radar sensor

Abstract

Radar sensors are disclosed. A radar sensor includes an antenna layer having antenna elements and a compound radome including an absorber layer on top of the antenna layer and a cover layer on top of the absorber layer. The absorber layer has a higher electromagnetic absorption than the cover layer. The compound radome includes a primary region in which the absorber layer has a reference absorber thickness and the cover layer has a reference cover thickness, and a secondary region in which the absorber layer has a secondary absorber thickness and the cover layer has a secondary cover thickness. The secondary cover thickness is different than the reference cover thickness. For a first angle of incidence, electromagnetic reflectivity is at a minimum within the primary region, and for a second angle of incidence different than the first angle of incidence, electromagnetic reflectivity is at a minimum within the secondary region.

Description

Technical Field

[0001] This disclosure relates to a radar sensor including an antenna layer and a composite radome, the antenna layer including at least one antenna element configured to transmit and receive electromagnetic waves, and the composite radome including an absorber layer extending over the top of the antenna layer and a cover layer extending over the top of the absorber layer. Background Technology

[0002] Radar sensors are crucial perception sensors in modern vehicles and across the automotive technology field. This is because, compared to other perception sensors such as cameras, the information provided by radar sensors is usable even in low-light conditions and adverse weather conditions.

[0003] For aerodynamic and aesthetic reasons, automotive radar sensors are typically integrated into or concealed behind other vehicle components, i.e., behind the vehicle's housing. Such vehicle components can be bumpers, dashboards, signs, etc. Furthermore, the internal components of automotive radar sensors are usually mounted within a sensor housing, with a cover on top of the housing. The housing and cover encapsulate and protect the internal sensor components from environmental factors such as dust, moisture, corrosion, rust, and mechanical damage.

[0004] However, if another vehicle component is placed in front of the radar sensor's antenna, the radar sensor's performance may degrade relative to its ideal performance. This is likely due to the fact that strong multiple bounce effects can occur between the vehicle component and the radar sensor, such as multiple reflections between different surfaces of the vehicle component, the radar sensor, and the radome. The impact of this multiple bounce effect on a given antenna radiation pattern depends on the corresponding air gaps between the radome and the radar sensor, and between the radome and the vehicle component, as well as the thickness and shape of the radome. Furthermore, an increase in the level of sidelobes (e.g., elevation sidelobes) and depolarization effects may occur.

[0005] Even if the radar sensor radome is properly designed and integrated into the vehicle, most of the aforementioned interference effects may still exist, for example, due to multiple bounce reflections between the radar sensor's metallic planar surface and vehicle components. Such metallic surfaces can be highly reflective of electromagnetic waves and can be present within the radar sensor at the top surface of the antenna plate and / or radome, and additionally at another vehicle component (e.g., the vehicle's bumper or dashboard).

[0006] Furthermore, when performing angle detection relative to external objects using radar sensors, the angle error may increase due to the aforementioned effects. For example, if a radar sensor, such as a vehicle front radar, must be integrated behind a painted dashboard and high accuracy is required to find the angle or determine the direction of arrival (DoA) of the radar wave, then the interaction between the radar wave and the dashboard should be strongly mitigated. The same applies if the radar sensor has an extended field of view with respect to elevation.

[0007] Therefore, a radar sensor is needed to reduce interference effects, such as the effects of multiple bounce reflections, when it is installed near another vehicle component. Summary of the Invention

[0008] This disclosure provides a radar sensor according to the independent claims and a method for manufacturing such a radar sensor. Embodiments are given in the dependent claims, the specification, and the drawings.

[0009] In one aspect, this disclosure relates to a radar sensor comprising an antenna layer and a composite radome. The antenna layer includes at least one antenna element configured to transmit and receive electromagnetic waves. The composite radome includes an absorber layer extending over the top of the antenna layer and a cover layer extending over the top of the absorber layer. The absorber layer has a higher absorption coefficient for electromagnetic waves than the cover layer. The composite radome includes a main region in which the absorber layer has a reference absorber thickness, and the cover layer has a reference cover thickness at at least one location within the main region. Furthermore, the composite radome includes at least one sub-region in which the absorber layer has a sub-absorber thickness, and the cover layer has a sub-cover thickness at at least one location within the sub-region. The sub-cover thickness differs from the reference cover thickness. For a first predetermined angle of incidence, the electromagnetic wave reflectivity is at a minimum in the main region, while for a second predetermined angle of incidence different from the first predetermined angle of incidence, the electromagnetic wave reflectivity is at a minimum in the sub-region.

[0010] Radar sensors may include various components, including, for example, layers or boards for electronic elements such as monolithic microwave integrated circuits (MMICs), layers or components formed as antenna bottom covers, and antenna layers formed as antenna top covers. One or more antenna elements are disposed within the antenna layer, and these antenna elements may be surrounded by absorber layers. That is, the absorber layer may extend on top of those sections of the antenna layer that do not contain antenna elements.

[0011] The antenna layer can define a reference plane, on which one or more antenna elements are mounted. The thicknesses of the absorber layer and the cladding layer can be defined in a direction perpendicular to this reference plane; that is, the reference absorber thickness and the reference cladding thickness, as well as the secondary absorber thickness and the secondary cladding thickness. The direction in which these thicknesses are defined can also be the same as the boresight direction of the radar sensor.

[0012] The electromagnetic waves transmitted and received by the antenna elements of a radar sensor can have frequencies in a range suitable for automotive radar, such as from 76 GHz to 81 GHz, or alternatively, frequencies exceeding 100 GHz, of which approximately 120 GHz of the frequency band can be associated with advanced automotive radar sensors.

