Waveguide structure radar sensor

Abstract

TITLE: Radar Sensor with Waveguide Structure A radar sensor having a (10; 54; 96) waveguide structure for guiding microwave signals, characterized in that the (10; 54; 96) waveguide structure is a 3D printed product. Figure 1

Description

Title of the invention: Radar sensor with waveguide structure FIELD OF THE INVENTION

[0001] The present invention relates to a radar sensor with a waveguide structure for conducting microwave signals.

[0002] In particular, the invention relates to a radar sensor of a driving assistance system for equipping motor vehicles. STATE OF THE ART

[0003] Document DE 102018 203 106 A1 describes an example of a radar sensor with a waveguide structure, namely, a waveguide antenna.

[0004] Radar sensor waveguide structures are currently manufactured by producing several shaped metal components whose surface has a determined pattern of cavities which then constitute the cavities of the waveguide. The shaped components are then joined together so that the cavities are turned towards each other and are aligned to complete each other by forming closed cavities. It is also possible to produce the shaped parts by injection of plastic materials and then to metallize the walls of the cavities.

[0005] A variant of the manufacturing process consists of milling the hollows intended to form the cavities in solid plates and then assembling several such plates.

[0006] Document US 10128 567 B2 describes a waveguide antenna for a radar sensor comprising several groups of emission orifices located in a common plane. The planes are however inclined relative to each other, so that with a single radar sensor radar signals are emitted in different directions to have a wider field of vision. The production of such waveguide structures with several emission directions is however relatively complicated.

[0007] PURPOSE OF THE INVENTION

[0008] The present invention aims to develop a radar sensor having a waveguide structure which is simple to manufacture and offers greater possibilities of shape and arrangement of the waveguides.

[0009] DISCLOSURE AND ADVANTAGES OF THE INVENTION

[0010] To this end, the invention relates to a radar sensor having a waveguide structure for guiding microwave signals, a sensor characterized in that the waveguide structure is a 3D printing product.

[0011] 3D printing methods are known with which three-dimensional objects can also be produced from metal. For example, document US 1,052,689 B2 describes a printer which emits droplets of molten metal according to the principle of an inkjet printer on a substrate. To do this, a magnetic field is applied to the molten product. To generate the metal droplets, a current pulse is passed through the molten metal pool so that a Lorentz force acts on the liquid metal and expels the molten metal through a nozzle.

[0012] A 3D printing method is also known which consists of freezing, by stereolithography with laser radiation, a starting material which is initially liquid. This method makes it possible to produce cavities without having to fill the cavity with a filling material.

[0013] The production of waveguide structures by a 3D printing process offers a series of advantages. On the one hand, this process allows the production of objects with complex shapes that would be practically impossible with other manufacturing techniques. Another advantage is that all parts of the waveguide structure are connected by a material bond so that it is no longer necessary to assemble several shaped parts or plates. This avoids the difficulty of defective contact at the junctions between electrically conductive wall segments of the waveguide. In addition, the waveguides can be produced with very thin walls, which represents a saving in material and weight. In addition, it is easier to shape the waveguide structures according to customer specifications.For example, company logos, serial numbers or similar information can also be printed directly into the waveguide structure.

[0014] The invention also relates to a method for producing a radar sensor whose waveguide structure is obtained by a 3D printing method.

[0015] The cavities of the waveguide structures can thus be produced by first introducing a filling material into the cavities initially opened during the printing process, this material then serving as a support for printing a wall which terminates the top of the cavity. The filling material is capable of flowing at least under certain conditions, for example, at high temperature, which will then allow it to be removed from the waveguide structure.

[0016] The filling material can, however, also be a dielectric material which only very slightly dampens the microwave radiation and therefore remains in the waveguide structure.

[0017] Typically, the waveguide structure is on a board fitted with the electronic components of the radar sensor. In the 3D metal printing process, a solder surface can be produced on the waveguide structure, which can then be soldered to the board. Fastening members such as, for example, pegs, snap fasteners, hooks, pressure-fitting elements or the like can also be printed on the waveguide structure, with which fix the waveguide structure to the plate. Sintering processes can also be used, in which microstructures are formed on the surfaces to be connected, and these microstructures then bond with each other.

[0018] Attachment structures can also be printed to attach a radome or other component to the waveguide structure.

[0019] In principle, it is also possible to use the board directly as a printing support for the waveguide structure. This variant is, in particular, advantageous if the board only receives electronic components on one side and the waveguide structure is on the other side of the board.

