FR3111711A1 - Vehicle assembly including radar sensor - Google Patents

Abstract

The invention relates to a vehicle assembly (1) of a vehicle (2), said vehicle assembly (1) comprising a radar sensor (10) and an independent part (11) of said radar sensor (10), said radar sensor (10) comprising at least one transmitting antenna (100) configured to transmit primary radar waves (R1) and at least two receiving antennas (101) configured to receive secondary radar waves (R2),characterized in that said independent part ( 11) comprises:- a primary part (110) arranged facing said at least one transmitting antenna (100) which follows the form of propagation of said primary radar waves (R1) in the near field (NF), and which has a primary thickness (e1) constant, and- a secondary part (111) arranged facing said at least two receiving antennas (101) and which is planar. Figure for the abstract: figure 1

Description

Vehicle assembly comprising a radar sensor

The present invention relates to a vehicle assembly, said vehicle assembly comprising a radar sensor. It finds a particular but non-limiting application in motor vehicles.

A vehicle assembly comprising a radar sensor comprises, in a manner known to those skilled in the art, a transmitting antenna configured to transmit primary radar waves and at least two receiving antennas configured to receive secondary radar waves. The radar sensor is positioned at the front or at the rear of the vehicle to meet the needs of detecting an object in the environment outside the vehicle. Secondary radar waves are radar waves which are reflected on an object which is in the environment outside the vehicle and which thus make it possible to detect the presence of said object. The vehicle assembly further comprises an independent part behind which the radar sensor is positioned. The independent part is an exit window for a headlight of the vehicle. The radar sensor is printed on a flexible substrate which follows the shape of said output lens. It's stuck on it.

A disadvantage of this state of the art is that the primary radar waves are reflected on the independent part and return to the radar sensor. These are spurious reflections which reduce the signal-to-noise ratio and thus lead to a loss in the detection range of the radar sensor. Consequently, this leads to a detection error or no detection of an object while the latter is present in the environment outside the vehicle.

In this context, the present invention aims to provide a vehicle assembly comprising a radar sensor which makes it possible to solve the mentioned drawback.

To this end, the invention proposes a vehicle assembly, said vehicle assembly comprising a radar sensor and an independent part of said radar sensor, said radar sensor comprising at least one transmitting antenna configured to transmit primary radar waves and at least two antennas receivers configured to receive secondary radar waves, characterized in that said independent part comprises:
- a primary part arranged facing said at least one transmitting antenna which follows the form of propagation of said primary radar waves in the near field, and which has a constant primary thickness, and
- A secondary part arranged opposite said at least two receiving antennas and which is flat.

Thus, as will be seen in detail below, the form of propagation of the primary radar waves being quasi-spherical in the near field, the fact of following this form and having a constant thickness for the primary part of the independent part makes it possible to cancel the parasitic reflections between them. Consequently, this no longer disturbs the detection of an object in the environment outside the vehicle.

According to non-limiting embodiments, said vehicle assembly may also comprise one or more additional characteristics taken alone or according to all the technically possible combinations, among the following.

According to a non-limiting embodiment, said primary part is curved so that said primary radar waves have an angle of incidence which is normal to said primary part.

According to a non-limiting embodiment, said primary part has a constant radius of curvature.

According to a non-limiting embodiment, said secondary part has a constant secondary thickness.

According to a non-limiting embodiment, said secondary thickness is equal to said primary thickness.

According to a non-limiting embodiment, said primary part comprises a radius of curvature and said primary part is at a distance from said independent part, said radius of curvature comprising a size less than or equal to said distance.

According to a non-limiting embodiment, said independent part is made of plastic.

According to a non-limiting embodiment, said independent part is an exit window of a lighting device of the vehicle, a logo, a decorative part, or a radome.

There is also proposed an independent part of a vehicle assembly comprising a radar sensor, characterized in that said independent part comprises:
- a primary part arranged opposite at least one transmitting antenna of said radar sensor, which follows the shape of said primary radar waves, and which has a constant primary thickness,
- A secondary part arranged opposite at least two receiving antennas of said radar sensor and which is flat.

According to a non-limiting embodiment, said independent part is an exit glass of a lighting device of the vehicle, a logo, a decorative part or a radome.

