VEHICLE ASSEMBLY COMPRISING RADAR SENSOR AND LAYER ARRANGEMENT - Patent application

Abstract

A vehicle comprises: a radar sensor (10); and a layer arrangement (11) arranged facing the radar sensor and configured to perform an illumination function, the layer arrangement (11) comprising: a first subassembly (S1) of at least one layer (110) that is reflective in the visible range, each layer (110) having a primary refractive index (n10) and a primary thickness (e10); and a second subassembly (S2) of at least one layer (112) that is transparent in the visible range, each layer (112) having a secondary refractive index (n20), the primary refractive index (n10) being high with respect to the secondary refractive index (n20). and the total thickness (e1) of the first subassembly (S1) of the layer (110) is dimensioned such that there is a phase shift of π modulo 2π between the waves (R11) of the radar wave (R1) incident on the outer surface (S1.1) of the first subassembly (S1) and the waves (R12) reflected by the interface (J12) between the first subassembly (S1) and the second subassembly (S2) as they leave the first subassembly.

Description

[Technical field]

[0001] VEHICLE ASSEMBLY FIELD OF THE DISCLOSURE The present invention is particularly, but not exclusively, applicable to motor vehicles. [Background technology]

[0002] Vehicle assemblies known to those skilled in the art include: - a radar sensor configured to transmit radar waves; a layer arrangement arranged facing the radar sensor, the layer arrangement including a reflective layer having a higher refractive index for radar waves compared to the other layers of the layer arrangement.

[0003] The layer arrangement forms an illuminated logo, and thus the radar sensor is placed behind the illuminated logo and meets the requirements for detecting objects in the environment outside the vehicle.

[0004] One disadvantage of this prior art is that when a radar wave is transmitted by the radar sensor, it travels up to the layer arrangement and is reflected by the layer arrangement. This generates, in particular, three reflected waves, one of the three reflected waves being reflected by the outer surface of the layer arrangement and the other two of the three reflected waves being reflected inside the layer arrangement. The three reflected waves are reflected waves called primary reflected waves that return to the radar sensor. This impedes the propagation of the radar wave. This reduces the signal-to-noise ratio of said radar sensor, thereby causing disturbances in the detection by the radar sensor. The radar sensor loses its detection range. As a result, this can lead to detection errors or non-detection of objects even when said objects are present in the environment outside the vehicle. Summary of the Invention [Problem to be solved by the invention]

[0005] In this context, the present invention aims to propose a vehicle assembly making it possible to overcome the aforementioned disadvantages. [Means for solving the problem]

[0006] To this end, the invention proposes a vehicle assembly for a vehicle, said vehicle assembly comprising: - a radar sensor configured to transmit radar waves in a range of wavelengths; - a layer arrangement arranged facing the radar sensor and configured to perform an illumination function, the layer arrangement comprising: a first subassembly of at least one layer that is reflective in the visible range, each layer having a primary refractive index and a primary thickness; and a second subassembly of at least one layer that is transparent in the visible range, each layer having a secondary refractive index, the primary refractive index being higher in the radar range with respect to the secondary refractive index; Equipped with - a total thickness of the first subassembly of layers is dimensioned such that there is a phase shift of π modulo 2π between radar waves incident on an outer surface of the first subassembly and waves reflected by an interface between the first subassembly and the second subassembly as they exit the first subassembly. According to non-limiting embodiments, the vehicle assembly may further include one or more additional features selected from the following, taken alone or in any technically possible combination:

[0007] According to one non-limiting embodiment, the total thickness of the second subassembly of layers is dimensioned such that there is a phase shift of π modulo 2π between the radar waves incident on the outer surface of the first subassembly and the waves reflected by the outer surface of the second subassembly as they exit the first subassembly.

[0008] According to one non-limiting embodiment, the total thickness of the second subassembly of layers is dimensioned by varying the thickness of only one of the layers of the second subassembly.

[0009] According to one non-limiting embodiment, each layer of the first subassembly has a refractive index that differs from the refractive index of another adjacent layer of the first subassembly by less than 0.1 in the radar region.

[0010] According to one non-limiting embodiment, each layer of the second subassembly has a refractive index that differs from the refractive index of another adjacent layer of the second subassembly by less than 0.1 in the radar region.

[0011] According to one non-limiting embodiment, each layer of the second subassembly has a refractive index that differs from the refractive index of a layer of the first subassembly by more than 0.1 in the radar region.

[0012] According to one non-limiting embodiment, the vehicle assembly includes at least one light source configured to emit visible light that enters the layer arrangement through an edge of one of the layers of the second subassembly of the layer arrangement.

[0013] According to one non-limiting embodiment, the at least one layer that is reflective in the visible region is composed of titanium particles.

[0014] According to one non-limiting embodiment, the layer arrangement forms an illuminated logo or an illuminated front end grille, or forms part of a headlamp.

[0015] According to one non-limiting embodiment, the radar sensor is a millimeter wave or very high frequency or microwave radar sensor.

[0016] According to one non-limiting embodiment, the radar waves are transmitted in a frequency band between 100 MHz and 5 GHz.

[0017] According to one non-limiting embodiment, the illumination function is a lighting and / or signaling function.

[0018] According to one non-limiting embodiment, the second subassembly of layers comprises: an exit layer forming an exit outer lens of the layer arrangement; - Protective layer Equipped with.

[0019] According to one non-limiting embodiment, the first subassembly of layers is a diffusely reflective white subassembly.

[0020] According to one non-limiting embodiment, the total thickness of the first subassembly is determined for an angle of incidence equal to arctan(d1 / (2e4)), where e4 is the distance between the radar sensor and the layer arrangement and d1 is the distance between the transmitting and receiving antennas of the radar sensor.

