RADAR SENSOR DEVICE FOR A MOTOR VEHICLE, DRIVER ASSISTANCE SYSTEM, MOTOR VEHICLE AND METHOD FOR DETECTING AN OBJECT

Description

[0001] The invention relates to a radar sensor device for a motor vehicle for detecting an object in a surrounding area of ​​the motor vehicle, having an antenna configuration comprising at least two transmitting antennas for transmitting transmission signals, wherein the respective main beam directions of the transmission characteristics of the at least two transmitting antennas have different elevation angles and different azimuth angles. The invention also relates to a driver assistance system, a motor vehicle, and a method.

[0002] Radar sensor devices are typically used in motor vehicles to detect objects or obstacles in the area surrounding the motor vehicle. For this purpose, the radar sensor devices or radar sensors have transmitting antennas that emit signals in the form of electromagnetic waves. The transmitted signals are reflected by an object in the area surrounding the vehicle, and the reflected signals are received again as received signals or echo signals by the transmitting antennas themselves or by a separate receiving antenna. Information about the object, such as the position of the object in relation to the motor vehicle, the speed of the object, and the angle of the object in relation to the motor vehicle, can be obtained from the transmitted signals and the received signals. Both horizontal angles or azimuth angles and vertical angles or elevation angles are recorded.Such a radar sensor used for angle-resolved object location is known, for example, from WO 2015 / 028175 A1. This radar sensor comprises two transmitting antennas, each with a different operating direction in elevation and azimuth. A similar radar device with multiple transmitting and receiving antennas is disclosed in DE102013216951A1.

[0003] This information can be fed into a driver assistance system in the vehicle, such as adaptive cruise control, a lane change assistant, or similar. Automatic emergency braking systems also use information from radar sensors to initiate automatic emergency braking in the event of an imminent collision between the vehicle and an obstacle. However, for this application, measuring the elevation angle of the objects is particularly important, as emergency braking is not permitted for objects on the ground that can be driven over, such as manhole covers, or objects that can be driven under, such as sign gantries. Due to their material and shape, such objects reflect the transmission signal or radar signal well, but do not pose any obstacle to the vehicle.

[0004] It is an object of the present invention to provide a solution as to how elevation angles and azimuth angles of objects in an area surrounding a motor vehicle can be determined particularly accurately and reliably.

[0005] This object is achieved according to the invention by a radar sensor device, a driver assistance system, a motor vehicle, and a method having the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figures.

[0006] In one embodiment of a radar sensor device according to the invention, which serves to detect an object in a surrounding area of ​​a motor vehicle, said device has an antenna configuration, wherein the antenna configuration in particular comprises at least two transmitting antennas for transmitting transmission signals. In particular, respective main beam directions of transmission characteristics of the at least two transmitting antennas have different elevation angles and different azimuth angles. Furthermore, the antenna configuration in particular has at least two receiving antennas, separate from the transmitting antennas, for receiving the transmission signals reflected in the surrounding area as received signals, wherein respective main beam directions of reception characteristics of the at least two receiving antennas have different elevation angles.

[0007] A radar sensor device for a motor vehicle for detecting an object in a surrounding area of ​​the motor vehicle preferably has an antenna configuration comprising at least two transmitting antennas for transmitting transmission signals. Respective main beam directions of transmission characteristics of the at least two transmitting antennas have different elevation angles and different azimuth angles. Furthermore, the antenna configuration has at least two receiving antennas, separate from the transmitting antennas, for receiving the transmission signals reflected in the surrounding area as received signals. Respective main beam directions of reception characteristics of the at least two receiving antennas have different elevation angles.

[0008] Such radar sensor devices can be arranged on the motor vehicle, wherein one radar sensor device can be arranged, for example, in a front region of the motor vehicle and another radar sensor device can be arranged in a rear region of the motor vehicle. By means of the radar sensor device, in particular an azimuth angle of the object and an elevation angle of the object can be determined. The azimuth angle is in particular a horizontal angle in a horizontal plane which is spanned, for example, by a vehicle longitudinal axis and a vehicle transverse axis. The azimuth angle is related to a reference axis, for example the vehicle longitudinal axis. The elevation angle is a vertical angle in a vertical plane which is spanned, for example, by the vehicle longitudinal axis and a vehicle vertical axis.The elevation angle is also referenced to a reference axis, for example, the vehicle's longitudinal axis. The reference axis for the elevation extends, in particular, to the installation height of the radar sensor device on the vehicle, parallel to the vehicle's roadway. The elevation angle describes the height of the object above the vehicle's roadway.

[0009] The radar sensor device is provided with an antenna configuration comprising multiple transmitting and receiving antennas. The transmitting and receiving antennas can, for example, be arranged separately from one another on a common antenna board. The transmitting and receiving antennas can each have a group of antenna elements. In particular, it is provided that the transmitting antennas are used successively to perform the measurements, whereas the receiving antennas are used simultaneously to perform the measurements. In other words, this means that the transmitting antennas are controlled sequentially to transmit a respective transmission signal, with all receiving antennas being controlled simultaneously to receive the reflected transmission signal transmitted by the respective active transmitting antenna. The receiving antennas can measure the azimuth angle using so-called digital beamforming.The azimuth angle is determined, in particular, from a phase shift between the transmitted signal and the received signal. The elevation angle is determined, in particular, from a power comparison of the signal levels or amplitudes of the transmitted signal and the received signal.

[0010] The two transmitting antennas have different directivities in both azimuth and elevation. The directivities in azimuth result from a horizontal antenna pattern, which describes the directivities of the transmitting antennas or the transmitting characteristics in the horizontal plane. In azimuth, the transmitting antennas have different horizontal components of the main beam directions, along which the directivities, in particular the main lobes of the directivities, are oriented. The main beam directions of the transmitting characteristics therefore have different azimuth angles to the reference axis. The transmitting characteristics are thus pivoted horizontally relative to the reference axis by the respective azimuth angle. The directivities in elevation result from a vertical antenna pattern, which describes the directivities of the transmitting antennas in the vertical plane.The transmitting antennas have different vertical components of the main beam directions in elevation. The main beam directions of the transmitting patterns also have different elevation angles relative to the reference axis, so that the transmitting patterns are vertically tilted by the respective elevation angle relative to the reference axis.

[0011] This means that a first transmission characteristic of a first transmitting antenna covers a first azimuth angle range and a first elevation angle range, and a second transmission characteristic of a second transmitting antenna covers a second azimuth angle range and a second elevation angle range. The angle ranges may overlap in some areas. As a result, the transmission signals from the two transmitting antennas are transmitted into different sub-areas of the surrounding area of ​​the motor vehicle.

