Millimeter wave antenna and millimeter wave radar

Abstract

The invention discloses a millimeter wave antenna and a millimeter wave radar, and relates to the technical field of in-vehicle monitoring, and the millimeter wave antenna comprises a grounding layer, a base layer and a radiation structure. The grounding layer is used for being laid or embedded in the ground. The base layer is stacked above the grounding layer, in the vertical direction, the middle position of the base layer is partially hollowed out to form a hollowed-out position, and the hollowed-out position is used for containing the grounding part; the radiation structure is arranged right above the base layer, the radiation structure comprises a feed layer, a plurality of feeder lines and a plurality of antennas, the feed layer is arranged above the base layer and is located right above the hollow position, each feeder line is at least partially embedded into the feed layer, the plurality of antennas are correspondingly and electrically connected with the plurality of feeder lines, and each antenna and the hollow position are arranged in a staggered manner in the horizontal direction; wherein the feed layer is provided with a plurality of via holes around each feed line, and each via hole penetrates through the feed layer and a part of the base layer and is used for being electrically connected with the grounding part; according to the technical scheme provided by the invention, the antenna has larger antenna bandwidth while facilitating layout.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and in particular to a millimeter wave antenna and a millimeter wave radar. Background Art

[0002] With the continuous development of fifth-generation communication technology, the millimeter wave band (mm-waveband) has gradually entered people's field of vision and derived many new technologies. The millimeter wave band has ultra-wide bandwidth, lower latency, and higher unlimited transmission speed, and is mostly used in the field of vehicle-mounted radar monitoring. Millimeter wave radars mostly use a multi-layer PCB (Printed Circuit Board) structure design, which is divided into the top antenna layer and the device layer.

[0003] Faced with the complex environment inside the car, most of the existing in-vehicle detection radar antennas are designed with microstrip antennas and adopt the MIMO form of multiple transmission and multiple reception. Since the theoretical bandwidth of the microstrip antenna is not large, only about 5-8%, it cannot meet the accuracy requirements required by the millimeter-wave radar during detection. Therefore, an array form is often used to increase the bandwidth of the antenna. However, for the small and compact radar installed in the car, the use of an array antenna is a great challenge for the PCB with a small board size, which greatly increases the difficulty of the layout of other devices.

[0004] Therefore, how to increase the bandwidth of the antenna while reducing the difficulty of layout of other devices has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] The main purpose of the present invention is to propose a millimeter wave antenna and a millimeter wave radar, aiming to reduce the difficulty of layout of other devices while increasing the bandwidth of the antenna.

[0006] To achieve the above-mentioned purpose, the millimeter wave antenna proposed in the present invention includes a ground layer, a base layer and a radiation structure; the ground layer is used to be laid or embedded in the ground; the base layer is stacked on the ground layer, and in the up and down directions, the middle position of the base layer is partially hollowed out to form a hollow position, and the hollow position is used to accommodate the grounding part; the radiation structure is located directly above the base layer, and the radiation structure includes a feed layer, multiple feed lines and multiple antennas, the feed layer is stacked on the base layer and is located directly above the hollow position, each feed line is at least partially embedded in the feed layer, and the multiple antennas are electrically connected to the multiple feed lines correspondingly, and each antenna is staggered with the hollow position in the horizontal direction; wherein, the feed layer is provided with multiple vias around each feed line, and each via penetrates the feed layer and a part of the base layer for electrical connection with the grounding part.

[0007] In one embodiment, the base layer includes a first dielectric layer, a second dielectric layer and at least one intermediate dielectric layer; the first dielectric layer is used to be arranged below the ground portion and in contact with the ground layer; the second dielectric layer is used to be arranged above the ground portion and attached to the bottom of the feed layer, the second dielectric layer is used to integrate the circuit structure of the millimeter wave antenna and is penetrated by vias; the intermediate dielectric layer is arranged between the first dielectric layer and the second dielectric layer and is located below multiple antennas to form a hollow position at the ground portion with the first dielectric layer and the second dielectric layer.

[0008] In one embodiment, the effective dielectric constant of the second dielectric layer and the first dielectric layer is ε, 3.8≤ε≤4.2.

[0009] In one embodiment, the dielectric constants of the first dielectric layer, the second dielectric layer, and the intermediate dielectric layer are the same.

[0010] In one embodiment, the material of the first dielectric layer includes a first semi-solid sheet, the material of the second dielectric layer includes a second semi-solid sheet, and the intermediate dielectric layer is formed by extruding the first semi-solid sheet and the second semi-solid sheet.