[0021] The invention further proposes a layer arrangement arranged facing a radar sensor, said radar sensor being configured to transmit radar waves of a range of wavelengths, said layer arrangement being configured to perform an illumination function, comprising a first subassembly of at least one layer that is reflective in the visible range, each layer having a primary refractive index and a primary thickness, and a second subassembly of at least one layer that is transparent in the visible range, each layer having a secondary refractive index, said primary refractive index being high with respect to said secondary refractive index in the radar range, - the total thickness of the first subassembly of layers is dimensioned such that there is a phase shift of π modulo 2π between radar waves incident on an outer surface of the first subassembly and waves reflected by the interface between the first subassembly and the second subassembly as they exit the first subassembly.

[0022] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic diagram of a vehicle assembly according to one non-limiting embodiment of the present invention, the vehicle assembly comprising a radar sensor and a layer arrangement, the layer arrangement comprising a first subassembly of a layer and a second subassembly of a layer. [Diagram 2] 2 is a front view of the vehicle assembly of FIG. 1, according to one non-limiting embodiment, the vehicle assembly further including a light decoupling relief feature according to one non-limiting embodiment. [Diagram 3] FIG. 3 is a schematic diagram of a radar wave transmitted by a radar sensor of the vehicle assembly of FIG. 1 or FIG. 2, according to one non-limiting embodiment, the radar wave generating a reflected wave that is reflected off one surface of the layer arrangement of the vehicle assembly of FIG. 1 or FIG. 2 and within the layer arrangement. [Figure 4] FIG. 3 is a schematic diagram of a radar wave transmitted by a radar sensor of the vehicle assembly of FIG. 1 or FIG. 2, according to one non-limiting embodiment, the radar wave generating a reflected wave that is reflected by two faces of the layer arrangement of the vehicle assembly of FIG. 1 or FIG. 2. [Diagram 5] 3 is a schematic diagram of a layer of a layer arrangement of the vehicle assembly of FIG. 1 or FIG. 2 according to one non-limiting embodiment, the layer arrangement comprising a first subassembly of layers and a second subassembly of layers. [Figure 6] FIG. 4 is a first graph of results showing two reflectivity curves associated with radar waves from the radar sensor of FIG. 1 when a second subassembly of the layer arrangement of FIG. 1 is optimized to minimize the reflected wave of FIG. 3, according to one non-limiting embodiment. [Figure 7] FIG. 4 is a first graph of results showing two reflectivity curves associated with radar waves from the radar sensor of FIG. 1 when a second subassembly of the layer arrangement of FIG. 1 is optimized to minimize the reflected wave of FIG. 3 and when a first subassembly of layers of the layer arrangement of FIG. 1 is optimized to minimize the reflected wave of FIG. 4, according to one non-limiting embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Elements that are identical in structure or function and that appear in several figures use the same reference numerals unless otherwise specified.

[0025] A vehicle assembly 1 of a vehicle 2 according to the present invention will be described with reference to Figs. 1 to 7. The vehicle assembly 1 is also called a vehicle system 1. In one non-limiting embodiment, the vehicle 2 is an automobile. The term automobile means any type of engined vehicle. This embodiment is given as a non-limiting example in the remainder of the description. Thus, in the remainder of the description, the vehicle 2 is also called automobile 2. In one non-limiting embodiment, the vehicle assembly 1 is arranged in the grill of the automobile 2. In another non-limiting embodiment, the vehicle assembly 1 may be integrated into a body part located at the rear of the automobile 2.

[0026] As shown in FIG. 1, a vehicle assembly 1, also referred to as a vehicle device 1, - a radar sensor 10 configured to transmit radar waves R1; a layer arrangement 11 arranged facing said radar sensor 10; Equipped with.

[0027] These elements are described below.

[0028] The radar sensor 10 is described below. As shown in FIG. 1, the radar sensor 10 is arranged facing the layer arrangement 11. In one non-limiting embodiment, the radar sensor 10 is a millimeter wave (between 24 GHz and 300 GHz) or ultra-high frequency (between 300 MHz and 81 GHz) or microwave (between 1 GHz and 300 GHz) radar sensor. In one non-limiting variant, the radar sensor 10 operates at a radar frequency between 76 GHz and 81 GHz. The radar waves R1 are transmitted in a range Δ1 of wavelength λ. In one non-limiting embodiment, the radar waves R1 are transmitted in a frequency band between 100 MHz and 5 GHz. In one non-limiting example, if the radar sensor 10 operates at a radar frequency of 77 GHz, i.e. at a wavelength λ of 3.95 mm and in a frequency band of 1 GHz, the radar sensor 10 thereby operates in a frequency band of 76.5 GHz to 77.5 GHz. Thus, radar waves R1 are transmitted in a frequency range of 76.5 GHz to 77.5 GHz, i.e., in a range Δ1 with a wavelength λ of 3.87 mm to 3.92 mm. In another non-limiting example, if radar sensor 10 operates in a frequency band of 5 GHz at a radar frequency of 78.5 GHz, then radar sensor 10 operates in a frequency band of 76 GHz to 81 GHz. Thus, radar waves R1 are transmitted in a frequency range of 76 GHz to 81 GHz, i.e., in a range Δ1 with a wavelength λ of 3.701 mm to 3.945 mm.

[0029] As shown in Figures 3 and 4, the transmitted radar wave R1 strikes the layer arrangement 11 at an angle of incidence θ. In one non-limiting embodiment, the angle of incidence θ is between 0° and ±30°. The radar sensor 10 thus includes a field of view FOV that varies between -30° and +30°. The center of the field of view FOV is at an angle of 0° relative to the longitudinal axis Ox of the vehicle, also referred to as the vehicle axis Ox. In another non-limiting embodiment, the field of view FOV varies between -90° and +45°. The center of the field of view FOV is at an angle of -45° relative to the vehicle axis Ox, and the angle of incidence θ of the radar wave R1 on the layer arrangement 11 remains close to 0° (the vehicle assembly 1 is then positioned at approximately 45° relative to the vehicle axis Ox).

