Circuit board assembly, radar, and vehicle

Abstract

Embodiments of the present application provide a circuit board assembly, a radar and a vehicle. The circuit board assembly comprises a circuit board, at least one antenna, at least two radio frequency chips and a first cover layer. The circuit board comprises a plurality of core layers and a plurality of circuit layers arranged between adjacent two core layers; the circuit layer comprises a plurality of first transmission lines and a plurality of second transmission lines. The two ends of the second transmission line are electrically connected with the antenna and the second radio frequency chip respectively. The first cover layer is arranged on the circuit board; wherein the relative dielectric constant of the first cover layer is linearly related to the transmission speed of the first radio frequency signal, so that the speed ratio of the transmission speed of the first radio frequency signal and the transmission speed of the second radio frequency signal is equal to the length ratio of the first transmission line and the second transmission line. When wiring the first transmission line and the second transmission line, there is no need to consider the restriction of the same wiring length, and when the wiring space and position requirements are met, the first transmission line and the second transmission line can be arranged in a regular straight line shape as much as possible.

Description

Technical Field

[0001] This application relates to the field of radar technology, specifically to circuit board assemblies, radar, and vehicles. Background Technology

[0002] In recent years, radar applications have become increasingly widespread, with millimeter-wave radar playing a crucial role in fields such as automotive driver assistance, security, and healthcare. For radar to function properly, each RF port of the RF chip and each antenna must be interconnected via low-loss, low-dispersion RF transmission lines. To ensure that the transmission phase of each antenna to the transmission line is the same within a certain bandwidth, the transmission lines corresponding to each antenna channel must be geometrically equal in length. Achieving this equal length requires introducing structures such as S-bends to extend the geometric path in the transmission lines. The equal-length wiring process is extremely cumbersome, and the insertion loss and inter-channel coupling caused by equal-length wiring also limit further improvements in radar performance. Summary of the Invention

[0003] This application provides circuit board assemblies, radar, and vehicles to reduce wiring complexity, improve radar radio frequency performance, and shorten development cycles.

[0004] To achieve the above objectives, this application adopts the following technical solution:

[0005] A first aspect of this application provides a circuit board assembly, including a circuit board, at least one antenna, at least two radio frequency (RF) chips, and a first cover layer. The circuit board includes a multilayer core board and a wiring layer disposed between two adjacent core boards; the wiring layer includes multiple first transmission lines and multiple second transmission lines; wherein any two first transmission lines are of the same length, and any two second transmission lines are of the same length. At least two RF chips are disposed on the circuit board, namely a first RF chip and a second RF chip; the two ends of each first transmission line are electrically connected to the antenna and the first RF chip, respectively, and the first transmission line is used to transmit a first RF signal between the antenna and the first RF chip; the two ends of each second transmission line are electrically connected to the antenna and the second RF chip, respectively, and the second transmission line is used to transmit a second RF signal between the antenna and the second RF chip; the first cover layer is disposed on the circuit board and covers the multiple first transmission lines; wherein the relative permittivity of the first cover layer satisfies a first condition, the first condition being that the relative permittivity of the first cover layer is linearly related to the transmission speed of the first RF signal, and such that the ratio of the transmission speed of the first RF signal to the transmission speed of the second RF signal is equal to the ratio of the lengths of the first and second transmission lines.

[0006] The aforementioned circuit board assembly adjusts the transmission speed of the first radio frequency (RF) signal through the first cover layer, ensuring that the ratio of the transmission speeds of the first and second RF signals equals the length ratio of the first and second transmission lines. This guarantees that the transmission phase from the antenna to the transmission lines is the same. Therefore, when routing the first and second transmission lines, there is no need to consider the limitation of identical wiring lengths. While meeting the requirements for wiring space and location, the first and second transmission lines can be arranged in a regular straight-line shape as much as possible. Thus, the wiring of the first and second transmission lines is simple, reducing the radar development cycle and difficulty. Furthermore, the shorter line lengths of the first and second transmission lines also result in lower transmission loss.

[0007] Optionally, the circuit board assembly further includes a second cover layer disposed on the circuit board and covering multiple second transmission lines. The relative permittivity of the second cover layer satisfies a second condition: the relative permittivity of the second cover layer is linearly related to the transmission speed of the second radio frequency (RF) signal, and the ratio of the transmission speed of the first RF signal to the transmission speed of the second RF signal is equal to the length ratio of the first transmission line to the second transmission line. The relative permittivity of the first cover layer and the second cover layer are different. Thus, the transmission speed of the first RF signal can be adjusted simultaneously through the first cover layer and the transmission speed of the second RF signal through the second cover layer, adjusting the ratio of the transmission speeds of the first and second RF signals. This adjustment method is more flexible and precise, and can adapt to more complex wiring requirements.

[0008] Optionally, at least one antenna includes a transmitting antenna; multiple first transmission lines include multiple first transmitting transmission lines, with both ends of the first transmitting transmission lines electrically connected to the transmitting antenna and a first radio frequency chip, respectively; multiple second transmission lines include multiple second transmitting transmission lines, with both ends of the second transmitting transmission lines electrically connected to the transmitting antenna and a second radio frequency chip, respectively; the length ratio of the first transmitting transmission lines to the second transmitting transmission lines is n, and the speed ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n, where n > 0. Thus, the phase from the transmitting antenna to the first transmitting transmission lines and the second transmitting transmission lines is the same, ensuring that the millimeter-wave signal does not generate a phase difference when it is transmitted from the transmitting antenna, thereby improving the high-resolution angle measurement capability of the corresponding radar.

