.

[0037] FIG. IF illustrates an alternate view from above the bottom side of the RFID tag of FIG. IB, showing the second ground plate 110 partially overlapping the first ground plate 104. In this configuration, a portion of the first ground plate 104 remains visible and uncovered by the second ground plate 110. This partial overlap arrangement may provide advantages in terms of antenna performance or manufacturing flexibility compared to full overlap or no overlap configurations.

[0038] FIG. 1G illustrates an alternate view from above the bottom side of the RFID tag of FIG. IB, showing a gap 124 between the first ground plate 104 and the second ground plate 110. In this configuration, the ground plates 104 and 110 are separated by the gap 124, rather than overlapping. This arrangement with a gap between the ground plates may provide certain advantages in terms of antenna performance, manufacturing flexibility, or adaptability to specific substrate geometries compared to overlapping configurations.

[0039] FIG. 2A illustrates a view from above a top side of a radio-frequency identification (RFID) tag with an antenna structure wrapped around another example rectangular prism substrate. An RFID tag 200 may include similar components to the RFID tag and antenna structures described above in FIGS. 1A-1E. For example, the RFID tag 200 may include a substrate 202 and an inlay 204 wrapped around the substrate 202. A first conductive patch206 may be located on a top surface of the inlay 204 laterally spaced apart from a second conductive patch 208. As discussed above, the conductive patches 206 and 208 may be connected to ground plates via a first connecting strip 210 and a second connecting strip 212, respectively. As discussed above, the connecting strips 210 and 212 may themselves be formed from conductive material (e.g., the same conductive material from which the first conductive patch 206 and the second conductive patch 208 are formed). The ground plates may overlap on the bottom side of the substrate 202 similar to what is described above for FIG. 1C. As illustrated in FIG. 2A, the connecting strips 210 and 212 may extend between a top surface and a bottom surface of the substrate 202 on side surfaces or side ends 214 and 216, respectively, of the substrate 202. Furthermore, the connecting strips 210 and 212 may be located at least partially on a portion of the inlay 204 located on a top side or top surface of the substrate 202 when the inlay 204 is wrapped around the substrate 202. As such, the connecting strips 210 and 210 may be wrapped around more of the surface of the substrate 202 as compared to, for example, the RFID tag 100.

[0040] The structure illustrated in FIG 2A illustrates that the height / thickness of the substrate can be reduced (e.g., to 1 mm) as comparted to the thickness / height of the substrate illustrated in FIGs. 1A-1C. By decreasing the substrate thickness while the length of the substrate increases (the size of the conductive patches and the width of the substrate may remain fixed), the antenna performance can remain the same. In an example, the range of the antenna may improve by reducing the length of the connecting strips 210 and 212 on the top of the substrate 202 in FIG. 2A by increasing the length of the conductive patches 206 and 208. In an example, the position of the connecting strips 210 and 212 (as well as connecting strips 108 and 114) may be shifted along the side ends of the substrates (e.g., from a middle or center position, closer to one of the edges of the side ends, or vice-versa). Additionally, or alternatively, the width of the connecting strips 210 and 212 (as well as connecting strips 108 and 114) may be made wider or narrower based on a desired resonance frequency. Performance of the disclosed antennas is not sensitive to a geometrical change of wrapping the inlay around the substrate, thus the antenna and RFID tag may take any suitable or desired shape.

[0041] FIG. 2B illustrates a view from above the bottom side of the RFID tag 200 of FIG. 2A. As illustrated in FIG. 2B, and similar to what is illustrated and described in 1C, two ground plates 216 and 218 may be overlapped on a bottom surface or bottom side of the substrate 202. Specifically, a portion of the inlay 204 containing a first ground plate 216 may be in direct contact with the bottom surface of the substrate 202 and a portion of the inlay 204containing a second ground plate 218 may be folded over the first ground plate 216. In such an example, the second ground plate 218 may completely cover, or substantially completely cover the first ground plate 216.