[0011] In one embodiment, projections of the first dielectric layer, the second dielectric layer, and the ground layer in the up-down direction overlap.

[0012] In one embodiment, the material of the feed layer includes at least one of copper and copper-aluminum composite material.

[0013] In one embodiment, the distance between every two adjacent antennas is d, the wavelength of the electromagnetic waves emitted by the antennas is λ, and d=λ / 2.

[0014] In one embodiment, among the multiple antennas, some of the antennas are used to transmit electromagnetic waves, and another part of the antennas are used to receive electromagnetic waves, and the multiple antennas are arranged in an array.

[0015] The present invention also proposes a millimeter wave radar, which includes a millimeter wave antenna and a radome, wherein the millimeter wave antenna includes a grounding layer, a base layer and a radiation structure; the grounding layer is used to be laid or embedded in the ground; the base layer is stacked above the grounding layer, and in the up and down directions, the middle position of the base layer is partially hollowed out to form a hollow position, and the hollow position is used to accommodate the grounding part; the radiation structure is located directly above the base layer, and the radiation structure includes a feed layer, multiple feed lines and multiple antennas, the feed layer is stacked above the base layer and is located directly above the hollow position, each feed line is at least partially embedded in the feed layer, and the multiple antennas are electrically connected to the multiple feed lines correspondingly, and each antenna is staggered with the hollow position in the horizontal direction; wherein the feed layer is provided with multiple vias around each feed line, each via hole penetrates the feed layer and a part of the base layer to be electrically connected to the grounding part, and the radome is provided on the millimeter wave antenna.

[0016] The feed layer beside the feed line of the present invention is provided with a via, and the via is electrically connected to the ground part. In this way, the ground part is used as a reference ground, and the hollowed-out base layer forms a thinner dielectric substrate of the feed line. The thickness of the dielectric substrate of the feed line is the distance from the top of the hollowed-out position to the top of the feed layer. Therefore, the via size can be smaller, which is convenient for the layout of the circuit structure, and the ground can be used as a reference ground to form a thicker dielectric substrate of the antenna component. The thickness of the dielectric substrate of the antenna component is the distance from the top of the feed layer to the ground layer. In this way, the reference grounds set at intervals and the thicker dielectric substrate of the antenna component make it convenient to layout the millimeter wave antenna while having a larger antenna bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0018] Figure 1 A schematic structural diagram of an embodiment of a millimeter wave antenna provided by the present invention;

[0019] Figure 2 for Figure 1 A top view of the mid-millimeter wave antenna;

[0020] Figure 3 A comparison diagram of S parameters of an embodiment of a millimeter wave antenna provided by the present invention;

[0021] Figure 4 The antenna pattern of an embodiment of the millimeter wave radar provided by the present invention.

[0022] Description of Figure Numbers:

[0023] 100. Millimeter wave antenna; 1. Ground layer; 2. Base layer; 21. First dielectric layer; 22. Second dielectric layer; 23. Intermediate dielectric layer; 2A. Hollow position; 3. Radiating structure; 31. Feed line; 32. Antenna; 33. Feed layer.

[0024] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0027] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] Faced with the complex environment inside the car, most of the existing in-vehicle detection radar antennas are designed with microstrip antennas and adopt the MIMO form of multiple transmission and multiple reception. Since the theoretical bandwidth of the microstrip antenna is not large, only about 5-8%, it cannot meet the accuracy requirements required by the millimeter-wave radar during detection. Therefore, an array form is often used to increase the bandwidth of the antenna. However, for the small and compact radar installed in the car, the use of an array antenna is a great challenge for the PCB with a small board size, which greatly increases the difficulty of the layout of other devices.

[0029] In the related art, the PCB antenna structure is formed by pressing the top layer, dielectric layer, and ground layer together from top to bottom. The dielectric layer is provided with vias to connect the top layer to the ground. The vias are related to the thickness of the PCB antenna structure. The thicker the dielectric layer, the thicker the PCB antenna structure of the millimeter-wave radar is, and the larger the aperture of the via. A via that is too large will occupy the space of other circuit structures. Therefore, when selecting the via aperture, it is necessary to consider the component size and pin spacing on the PCB antenna structure. If the component size is small and the pin spacing is tight, then a smaller blind hole aperture is more suitable.

