Vehicle-mounted NFC antenna

Abstract

This invention discloses a vehicle-mounted NFC antenna, including a substrate and at least one coil. One coil is disposed on a first side of the substrate. The coil includes a rectangular coil loop and a central branch. The coil loop includes four loop branches. The central region of the coil loop (corresponding to test point C) has a magnetic field component parallel to the substrate. The magnetic field energy can be obtained by the NFC antenna of the test terminal under any vertical card-swiping posture. Furthermore, compared to the uniform magnetic field distribution of traditional antennas, this invention has at least two loop branches with stronger magnetic fields (corresponding to test points E and S). When performing test cases that traditional antennas cannot meet, it can ensure that the energy intensity of the electromagnetic beam perpendicular to the test terminal in these two states reaches the induction detection standard at a specified distance. In summary, this invention proposes an improvement over traditional antennas, enabling special test points to meet test requirements without the need for deviation certification (downgrade certification), and meeting user needs.

Description

Technical Field

[0001] This utility model relates to the field of short-range communication antenna technology, and in particular to a vehicle-mounted NFC antenna. Background Technology

[0002] NFC, or Near Field Communication, is a short-range, high-frequency wireless communication technology that allows devices using NFC to exchange data when they are close to each other. In the automotive industry, NFC served as the first generation of digital keys, and Apple adopted NFC as its digital key, setting authentication requirements for swipe distance and swipe gesture.

[0003] Traditional NFC antenna design Figure 3 As shown, a multi-turn wound circuit coil loop is used to form a radiating magnetic field. The magnetic field distribution of this NFC antenna at the XoZ and YoZ interfaces is shown below. Figure 4 As shown, the magnetic field at the center is primarily perpendicular to the NFC antenna, with a ring-shaped magnetic field component around the perimeter. This design cannot meet the following test cases for Apple CarKey certification:

[0004] 1. For example Figure 5 When the terminal is at point C and at a 90° angle to the NFC antenna (corresponding to Test Case 5), because the magnetic field in its central area has no horizontal component, the terminal cannot obtain magnetic field energy when it enters, and the sensing distance is close or even non-sensing.

[0005] 2. Figure 6 In the test case, the terminal was at a 45° angle to the antenna at point E (corresponding to Test Case 9). The overlapping area of ​​the antennas was insufficient, the magnetic field strength was low, and it was difficult to obtain energy.

[0006] 3. Figure 7 The display shows that the terminal is at a 45° angle to the antenna at point S (corresponding to Test Case 12), which also means it cannot meet the certification requirements.

[0007] The root cause of the above problems is that the Apple CarKey authentication method is fixed. Therefore, no matter how the position of the traditional NFC antenna is adjusted, the structural design of the conventional antenna will inevitably result in three test cases that cannot meet the authentication requirements (Test Cases 5 / 9 / 12). This is an inherent defect in the traditional antenna structural design.

[0008] Of course, the problems with multi-turn coil designs are not limited to Apple CarKey authentication testing; similar issues exist in Android NFC authentication testing. A common practice in existing technologies is to use a deviation authentication (authentication downgrade) method at these three test points.

[0009] Furthermore, the multi-turn coil design presents numerous inconveniences for users when used in daily applications, particularly when employing it in Test Cases 5 / 9 / 12. Due to insufficient antenna overlap and low magnetic field strength, the magnetic field energy is difficult for the terminal to capture, resulting in poor device sensitivity. This often necessitates repeated adjustments to the terminal's angle and position when near the NFC antenna, requiring multiple attempts to successfully complete operations such as door unlocking, significantly impacting usability and causing inconvenience.

[0010] Therefore, it is necessary to improve the structural design of traditional NFC antennas. Utility Model Content

[0011] To overcome the technical problem that traditional NFC antennas described in the prior art cannot pass at least three test cases, this utility model provides a vehicle-mounted NFC antenna. By improving the antenna structure design, this vehicle-mounted NFC antenna can pass all the above test cases, meet the Apple CarKey certification requirements without taking deviation certification (certification downgrade), and improve the user experience.

[0012] The technical solution adopted by this utility model to solve its problem is:

[0013] An in-vehicle NFC antenna, comprising:

[0014] A substrate, the substrate including a first side surface and a second side surface disposed opposite to each other;

[0015] A first coil is disposed on the first side. The first coil includes a first coil loop that is rectangular in shape. The first coil loop includes a first loop branch, a second loop branch, a third loop branch, and a fourth loop branch. The first loop branch and the third loop branch are arranged opposite to each other, and the second loop branch and the fourth loop branch are arranged opposite to each other.

[0016] The central region of the first coil loop has a magnetic field component parallel to the substrate. Furthermore, the magnetic field strength of the third loop stub is greater than that of the first loop stub, and the magnetic field strength of the fourth loop stub is greater than that of the second loop stub; or, the magnetic field strength of the first loop stub is greater than that of the third loop stub, and the magnetic field strength of the second loop stub is greater than that of the fourth loop stub.

