Radar system, antenna array for a radar system, vehicle equipped with at least one radar system, and method for operating at least one radar system

Abstract

To provide a radar system for monitoring an object for at least one monitor region, an antenna array, a vehicle, and a method for operating the radar system.SOLUTION: A radar system has a plurality of transmission antennas 26 which can be controlled by using a transmission signal and can be used to send a target radar signal to at least one monitor region. The radar system has a plurality of reception antennas 28 for receiving an echo of a sent radar signal and converting the echo into its corresponding reception signal. The respective phase centers 32 of at least two adjacent reception antennas 28 are arranged at base intervals 40. The respective phase centers 32 of at least two adjacent reception antennas 28 are arranged at receiver vertical intervals 48a, 48b, and 48c larger than the base intervals 40.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention provides a radar system for monitoring at least one surveillance area for objects, comprising: a plurality of transmit antennas controllable with respective transmit signals and operable to transmit radar signals of interest into at least one monitored area; a plurality of receive antennas operable to receive echoes of the transmitted radar signal and convert the echoes into corresponding receive signals; The present invention relates to a radar system comprising at least one control and evaluation device connected to a transmitting antenna and a receiving antenna, which can be used to generate a transmission signal for controlling the transmitting antenna, and which can be used to ascertain from the received signal object information relating to an object detected using the radar signal.

[0002] The present invention further provides an antenna array for a radar system monitoring at least one surveillance area for objects, comprising: a plurality of transmit antennas controllable with respective transmit signals and operable to transmit radar signals of interest; The present invention relates to an antenna array comprising a plurality of receive antennas that can be used to receive echoes of a transmitted radar signal and convert the echoes into corresponding received signals.

[0003] The present invention also provides a vehicle comprising at least one radar system for monitoring at least one surveillance area for objects, the vehicle comprising: At least one radar system a plurality of transmit antennas controllable with respective transmit signals and operable to transmit radar signals of interest into at least one monitored area; a plurality of receive antennas operable to receive echoes of the transmitted radar signal and convert the echoes into corresponding receive signals; and at least one control and evaluation device connected to the transmitting antenna and the receiving antenna, which can be used to generate a transmission signal for controlling the transmitting antenna, and which can be used to ascertain from the received signal object information relating to an object detected using the radar signal.

[0004] The present invention further provides a method of operating a radar system adapted to monitor at least one surveillance area for an object, comprising: controlling a plurality of transmit antennas using the transmit signal and transmitting applicable radar signals into the monitored area; receiving echoes of the transmitted radar signals using a plurality of receiving antennas, converting the echoes into corresponding received signals, processing the received signals using signal processing, and ascertaining object information from the received signals regarding objects within the monitored area; The present invention relates to a method comprising:

[0005] [Prior art document] German Patent Application No. DE 10 2018 118 238 A1 discloses a method for operating a radar system and a radar system. The method includes using at least two transmitting antennas spaced apart from one another to transmit a transmission signal into a monitored area. If necessary, at least one receiving array element is used to receive an echo signal reflected by at least one object present in the monitored area. Information about at least one object is determined from the echo signal. The radar system can be operated in either a distance operation mode, in which the at least two transmitting antenna elements are used to simultaneously transmit the same transmission signal, and the distance and / or velocity of at least one object relative to the radar system are determined from the corresponding echo signal, or a directional operation mode, in which the at least two transmitting antenna elements are used to transmit distinct transmission signals, and the distinct echo signals are assigned to the transmitting antenna elements, and at least one directional component of the object is determined.