According to a non-limiting embodiment, said light device is a headlight or a rear light of said vehicle.

According to a non-limiting embodiment, said primary part is arranged centered with respect to said at least one transmitting antenna.

The invention and its various applications will be better understood on reading the following description and on examining the accompanying figures:

is a schematic view of a vehicle assembly, said vehicle assembly comprising a radar sensor and an independent part of said radar sensor, said radar sensor comprising at least one transmitting antenna and at least two receiving antennas, according to a non-limiting embodiment of the invention,

is a schematic view of the form of propagation of primary radar waves emitted by said radar sensor of said vehicle assembly of the , in the near field and in the far field, according to a non-limiting embodiment,

is a schematic view of the form of propagation of primary radar waves emitted by said radar sensor of said vehicle assembly of the , in the near field, and of the form of propagation of secondary radar waves which arrive at said radar sensor, according to a non-limiting embodiment,

illustrates a comparison between the angle of incidence of primary radar waves which arrive on an independent part of the state of the prior art, and the angle of incidence of primary radar waves which arrive on the independent part of said assembly vehicle of the , according to a non-limiting embodiment.

Identical elements, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

The vehicle assembly 1 of a vehicle 2 according to the invention is described with reference to Figures 1 to 4. In one non-limiting embodiment, the vehicle 2 is a motor vehicle. Motor vehicle means any type of motorized vehicle. This embodiment is taken as a non-limiting example in the remainder of the description. In the remainder of the description, vehicle 2 is thus otherwise called motor vehicle 2.

As shown on the , vehicle set 1 includes:
- a radar sensor 10,
- an independent part 11 of said radar sensor 10 which is arranged facing said radar sensor 10.

In a non-limiting embodiment, the radar sensor 10 is a millimeter wave (between 24 GHz and 300 GHz) or microwave (between 300 MHz and 79 GHz) or microwave (between 1 GHz and 300 GHz) sensor. In a non-limiting alternative embodiment, the radar sensor 10 operates at a radar frequency comprised between 76 GHz and 81 GHz.

The radar sensor 10 is configured to scan the exterior environment of the motor vehicle 2, thanks to the emission of primary radar waves R1. As shown on the , the radar sensor 10 thus comprises:
- at least one transmitting antenna 100 configured to transmit primary radar waves R1,
- At least two receiving antennas 101 configured to receive secondary radar waves R2.

The radar sensor 10 further comprises at least one transmitter 103 configured to generate the primary radar waves R1 and at least one receiver 104 configured to process the secondary radar waves R2. In a non-limiting embodiment, a single electronic component can be used for both transmission and reception functions. There will thus be one or more transmitter/receiver called "transceiver" in the Anglo-Saxon language. Said transmitter 103 generates primary radar waves R1 which are subsequently emitted by the transmitting antenna 100, which when they encounter an object 3 (here a pedestrian in the nonlimiting example illustrated) in the external environment of the motor vehicle 2 are reflected on said object 3. The radar waves thus reflected are waves transmitted back to the radar sensor 10. These are the secondary radar waves R2 received by the receiving antennas 101. These are radar waves retransmitted in the direction of the radar sensor 10 In a non-limiting embodiment, the primary radar waves R1 and the secondary radar waves R2 are radio frequency waves. In a non-limiting embodiment, the radar sensor 10 comprises a plurality of transmitters 103 and a plurality of receivers 104.

The transmitting antenna 100 is configured to transmit the primary radar waves R1 generated by the transmitter 103. The receiving antennas 101 are configured to receive the secondary radar waves R2 and communicate them to the receiver 104 which subsequently processes them. There is a phase difference Δϕ between the secondary radar waves R2 received by the receiving antennas 101 which makes it possible to deduce the position of the object 3 with respect to the motor vehicle 2, object 3 which is located in the external environment of the motor vehicle 2. In non-limiting embodiments, the antennas 13 are patch antennas otherwise called in English language "patch antenna" or slot antennas otherwise called in English language "slot antenna".

In a non-limiting embodiment, the antennas 100, 101, the transmitter 103 and the receiver 104 are disposed on a printed circuit board 105. In a non-limiting embodiment, the printed circuit board is a circuit board rigid printed otherwise called PCBA ("Printed Circuit Board Assembly" in the Anglo-Saxon language or a flexible printed circuit board, otherwise called "Flexboard" in the Anglo-Saxon language.