[0017] In the above technical solution, the central region of the first coil loop has a magnetic field component parallel to the substrate, that is, the magnetic field generated by the first coil when energized has a horizontal vector in the horizontal direction in this central region. Therefore, when the test terminal enters the magnetic field in any vertical card-swiping posture, a horizontal magnetic field component will pass through the NFC antenna coil of the test terminal, enabling the NFC antenna of the test terminal to obtain sufficient magnetic field energy, thereby meeting the test requirements of point C (corresponding to Test Case 5).

[0018] Furthermore, between the first and third loop branches, and between the second and fourth loop branches, there must be two branches whose magnetic field strength is greater than that of the other two branches. The loop branches with the stronger magnetic field correspond to the E and S test points. Therefore, when using the test postures of Test Cases 9 and 12, it can be ensured that the energy intensity of the electromagnetic beam of the NFC antenna coil perpendicular to the test terminal in these two states can reach the detection standard for sensing at the specified distance, thus meeting the test requirements of the E and S test points (corresponding to Test Cases 9 and 12).

[0019] As a preferred embodiment, the first coil further includes a first central branch connected to the first coil loop, the first central branch being disposed between the first loop branch and the third loop branch; or, the first central branch being disposed between the second loop branch and the fourth loop branch.

[0020] In the above technical solution, a structural design is provided to realize that there is a horizontal magnetic field component in the middle region of the coil loop and that the magnetic field strength of the two loop branches is greater than that of the other two loop branches on the opposite side. Specifically, a first middle branch is set between any two opposite loop branches, and the first middle branch and the coil loop composed of the four loop branches form a current loop.

[0021] As a preferred embodiment, the number of the first central branch is greater than or equal to two, and the current direction of each of the first central branch is the same.

[0022] In the above technical solution, the magnetic field generated after the first middle branch is energized can be superimposed with the magnetic field generated after the loop branch on one side is energized, thereby strengthening the magnetic field strength on that side, which corresponds to point E or point S in the test case; while it partially cancels out the magnetic field strength on the other side of the loop branch, thereby partially weakening the magnetic field strength on that side, which corresponds to point W or point N in the test case. Since the overlap area between the test terminal and the W and N test points is large during the test, even if the magnetic field strength of the W and N test points is weakened or lower than that of the E and S test points, the magnetic field strength of these two test points can still meet the detection standard sensed by the tested terminal and satisfy the test requirements of the W and N test points (corresponding to Test Cases 5 and 11).

[0023] As a preferred embodiment, the third and fourth loop branches include branches in the same direction, and the first and second loop branches include branches in the same direction and branches in opposite directions; or, the first and second loop branches include branches in the same direction, and the third and fourth loop branches include branches in the same direction and branches in opposite directions. Wherein, the current direction of the branches in the same direction is the same as that of the first central loop branch, and the current direction of the branches in opposite directions is opposite to that of the first central loop branch.

[0024] The above technical solution provides a structural design method for adding a first central stub to a conventional toroidal coil. The principle is that when adding a first central stub or increasing the number of first central stubs to enhance the central current intensity, in order to ensure the overall winding return path of the first coil, return lines for both unidirectional and reverse currents must be set in the first coil loop.

[0025] Specifically, since the overlap area between the W and N test points and the NFC antenna coil of the test terminal is relatively large and the magnetic field strength requirement is relatively low, the reverse current of the W and N test points can be increased (that is, the reverse stub is set at the W and N test points), and the same-direction current of the S and E test points can be increased (that is, the same-direction stub is set at the S and E test points). Ultimately, this will increase the horizontal magnetic field component of the C test point and enhance the magnetic field strength of the S and E test points.

[0026] As a preferred embodiment, for every 2n increase in the number of the first central branch, the number of the first coil loop increases by n. Here, n is a positive integer greater than or equal to 1.

[0027] In the above technical solution, considering the winding return path of the first coil, increasing the number of the first central branch requires simultaneously increasing the current intensity of the loop branches. Since the current flowing through each branch is the same, the number of branches can characterize the current intensity. Therefore, whenever the number of the first central branch increases by an even number, the number of loop branches around it increases by half that number, which means the number of coil loops increases by half that number of turns.

[0028] As a preferred embodiment, for any first loop branch, second loop branch, third loop branch, or fourth loop branch that simultaneously includes both the same-direction branches and the opposite-direction branches, the number of opposite-direction branches is two or more times less than the number of same-direction branches.

[0029] In the above technical solution, even if the magnetic field strength requirements for the W and N test points are relatively low, the number of reverse stubs at the corresponding points cannot be too large, otherwise the test requirements cannot be met. Therefore, for any loop stub that includes both unidirectional and reverse stubs, the number of reverse stubs carrying reverse current should be two or more fewer than the number of unidirectional stubs carrying forward current.

[0030] As a preferred embodiment, the first central branch is located in the middle of the first ring branch and the third ring branch, and is arranged parallel to both of them; or, the first central branch is located in the middle of the second ring branch and the fourth ring branch, and is arranged parallel to both of them.

