Vehicle-mounted NFC antenna

Abstract

A vehicle-mounted NFC antenna disclosed by the present invention comprises a substrate and at least one coil, one coil is arranged on a first side surface of the substrate, the coil comprises a coil loop and a middle branch knot which are in a rectangular surrounding shape, and the coil loop comprises four loop branch knots. Wherein the central area (corresponding to the test point C) of the coil loop has a magnetic field component parallel to the substrate, and the magnetic field energy can be acquired by the NFC antenna of the test terminal by adopting a vertical card swiping posture of the test terminal under any condition. Moreover, compared with the uniform magnetic field distribution of the traditional antenna, the antenna provided by the invention has at least two loop branches (corresponding to test points E and S) with stronger magnetic fields, and when a test case which cannot be met by the original traditional antenna is carried out, the energy intensity of an electromagnetic beam vertical to a test terminal in the two states can reach an induction detection standard of a specified distance. In conclusion, a traditional antenna is improved, so that the special test point position meets the test requirement, a deviation authentication (degradation authentication) mode does not need to be adopted, and the use requirement of a user is met.

Description

Technical Field

[0001] The present invention relates to the technical field of short-range communication antennas, and in particular to a vehicle-mounted NFC antenna. Background Art

[0002] NFC, or Near Field Communication, is a short-range, high-frequency wireless communication technology that allows devices using it to exchange data when in close proximity. In the automotive industry, NFC is the first generation of digital keys. Apple, using NFC as a digital key, has established authentication requirements for card swiping distance and gesture.

[0003] Traditional NFC antenna design Figure 3 As shown in the figure, a multi-turn circuit coil loop is used to form a radiated magnetic field. The magnetic field distribution of the NFC antenna at the XoZ interface and the YoZ interface is shown in the figure. Figure 4 As shown, the magnetic field at the center is mainly perpendicular to the NFC antenna, and there are circular magnetic field components around it. This design cannot meet the following test cases for Apple CarKey certification: 1. If Figure 5 , 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 entering, and the sensing distance is short or even no sensing occurs.

[0004] 2. Figure 6 In the example, the terminal is at a 45° angle to the antenna at point E (corresponding to Test Case 9). The antenna overlap area is insufficient, the magnetic field strength is weak, and it is difficult to obtain energy.

[0005] 3. Figure 7 The display shows that the terminal is at a 45-degree angle to the antenna at point S (corresponding to Test Case 12). Similarly, it fails to meet the certification requirements.

[0006] 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 (Test Case 5 / 9 / 12) failing to meet the authentication requirements. This is a natural defect in the traditional antenna structure design.

[0007] Of course, the issues with multi-turn coil loop designs aren't limited to Apple CarKey authentication testing; they also arise in Android NFC authentication testing. A common approach in existing technology is to employ deviated authentication (authentication downgrade) at these three test points.

[0008] Furthermore, the multi-turn circuit coil design can cause significant inconvenience in daily use when used in the manner described in Test Cases 5 / 9 / 12. Due to the insufficient antenna overlap and low magnetic field strength, the terminal struggles to capture the magnetic field energy, resulting in poor device sensitivity. This often requires repeated adjustments to the terminal's angle and position when near the NFC antenna, requiring multiple attempts to successfully complete operations such as unlocking a door. This significantly impacts user experience and creates inconvenience.

[0009] Based on this, it is necessary to improve the structural design of traditional NFC antennas. Summary of the Invention

[0010] In order to overcome the technical problem that the traditional NFC antenna described in the above-mentioned prior art cannot pass at least three test cases, the present invention provides a vehicle-mounted NFC antenna. By improving the antenna structure design, the vehicle-mounted NFC antenna can pass all the above-mentioned test cases, meet the Apple CarKey certification requirements without adopting deviation certification (certification downgrade), and improve the user experience.

[0011] The technical solution adopted by the present invention to solve the problem is: A vehicle-mounted NFC antenna, comprising: a substrate, the substrate comprising a first side surface and a second side surface disposed opposite to each other; A first coil, the first coil is arranged on the first side, the first coil includes a first coil loop surrounded by a rectangle, 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.

[0012] 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 branch is greater than that of the first loop branch, and the magnetic field strength of the fourth loop branch is greater than that of the second loop branch; alternatively, the magnetic field strength of the first loop branch is greater than that of the third loop branch, and the magnetic field strength of the second loop branch is greater than that of the fourth loop branch.