[0009] Optionally, at least one antenna further includes a receiving antenna; the plurality of first transmission lines further include a plurality of first receiving transmission lines, with both ends of the first receiving transmission lines electrically connected to the receiving antenna and the first radio frequency chip, respectively; the plurality of second transmission lines further include a plurality of second receiving transmission lines, with both ends of the second receiving transmission lines electrically connected to the receiving antenna and the second radio frequency chip, respectively; the length ratio of the first receiving transmission lines and the second receiving transmission lines is n2, and the speed ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n2, where n2 > 0. Thus, the phase from the receiving antenna to the first receiving transmission lines and the second receiving transmission lines is the same, ensuring that the received millimeter-wave signal does not generate a phase difference during transmission to the corresponding radio frequency chip, thereby improving the high-resolution angle measurement capability of the corresponding radar.

[0010] Optionally, the first and second overlay layers can be placed on the same layer. This makes the manufacturing process more convenient.

[0011] Alternatively, the core board can be made of the same material as the first cover layer. This simplifies the manufacturing process of the first cover layer.

[0012] Optionally, the first and second transmission lines can be microstrip transmission lines, coplanar waveguide transmission lines, or grounded coplanar waveguide transmission lines. These types of transmission lines have relatively low transmission loss, thereby improving radar resolution.

[0013] Optionally, the first and second transmission lines may include straight segments. This simplifies the wiring process.

[0014] Optionally, the first transmission line and the second transmission line are located on the same circuit layer. This allows for a single photolithography process, thus simplifying the fabrication process.

[0015] Optionally, at least one of the materials, widths, and thicknesses of the first and second transmission lines is the same. This minimizes the impact of differences between the first and second transmission lines on the transmission speed of the radio frequency signal, allowing the transmission speed of the radio frequency signal to be adjusted through the overlay layer.

[0016] A second aspect of this application provides a radar, which includes a housing and the aforementioned circuit board assembly, the circuit board assembly being disposed within the housing. The aforementioned radar has a high resolution angle measurement capability.

[0017] A vehicle includes a body and the aforementioned radar mounted on the body. The radar provides information on the distance, speed, and azimuth of a target, thereby assisting a driver or autonomous driving system in making judgments and achieving the goal of safe driving. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of a vehicle provided in this application embodiment;

[0019] Figure 2a This application provides a schematic diagram of the internal structure of a radar according to an embodiment of the present application.

[0020] Figure 2b A cross-sectional structural diagram of a radar provided in an embodiment of this application;

[0021] Figure 3a A top view of a circuit board assembly provided in an embodiment of this application;

[0022] Figure 3b Wave velocity-coating layer dielectric constant curve provided for embodiments of this application;

[0023] Figure 3c A linear fitting diagram of wave velocity and capping layer dielectric constant provided for embodiments of this application;

[0024] Figure 3d A full-wave simulation result diagram of the transmission phase of the transmission line provided in the embodiments of this application;

[0025] Figure 3e A schematic diagram of the transmission line length provided in the embodiments of this application;

[0026] Figure 3f A schematic diagram of a millimeter radar wave signal provided in an embodiment of this application;

[0027] Figure 3g A flowchart illustrating a method for determining the relative permittivity of a capping layer provided in an embodiment of this application;

[0028] Figure 4 A cross-sectional structural schematic diagram of a circuit board assembly provided in an embodiment of this application;

[0029] Figure 5 A top view of a circuit board assembly provided in another embodiment of this application;

[0030] Figure 6 A top view of a circuit board assembly provided in another embodiment of this application;

[0031] Figure 7 A top view of a circuit board assembly provided in another embodiment of this application;

[0032] Figure 8 This is a top view of a circuit board assembly provided in another embodiment of this application.

[0033] Figure label:

[0034] 01. Automobile; 02. Radar; 021. Housing; 022. Circuit board assembly; 10. Circuit board; 11. Core board; 12. Circuit layer; 13. First transmission line; 14. Second transmission line; 131. First transmitting transmission line; 132. First receiving transmission line; 141. Second transmitting transmission line; 142. Second receiving transmission line; 20. Antenna; 21. Transmitting antenna; 22. Receiving antenna; 30. First radio frequency chip; 40. Second radio frequency chip; 50. First cover layer; 60. Second cover layer; 1a. Target object; S1. Transmitting millimeter wave; S2. Reflecting millimeter wave. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0036] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0037] Furthermore, in this application, directional terms such as "upper" and "lower" may be defined relative to the orientation in which the components are schematically placed in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation in which the components are placed in the accompanying drawings.

[0038] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled" can refer to a method of electrical connection for signal transmission. "Coupled" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0039] refer to Figure 1 This application provides a vehicle 01. Vehicle 01 can be a car, motorcycle, bus, truck, or construction vehicle, etc. This application does not limit the type of vehicle 01; for ease of illustration, the following description uses a car as an example.