[0042] Alternatively, the portion of the inlay 204 containing the second ground plate 218 may be in direct contact with the substrate 202 and a portion of the inlay including the first ground plate 216 may be folded over and make contact with the second ground plate 218 to completely cover, or substantially completely cover the second ground plate 218.

[0043] The substrate (e.g., substrate 116 or 202) can have any suitable thickness. In an example, the substrate (e g., substrate 116 or 202) may have a thickness between about 1 millimeter (mm) to about 10 mm. The substrate may have a length of about 32 mm and a width of about 13 mm. The thickness of the substrate may be selected based on any suitable factor(s), such as but not limited to, the type of material from which the substrate is formed (e.g., a polycarbonate, foam, high-impact polystyrene (HIPS), or acrylonitrile butadiene styrene (ABS)), a desired read range of the RFID tag, or the like. In some examples, a thicker substrate can result in an increased read range of the RFID tag. It is understood that the dimensions of the substrate (e.g., the length, the width, or the thickness) may be adjusted as suitable or desired based, at least in part, on one or more of the factors listed above.

[0044] FIG. 3A illustrates an example of a cylindrical radio-frequency identification (RFID) tag. In an example, a cylindrical RFID tag 300 can include a substrate 302, a first conductive patch 304 connected to a first ground plate 306 and a second conductive patch 308 connected to a second ground plate 310. The first ground plate 306, first conductive patch 304, second conductive patch 308, and second ground plate 310 may be located on a top surface of an inlay 312, such as a PET, PVC, or paper inlay. Similar to the RFID tag assemblies discussed in FIGS. 1A-2B, the first conductive patch 304 may be connected to the first ground plate 306 by a first connecting strip 314. Likewise, the second conductive patch 308 may be connected to the second ground plate 310 by a second connecting strip 316.

[0045] FIGS. 3B-3F illustrate an assembly process for the cylindrical RFID tag of FIG. 3 A. Similar to the rectangular prism RFID tag discussed above, the cylindrical RFID tag 300 may be assembled by folding a portion of the inlay 312 having the ground plates around the substrate 302. For example, a portion of the inlay 312 including the second ground plate 310 may be folded over the substrate, as illustrated in FIG. 3B, so that the second ground plate 310 is positioned at or over a bottom side or a bottom surface of the substrate 302, as illustrated in FIG. 3C. Similarly, as illustrated in FIG. 3D, the portion of the inlay 312 including the first ground plate 306 may be wrapped around the substrate 302 so that the firstground plate 306 at least partially overlaps, and in some examples fully covers (or substantially fully covers), the second ground plate 310 on the bottom surface of the substrate 302, as illustrated in FIG. 3F, showing the bottom view of the assembled cylindrical RFID tag 300. As illustrated in FIG. 3E, the portions of the inlay 312 including the first connecting strip 314 and the second connecting strip 316 can be located on a side surface or side edge 318 of the cylindrical RFID tag 300, in some examples, on opposite sides of the side surface. A portion of the first connecting strip 314 and / or the second connecting strip 316 may also be located on the top surface of the assembled cylindrical RFID tag 300, similar to the example illustrated in FIG. 2A for a rectangular prism RFID tag 200.

[0046] As illustrated in FIGS. 1A-3F, the shape of the inlay, patches, and ground plates may generally correspond to the shape (e.g., rectangular prism, cylindrical) of the substrate chosen. For example, for a rectangular prism substrate as illustrated in FIGS 1A-1C and FIGS. 2A and 2B, the inlay, patches, and ground plates may be generally rectangular. For a cylindrical substrate as illustrated in FIGS 3A-3F, the inlay, patches, and ground plates may be circular or semicircular (or in the case of the inlay, may comprise a plurality of circular portions). Also, as mentioned previously, the tags are not limited to just rectangular prism shaped or cylindrically shaped substrates but can be adapted for a substrate of any suitable or desired shape. Also, as discussed above, the specific dimensions and proportions of the conductive patches, connecting strips, and ground plates of any of the configurations discussed in FIGS 1A-3F can be sized or adjusted as needed (e.g., the widths of each of the conductive patches, connecting strips, and ground plates can be made equal or substantially equal) to meet the requirements of different applications or to optimize specific performance characteristics of the RFID tag.