[0013] In this technical solution, the central region of the first coil loop has a magnetic field component parallel to the substrate. This means that the magnetic field generated by the first coil when energized has a horizontal vector in this central region. Therefore, when the test terminal enters the magnetic field using any vertical card swiping posture, a horizontal magnetic field component will pass through the test terminal's NFC antenna coil, ensuring that the test terminal's NFC antenna receives sufficient magnetic field energy to meet the test requirements of point C (corresponding to Test Case 5).

[0014] Furthermore, between the first and third loop branches, and between the second and fourth loop branches, two of the branches must have a stronger magnetic field strength than the other two. The loop branches with the stronger magnetic field correspond to test points E and S. Therefore, when using the test postures of Test Cases 9 and 12, the energy intensity of the electromagnetic wave beam perpendicular to the NFC antenna coil of the test terminal in these two states can be guaranteed to meet the detection standard for induction at the specified distance, thereby meeting the test requirements of test points E and S (corresponding to Test Cases 9 and 12).

[0015] As a preferred embodiment, the first coil also includes a first middle branch node connected to the first coil loop, and the first middle branch node is arranged between the first loop branch node and the third loop branch node; or, the first middle branch node is arranged between the second loop branch node and the fourth loop branch node.

[0016] In the above technical solution, a structural design method is provided to achieve the existence of a horizontal magnetic field component in the middle area of ​​the coil loop and 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 coil loop composed of the first middle branch and the four loop branches constitutes a current loop.

[0017] As a preferred solution, the number of the first mid-circuit branches is greater than or equal to two, and the current directions of the first mid-circuit branches are the same.

[0018] In the above technical solution, the magnetic field generated by the first middle branch after power is applied to the loop branch on one side can be superimposed with the magnetic field generated by power application on the loop branch on one side, thereby strengthening the magnetic field strength on that side, which corresponds to point E or point S in the test case; and partially offset by the loop branch on the other side, thereby partially weakening the magnetic field strength on that side, which corresponds to point W or point N in the test case. Since the overlapping 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 the magnetic field strength of the W and N test points is 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 meet the test requirements of the W and N test points (corresponding to Test Cases 5 and 11).

[0019] As a preferred embodiment, the third loop branch and the fourth loop branch include unidirectional branches, and the first loop branch and the second loop branch include unidirectional branches and counter-directional branches; or the first loop branch and the second loop branch include unidirectional branches, and the third loop branch and the fourth loop branch include unidirectional branches and counter-directional branches. The current direction of the unidirectional branches is the same as that of the first mid-circuit branches, and the current direction of the counter-directional branches is opposite to that of the first mid-circuit branches.

[0020] The above technical solution provides a structural design method for adding a first central branch to a conventional toroidal coil. The principle is that when adding a first central branch or increasing the number of first central branches to enhance the current intensity in the central portion, return lines for both unidirectional and reverse currents must be provided within the first coil loop to ensure a consistent winding return path for the entire first coil.

[0021] Specifically: Since the W and N test points have a large overlapping area with the NFC antenna coil of the test terminal and have a low requirement for magnetic field strength, the reverse current of the W and N test points can be increased (that is, reverse branches are set at the W and N test points), and the unidirectional current of the S and E test points can be increased (that is, unidirectional branches are set at the S and E test points). Ultimately, the horizontal magnetic field component of the C test point can be increased, and the magnetic field strength of the S and E test points can be enhanced.

[0022] As a preferred solution, every time the number of the first mid-circuit branches increases by 2n, the number of the first coil loops increases by n, where n is a positive integer greater than or equal to 1.

[0023] In the above technical solution, considering the winding return path of the first coil, increasing the number of first central branches requires simultaneously increasing the current intensity of the loop branches. If the current flowing through each branch is the same, the number of branches can be used to represent the current intensity. Therefore, whenever the number of first central branches increases by an even number, the number of surrounding loop branches increases by half that number, meaning the number of coil loops increases by half that number.

[0024] As a preferred solution, for any one of the first loop branch, the second loop branch, the third loop branch or the fourth loop branch that includes both the same-direction branches and the reverse branches, the number of the reverse branches is two or more less than the number of the same-direction branches.

[0025] 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 branches at the corresponding points cannot be too large, otherwise the test requirements will not be met. Therefore, for any loop branch that includes both unidirectional branches and reverse branches, the number of reverse branches with reverse current must be two or more less than the number of unidirectional branches with forward current.

[0026] As a preferred embodiment, the first middle branch node is located in the middle of the first loop branch node and the third loop branch node, and is arranged parallel to the two; or, the first middle branch node is located in the middle of the second loop branch node and the fourth loop branch node, and is arranged parallel to the two.