The radar sensor 10 further comprises an electronic control unit 106 configured to control the transmitter 103 and the receiver 104. Since a radar sensor is known to those skilled in the art, it is not described in more detail here.

As shown on the , in the near field (referenced NF in the figure), the form of propagation of the primary radar waves R1 is quasi-spherical. In the far field (referenced FF in the figure), the form of propagation of the primary radar waves R1 is flat. By near field, it is meant that the distance df is less than a threshold S1. This distance df is known as the Fraunhofer distance. We thus have df = ((2 x d2) /λ1).

In a non-limiting example, the threshold S1 is 460 millimeters (mm) for a wavelength λ1 of the primary radar waves R1 of 3.896 mm with d a distance of 30 mm, d being the length of the transmitting antenna 100. In a non-limiting embodiment, the distance df is equal to 400mm. In a non-limiting embodiment, the distance d1 between said at least one transmitting antenna 100 and the primary part 110 is less than or equal to the distance df. Beyond the distance df, the form of propagation of the primary radar waves R1 is considered in the far field FF and as being plane.

In non-limiting embodiments, the radar sensor 10 is positioned in a light device of the motor vehicle 2, behind the front or rear bumper of the motor vehicle 2, behind the grille of the motor vehicle 2, or behind an illuminated logo or No. In non-limiting embodiments, the light device is a headlight or a rear light of the motor vehicle 2.

The radar sensor 10 is positioned opposite the independent part 11. In non-limiting embodiments, the independent part is a radome, an output window of the light device, a logo illuminated or not, or a decorative part.

As illustrated in Figures 1 and 3, the independent part 11 comprises:
- a primary part 110 arranged opposite said at least one transmitting antenna 100,
- a secondary part 111 arranged opposite said at least two receiving antennas 101.

In a non-limiting embodiment, the independent part 11 is made of plastic. In a non-limiting alternative embodiment, the independent part 11 is made of polycarbonate (PC). In other non-limiting embodiments, the independent part 11 is in any other material other than a conductive material, because a conductive material absorbs radar waves.

As shown on the , the primary part 110 comprises a first face 110a, a second face 110b opposite the first face 110a, and has a thickness e1. The first face 110a is arranged opposite the transmitting antenna 100. The primary part 110 follows the form of propagation of said primary radar waves R1 in the near field NF. In the near field NF, the primary radar waves R1 propagate in a quasi-spherical fashion. Thus, the primary part 110 which therefore follows this quasi-spherical shape is curved. This allows the primary radar waves R1 to arrive on the primary part 110, in particular on its first face 110a, with an angle of incidence θ of 0°, i.e. cosθ = 1, as illustrated on the (part b). The primary radar waves R1 therefore arrive perpendicular to the primary part 110 at each point of its first face 110a. Furthermore, in a non-limiting embodiment, the primary part 110 is arranged in a centered manner with respect to the transmitting antenna 100. This allows the primary part 110 to perfectly follow the form of propagation of the primary radar waves R1.

In a non-limiting embodiment, the primary part 110 has a constant radius of curvature Rc (illustrated in the ). This allows the primary radar waves R1 to arrive with an angle of incidence θ which is normal to the primary part 110, in particular to its first face 110a. Indeed, the propagation of the primary radar waves R1 takes place in a quasi-spherical fashion according to a constant radius of curvature Rc' (illustrated on the ). Thus, the radius of curvature Rc of the primary part 110 is equal to the radius of curvature Rc' of the form of propagation of the primary radar waves R1. This makes it possible to obtain a perfectly normal angle of incidence θ. In a non-limiting embodiment, the radius of curvature Rc is between 0.1 millimeter per radian (mm/rad) and 400 mm/rad.