[0047] For example, FIG. 4A illustrates an example of an asymmetrical antenna structure 400, optionally including anti-tampering features. The antenna structure 400 comprises a left conducting patch 402 and a right conducting patch 404, which may be asymmetrically sized, shaped, and / or positioned. A first ground plate 406 is connected to the left conducting patch 402 via a left connecting strip 408, while a second ground plate 410 is connected to the right conducting patch 404 via a right connecting strip 412. The first ground plate 406 and second ground plate 410 may at least partially overlap, as described above. Alternatively, there may be a gap between the first ground plate 406 and second ground plate 410, as also described above. This asymmetrical configuration demonstrates the adaptability of the antenna structure design to accommodate various geometries and specialized features. FIG. 4A also depicts an optional anti-tamper pin 414 that is movable along an anti-tamper track 416. The anti-tamperpin 414 can be designed to support mechanical tearing of the antenna track, fulfilling an antitamper feature. Attempts to remove the RFID tag from an object or surface to which it is attached can cause the pin to break the antenna track, thereby disabling the tag and providing evidence of tampering.

[0048] FIG. 4B illustrates the asymmetrical antenna structure of FIG. 4A with the addition of a dielectric core 418. The dielectric core 418 can be positioned within the asymmetrical antenna structure 400, serving as a substrate around which the conductive elements are arranged. Specifically, the asymmetrical antenna structure 400 can be wrapped or positioned around the dielectric core 418. The dielectric core 418 can be formed from various materials with different dielectric properties, allowing for customization of the performance characteristics of the antenna structure. Examples of materials that can be used for the dielectric core include polycarbonate, foam, high-impact polystyrene (HIPS), or acrylonitrile butadiene styrene (ABS). These materials offer different permittivity values and mechanical properties, enabling the antenna structure to be adapted for specific applications or environmental conditions. This configuration demonstrates how the flexible design of the antenna structure can accommodate various internal structures, such as a dielectric core, including asymmetrical structures.

[0049] FIG. 5 illustrates an example of a method of fabricating a radio-frequency identification (RFID) tag. The method 500 can include or comprise a number of Operations or Steps. The Steps described herein are examples only, and the method can omit one or more of the listed Steps, can repeat Steps, can include other Steps, or can execute the Steps concurrently, substantially simultaneously, or in another order, as appropriate or desired.

[0050] Step 502 of the method 500 may include providing a substrate. As discussed above, the substrate may be formed from at least one of a ceramic, polycarbonate, foam, high- impact polystyrene (HIPS), or acrylonitrile butadiene styrene (ABS), cardboard, wood, plastic, including recyclable plastic, or the like. In an example, at least a portion of the substrate may be substantially rectangular or circular. The substrate may be three- dimensional so as to form a three-dimensional shape or object (e.g., a three dimensional rectangular prism or cylinder). In an example, the substrate may be a solid (or substantially solid) piece of material. In another example, a portion of the substrate (e.g., a middle portion of a three-dimensional rectangle) may be hollow or include one or more voids, negative spaces, or the like.

[0051] Step 504 of the method 500 may include forming an antenna structure. In an example, the antenna structure may comprise an inlay with a top surface and a bottomsurface. The inlay may be a PET, PVC, or paper inlay, and the bottom surface of the inlay may be configured to contact or attach to the substrate. For example, the inlay could include an adhesive backing. The antenna structure may also include a first conductive patch and a second conductive patch located on the top surface of the inlay. A first edge or a side of the first conductive patch may be laterally spaced apart from a first edge of the second conductive patch to form a gap between the first conductive patch and the second conductive patch.