[0013] A composite cover with an absorber layer and a cover layer means that the composite cover requires at least one absorber layer and at least one cover layer. However, the composite layer can also be a multi-layer system, which may further include, for example, additional coating layers or layers for improving the lighting characteristics of the composite cover. Furthermore, such a multi-layer system may include more than one absorber layer and more than one cover layer.

[0014] The main region and at least one sub-region can have macroscopic dimensions on top of a partition without antenna elements. However, the main region and at least one sub-region can be discontinuous, i.e., comprising different sub-regions spatially separated and configured with corresponding reference thicknesses and corresponding sub-thicknesses of the absorber layer and cladding layer, respectively, for at least one location within a corresponding sub-region. For example, a portion of the main region and one sub-region belonging to the sub-region can be disposed between a pair of antenna elements, wherein the corresponding sub-region of the sub-region having a sub-absorber thickness can be formed as a cavity or protrusion relative to a reference height level. This reference height level can be defined by the upper surface of the absorber layer at at least one location within the main region where the absorber layer has a reference absorber thickness. Since the absorber layer and cladding layer can be connected to each other without air gaps therebetween, the material of the cladding layer can fill the one or more cavities within the sub-region or surround the one or more protrusions providing the sub-absorber thickness.

[0015] The first and second predetermined incident angles can be defined relative to a direction perpendicular to the upper surface of the composite radome or to a direction perpendicular to the reference plane on or above the antenna element. For a given frequency of the electromagnetic wave, the predetermined incident angle at which the reflectivity of the electromagnetic wave is at its minimum depends on the corresponding thickness of the cladding layer in the corresponding region, namely the reference cladding thickness and the sub-cladding thickness.

[0016] To minimize the reflectivity of electromagnetic waves, the electrical lengths of the cladding layer and the absorber layer can be optimized along with the antenna surface. Possible options for minimizing reflectivity can be described by the following formula, achieving maximum attenuation or minimum reflection of electromagnetic waves within the corresponding region, i.e., for electromagnetic waves with corresponding first and second predetermined incident angles:

[0017] ,in

[0018] in, λ is the wavelength of the electromagnetic wave at frequency f, c0 is the speed of light in a vacuum, and DK is the dielectric constant of the material in the overlay layer. i represents an integer, but can also be zero.

[0019] The corresponding electrical length determines the required thickness of the overlay layer in the main region and at least the secondary region to achieve minimum reflectivity at the first and second predetermined incident angles, namely the reference overlay thickness and the secondary overlay thickness.

[0020] The required thicknesses of the cover layers in these regions can correspond to the aforementioned reference height level for the absorber layer in the main region and the secondary height level for the absorber layer in at least one secondary region, respectively, assuming the composite cover has a constant total thickness. In other words, if a constant thickness of the composite cover is required, the reference cover thickness and the secondary cover thickness can determine the reference absorber thickness and the secondary absorber thickness.

[0021] However, the thickness of the reference absorber and the secondary absorber can just exceed the required minimum thickness to, for example, provide sufficient absorption for electromagnetic waves to suppress multiple bounce effects. That is, the thickness of the reference absorber and the secondary absorber can even be equal. In this case, an air-filled cavity can be formed at the antenna surface, i.e., on top of the antenna layer. An air-filled cavity can also be caused by the antenna surface structure if the flat surface of the absorber layer faces the antenna layer. Alternatively, this surface of the absorber layer can follow the relief of the top surface of the antenna layer without an air-filled cavity. However, if a nearly constant thickness of the composite cover is required, the thickness of the reference absorber can be greater than the thickness of the secondary absorber if the thickness of the reference cover is less than the thickness of the secondary cover, and vice versa.

[0022] In summary, for at least two predetermined incident angles—namely, for a first predetermined incident angle and for at least one additional predetermined sub-incident angle—the reflectivity of the overlay layer and the absorber layer (i.e., the composite radome as a whole) is minimized. Therefore, interference with radar sensor performance is reduced.

[0023] Furthermore, the angle detection performance of radar sensors can be improved. That is, the angle error when determining the direction of arrival (DoA) can be significantly reduced. Additionally, the coverage range of radar sensors in both azimuth and elevation angles can be extended due to reduced multi-hop effects. Moreover, the propagation of surface waves can be reduced (e.g., between at least two antenna elements) due to the extension of the absorber layer within sections without antenna elements.

[0024] Since the main region and at least one sub-region can be disposed as macroscopic entities on the surface of the absorber layer, the workload for manufacturing the absorber layer and thus the entire radar sensor can be reduced compared to an absorber layer with small structures for reducing the aforementioned interference effects.

[0025] According to the implementation, the thickness of the secondary absorber can differ from the thickness of the reference absorber. For example, if the thickness of the secondary absorber is greater than the thickness of the reference absorber, then the thickness of the secondary absorber can be less than the thickness of the reference absorber, and vice versa. In this way, a nearly constant thickness of the composite cover can be achieved in both the primary and secondary regions. This provides a smooth appearance for the composite cover.

[0026] The first predetermined incident angle can represent the line-of-sight direction relative to the antenna layer. Regarding the multiple bounce effect, the most important angular range, i.e., close to the line-of-sight direction, can be covered by this choice of the first predetermined incident angle. However, compared to an absorber layer that only reduces reflectivity at the line-of-sight direction, a second predetermined incident angle, different from the line-of-sight direction and also having minimal reflectivity, can enhance the total reflectivity over a larger angular range.

[0027] The main region may extend between at least one antenna element and at least one sub-region. In other words, the main region may be located close to or adjacent to at least one antenna element, while at least one sub-region may have a greater distance to at least one antenna element than the main region. Thus, for example, multiple bounce reflections at the line of sight can be reduced by the main region adjacent to the antenna element, while at least one sub-region may be associated with a larger sub-incident angle at which a further minimum of reflectivity occurs.

