RADARSENSOR

Description

Field of invention

[0001] The invention relates to a radar sensor. State of the art

[0002] Radar sensors are used to detect distant objects. They emit electromagnetic radar waves in a predetermined direction and then receive and analyze the reflected portions of these waves. For example, radar sensors can be used in motor vehicles to detect obstacles or other road users.

[0003] DE 10 2012 202 913 A1 describes a radar sensor. The US 2016 013 557 A1 describes an antenna device. EP 1 462 817 A1 describes a millimeter-wave radar and a method for its manufacture. EP 0 884 799 A2 describes a semiconductor module containing an antenna element. Disclosure of the invention

[0004] Against this background, the approach presented here introduces a radar sensor according to the independent claim. Advantageous further developments and improvements of the approach presented here result from the description and are described in the dependent claims. Advantages of the invention

[0005] Embodiments of the present invention can advantageously enable the controlled coupling and absorption of substrate waves generated from an antenna substrate during the operation of a radar sensor. This can improve the functionality of the radar sensor and, in particular, its radiation pattern.

[0006] A radar sensor with at least one antenna structure and at least one coupling structure is proposed, wherein the coupling structure is configured to couple substrate waves from an antenna substrate used as a support for the antenna structure and the coupling structure and to radiate them as coupling waves into a radiation area, wherein the radar sensor further comprises an absorber arranged in the radiation area for absorbing the coupling waves.

[0007] Ideas for embodiments of the present invention can be considered to be based, among other things, on the thoughts and findings described below.

[0008] An antenna substrate can be described as a printed circuit board (PCB). The antenna substrate is electrically non-conductive. Electrically conductive structures, such as conductor tracks, vias, and metallized areas, can be arranged on or integrated into the antenna substrate. A portion of the electrically conductive structures can form an antenna structure. Another portion can form a coupling structure. The antenna structure is connected to control electronics. The antenna structure can radiate electromagnetic waves when it is stimulated by a high-frequency electrical signal from the control electronics. The antenna structure can thus act as a transmitting antenna. The antenna structure can have a directional characteristic and radiate a large portion of the electrical energy supplied to it by the high-frequency signal within a defined angular range.Furthermore, the antenna structure can map an incoming electromagnetic signal into a high-frequency signal and thus act as a receiving antenna.

[0009] In particular, electrically conductive areas on the surface of the antenna substrate can form the antenna structure. An electrically conductive material can be applied to the surface to create this structure. This material can be printed onto the surface using various printing methods such as screen printing, roll printing, etc. Alternatively, the conductive material can be deposited onto the surface in other ways. Various deposition methods, such as gas-phase deposition (e.g., CVD or PVD) or liquid-phase deposition (e.g., electroplating or electroless plating), can be used. Before deposition, areas where no conductive material is to be deposited can be masked. The mask can be removed after deposition.Alternatively, electrically conductive material can be deposited across the entire surface, and then, after applying a mask, unwanted areas can be removed by etching. Masking and deposition allow the antenna structure to be aligned on the surface with high precision. The individual sections can be electrically connected to each other. These sections can form antenna structures of varying sizes and strengths.

[0010] Due to high-frequency effects, some of the electrical energy supplied by the control electronics can be coupled into the antenna substrate as substrate waves from the antenna structure and propagate within the antenna substrate. At edges of the antenna substrate, such as the borders, the substrate waves can couple out uncontrollably, radiate in an uncontrolled direction, and thus cause interference.

[0011] The coupling structure can act as a capture device or trap for the substrate waves, selectively coupling them out of the antenna substrate. In this case, the coupling structure itself acts as an antenna and can, in turn, radiate electromagnetic waves, referred to here as coupling waves. The coupling structure can emit these electromagnetic waves, particularly into a specific radiation pattern. For this purpose, the coupling structure can exhibit its own directional characteristics. The directional characteristics of the coupling structure can differ significantly from those of the antenna structure. The directional characteristics of the coupling structure can be directed towards the absorber.

[0012] An absorber converts absorbed electromagnetic waves into heat. The absorber can consist, for example, of a plastic material with a high proportion of electrically conductive particles and / or carbon fibers, such as graphite. It can also be made of a metallic or metallized foam.

[0013] The antenna structure can be aligned along a main direction of extension to exhibit directional characteristics. A main radiation pattern can be arranged alongside the antenna structure along the main direction of extension. The coupling structure can be arranged alongside the antenna structure. In other words, the coupling structure can be positioned laterally offset from the antenna structure.

[0014] The coupling structure can be electrically isolated from the antenna structure. The coupling structure can be isolated from the antenna structure by the antenna substrate. No electrical current can flow between the antenna structure and the coupling structure. The coupling structure can be a passive element of the radar sensor.