[0052] The conductive patches may be a metal plate or may be a screen-printed patch or area printed with conductive ink. As described above, in general, the conductive patches, the connecting strips, and the ground patches may be etched on the inlay, screen printed on the inlay, adhered to the inlay, or otherwise joined with or located on the inlay via any suitable fabrication method or process. The inlay may be adhered or bonded to the substrate using an adhesive (e.g., using an optional adhesive backing), thin film transfer, hot liquid melt, glue, or the like. In an example the inlay may be laminated into a PVC card. In another example, the inlay may be attached to the substrate using ultrasonic welding. The conductive patches may each be connected to a corresponding ground plate (e.g., a first ground plate and a second ground plate) via thin (as compared to the conductive patches and the ground plates) conductive strips. In an example, the first conductive patch is connected to a first ground plate via a first conductive strip and a second conductive patch is connected to a second ground plate via a second conductive strip. The conductive patches, the metal strips, and the ground plates may be formed from the same material or metal, such as aluminum, silver, or copper. Alternatively, the ground plates, conductive patches, and the strips may be formed from carbon-based material such as carbon nanotubes, graphene-based composites, or the like. In such an example, the first ground plate, the first conductive strip, and the first conductive patch may be formed from a single metal piece. Similarly, the second ground plate, the second conductive strip, and the second conductive patch may be formed from a second single metal piece. The metal piece forming the first ground plate, the first conductive strip, and the first conductive patch may be a different metal piece and / or a different type of metal forming the second ground plate, the second conductive strip, and the second conductive patch.

[0053] At Step 506, the method 500 may include wrapping the antenna structure around the substrate. The antenna structure may be wrapped around the substrate such that a portion of the inlay including the first and second conductive patches covers at least a portion of the top surface of the substrate. Furthermore, a portion of the inlay including at least a portion of thefirst conductive strip may be arranged along a first side surface of the substrate and a portion of the inlay including at least a portion of the second conductive strip may be arranged along a second side surface of the substrate. The portions of the inlay including the ground plates may be wrapped around the bottom surface of the substrate such that the first ground plate at least partially overlaps the second ground plate on the bottom surface of the substrate.Alternatively, the portion of the inlay including the ground plates may be wrapped around the bottom surface of the substrate such that the second ground plate at least partially overlaps the first ground plate.

[0054] At Step 508, the method 500 may include locating an RFID chip on the RFID tag. An Integrated Circuit (IC) chip may be arranged to span the gap formed between the conductive patches at any portion along a length of the gap. Thus, the RFID structures described herein permit flexibility in IC chip placement without any degradation in antenna performance.

[0055] The RFID tags discussed herein may be of any suitable or desired size or shape and may be made in various thicknesses. By increasing the thickness (z-direction) of the substrate, while keeping the length (y-direction) and the width (x-direction) fixed, an antenna read range of the RFID tag may be considerably improved (compared to increasing the thickness of conventional tags). Furthermore, various types of IC chips may be used in the RFID tags described herein and various substrate materials (e.g., a polycarbonate, foam, high-impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS) or a ceramic) with different permittivity's and dielectric constants may be used to form the RFID tags without a reduction or degradation in antenna performance.

[0056] Example l is a radio-frequency identification (RFID) tag, comprising: a substrate, the substrate including: a top surface, a bottom surface, a first side surface and a second side surface; and an antenna structure comprising: an inlay, the inlay including a top surface and a bottom surface; a first conductive patch and a second conductive patch located on the top surface of the inlay, wherein a first edge of the first conductive patch is laterally spaced apart from a first edge of the second conductive patch to form a gap therebetween; a first ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the first conductive patch and connected to the first conductive patch by a first conductive strip; and a second ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the second conductive patch and connected to the second conductive patch by a second conductive strip; wherein the antenna structure is wrapped around the substrate such that: a portion of the inlay including the first and second conductive patches covers at least aportion of the top surface of the substrate; a portion of the inlay including at least a portion of the first conductive strip is arranged along the first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along the second side surface of the substrate; and the first ground plate at least partially overlaps the second ground plate on the bottom surface of the substrate.