[0030] The radar sensor 10 is configured to scan the environment outside the motor vehicle 2 by transmitting radar waves R1. Thus, as shown in FIG. at least one transmitting antenna 100 configured to transmit radar waves R1, also called primary radar waves R1; - at least two receiving antennas 101 configured to receive radar waves R2, also called secondary radar waves R2 or return radar waves R2; Equipped with.

[0031] The radar sensor 10 further comprises at least one transmitter 103 configured to generate a primary radar wave R1 and at least one receiver 104 configured to process the returned and received secondary radar wave R2. In one non-limiting embodiment, a single electronic component may be used for both the transmitting and receiving functions. Thus, there will be one or more transceivers. Said transmitter 103 generates a primary radar wave R1, which is subsequently transmitted by the transmitting antenna 100, which, upon encountering an object 3 (here, a pedestrian in the illustrated non-limiting example) in the environment outside the motor vehicle 2, is reflected by said object 3. The thus reflected radar wave is the wave transmitted back to the radar sensor 10. The reflected radar wave is the secondary radar wave R2 received by the antenna 101. The reflected radar wave is the radar wave transmitted back towards the radar sensor 10. In one non-limiting embodiment, the primary radar wave R1 and the secondary radar wave R2 are high frequency. In one non-limiting embodiment, the radar sensor 10 comprises multiple transmitters 103 and multiple receivers 104 .

[0032] A transmitting antenna 100, also referred to as antenna 100, is configured to transmit a primary radar wave R1 generated by a transmitter 103. A receiving antenna 101, also referred to as antenna 101, receives a secondary radar wave R2 and transmits the secondary radar wave R2 to a receiver 104, which is then configured to process the secondary radar wave R2. There is a phase shift between the secondary radar waves R2 received by the receiving antenna 101, which makes it possible to estimate the angular position of an object 3 relative to the motor vehicle 2, said object 3 being located in the environment external to the motor vehicle 2. In a non-limiting embodiment, the antennas 100, 101 are patch or slot antennas.

[0033] In one non-limiting embodiment, the antennas 100, 101, the transmitter 103, and the receiver 104 are disposed on a printed circuit board 105. In one non-limiting embodiment, the printed circuit board is a printed circuit board assembly (PCBA) or a flexible printed circuit board (flexboard).

[0034] The radar sensor 10 further comprises an electronic control unit 106 configured to control the transmitter 103 and the receiver 104. Such radar sensors are known to those skilled in the art and will not be described in further detail here.

[0035] The layer arrangement 11 is described below. As shown in FIG. 1 or FIG. 3 to FIG. 5, the layer arrangement 11 is a first subassembly S1 of at least one layer 110 that is reflective in the visible range, a second subassembly S2 of at least one layer 112; Equipped with.

[0036] The layer arrangement 11 is configured to perform a lighting function. The first subassembly S1 and the second subassembly S2 work together to perform said lighting function. In one non-limiting embodiment, the lighting function is a lighting and / or signaling function. It is a so-called modulated lighting function.

[0037] It should be noted that because Figure 1 is a schematic diagram, only two layers 110 are shown in Figure 1, and only two layers 112 are shown in Figure 1. In the remainder of the description, the first subassembly S1 of layer 110 will also be referred to as the first subassembly S1, and the second subassembly S2 of layer 112 will also be referred to as the second subassembly S2.

[0038] In non-limiting embodiments, the layer arrangement 11 forms an illuminated logo or an illuminated front-end grille or forms part of a headlamp. In these cases, the vehicle assembly 1 comprises one or more light sources 12. Thus, a logo or a front-end grille or a separate relief structure 13 (described below) is illuminated by a plurality of light sources 12. Thus, in one non-limiting embodiment, said vehicle assembly 1 comprises at least one light source 12 configured to emit visible light Lx, also called light Lx or light, which enters said layer arrangement 11 through the edge. In the non-limiting example shown in FIG. 2, the light sources 12 are arranged at the periphery of said layer arrangement 11, at the same height as the layer 112 of the second subassembly S2. In this non-limiting example, the arrangement 11 forms part of a headlamp 5 further comprising an illumination module 50 further having one or more light sources (not shown).

[0039] The light source 12 generates a light beam (not shown) and generates light Lx, which is injected into the transparent layer 112 and reflected by said at least one layer 110. It is noted in particular that one of the transparent layers 112 is configured to act as a light guide for said light Lx, while the other layer 112 is a styling or protective layer (for corrosion protection in one non-limiting example).

[0040] In one non-limiting embodiment, the light source 12 is a semiconductor light source. In one non-limiting embodiment, the semiconductor light source forms part of a light emitting diode. A light emitting diode means, in non-limiting examples, any type of light emitting diode, whether LED, OLED (Organic LED), AMOLED (Active Matrix Organic LED), or even FOLED (Flexible OLED). In another non-limiting embodiment, the light source 12 is a light bulb with a filament.

[0041] As shown in FIG. 1, the first subassembly S1 of the layer 110 is positioned facing the radar sensor 10, while the second subassembly S2 of the layer 112 is positioned adjacent to the first subassembly S1 of the layer 110 and facing the exterior of the motor vehicle 2.

[0042] In a first non-limiting embodiment, the first subassembly S1 is a diffusely reflective subassembly, i.e., the at least one layer 110 is diffusely reflective, and the second subassembly S2 is transparent in the visible range, i.e., layer 112 is transparent to visible light.

[0043] In a second non-limiting embodiment, the first subassembly S1 is a subassembly transparent in the visible range having a light separation relief structure 13, i.e. said at least one layer 110 is transparent to visible light and has a light separation relief structure 13, and the second subassembly S2 is transparent in the visible range, i.e. layer 112 is transparent to visible light.

[0044] The light separating relief structure 13 is configured to separate the light Lx generated by the light source 12. The relief 130 of the light separating relief structure 13 is a local modification of the relief of the surface on which it is located, i.e. here of one of the layers 110 facing the radar sensor 10.

