Antenna structure and wheel structure with tire pressure monitoring system

Abstract

This invention discloses a wheel unit antenna and a corresponding wheel structure for a tire pressure monitoring system (TPMS), wherein the antenna is sized and oriented such that the entire wheel structure, including the tire, will act as a waveguide. The antenna can be non-resonant and in the form of a monopole antenna perpendicular to the ground plane. Furthermore, the antenna length is significantly shorter than a quarter wavelength, for example, one-tenth of a wavelength (λ / 10) or less.

Description

Technical Field

[0001] This invention relates to the field of tire pressure monitoring systems, and particularly to antenna structures for tire pressure monitoring systems and wheel structures with tire pressure monitoring systems. Background Technology

[0002] Especially in the automotive industry, tire pressure monitoring sensors (TPMS), sometimes referred to as wheel units, are increasingly important products. They transmit tire pressure information via radio frequency signals to a main receiver in the car or vehicle. This information can then be used to notify the user of tire conditions or for further processing for other purposes. In addition to tire pressure, tire pressure monitoring systems (TPMS) or wheel units can also transmit other useful information, such as tire temperature or information related to different stress conditions encountered inside or on the tire.

[0003] Typically, the radio spectrum used can be the ISM band (Industrial, Scientific, and Medical bands) (such as 315MHz or 434MHz), or higher frequencies can be used in newer systems, such as Bluetooth Low Energy (2.4 to 2.48GHz). Even Ultra Wideband (UWB) can be used.

[0004] Compared to the size of the wheel unit, the frequency of the ISM band and the operating wavelength of Bluetooth Low Energy (BLE) are relatively long, while the size of the wheel unit is limited by physical space and is usually very small; in addition, the wheel unit must integrate all electronic components, including sensors, batteries, microcontrollers, corresponding circuits and radio frequency antennas, in the housing.

[0005] Therefore, the antenna for a tire pressure monitoring system (TPMS) or wheel unit must be small enough to fit within the wheel unit, but preferably large enough to be at least approximately a quarter wavelength (λ / 4) for resonance and efficient transmission and / or reception. Due to their small size, electrically small loop antennas are also used in the ISM band, but these types of antennas typically have low radiation efficiency (below -15 dB, even below -20 dB). Furthermore, the surrounding environment, consisting of the metal rim and tire (rubber and metal structural components), itself introduces additional damping, further reducing the overall radiation efficiency of the antenna. Summary of the Invention

[0006] Electromagnetic analysis of the entire wheel system (metal rim and tire) reveals other electromagnetic modes with good antenna transmission efficiency within the wheel structure. These modes can be specifically excited using a specially designed antenna, thereby benefiting from the maximum radiation characteristics of the wheel structure and the system itself.

[0007] Embodiments of the present invention include small antenna sizes, having electrically small monopoles or dipoles smaller than or even much smaller than a quarter wavelength. These do not resonate but can still excite desired electromagnetic modes within a wheel structure. One embodiment uses an antenna with a length of one-tenth of a wavelength (λ / 10) or less. Advantages include the ability to tune the transmitter to frequencies exhibiting the maximum achievable antenna radiation efficiency; for example, in the ultra-wideband (UWB) frequency range, there are multiple 500 MHz wide channels between 5 GHz and 9 GHz, as detailed below, which can be used to improve system efficiency. The same advantages can be applied to other wideband frequency ranges.

[0008] The present invention includes a simple and compact antenna placed within the wheel unit of a tire pressure monitoring system (TPMS), which achieves the aforementioned advantages and outperforms the larger antennas used in existing TPMS systems. The solution according to the invention benefits from the consideration that the entire wheel structure, including the tire, can act as a waveguide. This structure, depending on its overall size (determined by the wheel and tire type), generates specific electromagnetic propagation modes, which have relevant selections within the operating frequency range. The most effective mode is selected from these modes to excite the wheel using the antenna design and direction described in this invention.

[0009] Embodiments of the present invention include a wheel structure with a tire pressure monitoring system (TPMS), the system including an antenna according to the present invention, wherein the assembled wheel structure includes a non-resonant antenna whose dimensions and orientation are determined such that the entire wheel structure, including the tire, will act as a waveguide.

[0010] Embodiments of the invention also include manufacturing a wheel structure with a tire pressure monitoring system (TPMS), the system including an antenna according to the invention. The wheel structure and antenna efficiency can be simulated, and the antenna's position and / or size can be determined based on the simulation results of the antenna efficiency. The wheel structure can then be assembled using the determined antenna position and / or size. Attached Figure Description

[0011] In the attached diagram:

[0012] Figure 1 The characteristic patterns of a general wheel model are shown;

[0013] Figure 2 An embodiment based on the concept of the present invention is shown;

[0014] Figure 3 A conceptual model showing the complete cross-section of the wheel structure;

[0015] Figure 4 This shows the dependence of antenna efficiency on frequency and wheel size;

[0016] Figure 5 An alternative embodiment based on the concept of the present invention is shown;