[0057] In Example 2, the subject matter of Example 1 optionally includes an RFID chip is arranged to span the gap between the first conductive patch and the second conductive patch.

[0058] In Example 3, the subject matter of any one or more of Examples 1-2 optionally include subject matter wherein the substrate has a substantially rectangular prism shape.

[0059] In Example 4, the subject matter of any one or more of Examples 1-3 optionally include subject matter wherein the substrate has a substantially cylindrical shape.

[0060] In Example 5, the subject matter of any one or more of Examples 1-4 optionally include subject matter wherein the substrate is formed from at least one of: a polycarbonate, foam, high-impact polystyrene (HIPS), or acrylonitrile butadiene styrene (ABS).

[0061] In Example 6, the subject matter of any one or more of Examples 1-5 optionally include subject matter wherein at least one of the first conductive strip or the second conductive strip additionally extends along a portion of the inlay that wraps around a portion of at least one of the top surface or bottom surface of the substrate.

[0062] In Example 7, the subject matter of any one or more of Examples 1-6 optionally include subject matter wherein the first conductive patch has substantially a same size and a same shape as the second conductive patch.

[0063] In Example 8, the subject matter of Example 7 optionally includes subject matter wherein the first ground plate has substantially a same size and a same shape as the second ground plate.

[0064] In Example 9, the subject matter of any one or more of Examples 1-8 optionally include subject matter wherein the first ground plate, the first conductive strip, and the conductive patch are formed from a single metal piece.

[0065] In Example 10, the subject matter of Example 9 optionally includes subject matter wherein the second ground plate, the second conductive strip, and the second conductive patch are formed from a single metal piece.

[0066] In Example 11, the subject matter of Example 10 optionally includes subject matter wherein the first conductive patch, the first conductive strip, the first ground plate, the second conductive patch, the second conductive strip, and the second ground plate are formed from aluminum.

[0067] In Example 12, the subject matter of any one or more of Examples 1-11 optionally include subject matter wherein the RFID tag is operable in a read-range between 865.5 megahertz (MHz) to 956 MHz, inclusive.

[0068] In Example 13, the subject matter of any one or more of Examples 1-12 optionally include subject matter wherein a length of each of the first conductive strip and the second conductive strip is the same, and wherein the length corresponds to a thickness of the substrate between the top surface and the bottom surface.

[0069] In Example 14, the subject matter of any one or more of Examples 1-13 optionally include subject matter wherein the inlay is a Polyethylene Terephthalate (PET) inlay and the bottom surface of the inlay comprises an adhesive backing, and wherein the adhesive backing makes contact with the substrate.

[0070] In Example 15, the subject matter of any one or more of Examples 1-14 optionally include subject matter wherein at least one of: i) the first conductive patch has at least one different dimension than the second conductive patch, ii) the first conductive strip has at least one different dimension than the second conductive strip, or iii) the first ground plate has at least one different dimension than the second ground plate.

[0071] Example 16 is a method of fabricating a radio-frequency identification (RFID) tag, the method comprising: providing a substrate, the substrate including: a top surface, a bottom surface, a first side surface, and a second side surface; wrapping an antenna structure around the substrate, the antenna structure comprising: an inlay, the inlay including a top surface and a bottom surface; a first conductive patch and a second conductive patch located on the top surface of the inlay, wherein a first edge of the first conductive patch is laterally spaced apart from a first edge of the second conductive patch to form a gap therebetween; a first ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the first conductive patch and connected to the first conductive patch by a first conductive strip; and a second ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the second conductive patch and connected to the second conductive patch by a second conductive strip; and wherein the antenna structure is wrapped around the substrate such that: a portion of the inlay including the first and second conductive patches covers at least a portion of the top surface of the substrate; a portion of the inlay including at least a portion of the first conductive strip is arranged along the first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along the second side surface of the substrate; and the first ground plate at least partially overlaps the second ground plate on the bottom surface of the substrate.