[0040] refer to Figure 1The car is equipped with radar 02 around its perimeter. Radar 02 can be used to measure the distance, speed, and azimuth of targets 1a (such as obstacles or pedestrians) around the car, thereby improving the safety of driving and achieving assisted driving. Radar 02 can be lidar, millimeter-wave radar, or ultrasonic radar. This application does not limit the type of radar 02. For ease of illustration, the following description uses millimeter-wave radar as an example.

[0041] The following explains the principle of millimeter-wave radar for ranging, velocity measurement, and azimuth measurement of target 1a (such as obstacles or pedestrians). In some embodiments of this application, Figure 2a The radar 02 shown includes an antenna 20. Antenna 20 includes a transmitting antenna 21 and a receiving antenna 22. There are multiple transmitting antennas 21, which are typically arranged side-by-side. Similarly, there are multiple receiving antennas 22, which are typically arranged side-by-side, meaning they are parallel to each other. The number of transmitting antennas 21 and receiving antennas 22 may be the same or different. The transmitting antenna 21 can transmit millimeter waves to the outside world; for ease of description, the millimeter waves transmitted by the transmitting antenna 21 are referred to as transmitted millimeter waves S1. The receiving antenna 22 can receive millimeter waves reflected back from the outside world; for ease of description, the millimeter waves received by the receiving antenna 22 are referred to as reflected millimeter waves S2.

[0042] Figure 1 The radar 02 shown can continuously transmit millimeter waves S1 to a target 1a (such as an obstacle or pedestrian). Then, radar 02 receives reflected millimeter waves S2 returned from the target 1a. In this case, the time difference between the transmitted millimeter waves S1 and the reflected millimeter waves S2 is the flight time of the millimeter waves. The distance of the target 1a relative to radar 02 is obtained by detecting the flight time of the millimeter waves.

[0043] Alternatively, in some other embodiments of this application, the radar 02 can also obtain the speed of the target object 1a relative to the radar 02 by calculating the frequency change between the reflected millimeter wave S2 and the transmitted millimeter wave S1 based on the Doppler effect.

[0044] Alternatively, in some other embodiments of this application, the radar 02 can also calculate the azimuth angle of the target 1a relative to the radar 02 by receiving the phase difference of the reflected millimeter wave S2 returned by the same target 1a through the parallel receiving antennas 22.

[0045] Radar 02 provides information on the distance, speed, and azimuth of target 1a, thereby assisting the driver or unmanned driving system in making judgments and achieving the goal of safe driving.

[0046] For details, please refer to Figure 1The radar 02 can be installed at the front, rear, or side of the vehicle. This application does not limit the installation location of the radar 02 on the vehicle. Drivers typically pay more attention to targets 1a in front of or behind the vehicle, such as other vehicles. In this case, the radar 02 can be installed at the front or rear of the vehicle, with its orientation directly facing the target 1a. Thus, the vehicle itself obstructs the radar 02 relatively little. The emitted millimeter wave S1 can propagate directly to the target 1a, resulting in a high-quality reflected millimeter wave S2 signal, thereby improving the resolution of the radar 02.

[0047] It should be noted that the above description is based on the example of radar 02 being installed inside a vehicle. In other embodiments of this application, radar 02 can also be installed in security inspection equipment to determine the distance to the object being inspected, or installed in imaging equipment to determine the distance to the object being imaged.

[0048] The structure of the aforementioned radar 02 is illustrated below with an example. The example is as follows: Figure 2b The radar 02 may include a housing 021 and a circuit board assembly 022, with the circuit board assembly 022 disposed within the housing 021. The circuit board assembly 022 is a crucial component of the radar 02, primarily used for transmitting and receiving millimeter waves. The housing 021 provides mounting space for the circuit board assembly 022. The housing 021 includes a cavity within which the circuit board assembly 022 is housed. The entire radar 02 can be mounted on a target device, such as security inspection equipment or a vehicle, via the housing 021.

[0049] The specific structure of the circuit board assembly 022 provided in the embodiments of this application is referred to... Figure 3a The aforementioned circuit board assembly 022 may include a circuit board 10, at least one antenna 20, at least two radio frequency (RF) chips, and a first cover layer 50. The circuit board 10 includes a multilayer core board 11 and a wiring layer 12 disposed between adjacent core board layers 11. The wiring layer 12 includes multiple first transmission lines 13 and multiple second transmission lines 14; wherein any two first transmission lines 13 are of the same length, and any two second transmission lines 14 are of the same length. At least two RF chips are disposed on the circuit board 10, namely a first RF chip 30 and a second RF chip 40. Figure 3a The two ends of the first transmission line 13 are electrically connected to the antenna 20 and the first radio frequency chip 30, respectively, and the first transmission line 13 is used to transmit a first radio frequency signal between the antenna 20 and the first radio frequency chip 30. The two ends of the second transmission line 14 are electrically connected to the antenna 20 and the second radio frequency chip 40, respectively, and the second transmission line 14 is used to transmit a second radio frequency signal between the antenna 20 and the second radio frequency chip 40.

