EP4641831A1

EP4641831A1 - Radar radome with rib structure

Info

Publication number: EP4641831A1
Application number: EP24171907.9A
Authority: EP
Inventors: Manar Bakro
Original assignee: Aptiv Technologies AG
Current assignee: Aptiv Technologies AG
Priority date: 2024-04-23
Filing date: 2024-04-23
Publication date: 2025-10-29

Abstract

The present disclosure relates to a radar system, particularly for automotive application, as well as a vehicle comprising such a radar system. The radar system comprises an antenna structure and a radome (10) covering at least partially the antenna structure. The radome has a first surface facing the antenna structure.

Description

Technical field

The present disclosure generally relates to a radar system and a vehicle comprising a radar system.

Background of the invention

In automotive application, sensors are commonly used to improve safety and/or to assist a driver. For example, Advanced Driver Assistance Systems (ADAS) and Automated Driving Systems (ADS), both known by the skilled person, may rely on sensor data to control the steering of a vehicle.
For these and other purposes, radars are being utilized. A radar antenna radiates an electromagnetic wave, e.g. of a millimeter band, in a desired direction and receives a reflected wave from objects in front of the radar to detect possible objects.
A radar may be mounted to a vehicle behind the facia, bumper or chassis of a vehicle facing in a specific direction (e.g. forward or reverse driving direction, sideways, inclined to the driving direction, etc.). A radar system may comprise a planar-shaped antenna array, covered by a radome forming a protective structure of the antenna array. A radome may be a structural, weatherproof enclosure that protects a radar antenna. In automotive applications, a radome may be an integral part of the automotive facia/bumper/chassis. Since the radar waves need to propagate through the radome or possibly other parts of the vehicle (fascia/bumper/chassis), reflections may occur which may negatively affect the accuracy of the radar system and may be perceived as noise. It is generally desirable to achieve minimum reflections, and that the radiation is not impaired e.g. by the radome.
To meet the requirements of ADAS/ADS specifications, specific radar radiation patterns must be provided for by the vehicle's radar system (for example meeting a certain resolution). For this purpose, the number of antennas mounted on an antenna board or printed circuit board (PCB) used in an antenna system may be increased. This, however, may lead to an increased radar cross section of the radar system, leading to an increased angular error.
A flat radome covering a planar antenna structure having several antennas may result in an undesired near field distribution between the radome and the antenna surface. Electromagnetic waves emitted by a first antenna may undergo multiple reflections between the fascia and the antenna surface and eventually negatively affect a second antenna of the antenna structure. This may increase the angle error of the antenna system both on the azimuth and elevation.
There is thus a need for an improved radar system.