[0012] Furthermore, it is now provided that receiving antennas also have different directional effects in elevation. The receiving characteristics or directional characteristics of the at least two receiving antennas are oriented along different elevation angles, thus covering different elevation angle ranges. The receiving characteristics are therefore also pivoted vertically with respect to the reference axis by an elevation angle assigned to the respective receiving characteristic. By pivoting the receiving characteristics, the vertical reception range or field of view of the radar sensor device, which results from the elevation angle ranges of both receiving characteristics, is expanded.This means that a vertical opening angle of the field of view of the radar sensor device is increased so that an elevation angle measurement with a high angular resolution can be reliably carried out by the receiving antennas and the receiving channels assigned to the receiving antennas.

[0013] In particular, it is provided that the azimuth angles of the respective main beam directions of the reception characteristics of the at least two reception antennas are designed to be identical. This means that the reception antennas each cover the same azimuth angle range. However, for one of the reception antennas, the reception characteristic is modified in elevation so that the reception antennas cover different elevation angle ranges. The azimuth angle range covered by the reception antennas, which represents a horizontal field of view of the radar sensor device, is specified by a horizontal aperture angle. The horizontal aperture angle can ideally be 180°, for example, so that the half-space adjacent to the radar sensor device is covered. When the radar sensor device is installed on the motor vehicle, the azimuth angle range is therefore virtually omnidirectional.By modifying the elevation directional characteristic, improved object detectability in the vertical direction will be achieved, while detectability in the horizontal direction will not be negatively affected. This means that, in addition to the elevation angle measurement, the receiving antennas can reliably perform the azimuth angle measurement using digital beamforming, and in particular, without compromising sensor performance. The radar sensor device is thus designed for exceptional reliability.

[0014] Particularly preferably, a first main beam direction of a first transmission characteristic of a first transmitting antenna and / or a first reception characteristic of a first receiving antenna has a first elevation angle of 0° with respect to a reference axis oriented parallel to a roadway of the motor vehicle. A second main beam direction of a second transmission characteristic of a second transmitting antenna and a second reception characteristic of a second receiving antenna each has a second elevation angle different from 0°. The reference axis extends parallel to the roadway of the motor vehicle at the installation height of the radar sensor device, so that the respective first main beam directions of the first transmitting antenna and the first receiving antenna also extend parallel to the roadway of the motor vehicle.The respective second main beam directions of the second transmitting antenna and the second receiving antenna are oriented obliquely to the reference axis and thus to the horizontal plane.

[0015] The second main beam direction of the second transmitting antenna and the second main beam direction of the second receiving antenna can have different elevation angles or the same elevation angle. The second elevation angle can be positive, for example, so that the respective second main beam direction is oriented diagonally downwards in the direction of the roadway. By orienting the second transmitting characteristic in the direction of the roadway, a roadway area can be detected or illuminated so that, particularly in combination with the second receiving characteristic oriented in the direction of the roadway, objects close to the ground can be detected more effectively. Due to the improved detectability of these objects, they can be classified by evaluating the elevation angle, in particular as objects that the motor vehicle can drive over, for example manhole covers, or obstacles to the motor vehicle, for example other vehicles.The second elevation angle can, for example, be negative, so that the respective second main beam direction is oriented obliquely upwards towards the sky. By orienting the second transmission characteristic towards the sky, an area obliquely above the motor vehicle can be detected or illuminated so that, particularly in combination with the second reception characteristic oriented towards the sky, objects above the motor vehicle can be detected more effectively. Due to the improved detectability of these objects, they can be classified by evaluating the elevation angle, in particular as objects that the motor vehicle can drive under, for example sign gantries, or obstacles for the motor vehicle, for example trucks. The second elevation angle can have a value between 10° and 20°.

[0016] In particular, a vertical aperture angle of the second receiving characteristic is larger than a vertical aperture angle of the first receiving characteristic. This means that the receiving characteristic of the second receiving antenna is, on the one hand, widened in elevation and, on the other hand, pivoted in its main beam direction, for example, downwards toward the roadway. Thus, a second elevation angle range covered by the second receiving characteristic is enlarged, so that, particularly in combination with the downwardly pivoted second transmission characteristic of the second transmitting antenna, the detectability of objects near the ground can be significantly improved.

[0017] Preferably, an elevation angle difference between the main beam directions of the first and second receiving characteristics and / or a vertical aperture angle of the second receiving characteristic with respect to a vertical aperture angle of the first receiving characteristic is configured such that a received signal received by the second receiving antenna has a maximum attenuation of 6 dB compared to a received signal received by the first receiving antenna. The received signals received by the first and second receiving antennas originate in particular from the reflection of the same transmitted signal. The invention is based on the finding that an attenuation of an amplitude of the second receiving antenna on the associated receiving channel by up to 6 dB has no negative influence on the azimuth angle measurement.This means that the radar sensor device according to the invention can still be used to carry out the azimuth angle measurement reliably and accurately, while, on the other hand, an elevation angle measurement can be carried out more accurately, namely if an attenuation or damping of at most 6 dB results for objects or targets which are located in particular at the installation height of the radar sensor device on the motor vehicle.

[0018] In a further development of the invention, the antenna configuration comprises a third and a fourth receiving antenna, wherein a third and a fourth main beam direction of reception characteristics of the third and fourth receiving antennas have the first elevation angle, and wherein the azimuth angles of the main beam directions of all reception characteristics as well as the horizontal aperture angles of all reception characteristics are identical. In other words, this means that the antenna configuration comprises four receiving antennas that can simultaneously receive reflected transmission signals from the surrounding area. In azimuth and horizontal directions, all reception characteristics cover, in particular, the same azimuth angle range.The main beam directions of all reception characteristics are oriented in particular along a viewing direction of the radar sensor device when installed on the motor vehicle, whereby the viewing direction is related to the reference axis for the azimuth angle. For a radar sensor installed at the rear, whose viewing direction is oriented straight ahead backwards, opposite the direction of travel, the viewing direction is oriented along the vehicle's longitudinal axis, which represents the reference axis. The azimuth angle in this case is 0°. For a radar sensor with a viewing direction directed obliquely to the side, which deviates horizontally from the reference axis, the azimuth angle is different from 0°. The horizontal aperture angles of all reception characteristics are ideally 180°, for example, so that all reception characteristics cover the half-space adjacent to the radar sensor device in the horizontal direction.

[0019] This ensures reliable azimuth angle measurement via digital beamforming.