In a non-limiting embodiment, the primary part 110 of the radar sensor 10 is at a distance d1 (illustrated in the ) of the independent part 11. In a non-limiting embodiment, the distance d1 between said at least one transmitting antenna 100 and the primary part 110 is less than or equal to the distance df. In a non-limiting embodiment, the size of the radius of curvature Rc located at each point of the primary part 110, is less than or equal to the distance df, ie at the near field/far field limit. Thus, in a non-limiting example, the distance df is equal to approximately 400 mm. This makes it possible to have a minimum size of the vehicle assembly 1 since the radar sensor 10 is very close to the independent part 11. It will be noted that the radius of curvature Rc located at each point of the primary part 110 can be equal to the transmitter antenna distance 100-piece independent 11.

As shown on the (part a), which illustrates a primary part 310 of the state of the prior art, when the angle of incidence θ is different from 0°, the corresponding refracted angle referenced β in the figure is also different from 0° . The path δ traveled by the parasitic reflections R1' (which are reflected on a first face 310a of the primary part 310 of the independent part) and by the parasitic reflections R1'' (which are reflected on the second face 310b of the primary part 310 of the independent part) is equal to 2necos(r), with e the thickness of the primary part 310 and n the refractive index of the primary part 310. The two series of parasitic reflections R1' and R1'' are in phase opposition and arrive at the radar sensor referenced 40. They create destructive interference. The phase shift between the two series of parasitic reflections R1' and R1'' thus depends on the cosine of the refracted angle β (and therefore on the cosine of the angle of incidence θ) and on the thickness e3 of the primary part 310 .

As shown on the (part b), when the angle of incidence θ is equal to 0°, we have cosθ = 1 and cosβ = 1. The parasitic reflections R1', R1'' of the primary radar waves R1 on the faces 110a, 110b of the independent part 11 also arrive in phase opposition and create destructive interference. The path traveled by the parasitic reflections R1' (which are reflected on the first face 110a of the primary part 110 of the independent part 11) and by the parasitic reflections R1'' (which are reflected on the second face 110b of the primary part 110 independent part 10) is equal to 2ne1, with e1 the thickness of the primary part 110 of the independent part 11. The path thus only depends on the primary thickness e1.

Thus, thanks to the primary part 110 which is curved, one acts on the phase difference between the parasitic reflections R1', R1''. The phase shift between the two series of parasitic reflections R1' and R1'' will no longer depend only on the primary thickness e1 of the primary part 110. In order to completely eliminate these parasitic reflections R1', R1'', the primary part 110 includes a constant primary thickness e1. In a non-limiting embodiment, the primary thickness e1 is between 1 millimeter and 15 millimeters (mm). This makes it possible to have a perfect phase shift of 2π between the parasitic reflections R1' (first series of parasitic reflections) and the parasitic reflections R1'' (second series of parasitic reflections) so that they cancel each other out.

It should be noted that if the primary thickness e1 is not constant, even with a cosθ = 1, the phase difference between the parasitic reflections R1' and the parasitic reflections R1'' will vary due to the primary thickness e1 which varies. There will be a part of the parasitic reflections R1', R1'' which still interferes with the primary radar waves R1, despite the fact that they create destructive interference. The phase shift of will thus not be perfectly 2π. Note that if the primary thickness e1 is constant, but the cosθ is different from 1, the phase difference between the parasitic reflections R1' and the parasitic reflections R1'' will vary. There will be a part of the parasitic reflections R1', R1'' which still interferes with the primary radar waves R1, despite the fact that they create destructive interference. The phase shift will thus not be perfectly 2π. It will also be noted that having a constant primary thickness e1 is simpler to manufacture than a primary part 110 with a variable primary thickness e1.

On the receiving side, as shown in the , the secondary radar waves R2 are received by the receiving antennas 101 in the far field FF. They thus arrive on the receiving antennas 101 in a flat manner. For this purpose, the secondary part 111 is flat. It is therefore not curved like the primary part 110. This allows the secondary radar waves R2 to arrive on the secondary part 111 of the independent part 11 with the same angle of incidence. Thus, there is the same quantity of energy which arrives on the receiving antennas 101. There is a homogeneity of the secondary radar waves R2 which arrive on the receiving antennas 101. If the secondary part 111 were not flat, this would generate errors on the calculation of the phase difference Δϕ between the secondary radar waves R2 and therefore errors on the detection of an object 3.