[0072] In Example 17, the subject matter of Example 16 optionally includes arranging an RFID chip to span the gap between the first conductive patch and the second conductive patch.

[0073] In Example 18, the subject matter of any one or more of Examples 16-17 optionally include extending at least one of the first conductive strip or the second conductive strip along a portion of the inlay that wraps around at least one of the top surface or the bottom surface of the substrate.

[0074] In Example 19, the subject matter of any one or more of Examples 16-18 optionally include forming the first ground plate, the first conductive strip, and the first conductive patch from a single metal piece; and forming the second ground plate, the second conductive strip, and the second conductive patch from a second single metal piece.

[0075] In Example 20, the subject matter of any one or more of Examples 16-19 optionally include subject matter wherein the substrate is formed from at least one of: a polycarbonate, foam, high-impact polystyrene (HIPS), or acrylonitrile butadiene styrene (ABS).

[0076] In Example 21, the subject matter of any one or more of Examples 16-20 optionally include subject matter wherein the first ground plate has substantially a same size and a same shape as the second ground plate.

[0077] In Example 22, the subject matter of any one or more of Examples 16-21 optionally include subject matter wherein a length of the first conductive strip and the second conductive strip are substantially the same.

[0078] In Example 23, the subject matter of Example 22 optionally includes subject matter wherein the length of the first conductive strip and the second conductive strip corresponds to a thickness of the substrate between the top surface and the bottom surface.

[0079] In Example 24, the subject matter of any one or more of Examples 16-23 optionally include subject matter wherein at least one of i) the first conductive patch is sized differently from the second conductive patch, the first conductive strip is sized differently than the second conductive strip, or iii) the first ground plate is sized differently than the second ground plate.

[0080] Example 25 is an antenna structure for an RFID tag, comprising: an inlay, the inlay including a top surface and a bottom surface; a first conductive patch and a second conductive patch located on the top surface of the inlay, wherein a first edge of the first conductive patch is laterally spaced apart from a first edge of the second conductive patch to form a gap therebetween; a first ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the first conductive patch and connected to the firstconductive patch by a first conductive strip; and a second ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the second conductive patch and connected to the second conductive patch by a second conductive strip.

[0081] In Example 26, the subject matter of Example 25 optionally includes subject matter wherein an RFID chip is arranged to span the gap between the first conductive patch and the second conductive patch.

[0082] In Example 27, the subject matter of any one or more of Examples 25-26 optionally include subject matter wherein the antenna structure is configured to wrap around a substrate such that: a portion of the inlay including the first and second conductive patches covers at least a portion of a top surface of the substrate; a portion of the inlay including at least a portion of the first conductive strip is arranged along a first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along a second side surface of the substrate; and the first ground plate at least partially overlaps the second ground plate on a bottom surface of the substrate.

[0083] In Example 28, the subject matter of Example 27 optionally includes subject matter wherein at least one of the first conductive strip or the second conductive strip additionally extends along a portion of the inlay that wraps around a portion of at least one of the top surface or bottom surface of the substrate.

[0084] In Example 29, the subject matter of any one or more of Examples 25-28 optionally include subject matter wherein the antenna structure has an asymmetrical shape.

[0085] In Example 30, the subject matter of any one or more of Examples 25-29 optionally include subject matter wherein the antenna structure is configured to wrap around a substrate such that: a portion of the inlay including the first and second conductive patches covers at least a portion of a top surface of the substrate; a portion of the inlay including at least a portion of the first conductive strip is arranged along a first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along a second side surface of the substrate; and the first ground plate and the second ground plate are separated by a gap on a bottom surface of the substrate.