[0020] In elevation, three of the four receiving antennas—the first, third, and fourth receiving antennas—cover the same elevation angle range, which is oriented along the elevation angle reference axis, which is parallel to the roadway. The second transmitting antenna covers an elevation angle range oriented vertically obliquely to the reference axis and thus obliquely to the main beam directions of the other receiving antennas. With a second receiving characteristic oriented obliquely downwards, objects that are not at the installation height of the radar sensor device, in particular below the installation height of the radar sensor device, can be detected and classified particularly well.

[0021] The antenna configuration preferably comprises a third transmitting antenna, wherein a third main beam direction of a third transmission characteristic of the third transmitting antenna has the first elevation angle, wherein an azimuth angle of the second main beam direction of the second transmitting antenna is formed between the azimuth angles of the first and third main beam directions, and wherein a horizontal aperture angle of the second transmission characteristic is greater than a respective horizontal aperture angle of the first transmission characteristic and the third transmission characteristic. This means, for example, that the azimuth angle of the second transmitting antenna has 0° to the reference axis oriented in the viewing direction, and the second main beam direction of the second transmitting antenna extends in the horizontal plane along the reference axis, for example, the vehicle's longitudinal axis.The respective azimuth angles of the first and third transmission characteristics are in particular of equal magnitude, with the first transmission characteristic, for example, being pivoted horizontally to one side and the transmission characteristic of the third transmission antenna being pivoted horizontally to the other side. The first and third transmission characteristics are therefore pivoted towards a respective side and are thereby focused. The first and third transmission antennas are therefore sectorizing transmission antennas, with their main beam directions lying horizontally in elevation. The horizontal aperture angles of the first and third reception characteristics cover a total horizontal range of approximately 180°. The horizontal aperture angle of the second transmission characteristic is ideally 180°, so that the second transmission characteristic illuminates the half-space.The directional characteristic of the second transmitting antenna is thus virtually omnidirectional in azimuth, and in elevation it is tilted towards the ground, for example.

[0022] Preferably, the second main beam direction of the second transmission characteristic is oriented obliquely downwards in the direction of a roadway of the motor vehicle. A control device of the radar sensor device is designed to detect a blockage of the radar sensor device based on the extent and / or continuity of a detection point distribution in a transmission signal transmitted by the second transmission antenna, reflected by the roadway, and received as a received signal by at least one of the reception antennas. According to this embodiment, the radar sensor device is thus designed to detect a blocked state of the radar sensor device, which may negatively impact the functionality of the radar sensor device.In such a blocked state, the radar sensor device is covered, for example, by a layer of dirt, such as a layer of ice, a layer of snow, or a layer of dirt, and is thus hindered in transmitting and / or receiving the radar signals. To detect blockages, the road is illuminated in sections by the second transmitting antenna, whose transmission characteristics are inclined downwards towards the roadway or the ground. The transmitted signal reflected from the roadway is detected again as a received signal by at least one of the receiving antennas, in particular by the second receiving antenna, whose reception characteristics are also directed towards the ground. To evaluate the blockage detection, the detection point distribution or point cloud is determined based on the received signal.The detection point distribution includes reflection points resulting from the reflection of the transmission signal of the second transmitting antenna on the ground.

[0023] To determine the detection point distribution, the values ​​of the detection points or reflection points are plotted against a distance or a range from the vehicle. The distance can be obtained, for example, from the radar signal's travel time. Whether the detection points are actually ground reflections can be verified or verified using the received signals from the three other receiving antennas. The values ​​of the detection points are determined, in particular, as a ratio between a measured radial velocity of the ground, which represents a stationary object, and the speed of the vehicle. This point cloud can then be evaluated by determining an extent of the point cloud corresponding to the azimuth direction.

[0024] The invention is based on the finding that the maximum extent of the point cloud for the azimuth direction is limited by the horizontal field of view of the radar sensor device. If the sensor is not blocked, detection points should be able to be recorded continuously across the entire horizontal field of view. If the extent of the point cloud corresponding to the azimuth direction does not correspond to the horizontal field of view of the radar sensor device and / or if detection points are not continuously present across the entire horizontal field of view, the blockage of the radar sensor is detected. In particular, the degree of blockage or a blocked angular range can be determined based on the continuity and / or the extent of the detection point distribution.For example, if there are no detection points within a certain area of ​​the point cloud, it can be assumed that the radar sensor is blind for the corresponding azimuth angle range. For example, if there are only a few detection points within a certain area of ​​the point cloud, it can be assumed that the radar sensor's visibility is limited in the corresponding azimuth angle range.

[0025] If the complete or partial blockage of the radar sensor device has been detected, a warning signal can be issued to a driver of the motor vehicle so that he or she is informed of the limited functionality of the radar sensor device.

[0026] It proves to be particularly advantageous if the second transmission characteristic of the second transmitting antenna, oriented along the second main beam direction, has a zero point at a predetermined zero-value angle. The zero-value angle is in particular a predetermined elevation angle between a zero-value direction and the main beam direction of the second transmitting antenna. The zero point is therefore oriented along the zero-value direction. All points in the antenna diagram at which the radiated energy is practically zero are referred to as zero points. Along the zero-value direction predetermined by the zero-value angle, the second transmitting antenna therefore emits practically no radiated energy. This means that essentially no transmitted signal is reflected at an object located in the zero point of the second transmission characteristic, and thus essentially no received signal is received.The zero point can be generated, for example, by controlling several transmitting antenna elements of the second transmitting antenna with different phases.

[0027] A control device of the radar sensor device is now designed to determine an elevation angle of the object when the object enters the zero point based on the received signal received by at least one of the receiving antennas and the zero value angle. This means that the elevation of the object is determined as soon as the object enters the zero point. The object enters the zero point when, for example, the motor vehicle with the radar sensor device moves towards the object and the object, at a specific distance from the motor vehicle, which depends on the elevation of the object, transitions from the directional characteristic of the second transmitting antenna to the zero point. In other words, the time at which the object enters the zero point depends on the distance of the object from the motor vehicle and the elevation angle or the elevation of the object.The passing of the object can be determined based on a drop in the signal amplitude in the received signal. The elevation of the object is detected, in particular, by comparing the amplitudes of the reflected transmission signal from the second transmitting antenna and the reflected transmission signal from the first and / or third transmitting antenna, which does not have a zero point.