[0045] It should be noted that if the layer 110 is a diffusely reflective white layer, the light Lx does not propagate in this layer 110 but is directly directed towards the exterior of the motor vehicle 2 by the light separation relief structure 13, which is arranged to direct the light Lx along the vehicle axis Ox of the motor vehicle 2, thereby enabling it to perform a lighting function. In a non-limiting embodiment, the light separation relief structure 13 is made up of a plurality of - minidiscs, also called microlenses, obtained by laser bombardment, and / or - Micro-cones, and / or - Micro-Cone Prism, and / or - Mini Prism, and / or - Embossing Equipped with.

[0046] The relief 130 is thus a minidisc and / or a micro-cone and / or a micro-cone prism and / or a mini-prism and / or an embossing. Such a surface is often described as a diffusing surface or a microlens surface.

[0047] The first subassembly S1 of layers is configured to transmit the light Lx generated by the light source 12 towards the exterior of the motor vehicle 2. Each layer 110 of the first subassembly S1 has a primary refractive index n10, also referred to as the refractive index n10, and a primary thickness e10, also referred to as the thickness e10. The first subassembly S1 has a total thickness e1 made up of all the thicknesses e10. The layers 110 each have a refractive index n10 that is very close to the refractive index n10 of another adjacent layer 110, also referred to as continuous. In one non-limiting embodiment, each layer 110 has a refractive index n10 that differs from the refractive index n10 of the adjacent layer 110 of said first subassembly S1 by less than 0.1. This threshold value further allows for negligible internal reflection waves between the layers 110 of the first subassembly S1. In one non-limiting variation of this non-limiting embodiment, the difference is less than 0.05.

[0048] The second subassembly S2 of layers is configured to propagate visible light Lx within the layers 112, which allows for increased efficiency of the lighting function. Each layer 112 of the second subassembly S2 has a secondary refractive index n20, also referred to as refractive index n20, and a secondary thickness e20, also referred to as thickness e20. The second subassembly S2 has a total thickness e2 composed of all the thicknesses e20. The layers 112 each have a refractive index n20 that is very close to the refractive index n20 of the adjacent layer 112, also referred to as continuous. In one non-limiting embodiment, each layer 112 has a refractive index n20 that differs from the refractive index n20 of the adjacent layer 112 of said second subassembly S2 by less than 0.1. This threshold value also allows for negligible internal reflection waves between the layers 112 of the second subassembly S2. In the illustrated non-limiting example, the second subassembly S2 comprises two layers 112a and 112b, namely the layer 112a acting as a light guide for the light Lx, and the layer 112b being a protective layer. The exit layer 112a has a secondary refractive index n20a that differs from the secondary refractive index n20b of the adjacent protective layer 112b by less than 0.1 in the radar region. In one non-limiting variant of this non-limiting embodiment, the difference is less than 0.05. In the illustrated non-limiting example, the secondary refractive index n20a is equal to 1.6 and the secondary refractive index n20b is equal to 1.62.

[0049] The layer sequence 11 therefore has a total thickness e0=e1+e2, as shown in FIG.

[0050] The primary refractive index n10 is high relative to the secondary refractive index n20 in the radar region. By "high" we mean that the layers 110 and 112 cannot be considered equivalent layers. In one non-limiting embodiment, therefore, each layer 112 of the second subassembly S2 has a refractive index n20 that differs from the refractive index n10 of the layer 110 of said first subassembly S1 by more than 0.1. Thus, there is a refractive index difference of more than 0.1 in the radar region.

[0051] In one non-limiting embodiment shown in FIG. 5, the first subassembly S1 of layers 110 comprises a single layer 110. In one non-limiting embodiment, the layer 110 is a layer of white reflective material. The first subassembly S1 of layers 110 is therefore a diffusely reflective white layer. This allows maximizing the efficiency of the light source 12, which would otherwise lose half of the visible light Lx. In one non-limiting variant, the material is made up of particles of titanium TiO2. In one non-limiting example, it is a plastic with a titanium oxide dopant. It should be noted that the more titanium oxide doping, the more optically reflective the material is and therefore the higher the refractive index in the radar range. In one non-limiting embodiment, the doped plastic is PC (polycarbonate). The titanium doping is - Using a well-controlled process that makes it possible to obtain an even distribution on large parts such as the front end grille, unlike a coat of paint; - And, unlike paint coatings, it is possible to modify the reflectance and thereby control the refractive index. The titanium oxide-doped plastic layer 110 contributes to the performance of the lighting function. It should be noted that the titanium also makes it possible to protect the titanium-doped plastic. The layer 110 is a layer that is transparent to the radar waves R1, R2, but not to the visible light Lx, i.e. the visible light Lx is largely reflected by the layer 110 (in particular by the interface J12, which will be described below), so that the layer 110 passes the radar waves R1 but does not pass the visible light Lx. In one non-limiting embodiment, its thickness e10 is a few millimeters. In one non-limiting embodiment, the primary refractive index n10 of this layer 110 is equal to 2. It should be noted that the higher the concentration of particles of titanium TiO2, the more reflective the layer 110 is and the higher the primary refractive index n10. This non-limiting embodiment of a single layer 110 is provided as a non-limiting example in the remainder of the description.

[0052] In one non-limiting embodiment shown in FIG. 5, the second subassembly S2 of the layer 112 includes: an exit layer 112a forming the exit outer lens of the layer sequence 11; a protective layer 112b that makes it possible to prevent yellowing of the plastic of the exit outer lens 112a by blocking ultraviolet light; Equipped with.

[0053] In one non-limiting embodiment, the protective layer 112b can also be an anti-scratch layer. In one non-limiting embodiment, the exit layer 112a is made of PC. It is a layer that is transparent to both radar waves R1, R2 and visible light Lx. In one non-limiting embodiment, the protective layer 112b has a thickness e20b of substantially 50 micrometers. In one non-limiting embodiment, the protective layer 112b is a deposit of a protective varnish.

