Hollow waveguide element and method of manufacturing the same

Abstract

The invention relates to a hollow waveguide element having a channel (10) which has an open side which is delimited by at least one side wall (11, 12). The side wall (11, 12) has a plurality of electric contact surfaces (20) which are spaced apart from one another.

Description

Technical Field

[0001] This invention relates to a hollow waveguide element, particularly a hollow waveguide element for use in radar sensors. Furthermore, this invention also relates to a method for manufacturing the hollow waveguide element. Background Technology

[0002] Radar sensors are placed in vehicles to enable comfort and safety features. They measure the distance to targets directly, without relying on image analysis like optical cameras.

[0003] Antenna structures for radar sensors can be constructed on circuit boards as planar antennas, particularly microstrip antennas. Three-dimensional hollow waveguide antennas are also used. Compared to planar antennas, they offer lower power loss and higher bandwidth characteristics. Hollow waveguide antennas typically consist of multiple layers that must be bonded or soldered together.

[0004] DE 10 2020 216 362 A1 describes a radar sensor having a hollow waveguide structure in the form of a channel with an opening on one side. The channel is soldered to a copper layer on a circuit board with its open side facing out, such that the copper layer forms a wall of the waveguide. Summary of the Invention

[0005] This hollow waveguide element is specifically configured for guiding electromagnetic waves having a wavelength λ. It has a channel with an open side, which is defined by at least one sidewall. For example, the channel may have a single sidewall completely surrounding it, or it may have multiple sidewalls. In addition to the sidewall defining the open side, the channel may particularly have at least one wall opposite the open side, connected to the sidewall. The at least one sidewall has a plurality of electrically contact surfaces spaced apart from each other. An electrically contact surface is understood here as a surface configured and equipped for welding or electrically bonding the sidewall of the channel to a metal surface. This metal surface is particularly the metal bottom surface of a circuit board. Thus, the open side can be closed by this metal surface. In one embodiment of the hollow waveguide element, the channel may also be made of metal. In another embodiment of the hollow waveguide element, the channel is made of a carrier material, such as plastic, which has a metallized layer on the inner side of the channel.

[0006] In principle, the sidewalls of such a channel can be fully welded or bonded to the metal surface. However, this full connection results in a rigid connection between the hollow waveguide element and the metal surface, which introduces a high risk of bending and breakage during the lifespan of the hollow waveguide element. It has been found that this risk can be mitigated by using multiple electrically spaced contact surfaces.

[0007] The length and / or width of each electrical contact surface is preferably in the range of 0.3 mm to 1.5 mm. The area of ​​each electrical contact surface is preferably 0.09 mm². 2 Up to 2.25 mm 2 Within a certain range. Such an electrical contact surface has the following advantages: on the one hand, it ensures a load-bearing connection between the channel and the metal surface; on the other hand, it keeps the contact area between the channel and the metal surface so small that the hollow waveguide element has high tolerance to mechanical loads.

[0008] The distance between two adjacent electrical contact surfaces is preferably in the range of 0.3 mm to λ / 4, and particularly preferably less than λ / 8. The height of the opening between the contact surfaces is also preferably in the range of 0.3 mm to λ / 4, and particularly preferably less than λ / 8, to minimize the impact on wave propagation. Thus, the electrical contact surfaces are sufficiently close to each other to reliably connect the hollow waveguide element to the metal surface, while being sufficiently far apart to significantly reduce the sensitivity of the hollow waveguide element to mechanical loads.

[0009] The separation of the contact surfaces is preferably achieved by means of through-holes penetrating the sidewalls, particularly arcuate or rectangular ones. Such through-holes allow the unpenetrated areas of the sidewalls, each terminating in an electrical contact surface, to take the form of pins, which are well-suited for defined point connections between the channel and the metal surface. Furthermore, it has been found that such through-holes do not negatively impact the waveguide characteristics of the channel. These through-holes can also be implemented, in particular, as teeth on the sidewalls.

[0010] The channel preferably has a rectangular cross-section, which allows for simple manufacturing. The height of the channel from the opening side to the channel side opposite the opening side is preferably in the range of λ / 2 to λ, as this corresponds to a single-mode rectangular waveguide.