[0028] Using the zero point, the elevation angles of objects can be detected with particular precision, and the objects can be classified based on the detected elevation angles. For example, if the second transmission characteristic is oriented toward the roadway, objects close to the roadway can be detected, and based on the object's elevation angle—i.e., its height above the roadway—it can be used to distinguish whether the object is traversable by the vehicle. The object is then assessed as traversable by the vehicle if the object's elevation angle falls below a predetermined threshold.The threshold is selected, for example, such that the elevation value of an object near the ground and connected to the roadway, such as a manhole cover, detected by the radar sensor device falls below the threshold, while the elevation value of an object located at a distance from the roadway, such as a body part of another motor vehicle, exceeds the threshold. If the zero point is oriented toward the sky, i.e., diagonally upwards, objects that can be driven under, such as sign gantries, can be detected and classified as such.

[0029] Particularly preferably, the second main beam direction and the zero point of the second transmission characteristic of the second transmission antenna are oriented obliquely downwards in the direction of a roadway of the motor vehicle, wherein a control device of the radar sensor device is designed to detect a misalignment of the radar sensor device based on a transmission signal emitted by the second transmission antenna, reflected by the roadway, and received as a received signal by at least one of the reception antennas, if a deviation between a distance value of the zero point from the motor vehicle, detected based on the received signal, and a predetermined reference value exceeds a predetermined threshold. The predetermined reference value corresponds to a distance value at which the zero point strikes the roadway with a correctly installed, non-misaligned radar sensor.This reference value can be stored in a memory device, for example, to check the vertical adjustment, i.e., to check the viewing direction of the radar sensor device in elevation. If the detection point distribution is recorded, for example, in connection with the blockage measurement, the vertical adjustment can be checked based on the detection point distribution. To do this, a check is carried out to determine the distance in the detection point distribution at which no detection points are present, i.e., the distance at which a signal drop occurs in the detection point distribution. This range in the detection point distribution at which no detection points occur results from the zero point of the second transmission characteristic. If this distance of this range corresponds to the predetermined reference value or lies within a tolerance range, it is assumed that the radar sensor is correctly adjusted.If the distance values ​​differ from each other, the misalignment of the radar sensor device is detected and, for example, a warning signal is issued to the driver of the vehicle.

[0030] The invention also relates to a driver assistance system for a motor vehicle with a radar sensor device according to the invention. The driver assistance system can perform assistance functions based on the azimuth angle and elevation angle of objects in the surrounding area of ​​the motor vehicle detected by the radar sensor device. The driver assistance system is designed, in particular, as an automatic emergency braking assistant. Based on the elevation angle of the objects detected by the radar sensor device and the classification of the objects, it can be assessed whether the driver assistance system needs to perform emergency braking or not. If, for example, objects have been classified as being driveable over or under, automatic emergency braking of the motor vehicle can be omitted.If objects have been classified as impassable or impassable, i.e., as obstacles for the vehicle, the driver assistance system can trigger automatic emergency braking of the vehicle. The driver assistance system is designed to be particularly reliable because the radar sensor device is configured to detect a blocked state and / or misalignment. The driver assistance system can also have an output device that can issue warning signals to the driver in the event of a blocked state and / or misalignment.

[0031] A motor vehicle according to the invention comprises a driver assistance system according to the invention. The motor vehicle is designed, in particular, as a passenger car.

[0032] The invention further relates to a method for detecting an object in a surrounding area of ​​the motor vehicle, in which transmission signals are emitted by at least two transmitting antennas, wherein respective main beam directions of transmission characteristics of the at least two transmitting antennas have different elevation angles and different azimuth angles. Furthermore, the transmission signals reflected in the surrounding area are received as received signals by at least two receiving antennas separate from the transmitting antennas, wherein respective main beam directions of reception characteristics of the at least two receiving antennas have different elevation angles.

[0033] The preferred embodiments presented with reference to the radar sensor device according to the invention and their advantages apply accordingly to the driver assistance system according to the invention, to the motor vehicle according to the invention and to the method according to the invention.

[0034] The terms "in front of", "behind", "above", "below", "vertical", "horizontal", "oblique", "azimuth", "elevation", etc. indicate the given position and orientation when the radar sensor device is used as intended and arranged as intended on the motor vehicle and when an observer is then standing in front of the motor vehicle and looking along a longitudinal axis (L) of the motor vehicle.

[0035] Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are to be regarded as encompassed and disclosed by the invention that are not explicitly shown and explained in the figures, but which emerge and can be produced by separate combinations of features from the explained embodiments. Embodiments and combinations of features are also to be regarded as disclosed that therefore do not have all the features of an originally formulated independent claim.Furthermore, embodiments and combinations of features are to be regarded as disclosed, in particular by the embodiments set out above, which go beyond or deviate from the combinations of features set out in the reliances of the claims.

[0036] The invention will now be explained in more detail using preferred embodiments and with reference to the accompanying drawings.

[0037] Showing: Fig. 1 shows a schematic representation of an embodiment of a motor vehicle according to the invention; Fig. 2 shows a schematic representation of an embodiment of an antenna configuration for a radar sensor device; Fig. 3a, b shows antenna diagrams of transmitting antennas of the antenna configuration from Fig. 2 ; Fig. 4 an antenna diagram of the receiving antennas of the antenna configuration from Fig. 2 ; Fig. 5 shows a schematic representation of an embodiment of a motor vehicle according to the invention in a side view; Fig. 6 shows a schematic representation of an embodiment of a motor vehicle detecting an azimuth angle of a stationary object; and Fig. 7 shows a schematic representation of a detection point distribution used to determine a misalignment and / or a blockage of the radar sensor device.

[0038] In the figures, identical and functionally identical elements are provided with the same reference numerals.

[0039] Fig. 1 shows a motor vehicle 1 according to the present invention. In the present case, the motor vehicle 1 is designed as a passenger car. The motor vehicle 1 comprises a driver assistance system 2, which can be designed, for example, as an automatic emergency braking assistance system and / or an automatic adaptive cruise control system. The driver assistance system 2 has a control device 3, which is designed to communicate with radar sensor devices 4 of the driver assistance system 2. The control device 3 is embodied here by a vehicle-mounted control unit, but the control device 3 can also be integrated into the radar sensor devices 4.In the present case, the motor vehicle 1 has two radar sensor devices 4, wherein a first radar sensor device 4 is arranged in a front region 5 of the motor vehicle 1 and can monitor a surrounding area 6 of the motor vehicle 1 in front of the motor vehicle 1 and wherein a second radar sensor device 4 is arranged in a rear region 7 of the motor vehicle 1 and can monitor the surrounding area 6 behind the motor vehicle 1.