[0015] Electrically conductive areas on the surface of the antenna substrate can form the coupling structure. During the production of the antenna structure, the electrically conductive material for the coupling structure can be applied to the surface in the same step. The electrically conductive material for both the antenna structure and the coupling structure can be printed onto the surface in a single operation. Alternatively, the electrically conductive material can be deposited onto the surface in a single operation. Before deposition, areas where electrically conductive material is not to be deposited for either the antenna or the coupling structure can be masked. The mask can be removed after deposition. By masking and deposition, the coupling structure can be aligned with high precision relative to the antenna structure.By arranging the coupling structure on the surface, substrate waves propagating along the surface can be coupled out particularly well.

[0016] The sub-areas can be electrically isolated from one another. The coupling structure can have unconnected individual areas. By using separate individual areas, mutual interference between the individual sub-areas of the coupling structure can be reduced.

[0017] The sub-areas can form antenna structures oriented in different directions. These differently oriented antenna structures are aligned at different angles to the main direction of extension of the antenna structure. Due to these different angles, the coupling structure exhibits a weaker directional characteristic than the antenna structure. Because of these different angles, the coupling structure can couple substrate waves from the antenna substrate from different directions.

[0018] Antenna structures with the same orientation can be grouped together. Antenna structures with the same orientation can be arranged at regular intervals. By strategically aligning the antenna structures, expected frequencies of the substrate waves can be coupled out particularly effectively from the antenna substrate.

[0019] The absorber can be positioned on a surface of the radar sensor's radome opposite the coupling structure. A radome can be a protective housing for the radar sensor. The radome can be transparent to electromagnetic waves. The absorber can be spatially separated from the antenna substrate. This spatial separation ensures that the absorber is electrically isolated from the antenna structure. Any electrical currents that may arise within the absorber are thus reliably separated from the antenna structure. Any heat generated can be dissipated via the radome.

[0020] The absorber can also be designed to shield the radar sensor's control electronics. The absorber can be positioned within the coupling structure's radiation pattern and in front of the control electronics. In this way, a single component can fulfill both functions. Brief description of the drawings

[0021] Embodiments of the invention are described below with reference to the accompanying drawings, whereby neither the drawings nor the description are to be interpreted as limiting the invention. Fig. 1 shows a representation of a radar sensor according to an exemplary embodiment; and Fig. 2 shows a cross-sectional view through a radar sensor according to an exemplary embodiment.

[0022] The figures are merely schematic and not to scale. Identical reference symbols in the figures denote identical or equivalent features.

[0023] In radar sensors with antennas on a high-frequency (HF) substrate, unwanted power components can occur, depending on the implementation. These propagate through the printed circuit board substrate, forming so-called substrate waves. High-impedance structures (HAS) can be used to suppress these HAS. When using HAS, a through-hole connection to the ground plane is necessary. The large number of HAS required can lead to additional production costs and manufacturing risks.

[0024] Therefore, the approach presented here uses structures that radiate the power of the substrate waves into an absorber and do not require any additional production steps. Embodiments of the invention

[0025] Fig. 1Figure 1 shows a representation of a radar sensor 100 according to an exemplary embodiment. The radar sensor 100 has an antenna substrate 102, which serves as a support for at least one antenna structure 104 of the radar sensor 100 and at least one coupling structure 106 of the radar sensor 100. The antenna structure 104 can be referred to as an antenna array. The antenna structure 104 has several individual antenna structures 108 arranged side by side in a row. The row is aligned along a principal direction of the antenna structure 104. Here, the antenna structure 104 is shown with six individual antenna structures 108. The number of individual antenna structures 108 can be adapted as required. The antenna structures 108 are interconnected and connected to the control electronics of the radar sensor 100 via an electrically conductive conductor track 110 of the antenna substrate 102. The conductor track 110 is also aligned with the main direction.The antenna structures 108 are metallized surfaces on a surface of the antenna substrate 102. The central antenna structures 108 of the antenna structure 104 are larger than the outermost antenna structures 108.

[0026] The coupling structure 106 is arranged on both sides of the antenna structure 104. Here, the coupling structure 106 consists of a multitude of metallized surfaces on the surface of the antenna substrate 102. The individual surfaces of the coupling structure 106 are not electrically connected to each other or to the antenna structure 104. The metallized surfaces of the coupling structure 106 also form antenna structures 108. The antenna structures 108 of the coupling structure 106 are oriented differently. Nine antenna structures 108 with the same orientation are grouped into a 3x3 matrix 112. The antenna structures of adjacent matrices are oriented differently. Here, the antenna structures 108 are oriented in two directions. One half of the antenna structures 108 is oriented along the main direction. The other half is oriented perpendicular to the main direction.

[0027] When an electrical excitation signal is applied to the antenna structures 108 of the antenna structure 104 via the conductor track 110, the antenna structure 104 radiates a portion of the supplied power as electromagnetic radar waves in a design-related radiation direction. Another portion of the power is coupled into the antenna substrate 102 as substrate waves 114.