[0028] The reference absorber thickness within the main region (i.e., the aforementioned reference height level) can correspond to the maximum height level of the entire absorber layer. Conversely, the sub-absorber thickness within the sub-region can be less than the maximum height level associated with the main region.

[0029] At least one sub-region may be located at least partially between the two antenna elements. Therefore, the sub-region can improve the isolation between the two antenna elements due to the minimum reflectivity at the second predetermined incident angle within the sub-region.

[0030] According to another embodiment, in the at least one sub-region, the absorber layer may include multiple cavities, in which the thickness of the sub-absorber may be less than the thickness of the reference absorber. Such cavities may require less work in manufacturing the absorber layer. Furthermore, the cavities may provide minimal reflectivity, for example, at a second predetermined incident angle different from, for example, the viewing axis.

[0031] Furthermore, the individual cavities can be formed as rectangular strips, and at least one strip can have a length greater than the length of at least one antenna element in one direction within the absorber layer. Such rectangular strips can further reduce the amount of manufacturing work required. Additionally, the isolation of at least one antenna element can be improved because one strip extends along at least the entire length of the antenna element in a predetermined direction.

[0032] Furthermore, the cavities can be aligned parallel to each other. This alignment can further reduce the workload of fabricating the absorber layer. In addition, parallel-aligned cavities can improve the isolation of antenna elements.

[0033] In the subregion, the absorber layer may include at least one section that is tilted relative to a reference plane extending parallel to the antenna layer. Tilted or oblique sections within the subregion can facilitate the fabrication of a subregion designed to minimize reflectivity for a second predetermined incident angle.

[0034] According to another embodiment, the surface of the absorber layer may have a continuous height gradient in the main region and / or at least one sub-region. For example, the main region and sub-region may be defined as different regions or partitions on the continuously rising or falling surfaces of the absorber layer. Furthermore, the corresponding surface (e.g., the inner surface) of the cover layer may also have a continuous height gradient, for example, having the same absolute value but different signs. In other words, if the absorber layer has, for example, a falling surface, the cover layer may have a rising surface. Such surfaces of the absorber layer and cover layer with corresponding continuous height gradients can provide electromagnetic waves with a tilt angle within a certain range where reflections of the composite shield can be minimized, for example, close to the line of sight.

[0035] A continuous altitude gradient can have a constant absolute value in at least a portion of the main and sub-regions, and this absolute value can depend on the radar sensor's field of view. The field of view can be the instrument's field of view with respect to the azimuth and elevation angles relative to the radar sensor. If a wide field of view is required, a larger absolute value of the altitude gradient can be applied.

[0036] Alternatively, the continuous height gradient can vary non-linearly in at least a portion of the main and secondary regions. This non-linearly varying height gradient allows coverage of an increasing angular range with respect to reflectivity minimization. Furthermore, the above embodiments can be combined such that, in the main and secondary regions, there are partitions of absorber and overlay layers with constant height gradients, while other partitions can have non-linear height gradients for the absorber and overlay layers, respectively.

[0037] As an alternative to a continuous gradient, the main region and at least one sub-region can be formed by a stepped surface of the absorber layer. The main region can constitute a first or highest step adjacent to at least one antenna element. Furthermore, the surface of the absorber layer can "step down" from the main region adjacent to the antenna element to one or more sub-regions, which have a larger distance to the antenna element than the main region. A stepped surface with macroscopic dimensions can also reduce the amount of work required in manufacturing.

[0038] Furthermore, the above embodiments can be combined in the following way: in the main region and the sub-region, there can be partitions with absorber layers provided with cavities as described above, while other partitions can be provided with constant or non-linear height gradients of absorber layers and cover layers respectively.

[0039] According to another embodiment, the radar sensor can have no air gap between the antenna layer and the absorber layer. This allows for a compact arrangement of the radar sensor, including attaching the composite radome directly to the upper surface of the antenna layer. However, for applications where the absorber layer is not required, the composite radome including the absorber layer can be easily replaced.

[0040] Generally, the absorber layer may contact the antenna layer so that there is no air gap between them; alternatively, the absorber layer may not contact the antenna layer so that an air gap exists between them. The surface of the antenna layer may be flat, which facilitates direct contact between the absorber layer and the antenna layer without air gaps. Alternatively, the surface of the antenna layer may be structured, and this is an example of an implementation in which the absorber layer and the antenna layer may enclose one or more air-filled cavities therebetween.

[0041] Furthermore, the absorber layer can be formed from a plastic material with a dielectric constant of up to 15. For example, the optimized dielectric constant can be approximately 8.

[0042] On the other hand, this disclosure relates to a vehicle comprising vehicle components and a radar sensor as described above, the radar sensor being disposed near the vehicle components. The vehicle components may be, for example, a dashboard, a bumper, or a sign.

[0043] In another aspect, this disclosure relates to a method for manufacturing a radar sensor. According to the method, an antenna layer for a radar sensor is provided, the antenna layer including at least one antenna element configured to transmit and receive electromagnetic waves. An absorber layer and a cover layer are connected to form a composite radome, wherein the absorption coefficient of the absorber layer for electromagnetic waves is higher than that of the cover layer. The composite radome is mounted on top of the antenna layer, wherein the composite radome includes a main region and at least one sub-region, wherein the absorber layer has a reference absorber thickness in the main region and the cover layer has a reference cover thickness at at least one location in the main region, and the absorber layer has a sub-cover thickness at at least one location in the sub-region. The sub-cover thickness is different from the reference cover thickness. For a first predetermined incident angle, the reflectivity of the electromagnetic waves is at a minimum in the main region, and for a second predetermined incident angle different from the first predetermined incident angle, the reflectivity of the electromagnetic waves is at a minimum in the sub-region.