[0027] In the above technical solution, the first middle branch node is centrally located or biased toward one side of the loop branch node, and is parallel to the loop branches on both sides. Under this design, the magnetic field generated by the first middle branch node after power is applied can be superimposed with the magnetic field generated by the loop branch node on one side after power is applied. Since the two are parallel to each other, the directions of the magnetic field vectors generated by the two can remain consistent and overlap at specific points, reinforcing each other, thereby maximizing the magnetic field enhancement effect. In addition, by arranging the first middle branch node in the center, the magnetic field generated by the first middle branch node will not excessively offset the magnetic field generated by the loop branch node on the other side after power is applied, thereby avoiding excessive weakening of the magnetic field on that side.

[0028] As a preferred embodiment, the in-vehicle NFC antenna further includes a second coil, which is disposed on the second side surface and comprises a rectangular second coil loop and a second middle branch located in the middle of the second coil loop. The second middle branch is arranged to intersect with the first middle branch, or the second middle branch is arranged parallel to the first middle branch.

[0029] In the above technical solution, the on-board NFC antenna includes a first coil and a second coil, which are respectively arranged on the front and back sides of the substrate. Through the above-mentioned double-layer routing design, the mutually intersecting first middle branch and second middle branch can achieve magnetic field interference in four directions of the upper and lower coil loops. The test direction of the on-board NFC antenna is no longer dependent on a specific direction, so that the magnetic field strength of different test points can be controlled by only controlling the current direction. During specific testing, no matter how the on-board NFC antenna is arranged, it can meet the Carkey authentication requirements in any state. There is no need to adaptively adjust the orientation of the W, E, N, and S test points according to the magnetic field strength of the specific loop branch area, thereby further optimizing subsequent test and authentication operations. In addition, by designing the first middle branch and the second middle branch in parallel to each other, magnetic field superposition can be achieved, further strengthening the tangential magnetic field strength generated by the two middle branches.

[0030] As a preferred solution, 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 passing through the first coil is superimposed with the magnetic flux generated by the current passing through the second coil.

[0031] In the above technical solution, the second coil and the first coil can share a feed terminal. This coil winding method can achieve electromagnetic coupling between the two coils, achieving magnetic flux superposition. When current passes through the first and second coils, due to the relationship between their winding directions, currents in the first and second coils flow in the same direction. This enhances the electromagnetic coupling effect between the two coils, thereby achieving better energy transfer.

[0032] As a preferred solution, the second coil loop and the first coil loop are arranged parallel to each other; the second middle branch and the first middle branch are arranged perpendicular to each other.

[0033] 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 transmission efficiency. By arranging the first and second middle branches perpendicularly and centrally, the magnetic fields generated by the two middle branches can be evenly distributed within the magnetic fields generated by their respective coils, avoiding excessive strengthening or weakening of any side branches of the coil loop. At the same time, 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.

[0034] In summary, based on the design of traditional NFC antennas, this invention makes the magnetic field strength in the area where two adjacent loop branches are located greater than the magnetic field strength of the other two loop branches on opposite sides. Compared with traditional NFC antennas in the prior art, this invention has at least the following technical effects: 1) The center area of ​​the coil loop has a significant horizontal magnetic field component. Under any vertical card swiping posture of the test terminal, the magnetic field energy can be obtained by the NFC antenna of the test terminal, thus meeting the test requirements of point C (corresponding to Test Case 5).

[0035] 2) Compared with the uniform magnetic field distribution of traditional NFC antennas, the present invention has at least two loop branches with relatively strong magnetic fields, corresponding to the E and S test points of Carkey certification. Due to the stronger magnetic field strength at these two points, when using the test postures of Test Cases 9 and 12, it can ensure that the energy intensity of the electromagnetic wave beam perpendicular to the test terminal in these two states can meet the detection standard for induction by the tested terminal at a specified distance (for example, 40mm), thereby meeting the test requirements of the E and S test points (corresponding to Test Cases 9 and 12).

