Radarsensor

Abstract

Radar sensor (100) comprising: - a radar antenna (130); - a radar lens (115); - a funnel element (140) between the radar antenna (130) and the radar lens (115); - wherein the funnel element (140) comprises a material that absorbs radar radiation emitted by the radar antenna (130); - wherein the radar antenna (130) together with other high-frequency components (135) is arranged on a flat circuit carrier (125) or a circuit board (125); - wherein the high-frequency circuit (135) on the flat circuit carrier (125) or the circuit board (125) maintains a predetermined radial distance to the radar antenna (130); and wherein the funnel element (140) is placed on the flat circuit carrier (125) or the circuit board (125) in the region of the radar antenna (130) and is connected to the flat circuit carrier (125) or the circuit board (125). (125) is in intervention.

Description

The present invention relates to a radar sensor. In particular, the invention relates to a radar sensor for measuring distance on board a motor vehicle.Prior ArtOn board a motor vehicle, a radar sensor may be used to determine a distance to a surrounding object. On the basis of the determined distance, different comfort functions of the motor vehicle can be controlled. For example, a speed of the motor vehicle can be automatically controlled to a predetermined value, wherein a distance measurement to the front by means of the radar sensor ensures that a predetermined safety distance from a motor vehicle driving ahead is not undershot. Other applications of a radar sensor include an emergency braking function when it approaches an object rapidly, a distance warning system in order to make it easier for a driver of the motor vehicle to maintain a required safety distance from a motor vehicle driving ahead, or a parking aid for collision warning in the short range at a low driving speed.Radar sensors of this type are usually designed as an integrated module, the module providing already evaluated or partially evaluated distance or approach signals at an electrical interface. All components required for emitting, receiving and correlating radar signals are included in the module.Such a radar sensor usually comprises a radar antenna, a high-frequency circuit for driving the radar antenna and a radar lens for focusing the radar radiation emitted by the radar antenna or incident therein. In order to prevent high-frequency radiation of the radar antenna from interfering with the operation of the high-frequency circuit or high-frequency radiation of the high-frequency circuit from interfering with the radar antenna, it is known to provide a metal screen or a metal cage which comprises a recess through which the radar antenna emits or receives radar radiation in order to shield the radar antenna from the high-frequency circuit. As a result, although electromagnetic radiation and in particular the high-frequency radar radiation can be shielded, so that the high-frequency circuit and the radar antenna do not influence one another, the performance or characteristic of the radar antenna can also be impaired in this case.The publications EP 1 880 174 B1, EP 2 112 482 A1 and EP 0 871 241 A2 disclose radar antennas in different configurations.It is an object of the present invention to suppress scattered radiation in the region of a radar antenna of a radar sensor.The invention achieves this object by means of a radar sensor having the features of the independent claim. Dependent claims represent preferred embodiments.Disclosure of the InventionA radar sensor according to the present invention includes a radar antenna, a radar lens, and a funnel element between the radar antenna and the radar lens. The funnel element comprises a material which absorbs radar radiation emitted by the radar antenna. The radar antenna is arranged together with further high-frequency components on a planar circuit carrier or a printed circuit board. The high-frequency circuit keeps a predetermined radial distance from the radar antenna on the planar circuit carrier or the printed circuit board. The funnel element is placed on the planar circuit carrier or the circuit board in the region of the radar antenna and is in engagement with the planar circuit carrier or the circuit board.This makes it possible to dispense with the use of a shielding metal surface which can reflect radar radiation and other electromagnetic radiation. A directional characteristic of the radar antenna may be unaffected by the absorbing material. This may allow for an improved operation of the radar sensor. In addition, it may be easier to adapt a geometry of the radar sensor, in particular of the radar lens, to an emission characteristic of the radar antenna. As a result, the emission characteristic of the radar sensor can be better controllable and development and production costs can be saved. Because the radar antenna is arranged together with further high-frequency components on a planar circuit carrier or a printed circuit board, the radar antenna and the electronic high-frequency components can be embodied as integrated on the circuit carrier, as a result of which space, weight and production costs of the radar sensor can be reduced. The funnel element can nevertheless effectively suppress the radar antenna and the radio-frequency components from being influenced mutually.The funnel element faces the radar antenna with its narrow side and the radar lens with its wide side. In a preferred embodiment, the funnel element abuts the radar lens. This makes it possible to ensure that the radar radiation emitted by the radar antenna falls onto a geometric region of the radar lens which is designed for focusing the radar radiation. Distortion of the radar radiation, in particular in a radially outer edge region of the radar lens, can thereby be reduced.In the radially outer region of the radar lens, in particular a lens edge can be situated which does not contribute to the focusing of the radar radiation, wherein the funnel element is configured to shield the lens edge from radar radiation of the radar antenna by absorption. The lens edge may be indispensable for design reasons. In particular, the lens edge can serve for connecting the radar lens to a housing in order to encapsulate the radar sensor against environmental influences. The essential mechanical structure of a known radar sensor can thus be maintained without distortion of the radar radiation occurring in the region of the lens edge.In one embodiment, the funnel element comprises a cylindrical section in the region of the radar lens. The cylindrical portion may help to better shield the lens edge from radar radiation from the radar antenna.In a further embodiment, the funnel element comprises a radially inwardly directed collar in the region of the radar antenna. The collar can contribute to suppressing electromagnetic radiation running radially with respect to a main propagation direction of the radar radiation in an improved manner. Particularly, when the radar antenna is mounted on a planar member such as a circuit board, the collar can suppress surface waves running along the surface of the member. Furthermore, the collar can serve for a mechanical connection of the radar lens to the radar antenna or to a planar element on which the radar antenna is mounted or formed. A contact pressure force of the funnel element can be distributed over a larger area by the collar. A mechanical structure of a modularally encapsulated radar sensor can thereby be facilitated or improved.The funnel element may comprise a fastening element for attachment to the radar antenna, so that the radar lens with the funnel element may form a separately manageable unit. Mounting of the radar sensor may thus be simplified.The funnel element can be made of a plastic material absorbing radar radiation. For this purpose, the plastic can have predetermined dielectric properties and resistive and / or magnetic substances can be mixed with the plastic for converting radar radiation into heat. This can allow efficient absorption of the radar radiation to be achieved.In one embodiment, the material of the funnel element is porous. Reflection and refraction of radar radiation at pore boundaries may help to increase the absorptivity of the funnel element.The invention will now be described in more detail with reference to the accompanying figures, in which: FIG. 1 shows a radar sensor; FIG. 2 shows a section through a material of the funnel element from FIG. 1 ; and FIG. 3 shows a section through an alternative material analogous to FIG. 3. 