[0044] In general, a method for manufacturing a radar sensor as described above is provided. Therefore, the advantages and description of the implementation of the radar sensor also apply to this method.

[0045] According to an embodiment of the method, the absorber layer and the cover layer can be manufactured by 3D printing or injection molding. Furthermore, the connection between the absorber layer and the cover layer used to provide the composite cover can be established using an adhesive. Attached Figure Description

[0046] This document describes exemplary embodiments and functions of the present disclosure in conjunction with the following accompanying drawings.

[0047] Figure 1A and Figure 1B A schematic side view of a radar sensor mounted in a vehicle is shown.

[0048] Figure 2 The diagram schematically shows a top view of the absorber layer positioned on top of the antenna layer of a radar sensor.

[0049] Figure 3A and Figure 3B The diagram schematically shows a side view of the composite radome on top of the antenna layer and a perspective view of the absorber layer.

[0050] Figure 4 A side view schematically illustrates another embodiment of the composite radome on top of the antenna layer, and

[0051] Figure 5 A side view schematically illustrating another embodiment of the composite radome on top of the antenna layer is shown, along with a graph depicting the reflectivity as a function of the incident angle.

[0052] List of reference numerals

[0053] 100 radar sensors

[0054] 110 vehicles

[0055] 120 vehicle parts, such as dashboards or bumpers

[0056] 130mm mirror with multiple reflections

[0057] 140 housing

[0058] 150 electronic board

[0059] 160 antenna layers

[0060] Structure on top of the 162 antenna layer

[0061] 164 air-filled cavity

[0062] 170 standard mask

[0063] 200 absorber layers

[0064] 210 is used for openings in the absorber layer of antenna elements.

[0065] 212 Absorber Layer Sloping Upper Surface

[0066] 214 absorber layer stepped upper surface

[0067] 220 Main Area

[0068] 230 First Region

[0069] 232 Second Region

[0070] 240 chambers

[0071] 310 reference absorber thickness

[0072] 320 reference plane

[0073] 330 reduced or sub-absorbent thickness

[0074] 332 Further reduction in the thickness of the sub-absorber

[0075] 350 covering layers

[0076] 360 reference coverage thickness

[0077] 370 increased or sub-coverage thickness

[0078] 372 Further increase in or sub-coverage thickness

[0079] 380 coating layers

[0080] 390 composite cover

[0081] 400 antenna elements

[0082] 410 Package Protection Zone

[0083] 415 Transmitted electromagnetic waves

[0084] 420 reflected electromagnetic waves at 10°

[0085] 422 reflects electromagnetic waves at 30°

[0086] 424 reflects electromagnetic waves at 45°

[0087] Reflectivity of 510 horizontally polarized electromagnetic waves

[0088] Reflectivity of 520 vertically polarized electromagnetic waves Detailed Implementation

[0089] Figure 1A A radar sensor 100 is schematically depicted, mounted in a vehicle 110 behind a vehicle component 120 (e.g., the bumper, dashboard, or sign of the vehicle 110). For aesthetic and aerodynamic reasons, automotive radar sensors similar to radar sensor 100 are typically located behind the housing of the vehicle 110.

[0090] exist Figure 1B The image depicts an enlarged side view of a radar sensor 100. The radar sensor 100 includes a housing 140, within which various boards or layers 150, 160 are mounted as internal components. These boards or layers include board 150 for electronic components such as monolithic microwave integrated circuits (MMICs) and one or more boards or layers 160 for antenna elements or antenna layers. These antenna layers 160 may include a bottom cover or bottom layer and a top cover or top layer. Alternatively, the antenna layer 160 may include a printed circuit board (PCB) on which antenna elements are disposed.

[0091] In addition, the radar sensor 100 has a conventional cover 170. The housing 140 and the cover 170 encapsulate and protect the internal components of the radar sensor 100, such as the plates or layers 150, 160, from environmental factors such as dust, moisture, corrosion, rust, and mechanical damage.

[0092] The surface of the vehicle component 120 can have a high reflectivity to radar waves transmitted by the sensor 100. Therefore, multiple bounce reflections occur, which are caused by… Figure 1A and Figure 1BThe arrow 130 in the diagram illustrates this. Multiple bounce reflections 130 can exist between the radar sensor 100 and the carrier component 120. Furthermore, multiple bounce reflections 130 can also exist between the flat surface of the radome 170 and the upper antenna layer or plate 160. The impact of this multiple bounce effect on a given antenna radiation pattern depends on the corresponding air gaps between the radome 170 and the radar sensor 100, and between the radome 170 and the carrier component 120, as well as the thickness and shape of the radome 170. Reflections 130 are accompanied by undesirable interference effects on the performance of the radar sensor 100, such as radome insertion and transmission loss, line-of-sight error, antenna main lobe ripple, beamwidth and field of view contraction of the radar sensor 100, increased sidelobe level, and depolarization effects.

[0093] Even if the shroud 170 is properly designed and installed to minimize such undesirable interference effects, most of these interference effects may still be retained, for example, due to reflection. Therefore, the radar sensor 100 according to this disclosure is configured to minimize such interference effects as much as possible.

[0094] Figure 2 A schematic top view of the absorber layer 200 of the radar sensor 100 according to this disclosure is depicted. The absorber layer 200 is located on the antenna layer 160 (see...). Figure 4 The antenna layer 160 is located on top of the antenna element 400 and includes an opening 210, which is disposed on the corresponding antenna element 400 (see [reference]). Figure 4 The absorber layer 200 covers the section of the antenna layer 160 that does not contain the antenna element 400. The absorber layer 200 can have a dielectric constant up to 15. A specific dielectric constant of the absorber layer 200 could be, for example, 8.