[0050] Furthermore, a first cover layer 50 is disposed on the circuit board 10 and covers multiple first transmission lines 13. The relative permittivity of the first cover layer 50 is linearly related to the transmission speed of the first radio frequency signal, such that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is equal to the length ratio of the first transmission line 13 to the second transmission line 14.

[0051] Reference Figure 4 The circuit board 10 includes multiple cores 11. A circuit layer 12 can be disposed between any two adjacent cores 11, for example, between the outermost core 11 and its adjacent core 11. The circuit layer 12 can include multiple first transmission lines 13 and multiple second transmission lines 14, each first transmission line 13 having the same length. Each second transmission line 14 having the same length. The number of first transmission lines 13 and second transmission lines 14 can be the same or different.

[0052] It should be noted that the length of the transmission line refers to its actual length, that is, the length of the transmission line along the actual wiring path, and not the straight-line distance between the two ends of the transmission line after wiring. For example... Figure 3e As shown, the transmission line is routed in an "S" shaped path. The straight-line distance L1 between the first and last ends of the transmission line is 0.35 cm, and the length of the transmission line along the "S" shaped path is 0.5 cm. Therefore, according to the definition of the embodiments of this application, the length of the transmission line is 0.5 cm.

[0053] The circuit board assembly 022 also includes an antenna 20, which can be disposed between two adjacent core board layers 11, similar to the circuit layer 12. The antenna 20 can be a transmitting antenna 21 or a receiving antenna 22.

[0054] Each antenna 20 can be configured with multiple interfaces, for example, Figure 3a The diagram shows six interfaces, T1, T2, T3, T4, T5, and T6. Each interface connects to either the first transmission line 13 or the second transmission line 14. Radio frequency (RF) chips, such as the first RF chip 30 and the second RF chip 40, are mounted on the circuit board 10. If the RF chip is large, it can be mounted on the surface of the outermost core board 11. Alternatively, if the RF chip is small, a mounting slot can be provided in the core board 11 to embed the RF chip. The first RF chip 30 and the second RF chip 40 can be two chips connected in parallel, also known as cascaded chips. The number of RF chips is not limited to two; it can be more, such as three, four, five, etc. When the number of RF chips is greater, the other RF chips besides the first RF chip 30 and the second RF chip 40 can be named the third RF chip, the fourth RF chip, and so on.

[0055] The first RF chip 30 may also have an interface, for example, such as Figure 3a The three interfaces B1, B2, and B3 shown are connected by a first transmission line 13, which connects one interface of the antenna 20 to one interface of the first RF chip 30, transmitting the first RF signal between the antenna 20 and the first RF chip 30. The second RF chip 40 may also have an interface, for example, as shown in... Figure 3a The three interfaces shown are A1, A2, and A3. The second transmission line 14 connects to one interface of the antenna 20 and one interface of the second RF chip 40, transmitting the first RF signal between the antenna 20 and the first RF chip 30. Each first transmission line 13 connected to the antenna 20 serves as one RF channel, and similarly, each second transmission line 14 connected to the antenna 20 also serves as one RF channel.

[0056] Thus, the circuit board assembly 022, through the cascading of multiple RF chips, includes a large number of RF channels, exceeding the number of RF channels in a one-dimensional radar (a radar with only one RF chip). Therefore, the radar 02 including this circuit board assembly 022 has the basis for high-resolution angle measurement capability. Some radars 02, such as millimeter-wave radars, calculate the azimuth angle of the target object 1a relative to the radar 02 by measuring the phase difference of the reflected millimeter waves S2 returned by the same target object 1a received by parallel receiving antennas 22. Therefore, it is necessary to ensure that the transmission phase of each antenna 20 to the transmission line is the same within a certain bandwidth, so that the millimeter-wave signal does not generate a phase difference on the transmission line. In related technologies, this is usually achieved by geometrically equalizing the transmission lines corresponding to each antenna 20 channel. Compared with this technology, this application ensures that the transmission phase of the antenna 20 to the transmission line is the same by adjusting the transmission speed of the first RF signal through the first covering layer 50. Therefore, it overcomes the limitation of the same wiring length.

[0057] It should be noted that the circuit board assembly 022 of this embodiment is not only applicable to millimeter-wave radar, but also to other radars 02 that require equal phase of each transmission line. For ease of description, this embodiment will be described using the circuit board assembly 022 applicable to millimeter-wave radar as an example.

[0058] In this embodiment, the transmission speed of the first radio frequency signal is adjusted by the first cover layer 50 so that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is equal to the length ratio of the first transmission line 13 to the second transmission line 14, thereby ensuring that the transmission phase from the antenna 20 to the transmission line is the same.

[0059] Antenna 20 mentioned here can be either transmitting antenna 21 or receiving antenna 22. Taking transmitting antenna 21 as an example, this explanation illustrates how to determine the relative permittivity of the cladding layer. (Refer to...) Figure 5At least one antenna 20 includes a transmitting antenna 21. Multiple first transmission lines 13 include multiple first transmitting transmission lines 131. The two ends of each first transmitting transmission line 131 are electrically connected to the transmitting antenna 21 and the first radio frequency chip 30, respectively. Multiple second transmission lines 14 include multiple second transmitting transmission lines 141, the two ends of each second transmitting transmission line 141 being electrically connected to the transmitting antenna 21 and the second radio frequency chip 40, respectively. The length ratio of the first transmitting transmission line 131 to the second transmitting transmission line 141 is n1, and the speed ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n1, where n1 > 0.

