NFC antenna and intelligent lock

Abstract

The invention discloses an NFC antenna and an intelligent lock, and aims to solve the problem of non-uniform magnetic field distribution of an existing NFC antenna. The NFC antenna includes: a substrate; the outer ring coil and the inner ring coil are arranged on the surface of the same side of the substrate and bear current in the same direction during working; and a shielding layer. The key point is that the shielding layer is arranged on the substrate, is positioned in an area between the outer ring coil and the inner ring coil, in which magnetic fields generated by homodromous current are mutually offset, and is used for blocking the offset magnetic fields. Through the combined design of homodromous current superposition enhancement and shielding layer elimination offset, a uniform and high-strength magnetic field is formed in the whole induction area, the induction blind area is eliminated, and the identification success rate of various NFC cards and the user experience are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency identification (RFID), and in particular to an NFC card reader antenna for a smart lock and a smart lock comprising the antenna. Background Art

[0002] Near-field communication (NFC) technology, a convenient contactless communication method, has been widely adopted in smart door locks. Users can easily unlock the door using an NFC card or mobile phone, greatly improving convenience. The NFC system in a smart lock primarily consists of a card reader and a tag. The NFC antenna installed in the door lock acts as the reader antenna, and its performance directly determines the user experience.

[0003] An ideal NFC antenna should provide a uniform magnetic field distribution within its sensing area to ensure that users receive a consistent and reliable response regardless of card location. However, most conventional smart lock NFC reader antennas currently use a single-branch winding coil structure. The magnetic field generated by this structure has a serious problem of uneven distribution: the magnetic field is mainly concentrated near the coil routing, resulting in excessively high field strength at the edge and relatively weak field strength at the center of the antenna. As shown in the simulation data (see Figure 2), the magnetic field generated by this structure is mainly concentrated near the coil routing, resulting in excessively high field strength at the edge and relatively weak field strength at the center of the antenna. Figure 1 As shown in Figure 7, at a distance of 2 mm from this single-branch antenna, the magnetic field strength in its center is only about 15 A / m, while the maximum magnetic field strength near the coil reaches 34 A / m. This significant difference in field strength creates a sensing "blind spot" at the center of the antenna. When a user swipes an NFC card, especially a small one like a key fob, in this area (as shown in Figure 7), the tag chip inside the card may not receive sufficient sensing energy to activate, causing the swipe to fail. This uneven magnetic field distribution is a root cause of problems that affect user experience and product reliability.

[0004] Therefore, how to fundamentally improve the uniformity of the magnetic field distribution at close range of the antenna and eliminate the induction blind area has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide an NFC antenna and a smart lock, aiming to solve the problem in the prior art that NFC card reader antennas have a sensing blind spot due to uneven magnetic field distribution and weak magnetic field in the central area.

[0006] A first aspect of the present invention provides an NFC antenna, comprising: substrate; an outer coil and an inner coil, the outer coil and the inner coil being disposed on the same side surface of the substrate, and the outer coil surrounding the inner coil, wherein the outer coil and the inner coil are configured to carry current in the same direction during operation; and The shielding layer is provided on the substrate and is located in the area between the outer coil and the inner coil, and is used to block or weaken the mutually offset magnetic fields generated by the outer coil and the inner coil due to the same-direction current.

[0007] As can be seen, the present invention, by nesting an inner coil carrying a current in the same direction within an outer coil, reshapes the magnetic field configuration across the entire sensing area. On the one hand, by leveraging the principle of magnetic field superposition, the field strength in the weaker central region of a traditional single-coil antenna is effectively enhanced, eliminating the field strength distribution from being concentrated solely at the coil edges. On the other hand, the present invention addresses the inherent unevenness of the "magnetic field cancellation zone" created between the coils in the dual-coil structure. By precisely placing a shielding layer with a specific function within this cancellation zone, the negative effects inherent to the structure are actively eliminated, thereby ensuring uniform magnetic field distribution across the entire sensing area. The antenna of the present invention generates a stronger and more uniform magnetic field across the entire sensing area, particularly in the central region. This not only completely eliminates blind spots but also significantly improves compatibility and read success rates for NFC cards of various sizes (especially small ones), optimizing the user experience. Furthermore, locating the inner and outer coils on the same side of the substrate simplifies the manufacturing process and reduces production costs.

[0008] Optionally, the shielding layer is a metal shielding layer.

[0009] It can be seen that the use of a metal shielding layer, taking advantage of its good conductive properties, can efficiently block or reflect the magnetic field, thereby achieving an excellent magnetic field shielding effect at a lower cost.