[0031] In the above technical solution, the first central branch is positioned centrally or offset to one side of the loop branch, and is parallel to the loop branches on both sides. In this design, the magnetic field generated by the first central branch after energization can superimpose with the magnetic field generated by the loop branch on one side after energization. Because they are parallel, the vector directions of their magnetic fields remain consistent and overlap at a specific point, reinforcing each other and maximizing the magnetic field enhancement effect. Furthermore, by centrally positioning the first central branch, the magnetic field generated by it will not excessively cancel out the magnetic field generated by the loop branch on the other side after energization, thus avoiding excessive weakening of the magnetic field on that side.

[0032] As a preferred embodiment, the vehicle-mounted NFC antenna further includes a second coil disposed on the second side. The second coil includes a second coil loop forming a rectangle and a second central branch disposed in the middle of the second coil loop. The second central branch intersects with the first central branch; or, the second central branch is parallel to the first central branch.

[0033] In the above technical solution, the vehicle-mounted NFC antenna includes a first coil and a second coil, which are respectively located on the front and back sides of the substrate. Through the aforementioned double-layer routing design, the intersecting first and second central branch sections can achieve magnetic field interference in four directions on the upper and lower coil loops. This eliminates the dependence of the vehicle-mounted NFC antenna's testing direction on a specific orientation, allowing control of the magnetic field strength at different test points by controlling only the current direction. During testing, regardless of the vehicle-mounted NFC antenna's arrangement, it can meet the Carkey authentication requirements under any condition, without needing to adaptively adjust the orientation of the W, E, N, and S test points based on the magnetic field strength of a specific loop branch, thereby further optimizing subsequent testing and authentication operations. Furthermore, the parallel design of the first and second central branch sections allows for magnetic field superposition, further strengthening the tangential magnetic field strength generated by the two central branch sections.

[0034] As a preferred embodiment, the second coil is connected to the first coil, and the current flows in the first coil and the second coil in the same direction, so that the magnetic flux generated by the current through the first coil is superimposed with the magnetic flux generated by the current through the second coil.

[0035] In the above technical solution, the second coil and the first coil can share a common feed terminal. This coil winding method enables electromagnetic coupling between the two coils, achieving magnetic flux superposition. When current flows through the first and second coils, due to their winding directions, currents in the same direction are generated in both coils. This enhances the electromagnetic coupling effect between the two coils, resulting in better energy transfer.

[0036] As a preferred embodiment, the second coil loop is arranged parallel to the first coil loop; the second central branch is arranged perpendicular to the first central branch.

[0037] In the above technical solution, by arranging the first and second coil loops parallel to each other, their winding trajectories on the plane of the substrate can overlap, enhancing the electromagnetic coupling effect between the two coils and achieving higher energy transfer efficiency. By arranging the first and second central branches perpendicular to each other and centered, the magnetic field generated by the energized central branches can be evenly distributed within the magnetic field generated by their respective coils, avoiding excessive enhancement or weakening of the effect on any one side of the coil loop. Simultaneously, the overall magnetic field environment can be optimized, reducing signal interference and communication instability caused by magnetic field inhomogeneity, and improving the accuracy and reliability of CarKey authentication.

[0038] In summary, this invention, based on traditional NFC antenna design, ensures that the magnetic field strength in the region where two adjacent loop stubs are located is greater than the magnetic field strength in the other two loop stubs on opposite sides. Compared with existing traditional NFC antennas, it has at least the following technical advantages:

[0039] 1) The central region of the coil loop has a significant horizontal magnetic field component. The magnetic field energy can be obtained by the NFC antenna of the test terminal under any test terminal vertical card swiping posture, thus meeting the test requirements of point C (corresponding to Test Case 5).

[0040] 2) Compared with the uniform magnetic field distribution of traditional NFC antennas, this utility model has at least two loop branches with stronger magnetic fields, corresponding to the E and S test points of Carkey certification. Since the magnetic field strength of these two points is greater, when using the test postures of Test Case 9 and 12, it can ensure that the energy intensity of the electromagnetic beam perpendicular to the test terminal in these two states can reach the detection standard of the tested terminal at a specified distance (e.g., 40mm), thereby meeting the test requirements of the E and S test points (corresponding to Test Case 9 and 12).

[0041] 3) Due to the large overlap between the test terminal and the W and N test points, even if the magnetic field strength of the W and N test points is weakened or lower than that of the E and S test points, the magnetic field strength of these two test points can still meet the detection standard sensed by the tested terminal, satisfying the test requirements of the W and N test points (corresponding to Test Cases 5 and 11). Therefore, the NFC antenna design of this utility model can meet all test case requirements for Apple CarKey certification, eliminating the need for deviation certification (downgraded certification) and improving the user experience. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the test plane for an NFC antenna.

[0043] Figure 2 A table of 13 test cases for Carkey certification;

[0044] Figure 3 This is a schematic diagram of the structure of a traditional NFC antenna (including 5 test points).