In a non-limiting embodiment, the secondary part 111 has a constant secondary thickness e2. This avoids having an additional phase shift between the secondary radar waves R2 which would be induced by the material of the secondary part of the independent part 11 when it varies in thickness. This additional phase shift is a phase shift different from the phase shift Δϕ which exists between the secondary radar waves R2 when they arrive at the two receiving antennas 101 (and which will make it possible to deduce the position of an object 3 which is in the external environment of the motor vehicle 2). Such an additional phase shift thus distorts the calculation of the phase shift Δϕ. In a non-limiting embodiment, its secondary thickness e2 is equal to the primary thickness e1 of the primary part 110. This facilitates the manufacture of the entire independent part 11.

Of course, the description of the invention is not limited to the embodiments described above and to the field described above. Thus, in another non-limiting embodiment, the radar sensor 10 comprises more than one transmitting antenna 100 and more than two receiving antennas 101. Thus, in another non-limiting embodiment, if the radar sensor 10 comprises more than two transmitting antennas 100, in this case the independent part 11 comprises two primary parts 110 each arranged opposite each transmitting antenna 100, each primary part 110 having a constant thickness e1 and following the form of propagation in the near field NF of the primary radar waves R1 emitted by each transmitting antenna 100. Thus, in another non-limiting embodiment, the secondary part 111 of the independent part 11 may have a secondary thickness e2 different from that e1 of the primary part 110.

Thus, the invention described has in particular the following advantages:
- it makes it possible to take into account the shape of the primary radar waves R1 emitted in the near field NF and to ensure that the parasitic reflections cancel each other out,
- it makes it possible to cancel the parasitic reflections between them, unlike a solution in which a radar sensor follows the shape of the independent part but does not follow the shape of the radar waves emitted by the radar sensor; it thus prevents the reduction of the signal-to-noise ratio,
- it makes it possible to have a minimum size of the vehicle assembly 1, the independent part 11 being able to be placed close to the radar sensor 10 without causing errors in the detection of an object 3 located in the external environment of the vehicle 2 .

Claims (9)

Vehicle assembly (1), said vehicle assembly (1) comprising a radar sensor (10) and an independent part (11) of said radar sensor (10), said radar sensor (10) comprising at least one transmitting antenna (100) configured to emit primary radar waves (R1) and at least two receiving antennas (101) configured to receive secondary radar waves (R2),
characterized in that said independent part (11) comprises:
- a primary part (110) arranged opposite said at least one transmitting antenna (100) which follows the form of propagation of said primary radar waves (R1) in the near field (NF), and which has a constant primary thickness (e1) , And
- a secondary part (111) arranged opposite said at least two receiving antennas (101) and which is flat. Vehicle assembly (1), according to claim 1, wherein said primary part (110) is curved so that said primary radar waves (R1) have an angle of incidence (θ) which is normal to said primary part (110 ). Vehicle assembly (1) according to any one of the preceding claims, in which said primary part (110) has a constant radius of curvature (Rc). Vehicle assembly (1) according to any one of the preceding claims, in which said secondary part (111) has a constant secondary thickness (e2). Vehicle assembly (1) according to any of the preceding claims, wherein said primary part (110) comprises a radius of curvature (Rc) and said primary part (110) is at a distance (df) from said independent part ( 11), said radius of curvature (Rc) comprising a size less than or equal to said distance (df). A vehicle assembly (1) according to any preceding claim, wherein said independent part (11) is made of plastic. Vehicle assembly (1) according to any one of the preceding claims, in which said independent part (11) is an output window of a vehicle lighting device (2), a logo, a decorative part, or a radome. Independent part (11) of a vehicle assembly (1) comprising a radar sensor (10), characterized in that said independent part (11) comprises:
- a primary part (110) arranged opposite at least one transmitting antenna (100) of said radar sensor (10), which follows the shape of said primary radar waves (R1), which has a constant primary thickness (e1), and which is curved so that said primary radar waves (R1) have an angle of incidence (θ) which is normal to said primary part (110)
- a secondary part (111) arranged facing at least two receiving antennas (101) of said radar sensor (10) which has a constant secondary thickness (e2) and which is flat. Independent part (11) according to the preceding claim, according to which said independent part (11) is an output glass of a vehicle lighting device (2), a logo, a decorative part or a radome.