[0040] The radar sensor devices 4 are designed to detect objects in the surrounding area 6 of the motor vehicle 1. For this purpose, each radar sensor device 4 has an antenna configuration 8, which has at least two transmitting antennas Tx1, Tx2 for transmitting transmitted signals and at least two receiving antennas Rx1, Rx2 for receiving the received signals reflected in the surrounding area 6. Information about the objects, for example a relative speed and a position of the objects, can be extracted from the received signals. In particular, the radar sensor device 4 can perform an azimuth angle measurement to measure an azimuth angle Ψ of the object and an elevation angle measurement to measure an elevation angle Ω of the object.The azimuth angle Ψ is a horizontal angle in a plane spanned by a vehicle longitudinal axis L and a vehicle transverse axis Q with respect to a reference axis, for example with respect to the vehicle longitudinal axis L. The elevation angle Ω is a vertical angle in a plane spanned by the vehicle longitudinal axis L and a vehicle vertical axis H (perpendicular to the plane of the drawing) with respect to a reference axis, for example again with respect to the vehicle longitudinal axis L. The elevation angle Ω indicates a height of the object above the ground or a roadway 16 of the motor vehicle 1.

[0041] In Fig. 2 1 shows an embodiment of the antenna configuration 8 of the radar sensor device 4. In this case, three transmitting antennas Tx1, Tx2, Tx3 and four receiving antennas Rx1, Rx2, Rx3, Rx4 are arranged on an antenna board 9, wherein a geometric arrangement of the transmitting antennas Tx1 to Tx3 and the receiving antennas Rx1 to Rx4 is shown merely as an example. The transmitting antennas Tx1, Tx2 are controlled in particular for the sequential transmission of the transmitted signals or radar signals in the form of electromagnetic waves, for example by the control device 9. This means that the transmitting antennas Tx1, Tx2 transmit transmitted signals one after the other. The receiving antennas Rx1, Rx2 are controlled for the simultaneous reception of the received signals. This means that the receiving antennas Rx1, Rx2 receive the reflected transmitted signals simultaneously. The azimuth angle measurement is carried out by the receiving antennas Rx1, Rx2 using digital beamforming.

[0042] A first transmitting antenna Tx1, a second transmitting antenna Tx2 and a third transmitting antenna Tx3 point in both azimuth A (see Fig. 3a ) as well as in elevation E (see Fig. 3b ) have differently shaped directional characteristics or transmission characteristics Sx1, Sx2, Sx3. The first and third transmitting antennas Tx1, Tx3 are sectorized transmitting antennas, whose transmission characteristics Sx1, Sx3, as shown in a horizontal antenna diagram in Fig. 3a shown, each illuminate or cover limited, laterally aligned azimuth angle ranges, while the transmission characteristic Sx2 of the second transmission antenna Tx2 in particular illuminates the entire half-space. The second transmission characteristic Sx2 can therefore be described as omnidirectional. A second main beam direction HSx2, along which the second transmission characteristic Sx2 of the second transmission antenna Tx2 is oriented, has an azimuth angle Ψ of 0° to a reference axis which is oriented, for example, along the vehicle's longitudinal axis L. Relative to the second main beam direction HSx2, a first main beam direction HSx1 of the first transmission characteristic Sx1 of the first transmission antenna Tx1 is tilted by a negative azimuth angle Ψ. Thus, in a radar sensor device 4 arranged at the rear of the motor vehicle 1, the first transmission characteristic Sx1 is pivoted in the direction of a driver's side of the motor vehicle 1.Relative to the second main beam direction HSx2, a third main beam direction HSx3 of the third transmission characteristic Sx3 of the third transmission antenna Tx3 is tilted by a positive azimuth angle Ψ, whereby the third transmission characteristic Sx3 is pivoted in the direction of a passenger side of the motor vehicle 1.

[0043] As can be seen from the vertical antenna pattern according to Fig. 3b As shown, the first and third main beam directions HSx1, HSx3 lie horizontally at elevation E. This means that the main beam directions HSx1, HSx3 have an elevation angle Ω of 0° to a reference axis, for example, the vehicle's longitudinal axis L. At elevation E, the first and third transmitting antennas Tx1, Tx3 therefore have the same directional characteristic Sx1, Sx3, focused horizontally and aligned parallel to the roadway 16 or the ground. The second transmitting antenna Tx2, however, has a downwardly inclined directional characteristic Sx2, which here also has a zero point N. When the radar sensor device 4 is installed on the motor vehicle 1, this zero point N strikes the roadway 16 at a predetermined distance 15 (see Fig. 5 ). However, the second directional characteristic Sx2 does not need to have a zero point N. By means of the second transmitting antenna Sx2, the roadway 16 is illuminated with a defined signal profile, through which, as will be explained later in connection with the Fig. 5 bis Fig. 7 explained, a blockage and a vertical misalignment of the radar sensor device 4 arranged on the motor vehicle 1 can be detected.

[0044] The transmitting antennas Tx1, Tx2, Tx3 have, as shown in Fig. 2 shown, a plurality of transmitting elements 10. The Fig. 3a und 3b The directional characteristics Sx1, Sx2, Sx3 shown are generated or realized by a suitable phase assignment of the transmitting elements 10. To generate the pivoted first and third transmitting characteristics Sx1, Sx3, the transmitting elements 10 arranged in several columns can be controlled in phase, so that the directivity or bundling in azimuth A results from a superposition of the waves emitted by the transmitting elements 10.

[0045] The four receiving antennas Rx1, Rx2, Rx3, Rx4 have in particular the same reception characteristics Dx1, Dx2, Dx3, Dx4 in azimuth, which are not shown separately, but which in particular in azimuth A correspond to the second transmission characteristic Sx2 (see Fig. 3a ). In other words, all reception characteristics Dx1, Dx2, Dx3, Dx4 cover the same azimuth angle range, which corresponds to the azimuth angle range of the second transmission characteristic Sx2. The azimuth angle range covered by the reception characteristics Dx1, Dx2, Dx3, Dx4 corresponds to a horizontal field of view of the radar sensor device 4, which in particular covers the half-space adjacent to the motor vehicle 1 and thus enables reliable azimuth angle measurement by means of digital beamforming. Main beam directions HDx1, HDx2, HDx3, HDx4 of the reception characteristics Dx1, Dx2, Dx3, Dx4 are thus oriented along the same direction in azimuth A and have, for example, an azimuth angle Ω of 0° to the reference axis.

[0046] In elevation E (see Fig. 4 ), the three main beam directions HDx1, HDx3, HDx4 of a first, third, and fourth receiving antenna Rx1, Rx3, Rx4 are horizontal, while a main beam direction HDx2 of a second receiving antenna Rx2 is oriented toward the ground 16. Furthermore, the receiving characteristic Dx2 of the second receiving antenna Rx2 is widened in elevation E. This enables better vertical detection of objects located near the radar sensor device 4 on the ground 16. In combination with the downwardly pivoted transmission characteristic Sx2, this receiving antenna Rx2 can be used to implement functions such as blockage detection and misalignment detection without the need for separate receiving antennas. The elevation angle range covered by the receiving characteristics Dx1, Dx2, Dx3, Dx4 results in a vertical field of view of the radar sensor device 4.