[0006] The invention is based on the object of designing a radar system, an antenna array, a vehicle and a method of the kind mentioned at the beginning, in which the performance of the radar system in terms of its detection range and angular resolution for direction determination is improved. DISCLOSURE OF THE INVENTION

[0007] According to the invention, this object is achieved by providing for a radar system: The phase centers of at least four of the receive antennas are positioned on an imaginary receiver longitudinal axis, and the phase centers of at least two adjacent receive antennas are positioned at a base interval from each other, and the phase centers of at least two adjacent receiving antennas are spaced apart from each other at a receiver longitudinal spacing greater than the base spacing; This is achieved by:

[0008] According to the present invention, four receive antennas are arranged next to each other along a virtual receiver longitudinal axis, where at least two receive antennas are arranged at a base spacing, which allows the receive antennas to be used for unambiguous direction determination. At least two receive antennas are arranged at a larger spacing, which allows the receive antenna configuration to be larger overall, which allows the aperture of the radar system to be larger.

[0009] The receive antenna configuration of the present invention can be employed to operate a radar system in both a directional operation mode, in which the receive antennas are controlled using different receive signals, and a range operation mode, in which the receive antennas are controlled using the same receive signal.

[0010] According to one advantageous embodiment, at least one receiver longitudinal spacing may be an integer multiple of the base spacing, in particular plus or minus a tolerance, thereby increasing the spread of the receive antenna configuration in the direction of the receiver longitudinal axis, thereby facilitating a correspondingly large virtual receive antenna array formed from the transmit and receive configurations in the direction of the directional operation mode of the radar system.

[0011] According to a further advantageous embodiment, the phase centers of the two receive antennas located outside the receiver longitudinal axis may be arranged at a base interval, thereby realizing a corresponding virtual receive antenna array that facilitates better angular resolution in the directional steering mode of the radar system.

[0012] According to a further advantageous embodiment, the phase centers of at least two adjacent receiving antennas are arranged on the same side of the phase centers of the two receiving antennas arranged at the base interval; The receiver longitudinal spacing between the phase center of the receiving antenna closest to the two receiving antennas arranged at the base interval and the phase center of the closest of the two receiving antennas arranged at the base interval may be smaller than the receiver longitudinal spacing between the phase center of the receiving antenna closest to the two receiving antennas arranged at the base interval and the phase center of the receiving antenna farther away from the two receiving antennas arranged at the base interval, or The longitudinal receiver spacing between the phase center of the receive antenna closest to the two receive antennas arranged at the base interval and the phase center of the two receive antennas closest to the two receive antennas arranged at the base interval may be larger than the longitudinal receiver spacing between the phase center of the receive antenna closest to the two receive antennas arranged at the base interval and the phase center of the receive antenna farther away from the two receive antennas arranged at the base interval, thereby realizing a virtual receive antenna array having both a large aperture and large angular resolution in the directional operation mode of the radar system.

[0013] If the receiver longitudinal spacing of the closest receive antennas is smaller than the receiver longitudinal spacing of the spaced apart receive antennas, the receive antenna configuration can be more compact.

[0014] In this case, the base interval and the two longitudinal intervals may advantageously be arranged according to the representation of the Golomb ruler.

[0015] If the receiver longitudinal spacing of the closest receive antennas is greater than the receiver longitudinal spacing of the spaced apart receive antennas, a corresponding expanded virtual receive antenna array can be realized in the pointing mode of the radar system, facilitating a correspondingly larger angular resolution, which in turn can facilitate a larger aperture in the range mode of the radar system.

[0016] According to a further advantageous embodiment, the quotient of the larger of the two longitudinal receiver spacings and the smaller of the two longitudinal receiver spacings between three adjacent receive antennas may advantageously be 1.5 or an integer multiple of 1.5, which may improve the clarity of the angle measurement.

[0017] The quotient of the larger of the two receiver longitudinal spacings and the smaller of the two receiver longitudinal spacings between three adjacent receive antennas may advantageously be two times 1.5, or three.

[0018] According to a further advantageous embodiment, the base spacing can correspond to half the wavelength of the radar signal transmitted by the transmitting antenna, in particular plus or minus a tolerance, thereby enabling distinctly directed radar signals at the transmitter in the directional operation mode of the radar system, and also enabling unambiguous angle measurements in the directional operation mode.