[0095] The antenna layer contains corresponding antenna elements 400 (see...). Figure 4 The partitions can be considered as so-called active partitions or regions. Each antenna element 400 is configured to transmit and receive electromagnetic waves. The frequency of the transmitted electromagnetic waves is within the typical bandwidth of 76 GHz to 81 GHz currently used in automotive radar sensors. However, frequencies exceeding 100 GHz can also be used, such as the band near 120 GHz associated with advanced automotive radar sensors.

[0096] The surface of absorber layer 200 includes a main region 220, in which absorber layer 200 has a reference absorber thickness 310 relative to a reference plane 320 at the “bottom” of absorber layer 200 (see [reference]). Figure 3A The reference plane 320 extends parallel to the antenna layer 160, for example, parallel to its upper surface. The reference absorber thickness 310 of the main region 220 is defined relative to the line-of-sight direction of the antenna element 400, i.e., relative to the direction perpendicular to the reference plane 320.

[0097] Furthermore, the absorber layer 200 includes a sub-region 230, which is different from the main region 220 and has a sub-absorber thickness 330 that is different from (i.e., less than) the reference absorber thickness 310 (see [reference]). Figure 3A For example, Figure 2 and Figure 3A and Figure 3B In the embodiment shown, the subregion 230 is formed by a plurality of cavities 240 that are recessed relative to the surface of the absorber layer 200 in the main region 220.

[0098] Figure 3B A perspective view of the absorber layer 200 is schematically depicted. The opening 210 of the antenna element 400 is indicated only by a recess. Between a corresponding pair of antenna elements 400 (i.e., openings 210), a portion of a main region 220 having a reference absorber thickness 310 is positioned adjacent to the corresponding antenna element 400. Two portions or segments of the main region 220 are disposed between the corresponding pair of antenna elements 400. Because segments of the absorber layer 200 are arranged between the antenna elements 400, the propagation of surface waves between the antenna elements 400 is reduced.

[0099] Between these portions or segments of the main region 220 adjacent to the corresponding antenna element 200, portions or segments of the sub-region 230 with reduced or sub-absorber thickness 330 are provided, i.e., corresponding cavities 240. For example... Figure 2 , Figure 3A and Figure 3B As shown, the subregion 230, having a reduced or minor thickness 330 relative to the reference plane 320, is formed by the antenna element 400 (see...). Figure 2 The opening 210 and the surrounding extended cavity 240 are formed. For example... Figure 3B As shown, the cavity 240 is aligned in parallel with the antenna element 400 within the absorber layer 200.

[0100] The cavity 240 is formed as rectangular strips, and at least some of these strips have a length greater than the corresponding length of the antenna element 400 in the same direction, i.e., the longer side of the corresponding rectangle. Furthermore, as can be... Figure 3A As recognized in the study, cavity 240 has a chamfered edge at the boundary between the main region 220 and the sub-region 230. Such a chamfered edge can facilitate the fabrication of absorber layer 200.

[0101] In such Figure 2 and Figure 3A and Figure 3BIn the embodiment of the absorber layer 200 shown, the bottom surface of the corresponding cavity 240 is a flat surface, i.e., extending in or parallel to the reference plane 320. Alternatively, such a bottom surface of the corresponding cavity can be a sloping or conical surface. This can help to adapt the cavity to a predetermined incident angle of the electromagnetic wave to minimize the reflectivity of the absorber layer 200, as described below.

[0102] In addition, the radar sensor 100 includes a cover layer 350 made of plastic material (see...). Figure 3A as well as Figure 4 and Figure 5 The cover layer 350 covers and protects the entire antenna layer 160, namely the absorber layer 200 including the opening 210 (in which the antenna element 400 is located).

[0103] In the main region 220, the cover layer 350 has a reference cover thickness 360 that extends along a visual axis direction perpendicular to the reference plane 320, i.e., in the same manner as the reference absorber thickness 310. In the sub-region 220, the cover layer 350 has an increased sub-cover thickness 370, which also extends along a visual axis direction perpendicular to the reference plane 320, i.e., in the same manner as the sub-absorber thickness 330.

[0104] One or more coating layers 380 are provided on top of the cover layer 350. The cover layer 350 is arranged on top of the absorber layer 200 such that there is no air gap between the absorber layer 200 and the cover layer 350. Therefore, the absorber layer 200 and the cover layer 350 including the coating layer 360 form a composite cover 390 of the radar sensor 100.

[0105] Therefore, the composite cover 390 includes a main region 220 and a sub-region 230. In the main region 220, the absorber layer has a reference absorber thickness 310 and the cover layer 350 has a reference cover thickness 360. In the sub-region 230, the absorber layer has a sub-absorber thickness 330 and the cover layer 350 has a sub-cover thickness 370. Figure 3A In the embodiment shown, the composite cover 390 has a constant total thickness. Therefore, the sum of the reference absorber thickness 310 and the reference cover thickness 360 is almost the same as the sum of the secondary absorber thickness 330 and the secondary cover thickness 370, and both of these sums correspond to the total thickness of the composite cover 390.

[0106] like Figure 3AAs shown on the left, antenna layer 160 may have a flat surface. In this case, direct contact is provided between absorber layer 200 and antenna layer 160 without any air gap. Alternatively, the surface of the antenna layer may be structured, as indicated by structure 162 on top of antenna layer 160. In this case, an air-filled cavity 164 is formed between absorber layer 200 and antenna layer 160. Generally, absorber layer 200 may contact antenna layer 160 such that no air gap exists between them, or alternatively, absorber layer 200 may not contact antenna layer 160 such that an air gap exists between them.