2 is.DETAILED DESCRIPTION OF EMBODIMENTSFIG. 1 shows a radar sensor 100. Radar sensor 100 is designed, in particular, for use on board a motor vehicle. Radar sensor 100 is preferably a long-range radar sensor (LRR) for determining a distance and, if necessary, a speed of an object that is up to several 100 m away. The radar radiation emitted by radar sensor 100 is preferably in the range of approximately 24 or 77 GHz.Radar sensor 100 includes a base plate 105 and a radar lens 115 that terminate a housing 110 at opposite ends. In other embodiments, the components of radar sensor 100 may also be protected from environmental influences in a manner different from that provided by housing 110 and base plate 105. The radar lens 115 has a radially outer lens edge 120, which can be fastened to the housing 110. Furthermore, the radar sensor comprises a circuit carrier or a circuit board 125 on which a radar antenna 130 and a high-frequency circuit 135 are arranged. The radar antenna 130 may be formed on the board 125 in the form of a printed circuit. A funnel element 140 extends between the circuit board 125 and the radar lens 115, the narrow side of which funnel element faces the radar antenna 130 and the wide side of which funnel element faces the radar lens 115. In the region of the radar lens 115, a fastening element 145 for fastening to the radar lens 115 is formed on the funnel element 140.An interface 150 is optionally attached to the base plate 105 in order to provide electrical signals with respect to a measurement result of the radar sensor 100 to the outside and for connection to a power supply. Interface 150 may be connected to further electronic components in radar sensor 100, which will not be discussed in greater detail here.The high frequency circuit 135 on the board 125 preferably maintains a predetermined radial distance from the radar antenna 130 to allow the funnel element 140 to be seated on the board 125 in this area. The funnel element 140 lies with its narrow side in the region of the radar antenna 130 and is preferably in engagement with the printed circuit board 125. The wide side of the funnel element 140 lies in the region of the radar lens 115 and preferably lies axially against the radar lens 115, with the result that the funnel element 140 is fixed in the axial direction between the radar lens 115 and the printed circuit board 125.The radar lens 115 is preferably planar on the side facing the funnel element 140. A clear width of the funnel element 140 on the radar lens 115 is preferably dimensioned such that a region of the radar lens 115 lying radially inside the lens edge 120, which region is relevant for focusing emerging or entering radar radiation, adjoins the cavity formed by the funnel element 140.Preferably, a cylindrical section 155 is formed on the funnel element 140 in the region of the radar lens 115. The cylindrical portion 155 may make radar radiation exiting the radar antenna 130 difficult to reach the lens edge 120, where difficult to control reflections and distortion of radar radiation may occur.On its narrow side facing the radar antenna 130, the funnel element 140 preferably has a radially inwardly extending collar 160. As a result, a bearing surface of the funnel element 140 on the circuit board 125 can be enlarged. Surface waves between the radar antenna 130 and the high-frequency circuit 135 can thereby be effectively attenuated.In the region of the cylindrical section 155, a fastening element 145 can be formed on the funnel element 140 in order to be able to fasten the funnel element 140 to the radar lens 115. This can result in a separately manageable unit, which facilitates mounting of the radar sensor 100. In the present embodiment, for example, the circuit board 125 can be arranged in the housing 110 before the radar lens 115 together with the funnel element 140 is placed onto the housing 110 from above, whereby the housing 110 is closed off at the top axially and the circuit board 125 is optionally pressed axially against a holding structure of the housing 110. Before or after the mounting of the radar lens 115 and the funnel member 140, the bottom plate 105 may be mounted on the bottom surface of the housing 110.The funnel element 140 is made of a material whose properties and structure promote absorption of radar radiation. Both the material and the structure are preferably optimized for a wavelength of radar radiation which is emitted upward by the radar antenna 130 in FIG. 1 in a normal operation.The funnel element 140 is primarily configured to keep the radiation emanating from the radar antenna 130 away from elements which can either be disturbed by radar radiation, in particular the high-frequency circuit 135, or which can disturb a measurement by means of the radar radiation, such as the lens edge 120, due to their refractive properties. In the second place, the funnel element 140 is also configured to keep radio-frequency radiation, which is neither generated by the radar antenna 130 nor has entered the radar sensor 100 through the radar lens 115, away from the radar antenna 130. Such radiation can be generated by the high-frequency circuit 135, for example, in the form of a fundamental or harmonic frequency.FIG. 2 shows a section through a material of the funnel element 140 from FIG. 1. the funnel element 140 is preferably produced from a plastic. The plastic of the funnel element 140 preferably has semiconducting properties, i.e. its conductivity lies between those of a conductor and an insulator, in particular in the range between 10 3 and 10 -8 S / cm. Thereby, a portion of radar radiation to which the funnel element 140 is exposed can be converted into heat within the material, thereby effectively absorbing the radar radiation.In the preferred embodiment shown in FIG. 2, the material of the funnel element 140 is additionally interspersed with metallized balls or metal balls 205 of a predetermined diameter, which can be selected in particular depending on a wavelength of the radar radiation. As is known, the metal balls 205 may improve the absorption properties of the funnel member 140. In a variant of the illustrated embodiment, the metal balls 205 may also be applied to an inner or outer surface of the funnel element 105, for example by means of a corresponding paint.FIG. 3 shows a section through an alternative material of the funnel element 140 analogous to the illustration of FIG. 2, The embodiment illustrated can be combined with the embodiment of FIG. 2. Pores 210 pass through the material of the funnel element 140, the size range of which pores is preferably adapted to a wavelength of the radar radiation emitted by the radar antenna 130. If radar radiation penetrates the material of the funnel element 140, it is partially reflected at boundaries of the pores 210, as a result of which interference effects can form, which increase the absorption of the radar radiation.