[0019] At least one transmitting antenna may advantageously comprise multiple antenna elements, which may improve the transmission characteristics of the at least one transmitting antenna. Alternatively or additionally, at least one receiving antenna may advantageously comprise multiple antenna elements, which may improve the reception characteristics of the at least one receiving antenna.

[0020] The phase center of the transmitting antenna may be preferably located in the plane of the transmitting antenna, which makes it easier to define the position of the phase center and therefore allows for more accurate radar measurements. The main beam direction of the transmitting antenna may preferably run perpendicular to the plane of the transmitting antenna, which makes it easier to define the main beam direction.

[0021] Alternatively or additionally, the phase center of the transmitting antenna may advantageously be located in the plane of the receiving antenna, which makes it easier to define the position of the phase center and therefore more accurate radar measurements can be made. The main receiving direction of the receiving antenna may advantageously run perpendicular to the plane of the receiving antenna, which makes it easier to define the main receiving direction.

[0022] Alternatively or additionally, the phase centre of the transmit antenna and the phase centre of the receive antenna may advantageously be located in a common antenna plane, which allows the position of the phase centre to be located more accurately.

[0023] At least some of the transmit antennas may advantageously be realized as antenna arrays. This allows the transmit antennas to be manufactured and assembled together.

[0024] Alternatively or additionally, at least some of the receive antennas may advantageously be realized as an antenna array, so that the receive antennas can be manufactured and assembled together.

[0025] Alternatively or additionally, at least some of the transmit antennas and at least some of the receive antennas may advantageously be realized as a common antenna array, whereby the transmit and receive antennas can be manufactured and assembled together.

[0026] Advantageously, the respective phase centers of at least two adjacent transmitting antennas may be arranged on a virtual transmitter longitudinal axis, and the phase center of at least one further transmitting antenna may be arranged at a transmitter lateral distance from the transmitter longitudinal axis.

[0027] A virtual transmitter horizontal axis running perpendicular to the transmitter vertical axis through the phase center of the at least one further transmitting antenna may advantageously be located at a base distance from said virtual transmitter horizontal axis running perpendicular to the transmitter vertical axis through the phase center of one of the at least two transmitting antennas on the transmitter vertical axis.

[0028] The transmitter longitudinal spacing between each virtual transmitter longitudinal axis of at least two adjacent transmitting antennas on the transmitter longitudinal axis may advantageously be greater than the base spacing.

[0029] The at least two transmit antennas may be advantageously arranged along the transmitter longitudinal axis, the at least one further transmit antenna may be arranged adjacent to the transmitter longitudinal axis, and the at least one transmit antenna arranged adjacent to the transmitter longitudinal axis may be arranged adjacent to a target transmitter horizontal axis of one of the at least two transmit antennas at a base spacing.

[0030] This advantageous transmit antenna configuration can be operated in both a direction finding mode, in which the transmit antennas are controllable using different transmit signals, and in a range operation mode, in which the transmit antennas are controllable using the same transmit signal.

[0031] The longitudinal transmitter spacing may advantageously be an integer multiple of the base spacing, in particular plus or minus a tolerance.

[0032] Alternatively or additionally, the transmitter lateral spacing may advantageously be greater than the base spacing.

[0033] Alternatively or additionally, the lateral transmitter spacing may advantageously be smaller than the longitudinal transmitter spacing.

[0034] This allows a particularly compact transmit antenna configuration to be achieved.

[0035] The transmitter horizontal axis of the at least one further transmitting antenna may advantageously be arranged between the transmitter horizontal axes of at least two transmitting antennas adjacent on the transmitter vertical axis, thereby allowing a more compact realization of the transmitting antenna arrangement.

[0036] At least some of the transmit antennas are advantageously at least temporarily controllable with the same transmit signal.