[0030] The thickness of the antenna substrate will directly affect the bandwidth of the antenna. The calculation formula for the antenna bandwidth BW is:

[0031]

[0032] Among them, f 2 , f 1 Respectively represent the highest operating frequency and the lowest operating frequency, f r is represented as the center of the operating frequency. The bandwidth of a microstrip antenna when it resonates can be described by the quality factor Q. The Q factor is the sum of all quality factors associated with the antenna loss, including the power dissipated within the patch due to the lossy metal conductor and substrate, as well as the power loss due to radiation. The bandwidth of the antenna can also be described by the following formula:

[0033]

[0034] in,

[0035] In the formula, h is the thickness of the antenna dielectric substrate, ε r (w) is the effective dielectric constant of the antenna. It can be seen that the purpose of increasing the antenna bandwidth can be achieved by increasing the thickness of the antenna substrate.

[0036] Therefore, if the dielectric layer of the antenna structure is too thick, the via will be too large, thus affecting the layout of the PCB structure; if the dielectric layer is too thin, the bandwidth of the antenna will be relatively small.

[0037] Based on this, the present invention proposes a millimeter wave antenna 100 .

[0038] See also Figure 1 and Figure 2In one embodiment of the present invention, the grounding layer 1 is used for laying or embedding in the ground; the base layer 2 is stacked on the grounding layer 1, and in the up and down direction, the middle position of the base layer 2 is partially hollowed out to form a hollow position 2A, and the hollow position 2A is used to accommodate the grounding part; the radiation structure 3 is arranged directly above the base layer 2, and the radiation structure 3 includes a feeding layer 33, a plurality of feed lines 31 and a plurality of antennas 32, the feeding layer 33 is stacked on the base layer 2 and is located directly above the hollow position 2A, each feed line 31 is at least partially embedded in the feeding layer 33, and the plurality of antennas 32 are electrically connected to the plurality of feed lines 31 correspondingly, and each antenna 32 is staggered with the hollow position 2A in the horizontal direction; wherein, the feeding layer 33 is provided with a plurality of vias around each feed line 31, and each via penetrates the feeding layer 33 and a part of the base layer 2 for being electrically connected to the grounding part.

[0039] The feed layer 33 next to the feed line 31 of the present invention is provided with a via, and the via is electrically connected to the ground part. In this way, the ground part is used as a reference ground, and the hollowed-out base layer 2 forms a thinner dielectric substrate of the feed line 31. The thickness of the dielectric substrate of the feed line 31 is the distance from the top of the hollow position 2A to the top of the feed layer 33. Therefore, the via size can be smaller, which is convenient for the layout of the circuit structure, and a thicker dielectric substrate of the antenna component can be formed with the ground as a reference ground. The thickness of the dielectric substrate of the antenna component is the distance from the top of the feed layer 33 to the ground layer 1. In this way, the reference grounds set at intervals and the thicker dielectric substrate of the antenna component make the millimeter wave antenna 100 convenient for layout while having a larger antenna bandwidth.

[0040] It should be noted that the grounding part is a material used to connect to the ground as a reference ground, and there are many ways to form it. In order to achieve its tight arrangement in the hollow position 2A and facilitate installation, the ground layer of the existing PCB antenna structure can be partially corroded, and the remaining ground layer forms the grounding part, the top layer forms the radiation structure 3, and the dielectric layer forms the upper part of the base layer 2.

[0041] In one embodiment of the present invention, the base layer 2 includes a first dielectric layer 21, a second dielectric layer 22 and at least one intermediate dielectric layer 23; the first dielectric layer 21 is used to be arranged below the grounding portion and in contact with the grounding layer 1; the second dielectric layer 22 is used to be arranged above the grounding portion and attached to the bottom of the feed layer 33, the second dielectric layer 22 is used to integrate the circuit structure of the millimeter wave antenna and is penetrated by vias; the intermediate dielectric layer 23 is arranged between the first dielectric layer 21 and the second dielectric layer 22 and is located below the multiple antennas 32, so as to form a hollow position at the grounding portion with the first dielectric layer 21 and the second dielectric layer 22. In this way, the hollow position 2A can be formed by the first dielectric layer 21, the second dielectric layer 22 and the intermediate dielectric layer 23 of common industrial thickness, and standard plates are used for easy processing; such a layered arrangement can share external pressure, enhance the overall pressure resistance and deformation resistance through a reasonable layered layout, and prevent local deformation or damage of the dielectric layer.