[0045] Figure 4 The magnetic field distribution diagram of a traditional NFC antenna at the XoZ and YoZ interfaces;

[0046] Figure 5 This is a diagram of Test Case 5;

[0047] Figure 6 This is a diagram of Test Case 9;

[0048] Figure 7 This is a diagram of Test Case 12;

[0049] Figure 8 This is a schematic diagram of the structure of the first embodiment of the vehicle-mounted NFC antenna of this utility model;

[0050] Figure 9 This is a magnetic field distribution diagram of the XoZ and YoZ interfaces of the vehicle-mounted NFC antenna of this utility model in the first embodiment;

[0051] Figure 10 This is a schematic diagram of the first side of the second embodiment of the vehicle-mounted NFC antenna of this utility model;

[0052] Figure 11 This is a schematic diagram of the second embodiment of the vehicle-mounted NFC antenna of the present invention on the second side.

[0053] Figure 12 This is a schematic diagram of the structure of the first coil and the second coil in a second embodiment of the vehicle-mounted NFC antenna of this utility model;

[0054] Figure 13 This is a magnetic field distribution diagram of the XoZ and YoZ interfaces of the vehicle-mounted NFC antenna of this utility model in the second embodiment;

[0055] The meanings of the reference numerals in the attached figures are as follows:

[0056] 1. Substrate; 2. First coil; 3. First coil loop; 4. First middle branch; 5. Second coil; 6. Second coil loop; 7. Second middle branch. Detailed Implementation

[0057] To better understand and implement this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0058] In the description of this utility model, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0060] The vehicle-mounted NFC antenna provided by this utility model can be applied to the interior space of car door handles to generate a magnetic field with sufficient strength and coverage. When using the Carkey function of a mobile phone, users only need to bring the mobile phone or other devices close to the door handle area to quickly complete interactive operations such as unlocking and locking.

[0061] Of course, in addition to the application scenario of car door handles, the vehicle-mounted NFC antenna of this utility model can also be installed in other locations in the car, such as the center console and seats, to achieve multi-point authentication in the car and provide users with some advanced functions, such as seat memory and personalized settings, further improving the user experience and the level of intelligence of the car.

[0062] Example 1

[0063] In the first embodiment of this utility model, a structural design scheme for a vehicle-mounted NFC antenna is provided.

[0064] Figure 1 A plan view of the NFC antenna test is shown, where the five points marked W, E, N, S, and C are the test points. Figure 2 The test cases for Apple Carkey certification (Test Case 1~13) are shown, which correspond to the test cases of the test terminal under different test postures (including Landscape and Portrait) and test angles (including 0°, 45° and 90°).

[0065] Traditional NFC antenna design Figure 3 As shown, a multi-turn wound circuit coil loop is used to form a radiating magnetic field. The magnetic field distribution of this NFC antenna at the XoZ and YoZ interfaces is shown below. Figure 4 As shown, the magnetic field at the center is primarily perpendicular to the NFC antenna, with a ring-shaped magnetic field component around the perimeter. This design cannot meet the following test cases:

[0066] 1. For example Figure 5 As shown, the test terminal corresponds to point C and is at a 90° angle to the NFC antenna (corresponding to Test Case 5). Combined with... Figure 4It is known that the magnetic field distribution in the central region where point C is located is perpendicular to the NFC antenna, with virtually no horizontal magnetic field component. Therefore, when the test terminal enters the central radiated magnetic field of the NFC antenna at a 90° angle, the magnetic field energy cannot be obtained by the NFC antenna of the test terminal. This results in the sensing distance at point C being very short, or even undetectable, thus failing to meet the authentication requirements.

[0067] 2. For example Figure 6 As shown, the test terminal on the left corresponds to point E and is at a 45° angle to the NFC antenna (corresponding to Test Case 9). Combined with... Figure 4 It is known that the overlap area between the antenna of the test terminal and the NFC antenna is insufficient. In this state, the magnetic field strength perpendicular to the test terminal is small, and the magnetic field energy is difficult to be obtained by the NFC antenna of the test terminal, which ultimately leads to the failure to meet the certification requirements during the E-point test.

[0068] 3. For example Figure 7 As shown, the test terminal on the right corresponds to point S and is at a 45° angle to the NFC antenna (corresponding to Test Case 12). Combined with... Figure 4 It can be seen that the overlap area between the antenna of the test terminal and the NFC antenna is insufficient. In this state, the magnetic field strength perpendicular to the test terminal is small, and the magnetic field energy is difficult to be obtained by the NFC antenna of the test terminal, which ultimately leads to the failure to meet the certification requirements during the S-point test.

[0069] The root cause of the above defects is that the Apple CarKey authentication method is fixed. Therefore, no matter how the position of the traditional NFC antenna is adjusted, the structural design of the conventional antenna will inevitably result in three test cases that cannot meet the authentication requirements (Test Cases 5 / 9 / 12). This is an inherent defect in the traditional antenna structural design.

[0070] Based on this, the present invention provides an embodiment of an in-vehicle NFC antenna that can be applied to the interior space of a car door handle to generate a magnetic field of sufficient strength and coverage. When using the Carkey function on a mobile phone, the user only needs to bring the mobile phone or other device close to the door handle area to quickly complete interactive operations such as unlocking and locking.