[0020] According to one embodiment, the 3D printing method is a multi-component printing method with which, in addition to a metal component, non-metallic components, for example, a plastic material, are also printed. In this case, it is, for example, possible to produce relatively thin walls of the waveguide made of metal and to stiffen the structures with printed components made of plastic, which provides high stability with low weight. This method can also be used to close emission openings of the waveguides with a material transparent to microwave radiation, which avoids the use of a radome. It is also possible to print the filling material simultaneously while printing the walls of the waveguide.

[0021] The 3D printing process is particularly suitable for producing waveguide antennas whose emission holes have different orientations. This makes it possible to produce a radar sensor with a wide field of vision that combines several orientation functions, which, until now, was only achievable by a combination of several radar sensors.

[0022] The 3D printing process also makes it possible to produce structures whose waveguides intersect. This considerably facilitates the surface-developed waveguide antenna feed; this considerably reduces the space requirement of the waveguide antenna feed lines.

[0023] Similarly, the 3D printing process also makes it possible to develop cooling structures such as cooling ribs or fins, directly on the waveguide structure. Brief description of the drawings

[0024] The present invention will be described below in more detail using examples of a radar sensor with a waveguide structure shown in the accompanying drawings in which:

[0025] [Fig. 1] perspective view of a waveguide antenna for a radar sensor according to one embodiment of the invention,

[0026] [Fig.2] schematic sectional view of a radar sensor according to another embodiment of the invention,

[0027] [Fig.3] representation of a step of a method for producing a waveguide structure,

[0028] [Fig.4] representation of another step in the process of producing a waveguide structure,

[0029] [Fig.5] representation of another step in the process of producing a waveguide structure,

[0030] [Fig.6] representation of another step in the process of producing a waveguide structure,

[0031] [Fig.7] representation of another step in the process of producing a waveguide structure,

[0032] [Fig.8] representation of the final state of a waveguide structure,

[0033] [Fig.9] illustration of the method of producing a waveguide structure according to another exemplary embodiment of the invention,

[0034] [Fig. 10] illustration of the method of producing a waveguide structure according to another exemplary embodiment of the invention,

[0035] [Fig. 11] partial section of a waveguide structure according to another embodiment.

[0036] DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0037] [Fig.l] shows an example of a waveguide structure 10 for n radar sensors. This embodiment corresponds to a waveguide structure 10 in the form of a waveguide antenna with two coupling windows 10 located on the non-visible back of the structure and which are fed by microwave radiation from a high-frequency chip not shown in parallel end segments of two waveguides 14, 16. The end segments of the two waveguides are mechanically connected by a spacer 18; each of the two waveguides 14, 16 is divided into four branches 20 or 22 which go to another straight antenna cord 24 or 26. Each of the antenna cords 24, 26 is formed by a waveguide of rectangular section, the upper wall of which comprises a series of radiation windows (emission window 28).The antenna cords 14 and 26 are parallel to each other in a common plane and are nested so that each antenna cord 24 of the waveguide 14 has as a neighbor an antenna cord 26 of the waveguide 16. While the end segments of the two waveguides in which the injection windows 12 and the antenna cords 24, 26 are located respectively lie in a common plane, the branches 20, 22 must be vertically offset relative to each other so that the waveguides can cross. For this reason, the . waveguide 16 has an S-shaped curved segment 30 between the injection window 12 and the branch point 22.

[0038] In the transition zone between the branches 20, 22 and the antenna cords 24, 26 the waveguides are twisted around the longitudinal axis of the respective antenna cord so that the planes in which the radiation windows 28 are located are tilted to the opposite sides relative to the plane of the branches 20, 22. The antenna cords 24 thus radiate microwave power mainly in a direction which, in [Fig.l], is rather turned towards the observer while the antenna cords 26 radiate the microwave power in a direction which is rather oriented in the opposite direction to the observer.The radar sensor may, for example, be installed in a motor vehicle so that the antenna leads 24, 26 are vertical and the radiation windows 28 are oriented primarily forward; however, the antenna leads 24 emit the power more towards the left side of the vehicle and the antenna leads 26 emit more towards the right side. Optionally, the two waveguides 14, 16 may be supplied with different power so that the radar sensor will have a different range on the right side and on the left side of the vehicle. If necessary, the range profile may also vary depending on the situation.

[0039] For reasons of stability, the antenna cords 24, 26 are connected to each other at their free end by spacers 32. The entire waveguide structure 10 is a 3D printing product which is produced in one piece by a 3D metal printing process. Only the free ends of the antenna cords 24, 26 and the ends of the end segments in which the injection window 12 is located are still open in their state shown in [Fig.l] and they will subsequently be closed, by closing plates, during assembly of the antenna structure.

[0040] According to the same principle, by the 3D printing process it is also possible to produce waveguide structures in which the emission windows have three different radiation directions, for example, in the longitudinal direction of the vehicle towards the front, towards the right front or towards the left front. The power can thus be controlled so that the radar sensor has a greater range in the forward direction than in the two lateral directions so as to obtain a sort of "sliding vision radar".