[0036] 3) Because the test terminal overlaps significantly with the W and N test points, even if the magnetic field strength at these points is weakened or lower than that at the E and S test points, the magnetic field strength at these two test points still meets the detection standard for sensing by the tested terminal, meeting the test requirements for the W and N test points (corresponding to Test Cases 5 and 11). Therefore, the NFC antenna design of this invention meets all test case requirements for Apple CarKey authentication, eliminating the need for deviated authentication (downgraded authentication) and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the test plane of the NFC antenna; Figure 2 A table of 13 test cases for Carkey certification; Figure 3 This is a schematic diagram of the structure of a traditional NFC antenna (including 5 test points); Figure 4 Magnetic field distribution diagram of traditional NFC antenna at XoZ interface and YoZ interface; Figure 5 This is a schematic diagram of test case Test Case 5; Figure 6 This is a schematic diagram of test case Test Case 9; Figure 7 This is a schematic diagram of test case Test Case 12; Figure 8 This is a schematic structural diagram of a first embodiment of the vehicle-mounted NFC antenna of the present invention; Figure 9 Magnetic field distribution diagram of the XoZ interface and YoZ interface of the vehicle-mounted NFC antenna of the present invention in the first embodiment; Figure 10 This is a schematic diagram of a second embodiment of the vehicle-mounted NFC antenna of the present invention on a first side; Figure 11 This is a schematic diagram of a second side view of a second embodiment of a vehicle-mounted NFC antenna according to the present invention; Figure 12 This is a schematic structural diagram of the first coil and the second coil of the second embodiment of the vehicle-mounted NFC antenna of the present invention; Figure 13 Magnetic field distribution diagrams of the XoZ interface and YoZ interface of the vehicle-mounted NFC antenna of the present invention under the second embodiment; The meanings of the reference numerals are as follows: 1. Baseboard; 2. First coil; 3. First coil loop; 4. First middle branch; 5. Second coil; 6. Second coil loop; 7. Second middle branch. DETAILED DESCRIPTION

[0038] For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0039] In the description of the present invention, it should be noted that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0041] The vehicle-mounted NFC antenna provided by the present invention can be used in the internal space of a car door handle to generate a magnetic field of sufficient strength and coverage. When a user uses the CarKey function of a mobile phone, they only need to bring the mobile phone or other device close to the door handle area to quickly complete interactive operations such as unlocking and locking.

[0042] Of course, in addition to the application scenario of car door handles, the vehicle-mounted NFC antenna of the present invention can also be installed in other locations in the car, such as the center console, seats, etc., 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 intelligence level of the car.

[0043] Example 1 In a first embodiment of the present invention, a structural design solution of a vehicle-mounted NFC antenna is provided.

[0044] Figure 1 A plan view of the NFC antenna test is shown, wherein the five points W, E, N, S, and C marked in the figure are test points. Figure 2 The chart shows 13 test cases (Test Case 1 to 13) for Apple CarKey certification, which correspond to the test cases of the test terminal in different test postures (including Landscape and Portrait) and test angles (including 0°, 45° and 90°).

[0045] Traditional NFC antenna design Figure 3 As shown in the figure, a multi-turn circuit coil loop is used to form a radiated magnetic field. The magnetic field distribution of the NFC antenna at the XoZ interface and the YoZ interface is shown in the figure. Figure 4 As shown in the figure, the magnetic field at the center is mainly perpendicular to the NFC antenna, and there are circular magnetic field components around it. This design cannot meet the following test cases: 1. If Figure 5 As shown in the figure, the test terminal corresponds to point C and is at 90° to the NFC antenna (corresponding to Test Case 5). Figure 4 As can be seen, the magnetic field distribution in the central area at point C 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 captured by the test terminal's NFC antenna. Ultimately, the sensing distance during the test at point C is very short, or even nonexistent, and thus fails to meet certification requirements.

[0046] 2. If 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). Figure 4 It can be seen that the overlapping 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 authentication requirements during the E point test.

[0047] 3. If Figure 7As 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). Figure 4 It can be seen that the overlapping 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 authentication requirements during the S point test.

[0048] The fundamental reason for 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 (Test Case 5 / 9 / 12) failing to meet the authentication requirements. This is a natural defect in the traditional antenna structure design.

[0049] Based on this, the present invention provides an embodiment of a vehicle-mounted NFC antenna, which can be used in the internal space of a car door handle to generate a magnetic field of sufficient strength and coverage. When a user uses the CarKey function of a mobile phone, he or she only needs to place the mobile phone or other device close to the door handle area to quickly complete interactive operations such as unlocking and locking.

[0050] See also 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. The first coil 2 is arranged on the first side surface. The first coil 2 includes a first coil loop 3 that is surrounded in a rectangular shape. 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 to each other (that is, arranged on opposite sides), and the second loop branch and the fourth loop branch are arranged opposite to each other.

[0051] See also Figure 9 As shown, the central region of first coil loop 3 (corresponding to test point C) has a magnetic field component parallel to the substrate. This means that the magnetic field generated by energizing first coil 2 has a horizontal vector in this central region. Therefore, when a test terminal (such as a mobile phone) enters the magnetic field using any vertical card swiping gesture, a horizontal magnetic field component will pass through the test terminal's NFC antenna coil, ensuring that the test terminal's NFC antenna receives sufficient magnetic field energy to meet the test requirements of point C (corresponding to Test Case 5).