[0047] Up to now, the same elevation angle range was usually covered for the receiving antennas Rx1 to Rx4 in elevation in order to obtain a comparably high signal level on all four receiving channels assigned to the receiving antennas Rx1 to Rx4, as otherwise ambiguities can arise during digital beamforming in azimuth A. However, this procedure is now deviated from here, as it has been shown that an amplitude change on a receiving channel which is assigned to the Fig. 2 shown second receiving antenna Rx2, has the least negative impact on the performance of the azimuth angle measurement with regard to possible ambiguities. Furthermore, it was shown that an attenuation 12 of the amplitude on this receiving channel of up to 6 dB has no negative influence. This knowledge is used to modify the second receiving characteristic Dx2 of the second receiving antenna Rx2 at elevation E. The directional characteristic Dx2 is widened at elevation E and, at the same time, its main beam direction HDx2 is inclined towards the ground 16, so that for objects or targets at the installation height of the radar sensor device 4 on the motor vehicle 1, an attenuation 12 of at most 6 dB results.

[0048] The modification of the reception characteristic Dx2 of the second reception antenna Rx2 can be achieved, for example, by a linear phase assignment of individual reception elements 11 (see Fig. 2 ) of the second receiving antenna Rx2 in combination with a reduction of the total number of receiving elements 11 of this second receiving antenna Rx2. In particular, an arrangement applies to the receiving antennas Rx1, Rx2, Rx3, Rx4 in which the phase centers of the four receiving antennas Rx1, Rx2, Rx3, Rx4 are in the Fig. 2 shown vertical direction are all at the same height. In the Fig. 2 In the horizontal direction shown, certain distances d1, d2, d3 apply depending on a wavelength λ of the transmitted signal: d1 = λ, where d1 corresponds to the distance between the first and second receiving antennas Rx1, Rx2, d2 = 1.5λ, where d2 corresponds to the distance between the first and third receiving antennas Rx1, Rx3, and d3 = 0.5λ, where d3 corresponds to the distance between the third and fourth receiving antennas Rx3, Rx4. A linear scaling of the values ​​as well as a horizontal inversion of the arrangement of the receiving antennas Rx1, Rx2, Rx3, Rx4 is also possible.

[0049] For targets at sensor height, the modification of the second reception characteristic Dx2 does not result in any change in sensor performance. At the same time, however, it is possible to increase the area illuminated on the ground 16, especially for short distances, as well as to improve the sensitivity for objects on the ground 16. By comparing the power measured by the reception channel, which corresponds to the Fig. 2 shown second receiving antenna Rx2, with the power measured by the other receiving channels, an additional height estimate of the object can be made.

[0050] The height estimation or elevation measurement of the object can be improved in particular with the transmission characteristic Sx2, which has the zero point N. For this purpose, the motor vehicle 1 moves, as shown in Fig. 5 shown on lane 16. In Fig. 2 For the sake of clarity, only the transmitting characteristics Sx1, Sx2 of the first and second transmitting antennas Tx1, Tx2 are shown in elevation. The receiving characteristics Dx1, Dx2, Dx3, Dx4 in elevation E can be calculated as shown in Fig. 4 shown. The zero point N in the second transmission characteristic Sx2 is oriented along a zero value direction 14, which has a specific zero value angle 13 to the main beam direction HSx2 of the second transmission antenna. The zero point N hits the roadway 16 at a specific distance 15 predetermined by the zero value angle 13. According to this embodiment, an elevation angle of objects O1, O2 close to the ground can be determined, whereby the objects O1, O2 can be classified. In the present case, the object O1 is a manhole cover and does not represent an obstacle for the motor vehicle 1. The object O1 can be driven over by the motor vehicle 1. In the present case, the object O2 is an object spaced from the roadway, for example a body part of another vehicle, and represents an obstacle for the motor vehicle 1. The object O2 cannot be driven over by the motor vehicle 1.To classify objects O1, O2, motor vehicle 1 moves towards objects O1, O2. Object O1 will reach zero point N earlier than object O2. The zero point entry can be identified by a signal drop in the received signal, which corresponds to the transmitted signal of the second transmitting antenna Tx2 reflected by objects O1, O2. The signal drop in the received signal will therefore occur at a smaller distance value for the first object O1 than for the second object O2. The elevation of objects O1, O2 can be detected based on the distance value of the signal drop in the received signal. By comparing the elevation value with a predetermined threshold value, objects O1, O2 can then be classified. By orienting the second transmission characteristic Sx2 diagonally upwards towards the sky, objects that can be driven under, such as sign gantries, can be detected.

[0051] Furthermore, a blockage of the radar sensor device 4 can be detected using the antenna configuration 8. If a blockage occurs, for example due to a layer of dirt or a layer of ice, the radar sensor device 4 is prevented from reliably transmitting and / or receiving the radar signals. A vertical misalignment of the radar sensor device 4 can also be detected. Vertical misalignment is the deviation of a vertical viewing direction of the radar sensor device 4 from a predetermined viewing direction. Blockage detection and misalignment detection are therefore carried out with the same antenna configuration 8, which is also used to detect the relative speed, distance, and angle of the object. If a blockage and / or misalignment of the radar sensor device 4 is detected, a warning signal or an error message can be output to a driver of the motor vehicle 1.

[0052] To evaluate the blockage detection and monitor the vertical adjustment of the radar sensor device 4, specific detections obtained by the second transmitting antenna Tx2 and the second receiving antenna Rx2 can now be considered. In other words, a transmitted signal transmitted by the second transmitting antenna Tx2 and reflected by the ground 16 is received by the second receiving antenna Rx2 as a received signal. Whether the received signal originates from a reflection by the ground 16 can already be estimated at this point with a certain degree of probability by comparing the received power measured by the four receiving antennas Rx1 to Rx4 and based on the detected distance.If the reflection actually originates from the ground 16, it can be assumed that only the receiving antenna Rx2 provides sufficient power for detection, and that an angle measurement using digital beamforming across all receiving antennas Rx1 to Rx4 is not possible. Therefore, the only information available for detecting the ground reflection is the distance and relative velocity from the Doppler measurement.