[0060] In this embodiment, by providing a first covering layer 50 on the first transmission line 131, the transmission speed of the first radio frequency signal on the first transmission line 131 is adjusted so that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n1. This ratio is equal to the length ratio of the first transmission line 131 to the second transmission line 141. Thus, the phase from the transmitting antenna 21 to the first transmission line 131 and the second transmission line 141 is the same, ensuring that the millimeter-wave signal does not generate a phase difference when it is transmitted from the transmitting antenna 21, thereby improving the high-resolution angle measurement capability of the corresponding radar 02. Specifically, the method for determining the relative permittivity of the covering layer is as follows: Figure 3g As shown, it includes steps S101 to S105.

[0061] S101, determine the transmission line length ratio.

[0062] The transmitting antenna 21 has six interfaces: T1, T2, T3, T4, T5, and T6. The second RF chip 40 has three interfaces: A1, A2, and A3, and the first RF chip 30 has three interfaces: B1, B2, and B3. A first transmitting line 131 connects interfaces T4 and B1, and its length is LA. A second transmitting line 141 connects interfaces T1 and A1, and its length is LB. The length ratio η of the first transmitting line 131 and the second transmitting line 141 is defined as:

[0063] η=LA / LB (1)

[0064] S102 simulates the wave velocity of a transmission line under different relative permittivity of the covering layers.

[0065] The surface of a transmission line is covered with a coating layer. The relative permittivity of the coating layer affects the transmission speed of the radio frequency (RF) signal transmitted by the transmission line. RF signals propagate in the form of signal waves, and the transmission speed can also be called wave speed.

[0066] The wave velocity of the transmission line under different cladding layers can be calculated using full-wave electromagnetic simulation software. In this embodiment, the simulation process is as follows: the specifications (such as material, width, etc.) and length LA of the first transmitting transmission line 131 are determined. The wave velocity of the first transmitting transmission line 131 under different first cladding layers 50 is simulated using full-wave electromagnetic simulation software, and the wave velocity is normalized relative to the speed of light. Based on the scattered data obtained from the simulation, the ratio of wave velocity to the speed of light is used as the vertical axis, and the relative permittivity is used as the horizontal axis, establishing a... Figure 3b The wave velocity-relative permittivity relationship curve is shown.

[0067] S103, establish the mapping relationship between wave velocity and relative permittivity.

[0068] Through observation Figure 3b The curve shape revealed a possible linear relationship between wave speed and relative permittivity. Linear fitting was performed on the scattered data obtained from the simulation to obtain a linear graph of the wave speed-relative permittivity relationship. In this graph, the horizontal axis represents the ratio of wave speed to light speed, and the vertical axis represents the relative permittivity. Specifically, the wave speed and relative permittivity are negatively correlated. That is, the transmission speed of the first radio frequency signal can be adjusted by setting different relative permittivity values ​​for the first cover layer 50, and after determining the target transmission speed of the first radio frequency signal, it can be further adjusted by... Figure 3c The relative permittivity of the corresponding first cover layer 50 is queried to guide the setting of the first cover layer 50.

[0069] S104, calculate the relative permittivity of the capping layer.

[0070] Assuming the second radio frequency signal comes from, for example Figure 3a The time required for the electromagnetic waves output from port A1 of the second RF chip 40 to reach antenna 20 T1 is Tb, and the time required for them to reach antenna 20 T4 from port B1 of the first RF chip 30 is Ta. Ta and Tb satisfy: Ta = LA / Va, Tb = LB / Vb, respectively. To ensure that the time delays of the electromagnetic waves output from each chip reaching antenna 20 are equal, Ta should equal Tb. That is:

[0071] Va / Vb=LA / LB (2)

[0072] Since the second RF chip 40 has no overlay layer, Vb is a fixed value. Then, according to equations (1)-(2), Vb = Va / η can be obtained, and the specific value of Va can be calculated. After obtaining the specific value of Va, it is possible to... Figure 4 In this process, the relative permittivity of the corresponding capping layer is found. For example, in one embodiment, for a 77 GHz microstrip transmission line, Vb has a value of 0.637. When η = 1.36, Va = 0.425, and the relative permittivity of the corresponding capping layer is approximately 10.

[0073] S105, conduct simulation to verify the results.

[0074] Based on the above calculation results, the transmission phase of each transmission line can be obtained in full-wave electromagnetic simulation software. Figure 3a Taking the transmission phase from chip A1 port of the first RF chip 30 to antenna T1 20 and from chip B1 port to antenna T4 20 as an example, the results are illustrated. Since the cases for other transmission paths are similar, they will not be repeated here. The full-wave simulation results are as follows: Figure 3d As shown, this method can guarantee that the transmission phases of two transmission lines of unequal length (length ratio η = 1.36) are the same, with an error within 1°.