[0052] It is worth mentioning that the central area described in the present invention is the center area of ​​the vehicle-mounted NFC antenna and its adjacent area. When applied to the test scenario of Apple Carkey certification, it corresponds to the area where the C test point is located.

[0053] See also Figure 9As shown, the magnetic field strength of the third loop branch is greater than that of the first loop branch, and the magnetic field strength of the fourth loop branch is greater than that of the second loop branch. Alternatively, the magnetic field strength of the first loop branch is greater than that of the third loop branch, and the magnetic field strength of the second loop branch is greater than that of the fourth loop branch. The purpose of the above design is that between the first and third loop branches that are relatively arranged, and between the second and fourth loop branches that are relatively arranged, there must be an area where the magnetic field strength of two of the loop branches is greater than that of the other two loop branches, and the loop branches where the stronger magnetic field is located correspond to the E and S test points.

[0054] For example, taking "the magnetic field strength of the third loop branch is greater than that of the first loop branch, and the magnetic field strength of the fourth loop branch is greater than that of the second loop branch" as an example, the third loop branch and the fourth loop branch correspond to the E test point and the S test point, respectively. When performing the test cases of Test Case 9 and 12, it can be ensured that the energy intensity of the electromagnetic wave beam perpendicular to the NFC antenna coil of the test terminal in these two states can reach the detection standard of induction at a specified distance (such as 40mm), thereby meeting the test requirements of the E and S test points (corresponding to Test Case 9 and 12). Therefore, the vehicle-mounted NFC antenna design of the present invention can meet all test case requirements of Carkey certification, without the need to adopt deviation certification (downgrade certification), and improve the user experience.

[0055] See also Figure 8 As shown, in a preferred embodiment of this embodiment, the first coil 2 further includes a first middle branch 4 connected to the first coil loop 3. The first middle branch 44 is provided between the first loop branch and the third loop branch, with its two ends respectively connected to the second loop branch and the fourth loop branch; alternatively, the first middle branch is provided between the second loop branch and the fourth loop branch, with its two ends respectively connected to the first loop branch and the third loop branch.

[0056] The above-mentioned preferred scheme provides a structural design method that can realize the existence of a horizontal magnetic field component in the middle area of ​​the first coil loop 3 and the magnetic field strength of 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 coil loop composed of the first middle branch and the first loop branch, the second loop branch, the third loop branch, and the fourth loop branch constitutes a current loop.

[0057] Specifically, the location of the first mid-circuit branch is determined based on the orientation of the E and S test points during authentication and the direction of the energized current. For example, if the locations of the third and fourth loop branches are used as the E and S test points, the first mid-circuit branch can be located between the second and fourth loop branches. If the locations of the first and second loop branches are used as the E and S test points, the first mid-circuit branch can be located between the first and third loop branches.

[0058] See also Figure 8 As shown, in a preferred solution of this embodiment, the number of first middle branch nodes 4 is greater than or equal to two, and the current directions of each first middle branch node 4 are the same, so that the magnetic fields generated by all first middle branch nodes 4 after being energized are superimposed in the same direction.

[0059] In this preferred embodiment, the purpose of providing multiple first mid-circuit branches 4 with unidirectional current is to ensure that the magnetic field generated by the first mid-circuit branch 4 upon energization can superimpose with the magnetic field generated by the loop branch located on one side of it upon energization, thereby strengthening the magnetic field strength in the area on that side, corresponding to test point E or test point S in the test case. Simultaneously, the magnetic field generated by the first mid-circuit branch 4 partially offsets the magnetic field generated by the loop branch on the other side, thereby partially weakening the magnetic field strength in the area on that side, corresponding to test point W or test point N in the test case. Since the test terminal overlaps significantly with the W and N test points during testing, even if the magnetic field strength at the W and N test points is weakened or lower than that at the E and S test points, the magnetic field strength at these two test points still meets the detection standard sensed by the terminal under test, meeting the test requirements for the W and N test points (corresponding to Test Cases 5 and 11).

[0060] Therefore, the current directions of the first mid-circuit branches 4 must be the same, otherwise the magnetic fields generated by the first mid-circuit branches 4 will cancel each other out. In addition, by increasing the number of first mid-circuit branches 4 with currents in the same direction, the magnetic field strength in the area where the E or S point is located can be further increased.

[0061] In an alternative embodiment of this embodiment, if the third and fourth loop branches correspond to the E and S test points during the certification test, the third and fourth loop branches include unidirectional branches, and the first and second loop branches include unidirectional branches and counter-directional branches. The current direction of the unidirectional branches is the same as the current direction of the first mid-circuit branch 4, and the current direction of the counter-directional branches is opposite to the current direction of the first mid-circuit branch 4.