[0107] In both cases, the composite radome 390 is generally located on top of the antenna layer 160. Therefore, if needed, for example in cases where a conventional radome consisting only of a flat cover layer does not require an absorber layer, the composite radome 390, which includes the absorber layer 200, can be easily replaced.

[0108] In the partition or opening 210 where the radar element 400 is located, a small air gap can be provided between the corresponding antenna element 400 and the cladding layer 350. Alternatively, the cladding layer 350 can be directly disposed on top of the corresponding antenna element 400, so that there is no air gap between them. Figure 3A As is understood, the overlay layer extends slightly into the opening 210, that is, on top of the corresponding antenna element 400.

[0109] Because the thickness of the subcover 370 is different from (i.e. greater than) the thickness of the reference cover 360, the reflectivity of the electromagnetic wave is at its minimum at different incident angles, both in the main region 220 and in the subregion 230. Specifically, for a first predetermined incident angle, the reflectivity of the electromagnetic wave is at its minimum in the main region 220, while for a second predetermined incident angle different from the first predetermined incident angle, the reflectivity of the electromagnetic wave is at its minimum in the subregion 230. Now, further reference will be made to... Figure 4 and Figure 5 This will be explained in detail.

[0110] At the line of sight, i.e., at a 0° incident angle of the electromagnetic wave relative to the direction perpendicular to the reference plane 320, the optimized thickness d of the overlay layer 350 for achieving minimum reflectivity is given by the following formula:

[0111] ,in

[0112] in, λ is the wavelength of the radar wave or electromagnetic wave at frequency f, c0 is the speed of light in a vacuum, and DK is the dielectric constant of the material in the overlay layer 350. i represents an integer, but can also be zero.

[0113] At an incident angle greater than zero, the distance d corresponds to the electrical length 35° across the overlay layer for that specific angle. When considering... Figure 4 When the electromagnetic wave 415 is transmitted at different angles relative to the radar sensor 400, the different incident angles of the electromagnetic wave at the upper surface of the composite cover 390 correspond to different electrical lengths through the covering layer 350. Conversely, if the thickness of the covering layer 350 varies, the same electrical length corresponding to minimum reflection is achieved at different incident angles of the electromagnetic wave, as in... Figure 4 This can also be recognized in the text.

[0114] Figure 4 Another embodiment of the radar sensor 100 is depicted, which includes at least one antenna element 400 mounted on an antenna plate or layer 160, said antenna plate or layer 160 having high reflectivity to electromagnetic waves, for example, due to a metallic surface or due to a jump in dielectric constant. The radar sensor 100 also includes an absorber layer 200 located on top of the antenna plate 160 and a cover layer 350 located on top of the absorber layer 200. Thus, the absorber layer 200 and the cover layer 350 again constitute a composite cover 390 for the antenna substrate 160.

[0115] The absorber layer 200 has a sloping or tapered surface 212, such that the absorber layer 200 has a maximum or reference thickness 310 adjacent to the antenna element 400. In other words, the absorber layer 200 has a reference absorber thickness 310 at a location adjacent to the antenna element 400, i.e., at a certain location within the main region 220. However, in an alternative embodiment, the absorber layer may also have a minimum thickness adjacent to the antenna element 400.

[0116] In the two sub-regions 230 and 232, the thickness of the absorber layer 200 decreases with increasing distance relative to the antenna element 400. Within these sub-regions 230 and 232, a corresponding sub-absorber thickness 330 and 332 are reached at a certain location within the respective sub-regions 230 and 232 (corresponding to the sub-absorber thickness 330 within the cavity 240, see [link]). Figure 3A and Figure 3B Therefore, for example Figure 4 The absorber layer 200 of the embodiment of the radar sensor 100 shown provides a continuous or constant height gradient.

[0117] Accordingly, adjacent to antenna element 400, i.e., at a certain location within the main region 220, the cladding layer 350 has a reference absorber thickness 360. In the two sub-regions 230, 232, the thickness of the cladding layer 350 increases with increasing distance relative to antenna element 400. Within these sub-regions 230, 232, at a certain location within the respective sub-regions 230, 232, a corresponding sub-cladding thickness 370, 372 is reached (corresponding to the sub-cladding thickness 370 above cavity 240, see...). Figure 3A and Figure 3B ).

[0118] The primary region 220 is defined as being adjacent to the antenna element 400, and the secondary regions 230 and 232 have a greater distance to the antenna element 400 than the primary region 220. The dimensions of the primary regions 220, 230, and 232 can be arbitrarily chosen, as these regions only have imaginary boundaries. Independent of any specific size definition, the primary regions 220, 230, and 232 differ in height relative to the antenna layer 160 with respect to the absorber layer 200, such that the absorber thickness 310 of the absorber layer 200 in the primary region 220 is greater than the corresponding absorber thicknesses 330 and 332 in the secondary regions 230 and 232.

[0119] also, Figure 4 The image depicts a packaged protection zone 410 for antenna element 400. Within the packaged protection zone 410, minimal distortion is required for the transmitted and received radar waves. This minimal distortion is achieved through the construction of an absorber layer 200 having a sloping or conical surface 212, which provides minimal reflectivity for electromagnetic waves at different incident angles.