Summary of the invention

The present disclosure provides a solution according to the subject matter of the independent claims.
A first aspect of the present disclosure relates to a radar system, particularly for automotive application. The radar system may be employed in a vehicle to facilitate navigation and monitoring of the surroundings of the vehicle. The radar system may be employed within an ADAS or ADS.
The radar system may comprise one or more antennas or radar antennas configured for emitting/radiating electromagnetic waves, preferably in a desired direction. For example, the one or more antennas may work in the 30 MHz to 300 GHz range, as will be appreciated by the person skilled in the art. Preferably, the one or more antennas may operate in a frequency band applicable for radar applications. In a preferred embodiment, the one or more antennas operate in the 76-81 GHz range.
The radar system comprises an antenna structure. This antenna structure may support or contain the one or more antennas of the radar system. For example, the antenna structure may be provided on a surface of an antenna board (e.g. a PCB). In certain embodiments, the antenna structure may comprise the antenna board, which may be a 3D printed or molded antenna PCB. The antenna structure may be a planar antenna structure, i.e. having a two-dimensional surface. The two-dimensional surface may be flat or bent. In typical applications, a surface normal of a (planar) antenna structure is facing towards the desired direction to be covered by the radar system. Preferably, the antenna structure comprises one or more antenna configured for operating at a frequency in the 76-81 GHz range, preferably at a frequency of about 78 GHz.
The radar system further comprises a radome covering at least partially the antenna structure. The radome may be a structural element which may protect the antenna or antenna structure from environmental influences. The radome may be formed by a part of a vehicle, e.g. a mirror housing, an emblem, a panel, a door, a bumper, etc., which may be part of an automotive facia. The radome may also be provided as a separate element. In automotive applications, for example, the radome itself may be covered by a part of an automotive facia.
The radome may preferably be made of a material that only minimally attenuates the electromagnetic radiation. For example, the radome may be manufactured from a dielectric material, e.g. from plastic. In preferred embodiments, the radome may comprise or consist of one or more of polybutylene terephthalate, fiberglass, and acrylic glass.
The radome has a first surface which faces the antenna structure. For example, the radome may be a flat element with a first surface facing the antenna structure and a second surface which is opposite of the first surface and faces away from the antenna structure.
The radome comprises a plurality of parallel ribs which are arranged on the first surface of the radome. The ribs may have a generally elongated form extending along the first surface of the radome. The ribs may be integrally formed with the remainder of the radome, or may be arranged separately on a radome base. The ribs may have a square, wavy or other cross-sectional shape. All ribs of the plurality of parallel ribs may have the same structure. Alternatively, one rib of the plurality of ribs may be differently shaped than another rib of the plurality of ribs. The area between the ribs provides for airgaps. The ribs are facing the antenna structure and are occupying the area between the radome and antenna structure. The plurality of parallel ribs may comprise two, three or more ribs. The ribs may be periodically spaced.
The inventors have found that the provision of the ribs and airgaps reduces the (multiple) reflections between the antenna structure and the radome of radar signals emitted from an antenna. The horizontal near field distribution between the radome and the antenna structure is reduced, thereby decreasing the angle error. Particularly if several antennas are arranged in the antenna structure, the provision of the ribs isolates nearby antennas from each other such that the near field distribution originating from a first antenna between the antenna structure and the radome is reduced by the ribs such that its impact on a second antenna of the antenna structure is reduced.
In addition, the ribs may provide structural integrity to the radome, helping it maintain its shape and withstand external forces such as wind, rain, and impacts. Further, the thermal conductivity between the antenna structure and the outer side of the radome is increased.
Preferably, the ribs are in contact with the antenna structure. The ribs may directly contact the antenna structure. In this manner, the ribs may sufficiently isolate different antennas from each other such that the influence of a horizontal near field distribution (or surface waves) generated at a first antenna is reduced at a second antenna of the antenna structure.
Preferably, adjacent ribs of the plurality of parallel ribs are spaced apart by the same distance. The distance between the ribs may be measured from the geometric center of one rib to the geometric center of an adjacent rib. With such a periodic arrangement of the ribs, the near field distribution originating from an antenna of the antenna structure is efficiently reduced.
Further preferred, a gap between two adjacent ribs is in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2 mm. The gap may be measured parallel to the antenna structure, at half height of the ribs. With such airgaps, the near field distribution originating from an antenna of the antenna structure is efficiently reduced. This particularly applies when the antennas of the antenna structure are operating at a frequency of about 78 GHz.
Preferably, each rib of the plurality of parallel ribs has a thickness in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2.5 mm, preferably of about 2 mm. The thickness may be measured parallel to the antenna structure, at half height of the ribs. Such a rib design allows for efficiently reducing the near field distribution originating from an antenna of the antenna structure.