[0054] 3 to 5, when a radar wave R1 is transmitted by the radar sensor 10, the radar wave R1 travels to the layer arrangement 11. The radar wave R1 is reflected by the layer arrangement 11 and generates four reflected waves R11, R12, R13, and R14, i.e., - R11, the wave reflected by the outer surface S1.1 of the first subassembly S1, R12, a wave reflected inside the layer sequence 11 by the interface J12 between the first subassembly S1 and the second subassembly S2, R13 (shown in FIG. 5 drawing (a)), a wave reflected inside the layer arrangement 11 by the interface J22 between the two layers 112a and 112b of the second subassembly, - R14, the wave reflected at the outer surface S2.1 of the second subassembly S2 Causes the following to occur.

[0055] It should be noted that reflected waves R12, R13, and R14 include incident portions that pass through layers 110 for R12, 110 and 112a for R13, and 110, 112a, and 112b for R14, before reflection.

[0056] In other words, there is a wave reflected by each refractive surface defined between two different adjacent layers. Four reflected waves R11 to R14 are reflected waves called primary reflected waves and return to the radar sensor 10. These are parasitic reflections that disturb the radar wave R1. The radar wave R1' is the radar wave that leaves the layer arrangement 11 and is shown in Figures 3 and 4. Due to these parasitic reflections, the radar wave R1 is attenuated to a greater extent compared to the radar wave R1 entering the layer arrangement 11. Thus, the efficiency of the radar sensor 10 is reduced. To overcome this problem, the thicknesses e1 and then e2 are successively optimized, as will be seen below.

[0057] The reflection strength varies for each reflected wave. In the illustrated non-limiting example, the reflection strength of R13 is negligible because the difference in refractive index between n20a and n20b is very small, and therefore Fresnel reflections are negligible. Its reflection strength is less than 0.5% for radar wave R1, while the reflection strengths of reflected waves R11, R12, and R14 vary between 3% and 8% in one non-limiting example. Reflected wave R13 has little effect on the transmission of radar wave R1, but reflected waves R11, R12, and R14 disrupt radar wave R1.

[0058] If the first subassembly of layers 110 comprises a plurality of layers 110, the layers 110 each have a refractive index n10 that is very close to the refractive index n10 of another adjacent layer 110, in other words, when they are continuous, all of the layers 110 of the first subassembly S1 have an equivalent refractive index n eq1 Note that the refractive index difference between the first and second layers may be considered to be equivalent to a single equivalent layer of total thickness e1 having a refractive index of less than 0.1 (as shown in Figures 1, 3, and 4). Recall that in the given non-limiting example, the refractive index difference is less than 0.1.

[0059] When the layers 112 each have a refractive index n20 that is very close to the refractive index n20 of another adjacent layer 112, in other words, when they are continuous, all of the layers 112 of the second subassembly S2 have an equivalent refractive index n eq2Note that this may be considered equivalent to a single equivalent layer of total thickness e2 with a refractive index of 0.1 or less (as shown in Figures 1, 3, and 4). Recall that in the given non-limiting example, the refractive index difference is less than 0.1.

[0060] Recall that these two secondary refractive indices n20a and n20b are very far from the primary refractive index n10 in terms of value. There is a large jump in the refractive index. Therefore, there can be no equivalent refractive index between the two subassemblies S1 and S2 unless the layer 110 has a thickness e10 that is significantly smaller than the radar wave R1 and negligible compared to the thickness e2 of the layer 112, which is not the case. Significantly smaller means e10=λ / 10.

[0061] In addition, since n10 is significantly larger than n20, there cannot be an equivalent refractive index between the two subassemblies S1 and S2.

[0062] Note that if n10 is very close or equal to n20, an equivalent index of refraction may exist, but this is also not the case. Due to the large refractive index jump between n10 and n20, it is not possible for an equivalent index of refraction to exist between the first subassembly S1 and the second subassembly S2 and for the thickness e0 to be optimized.

[0063] Conversely, as shown in FIGS. 1, 3, and 4, the second subassembly S2 has an equivalent refractive index n eq2 has.

number

[0064] The same principle applies to the first subassembly S1 if it includes multiple layers 110 with very similar refractive indices n10. eq1 It should be noted that the refractive index n can be calculated from the dielectric constants of the layers. This calculation is known to those skilled in the art and will not be described here.

[0065] Equivalent refractive index n eq2 In the calculation of R, the reflected wave R13, which has a very low reflection intensity and can therefore be ignored, is no longer taken into account. Thus, as shown in drawing (b) of FIG. 5, the reflected waves R11, R12 and R13 continue to disturb the radar sensor 10. Thus, the radar wave R1 is reflected by the layer arrangement 11 and generates three reflected waves R11, R12, R13 with high reflection intensities, i.e. most of their energy returns to the radar sensor 10. In this case, there are reflection intensity values ​​equal to:

number

[0066] The minimum reflection intensity value I(M) is obtained when the different layers of the two subassemblies S1, S2 are optimized so that they, separately, cause a phase shift of π modulo 2π, so that there is destructive interference between the terms R11 and R14 and between R11 and R12, respectively. Therefore, to minimize the parasitic waves R11, R12, and R14, R11 and R12 must be in opposite phase to create destructive interference, and R11 and R14 must also be in opposite phase to create destructive interference. In this way, the maximum reflection, i.e. the phenomenon of interference by R11, R14, is optimized. It should be noted that although the terms R12 and R14 remain in constructive phase, it has significantly less impact than the sum of the other two terms, since the terms R12 and R14 have a lower intensity than the terms R11 and R14 and the terms R11 and R12.

[0067] For this purpose, in order to reduce the parasitic waves and improve the transmission of the radar wave R1, the layers 112 of the second subassembly S2 can be considered as equivalent layers when the refractive index difference between the different layers 112 is small, so that this equivalent layer is dimensioned to have a phase shift of π modulo 2π between R11 and R14. Conversely, if there is a large refractive index difference between two successive layers, they cannot be considered as equivalent layers. This is the case for the layer 110 and the equivalent layer formed by the layers 112a and 112b. In this case, each non-equivalent layer must be optimized separately in order to reduce the parasitic waves and improve the transmission of the radar wave R1. In this case, each non-equivalent layer must cause a phase shift of π modulo 2π.