[0071] See Figure 8 As shown, in the technical solution of this embodiment, the vehicle-mounted NFC antenna includes a substrate 1 and a first coil 2. The substrate 1 includes a first side surface, and the first coil 2 is disposed on the first side surface. The first coil 2 includes a first coil loop 3 that is rectangularly surrounded. The first coil loop 3 includes a first loop branch, a second loop branch, a third loop branch, and a fourth loop branch that are connected in sequence. The first loop branch and the third loop branch are arranged opposite each other (that is, they are arranged on opposite sides), and the second loop branch and the fourth loop branch are arranged opposite each other.

[0072] See Figure 9 As shown, the central region of the first coil loop 3 (corresponding to test point C) has a magnetic field component parallel to the substrate, meaning that the magnetic field generated by the first coil 2 when energized has a horizontal vector in this central region. Therefore, when the test terminal (e.g., a mobile phone) enters the magnetic field in any vertical card-swiping posture, a horizontal magnetic field component will pass through the NFC antenna coil of the test terminal, enabling the NFC antenna of the test terminal to obtain sufficient magnetic field energy, thereby meeting the test requirements of point C (corresponding to Test Case 5).

[0073] It is worth mentioning that the central region described in this utility model is the central region of the vehicle NFC antenna and its adjacent region. When applied to the Apple CarKey authentication test scenario, it corresponds to the region where the C test point is located.

[0074] See Figure 9 As shown, the magnetic field strength of the third loop stub is greater than that of the first loop stub, and the magnetic field strength of the fourth loop stub is greater than that of the second loop stub. Alternatively, the magnetic field strength of the first loop stub is greater than that of the third loop stub, and the magnetic field strength of the second loop stub is greater than that of the fourth loop stub. The purpose of this design is that, between the relatively positioned first and third loop stubs, and between the relatively positioned second and fourth loop stubs, there must be two loop stubs whose regions have a greater magnetic field strength than the other two loop stubs, and the loop stub with the stronger magnetic field corresponds to the E and S test points.

[0075] For example, taking the statement that "the magnetic field strength of the third loop stub is greater than that of the first loop stub, and the magnetic field strength of the fourth loop stub is greater than that of the second loop stub" as an example, the third and fourth loop stubs correspond to test point E and test point S, respectively. When performing test cases 9 and 12, it can be ensured that the energy intensity of the electromagnetic beam of the NFC antenna coil perpendicular to the test terminal in these two states can reach the detection standard at the specified distance (e.g., 40mm), thus meeting the test requirements of test points E and S (corresponding to Test Cases 9 and 12). Therefore, the vehicle-mounted NFC antenna design of this utility model can meet all test case requirements for Carkey certification, eliminating the need for deviation certification (downgraded certification) and improving the user experience.

[0076] See Figure 8As shown, in a preferred embodiment, the first coil 2 further includes a first central branch 4 connected to the first coil loop 3. The first central branch 44 is located between the first loop branch and the third loop branch, and its two ends are connected to the second loop branch and the fourth loop branch, respectively; or, the first central branch is located between the second loop branch and the fourth loop branch, and its two ends are connected to the first loop branch and the third loop branch, respectively.

[0077] The above-mentioned preferred embodiment provides a structural design that enables the presence of a horizontal magnetic field component in the middle region of the first coil loop 3 and the magnetic field strength of two loop stubs therein to be greater than that of the other two loop stubs on the opposite side. Specifically, a first middle loop stub is set between any two opposite loop stubs, and the first middle loop stub, together with the coil loop composed of the first loop stub, the second loop stub, the third loop stub, and the fourth loop stub, forms a current loop.

[0078] Specifically, the location of the first central branch is determined by a combination of factors, including the orientation of the E and S test points during certification and the direction of the current flow. For example, if the locations of the third and fourth ring branches are used as E and S test points, the first central branch can be located between the second and fourth ring branches; if the locations of the first and second ring branches are used as E and S test points, the first central branch can be located between the first and third ring branches.

[0079] See Figure 8 As shown, in a preferred embodiment, the number of first central branch 4 is greater than or equal to two, and the current direction of each first central branch 4 is the same, so that the magnetic fields generated after all the first central branch 4 are energized are superimposed in the same direction.

[0080] In this preferred embodiment, the purpose of setting multiple first central branch segments 4 with currents in the same direction is that the magnetic field generated by the first central branch segment 4 after being energized can be superimposed with the magnetic field generated by the loop branch located on one side of it after being energized, thereby strengthening the magnetic field strength in that side region, which corresponds to test point E or test point S in the test case. At the same time, the magnetic field generated by the first central branch segment 4 will partially cancel out the magnetic field strength of the loop branch on the other side, thereby partially weakening the magnetic field strength in that side region, which corresponds to test point W or test point N in the test case. Since the overlap area between the test terminal and the W and N test points is large during testing, even if the magnetic field strength of the W and N test points is weakened or lower than that of the E and S test points, the magnetic field strength of these two test points can still meet the detection standard sensed by the tested terminal, satisfying the test requirements of the W and N test points (corresponding to Test Cases 5 and 11).