[0041] [Fig.2] shows a complete radar according to another embodiment according to a schematic section. The radar sensor 34 has a housing 36 which is closed on its top according to [Fig.2] by a radom 38. Inside the housing 36, there is a plate 42 held by uprights 40 fitted on their lower face with a high-frequency chip 44 (for example, an MMIC) and other electronic components 46. The outer side of the housing 36 forms a connector unit 48 by which the radar sensor can be connected to the electronics of a driver assistance system. The electrical lines 50 connect the connector unit 48 to the conductive paths of the board 42 which go to the electrical contacts (Bail Grid Arrays) of the high-frequency chip 44 and the components 46. The high-frequency chip 44 and the components 46 are installed on a cooling sheet 52 so as to dissipate the heat released during operation.

[0042] The top of the board 42 has a waveguide structure 54 in the form of a waveguide antenna that was fabricated by 3D printing like the waveguide structure. The high-frequency chip 44 has two integrated decoupling points through which microwave power is injected through the passages 56 of the board 42 into the waveguide structure 54.

[0043] Since the waveguide antenna is a monostatic transmitting and receiving antenna, there can also be signal flow in the reverse direction from the antenna to the high frequency chip 44.

[0044] The waveguide structure 54 shown only by its outline in [Fig. 2] has a relatively complex pattern of waveguide antennas which, as in [Fig. 1], are waveguides which cross each other with passages 56. At the point where the waveguides cross each other, must lie in several planes, the waveguide structure 54 has a raised plate 58. In the example shown, the waveguide structure 54 extends beyond the plate 42 and has, outside the contour of the plate, protrusions 60 coming into the space under the plate 42. This makes it possible to use, in an efficient manner, the volume available in the housing 36 for complex driving patterns of the waveguide structure. The radiation emission ports of the waveguide antennas are located in areas 62 in which the waveguide structure 54 has a lower height.This is why it ensures that the radiation holes are at a sufficient distance from the radom 38. .

[0045] In the example of [Fig. 2], the bottom wall of the waveguide structure 54 which is made of metal can be welded directly to the plate 42 or be glued. According to another embodiment, in which the waveguide structure does not extend beyond the edge of the plate, the plate could also be a printing support for printing the waveguide structure.

[0046] A method of printing a waveguide structure will be described hereinafter in more detail using FIGS. 3 to 8, for example, the waveguide structure 10 of [Fig. 1].

[0047] [Fig. 3] shows a section of a part of the waveguide structure, more particularly a section of one of the antenna cords 24 at the height of the spacer 32 in a state during the printing process. Using a through-print head 64, the spacers 32 as well as the bottom 70 and the side walls 68 of the waveguide have already been printed on a support. On top, the waveguide is still open. The two side walls 68 have a slightly different height and are thus inclined correspondingly slightly in the emission direction of the antenna cord relative to the vertical. It is also possible, in a 3D printing process and without using a printing substrate, not to produce horizontal walls, but it is also possible to produce walls slightly inclined relative to the vertical direction.Since the metal, which is still liquid upon arrival at the printing object, solidifies immediately due to the droplets ejected by the print head 64, the material in each droplet position can be passed substantially over the material in the next layer in depth so that a side wall with an inclined side is obtained.

[0048] When the stage shown in [Fig. 3] is reached, the printing process is interrupted and the waveguide cavity is filled with a filler material 72 as shown in [Fig. 4]. The filler material 72 is, for example, fine-grained, fluid sand.

[0049] The excess filler material is scraped off with a scraper so that a flat print support surface is obtained for printing the waveguide cover as shown in [Fig. 5]. Then, the printing process is resumed and a substantially horizontal top wall 74 is printed. [Fig. 6] shows the state at the end of the printing operation. In this state, the waveguide structure can be detached from the substrate 70.

[0050] [Fig. 7] shows an end segment of the antenna cord 24 in longitudinal section. Since the antenna cord has an open end, the filler material 72 can simply be poured.

[0051] [Fig.8] shows the final state of the antenna cord 24 after closing the open end of the waveguide with a welded closing plate 76.

[0052] An alternative form for producing the waveguide structure 10 using the 3D printing method is shown in [Fig. 9]. The state shown corresponds to that of [Fig. 5]. In this alternative form of the method, however, in addition to the print head 64 for metal, another print head 78 is provided, with which the filling material 80 is printed, which fills the cavity of the waveguide. The filling material 80 can be, for example, a wax or other easily meltable material that liquefies and is poured out after the printing process has ended. Alternatively, a soluble material can also be used, which can be removed with a solvent.