[0010] Optionally, the shielding layer and the outer coil are located on opposite sides of the substrate.

[0011] It can be seen that placing the shielding layer and the coil on both sides of the substrate can, on the one hand, use the substrate as an insulating isolation to avoid electrical short circuit between the shielding layer and the coil; on the other hand, it simplifies the process complexity of single-sided wiring and facilitates production and manufacturing.

[0012] Optionally, the outer coil and the inner coil are connected in series by a continuous conductive wire through a via hole provided on the substrate.

[0013] It can be seen that by connecting the inner and outer coils in series through vias, it can structurally ensure that the currents in the two coils are strictly in the same direction and equal in magnitude, thereby ensuring the stability and consistency of the magnetic field superposition effect and improving the reliability of the product.

[0014] Optionally, the outer coil and the inner coil are concentrically arranged.

[0015] It can be seen that the concentric setting makes the overall structure of the antenna have good symmetry, which helps to produce a more regular and uniform magnetic field distribution, reduces the difference in recognition performance caused by different card swiping angles, and improves the consistency of recognition.

[0016] Optionally, a π-type matching network is further included, which includes a reactance element connected in series to the antenna loop and two parallel reactance elements connected between the two ends of the series reactance element and the ground, respectively, for adjusting the impedance matching between the antenna and an NFC card reader module.

[0017] It can be seen that by setting up a π-type matching network, the input impedance of the antenna can be flexibly adjusted to achieve the best conjugate matching state with the NFC card reader module, thereby maximizing the power transmission efficiency between the antenna and the chip, obtaining a longer card reading distance and higher system stability.

[0018] Optionally, both the outer coil and the inner coil are rectangular coils.

[0019] It can be seen that the rectangular coil shape can better match the usually rectangular installation area on the smart lock panel, thereby maximizing the antenna size within a limited space and improving space utilization.

[0020] Optionally, the shielding layer includes two spaced-apart separate shielding blocks, one of which is disposed between one long side of the outer coil and one long side adjacent to the inner coil, and the other is disposed between the other long side of the outer coil and another long side adjacent to the inner coil.

[0021] It can be seen that in view of the fact that the magnetic field cancellation of rectangular coils mainly occurs between the long sides, the shielding layer is designed as two separate shielding blocks, which can accurately shield the cancellation area and avoid unnecessary shielding of the non-cancellation area. While effectively solving the problem, it saves shielding materials and reduces costs.

[0022] Optionally, the width of each shielding block is configured so that its two side edges correspond to the outer edge of the long side of the inner coil and the inner edge of the long side of the outer coil respectively.

[0023] It can be seen that precisely configuring the width of the shielding block to just cover the area between the inner and outer coils can ensure the most effective shielding of the magnetic field cancellation area while avoiding excessive shielding of the effective magnetic field area of ​​the coil itself, thereby optimizing the overall performance of the antenna.

[0024] A second aspect of the present invention provides a smart lock comprising an NFC antenna as described in any one of the first aspects of the present invention.

[0025] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0027] Figure 1 This is a schematic diagram of the magnetic field simulation of a single-branch antenna in the prior art; Figure 2 1 is a planar schematic diagram of the NFC antenna structure according to an embodiment of the present invention; Figure 3 2. This is a schematic diagram of the magnetic field simulation of the NFC antenna according to an embodiment of the present invention at a position d=2 mm. Figure 4 This is a schematic diagram of the magnetic field simulation of the NFC antenna at a position d = 2 mm when the shielding layer is increased inward by 1 mm according to an embodiment of the present invention; Figure 5 is a three-dimensional view of one side surface of a display substrate according to an embodiment of the present invention; Figure 6 is a three-dimensional view of the other side surface of the display substrate according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the magnetic field distribution principle of the internal and external branch coils of the present invention; Figure 8 This is a schematic diagram showing the problems that exist when using a single-branch antenna in the prior art when swiping large-size and small-size NFC cards.

[0028] Explanation of the accompanying reference numerals: 1. Main coil; 101. Outer coil; 102. Inner coil; 2. Π-type matching network; 3. Shielding layer; 4. Via hole; 5. NFC card reader module; 6. Substrate. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0030] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0031] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0032] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0033] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures. Example 1

[0034] See also Figure 2 、 Figure 3 、 Figure 5 、 Figure 6 and Figure 7 This embodiment provides an NFC antenna. The basic structure of the antenna includes a substrate 6, a main antenna 1 disposed on the substrate 6, and a shielding layer 3.