[0120] When installed in a vehicle, the radar sensor 100 is located on another vehicle component 120, such as a dashboard, painted bumper, cover, or sign (see also...). Figure 1A and Figure 1B Behind the antenna element 400. If the antenna element 400 transmits electromagnetic waves 415 at different angles, these electromagnetic waves are reflected at the carrier component 120, causing the incident angle of these radar waves 415 at the upper surface of the composite radome 390 to also vary. Due to the height gradient of the absorber layer 200 relative to the antenna plate 160 and the increased subcover thicknesses 370, 372, electromagnetic waves arriving at the upper surface of the composite radome 390 at different incident angles have minimum reflectivity at different incident angles.

[0121] For example, electromagnetic waves with small incident angles are reflected in the main region 220 adjacent to antenna element 200, and due to the corresponding reference cover thickness 360 of the cover layer 350 adjacent to antenna element 400, the reflectivity of radar waves is minimized for such small angles. The corresponding minimized reflection in the main region 220 is indicated by arrow 420, i.e., for an incident angle of approximately 10°.

[0122] Furthermore, the corresponding minimization of reflections at larger incident angles within subregions 230 and 232 is indicated by arrows 422 and 424, which correspond to incident angles of approximately 30° and approximately 45° at the upper surface of the composite cover 390, respectively. For these incident angles, electromagnetic wave reflections are minimized within the corresponding subregions 230 and 232 due to the increased subcover thicknesses 370 and 372 of the cover layer 350. As a result, distortion over the extended range of incident angles within the encapsulation protection zone 410 is minimized due to the height gradient of the surface 212 between the absorber layer 200 and the cover layer 350.

[0123] exist Figure 5 In the lower part, another embodiment of the radar sensor 100 is depicted, which is similar to... Figure 4 The difference in the embodiment shown is that a stepped surface 214 is used instead of a sloped surface 212 with a continuously decreasing height. Specifically, as Figure 5 The stepped surface 214 shown has three different height levels, corresponding to the reference absorber thickness 330 of the absorber layer 200 in the main region 220 and the corresponding sub-absorber thicknesses 330 and 332 of the absorber layer 200 in the corresponding sub-regions 230 and 232. Due to the stepped surface 214, the covering layer 350 is correspondingly provided with a reference covering thickness 360 in the main region 220, and correspondingly provided with sub-coverer thicknesses 370 and 372 in the corresponding sub-regions 230 and 232.

[0124] exist Figure 5 The upper part shows corresponding graphs of reflectivity or reflection amplitude in dB for the respective regions 220, 230, 232 of the composite shield 390 provided by the stepped surface 214 at the angle of incidence. In these graphs, the corresponding solid line 510 depicts the reflection amplitude for horizontally polarized electromagnetic waves, while the corresponding dashed line 520 represents the reflection amplitude for vertically polarized electromagnetic waves.

[0125] As can be seen in the figure, minimum reflectivity or reflection amplitude is achieved at different incident angles for the main region 220 and the corresponding sub-regions 230, 232. Specifically, for the main region 220 adjacent to the antenna element 200, minimum reflectivity is achieved approximately at the line of sight, i.e., at an incident angle of approximately 0°. For the first region 230 with an increased cover thickness 370, minimum reflectivity or reflection amplitude is achieved at an incident angle of approximately 22°, while for the second region 232 with a further increased sub-cover thickness 372, a corresponding minimum reflection amplitude is achieved at a larger incident angle of approximately 31°. Therefore, the stepped surface 214 provides minimum reflection amplitude at different incident angles.

[0126] According to this disclosure, a radar sensor may include: an antenna layer including at least one antenna element configured to transmit and receive electromagnetic waves; and a composite radome including: an absorber layer extending over the top of the antenna layer and a cover layer extending over the top of the absorber layer. The absorber layer may have a higher absorption coefficient for the electromagnetic waves than the cover layer. The composite radome may include: a main region in which the absorber layer has a reference absorber thickness, and the cover layer has a reference cover thickness at at least one location within the main region. Furthermore, the composite radome may include at least one sub-region in which the absorber layer has a sub-absorber thickness, and the cover layer has a sub-cover thickness at at least one location within the sub-region, the sub-cover thickness being different from the reference cover thickness. For a first predetermined angle of incidence, the reflectivity of the electromagnetic waves in the main region may be at a minimum, and for a second predetermined angle of incidence different from the first predetermined angle of incidence, the reflectivity of the electromagnetic waves in the sub-region may be at a minimum.

[0127] According to various embodiments, the thickness of the secondary absorber may differ from the thickness of the reference absorber.

[0128] According to various embodiments, the first predetermined incident angle may represent the line-of-sight direction relative to the antenna layer.

[0129] According to various embodiments, the main region may extend between the at least one antenna element and the at least one sub-region.

[0130] According to various embodiments, the thickness of the reference absorber in the main region can correspond to the maximum height level of the entire absorber layer.

[0131] According to various embodiments, the at least one sub-region may be located at least partially between the two antenna elements.

[0132] According to various embodiments, in the at least one sub-region, the absorber layer may include multiple cavities, in which the thickness of the sub-absorber may be less than the thickness of the reference absorber.

[0133] According to various embodiments, the surface of the absorber layer may have a continuous height gradient in the main region and / or in at least one sub-region.

[0134] According to various embodiments, the continuous height gradient may have a constant absolute value in at least a portion of the primary and secondary regions, and the absolute value may depend on the field of view of the radar sensor.

[0135] According to various embodiments, the continuous height gradient can vary non-linearly on the surface of the absorber layer in at least a portion of the primary and secondary regions.

[0136] According to various embodiments, the main region and the at least one sub-region may be formed by the stepped surface of the absorber layer.

[0137] According to various embodiments, the radar sensor may have no air gap between the antenna layer and the absorber layer.

[0138] According to various embodiments, at least one inflatable cavity may be surrounded between the antenna layer and the absorber layer.