[0037] Alternatively or additionally, at least some of the transmit antennas are advantageously controllable, at least temporarily, with different transmit signals, such that each transmitted radar signal is at least temporarily distinguishable at the receive antenna.

[0038] Alternatively or additionally, at least some of the transmit antennas are switchably controllable using the same transmit signal or different transmit signals.

[0039] Controlling at least some of the transmit antennas, at least temporarily, with the same transmit signal allows the same radar signal to be emitted simultaneously from the target transmit antennas. Thus, the radar signals from each transmit antenna can be combined to form a common radar signal with greater signal strength, thereby increasing the detection range. A mode of operation of a radar system in which at least some of the transmit antennas are controlled with the same transmit signal can be referred to as a range operation mode.

[0040] At least two adjacent receive antennas may advantageously be operated using a beamforming scheme, in which adjacent transmit antennas, particularly those spaced at a base interval, can be used coherently so that multiple transmit channels each transmit the same radar signal with a defined phase offset.

[0041] The ability to distinguish radar signals allows corresponding echoes of received radar signals to be assigned to target transmit antennas using the receive antennas, thereby reducing the investment in transmit antennas for direction determination. A radar system operating mode in which at least two of the transmit antennas are controlled so that each transmitted radar signal is at least temporarily distinguishable at least at the receive antenna can be referred to as a directional operating mode.

[0042] At least two of the transmit antennas may advantageously be operated using a MIMO scheme, in which the transmit antennas transmit radar signals that are at least temporarily distinguishable at least at the receive antennas, which may improve the angular resolution for direction determination.

[0043] At least some of the transmit antennas are controllable in a switchable manner using the same or different transmit signals, so that the radar system can be switched between a direction operation mode and a range operation mode, and at least some of the transmit antennas are advantageously switchable automatically and / or as needed.

[0044] In the directional operation mode, a higher angular resolution is possible than in the range operation mode, and conversely, in the range operation mode, a wider detection range is possible than in the directional operation mode.

[0045] The radar system, in particular at least one control and evaluation device of the radar system, may advantageously comprise at least one switching means which may be used to switch the radar system between an operating mode in which at least some of the transmitting antennas are controllable using the same transmitting signal, in particular a range operation mode or a beamforming mode, and an operating mode in which at least some of the transmitting antennas are controllable using different transmitting signals, in particular a directional mode or a MIMO mode.

[0046] The special inventive combination of receive and transmit antenna configurations means that when the radar system is operated in a directional steering mode, in particular in MIMO mode, a virtual receive antenna array can be realized which combines a large aperture with a large angular resolution.

[0047] Radar systems may be used to ascertain object information, particularly the distance, direction, and / or velocity of an object, particularly an object target to the radar system, which is an area of ​​the object from which a radar signal is reflected, and which can be received as an echo using a receiving antenna.

[0048] Direction determination is the determination of the direction in which a target is located relative to a radar system, where direction may be specified as an angle relative to a reference axis of the radar system, in particular the main beam direction of the transmit antenna.

[0049] The longitudinal axis of the transmitter and / or the longitudinal axis of the receiver, as well as the main beam direction of the transmitting antenna, are preferably spatially oriented in the horizontal direction, so that a horizontally extending monitoring area can be monitored with angular resolution, which direction can be determined here as an azimuth angle.

[0050] The radar system may advantageously comprise means for controlling the transmitting antenna, in particular means for generating the transmitting signals. Furthermore, the radar system may comprise means for processing the receiving signals. The means for controlling and / or processing may be realized in the form of software and / or hardware using a common control and evaluation device. The control and evaluation device may comprise appropriate transmission channels for the transmitting signals and / or receiving channels for the receiving signals. The transmitting signals and / or receiving signals may be electrical signals, so that electronic means may be used for control and / or evaluation.