Claims

Radar sensor (100) comprising: - a radar antenna (130); - a radar lens (115); a funnel element (140) between the radar antenna (130) and the radar lens (115), - wherein the funnel element (140) comprises a material which absorbs radar radiation emitted by the radar antenna (130), - wherein the radar antenna (130) is arranged together with further high-frequency components (135) on a planar circuit carrier (125) or a printed circuit board (125), - wherein the high-frequency circuit (135) on the planar circuit carrier (125) or the printed circuit board (125) holds a predetermined radial distance from the radar antenna (130), wherein the funnel element (140) is placed on the planar circuit carrier (125) or the printed circuit board (125) in the region of the radar antenna (130) and is in engagement with the planar circuit carrier (125) or the printed circuit board (125).The radar sensor (100) of claim 1, wherein the funnel element (140) abuts the radar lens (115).Radar sensor (100) according to Claim 2, wherein a radially outer lens edge (120) of the radar lens (115) does not contribute to the focusing, and the funnel element (140) is configured to shield the lens edge (120) from radar radiation of the radar antenna (130) by absorption.Radar sensor (100) according to one of the preceding claims, wherein the funnel element (140) has a cylindrical section (155) in the region of the radar lens (115).Radar sensor (100) according to one of the preceding claims, wherein the funnel element (140) has a radially inwardly pointing collar (160) in the region of the radar antenna (130).Radar sensor (100) according to one of the preceding claims, wherein the funnel element (140) has a fastening element (145) for attachment to the radar antenna (130), such that the radar lens (115) forms a unit which can be handled separately with the funnel element (140).Radar sensor (100) according to one of the preceding claims, wherein the funnel element (140) is produced from a plastic material absorbing radar radiation.Radar sensor (100) according to one of the preceding claims, wherein the material of the funnel element (140) is porous.

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