[0075] It should be noted that the circuit board assembly in this embodiment has excellent broadband electrical equal-length transmission characteristics. The most commonly used signal system in millimeter-wave radar is the FMCW (Frequency Modulated Continuous Wave) waveform. FMCW millimeter-wave radar periodically transmits chirp signals. Chirp signals can also be called linear frequency modulated signals; the signal frequency increases linearly and has a certain bandwidth, such as... Figure 3f As shown. According to the principle of FMCW millimeter-wave radar, its ranging accuracy ΔR will depend on the bandwidth of the Chirp signal, as shown in equation (3):

[0076] ΔR=c / 2B (3)

[0077] As shown in the above formula, the larger the signal bandwidth, the higher the ranging accuracy. In this case, it is crucial that the millimeter-wave radar RF transmission line maintains equal transmission phase across the wide bandwidth. The cladding electrical equal-length scheme described in this application embodiment can provide excellent wideband equal-phase transmission. Figure 3b The wave velocity-frequency curves of transmission lines A1-T1 and A4-T4 were calculated. It can be seen that their wave velocity remains stable within a bandwidth of 77-80 GHz. This also explains... Figure 3d The wideband equal-phase transmission characteristics of the circuit board, with a bandwidth of 3GHz, are higher than the typical bandwidth (~1GHz) of currently commercially available millimeter-wave radars. Applying this circuit board assembly to the design of millimeter-wave radar can help improve radar resolution.

[0078] In summary, in the circuit board assembly 022 of this application embodiment, the transmission speed of the first radio frequency signal is adjusted by the first cover layer 50, such that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is equal to the length ratio of the first transmission line 13 to the second transmission line 14, thereby ensuring that the transmission phase from the antenna 20 to the transmission line is the same. Therefore, when routing the first transmission line 13 and the second transmission line 14, there is no need to consider the limitation of the same routing length. While meeting the requirements of routing space and position, the routing of the first transmission line 13 and the second transmission line 14 can be arranged into a regular straight line shape as much as possible. That is, in some embodiments, the first transmission line and the second transmission line include straight line segments, and in other embodiments, the first transmission line and the second transmission line include straight line segments. Therefore, the routing of the first transmission line 13 and the second transmission line 14 is simple, reducing the development cycle and development difficulty of the radar 02, and the shortening of the line length of the first transmission line 13 and the second transmission line 14 also brings lower transmission loss. Furthermore, the fact that the first transmission line 13 and the second transmission line 14 are mostly different reduces the probability of insertion loss, inter-channel coupling, and dispersion problems caused by equal-length wiring, thereby improving the performance of the circuit board assembly 022. It should be noted that when wiring space is limited or it is necessary to avoid other components, the corresponding parts of the first transmission line 13 and the second transmission line 14 can also be provided with bent sections.

[0079] The above example illustrates how to determine the relative permittivity of the first cladding layer 50, using antenna 20 as the transmitting antenna 21. In other embodiments of this application, refer to... Figure 5 Alternatively, taking antenna 20 as an example of receiving antenna 22, the relative permittivity of the first covering layer 50 can be determined. In this case, the determination method is the same as... Figure 3g The method shown will not be elaborated further here.

[0080] In this embodiment, reference is made to Figure 5 At least one antenna 20 includes a receiving antenna 22; multiple first transmission lines 13 also include multiple first receiving transmission lines 132, the two ends of which are electrically connected to the receiving antenna 22 and the first radio frequency chip 30, respectively; multiple second transmission lines 14 also include multiple second receiving transmission lines 142, the two ends of which are electrically connected to the receiving antenna 22 and the second radio frequency chip 40, respectively; the length ratio of the first receiving transmission line 132 to the second receiving transmission line 142 is n2, and the speed ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n2, where n2 > 0.

[0081] In this embodiment, a first cover layer 50 can also be provided on the first receiving transmission line 132 to adjust the transmission speed of the first radio frequency signal on the first receiving transmission line 132, so that the speed ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n2. This speed ratio is equal to the length ratio of the first receiving transmission line 132 and the second receiving transmission line 142. In this way, the phase of the receiving antenna 22 to the first receiving transmission line 132 and the second receiving transmission line 142 is the same, so that the received millimeter wave signal does not generate a phase difference during transmission to the corresponding radio frequency chip, thereby improving the high-resolution angle measurement capability of the corresponding radar 02. The method for determining the relative permittivity of the cover layer is similar to that described above. Figure 3g As shown.

[0082] The above example uses the first transmitting line 131 or the first receiving transmitting line 132 to set the first cover layer 50. In other embodiments of this application, refer to... Figure 6 Alternatively, in addition to setting the first cover layer 50, a second cover layer 60 can also be set on the second transmit transmission line 141 or the second receive transmission line 142.

[0083] In this embodiment, reference is made to Figure 6 The circuit board assembly 022 also includes a second cover layer 60, which is disposed on the circuit board 10 and covers multiple second transmission lines 14. The relative permittivity of the second cover layer 60 is linearly related to the transmission speed of the second radio frequency signal, such that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is equal to the length ratio of the first transmission line 13 to the second transmission line 14. The relative permittivity of the first cover layer 50 and the second cover layer 60 are different.