[0051] The invention may be used in radar systems for vehicles, in particular motor vehicles. The invention may advantageously be used in land vehicles, in particular cars, trucks, buses, motorbikes, etc., or in airplanes and / or ships. The invention may be used in vehicles that can be operated automatically or at least semi-automatically. However, the invention is not limited to use in vehicles. The invention may also be used in radar systems that operate stationary.

[0052] The radar system may advantageously be connected to or be part of at least one electronic control device of the vehicle, in particular a driver assistance system or a chassis control system and / or a driver information device and / or a parking assistance system and / or an attitude recognition system, etc., so that the vehicle can be operated automatically or semi-automatically.

[0053] Radar systems may be used to detect stationary or moving objects, in particular vehicles, people, animals, plants, obstacles, road irregularities, in particular potholes or stones, road boundaries, road signs, empty spaces, in particular parking spaces, precipitation, etc.

[0054] According to a further advantageous embodiment, the configuration of transmit and receive antennas is used in a directional steering mode of the radar system to realize a virtual receive antenna array in which at least two adjacent virtual receive array elements are arranged on at least one virtual array longitudinal axis, At least two adjacent virtual receive array elements may be positioned at a base spacing from each other; and / or At least two adjacent virtual receive array elements may be spaced apart at a distance greater than the base spacing; and / or At least two adjacent virtual receive array elements may be spaced apart at an interval corresponding to an integer multiple of the base spacing. Virtual receive antenna arrays spaced apart from one another at the base spacing may be used to achieve clear direction determination. In general, virtual receive antenna arrays spaced apart greater than the base spacing may be used to achieve larger virtual receive antenna arrays. Larger virtual receive antenna arrays may be used to achieve larger apertures. This generally allows the radar system to be used over a correspondingly larger angular range to clearly and more accurately determine the direction of a target object.

[0055] The inventive arrangement of transmit and receive antennas may be used to achieve a virtual receive antenna array comprising a large number of virtual receive antenna array elements by geometric convolution of the locations of the phase centers of the transmit and receive antennas.

[0056] According to a further advantageous embodiment, the virtual receive array elements in the virtual receive antenna may be arranged in a manner that is distributed across at least two virtual array longitudinal axes, At least two virtual receive array elements arranged on different array longitudinal axes may be arranged at the same height when viewed in the direction of the array longitudinal axis; and / or At least two virtual receive array elements arranged on different array longitudinal axes may be arranged in a manner that they are offset from each other when viewed in the direction of the array longitudinal axis; and / or At least two virtual receive array elements arranged on different array longitudinal axes may be arranged in a manner that they are offset from each other by a base spacing when viewed in the direction of the array longitudinal axis.

[0057] The configuration of the virtual receive antenna array elements on different array longitudinal axes allows the direction of the target object to be ascertained in two dimensions. The offset configuration of the virtual receive antenna array allows for better angular resolution to be achieved when determining the direction of the target object.

[0058] According to the present invention, The phase centers of at least four of the receive antennas are arranged on an imaginary receiver longitudinal axis, and the phase centers of at least two adjacent receive antennas are arranged at a base interval from each other, and The phase centers of at least two adjacent receiving antennas are arranged at a receiver longitudinal spacing greater than a base spacing. Thus, the object is further achieved for the antenna array.

[0059] According to the invention, this object is also achieved for a vehicle, in that the vehicle is equipped with at least one radar system according to the invention.

[0060] According to the present invention, a vehicle is equipped with at least one radar system capable of monitoring objects around the vehicle. Object information identified using the at least one radar system can be used in conjunction with a driver assistance system to control the operation of the vehicle, thereby allowing the vehicle to be operated automatically or semi-automatically.

[0061] According to the present invention, a range operation mode in which at least some of the transmit antennas are at least temporarily controlled using the same transmit signal; and switching between directional operation modes in which at least some of the transmit antennas are at least temporarily controlled using different transmit signals such that each received radar signal is at least temporarily distinguishable at the receive antenna; Thus, the present object is further achieved with respect to the method.