[0062] In another optional scheme of this embodiment, if the first loop branch and the second loop branch correspond to the E and S test points during the certification test, the first loop branch and the second loop branch include same-direction branches, and the third loop branch and the fourth loop branch include same-direction branches and reverse branches.

[0063] The two alternatives described above essentially provide a structural design method for adding a first central branch 4 to a conventional toroidal coil. The principle is that, in the process of adding the first central branch 4 or increasing the number of first central branches 4 to enhance the current intensity in the central region, to ensure a consistent winding return path for the first coil 2, additional return lines for both unidirectional and reverse currents must be added to the first coil loop 3. In this solution, the additional reverse current return lines are located in the first and second loop branches.

[0064] Specifically, since the overlapping area between the W and N test points and the NFC antenna coil of the test terminal is large and the requirement for magnetic field strength is low, the reverse current of the W and N test points can be increased (that is, the additional reverse branches are set at the loop branches where the W and N test points are located), and the unidirectional current of the S and E test points can be increased (that is, the additional unidirectional branches are set at the S and E test points). Ultimately, the loop branches where the W and N test points are located include both unidirectional branches and reverse branches, while the loop branches where the S and E test points are located only include unidirectional branches, thereby increasing the horizontal magnetic field component of the C test point and enhancing the magnetic field strength of the S and E test points.

[0065] In an optional solution of this embodiment, the number of first coil loops 3 increases by n every time the number of first mid-circuit branches 4 increases by 2n, where n is a positive integer greater than or equal to 1.

[0066] Specifically, considering the winding return path of the first coil 2, increasing the number of first central branches 4 requires simultaneously increasing the current intensity of the first coil loop 3. Given that the current flowing through each first central branch 4 is the same, the number of branches can be used to represent the current intensity. Therefore, whenever the number of first central branches 4 increases by an even number, the number of surrounding loop branches increases by half that number, meaning the number of coil loops increases by half that number.

[0067] Preferably, the number of the first mid-circuit branches 4 is two, and the number of windings of the first coil loop 3 increases by one.

[0068] Further preferably, the number of the first middle branches 4 is four, and the number of windings of the first coil loop 3 increases by two.

[0069] In another alternative embodiment of this embodiment, for any first loop branch, second loop branch, third loop branch, or fourth loop branch (i.e., a switching branch containing reverse current) that includes both unidirectional branches and reverse current branches, the number of reverse current branches must be two or more less than the number of unidirectional branches. The purpose of this design is to: During certification testing, even if the W and N test points have low magnetic field strength requirements, if the number of reverse branches at the corresponding points is too large, the magnetic field will be too weak, resulting in failure to meet the test requirements even if the magnetic field overlaps a large area with the NFC antenna coil of the test terminal. Therefore, for any loop branch that includes both unidirectional branches and reverse branches, the number of reverse branches with reverse current must be two or more less than the number of unidirectional branches with forward current.

[0070] See also Figure 8 As shown, in an optional scheme of this embodiment, the first middle branch 4 is arranged in the middle of the first loop branch and the third loop branch, and is arranged parallel to the first loop branch and the third loop branch, and is connected to the second loop branch and the fourth loop branch.

[0071] Specifically, the first mid-circuit branch 4 is centrally positioned and parallel to the first and third loop branches on either side of it. With this design, the magnetic field generated by the first mid-circuit branch 4 upon energization can overlap with the magnetic field generated by the loop branches on one side (e.g., the third loop branch). Because the first mid-circuit branch 4 and the third loop branch are parallel, the magnetic field vector directions generated by the two branches remain consistent and overlap at specific points, reinforcing each other and maximizing the magnetic field enhancement effect. Furthermore, the central placement of the first mid-circuit branch 4 prevents the magnetic field generated by the first mid-circuit branch 4 from excessively offsetting the magnetic field generated by the loop branches on the other side (e.g., the first loop branch) upon energization, thereby preventing excessive weakening of the magnetic field on that side.

[0072] See also Figure 8 As shown, in another optional scheme of this embodiment, the first middle branch 4 is arranged in the middle of the second loop branch and the fourth loop branch, and is arranged parallel to the second loop branch and the fourth loop branch, and is connected to the first loop branch and the third loop branch.