[0068] How destructive interference is achieved between R11 and R12 will now be explained. As will be explained below, thickness e1 is optimized for this purpose.

[0069] The total thickness e1 of the first subassembly S1 of the layer 110 is dimensioned such that there is a phase shift of π modulo 2π between R11 and R12. In other words, the total thickness e1 of the first subassembly S1 of the layer 110 is dimensioned such that there is a phase shift of π modulo 2π between the wave R11 of the radar wave R1 incident on the outer surface S1.1 of the first subassembly S1 and the wave R12 reflected by the interface J12 between said first subassembly S1 and said second subassembly S2 when they leave said first subassembly S1.

[0070] If the angle of incidence θ is different from 0°, the corresponding angle of refraction r is also different from 0°.

[0071] The phase difference Δφ, also called the phase shift Δφ, between these two reflected waves R11 and R12 is equal to:

number

[0072] sin(θ)=n eq1 ×sin(r), we get the following.

number

number

[0073] Considering that the reflected waves R11 and R12 return towards the radar sensor 10, they cause disturbances to the radar sensor 10, i.e. attenuation of the signal-to-noise ratio. To eliminate these disturbances, the total thickness e1 of the first subassembly S1 will be defined such that the reflected waves R11 and R12 are in antiphase to create destructive interference. To obtain destructive interference, the phase difference Δφ between the two reflected waves R11 and R12 must be equal to π modulo 2π. Thus, Δφ=(2m+1)*π, where m is a natural integer. Hence, we obtain:

number

[0074] For any value of the angle r, the equation e1 = mλ / (2n eq1 Note that the function of the wavelength λ of the range Δ1 is m times the effective refractive index n of the first subassembly S1 of the layer 110. eq1 The refractive index is then scaled to be twice the refractive index of the radar wave R1 multiplied by the cosine of the refraction angle r corresponding to the incidence angle θ of the radar wave R1, where m is an integer. Therefore, the equivalent refractive index n eq1 and the wavelength λ used in the operating frequency range of the radar sensor 10, the total thickness e1 of the first subassembly S1 can be determined such that the reflected waves R11 and R12 cancel each other. In one non-limiting embodiment, the selected wavelength λ is located in the middle of the range Δ1.

[0075] The ideal total thickness e1 is defined when the angle of incidence is equal to 0 and m is equal to 1. When θ=0, r=0. As a result, for m=1, the ideal total thickness e1 of the first subassembly S1 is therefore e1=λ / (2n eq1 In other words, e1=λ / (2n10) in the non-limiting example of a single layer.

[0076] Therefore, the total thickness e1 is the ideal total thickness e1 = λ / (2n eq1 ) or e1=mλ / (2n eq1 cos(r)).

[0077] In one non-limiting embodiment, the first subassembly S1 of layers has a total thickness e1 between 0.8 and 1.2 times said ideal total thickness e1. This range of values ​​takes into account the possible emission angles of the radar sensor 10. The possible values ​​of the incidence angle θ are defined in the technical specifications of the radar sensor 10, which means that the possible values ​​of the incidence angle θ are the field of view of the radar sensor 10. In one non-limiting example, the incidence angle θ is between 0° and ±30°. This range of values ​​from 0.8 to 1.2 makes it possible to take into account the manufacturing tolerances of the total thickness e0. It is noted that, in the given non-limiting example, the thickness e10 of the layer 110 of white reflective material made up of particles of titanium TiO2 is easy to manage with regard to the industrial process involved.

[0078] It should be noted that there is a value of the incidence angle θ at which the reflected radar waves R11 and R12 cause maximum disturbance to the receiving antenna 101 of the radar sensor 10. This incidence angle θ is called the critical incidence angle θ. In one non-limiting embodiment, this value is equal to θ=arctan(d1 / (2e4)), where d1 is the distance between the transmitting antenna 100 and the receiving antenna 101, and e4 is the distance between the radar sensor 10 and the layer arrangement 11, as shown in FIG. 3. Thus, in one non-limiting embodiment, a value of the total thickness e1 is determined for an incidence angle θ equal to arctan(d1 / (2e4)). It should be noted that in one non-limiting example, the midpoint of the receiving antenna 101 is utilized to calculate d1.

[0079] Therefore, the total equivalent refractive index n eq1 Depending on the value of and the wavelength λ used in the operating frequency range of the radar sensor 10 (between 76 GHz and 81 GHz in the given non-limiting example), it is possible to determine the value of the total thickness e1 so that the primary reflected waves R11 and R12 cancel each other out. Thus, the receiving antenna 101 experiences less noise. A better signal-to-noise ratio is achieved.

[0080] Due to the optimization of the thickness e1, and because the layers 110 and 112 are parallel to each other, the path traveled in the thickness e1 between the radar wave R1 and the reflected wave R14 is the same, and therefore the radar wave R1 and the reflected wave R14 hit the interface S1.1 and the interface J1.2, respectively, at the same angle of incidence. Furthermore, therefore, there is a phase shift equal to π modulo 2π between the incident part of the reflected wave R14 passing through the first subassembly S1 (i.e., layer 110) on the outward path and the part of the reflected wave R14 passing through the first subassembly S1 (i.e., layer 110) on the return path. These two parts therefore cancel each other out. It is then sufficient that there is destructive interference between the reflected wave R11 and the reflected wave R14 in the second subassembly S2. How destructive interference is achieved between R11 and R14 will now be explained. For this purpose, the thickness e2 is optimized (after the thickness e1 has been optimized), as will be described below.