[0062] In accordance with the present invention, the radar system is operated alternately between a range operation mode to achieve a long detection range and a direction operation mode to increase the angular resolution for direction determination.

[0063] Discrimination in the directional steering mode allows reflected radar signals, or echoes, to be assigned to each transmitting antenna at the receiving antenna.

[0064] At least two transmit antennas may advantageously be used to transmit differently coded radar signals, so that the radar signals can be at least temporarily distinguished from one another at the receive antennas.

[0065] The transmitted signals may be advantageously coded relative to one another, in particular by phase modulation, to generate distinguishable radar signals, whereby at least temporal signal orthogonality may be achieved between the transmitted and received signals, whereby the radar signals and the corresponding echoes may be rendered distinct from one another.

[0066] The received signals may be advantageously processed in the receiver by suitable evaluation, in particular by means of a Fourier transform. The means for performing the evaluation may advantageously be realized in the form of software and / or hardware, in particular in at least one control and evaluation device.

[0067] Alternatively, the features and advantages disclosed in connection with the radar system of the present invention, the antenna array of the present invention, the vehicle of the present invention, the method of the present invention, and their respective advantageous configurations may be applied in a corresponding manner to each other, and vice versa. Of course, individual features and advantages may also be combined with each other, and advantageous effects beyond the individual effects may also be obtained. [Brief explanation of the drawings]

[0068] Further advantages, features and details of the present invention will become apparent from the following description in which exemplary embodiments of the present invention are described in more detail with reference to the drawings. Those skilled in the art will conveniently consider the disclosed features individually in combination in the drawings, description and claims and combine them to form further meaningful combinations. Schematically, in the figures: [Figure 1] FIG. 1 shows a front view of a motor vehicle equipped with a driver assistance system and a radar system for monitoring a surveillance area ahead in the direction of movement of the motor vehicle. [Figure 2] FIG. 2 shows a plan view of the motor vehicle of FIG. [Figure 3] FIG. 3 shows a side view of the motor vehicle of FIGS. [Figure 4] FIG. 4 shows a front view of an antenna array of a radar system including a transmitting antenna and a receiving antenna according to a first exemplary embodiment that may be used in the motor vehicle of FIGS. [Figure 5] FIG. 5 shows the virtual receive antenna array realized with the antenna array of FIG. 4 when the radar system is operated in directional steering mode. [Figure 6] FIG. 6 shows a range / direction graph of the antenna array of FIG. 4, showing the detection range of the radar system as a function of direction when the radar system is operated in a range and direction operation mode. [Figure 7] FIG. 7 shows a received signal / direction graph for the antenna array of FIG. 4 with the radar system operated in a directional operation mode when a target object is detected. [Figure 8] FIG. 8 shows a received signal / direction graph with multiple measurement curves for the antenna array of FIG. 4, with the radar system operated in directional operation mode, when two target objects are detected. [Figure 9] FIG. 9 shows a received signal / direction graph with multiple measurement curves for the antenna array of FIG. 4, with the radar system operated in range operation mode, when the two target objects of FIG. 8 are detected. [Figure 10]FIG. 10 shows a front view of an array including transmit and receive antennas of a radar system according to a second exemplary embodiment that may be used in the motor vehicle of FIGS. 1-3. [Figure 11] FIG. 11 shows a virtual receive antenna array realized with the antenna array of FIG. 10 when the radar system is operated in directional steering mode. [Figure 12] FIG. 12 shows a range / direction graph of the antenna array of FIG. 10, showing the detection range as a function of direction when the radar system is operated in range and direction operation modes. [Figure 13] FIG. 13 shows a received signal / direction graph for the antenna array of FIG. 10 with the radar system operated in a directional steering mode when a target object is detected. [Figure 14] FIG. 14 shows a received signal / direction graph with multiple measurement curves for the antenna array of FIG. 10, with the radar system operated in directional operation mode, when two target objects are detected. [Figure 15] FIG. 15 shows a received signal / direction graph for a radar system with the antenna array of FIG. 10, when the radar system is operated in a range operation mode, when two target objects from FIG. 14 are detected.