[0086] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments that may be practiced. These embodiments are also referred to herein as “examples.” Such examples may include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0087] As used herein, the terms “substantially” or “generally” refer to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is “substantially” or “generally” enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking, the nearness of completion will be so as to have generally the same overall result as if absolute and total completion were obtained. The use of “substantially” or “generally” is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result. For example, an element, combination, embodiment, or composition that is “substantially free of’ or “generally free of’ an element may still actually contain such element as long as there is generally no significant effect thereof.The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments may be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is to allow the reader to quickly ascertain the nature of the technical disclosure and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the embodiments should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A radio-frequency identification (RFID) tag, comprising: a substrate, the substrate including: a top surface, a bottom surface, a first side surface and a second side surface; and an antenna structure comprising: an inlay, the inlay including a top surface and a bottom surface; a first conductive patch and a second conductive patch located on the top surface of the inlay, wherein a first edge of the first conductive patch is laterally spaced apart from a first edge of the second conductive patch to form a gap therebetween; a first ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the first conductive patch and connected to the first conductive patch by a first conductive strip; and a second ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the second conductive patch and connected to the second conductive patch by a second conductive strip; wherein the antenna structure is wrapped around the substrate such that: a portion of the inlay including the first and second conductive patches covers at least a portion of the top surface of the substrate; a portion of the inlay including at least a portion of the first conductive strip is arranged along the first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along the second side surface of the substrate; and the first ground plate at least partially overlaps the second ground plate on the bottom surface of the substrate.

2. The RFID tag of claim 1, further comprising: an RFID chip is arranged to span the gap between the first conductive patch and the second conductive patch.

3. The RFID tag of claim 1, wherein the substrate has a substantially rectangular prism shape.

4. The RFID tag of claim 1, wherein the substrate has a substantially cylindrical shape.

5. The RFID tag of claim 1, wherein the substrate is formed from at least one of: a polycarbonate, foam, high-impact polystyrene (HIPS), or acrylonitrile butadiene styrene (ABS).

6. The RFID tag of claim 1, wherein at least one of the first conductive strip or the second conductive strip additionally extends along a portion of the inlay that wraps around a portion of at least one of the top surface or bottom surface of the substrate.

7. The RFID tag of claim 1, wherein the first conductive patch has substantially a same size and a same shape as the second conductive patch.

8. The RFID tag of claim 7, wherein the first ground plate has substantially a same size and a same shape as the second ground plate.

9. The RFID tag of claim 1, wherein the first ground plate, the first conductive strip, and the conductive patch are formed from a single metal piece.

10. The RFID tag of claim 9, wherein the second ground plate, the second conductive strip, and the second conductive patch are formed from a single metal piece.

11. The RFID tag of claim 10, wherein the first conductive patch, the first conductive strip, the first ground plate, the second conductive patch, the second conductive strip, and the second ground plate are formed from aluminum.

12. The RFID tag of claim 1, wherein the RFID tag is operable in a read-range between 865.5 mega-hertz (MHz) to 956 MHz, inclusive.

13. The RFID tag of claim 1, wherein a length of each of the first conductive strip and the second conductive strip is the same, and wherein the length corresponds to a thickness of the substrate between the top surface and the bottom surface14. The RFID tag of claim 1, wherein the inlay is a Polyethylene Terephthalate (PET) inlay and the bottom surface of the inlay comprises an adhesive backing, and wherein the adhesive backing makes contact with the substrate.

15. The RFID tag of claim 1, wherein at least one of: i) the first conductive patch has at least one different dimension than the second conductive patch, ii) the first conductive strip has at least one different dimension than the second conductive strip, or iii) the first ground plate has at least one different dimension than the second ground plate.