[0017] Figure 6 This demonstrates the dependence of antenna efficiency on frequency and wheel size for a known quarter-wavelength antenna;

[0018] Figure 7 This illustrates the dependence of antenna efficiency on frequency for another embodiment of the concept according to the invention; and

[0019] Figure 8 The antenna's radiation efficiency is shown. Detailed Implementation

[0020] In embodiments of the invention, the antenna is sized and positioned such that the entire wheel structure, including the tire, functions similarly to a waveguide. The structure of the invention, depending on its overall dimensions and / or wheel and tire type, can benefit from specific electromagnetic propagation modes, some of which can be selected within the operating frequency range. Using the antenna design and orientation conceived according to the invention, the most effective modes among these can be selectively excited. The selected electromagnetic propagation modes within the operating frequency range can be demonstrated by running eigenmode analysis or an eigenmode solver.

[0021] The entire wheel is a relatively large structure, so its characteristic first mode may be excited below 2.4 GHz. Figure 1 This demonstrates the eigenmode analysis for a general wheel model in Ansys AEDT. Small monopole antennas can be excited using these improved electromagnetic modes, providing good radiation efficiency. It can even be found that structural propagation modes are excited at frequencies far below 2.35 GHz, for example, through eigenmode analysis. Figure 1 The curve 100 is shown in the figure.

[0022] This exemplary embodiment demonstrates that the concept of the present invention can be realized by placing a very simple small antenna inside the wheel unit of a tire pressure monitoring system (TPMS), and the present invention is actually more effective than the standard larger antenna used in tire pressure monitoring systems (TPMS).

[0023] These analyses have been performed using Ansys AEDT electromagnetic simulation. For this purpose, specific electrical models were implemented, including wheel models, tire models, and tire pressure monitoring system (TPMS) wheel unit models. The wheels and tires are adjustable for different sizes commonly used in the market. The wheel unit model is a simplified model suitable for antenna performance analysis, comprising the housing, battery, printed circuit board, and simplified metal valve assembly. This is from... Figure 2As can be seen, the wheel unit 200 includes an antenna 210 perpendicular to the printed circuit board (PCB).

[0024] Antenna 210 may be too short to resonate at the frequency used for transmission, and therefore it is used to excite the wheel structure. In embodiments, the antenna may have a length significantly shorter than a quarter wavelength. In some embodiments, the antenna length may be one-tenth of a wavelength (λ / 10) or shorter. In some embodiments, the antenna length is approximately 5 millimeters.

[0025] The cross-section of the complete wheel structure built in Ansys AEDT is as follows: Figure 3 As shown in Figure 300. The wheel structure can be simulated before assembly. Advantageous embodiments and methods for manufacturing a wheel structure with a tire pressure monitoring system (TPMS) including an antenna according to the invention may include simulating the wheel structure and antenna efficiency. The position and / or size of the antenna can be determined based on the simulation results of the antenna efficiency. The simulation results can then be applied to assemble the wheel unit and wheel structure, wherein the position and / or size of the antenna are determined according to the simulation results. In embodiments of the method of the invention, the position and / or size of the antenna can be determined such that the efficiency is at least between -2dB and -4dB, or within any other efficiency range required for the target application.

[0026] Using the above model, broadband analysis was performed between 1 GHz and 3 GHz. The overall radiation efficiency of the small antenna was studied for four wheel (tire + rim) sizes (195 / 65R15; 205 / 55R16; 235 / 40R17 and 235 / 45R18), and the results are plotted in [the table / image / image]. Figure 4 middle.

[0027] It can be seen that the antenna efficiency varies greatly depending on the frequency and wheel size; in the Bluetooth Low Energy (BLE) band at 410, the antenna efficiency is close to the maximum value, as shown in the figure, between 2dB and -4dB.

[0028] The following analysis used a similar model, but as Figure 5 As shown, an additional capacitively loaded top metallized surface is added to the inner wall of the housing above the antenna. In this example, the metallized plane is perpendicular to the antenna. Device 520 is a metal plane capacitively coupled to the antenna 510 without direct contact.

[0029] like Figure 6 As shown, by implementing this type of capacitive loading, antenna efficiency is further improved. Efficiency 600 rises to almost its maximum (above -2dB) in the Bluetooth Low Energy (BLE) band, as shown in 610.

[0030] exist Figure 6The diagram illustrates the efficiency traces for various wheel / tire configurations that are always in a BLE communication environment. Trace 615 shows the efficiency of the 195 65R15 wheel / tire combination as a function of frequency. Trace 625 shows the efficiency of the 205 55R16 wheel / tire combination as a function of frequency. Trace 635 shows the efficiency of the 235 40R17 wheel / tire combination as a function of frequency. Trace 645 shows the efficiency of the 235 45R18 wheel / tire combination as a function of frequency.