[0069] In the drawings, like elements are marked with like reference numerals.

[0070] Figure 1 shows a front view of a motor vehicle 10 in the form of an automobile. Figure 2 shows a plan view of the motor vehicle 10. In Figure 3, the motor vehicle 10 is shown in a side view.

[0071] The motor vehicle 10 includes a radar system 12. By way of example, the radar system 12 is located on the front fender of the motor vehicle 10. The radar system 12 may be used to monitor a surveillance area 14 ahead of the motor vehicle 10 for an object 18 in a direction of travel 16. The radar system 12 may also be differently located and oriented at other locations on the motor vehicle 10. The radar system 12 may be used to ascertain object information, e.g., in the form of a distance r and a direction, e.g., an azimuth angle φ and an elevation angle Θ, of the object target of the object 18 relative to the motor vehicle 10 or the radar system 12. Optionally, the speed of the object target relative to the motor vehicle 10 may also be ascertained. The object target of the object 18 is a part of the object 18 from which a radar beam may be reflected as an echo.

[0072] The object 18 may be a stationary or moving object, in particular a vehicle, a person, an animal, a plant, an obstacle, in particular a pothole or a stone road irregularity, a road boundary, a road sign, an empty space in particular a parking space, precipitation, etc.

[0073] For better orientation, Cartesian xyz coordinate axes of interest are shown in Figures 1-5, 10, and 11. In the exemplary embodiment shown, the x-axis extends in the direction of the longitudinal vehicle axis of motor vehicle 10, the y-axis extends along the lateral vehicle axis, and the z-axis extends upward, spatially perpendicular to the xy plane. When motor vehicle 10 is operating on a level road, the x-axis and y-axis extend spatially horizontally, and the z-axis extends spatially vertically.

[0074] The radar system 12 is configured as a frequency-modulated continuous wave radar, also known among experts as FMCW (Frequency Modulated Continuous Wave) radar. The radar system 12 may be used to detect an object 18 located at a large distance r with a large angular resolution in the relationship between the azimuth angle φ and the elevation angle Θ.

[0075] The radar system 12 is connected to a driver assistance system 20. The driver assistance system 20 may be used to operate the motor vehicle 10 automatically or semi-automatically.

[0076] The radar system 12 comprises an antenna array 22 and a control and evaluation unit 24. Figure 4 shows the antenna array 22 according to a first exemplary embodiment, and Figure 10 shows the antenna array according to a second exemplary embodiment.

[0077] The radar system 12 associated with the antenna array 22 according to the first exemplary embodiment is described below, first in connection with FIGS.

[0078] By way of example, the antenna array 22 comprises three transmit antennas 26 and four receive antennas 28. By way of example, the receive antennas 28 are spatially positioned below the transmit antennas 26. However, the receive antennas 28 may also be positioned above, next to, or, in at least some cases, at the same height as, for example, the transmit antennas 26.

[0079] Each transmit antenna 26 is connected to a corresponding transmit channel, which may be used to control each transmit antenna 26 with an appropriate electrical transmit signal. Accordingly, each receive antenna 28 is also connected to a corresponding receive channel, which may be used to transmit an electrical receive signal from the receive antenna 28. The transmit and receive channels may be integrated, for example, in the control and evaluation device 24.

[0080] The transmitting antenna 26 may be used to transmit a radar signal 30 of interest using an electrical transmission signal for control purposes.

[0081] The position of each transmit antenna 26 is defined by a respective phase center 32 .

[0082] The phase centers 32 of two of the transmit antennas 26 are positioned adjacent to each other on an imaginary longitudinal transmitter axis 34. By way of example, the longitudinal transmitter axis 34 extends parallel to the y-axis.