[0035] Combine Figure 2 、 Figure 5 and Figure 7 Main antenna 1 consists of an outer coil 101 and an inner coil 102, which are arranged on the same side of substrate 6. Outer coil 101 surrounds inner coil 102. Placing both coils on the same surface allows the antenna to be fabricated using simplified processes such as single-sided PCB etching or FPC, reducing production costs.

[0036] During operation, the outer coil 101 and the inner coil 102 are configured to carry current in the same direction. Figure 7 According to the principle shown, the unidirectional current makes the magnetic fields generated by the two coils in the center area of ​​the inner coil 102 and the outer area of ​​the outer coil 101 consistent in direction, forming a magnetic field superposition effect. This design significantly enhances the field strength in the center area of ​​the antenna and concentrates the maximum magnetic field area there. Figure 3 The simulation results show that at a distance of 2 mm from the antenna, the field strength in the central area of ​​the antenna of the present invention can reach 42.9 A / m, which is much higher than Figure 1 The center field strength of the traditional single-coil antenna shown is about 15A / m, which effectively solves the "center blind spot" problem of traditional antennas.

[0037] However, the same direction current structure will also generate magnetic fields in opposite directions in the area between the outer edge of the inner coil 102 and the inner edge of the outer coil 101, thereby forming a "magnetic field cancellation area", such as Figure 7 To solve this problem, a shielding layer 3 is provided in this embodiment. The shielding layer is preferably a metal shielding layer made of a conductive material, such as copper foil. Figure 5As shown, the shielding layer 3 is preferably disposed on the other surface of the substrate 6, i.e., the surface opposite the surface where the main antenna 1 is located, to achieve spatial isolation. It is spatially located directly opposite the magnetic field cancellation region, thereby blocking or weakening the mutually canceling magnetic fields in this region, thereby avoiding the formation of new sensing blind spots. Example 2

[0038] This embodiment provides a further preferred structure based on the first embodiment.

[0039] In a preferred embodiment, Figure 2 、 Figure 5 and Figure 6 As shown, the outer coil 101 and the inner coil 102 are connected by a continuous wire through two vias 4 provided on the substrate 6 to form a series loop. This design ensures that the current directions in the inner and outer coils 101 are completely consistent, improving product reliability and performance consistency.

[0040] In another preferred embodiment, the outer coil 101 and the inner coil 102 are concentrically arranged. This symmetrical structure helps to generate a more regular and uniform magnetic field distribution, thereby improving the recognition consistency of cards swiped at any angle.

[0041] To achieve the ideal shielding effect, the size of the shielding layer 3 should be precisely configured to effectively block the magnetic field offset while avoiding unnecessary reduction in the overall performance of the antenna. If the shielding layer is too large, it may unnecessarily shield the effective magnetic field superposition area, which will reduce the overall performance of the antenna. For example, compared Figure 3 and Figure 4 The simulation results show that when the shielding layer size exceeds the optimal coverage range and increases inward by 1 mm, the maximum magnetic field strength decreases from 42.92 A / m to 42.52 A / m, which confirms the importance of precisely controlling the shielding layer size.

[0042] In addition, if Figure 2 and Figure 7 As shown, the antenna may also include a π-type matching network 2, which is connected between the main antenna 1 and the NFC card reader module 5 at the rear end. This network is used to accurately adjust the overall impedance of the antenna to achieve optimal matching with the NFC card reader module 5. A typical π-type matching network 2 includes a reactive element (such as an inductor or capacitor) connected in series with the antenna loop and two parallel reactive elements (such as capacitors or inductors) connected between the two ends of the series reactive element and the ground. By adjusting the parameters of these components, the highest power transmission efficiency can be guaranteed to obtain better read and write distance and stability. The typical π-type matching network is prior art and will not be described here. Example 3

[0043] This embodiment provides an optimized design particularly suitable for smart lock panels.

[0044] In this embodiment, both the outer coil 101 and the inner coil 102 are rectangular coils. This shape can better utilize the rectangular space commonly found on smart lock panels. For rectangular coils, magnetic field cancellation mainly occurs between the two parallel long sides. Therefore, the shielding layer 3 can be optimized to be two separated shielding blocks spaced apart, such as Figure 2 As shown in Figure 1, one shielding block is positioned between the upper long side of the outer coil 101 and the upper long side of the inner coil 102; the other shielding block is positioned between the lower long side of the outer coil 101 and the lower long side of the inner coil 102. The spacing between the two shielding blocks corresponds to the vertical distance between the two long sides of the inner coil 102. This split design precisely addresses key issues with minimal material and at the lowest cost.

