RADAR SENSOR, RADAR SENSOR SYSTEM, AND METHOD FOR DETERMINING THE POSITION OF AN OBJECT USING HORIZONTAL AND VERTICAL DIGITAL BEAM FORMATION FOR MEASURING POINT-REFLECTIVE AND SURFACE-REFLECTIVE OBJECTS

Abstract

A radar sensor for a vehicle includes a control unit and an antenna array. The radar sensor is configured to perform a three-dimensional scan to determine a vertical and a horizontal position of an object in order to assist with distinguishing the geometrical nature of the object.

Claims

1. A radar sensor for a vehicle, comprising: a control unit; and an antenna array, wherein the radar sensor is configured to perform a three-dimensional scan to determine a vertical and horizontal position of an object in order to assist with distinguishing the geometrical nature of the object.

2. The radar sensor of claim 1, wherein the antenna array comprises at least one antenna row of individual antenna transmitters and at least one antenna row of individual antenna receivers.

3. The radar sensor of claim 1, wherein the control unit performs the three-dimensional scan with the antenna array according to a digital beam formation.

4. The radar sensor of claim 3, wherein the three-dimensional scan comprises a horizontal scan and a vertical scan, and the control unit comprises a transmitting/receiving device for performing the horizontal scan and a transmitting/receiving device for performing the vertical scan.

5. The radar sensor of claim 4, wherein the transmitting/receiving device for performing the horizontal scan is associated with at least one antenna row of individual antenna transmitters and with at least one antenna row of individual antenna receivers from the antenna array in order to form a fan-shaped beam.

6. The radar sensor of claim 4, wherein the transmitting/receiving device for performing the vertical scan is associated with at least one antenna transmitter of the antenna array with a widely radiating opening angle.

7. The radar sensor of claim 4, wherein the transmitting/receiving device for performing the horizontal scan and the transmitting/receiving device for performing the vertical scan each comprise a digital beam formation in order to swivel the beam horizontally and/or vertically.

8. The radar sensor of claim 4, wherein the horizontal scan and the vertical scan are performed sequentially in time.

9. The radar sensor of claim 2, wherein the at least one antenna row of individual antenna transmitters and the at least one antenna row of individual antenna receivers are arranged orthogonally to one another, and the multi-dimensional scan being is a two-dimensional scan.

10. The radar sensor of claim 9, wherein the control unit is configured to swivel the beam in the vertical as well as in the horizontal direction according to the digital beam formation.

11. The radar sensor of claim 2, wherein the control unit virtually enlarges the antenna array according to the digital beam formation and forming a virtual array of antenna receivers.

12. The radar sensor of claim 2, wherein the control unit comprises two signal processing units.

13. A radar sensor system for a vehicle, comprising: at least-two radar sensors according to claim 1, the scanned fields of vision of the at least two radar sensors overlapping in order to distinguish a geometrical nature of the object.

14. The radar sensor system of claim 13, wherein the radar sensor system is configured to distinguish between punctiform and flat objects.

15. The radar sensor of claim 14, wherein the at least two radar sensors are fitted tilting in relation to a side of the vehicle in order to optimally cover the opening range of the doors of the vehicle.

16. The use of a radar sensor system of claim 13 for monitoring a door space of a vehicle.

17. The use of the radar sensor system of claim 13 to assist with the parking of the vehicle.

18. A method for determining a position of an object using a radar sensor system of claim 13, comprising: transmitting and receiving signals using antennas with an antenna beam in the form of a fan in a vertical direction; combining the received signals by digital beam formation to form a number of bundled antenna beams in a horizontal direction; transmitting and receiving signals with wide antenna beams in the vertical and the horizontal direction, the antennas being arranged orthogonally to the antennas with a fan-shaped beam; combining the received signals from the wide antenna beams using digital beam formation to form a number of bundled antenna beams in the vertical direction; and displaying a horizontal and a vertical position of the object.

19. A method for determining a position of an object using a radar sensor system of claim 13, comprising: sequentially transmitting signals with a row of transmitters, and simultaneously receiving the beams reflected on objects with a row of receivers; combining the received signals using two-dimensional digital beam formation to form a number of bundled antenna beams in a horizontal and a vertical direction; and displaying a horizontal and a vertical position of the object.

Description

[0033] Advantageous configurations are illustrated by the following figures.

[0034] FIG. 1 shows the sensor arrangement on the vehicle with a horizontal field of vision for monitoring the opening range of the doors. The sensors are each fitted tilted by approx. 30 degrees and have a field of vision of approx. 110 degrees. At least 2 sensors are to be fitted on each side of the vehicle in order to cover the opening range of the doors optimally.

[0035] FIG. 2 shows the vertical field of vision of the sensors and the range of potential obstacles.

[0036] The arrangement of the sensors has been chosen so that on the one hand the opening range of the doors is covered maximally, and on the other hand so that punctiform reflectors can be distinguished from flat reflectors. Overlapping of the fields of vision of the sensors is required for this purpose.

[0037] With punctiform objects the door may open up to the object, whereas with flat obstacles, such as for example walls or vehicles parked adjacent, the door may only open to the potentially extended surface.

[0038] In FIG. 3 the detection of a punctiform reflector, and in FIG. 4 the detection of a planar, flat object is sketched.