[0084] The relative permittivity of the second cover layer 60 is linearly related to the transmission speed of the second radio frequency signal. The transmission speed of the second radio frequency signal can be adjusted by selecting second cover layers 60 with different relative permittivity. The method for determining the relative permittivity of the second cover layer 60 can refer to the method for determining the relative permittivity of the first cover layer 50. In this embodiment, the transmitting antenna 21 is taken as an example. After the wiring scheme of the first transmitting transmission line 131 and the second transmitting transmission line 141 is determined, the length ratio of the first transmitting transmission line 131 to the second transmitting transmission line 141 is determined. Using methods such as... Figure 3g The method described above determines the transmission speed of the first radio frequency signal after determining the relative permittivity of the first cover layer 50, and the transmission speed of the second radio frequency signal can also be obtained. The first cover layer 50 can be selected based on its relative permittivity. Then, methods such as... Figure 3gThe method described herein uses full-wave electromagnetic simulation software to simulate the wave velocity of the second transmitting transmission line 141 under different cover layers. Based on the scattered data obtained from the simulation, a wave velocity-relative permittivity relationship curve is established, and a mapping relationship between wave velocity and relative permittivity is established on this basis. According to this mapping relationship, the relative permittivity of the second cover layer 60 corresponding to the transmission speed of the second radio frequency signal is obtained, so as to guide and set the second cover layer 60.

[0085] In this way, the transmission speeds of the first radio frequency (RF) signal on the first transmission line 131 and the second RF signal on the second transmission line 141 can be adjusted simultaneously, so that the ratio of the transmission speeds of the first RF signal and the second RF signal is n1, which is equal to the length ratio of the first transmission line 131 and the second transmission line 141. Therefore, the phase of the transmitting antenna 21 to the first transmission line 131 and the second transmission line 141 is the same, which prevents phase difference from occurring during the transmission of the millimeter-wave signal, thereby improving the high-resolution angle measurement capability of the corresponding radar 02. Furthermore, adjusting from both the transmission speeds of the first and second RF signals simultaneously makes the adjustment method more flexible and precise, adaptable to more complex wiring requirements.

[0086] The above example illustrates how a first covering layer 50 and a second covering layer 60 are respectively provided on the first transmission line 131 and the second transmission line 141, using antenna 20 as the transmitting antenna 21. In other embodiments of this application, refer to... Figure 7 Alternatively, taking antenna 20 as the receiving antenna 22 as an example, this illustrates how to set the first covering layer 50 and the second covering layer 60 on the first receiving transmission line 132 and the second receiving transmission line 142, respectively. The specific method is the same as the method for determining the transmitting antenna 21, and will not be repeated here.

[0087] Of course, refer to Figure 8 In other embodiments, when a first cover layer 50 is provided on the first receiving transmission line 132 and a second cover layer 60 is provided on the second receiving transmission line 142, a first cover layer 50 may also be provided on the first transmitting transmission line 131 and a second cover layer 60 may be provided on the second transmitting transmission line 141. The method for determining the relative permittivity of each cover layer is similar to... Figure 3g As shown, no further details will be provided.

[0088] Thus, on the one hand, the transmission speed of the first radio frequency signal on the first transmission line 131 and the transmission speed of the second radio frequency signal on the second transmission line 141 can be adjusted simultaneously, so that the ratio of the transmission speeds of the first and second radio frequency signals is n1, which is equal to the length ratio of the first and second transmission lines 131. Therefore, the phase of the transmitting antenna 21 to the first and second transmission lines 131 is the same, which prevents the millimeter-wave signal from generating a phase difference during transmission, thereby improving the high-resolution angle measurement capability of the corresponding radar 02.

[0089] On the other hand, the transmission speed of the first radio frequency signal on the first receiving transmission line 132 and the transmission speed of the second radio frequency signal on the second receiving transmission line 142 can be adjusted simultaneously so that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n1, which is equal to the length ratio of the first receiving transmission line 132 and the second receiving transmission line 142. Therefore, the phase of the transmitting antenna 21 to the first receiving transmission line 132 and the second receiving transmission line 142 is the same, which prevents the millimeter-wave signal from generating a phase difference during reception, thereby improving the high-resolution angle measurement capability of the corresponding radar 02.

[0090] In this way, under the combined effect of the two aspects, when wiring the first transmitting transmission line 131, the second transmitting transmission line 141, the first receiving transmission line 132 and the second receiving transmission line 142, there is no need to consider the limitation of the same wiring length. This can adapt to more complex wiring requirements, and adjustments can be made simultaneously from both the transmission speed of the first radio frequency signal and the transmission speed of the second radio frequency signal, making the adjustment method more flexible and precise.

[0091] Optionally, the first covering layer 50 partially or completely covers the first transmission line 13 along its extension direction, and the second covering layer 60 partially or completely covers the second transmission line 14 along its extension direction. As long as the first covering layer 50 partially covers the first transmission line 13 along its extension direction, it will affect the transmission speed of the first radio frequency signal; therefore, there are no specific restrictions on the specific coverage method of the first covering layer 50. Similarly, there are no specific restrictions on the specific coverage method of the second covering layer 60.