[0053] For the evaluation of the detections obtained from the ground 16, the following relationship is used, which applies because the ground 16 represents a stationary object: ν r ν h = cos Ψ

[0054] This relationship is based on Fig. 6 , in which the motor vehicle 1 is shown detecting a stationary infrastructure object 17. vr is the measured radial velocity of the infrastructure object 17, and vh is the ground speed of the motor vehicle 1. The speed vh of the motor vehicle 1 can be detected by a vehicle-mounted speed sensor. The azimuth angle Ψ can be specified relative to a reference of 0° against the direction of travel.

[0055] To detect the possible blockage of the radar sensor device 4 and to monitor the vertical adjustment, the distribution of the ratio vr / vh of the detections over the distance R is considered. For a radar sensor 4 installed at the rear area 7 of the motor vehicle 1 and looking diagonally backwards, the Fig. 7 The detection point distribution 19 or point cloud shown results, with each detection point 22 representing a ground reflection (positive velocities correspond to a moving object). An extension 21 of the detection point distribution 19 along the vr / vh direction is limited by a field of view of the sensor device 4 in azimuth A. A Fig. 7 The upper limit of the detection point distribution 19 (in the vr / vh direction) shown in the figure has the value "1" for a radar sensor device 4 looking obliquely backwards, which corresponds to the azimuth angle Ψ of 0°. Positive and negative azimuth angles Ψ cannot be distinguished in the detection point distribution 19. Fig. 7 The lower limit of the detection point distribution 19 (opposite the vr / vh direction) shown is given by the maximum detection angle of the radar sensor device 4 to the side. Fig. 7 In the horizontal direction (R-direction) shown, the detection point distribution 19 contains detections 22 for all distances R at which a reflection of the transmitted signal from the ground 16 occurs. The detection point distribution 19 is interrupted at a certain distance R1 by an area 20 in which no detection points 22 occur. This distance R1 corresponds to the Fig. 6 distance 15 shown, at which the zero point N of the transmission characteristic Sx2 of the second transmitting antenna Tx2 strikes the ground 16. The detection point distribution 19 can be evaluated over a predetermined period of time, for example, a few minutes.

[0056] For blockage detection, the extent 21 of the detection point distribution 19 along the vr / vh direction is determined. In particular, a simultaneous check is performed to determine whether detections 22 are continuously present across the entire detected distance range. If the extent 21 of the detection point distribution 19 does not correspond to the field of view of the radar sensor device 4 and / or if detections 22 are not continuously present across the entire detected distance range in the R direction, the blockage of the radar sensor device 4 is detected. In this case, a degree of blockage and / or blocked angular ranges of the field of view of the radar sensor device 4 can also be determined.

[0057] The vertical adjustment of the radar sensor device 4 is checked by detecting the distance R1 of the area 20 (or its center of gravity) in which no detections 22 occur. This distance R1 is compared with a predetermined reference value. If the determined value of the distance R1 deviates from the reference value by more than a certain tolerance threshold, the vertical misalignment is detected. The reference value can, for example, be a distance value determined and stored by detecting the distance of the zero point N from the motor vehicle 1 for a radar sensor 4 correctly adjusted on the motor vehicle 1.

[0058] For additional statistical analyses, for example, to analyze reflections from other stationary objects such as guardrails or bridges, the detection point distributions obtained from the other reception channels can be used. This can further improve the reliability of the method.

Claims

1. Radar sensor device (4) for a motor vehicle (1) for sensing an object (O1, O2) in a surrounding region (6) of the motor vehicle (1), comprising a control device (3) and an antenna configuration (8) having at least two transmitting antennas (Tx1, Tx2) for emitting transmitted signals, wherein respective main radiation directions (HSx1, HSx2) of transmission characteristics (Sx1, Sx2) of the at least two transmitting antennas (Tx1, Tx2) have different elevation angles (Ω) and different azimuth angles (Ψ), wherein the antenna configuration (8) has at least two receiving antennas (Rx1, Rx2) separate from the transmitting antennas (Tx1, Tx2) for receiving the transmitted signals reflected in the surrounding region (6) as received signals, wherein respective main radiation directions (HDx1, HDx2) of reception characteristics (Dx1, Dx2) of the at least two receiving antennas (Rx1, Rx2) have different elevation angles (Ω), wherein a first main radiation direction (HDx1) of a first reception characteristic (Dx1) of a first receiving antenna (Rx1) has a first elevation angle (Ω) of 0° with respect to a reference axis oriented parallel to a roadway (16) of the motor vehicle (1) and a second main radiation direction (HDx2) of a second reception characteristic (Dx2) of a second receiving antenna (Rx2) has a respective second elevation angle (Ω) different from 0°, wherein the second transmission characteristic (Sx2) of the second transmitting antenna (Tx2) oriented along the second main radiation direction (HSx2) has a zero point (N) at a predetermined zero value angle (13), and wherein the zero point (N) is generated at the predetermined zero value angle (13) by activating multiple transmitting antenna elements of the second transmitting antenna with different phases, characterized in that the object (O1, O2) enters the zero point (N) by the motor vehicle (1) with the radar sensor device moving towards the object (O1, O2) and the object (O1, O2) passing from the transmission characteristic (Sx2) of the second transmitting antenna (Tx2) into the zero point (N) in this case at a specific distance in relation to the motor vehicle (1), which is dependent on the elevation angle of the object (O1, O2), wherein the passing of the object (O1, O2) is determined on the basis of a drop in the signal amplitude in the received signal, and in that the control device (3) is designed for the purpose of determining an elevation angle of the object (O1, O2) upon entry of the object (O1, O2) into the zero point (N) on the basis of the received signal received by at least one of the receiving antennas (Rx1, Rx2, Rx3, Rx4), the determined distance in relation to the motor vehicle (1) and the predetermined zero value angle (13).

2. Radar sensor device (4) according to Claim 1, characterized in that azimuth angles (Ψ) of the respective main radiation directions (HDx1, HDx2) of the reception characteristics (Dx1, Dx2) of the at least two receiving antennas (Rx1, Rx2) are formed identically.

3. Radar sensor device (4) according to Claim 1 or 2, characterized in that a first main radiation direction (HSx1) of a first transmission characteristic (Sx1) of a first transmitting antenna (Tx1) has a first elevation angle (Ω) of 0° with respect to a reference axis oriented parallel to a roadway (16) of the motor vehicle (1) and a second main radiation direction (HSx2) of a second transmission characteristic (Sx2) of a second transmitting antenna (Tx2) has a respective second elevation angle (Ω) different from 0°.

4. Radar sensor device (4) according to one of the preceding claims, characterized in that a vertical aperture angle of the second reception characteristic (Dx2) is formed so as to be larger than a vertical aperture angle of the first reception characteristic (Dx1).