[0011] The channel is preferably arranged on the metal base surface of the circuit board, the outer contour of which corresponds to the outer contour of the opening side of the channel. This metal base surface, especially if made of copper, can also be referred to as a pad. If the electrical contact surfaces are separated by through-holes penetrating the sidewalls, the outer contour of the metal base surface has a toothed structure, which facilitates precise positioning of the channel on the circuit board. Here, the electrical contact surfaces of the channel are soldered or bonded to the teeth protruding from the outer contour of the metal base surface.

[0012] The wall opposite to the opening of the channel extends beyond the channel's cross-section and can function as an antenna structure for radar sensors. One or more openings extend through this wall into the channel's interior and can serve as radiating elements for radar waves.

[0013] The circuit board also preferably has a circuit with a Monolithic Microwave Integrated Circuit (MMIC) for radar sensors, which is connected to the channel in a waveguide manner. This circuit can be positioned on the same side of the circuit board as the channel to protect it from heat and parasitic radiation below the channel side, which extends into an antenna structure, or it can be positioned on the side of the circuit board away from the channel, where the waveguide connection extends through the circuit board.

[0014] In a method for manufacturing such a hollow waveguide element with a circuit board, a hollow waveguide element is first provided, which has a channel open on only one side. Furthermore, a circuit board with a metal base is provided, the outer contour of which corresponds to the outer contour of the open side of the channel of the hollow waveguide element. The channel is then fixed to the metal base of the circuit board at electrical contact points by soldering or conductive bonding, thereby obtaining a hollow waveguide element that is bounded on one side by the metal surface of the circuit board and on the other sides by the channel walls. Here, precise alignment of the channel on the metal base is achieved through the surface stress effect of solder paste or adhesive. Attached Figure Description

[0015] Embodiments of the invention are shown in the accompanying drawings and described in detail in the following description.

[0016] Figure 1 An isometric view of a hollow waveguide element according to an embodiment of the present invention is shown.

[0017] Figure 2 An isometric view of a hollow waveguide element according to another embodiment of the present invention is shown.

[0018] Figure 3a An isometric view of a hollow waveguide element channel according to another embodiment of the present invention is shown.

[0019] Figure 3b Showing according to Figure 3a A top view of the passageway.

[0020] Figure 4 A top view of a circuit board that can be connected to a channel of a hollow waveguide element in one embodiment of the present invention is shown.

[0021] Figure 5 Showing according to Figure 3a and Figure 3b The isometric view of the channel shows that its opening side is largely closed by the metal bottom surface of the circuit board.

[0022] Figure 6a An isometric view of a hollow waveguide element according to an embodiment of the present invention is shown, which has according to Figure 3a and Figure 3b The channel and according to Figure 4 The circuit board.

[0023] Figure 6b Showing according to Figure 6a A cross-sectional side view of a hollow waveguide element.

[0024] Figure 7 A flowchart illustrating a method for manufacturing a hollow waveguide element according to an embodiment of the present invention is shown. Detailed Implementation

[0025] The hollow waveguide element according to the first embodiment of the present invention is in Figure 1 As shown in the diagram, the hollow waveguide element has a channel 10 with a rectangular cross-section. The channel 10 has two sidewalls 11 and 12, each with an electrical contact surface 20 on its underside. The sidewalls 11 and 12 have semi-arched through-holes 21, which separate the electrical contact surfaces 20 from each other. The channel 10 is arranged on a circuit board 30 such that the electrical contact surfaces 20 are soldered to a copper-based metal bottom surface 31 of the circuit board 30. The metal bottom surface 31 forms the lower side surface of the channel 10. The remaining three sides of the channel are formed by metallization on the inner walls of the channel 10.

[0026] Figure 2 A second embodiment of the hollow waveguide element according to the present invention is shown. It differs from the first embodiment in the size design of the channel 10. In the first embodiment, the width of the channel 10 is greater than its height, while in the second embodiment, the height of the channel 10 is greater than its width. In both embodiments, the outer contour of the metal bottom surface precisely corresponds to the outer contour of the opening side of the channel 10, which is defined by two sidewalls 11, 12.