[0139] According to this disclosure, a method for manufacturing a radar sensor may include the following steps: providing an antenna layer of the radar sensor, the antenna layer including at least one antenna element configured to transmit and receive electromagnetic waves; connecting an absorber layer and a cover layer to form a composite radome, wherein the absorption coefficient of the absorber layer for electromagnetic waves may be higher than the absorption coefficient of the cover layer for electromagnetic waves; and mounting the composite radome on top of the antenna layer. The composite radome may include: a main region in which the absorber layer has a reference absorber thickness, and the cover layer has a reference cover thickness at at least one location within the main region; and at least one sub-region in which the absorber layer has a sub-absorber thickness, and the cover layer has a sub-cover thickness at at least one location within the sub-region, the sub-cover thickness being different from the reference cover thickness. For a first predetermined angle of incidence, the reflectivity of electromagnetic waves may be at a minimum in the main region, and for a second predetermined angle of incidence different from the first predetermined angle of incidence, the reflectivity of electromagnetic waves may be at a minimum in the sub-region.

Claims

1. A radar sensor (100), the radar sensor (100) comprising: Antenna layer (160) includes at least one antenna element (400) configured to transmit and receive electromagnetic waves. as well as The composite cover (390) includes an absorber layer (200) extending on top of the antenna layer (160) and a cover layer (350) extending on top of the absorber layer (200). The absorption coefficient of the electromagnetic wave by the absorber layer (200) is higher than that by the cover layer (350). The composite cover (390) includes: A main region (220), in which the absorber layer (200) has a reference absorber thickness (310), and in which, for at least one location within the main region (220), the cover layer (350) has a reference cover thickness (360); and At least one sub-region (230, 232), in which the absorber layer (200) has a sub-absorber thickness (330, 332), and in which, for at least one location within the sub-region (230, 232), the cover layer (350) has a sub-cover thickness (370, 372), the sub-cover thickness (370, 372) being different from the reference cover thickness (360); and Specifically, for the first predetermined incident angle, the reflectivity of electromagnetic waves is at its minimum in the main region (220), and for the second predetermined incident angle, which is different from the first predetermined incident angle, the reflectivity of electromagnetic waves is at its minimum in the secondary regions (230, 232).

2. The radar sensor (100) according to claim 1, wherein, The thickness of the sub-absorber (330, 332) is different from the thickness of the reference absorber (310).

3. The radar sensor (100) according to claim 1 or 2, wherein, The first predetermined incident angle represents the line of sight relative to the antenna layer (160).

4. The radar sensor (100) according to claim 1, wherein, The main region (220) extends between the at least one antenna element (400) and the at least one sub-region (230, 232).

5. The radar sensor (100) according to claim 1, wherein, The reference absorber thickness (310) within the main region (220) corresponds to the maximum height level of the entire absorber layer (200).

6. The radar sensor (100) according to claim 1, wherein, The at least one sub-region (230, 232) is located at least partially between the two antenna elements (400).

7. The radar sensor (100) according to claim 1, wherein, In the at least one sub-region (230, 232), the absorber layer (200) includes a plurality of cavities (240), in which the thickness of the sub-absorber (330, 332) is less than the thickness of the reference absorber (310).

8. The radar sensor (100) according to claim 1, wherein, In the main region (220) and / or in at least one sub-region (230, 232), the surface (212) of the absorber layer (200) has a continuous height gradient.

9. The radar sensor (100) according to claim 8, wherein, The continuous height gradient has a constant absolute value in at least a portion of the main region (220) and the sub-regions (230, 232), and The absolute value depends on the field of view of the radar sensor (100).

10. The radar sensor (100) according to claim 8 or 9, wherein, The continuous height gradient varies non-linearly on the surface (212) of the absorber layer (200) in at least a portion of the main region (220) and the sub-regions (230, 232).

11. The radar sensor (100) according to claim 1, wherein, The main region (220) and the at least one sub-region (230, 232) are formed by the stepped surface (214) of the absorber layer (160).

12. The radar sensor (100) according to claim 1, wherein, There is no air gap between the antenna layer (160) and the absorber layer (200) of the radar sensor (100).

13. The radar sensor (100) according to claim 1, wherein, At least one inflatable cavity (164) is surrounded between the antenna layer (160) and the absorber layer (200).

14. A method for manufacturing a radar sensor (100), the method comprising the steps of: An antenna layer (160) is provided for the radar sensor (100), the antenna layer (160) including at least one antenna element (400) configured to transmit and receive electromagnetic waves. The absorber layer (200) and the cover layer (350) are connected to form a composite cover (390). Wherein, the absorption coefficient of the absorber layer (200) for the electromagnetic wave is higher than that of the cover layer (350) for the electromagnetic wave, and The composite cover (390) is mounted on top of the antenna layer (160). The composite cover (390) includes: A main region (220), in which the absorber layer (200) has a reference absorber thickness (310), and in which, for at least one location within the main region (220), the cover layer (350) has a reference cover thickness (360); and At least one sub-region (230, 232), in which the absorber layer (200) has a sub-absorber thickness (330), and in which, for at least one location within the sub-region (230, 232), the cover layer (350) has a sub-cover thickness (370, 372), the sub-cover thickness (370, 372) being different from the reference cover thickness (360); and Specifically, for the first predetermined incident angle, the reflectivity of electromagnetic waves is at its minimum in the main region (220), and for the second predetermined incident angle, which is different from the first predetermined incident angle, the reflectivity of electromagnetic waves is at its minimum in the secondary regions (230, 232).

15. The method according to claim 14, wherein, The absorber layer (200) and the cover layer (350) are manufactured by 3D printing or injection molding.

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