[0053] In the example presented, the filling material 80 is not a solid block, but a honeycomb structure with diamond-shaped cavities 82. These cavities make it possible not only to save material, but also to accelerate the process of removing the filling material.

[0054] [Fig. 10] shows another variant of the manufacturing method. In this method, five print heads are used, namely two print heads 64 for metal, two print heads 84 for a cooling agent and one print head 86 installed in the middle for a filling material 88. The print heads are provided, symmetrically, on a carriage passing through the side walls 68 when printing; each time the carriage passes, a part of these side walls is printed with the print head 64. With the next print head, a liquid cooling agent is injected into the space between the two side walls; with the print head 86, the droplets of the filling material 88 are expelled into the cooling agent. The cooling agent causes the droplets to solidify immediately.If, during the next passage of the carriage, further droplets of the filler material 88 are printed, they can no longer bind to the previously printed droplets, so that the droplets remain isolated from one another and together they form, with the cooling agent, a slurry which is difficult to flow. When the side walls 68 have reached their full height, the printer starts with the upper wall 74, while in this area in which the upper wall is higher, printing with cooling agent and filler is carried out. At the end of the printing process, the mixture of filler material and filler can be easily rinsed off.

[0055] [Fig. 11] is a partial section of a radar sensor 90 according to another embodiment. This radar sensor has a plate 92, the top of which is lined with high-frequency chips 94. A waveguide structure 96 for forming a waveguide antenna is provided above the high-frequency chip 94 and comprises two parallel antenna cords 98, which are shown in section in [Fig. 11]. Analogously to [Fig.l], the antenna cords 98 are shown slightly tilted relative to each other, so that the top walls comprise emission windows 100 slightly inclined relative to each other and thus the microwave power is emitted in different directions. The lower side of each antenna cord 98 has an injection structure 102 by which the microwave signal generated by the high frequency chip 94 is injected into the waveguide.The waveguide structure 96 is also produced in one piece by 3D printing. At the same time, the dowel-type fixing members 104 were printed, with which the waveguide structure 96 is simply fixed to the plate 92. At the same time, a grid of parallel pins was also printed. 106 with which the waveguide structure is supported on the pins 106 which, like the entire waveguide structure, are made of metal and at the same time serve as cooling fins for heating the high-frequency chip 94 which is, for example, thermally coupled with a thermally conductive paste to the end decoupling structures 102.

Claims

Claims

1. Radar sensor having a waveguide structure (10; 54; 96) for guiding microwave signals, sensor with the waveguide structure (10; 54; 96) is a 3D printing product, characterized in that the waveguide structure (10) comprises intersecting waveguides (14, 16) having segments (24, 26) located in a common plane and comprises a waveguide antenna having several groups of emission radiation windows (28) which are located in planes inclined to each other.

2. Radar sensor according to claim 1, characterized in that at least parts of the printed waveguide structure (10; 54; 96) are made of metal.

3. Radar sensor according to one of the preceding claims, characterized in that the waveguide structure (54) is connected to a plate (42) by welding, gluing, sintering, clamping or screwing.

4. Radar sensor according to one of claims 1 to 3, characterized in that the plate (42) forms a printing support on which the waveguide structure (54) is printed.

5. Radar sensor according to one of claims 1 to 2, in which the waveguide structure (87) comprises printed fixing members (104) which connect it to another radar sensor component (92).

6. Radar sensor according to one of the preceding claims, characterized in that the waveguide structure (96) comprises printed heating structures (106) for heating electronic components (94) of the radar sensor.

7. Radar sensor according to one of claims 5 or 6, characterized in that the fixing members (104) and / or the heating structures (106) have the form of pins perpendicular to a plate-shaped component (92) of the radar sensor and which have a flexibility compensating for the different thermal expansion coefficients of the waveguide structure (96) and the plate-shaped component (92).

8. Radar sensor according to one of the preceding claims, characterized in that the waveguide structure (96) is a waveguide antenna having radiation windows (100) made of a material permeable to microwave radiation and which are printed in one go with electrically conductive parts of the waveguide structure (96) by a multi-component printing method.

9. Method for producing a radar sensor having a waveguide structure (10; 54; 96), characterized in that the waveguide structure is produced by a 3D printing method.

10. Method according to claim 9, characterized in that the 3D printing method is an inkjet printing method.

11. Method according to claim 10, characterized in that before the end of the printing process the cavities of the waveguide structure are filled with a filling material (72; 80; 88) which forms the closure of the waveguide structure terminating a printing substrate for printing the parts closing the cavities and which is fluid at least under certain conditions.

12. Method according to claim 9, characterized in that the 3D printing method is a stereolithographic printing method.

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