[0039] The distance and the angle of the punctiform object is detected by both sensors. However, with flat, planar objects only reflections occur with a perpendicular angle of incidence. Neither of the sensors is capable of detecting one and the same reflection point. The radar sensors detect the radial distance and the angle in relation to the point of reflection. If one now forms the orthogonals to the beam directions of the individual sensors, the latter run approximately parallel with a surface target and cross with a point target. With the point target the doors may be opened up to its position, and with a surface target only up to the extended orthogonal. The doors are thus prevented from touching the wall when opened, even though the reflection point is further away than the collision point.

[0040] FIG. 5 shows the millimetre wave module of an individual radar sensor with an antenna arrangement. The sensor consists of a transmitting/receiving device (1) for the vertical scan and a transmitting/receiving device (2) for the horizontal scan. Every transmitting/receiving device consists of at least 4 receivers (3a, 3b) and one or two transmitters (4a, 4b). Since the required detection rate for the door monitoring is low in comparison to the measuring rate of the sensor, the sensor system can perform the vertical detection and the horizontal detection one after the other chronologically. This reduces costs because only one signal processing unit is required. Furthermore, the transmitting/receiving units are prevented from disrupting one another.

[0041] FIG. 6 shows the functional block diagram of the radar sensor. It consists of two highly integrated radar front ends, each with two transmitters and four receivers. Analogue to digital converters are already integrated into the receivers so that the latter can be connected directly to the signal processing unit—a multicore digital signal processor. The signal processor additionally performs the task of controlling the transmitting/receiving modules and operates the communication interface with the outside world, e.g. with the control electronics of the automatic door.

[0042] Preferably with the digital beam formation described in/1/with two transmitters and a number of receivers, the vertical and the horizontal angular position of the object to be detected is now determined and the distance from the object is measured. The individual transmitters of a pair of transmitters are operated one after the other chronologically here. The bringing together of the information from the two detection processes corresponds to the detection with just one transmitter and reception with a virtual array (3a′, 3b′) which is twice as great as the real array. The angle measuring accuracy can thus be increased by a factor of 2. If this is not required, the detection can also be operated with just one transmitter.

[0043] FIG. 7 shows the time diagram and the modulation form of an individual transmitting/receiving unit.

[0044] Here the frequency of the two transmitters is modulated alternately, linearly and in the form of saw teeth. This cycle is repeated n times. The distance from the object is determined from the sets of data of the individual modulation ramps with the aid of a Fast Fourier Transform (FFT). Afterwards these sets of data are arranged to form a spectrogram and a second FFT is calculated by means of the columns of the spectrogram matrix. The line position of this so-called range-Doppler matrix corresponds to the speed of the object, and the column position corresponds to the radial distance. The modulation frequency fm is greater than the maximum Doppler frequency that occurs, and so an independent and clear distance and speed measurement can be taken.

[0045] Horizontal Scan:

[0046] In order to cover the field of vision illustrated in FIGS. 1 and 2 an antenna line has been chosen which has the vertical diagram shown in FIG. 8. The arrangement and dimensioning of the individual emitter elements of the antenna line has not been optimised here to the maximum beam bundling as is otherwise normal, but is designed so that an upwardly directed fan-shaped beam is formed. This fan-shaped beam ensures that reflections of objects which are suppressed when they lie beneath the door sill and the sensor can also still detect objects with high vertical angles. The gain of this type of antenna line corresponds approximately to only that of an individual emitter. However, the distance from the objects is so small that the radar sensor is still sufficiently sensitive.

[0047] The horizontal diagram of this antenna line is illustrated in FIG. 9. It has a very large 3 dB beam width in order to illuminate the required wide range of vision of 110°. After the digital beam formation the array diagram shown in FIG. 10 is produced which can be swivelled by up to +50° without so-called grating lobes being produced which could lead to dummy targets.

[0048] Vertical Scan:

[0049] Here, it is not antenna lines, but rather just a single emitter element—a so-called microstrip patch emitter—that is used. This emitter has a large opening angle in both the vertical and the horizontal (see FIG. 11). The digital beam scanning is restricted here to the angle range of-70° to 0°. At −70° dummy targets occur in the opposite direction. However, these would lie physically beneath the surface of the road, and so can be eliminated by a simple plausibility test. Up to a swivel angle of −60° the detection is free from grating lobes, and so from dummy targets.

[0050] The door opening range is therefore monitored two-dimensionally by the alternately horizontal and vertical scan, and so protruding obstacles such as loading ramps, handrails or exterior mirrors of adjacent vehicles can also be recognised as obstacles.

[0051] Two-Dimensional Scan:

[0052] An alternative to a radar sensor with horizontal and vertical scan is a radar sensor with a two-dimensional scan with which a high bundling beam can be controlled in two spatial directions. FIG. 12 shows the millimetre wave module with two transmitting/receiving modules which make available 4 transmitters and 8 receivers. Here the transmitting antennas are arranged in a row orthogonal to the row of receiving antennas. The transmitting antennas should have the same polarisation direction here as the receiving antenna in order to guarantee the maximum system sensitivity. When the antennas are fed on the same level, as can be seen for example in FIG. 5, with the necessary spacing of the transmitting/emitting elements a line run feeding the emitting elements would not be possible. In order to implement this the emitter elements have been tilted by 45° on the transmitter as well as on the receiver.

[0053] As an extension to the know method described, for example, in/1/, one can therefore generate the virtual reception array that is shown so that an array of 4×8 individual emitters is available for the signal processing. Within the framework of the signal evaluation the phase and the amplitude of each of these individual emitters can be regulated so that beam scanning is possible in the vertical as well as in the horizontal direction.

[0054] FIG. 13 shows the controllable diagram of the array with a 3 dB beam width of 16 degrees in the horizontal and 29 degrees in the vertical.