[0081] Therefore, the current directions of the first central branch 4 must be the same; otherwise, the magnetic field generated by the first central branch 4 itself will cancel each other out. Furthermore, by increasing the number of first central branches 4 with current in the same direction, the magnetic field strength in the region where point E or point S is located can be further increased.

[0082] In one optional embodiment, if the third and fourth loop branches correspond to the E and S test points during certification testing, then the third and fourth loop branches include branches in the same direction, and the first and second loop branches include branches in the same direction and branches in opposite directions. Specifically, the current direction of the branches in the same direction is the same as the current direction of the first middle loop branch 4, and the current direction of the branches in opposite directions is opposite to the current direction of the first middle loop branch 4.

[0083] In another optional embodiment, if the first loop branch and the second loop branch correspond to the E and S test points during the certification test, then the first loop branch and the second loop branch include branches in the same direction, and the third loop branch and the fourth loop branch include branches in the same direction and branches in opposite directions.

[0084] In essence, both of the above-mentioned alternative solutions provide a structural design method for adding a first central stub 4 to a traditional toroidal coil. The principle is that, in the process of adding the first central stub 4 from the toroidal coil or increasing the number of first central stubs 4 to enhance the central current intensity, to ensure the overall winding return path of the first coil 2, return lines for both unidirectional and reverse currents must be added to the first coil loop 3. In this solution, the added reverse current return line is located at the first loop stub and the second loop stub.

[0085] Specifically, since the overlap area between the W and N test points and the NFC antenna coil of the test terminal is large, the requirement for magnetic field strength is relatively low. The reverse current of the W and N test points can be increased (that is, the added reverse stub is set in the loop stub where the W and N test points are located), and the same-direction current of the S and E test points can be increased (that is, the added same-direction stub is set in the S and E test points). Ultimately, the loop stub where the W and N test points are located includes both same-direction and reverse stubs, while the loop stub where the S and E test points are located only includes same-direction stubs. This increases the horizontal magnetic field component of the C test point and enhances the magnetic field strength of the S and E test points.

[0086] In one alternative embodiment, for every 2n increase in the number of the first central branch 4, the number of the first coil loop 3 increases by n. Here, n is a positive integer greater than or equal to 1.

[0087] Specifically, considering the winding return path of the first coil 2, increasing the number of first central stubs 4 requires simultaneously increasing the current intensity of the first coil loop 3. Since the current flowing through each of the first central stubs 4 is the same, the number of stubs can characterize the current intensity. Therefore, whenever the number of first central stubs 4 increases by an even number, the number of loop stubs around them increases by half that number, meaning the number of coil loops increases by half that number of turns.

[0088] Preferably, if the number of the first middle branch 4 is 2, then the number of windings in the first coil loop 3 increases by 1.

[0089] More preferably, if the number of the first central branch 4 is 4, then the number of windings in the first coil loop 3 increases by 2.

[0090] In another alternative embodiment, for any first loop stub, second loop stub, third loop stub, or fourth loop stub that simultaneously includes both stubs in the same direction and stubs in opposite directions (i.e., a switching stub containing reverse current), the number of reverse stubs must be two or more times less than the number of stubs in the same direction. The purpose of this design is:

[0091] During certification testing, even if the W and N test points have low requirements for magnetic field strength, an excessive number of reverse stubs at these points can lead to an insufficiently weak magnetic field. This can result in the test requirements not being met even when the magnetic field overlaps significantly with the NFC antenna coil of the test terminal. Therefore, for any loop stub that includes both unidirectional and reverse stubs, the number of reverse stubs carrying reverse current must be two or more fewer than the number of unidirectional stubs carrying forward current.

[0092] See Figure 8 As shown, in an optional embodiment, the first central branch 4 is located in the middle of the first ring branch and the third ring branch, and is arranged parallel to the first ring branch and the third ring branch, and is connected to the second ring branch and the fourth ring branch.

[0093] Specifically, the first central branch 4 is centrally located and parallel to the first and third loop branches on either side. In this design, the magnetic field generated by the first central branch 4 after energization can superimpose with the magnetic field generated by one of the loop branches (e.g., the third loop branch) after energization. Furthermore, because the first central branch 4 and the third loop branch are parallel, their magnetic field vectors remain consistent and overlap at specific points, reinforcing each other and maximizing the magnetic field enhancement effect. Moreover, centrally located, the magnetic field generated by the first central branch 4 does not excessively cancel out the magnetic field generated by the loop branch (e.g., the first loop branch) on the other side, thus avoiding excessive weakening of the magnetic field on that side.

[0094] See Figure 8 As shown, in another optional embodiment, the first central branch 4 is located in the middle of the second ring branch and the fourth ring branch, and is arranged parallel to the second ring branch and the fourth ring branch, and is connected to the first ring branch and the third ring branch.