Preferably, each rib of the plurality of parallel ribs has a height in the range of 1 mm to 10 mm, preferably in the range of 2 mm to 8 mm, further preferred in the range of 3 mm to 6 mm. The height may be measured in a direction perpendicular to the antenna structure (or from a tip of a rib to its base which is flush with the first surface of the radome in the middle between two adjacent ribs). Such a rib design allows for efficiently reducing the near field distribution originating from an antenna of the antenna structure.
Preferably, the ribs are protruding from a baseline surface of the radome, and a cross-sectional shape of the ribs is essentially rectangular. It will be appreciated that, due to manufacturing the cross-sectional shape of the ribs may deviate from a perfect rectangular shape at the crossover to the baseline surface of the radome and/or at the tip sections of the ribs. In any case, such an essentially rectangular form of the ribs provides for large reduction of the near field distribution originating from an antenna of the antenna structure.
Preferably, the ribs comprise a dielectric material, preferably polybutylene terephthalate. This provides for improved reduction of the near field distribution originating from an antenna of the antenna structure.
Preferably, the tip of each rib of the plurality of parallel ribs comprises an absorber material such as a radiation-absorbent material. For example, the absorber material may be JCS-9 from Laird. The absorber material may be selected such that is can be used together with the other radome material through the molding process when forming the radome. The absorber material may absorb traveling waves at the antenna surface. The radiation-absorbent material may be different from the (dielectric) material of the remaining rib structure, as it provides for improved absorption of electromagnetic waves. It has been found that providing such an absorber material on the tips of the ribs further reduces the near field distribution originating from an antenna of the antenna structure.
Further preferred, the tip comprising the absorber material has a height in the range of 0.1 to 2 mm, preferably in the range of 0.3 mm to 1 mm, preferably in the range of 0.5 mm to 0.8 mm. The height may be measured in a direction perpendicular to the antenna structure (or from a tip of a rib to its base which is flush with the first surface of the radome in the middle between two adjacent ribs). Such a configuration has shown to be effective in reducing the near field distribution originating from an antenna of the antenna structure.
Preferably, each rib of the plurality of rib comprises spaced rib segments. In other words, along their elongated extension along the first surface of the radome, each rib may comprise recesses which eventually define individual rib segments of one rib. Preferably, the rib segments are equally spaced from each other. The rib segments may have the same proportions, or different proportions, depending on the setup of the respective implementation. The ribs may be elongated or square having the same length and thickness. Also the ribs may have the same structure, i.e. the ribs may feature the same rib segments, and the same spacing between the rib segments. In particular embodiments, the rib segments may have the shape of needles (i.e. having a round base area), or may be square with a base area of e.g. 1×1 mm², 2×2 mm², 3×3 mm². Such a structure allows for a particularly advanced reduction of the near field distribution when an advanced antenna layout is used. Waves reflected form the fascia, for example, may create a surface field with reflected waves at the antenna structure, which can be efficiently prevented with the proposed structure. Further, the thermal conductivity between the antenna structure and the radome is optimized.
Further preferred, the spacing between the rib segments is in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2 mm. The spacing may be measured parallel to the elongated extension of the ribs along the first surface of the radome, at half height of the ribs. Such a structure allows for a particularly advanced reduction of the near field distribution when an advanced antenna layout is used.
Further preferred, each rib segment has a length of 0.5 mm to 20 mm, preferably in the range of 1 mm to 10 mm, preferably in the range of 1.5 to 8 mm, preferably in the range of 2 to 6 mm, preferably in the range of 2.5 to 4 mm. Rib segments of such dimension have proven particularly useful for reducing the near field distribution originating from an antenna of the antenna structure.
Preferably, at least one antenna of the antenna structure is not covered by a rib of the radome, preferably wherein each antenna of the antenna structure is not covered by a rib of the radome. As detailed, the antenna structure may support or contain one or more antennas of the radar system. The antenna structure may provide for a spacing in the boresight of the antenna, such that the functionality of the is not or only marginally affected by the antenna structure. In the boresight of the antenna(s), no rib may be placed, again to not impair the functionality of the antenna(s). However, the near field distribution originating from an antenna and evolving between the antenna structure is hindered from impairing the functionality from neighboring antennas due to the placement of the ribs.
Another aspect of the present disclosure relates to a vehicle, such as e.g. a passenger car, comprising a radar system as described herein.
The person skilled in the art recognizes that the present disclosure is not limited to a radar system and a vehicle. The present disclosure also relates to a radome configured to cover an antenna structure, which has a first surface and comprises a plurality of parallel ribs arranged on the first surface of the radome. The radome may be configured and designed as described herein.