[0042] Specifically, the thickness of the first dielectric layer 21 is set to 0.127 mm, the thickness of the middle dielectric layer is set to 0.035 mm, and the thickness of the second dielectric layer 22 is set to 0.092 mm, that is, the thickness of the dielectric substrate of the feed line 31 is 0.127 mm, and the dielectric substrate of the antenna assembly is 0.254 mm.

[0043] In one embodiment of the present invention, the effective dielectric constant of the second dielectric layer 22 and the first dielectric layer 21 is ε, 3.8≤ε≤4.2. In this way, a relatively stable electric field environment can be provided, the scattering and absorption of electromagnetic energy can be reduced, and the transmission efficiency can be improved.

[0044] Specifically, the material of the base layer 2 may be selected from but not limited to PTFE (polytetrafluoroethylene), epoxy resin, hydrocarbon resin, and other modified materials.

[0045] In one embodiment of the present invention, the first dielectric layer 21 , the second dielectric layer 22 , and the intermediate dielectric layer 23 have the same dielectric constant, which can ensure that the electric field is evenly distributed in the entire region, thereby improving the performance and accuracy of the device.

[0046] In one embodiment of the present invention, the material of the first dielectric layer 21 includes a first semi-solid sheet, the material of the second dielectric layer 22 includes a second semi-solid sheet, and the intermediate dielectric layer 23 is formed by extruding the first semi-solid sheet and the second semi-solid sheet. In this way, the colloidal semi-solid sheet can better fill the gap, thereby improving the performance and precision of the device.

[0047] In one embodiment of the present invention, the projections of the first dielectric layer 21, the second dielectric layer 22 and the ground layer 1 in the vertical direction overlap, so that the overall thickness of the millimeter wave antenna 100 is uniformly set, preventing adverse effects caused by the overall oblique millimeter wave antenna 100.

[0048] In an embodiment of the present invention, the material of the feeding layer 33 includes at least one of copper and a copper-aluminum composite material.

[0049] In one embodiment of the present invention, the interval between every two adjacent antennas 32 is d, and the wavelength of the electromagnetic wave emitted by the antenna 32 is λ, d=λ / 2. Placing multiple antennas 32 at equal intervals along a half wavelength to form an antenna array can achieve higher gain and good directivity, which helps to concentrate the signal in a specific direction for transmission, improve the transmission efficiency and coverage of the signal, and enhance the detection capability and resolution of the target.

[0050] In one embodiment of the present invention, among the multiple antennas 32, some antennas 32 are used to transmit electromagnetic waves, and the other antennas 32 are used to receive electromagnetic waves, and the multiple antennas 32 are arranged in an array. The antennas arranged in an array can realize spatial multiplexing and beamforming, effectively improve the data rate, signal reliability and anti-interference ability, and improve the spectrum efficiency and coverage.

[0051] In one embodiment of the present invention, the material of the grounding layer 1 is a good conductor material. Specifically, the material of the grounding layer 1 is copper. The grounding layer 1 is laid on the ground or in a groove opened on the ground and solidified to form the grounding layer 1.

[0052] In one embodiment of the present invention, for the application scenario of short-range in-vehicle millimeter-wave radar, the antenna operating frequency is designed to be within the 58-64 GHz frequency band, and the MIMO antenna form is used to increase the ranging and angle measurement accuracy of the antenna, and the base layer 2 based on the dielectric constant of about 4 is used. Among them, the thickness of the first dielectric layer 21 is set to 0.127 mm, the thickness of the middle dielectric layer is set to 0.035 mm, and the thickness of the second dielectric layer 22 is set to 0.092 mm, that is, the thickness of the dielectric substrate of the feed line 31 is 0.127 mm, and the dielectric substrate of the antenna assembly is 0.254 mm.

[0053] Comparing the reflection coefficient S of this embodiment with that of the millimeter wave antenna 100 of the same thickness without hollowing out, the following is obtained: Figure 3 The results are shown, where S11 is a one-port reflection coefficient, indicating the matching of the antenna with a transmission line with an impedance of 50 ohms, and the smaller the reflection coefficient, the better; the horizontal axis is the frequency of the antenna, in GHz; the vertical axis is the S11 parameter value of the antenna, in dB; the solid curve represents the S11 parameter of the embodiment, and the dotted line represents the S11 parameter of the millimeter-wave radar that is not hollowed out and has the same thickness; S11≤–10dB, the reflection coefficient is -10dB, indicating that 90% of the incident power is transmitted to the antenna for transmission.

[0054] Depend on Figure 3 It can be seen that the antenna bandwidth of this embodiment is 58-65 GHz, which can greatly increase the antenna bandwidth without changing the antenna layout size.