[0095] Specifically, the first central branch 4 is centrally located and parallel to the second and fourth ring branches on either side. In this design, the magnetic field generated by the first central branch 4 after energization can superimpose with the magnetic field generated by one of the ring branches (e.g., the fourth ring branch) after energization. Furthermore, because the first central branch 4 and the fourth ring branch are parallel, their magnetic field vectors remain consistent and overlap at specific points, reinforcing each other and maximizing the magnetic field enhancement effect. Moreover, centrally located, the magnetic field generated by the first central branch 4 does not excessively cancel out the magnetic field generated by the ring branch on the other side (e.g., the second ring branch), thus avoiding excessive weakening of the magnetic field on that side.

[0096] Example 2

[0097] In a second embodiment of this utility model, another structural design scheme for an in-vehicle NFC antenna is provided.

[0098] See Figure 10-12 As shown, in this embodiment, the vehicle-mounted NFC antenna includes a substrate 1, a first coil 2, and a second coil 5. The substrate 1 includes a first side and a second side disposed opposite to each other. The first coil 2 is disposed on the first side, and the second coil 5 is disposed on the second side. The first coil 2 includes a first coil loop 3 arranged in a rectangle, and the second coil 5 includes a second coil loop 6 arranged in a rectangle. The first coil loop 3 includes four loop branches (i.e., the first loop branch, second loop branch, third loop branch, and fourth loop branch described in Embodiment 1), and correspondingly, the second coil loop 6 also includes four loop branches. A second central branch 7 is provided in the middle portion 6 of the second coil loop, and the second central branch 7 intersects with the first central branch 4; or, the second central branch 7 and the first central branch 4 are arranged parallel to each other.

[0099] See Figure 13As shown, based on the structural design of the first central branch 4 and the second central branch 7, the central region of the first coil loop 3 and the second coil loop 6 has a magnetic field component parallel to the substrate 1. That is, the magnetic field generated by the energization of the first coil 2 and the second coil 5 has a horizontal vector in the horizontal direction in this central region. Therefore, when the test terminal (e.g., a mobile phone) enters the magnetic field in any vertical card-swiping posture, a horizontal magnetic field component will pass through the NFC antenna coil of the test terminal, enabling the NFC antenna of the test terminal to obtain sufficient magnetic field energy, thereby meeting the test requirements of point C (corresponding to Test Case 5).

[0100] See Figure 13 As shown, based on the structural design of the first central branch 4 and the second central branch 7, in the first coil loop 3, between the relatively opposite first and third loop branches, and between the relatively opposite second and fourth loop branches, there must be two loop branches whose regions have a greater magnetic field strength than the other two loop branches. Similarly, in the second coil loop 6, there are also two loop branches whose regions have a greater magnetic field strength than the other two loop branches. Furthermore, by designing the first central branch 4 and the second central branch 7 as parallel entities, magnetic field superposition can be achieved, further strengthening the tangential magnetic field strength generated by the two central branches.

[0101] Compared to the uniform magnetic field distribution of traditional NFC antennas, the above design features two loop stubs with stronger magnetic fields, corresponding to the E and S test points for Carkey certification. Due to the greater magnetic field strength at these two points, when using the test postures of Test Case 9 and 12, it can be ensured that the energy intensity of the electromagnetic beam perpendicular to the test terminal in these two states can reach the detection standard of the tested terminal at a specified distance (e.g., 40mm), thus meeting the test requirements of the E and S test points (corresponding to Test Case 9 and 12).

[0102] Furthermore, in this embodiment, the vehicle-mounted NFC antenna employs a double-layer routing method, allowing the intersecting first central branch 4 and second central branch 7 to interfere with the magnetic fields of the first coil loop 3 and the second coil loop 6 in four directions. This design aims to eliminate the dependence of the vehicle-mounted NFC antenna's testing direction on a specific orientation, thus enabling control of the magnetic field strength at different test points by simply controlling the current direction. During testing, regardless of the vehicle-mounted NFC antenna's arrangement, it can meet the Carkey authentication requirements in any state, without needing to adaptively adjust the orientation of the W, E, N, and S test points based on the magnetic field strength of a specific loop branch, thereby further optimizing subsequent testing and authentication operations.

[0103] More specifically, the above design simplifies the testing and certification process for automotive NFC antennas, reduces testing complexity and cost, and improves testing efficiency and accuracy, ensuring that automotive NFC antennas can quickly and accurately pass Carkey certification under various conditions. Furthermore, it eliminates the need for frequent adjustments to the NFC antenna layout across different vehicle models and usage environments, guaranteeing good certification results. This allows automotive NFC antennas to better adapt to various complex environments, improving system reliability and stability, and providing users with a more convenient and stable user experience.

[0104] See Figure 12 As shown, in a preferred embodiment, the second coil 5 is connected to the first coil 2 to form a complete current loop. Specifically, the second coil 5 and the first coil 2 can share a common feed terminal, thereby aligning the current flow directions of the first coil 2 and the second coil 5.