Description of preferred embodiments

In the following, the preferred embodiments will be described with reference to the accompanying figures. In the figures, similar elements are described with the same reference sign.

Fig. 1: illustrates a vertical cross-section of a radar system according to an embodiment of the present disclosure;
Fig. 2: illustrates a vertical cross-section of a radar system according to another embodiment of the present disclosure;
Fig. 3: illustrates a horizontal cross-section of the radar system according to the embodiment of Fig. 2;
Fig. 4: illustrates a horizontal cross-section of a radar system according to another embodiment of the present disclosure;
Fig. 5: illustrates a vehicle according to another embodiment of the present disclosure;
Fig. 6: illustrates a radar system according to the prior art;
Fig. 7: illustrates a radar system according to another embodiment of the present disclosure;
Fig. 8: illustrates results of RCS simulations of the radar systems of Fig. 6 and Fig. 7.

Fig. 1 illustrates a vertical cross-section of a radar system 1 according to an embodiment of the present disclosure. The radar system 1 is a radar system configured for automotive applications. It may be employed within an ADAS or ADS, and provide input data for a control unit of the ADAS or ADS, as will be appreciated by the skilled person. The radar system 1 works in the 76-81 GHz range, preferably at 78 GHz.
The radar system 1 comprises a planar antenna structure 20. The planar antenna structure 20 supports or contains one or more antennas (not shown) of the radar system 1. The emitting direction of the antenna structure 20 is pointed upwards in the illustration of Fig. 1.
The radar system 1 further comprises a radome 10. The radome 10 has a first surface 11 facing the planar antenna structure 20. The emitted radar waves will need to pass through the radome 10. The radome protects the antenna structure 20 from environmental elements. By at least partially enclosing the antenna structure 20 in the radome 10, the sensitive components of the antenna structure 20 are shielded from damage, which can prolong the lifespan of the radar system 1 and reduce maintenance requirements.
The radome is made from a material that is transparent to radio waves, such as fiberglass or certain types of plastics. This allows radar signals to pass through the radome 10 with minimal attenuation or distortion at wide FOV and/or wide azimuth/elevation, ensuring that the performance of the radar system 1 is not significantly degraded by the presence of the radome 10.
In the embodiment of Fig. 1, the radome 10 comprises two parallel ribs 12 arranged on the first surface 11 of the radome 10. In the illustration of Fig. 1, the ribs extend in a direction in/out of plane. The ribs 12 are in contact with the antenna structure 20. In particular, the tips 13 of the ribs 12 which are remote from the first surface 11 of the radome 10 are contacting an antenna surface 21 of the antenna structure 20.
In the illustrated embodiment, the ribs 12 have a rectangular cross-section. At the edges of the rectangular cross-section, the shape of the ribs 12 may deviate from a perfect rectangular shape due to imprecisions during manufacturing. It will be appreciated that the ribs may have a different shape, e.g. wavy, triangular, sinusoidal, or a combination thereof.
The ribs 12 have a thickness or width w of 2 mm, and a height h of 5 mm The height of the ribs is the same as the height of the airgap between the antenna structure 20 and the radome base. Between the ribs 12 is a gap/airgap or spacing s of 3 mm. The ribs 12 are generally made integral with the remainder of the radome. The tips 13 of the ribs 12 comprise a radiation-absorbent material, e.g. JCS-9 from Laird. The radome including the ribs and tibs thereof is produced in a single molding process. The height t of the tips is 0,6 mm, for cost efficiency reasons. The dimensions of the ribs 12 are chosen to provide for improved characteristics of the radar system 1.
Fig. 2 illustrates a vertical cross-section of a radar system 1 according to another embodiment of the present disclosure. The structure of the radar system 1 is similar to that of Fig. 1, with a radome 10 and an antenna structure 20. In the embodiment of Fig. 2, the radome comprises four equally spaced ribs 12.
In the illustration of Fig. 2, the antenna structure 20 comprises three antennas 22a, 22b, 22c oriented such that emitted radar signals are passing trough channels towards the radome 10. The antennas 22a, 22b, 22c of the antenna structure 20 are not covered by ribs 12 of the radome 10. Thus, the boresight of the antennas 22a, 22b, 22c is free of ribs 12.