[0081] The total thickness e2 of the second subassembly S2 of the layer 112 is dimensioned such that there is a phase shift of π modulo 2π between R11 and R14. In other words, the total thickness e2 of the second subassembly S2 of the layer 112 is dimensioned such that there is a phase shift of π modulo 2π between the wave R11 of the radar wave R1 incident on the outer surface S1.1 of the first subassembly S1 and the wave R14 reflected by the outer surface S2.1 of the second subassembly S2 when they leave said first subassembly S1.

[0082] If the angle of incidence θ is different from 0°, the corresponding angle of refraction r is also different from 0°.

[0083] The phase difference Δφ, also called the phase shift Δφ, between the two reflected waves R11 and R14 is equal to:

number

[0084] sin(θ)=n eq2 ×sin(r), we get the following.

number

number

[0085] Considering that the reflected waves R11 and R14 return towards the radar sensor 10, they cause disturbances to the radar sensor 10, i.e. attenuation of the signal-to-noise ratio. To eliminate these disturbances, the total thickness e2 of the second subassembly S2 will be defined such that the reflected waves R11 and R14 are in antiphase to create destructive interference. To obtain destructive interference, the phase difference Δφ between the two reflected waves R11 and R14 must be equal to π modulo 2π. Thus, Δφ=(2m+1)*π, where m is a natural integer. Hence, we obtain:

number

[0086] For any value of the angle r, the equation e2 = mλ / (2n eq2Note that the function of the wavelength λ of the range Δ1 is m times the effective refractive index n of the second subassembly S2 of the layer 112. eq2 The refractive index is then scaled to be twice the refractive index of the radar wave R1 multiplied by the cosine of the refraction angle r corresponding to the incidence angle θ of the radar wave R1, where m is an integer. Therefore, the equivalent refractive index n eq2 and the wavelength λ used in the operating frequency range of the radar sensor 10, the total thickness e2 of the second subassembly S2 can be determined such that the reflected waves R11 and R14 cancel each other. In one non-limiting embodiment, the selected wavelength λ is located in the middle of the range Δ1.

[0087] The ideal total thickness e2 is defined when the angle of incidence is equal to 0 and m is equal to 1. When θ=0, r=0. As a result, at m=1, the ideal total thickness e2 of the second subassembly S2 is therefore e2=λ / (2n eq2 ) For r=0°, it is cos(r)=1.

[0088] Therefore, the total thickness e2 is the ideal e2=λ / (2n eq2 ) or e2=mλ / (2n eq2 cos(r)). Adjusting the total thickness e2 does not change the optical performance of the illuminated logo.

[0089] Thus, the total thickness e2 of the second subassembly S2 of the layer 112 is such that, at an angle of incidence θ equal to zero, the total thickness e2 divides said wavelength λ by the equivalent refractive index n eq2 If the angle of incidence θ is different from zero, then e2 = mλ / (2n eq2 cos(r)) This formula applies for any value of angle r.

[0090] In one non-limiting embodiment, to optimize e2, the thickness of only one of the layers 112 of said second subassembly S2 is changed. This simplifies the optimization process. In one non-limiting embodiment, the layer into which the light Lx is injected serves as a light guide for said light Lx to be modified. It should be noted that in practice, therefore, the thickness e20a of the exit layer 112a will be adjusted. The thickness e20b of the protective layer 112b cannot be adjusted, since it is already very thin. In practice, therefore, the thickness e20 of only one layer 112 is adjusted, i.e. the layer that is easiest to inject or the layer made of the cheapest material.

[0091] In one non-limiting embodiment, the second subassembly S2 has a total thickness e2 between 0.8 and 1.2 times the ideal total thickness e2. This range of values ​​takes into account the possible emission angles of the radar sensor 10. The possible values ​​of the incidence angle θ are defined in the technical specifications of the radar sensor 10, which means that the possible values ​​of the incidence angle θ are the field of view of the radar sensor 10. In one non-limiting example, the incidence angle θ is between 0° and ±30°. This range of values ​​from 0.8 to 1.2 makes it possible to take into account the manufacturing tolerances of the total thickness e2.

[0092] It should be noted that there is a value of the incidence angle θ at which the reflected radar waves R11 and R14 cause maximum disturbance to the receiving antenna 101 of the radar sensor 10. This incidence angle θ is called the critical angle θ. In one non-limiting embodiment, this value is equal to θ=arctan(d1 / (2e4)), where d1 is the distance between the transmitting antenna 100 and the receiving antenna 101, and e4 is the distance between the radar sensor 10 and the layer arrangement 11, as shown in FIG. 4. Thus, in one non-limiting embodiment, a value of the total thickness e2 is determined for an incidence angle θ that is equal to arctan(d1 / (2e4)). It should be noted that in one non-limiting example, the midpoint of the receiving antenna 101 is utilized to calculate d1.

[0093] Therefore, the total equivalent refractive index n eq2Depending on the value of and the wavelength λ used in the operating frequency range of the radar sensor 10 (between 76 GHz and 81 GHz in the given non-limiting example), it is possible to determine the value of the total thickness e2 so that the primary reflected waves R11 and R14 cancel each other out. Thus, the receiving antenna 101 experiences less noise. A better signal-to-noise ratio is achieved.

[0094] FIG. 6 shows a graph of the results after optimizing the second subassembly S2 of the layer arrangement 11 to minimize the influence of the reflected waves R11 and R14 on the radar wave R1, but without the optimization of the first subassembly S1 of the layer arrangement 11, the influence of the reflected waves R11 and R12 on the radar wave R1 still exists. Thus, R11 and R14 generate destructive interference between them, while R11 and R12 generate constructive interference between them. The incidence angle θ is shown on the x-axis and the reflection intensity IRL in decibels (dB) is shown on the y-axis. For two incidence angles θ at 76 GHz and 77 GHz, there are two curves C1, C2, respectively.