[0105] Through the above design, the magnetic flux generated by the current flowing through the first coil 2 can be coupled with the magnetic flux generated by the current flowing through the second coil 5, thereby achieving electromagnetic coupling between the two coils and superimposing the magnetic flux. When current flows through the first coil 2 and the second coil 5, due to their winding directions, currents in the same direction will be generated in both coils. This enhances the electromagnetic coupling effect between the two coils, resulting in better energy transfer.

[0106] See Figure 12 As shown, in a preferred embodiment, the second coil loop 6 and the first coil loop 3 are arranged parallel to each other, so that the winding trajectories of the two coil loops on the plane of the substrate 1 coincide, thereby enhancing the electromagnetic coupling effect between the first coil 2 and the second coil 5 and achieving higher energy transmission efficiency.

[0107] Furthermore, the second central branch 7 and the first central branch 4 are perpendicular to each other and centrally located within their respective coil loops. This ensures that the magnetic fields generated by the energized second central branch 7 and the first central branch 4 are evenly distributed within the magnetic fields generated by their respective coils, preventing excessive enhancement or weakening effects on any one side of the coil loop. Simultaneously, this design optimizes the overall magnetic field environment of the NFC antenna, reducing signal interference and communication instability caused by magnetic field inhomogeneity, and improving the accuracy and reliability of CarKey authentication.

[0108] Of course, the second embodiment of this utility model is an improvement on the first embodiment. The technical features not described in detail in this embodiment (such as the number and current direction of the second central branch 7, the structural design of the four loop branches of the second coil loop 6, etc.) are the same as the first central branch 4 and the first coil loop 3 in the first embodiment, and will not be described again in this embodiment.

[0109] The technical means disclosed in this utility model are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications are also considered within the scope of protection of this utility model.

Claims

1. A vehicle-mounted NFC antenna, characterized by, include: A substrate, the substrate including a first side surface and a second side surface disposed opposite to each other; A first coil is disposed on the first side. The first coil includes a first coil loop that is rectangularly encircled. The first coil loop includes a first loop branch, a second loop branch, a third loop branch, and a fourth loop branch. The first loop branch and the third loop branch are arranged opposite to each other, and the second loop branch and the fourth loop branch are arranged opposite to each other. The central region of the first coil loop has a magnetic field component parallel to the substrate. Furthermore, the magnetic field strength of the third loop stub is greater than that of the first loop stub, and the magnetic field strength of the fourth loop stub is greater than that of the second loop stub; or, the magnetic field strength of the first loop stub is greater than that of the third loop stub, and the magnetic field strength of the second loop stub is greater than that of the fourth loop stub.

2. The in-vehicle NFC antenna according to claim 1, characterized by The first coil further includes a first central branch connected to the first coil loop, the first central branch being located between the first loop branch and the third loop branch; or, the first central branch being located between the second loop branch and the fourth loop branch.

3. The vehicle-mounted NFC antenna according to claim 2, characterized in that, The number of the first central branch is greater than or equal to two, and the current direction of each of the first central branches is the same.

4. The vehicle-mounted NFC antenna according to claim 3, characterized in that, The third and fourth loop branches include branches in the same direction, and the first and second loop branches include branches in the same direction and branches in opposite directions; or, the first and second loop branches include branches in the same direction, and the third and fourth loop branches include branches in the same direction and branches in opposite directions. Wherein, the current direction of the same-direction branch is the same as that of the first central branch, and the current direction of the opposite-direction branch is opposite to that of the first central branch.

5. The vehicle-mounted NFC antenna according to claim 4, characterized in that, For every 2n increase in the number of the first central branch, the number of the first coil loop increases by n; where n is a positive integer greater than or equal to 1.

6. The vehicle-mounted NFC antenna according to claim 4, characterized in that, For any first loop branch, second loop branch, third loop branch, or fourth loop branch that simultaneously includes both the same-direction branches and the opposite-direction branches, the number of opposite-direction branches is two or more times less than the number of same-direction branches.

7. The vehicle-mounted NFC antenna according to claim 2, characterized in that, The first central branch is located in the middle of the first ring branch and the third ring branch, and is arranged parallel to both of them; or, the first central branch is located in the middle of the second ring branch and the fourth ring branch, and is arranged parallel to both of them.

8. The vehicle-mounted NFC antenna according to any one of claims 2-7, characterized in that, The vehicle-mounted NFC antenna also includes a second coil, which is disposed on the second side. The second coil includes a second coil loop that is rectangularly surrounded and a second central branch disposed in the middle of the second coil loop. The second central branch is arranged to intersect with the first central branch; or the second central branch is arranged to be parallel to the first central branch.

9. The vehicle-mounted NFC antenna according to claim 8, characterized in that, The second coil is connected to the first coil, and the current flows in the same direction in both coils, so that the magnetic flux generated by the current through the first coil is superimposed on the magnetic flux generated by the current through the second coil.

10. The vehicle-mounted NFC antenna according to claim 8, characterized in that, The second coil loop is arranged parallel to the first coil loop; the second middle branch is arranged perpendicular to the first middle branch.

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