The operation of antenna 22b, for example, creates a near field distribution in the space between the antenna structure 20 and the radome 10. This may result from the excited waves from the antenna 22b itself, as well as from the excited wave resulting from waves reflected from the radome or fascia. Due to the presence of the ribs 12, the influence of the near field distribution on the operation of the neighboring antennas 22a, 22c is advantageously reduced. Thereby, the overall functionality and precision of the radar system 1 is increased.
Fig. 3 illustrates a horizontal cross-section of the radar system 1 according to the embodiment of Fig. 2, wherein the cross-sectional plane intersects the ribs 12 on the first surface of the radome 10. The antenna structure 20 is not visible in this illustration. As can be seen, the ribs 12 are having the same structure and are equally spaced parallel to each other. The ribs 12 have a length 1 larger than the rib's width and also larger than the spacing s between the ribs. The ribs 12 may extend along the entire dimension of the radome. In the illustrated embodiment, the rib's length l is less (about 10-20% less) than the extension of the radome's first surface.
Fig. 4 illustrates a horizontal cross-section of a radar system 1 according to another embodiment of the present disclosure, wherein the cross-sectional plane intersects the ribs 12 on the first surface of the radome 10. The antenna structure 20 is not visible in this illustration. Contrary to the embodiment of Fig. 3, the ribs are not made in one piece, but are made of spaced rib segments 14. In the illustrated embodiment, the segments 14 are of the same size with a length l_s of 4 mm (or anywhere between 1 to 4 mm), and the spacing between segments 14 of a rib r is 2 mm (or anywhere between 1 to 3 mm). In other embodiments, some or all of the ribs may be differently segmented into individual segments. In other embodiments, the shape of the segments 14 is square or round.
Fig. 5 illustrates a vehicle 2 according to another embodiment of the present disclosure. The vehicle 2 comprises a radar system 1 as described herein, for example the radar system 1 according to the embodiment of Fig. 2. The radar system 1 is arranged behind a fascia 30 of the vehicle. The radar system 1 is arranged such that radar waves emitted from the antenna structure 20 pass through the radome 10 and the fascia 30 of the vehicle.
Fig. 6 illustrates a radar system 1' according to the prior art. The prior art radar system 1' comprises a radome 10' covering an antenna structure 20'. The surface of the radome 10' facing the antenna structure 20' is flat. Electromagnetic waves emitted by an antenna associated with the antenna structure 20' may undergo multiple reflections between the antenna structure 20' and the radome 10', and may thereby eventually increase the angle error of the radar system 1'.
Fig. 7 illustrates a radar system 1 according to another embodiment of the present disclosure. The setup of the radar system 1 of Fig. 6 is similar to that of Fig. 6 in that it comprises a radome 10 covering an antenna structure 20. However, according to the present disclosure, the radome 10 comprises ribs 12 (seven parallel ribs are illustrated in Fig. 7). The ribs 12 protrude from a baseline surface of the radome 10 and extend towards the antenna structure 20. In comparison with the prior art radar system 1' of Fig. 6, the ribs 12 partially occupy the space between the radome 10' and the antenna structure 20'.
The tips 13 of the ribs 12 comprise a radiation-absorbent material and are in direct contact with the antenna structure 20. Alternatively, the tips 13 are mounted separately onto the ribs 12 of the radome 10. Accordingly, the ribs and radome support body have been produced in a single molding process, and the tips 13 have been mounted onto the ribs 12 in a separate step.
Fig. 8 illustrates results of RCS simulations of the radar systems of Fig. 6 and Fig. 7. The dotted line represents the simulation results obtained with the prior art radar system 1' of Fig. 6, while the solid line represents the simulation results obtained with the prior art radar system 1 of Fig. 7. The simulation is based on a plan wave (78 GHz) as source radiating vertical at the surface of the antenna. The reflected power at -100 to 100° azimuth is illustrated in Fig. 8. As can clearly be seen, in comparison to compared to the prior art radar system 1', the radar system 1 of Fig. 7 allows for reducing the reflections up to 12 dB.