[0028] The antenna structures 108 of the coupling structure 106 couple the substrate waves 114 out of the antenna substrate 102 and in turn radiate coupling waves into a radiation area of ​​the coupling structure 106.

[0029] In the radiation area, at least one absorber (not shown here) is arranged, which absorbs the coupling waves and converts them into heat.

[0030] The antenna structures 104 can, for example, be operated at a frequency of 76 GHz. This results in parasitic high-frequency effects. One such high-frequency effect is substrate waves 114, which propagate to other electrical conductors or edges of the antenna substrate 102 and are radiated from there.

[0031] The edges of the antenna substrate 102 are subject to manufacturing tolerances, which makes the direction of radiation at the edges undefined. This undefined radiation can alter the antenna pattern of the radar sensor.

[0032] Fig. 2 Figure 1 shows a cross-sectional view through a radar sensor 100 according to an exemplary embodiment. The radar sensor 100 essentially corresponds to the radar sensor in Figure 1. Fig. 1In addition, the coupling waves 200, the absorber 202, and a radome 204 of the radar sensor 100 are shown here. The antenna structures 108 of the coupling structure 106 couple the substrate waves 114 out of the antenna substrate 102 and radiate the coupling waves 200 into the radiation area 206. The absorber 202 is located in the radiation area 206. Here, the absorber 202 is positioned on the radome 204. The absorber is separated from the coupling structure 106 by a gap and is thus electrically isolated from the antenna structures 108 of the coupling structure 106.

[0033] The radome 204 is transparent to the radar waves 208 emitted by the antenna structure 104 and protects the electrical components of the radar sensor 100 from environmental influences.

[0034] In other words, additional structures are applied to the antenna substrate 102, also referred to as a sensor circuit board, next to or around the antennas. These structures direct or radiate the incoming substrate waves 114 towards an overlying absorber 202, thus attenuating them. This minimizes the impact on the antenna characteristics. No further manufacturing steps are required in the production process to create these structures. The approach presented here is therefore cost-neutral. Furthermore, the substrate waves 114 are radiated from the substrate instead of being reflected by high-impedance structures.

[0035] A radar sensor 100 according to the approach presented here comprises a printed circuit board with a transmitting and receiving antenna in a housing with a radar-transparent radome 204 above the antennas and an absorber 202 within the housing. In addition to the antenna structures 104, further metallic structures are arranged which transfer the power traveling from the antennas in the substrate towards the absorber 202. Patch antennas are preferably used as these structures, as they can be easily manufactured during the printed circuit board production process. The patch antennas can be arranged as rectangular structures next to the antennas. The structures can be arranged below or just beside the absorber 202 in order to absorb the radiated substrate waves 114 in the absorber 202 so that they do not alter the antenna characteristics.

[0036] The coupling structure 106 and the antenna structure 104 can be metallically etched and / or deposited. The individual surfaces of the coupling structure 106 can, for example, have a length of four millimeters and a width of two millimeters. The length depends on the wavelength of the emitted radar waves 208. The length of the individual surface can be in a harmonic ratio to the wavelength. For example, the length can be ¼ λ or an integer multiple of the wavelength. The suitable length also depends on the dimensions and / or high-frequency properties of the antenna substrate 102.

[0037] Finally, it should be noted that terms such as "comprising," "encompassing," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Reference numerals in the claims are not to be considered as limitations.

Claims

1. Radar sensor (100) having at least one antenna structure (104) and at least one coupling structure (106) designed to couple substrate waves (114) out of an antenna substrate (102) used as a carrier for the antenna structure (104) and the coupling structure (106) and to emit them as coupling waves (200) into an emission region (206), characterized in that the radar sensor (100) furthermore comprises an absorber (202) arranged in the emission region (206) and serving for absorbing the coupling waves (200).

2. Radar sensor (100) according to Claim 1, wherein the coupling structure (106) is arranged next to the antenna structure (104).

3. Radar sensor (100) according to either of the preceding claims, wherein the coupling structure (106) is electrically isolated from the antenna structure (104).

4. Radar sensor (100) according to any of the preceding claims, wherein electrically conductive partial regions of a surface of the antenna substrate (102) form the coupling structure (106).

5. Radar sensor (100) according to Claim 4, wherein the partial regions are electrically isolated from one another.

6. Radar sensor (100) according to either of Claims 4 and 5, wherein the partial regions form antenna structures (108) oriented in different directions.

7. Radar sensor (100) according to Claim 6, wherein identically oriented antenna structures (108) are arranged in a grouped fashion.

8. Radar sensor (100) according to any of the preceding claims, wherein the absorber (202) is arranged on a surface of a radome (204) of the radar sensor (100) situated opposite the coupling structure (106).

9. Radar sensor (100) according to any of the preceding claims, wherein the absorber (202) is furthermore designed to shield control electronics of the radar sensor (100).