[0027] The channel 10 of the hollow waveguide element according to the third embodiment of the present invention is in Figure 3a and Figure 3b As shown. The channel 10 is implemented in a T-shape and is defined by a single surrounding sidewall 13. This sidewall 13, like the sidewalls 11 and 12 in the previous two embodiments, has a semi-arched through-hole 21 and is therefore toothed. The remaining areas of the sidewall 13 between the through-holes 21 terminate in the electrical contact surfaces 20. The channel 10 is constructed such that the wall of the antenna surface 14 is opposite to its opening side and extends beyond the cross-section of the channel 10. Four radiating openings 15 penetrate the antenna surface 14, thereby connecting the channel 10 to the side of the antenna surface 14 opposite to the channel 10 in a waveguide manner.

[0028] According to the third embodiment of the present invention, channel 10 is configured for communication with... Figure 4The circuit board 30 shown is soldered. This circuit board has a metal bottom surface 31 made of copper, which has an outer profile corresponding to the toothed profile of the sidewall 13 of the channel 10. A via 32 for conducting waves extends from the metal bottom surface 31 through the circuit board 30 to the opposite side of the circuit board. The inner wall of the via 32 is metallized.

[0029] If channel 10 is welded to the metal base 31, then the result is... Figure 5 The structure shown is without the rest of the circuit board 30. The complete hollow waveguide element obtained in this way... Figure 6a and Figure 6b As shown in the diagram. On the side of circuit board 30 opposite to channel 10, the MMIC is connected via a ball grid array (BGA) 41. This MMIC is configured to act as a transceiver for the radar sensor. Radar waves from the MMIC 40 are guided through via 32 and channel 10 to the radiating element 15 and radiated by the radar sensor. This type of radar sensor is particularly suitable for use in motor vehicles.

[0030] The process of manufacturing a radar sensor according to a third embodiment of the present invention is as follows: Figure 7 The diagram is schematically shown. After the initial 50 steps of this method, an unfinished hollow waveguide element is first provided, which is constructed solely from... Figure 3a and Figure 3b The channel 10 shown is composed of [the following]. Subsequently, 52 [other components] are provided according to [the following criteria]. Figure 4 The electrical contact surface 20 of the sidewall 13 of the channel 10 is coated with solder paste and precisely positioned on the metal bottom surface 31 of the circuit board 30, and then fixed thereon by soldering 53. Here, the surface stress of the solder paste ensures the correct positioning of the channel 10. The method then ends 54. The arrangement of other electronic components, such as the arrangement of the MMIC 40 on the circuit board 30, can be performed before or after performing these method steps 50 to 54.

Claims

1. A hollow waveguide element having a channel (10) having an open side, said open side being bounded by at least one sidewall (11-13), characterized in that, The sidewalls (11-13) have multiple electrically contact surfaces (20) that are spaced apart from each other.

2. The hollow waveguide element according to claim 1, characterized in that, The height and / or width of each contact surface (20) is in the range of 0.3 mm to 1.5 mm.

3. The hollow waveguide element according to claim 1 or 2, characterized in that, The distance between two adjacent contact surfaces (20) is in the range of 0.3 mm to λ / 4 mm, where λ is the wavelength of the electromagnetic wave to be conducted by the hollow waveguide element.

4. The hollow waveguide element according to any one of claims 1 to 3, characterized in that, The separation of the contact surfaces (20) is achieved by means of a through portion (21) passing through the sidewalls (11-13).

5. The hollow waveguide element according to claim 4, characterized in that, The through section (21) is arc-shaped or rectangular.

6. The hollow waveguide element according to claim 4 or 5, characterized in that, The through portion (21) is implemented as the teeth of the sidewall (11-13).

7. The hollow waveguide element according to any one of claims 1 to 6, characterized in that, The channel (10) has a rectangular cross-section.

8. The hollow waveguide element according to any one of claims 1 to 7, characterized in that, The channel (10) is arranged on the metal bottom surface (31) of the circuit board (30), the outer contour of which corresponds to the outer contour of the opening side of the channel (10).

9. The hollow waveguide element according to claim 8, characterized in that, The circuit board (30) has an MMIC (40) for a radar sensor, which is connected to the channel (10) in a waveguide manner.

10. A method for manufacturing a hollow waveguide element according to claim 8 or 9, comprising the following steps: - Provide (51) a hollow waveguide element according to any one of claims 1 to 7, - Provides (52) a circuit board (30) having a metal bottom surface (31), the outer contour of which corresponds to the outer contour of the opening side of the channel (10) of the hollow waveguide element, and - The channel (10) is fixed (53) to the metal bottom surface (31) at the contact surface (20) by means of welding or conductive bonding.

Images