[0095] FIG. 7 shows a graph of the result after optimizing the second subassembly S2 of the layer arrangement 11 to minimize the influence of the reflected waves R11 and R14 on the radar wave R1 and optimizing the first subassembly S1 of the layer arrangement 11 to minimize the influence of the reflected waves R11 and R12 on the radar wave R1. Thus, R11 and R14 generate destructive interference between them, and R11 and R12 also generate destructive interference between them. The incidence angle θ is shown on the x-axis and the reflection intensity IRL in decibels (dB) is shown on the y-axis. For two incidence angles θ at 76 GHz and 77 GHz, there are two curves C1, C2, respectively.

[0096] In the graph of Figure 6, when only the disturbances due to reflected waves R11 and R14 are processed, there is an average reflection strength IRL of -10 dB, whereas in the graph of Figure 7, when the disturbances due to reflected waves R11 and R12 are processed in addition to the disturbances due to reflected waves R11 and R14, there is an average reflection strength of -16 dB. Thus, when the disturbances due to reflected waves R11 and R12 and the disturbances due to reflected waves R11 and R14 are processed, there is a gain of 6 dB.

[0097] Of course, the description of the present invention is not limited to the above-mentioned embodiment and the above-mentioned field. Thus, in another non-limiting embodiment, the radar sensor 10 comprises two or more transmitting antennas 100 and three or more receiving antennas 101. Thus, in one non-limiting embodiment, the thickness e2 may be dimensioned before the thickness e1 or may be dimensioned in parallel.

[0098] The described invention therefore has, inter alia, the following advantages: - it makes it possible to minimize the primary reflected waves R11, R12 and R14 reflected towards the radar sensor 10. Thus, the signal-to-noise ratio of said radar sensor 10 is no longer low. The transmission of the radar wave R1 is improved, It makes it possible to minimize the reflected waves R11, R12 and R14 by modifying the total thickness e1 and the total thickness e2, and therefore by modifying the diffuse reflective white layer 110 and by modifying the transparent layer 112. - It makes it possible to minimize the waves R11 and R12 reflected between two inequivalent layers with significantly different reflective indices.

Claims

1. A vehicle assembly (1) for a vehicle (2), said vehicle assembly (1) comprising: a radar sensor (10) configured to transmit radar waves (R1) in a range (Δ1) of wavelengths (λ); a layer arrangement (11) arranged facing said radar sensor (10) and configured to perform an illumination function, said layer arrangement (11) comprising a first subassembly (S1) of at least one layer (110) that is reflective in the visible range, each layer (110) having a primary refractive index (n10) and a primary thickness (e10), and a second subassembly (S2) of at least one layer (112) that is transparent in said visible range, each layer (112) having a secondary refractive index (n20), said primary refractive index (n10) being higher in the radar range with respect to said secondary refractive index (n20), a vehicle assembly (1), characterized in that the total thickness (e1) of said first subassembly (S1) of said layer (110) is dimensioned such that there is a phase shift of π modulo 2π between the waves (R11) of said radar wave (R1) incident on the outer surface (S1.1) of said first subassembly (S1) and the waves (R12) reflected by the interface (J12) between said first subassembly (S1) and said second subassembly (S2) when they leave said first subassembly (S1).

2. 2. The vehicle assembly (1) of claim 1, wherein the total thickness (e2) of the second subassembly (S2) of the layer (112) is dimensioned such that there is a phase shift of π modulo 2π between the waves (R11) of the radar waves (R1) incident on the outer surface (S1.1) of the first subassembly (S1) and the waves (R14) reflected by the outer surface (S2.1) of the second subassembly (S2) as they leave the first subassembly (S1).

3. 3. The vehicle assembly (1) according to claim 2, wherein the total thickness (e2) of the second subassembly (S2) of layers (112) is dimensioned by varying the thickness of only one of the layers (112) of the second subassembly (S2).

4. 4. The vehicle assembly (1) according to claim 1, wherein each layer (110) of the first subassembly (S1) has a refractive index (n10) that differs from the refractive index (n10) of another adjacent layer (110) of the first subassembly (S1) by less than 0.1 in the radar region.

5. 5. The vehicle assembly (1) according to claim 1, wherein each layer (112) of the second subassembly (S2) has a refractive index (n20) that differs from the refractive index (n20) of another adjacent layer (112) of the second subassembly (S2) by less than 0.1 in the radar region.

6. 6. The vehicle assembly (1) according to claim 1, wherein each layer (112) of the second subassembly (S2) has a refractive index (n20) that differs from the refractive index (n10) of the layer (110) of the first subassembly (S1) by more than 0.1 in the radar region.

7. 7. The vehicle assembly (1) according to any one of claims 1 to 6, wherein the vehicle assembly (1) comprises at least one light source (12) configured to emit visible light (Lx) that enters the layer arrangement (11) through an edge of one of the layers (112) of the second subassembly (S2) of the layer arrangement (11).

8. 8. Vehicle assembly (1) according to any one of the preceding claims, wherein the at least one layer (110) that is reflective in the visible range is made up of particles of titanium (TiO2).

9. 9. Vehicle assembly (1) according to any one of the preceding claims, wherein the layer arrangement (11) forms an illuminated logo or an illuminated front-end grille or forms part of a headlamp.

10. a layer arrangement (11) arranged facing a radar sensor (10), the radar sensor (10) being configured to transmit radar waves (R1) in a range (Δ1) of wavelengths (λ), the layer arrangement (11) being configured to perform an illumination function, the layer arrangement (11) comprising: a first subassembly (S1) of at least one layer (110) that is reflective in the visible range, each layer (110) having a primary refractive index (n10) and a primary thickness (e10); and a second subassembly (S2) of at least one layer (112) that is transparent in the visible range, each layer (112) having a secondary refractive index (n20), the primary refractive index (n10) being high with respect to the secondary refractive index (n20), a layer arrangement (11), characterized in that the total thickness (e1) of the first subassembly (S1) of the layer (110) is dimensioned such that there is a phase shift of π modulo 2π between the waves (R11) of the radar wave (R1) incident on the outer surface (S1.1) of the first subassembly (S1) and the waves (R12) reflected by the interface between the first subassembly (S1) and the second subassembly (S2) when they leave the first subassembly (S1).

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