List of reference signs:

1, 1': radar system
2: vehicle
10, 10': radome
11: first surface of radome
12: rib(s)
13: tip of the rib(s)
14: rib segments
20, 20': antenna structure
21: antenna surface
22a, 22b, 22c: antennas
30: fascia

Claims

Radar system (1), particularly for automotive application, the radar system (1) comprising:
an antenna structure (20), preferably a planar antenna structure; and

a radome (10) covering at least partially the antenna structure (20);

wherein the radome (10) has a first surface (11) facing the antenna structure (20) and wherein the radome (10) comprises a plurality of parallel ribs (12) arranged on the first surface (11) of the radome (10).
The radar system (1) of claim 1, wherein the ribs (12) are in contact with the antenna structure (20).
The radar system (1) of claim 1 or 2, wherein adjacent ribs (12) of the plurality of parallel ribs (12) are spaced apart by the same distance.
The radar system (1) of claim 3, wherein a gap (s) between two adjacent ribs (12) is in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2 mm.
The radar system (1) of any one of the preceding claims, wherein each rib (12) of the plurality of parallel ribs (12) has a thickness (w) in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2.5 mm, preferably of about 2 mm.
The radar system (1) of any one of the preceding claims, wherein each rib (12) of the plurality of parallel ribs (12) has a height (h) in the range of 1 mm to 10 mm, preferably in the range of 2 mm to 8 mm, further preferred in the range of 3 mm to 6 mm.
The radar system (1) of any one of the preceding claims, wherein the ribs (12) are protruding from a baseline surface of the radome (10), and wherein a cross-sectional shape of the ribs (12) is essentially rectangular.
The radar system (1) of any one of the preceding claims, wherein the ribs (12) comprise a dielectric material, preferably polybutylene terephthalate.
The radar system (1) of any one of the preceding claims, wherein the tip of each rib (12) of the plurality of parallel ribs (12) comprises an absorber material.
The radar system (1) of claim 9, wherein the tip comprising the absorber material has a height (t) in the range of 0.1 to 2 mm, preferably in the range of 0.3 mm to 1 mm, preferably in the range of 0.5 mm to 0.8 mm.
The radar system (1) of any one of the preceding claims, wherein each rib (12) of the plurality of ribs (12) comprises spaced rib segments (14).
The radar system (1) of claim 11, wherein the spacing (r) between the spaced rib segments (14) is in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2 mm.
The radar system (1) of claim 11 or 12, wherein each rib segment (14) has a length (l_r) of 0.5 mm to 20 mm, preferably in the range of 1 mm to 10 mm, preferably in the range of 1.5 to 8 mm, preferably in the range of 2 to 6 mm, preferably in the range of 2.5 to 4 mm.
The radar system (1) of any one of the preceding claims, wherein at least one antenna (21a, 21b, 21c) of the antenna structure (20) is not covered by a rib (12) of the radome (10), preferably wherein each antenna (21a, 21b, 21c) of the antenna structure (20) is not covered by a rib (12) of the radome (10).
A vehicle (2) comprising a radar system (1) according to any one of the preceding claims.