16. A method of fabricating a radio-frequency identification (RFID) tag, the method comprising: providing a substrate, the substrate including: a top surface, a bottom surface, a first side surface, and a second side surface; wrapping an antenna structure around the substrate, the antenna structure comprising: an inlay, the inlay including a top surface and a bottom surface; a first conductive patch and a second conductive patch located on the top surface of the inlay, wherein a first edge of the first conductive patch is laterally spaced apart from a first edge of the second conductive patch to form a gap therebetween; a first ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the first conductive patch and connected to the first conductive patch by a first conductive strip; and a second ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the second conductive patch and connected to the second conductive patch by a second conductive strip; and wherein the antenna structure is wrapped around the substrate such that: a portion of the inlay including the first and second conductive patches covers at least a portion of the top surface of the substrate;a portion of the inlay including at least a portion of the first conductive strip is arranged along the first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along the second side surface of the substrate; and the first ground plate at least partially overlaps the second ground plate on the bottom surface of the substrate.

17. The method of claim 16, further comprising: arranging an RFID chip to span the gap between the first conductive patch and the second conductive patch.

18. The method of claim 16, further comprising: extending at least one of the first conductive strip or the second conductive strip along a portion of the inlay that wraps around at least one of the top surface or the bottom surface of the substrate.

19. The method of claim 16, further comprising: forming the first ground plate, the first conductive strip, and the first conductive patch from a single metal piece; and forming the second ground plate, the second conductive strip, and the second conductive patch from a second single metal piece.

20. The method of claim 16, wherein the substrate is formed from at least one of: a polycarbonate, foam, high-impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS) or a ceramic.

21. The method of claim 16, wherein the first ground plate has substantially a same size and a same shape as the second ground plate.

22. The method of claim 16, wherein a length of the first conductive strip and the second conductive strip are substantially the same.

23. The method of claim 22, wherein the length of the first conductive strip and the second conductive strip corresponds to a thickness of the substrate between the top surface and the bottom surface.

24. The method of claim 15, wherein at least one of i) the first conductive patch is sized differently from the second conductive patch, the first conductive strip is sized differently than the second conductive strip, or iii) the first ground plate is sized differently than the second ground plate.

25. An antenna structure for an RFID tag, comprising: an inlay, the inlay including a top surface and a bottom surface; a first conductive patch and a second conductive patch located on the top surface of the inlay, wherein a first edge of the first conductive patch is laterally spaced apart from a first edge of the second conductive patch to form a gap therebetween; a first ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the first conductive patch and connected to the first conductive patch by a first conductive strip; and a second ground plate located on the top surface of the inlay laterally spaced apart from a second edge of the second conductive patch and connected to the second conductive patch by a second conductive strip.

26. The antenna structure of claim 25, wherein an RFID chip is arranged to span the gap between the first conductive patch and the second conductive patch.

27. The antenna structure of claim 25, wherein the antenna structure is configured to wrap around a substrate such that: a portion of the inlay including the first and second conductive patches covers at least a portion of a top surface of the substrate; a portion of the inlay including at least a portion of the first conductive strip is arranged along a first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along a second side surface of the substrate; and the first ground plate at least partially overlaps the second ground plate on a bottom surface of the substrate.

28. The antenna structure of claim 27, wherein at least one of the first conductive strip or the second conductive strip additionally extends along a portion of the inlay that wraps around a portion of at least one of the top surface or bottom surface of the substrate.

29. The antenna structure of claim 25, wherein the antenna structure has an asymmetrical shape.

30. The antenna structure of claim 25, wherein the antenna structure is configured to wrap around a substrate such that: a portion of the inlay including the first and second conductive patches covers at least a portion of a top surface of the substrate; a portion of the inlay including at least a portion of the first conductive strip is arranged along a first side surface of the substrate; a portion of the inlay including at least a portion of the second conductive strip is arranged along a second side surface of the substrate; and the first ground plate and the second ground plate are separated by a gap on a bottom surface of the substrate.

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