[0055] Since the antenna is used for in-vehicle detection, the gain requirement is relatively small, but the beam range requirement is relatively large. Therefore, the present invention also proposes a millimeter-wave radar. The specific structure of the millimeter-wave radar refers to the above embodiment. Since the millimeter-wave radar adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here. Among them, the antenna cover is provided on the millimeter-wave antenna 100. In this way, by lowering the maximum gain, the millimeter-wave radar can obtain a larger beam angle, which is conducive to wider range detection in the car.

[0056] Furthermore, the antenna cover is made of PBT material, which has high strength, fatigue resistance, dimensional stability and small creep.

[0057] In one embodiment of the present invention, please refer to Figure 4 , Figure 4 is the directional diagram of the millimeter wave radar. The horizontal axis in the figure is the radiation angle of the radar, in degrees; the vertical axis represents the gain of the radar, in dBi. Direction Figure 1 It is generally a three-dimensional 3D figure in free space. For convenience in engineering, the maximum radiation direction plane is usually used for description. For microstrip antennas, the E-plane and H-plane directional patterns are usually measured. It can be seen that the radar 3dB beam width is 66° in the horizontal direction and 50° in the vertical direction. Since the radar is used for in-vehicle detection, the gain requirement is relatively small, but the beam range requirement is relatively large. By lowering the maximum gain, the antenna can obtain a larger beam angle, which is more conducive to detecting a larger range in the vehicle.

[0058] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A millimeter wave antenna, characterized in that: include: Grounding layer, used for laying or embedding in the ground; A base layer is stacked on the ground layer, and in the up and down direction, the middle position of the base layer is partially hollowed out to form a hollow position, and the hollow position is used to accommodate the grounding part; as well as, A radiation structure is arranged directly above the base layer, the radiation structure comprises a feed layer, a plurality of feed lines and a plurality of antennas, the feed layer is stacked above the base layer and located directly above the hollow position, each of the feed lines is at least partially embedded in the feed layer, the plurality of antennas are electrically connected to the plurality of feed lines correspondingly, and each of the antennas is staggered with the hollow position in the horizontal direction; The feed layer is provided with a plurality of via holes around each feed line, and each via hole penetrates the feed layer and a part of the base layer to be electrically connected to the grounding portion.

2. The millimeter wave antenna according to claim 1, characterized in that: The base layer includes: A first dielectric layer, arranged below the grounding portion and in contact with the grounding layer; a second dielectric layer, which is arranged above the grounding portion and attached to the bottom of the feeding layer, wherein the second dielectric layer is used to integrate the circuit structure of the millimeter wave antenna and is penetrated by the via hole; and At least one intermediate dielectric layer is disposed between the first dielectric layer and the second dielectric layer and is located below the plurality of antennas to form a hollow position at the ground portion with the first dielectric layer and the second dielectric layer.

3. The millimeter wave antenna according to claim 2, characterized in that: The effective dielectric constant of the second dielectric layer and the first dielectric layer is ε, 3.8≤ε≤4.

2.

4. The millimeter wave antenna according to any one of claims 2 to 3, characterized in that: The first dielectric layer, the second dielectric layer and the intermediate dielectric layer have the same dielectric constant.

5. The millimeter wave antenna according to claim 4, characterized in that: The material of the first dielectric layer includes a first semi-solid sheet, the material of the second dielectric layer includes a second semi-solid sheet, and the intermediate dielectric layer is formed by extruding the first semi-solid sheet and the second semi-solid sheet.

6. The millimeter wave antenna according to claim 2, characterized in that: The projections of the first dielectric layer, the second dielectric layer and the ground layer in the up-down direction overlap.

7. The millimeter wave antenna according to claim 1, characterized in that: The material of the feed layer includes at least one of copper and copper-aluminum composite material.

8. The millimeter wave antenna according to claim 1, characterized in that: The distance between every two adjacent antennas is d, the wavelength of the electromagnetic waves emitted by the antennas is λ, and d=λ / 2.

9. The millimeter wave antenna according to claim 1, characterized in that: Among the multiple antennas, some of the antennas are used to transmit electromagnetic waves, and another part of the antennas are used to receive electromagnetic waves, and the multiple antennas are arranged in an array.

10. A millimeter wave radar, characterized in that: include: The millimeter wave antenna according to any one of claims 1 to 9; as well as, The antenna cover is arranged on the millimeter wave antenna.

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