5. Radar sensor device (4) according to one of the preceding claims, characterized in that an elevation angle difference between the main radiation directions (HDx1, HDx2) of the first and the second reception characteristics (Dx1, Dx2) and / or a vertical aperture angle of the second reception characteristic (Dx2) with respect to a vertical aperture angle of the first reception characteristic (Dx1) is formed such that a received signal received by the second receiving antenna (Rx2) has at most an attenuation (12) of 6 dB in relation to a received signal received by the first receiving antenna (Rx1).

6. Radar sensor device (4) according to one of the preceding claims, characterized in that the antenna configuration (8) has a third and a fourth receiving antenna (Rx3, Rx4), wherein a third and a fourth main radiation direction (HDx3, HDx4) of reception characteristics (Dx3, Dx4) of the third and fourth receiving antennas (Rx3, Rx4) have the first elevation angle (Ω), and wherein the azimuth angles (Ψ) of the main radiation directions (HDx1, HDx2, HDx3, HDx4) of all reception characteristics (Dx1, Dx2, Dx3, Dx4) and horizontal aperture angles of all reception characteristics (Dx1, Dx2, Dx3, Dx4) are formed identically.

7. Radar sensor device (4) according to one of the preceding claims, characterized in that the antenna configuration (8) has a third transmitting antenna (Tx3), wherein a third main radiation direction (HSx3) of a third transmission characteristic (Sx3) has the first elevation angle (Ω), an azimuth angle (Ψ) of the second main radiation direction (HSx2) of the second transmitting antenna (Tx2) is formed lying between the azimuth angles (Ψ) of the first and the third main radiation directions (HSx1, HSx3), and wherein a horizontal aperture angle of the second transmission characteristic (Sx2) is greater than a respective horizontal aperture angle of the first transmission characteristic (Sx1) and the third transmission characteristic (Sx3).

8. Radar sensor device (4) according to Claim 7, characterized in that the elevation angle of the object (O1, O2) is detected by an amplitude comparison of the reflected transmitted signal of the second transmitting antenna (Tx2) and of the reflected transmitted signal of the third transmitting antenna (Tx3), which has no zero point.

9. Radar sensor device (4) according to one of the preceding claims, characterized in that the second main radiation direction (HSx2) of the second transmission characteristic (Sx2) of the second transmitting antenna (Tx2) is oriented diagonally downwards in the direction of a roadway (16) of the motor vehicle (1) and a control device (3) of the radar sensor device (4) is designed for the purpose of recognizing a blocking of the radar sensor device (4) on the basis of an extension (21) and / or continuity of a detection point distribution (19) in a transmitted signal, which is emitted by the second transmitting antenna (Tx2), reflected on the roadway (16), and received by at least one of the receiving antennas (Rx1, Rx2, Rx3, Rx4) as a received signal.

10. Radar sensor device (4) according to Claim 9, characterized in that the control device (3) is designed for the purpose of recognizing a degree of the blocking of the radar sensor device (4) on the basis of the continuity and / or extension of the detection point distribution (19).

11. Radar sensor device (4) according to one of the preceding claims, characterized in that the second main radiation direction (HSx2) and the zero point (N) of the second transmission characteristic (Sx2) of the second transmitting antenna (Tx2) are oriented downwards in the direction of a roadway (16) of the motor vehicle (1) and a control device (3) of the radar sensor device (4) is designed for the purpose of recognizing a misalignment of the radar sensor device (4) on the basis of a transmitted signal emitted by the second transmitting antenna (Tx2), reflected on the roadway (16), and received by at least one of the receiving antennas (Rx1, Rx2, Rx3, Rx4) as a received signal if a deviation between a distance value (15) of the zero point (N) from the motor vehicle (1) detected on the basis of the received signal and a predetermined reference value exceeds a predetermined threshold value.

12. Radar sensor device (4) according to one of the preceding claims, characterized in that the elevation angle of the object (O1, O2) is detected by an amplitude comparison of the reflected transmitted signal of the second transmitting antenna (Tx2) and of the reflected transmitted signal of the first transmitting antenna (Tx1), which has no zero point.

13. Driver assistance system (2) for a motor vehicle (1) comprising at least one radar sensor device (4) according to one of the preceding claims.

14. Motor vehicle (1) comprising a driver assistance system (2) according to Claim 14.

15. Method for recognizing objects (O1, O2) in a surrounding region (6) of a motor vehicle (1), in which transmitted signals are emitted by at least two transmitting antennas (Tx1, Tx2), wherein respective main radiation directions (HSx1, HSx2) of transmission characteristics (Sx1, Sx2) of the at least two transmitting antennas (Tx1, Tx2) have different elevation angles (Ω) and different azimuth angles (Ψ), wherein the transmitted signals reflected in the surrounding region (6) are received as received signals by at least two receiving antennas (Rx1, Rx2) separate from the transmitting antennas (Tx1, Tx2), wherein respective main radiation directions (HDx1, HDx2) of reception characteristics (Dx1, Dx2) of the at least two receiving antennas (Rx1, Rx2) have different elevation angles (Ω), wherein a first main radiation direction (HDx1) of a first reception characteristic (Dx1) of a first receiving antenna (Rx1) has a first elevation angle (Ω) of 0° with respect to a reference axis oriented parallel to a roadway (16) of the motor vehicle (1) and a second main radiation direction (HDx2) of a second reception characteristic (Dx2) of a second receiving antenna (Rx2) has a respective second elevation angle (Ω) different from 0°, wherein the second transmission characteristic (Sx2) of the second transmitting antenna (Tx2) oriented along the second main radiation direction (HSx2) has a zero point (N) at a predetermined zero value angle (13), and wherein the zero point (N) is generated at the predetermined zero value angle (13) by activating multiple transmitting antenna elements of the second transmitting antenna with different phases, characterized in that the object (O1, O2) enters the zero point (N) by the motor vehicle (1) with the radar sensor device moving towards the object (O1, O2) and the object (O1, O2) passing from the transmission characteristic (Sx2) of the second transmitting antenna (Tx2) into the zero point (N) in this case at a specific distance in relation to the motor vehicle (1), which is dependent on the elevation angle of the object (O1, O2), wherein the passing of the object (O1, O2) is determined on the basis of a drop in the signal amplitude in the received signal, and in that an elevation angle of the object (O1, O2) to determine upon entry of the object (O1, O2) into the zero point (N) on the basis of the received signal received by at least one of the receiving antennas (Rx1, Rx2, Rx3, Rx4), the determined distance in relation to the motor vehicle (1) and the predetermined zero value angle (13).