[0092] Optionally, the first cover layer 50 and the second cover layer 60 are disposed on the same layer. In this way, the first cover layer 50 and the second cover layer 60 can be manufactured simultaneously, or one can be manufactured after the other is completed, thus making the manufacturing process more convenient.

[0093] Alternatively, the core board 11 may be made of the same material as the first cover layer 50. This simplifies the process by using the same materials to manufacture both the core board 11 and the first cover layer 50.

[0094] Optionally, the first transmission line 13 and the second transmission line 14 are microstrip transmission lines, coplanar waveguide transmission lines, or grounded coplanar waveguide transmission lines. The transmission losses of these types of transmission lines are relatively low, thereby improving the resolution of radar 02.

[0095] Optionally, the first transmission line 13 and the second transmission line 14 are located on the same circuit layer 12. This allows for the simultaneous fabrication of the first transmission line 13 and the second transmission line 14 on the same layer, resulting in faster fabrication. This is especially true when the materials used for the first transmission line 13 and the second transmission line 14 are identical, enabling even faster fabrication.

[0096] Optionally, the first transmission line 13 and the second transmission line 14 are made of the same material, width, and thickness. The material, width, and thickness will affect the transmission speed of the radio frequency signal to a certain extent. At least one of the material, width, and thickness is the same, so as to minimize the impact of the difference between the first transmission line 13 and the second transmission line 14 on the transmission speed of the radio frequency signal, so as to adjust the transmission speed of the radio frequency signal through the overlay layer.

[0097] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A circuit board assembly, characterized in that, include: A circuit board, the circuit board comprising a multilayer core board and a circuit layer disposed between two adjacent core boards; the circuit layer comprising a plurality of first transmission lines and a plurality of second transmission lines; wherein any two first transmission lines are of the same length and any two second transmission lines are of the same length. At least one antenna; At least two radio frequency (RF) chips are disposed on the circuit board, namely a first RF chip and a second RF chip; the two ends of the first transmission line are electrically connected to the antenna and the first RF chip respectively, and the first transmission line is used to transmit a first RF signal between the antenna and the first RF chip; the two ends of the second transmission line are electrically connected to the antenna and the second RF chip respectively, and the second transmission line is used to transmit a second RF signal between the antenna and the second RF chip; the first transmission line and the second transmission line include straight segments; and the lengths of the first transmission line and the second transmission line are different; A first cover layer is disposed on the circuit board and covers the plurality of first transmission lines; wherein, the relative permittivity of the first cover layer satisfies a first condition, the first condition being that the relative permittivity of the first cover layer is linearly related to the transmission speed of the first radio frequency signal, and such that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is equal to the ratio of the length of the first transmission line to the length of the second transmission line.

2. The circuit board assembly according to claim 1, characterized in that, The circuit board assembly also includes: A second cover layer is disposed on the circuit board and covers the plurality of second transmission lines; wherein, the relative permittivity of the second cover layer satisfies a second condition, the second condition being that the relative permittivity of the second cover layer is linearly related to the transmission speed of the second radio frequency signal, and such that the ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is equal to the ratio of the length of the first transmission line to the length of the second transmission line; the relative permittivity of the first cover layer and the second cover layer are different.

3. The circuit board assembly according to claim 1, characterized in that, The at least one antenna includes a transmitting antenna; The plurality of first transmission lines include a plurality of first transmission transmission lines, the two ends of which are electrically connected to the transmitting antenna and the first radio frequency chip, respectively. The plurality of second transmission lines include a plurality of second transmission transmission lines, the two ends of which are electrically connected to the transmitting antenna and the second radio frequency chip, respectively; The length ratio of the first transmission line to the second transmission line is n1, and the speed ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n1, where n1 > 0.

4. The circuit board assembly according to claim 1, characterized in that, The at least one antenna further includes a receiving antenna; The plurality of first transmission lines also include a plurality of first receiving transmission lines, the two ends of which are electrically connected to the receiving antenna and the first radio frequency chip, respectively. The plurality of second transmission lines also include a plurality of second receiving transmission lines, the two ends of which are electrically connected to the receiving antenna and the second radio frequency chip, respectively. The length ratio of the first receiving transmission line to the second receiving transmission line is n2, and the speed ratio of the transmission speed of the first radio frequency signal to the transmission speed of the second radio frequency signal is n2, where n2 > 0.

5. The circuit board assembly according to claim 2, characterized in that, The first cover layer and the second cover layer are disposed on the same layer.

6. The circuit board assembly according to claim 1, characterized in that, The core board is made of the same material as the first cover layer.

7. The circuit board assembly according to claim 1, characterized in that, The first transmission line and the second transmission line are microstrip transmission lines, coplanar waveguide transmission lines, or grounded coplanar waveguide transmission lines.

8. The circuit board assembly according to any one of claims 1 to 7, characterized in that, The first transmission line and the second transmission line are located in the same line layer.

9. The circuit board assembly according to any one of claims 1 to 7, characterized in that, The first transmission line and the second transmission line have at least one of the same material, width and thickness.

10. A radar, characterized in that, The radar includes: case; The circuit board assembly according to any one of claims 1 to 9 is disposed within the housing.

11. A vehicle, characterized in that, The vehicle includes a body and a radar as described in claim 10 disposed on the body.

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