[0073] Specifically, the first mid-circuit branch 4 is centrally positioned and parallel to the second and fourth loop branches on either side of it. With this design, the magnetic field generated by the first mid-circuit branch 4 upon energization can overlap with the magnetic field generated by the loop branches on one side (e.g., the fourth loop branch). Because the first mid-circuit branch 4 and the fourth loop branch are parallel, the magnetic field vector directions generated by the two branches remain consistent and overlap at specific points, reinforcing each other and maximizing the magnetic field enhancement effect. Furthermore, the central placement of the first mid-circuit branch 4 prevents the magnetic field generated by the first mid-circuit branch 4 from excessively offsetting the magnetic field generated by the loop branches on the other side (e.g., the second loop branch) upon energization, thereby preventing excessive weakening of the magnetic field on that side.

[0074] Example 2 In a second embodiment of the present invention, another structural design solution for a vehicle-mounted NFC antenna is provided.

[0075] See also Figure 10-12 As shown, in the technical solution of this embodiment, the in-vehicle NFC antenna includes a substrate 1, a first coil 2, and a second coil 5. The substrate 1 includes a first side surface and a second side surface disposed opposite each other. The first coil 2 is disposed on the first side surface, and the second coil 5 is disposed on the second side surface. The first coil 2 includes a first coil loop 3 in a rectangular shape, and the second coil 5 includes a second coil loop 6 in a rectangular shape. The first coil loop 3 includes four loop branches (i.e., the first, second, third, and fourth loop branches described in Example 1). Correspondingly, the second coil loop 6 also includes four loop branches. A second middle branch 7 is disposed in the middle portion of the second coil loop 6. The second middle branch 7 and the first middle branch 4 are arranged intersectingly; alternatively, the second middle branch 7 and the first middle branch 4 are arranged parallel to each other.

[0076] See also Figure 13 As shown, based on the structural design of the first mid-circuit branch 4 and the second mid-circuit 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. This means that the magnetic field generated by energizing the first coil 2 and the second coil 5 has a horizontal vector in this central region. Therefore, when a test terminal (such as a mobile phone) enters the magnetic field using any vertical card swiping posture, a horizontal magnetic field component will pass through the test terminal's NFC antenna coil, allowing the test terminal's NFC antenna to receive sufficient magnetic field energy to meet the test requirements of point C (corresponding to Test Case 5).

[0077] See also Figure 13As shown, based on the structural design of the first mid-circuit branch 4 and the second mid-circuit branch 7, in the first coil loop 3, between the first and third loop branches, and between the second and fourth loop branches, there must be a region where the magnetic field strength of two of the loop branches is greater than that of the other two loop branches. Similarly, in the second coil loop 6, there are also two loop branches where the magnetic field strength is greater than that of the other two loop branches. In addition, by designing the first and second mid-circuit branches 4 and 7 to be parallel to each other, magnetic field superposition can be achieved, further strengthening the tangential magnetic field strength generated by the two mid-circuit branches.

[0078] Compared with the uniform magnetic field distribution of traditional NFC antennas, the above design has two loop branches with stronger magnetic fields, corresponding to the E and S test points of Carkey certification. Due to the stronger magnetic field strength at these two points, when using the test postures of Test Cases 9 and 12, it can ensure that the energy intensity of the electromagnetic wave beam perpendicular to the test terminal in these two states can meet the detection standard of induction by the tested terminal at a specified distance (for example, 40mm), thereby meeting the test requirements of the E and S test points (corresponding to Test Cases 9 and 12).

[0079] Furthermore, in the technical solution of this embodiment, the on-board NFC antenna utilizes a double-layer routing scheme, enabling the intersecting first mid-circuit branch 4 and second mid-circuit branch 7 to interfere with the magnetic field of the first coil loop 3 and the second coil loop 6 in four directions. This design objective is to make the test direction of the on-board NFC antenna no longer dependent on a specific direction, thereby enabling control of the magnetic field strength at different test points by controlling only the current direction. During specific testing, regardless of the on-board NFC antenna's layout, it can meet CarKey authentication requirements in any state, eliminating the need to adaptively adjust the orientation of the W, E, N, and S test points based on the magnetic field strength of the specific loop branch, thereby further optimizing subsequent testing and authentication operations.

[0080] More specifically, this design simplifies the testing and certification process for in-vehicle NFC antennas, reducing testing complexity and cost while improving test efficiency and accuracy. This ensures that in-vehicle NFC antennas can quickly and accurately pass CarKey certification in various conditions. Furthermore, frequent adjustments to the NFC antenna layout are no longer necessary to ensure successful certification across different vehicle models and usage environments. This allows in-vehicle NFC antennas to better adapt to various complex environments, improves system reliability and stability, and provides users with a more convenient and stable user experience.

[0081] See also Figure 12As 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 feeding terminal, so that the current of the first coil 2 and the second coil 5 flows in the same direction.