[0031] For comparison, a common quarter-wave antenna, typically used in such Bluetooth Low Energy (BLE) designs, was inserted into a similar wheel-type unit model to identify differences and improvements compared to the method described in this invention. Figure 7 As shown, the comparison is performed using a 205 / 55R16 wheel assembly. Trace 715 shows a 205 / 55R16 wheel / tire assembly with a small monopole antenna, trace 725 shows a 205 / 55R16 assembly with a small monopole antenna and a capacitive load, and trace 735 shows a 205 / 55R16 assembly with a quarter-wave inverted-F (IFA) antenna.

[0032] It is easy to see that even though the IFA antenna is much longer than the proposed small monopole antenna, its overall radiation efficiency is also lower, with a Δ value of approximately -3dB in the middle of the Bluetooth Low Energy (BLE) band compared to the top-loaded monopole antenna. This means that the antenna's position within the wheel structure and the optimal excitation of the electromagnetic mode are more important than the antenna length.

[0033] The solution of this invention also has the same advantages in ultra-wideband (UWB) frequencies. Depending on the frequency band where the maximum achievable efficiency value can be found, the system of this invention specifies certain channels or frequency bands instead of other channels or frequency bands with lower efficiency. In implementation, this can be achieved using a software application, thus requiring no hardware changes.

[0034] Figure 8 This demonstrates that when using a reference monopole antenna, the antenna radiation efficiency is independent of its length—similar values ​​can be obtained by placing 3 mm and 5 mm high monopole antennas on a 16-inch wheel. Trace 815 corresponds to the 3 mm monopole antenna, and trace 825 corresponds to the 5 mm monopole antenna. Therefore, in such an embodiment, the overall performance of the antenna depends on its position on the wheel and the overall wheel structure, not on the antenna length.

[0035] In addition to using standard Bluetooth and Bluetooth Low Energy (BLE) for communication, this invention can also be used with other communication standards and frequencies compatible with the aforementioned antenna.

[0036] This invention is applicable to wheel structures with tire pressure monitoring systems (TPMS) using the aforementioned antenna concept. The assembled wheel structure uses a non-resonant antenna. The antenna should be sized and oriented such that the entire wheel structure, including the tire, acts as a waveguide.

[0037] The inventive concept can also be used to manufacture wheel structures for TPMS systems including antennas as described above. First, the wheel structure and antenna efficiency are simulated, and the antenna's position and / or size are determined based on the simulation results to improve antenna efficiency. Then, the wheel structure is assembled using the determined antenna position and / or size. In one embodiment, the assembled wheel structure presents a non-resonant antenna, which is sized and oriented such that the complete wheel structure, including the tire, will act as a waveguide.

[0038] Therefore, this invention provides an improved solution compared to existing resonant antenna structures used in vehicle tire pressure monitoring systems. By using a tiny, non-resonant monopole antenna correctly positioned within the wheel unit above a ground plane defined by a printed circuit board (PCB), excellent system radiation efficiency can be provided over a wide frequency range. This means that the invention is not limited to a specific frequency band but can be adapted to different applications.

Claims

1. A wheel unit antenna for a tire pressure monitoring system, wherein, The antenna is non-resonant, and its size and orientation are determined such that the entire wheel structure, including the tire, will act as a waveguide. An additional capacitive load on top of the antenna is metallized to improve antenna efficiency.

2. The car wheel unit antenna according to claim 1, wherein, The antenna is a monopole perpendicular to the ground plane.

3. The car wheel unit antenna according to claim 1 or 2, wherein, The antenna length is less than a quarter wavelength.

4. The car wheel unit antenna according to claim 1 or 2, wherein, The antenna length is one-tenth of a wavelength (λ / 10) or shorter.

5. The wheel unit antenna according to claim 1 or 2, wherein, The antenna is approximately 5 centimeters long.

6. The wheel unit antenna according to claim 1 or 2, wherein, The metallized plane above the antenna is perpendicular to the antenna.

7. A wheel unit for a tire pressure monitoring system, which communicates using standards including Bluetooth and Bluetooth Low Energy (BLE), wherein, Communication is performed using the wheel unit antenna according to any one of claims 1-6.

8. A wheel structure with a tire pressure monitoring system comprising a wheel unit antenna according to any one of claims 1-6, wherein, The assembled wheel structure includes a non-resonant antenna, which is sized and oriented such that the entire wheel structure, including the tire, will act as a waveguide. A top metallized plane of an additional capacitive load above the antenna is used to improve antenna efficiency.

9. A method for manufacturing a wheel structure with a tire pressure monitoring system comprising a wheel unit antenna according to any one of claims 1-6, wherein, The wheel structure and antenna efficiency are simulated, and the antenna position and / or size are determined based on the simulation results of the antenna efficiency. The wheel structure is then assembled with the determined antenna position and / or size. The assembled wheel structure includes a non-resonant antenna, which is sized and oriented such that the entire wheel structure, including the tire, will act as a waveguide. A top metallized plane of an additional capacitive load above the antenna is used to improve antenna efficiency.

10. The method of claim 9, wherein, Determine the location and / or size of the antenna so that the efficiency is between -2 dB and -4 dB.

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