[0045] To achieve optimal shielding, the width of each shielding block is precisely configured: one edge aligns with the outer edge of the corresponding long side of inner coil 102, and the other edge aligns with the inner edge of the corresponding long side of outer coil 101. This configuration ensures that the shielding layer completely covers the magnetic field cancellation area, eliminating the blind spots between coils while maximally preserving the effective magnetic field in other areas of the antenna, thus optimizing antenna performance.

[0046] In some specific wiring implementations, in order to provide necessary electrical clearance for the electrical connection structures of the antenna (such as feed points, vias, or leads to matching networks), the two separate shielding blocks can be designed to have asymmetrical shapes or sizes. Figure 2 As shown, the shielding block on one side can have a partial cutout or be smaller overall than the shielding block on the other side to avoid the corresponding electrical connection area. This design is an important engineering practice, the purpose of which is to prevent unnecessary parasitic capacitance or signal coupling between the shielding layer and the key electrical nodes of the antenna, thereby ensuring the stability of the antenna input impedance and the effectiveness of the matching network, and avoiding negative impacts on the resonance characteristics and performance of the antenna itself. Example 4

[0047] This embodiment provides a smart lock, characterized by including the NFC antenna described in any of the above embodiments. The NFC antenna is installed inside the housing or panel of the smart lock to form a smart lock with superior performance. Through the unique design of the outer and inner coils 102 combined with the shielding layer, an NFC card reader antenna with high magnetic field strength, uniform distribution, and no induction blind spot is finally obtained, which can reliably identify various NFC cards (solving the problem in the background art such as Figure 8 The existing technical problems shown above are solved), which significantly improves the user experience and market competitiveness of smart lock products.

[0048] In summary, the present invention significantly enhances the magnetic field strength in the antenna's central region by combining outer coil 101 with inner coil 102 and utilizing unidirectional currents to achieve magnetic field superposition. Furthermore, the inventive shielding layer provided on substrate 6 precisely eliminates the cancellation zone created by the reverse magnetic field between the coils. This combined design of "enhancement" and "elimination" ultimately creates a stronger and more evenly distributed magnetic field throughout the antenna's sensing area, completely resolving the blind spot issue of existing technologies. This improves compatibility and read success rates for NFC cards of various sizes, providing users with a smoother and more reliable card swiping experience.

[0049] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. An NFC antenna, characterized in that: include: substrate; an outer coil and an inner coil, the outer coil and the inner coil being disposed on the same side surface of the substrate, and the outer coil surrounding the inner coil, wherein the outer coil and the inner coil are configured to carry current in the same direction during operation; and The shielding layer is provided on the substrate in a region between the outer coil and the inner coil, and is used to block or weaken the mutually canceling magnetic fields generated by the outer coil and the inner coil due to the unidirectional current.

2. The NFC antenna according to claim 1, wherein The shielding layer is a metal shielding layer.

3. The NFC antenna according to claim 1 or 2, characterized in that The shielding layer and the outer coil are respectively located on two opposite sides of the substrate.

4. The NFC antenna according to claim 1, wherein: The outer coil and the inner coil are connected in series by a continuous conductive wire through a via hole provided on the substrate.

5. The NFC antenna according to claim 1, wherein: The outer coil and the inner coil are concentrically arranged.

6. The NFC antenna according to claim 1, wherein: The device further includes a π-type matching network, which includes a reactance element connected in series to the antenna loop and two parallel reactance elements connected between the two ends of the series reactance element and the ground, for adjusting the impedance matching between the antenna and an NFC card reader module.

7. The NFC antenna according to claim 1, wherein: The outer coil and the inner coil are both rectangular coils.

8. The NFC antenna according to claim 7, wherein: The shielding layer includes two separated shielding blocks arranged at intervals, wherein one shielding block is arranged between one long side of the outer ring coil and one long side adjacent to the inner ring coil, and the other shielding block is arranged between the other long side of the outer ring coil and the other long side adjacent to the inner ring coil.

9. The NFC antenna according to claim 8, characterized in that The width of each shielding block is configured so that two side edges thereof correspond to the outer edge of the long side of the inner coil and the inner edge of the long side of the outer coil respectively.

10. A smart lock, characterized in that: The NFC antenna comprises the NFC antenna according to any one of claims 1 to 9.

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