[0082] This design allows the magnetic flux generated by the current passing through the first coil 2 to couple with the magnetic flux generated by the current passing through the second coil 5, thereby achieving electromagnetic coupling between the two coils and superimposing the magnetic flux. When current passes through the first coil 2 and the second coil 5, due to their winding directions, currents flow in the same direction in both coils. This enhances the electromagnetic coupling between the two coils, resulting in better energy transfer.

[0083] See also Figure 12 As shown, in a preferred embodiment of the present invention, 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 can overlap, thereby enhancing the electromagnetic coupling effect between the first coil 2 and the second coil 5 and achieving higher energy transmission efficiency.

[0084] Furthermore, the second mid-circuit branch 7 and the first mid-circuit branch 4 are perpendicular to each other and centered within their respective coil loops. This ensures that the magnetic fields generated by these branches are evenly distributed within the magnetic fields of their respective coils, preventing any significant strengthening or weakening of any particular branch in the coil loop. This design also optimizes the overall magnetic field environment of the NFC antenna, reducing signal interference and communication instability caused by magnetic field inhomogeneities, and improving the accuracy and reliability of CarKey authentication.

[0085] Of course, the second embodiment of the present invention is an improvement based on the first embodiment. The technical features not elaborated in detail in this embodiment (such as the number and current direction of the second middle branch nodes 7, the structural design of the four loop branches of the second coil loop 6, etc.) are the same as the first middle branch node 4 and the first coil loop 3 in the first embodiment, and will not be repeated in this embodiment.

[0086] The technical means disclosed in the solutions of the present invention are not limited to those disclosed in the above-mentioned embodiments, but also include technical solutions composed of any combination of the above-mentioned technical features. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A vehicle-mounted NFC antenna, characterized in that: include: a substrate, the substrate comprising a first side surface and a second side surface disposed opposite to each other; a first coil, the first coil being disposed on the first side surface, the first coil comprising a first coil loop in a rectangular shape, the first coil loop comprising 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 being disposed opposite each other, and the second loop branch and the fourth loop branch being disposed opposite each other; wherein a central region of the first coil loop has a magnetic field component parallel to the substrate; Moreover, the magnetic field strength of the third loop branch is greater than that of the first loop branch, and the magnetic field strength of the fourth loop branch is greater than that of the second loop branch; or, the magnetic field strength of the first loop branch is greater than that of the third loop branch, and the magnetic field strength of the second loop branch is greater than that of the fourth loop branch.

2. The vehicle-mounted NFC antenna according to claim 1, characterized in that: The first coil further includes a first middle branch node connected to the first coil loop, wherein the first middle branch node is arranged between the first loop branch node and the third loop branch node; or, the first middle branch node is arranged between the second loop branch node and the fourth loop branch node.

3. The vehicle-mounted NFC antenna according to claim 2, characterized in that: The number of the first mid-path branches is greater than or equal to two, and the current directions of the first mid-path branches are the same.

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

5. The vehicle-mounted NFC antenna according to claim 4, characterized in that: Every time the number of the first middle branch nodes increases by 2n, the number of the first coil loops increases by n; wherein 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 one of the first loop branch, the second loop branch, the third loop branch or the fourth loop branch that includes both the same-direction branches and the reverse-direction branches, the number of the reverse-direction branches is two or more less than the number of the same-direction branches.

7. The vehicle-mounted NFC antenna according to claim 2, characterized in that: The first middle branch node is located in the middle of the first loop branch node and the third loop branch node, and is arranged parallel to the two; or, the first middle branch node is located in the middle of the second loop branch node and the fourth loop branch node, and is arranged parallel to the two.

8. The vehicle-mounted NFC antenna according to any one of claims 2 to 7, characterized in that: The vehicle-mounted NFC antenna further includes a second coil, which is disposed on the second side surface. The second coil includes a second coil loop in a rectangular shape and a second middle branch disposed in the middle of the second coil loop. The second middle branch node and the first middle branch node are arranged to cross each other; or the second middle branch node and the first middle branch node are arranged to be parallel to each other.

9. The vehicle-mounted NFC antenna according to claim 8, characterized in that: The second coil is connected to the first coil, and currents of the first coil and the second coil flow in the same direction, so that the magnetic flux generated by the current passing through the first coil and the magnetic flux generated by the current passing through the second coil are superimposed.

10. The vehicle-mounted NFC antenna according to claim 8, characterized in that: The second coil loop and the first coil loop are arranged in parallel with each other; the second middle branch node and the first middle branch node are arranged perpendicular to each other.

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