[0083] 4, the phase center 32 of the third transmitting antenna 26 is located adjacent to and below the transmitter longitudinal axis 34. The third transmitting antenna 26 is located at a transmitter lateral spacing 36 from the transmitter longitudinal axis 34.

[0084] In each case, a corresponding imaginary transmitter horizontal axis 38 runs through the phase centers of the three transmit antennas 26. The transmitter horizontal axis 38 extends perpendicular to the transmitter vertical axis 34, illustratively parallel to the z-axis.

[0085] The horizontal transmitter axis 38 of each transmitting antenna 26 is disposed between the horizontal transmitter axes 38 of two adjacent transmitting antennas 26 on the vertical transmitter axis 34 .

[0086] The transmitter horizontal axis 38 of each transmitting antenna 26 is positioned at a base spacing 40 from the transmitter horizontal axis 38 of the transmitting antenna 26 on the right side in FIG. 4. By way of example, the base spacing 40 corresponds to one-half the wavelength λ of the radar signal 30 transmitted using the transmitting antenna 26, optionally plus or minus a tolerance.

[0087] The transmitter longitudinal spacing 42 between each of the transmitter horizontal axes 38 of the two transmitting antennas 26 on the transmitter longitudinal axis 34 is three times the base spacing 40, optionally plus or minus a tolerance. The transmitter horizontal spacing 36 is less than the transmitter longitudinal spacing 42 and greater than the base spacing 40.

[0088] Additionally, the antenna array 22 illustratively includes four receive antennas 28. The receive antennas 28 may be used to receive echoes 44 of the transmitted radar signal 30 and convert the echoes into corresponding electrical receive signals.

[0089] By way of example, the phase center 32 of the transmitting antenna 26 and the phase center 32 of the receiving antenna 28 are located in a common antenna plane. By way of example, the antenna plane extends parallel to the y-z plane. The main beam direction of the transmitting antenna 26, by way of example, runs perpendicular to the antenna plane, i.e., parallel to the vehicle longitudinal axis or parallel to the x-axis. The main receiving direction of the receiving antenna 28, by way of example, also runs perpendicular to the antenna plane.

[0090] Each phase center 32 of the receive antennas 28 is located on an imaginary receiver longitudinal axis 46. The receiver longitudinal axis 46 runs parallel to the transmitter longitudinal axis 34.

[0091] 4, the phase centers 32 of the first and second receive antennas 28 are positioned at a base spacing 40. The two receive antennas 28 positioned at a base spacing may be used to provide unambiguous direction determination of an object target.

[0092] The phase centers 32 of the third and fourth receive antennas 28 are located on the same side of the phase centers 32 of the two receive antennas 28 that are spaced apart by the base spacing 40 .

[0093] 4 is located at a first receiver longitudinal spacing 48a from the phase center 32 of the third receiver antenna 28 from the left. The first receiver longitudinal spacing 48a is twice the base spacing 40, optionally plus or minus a tolerance.

[0094] The phase center 32 of the third receive antenna 28 from the left in Figure 4 is located at a second receiver longitudinal axis 48b from the phase center 32 of the fourth receive antenna 28 from the left. The second receiver longitudinal spacing 48b is six times the base spacing 40, optionally plus or minus a tolerance. The quotient of the second receiver longitudinal spacing 48b and the first receiver longitudinal spacing 48a is three.

[0095] As an example, the base spacing 40 and the two receiver longitudinal spacings 48a, 48b may be arranged according to the representation of the Golomb ruler.

[0096] The largest spacing between the two outer receive antennas, i.e., the first receive antenna 28 and the fourth receive antenna 28 from the left, is used to achieve a correspondingly large aperture of the radar system 12 in the direction of the azimuth angle φ.

[0097] The particular configuration of the phase centers 32 of the transmit antennas 26 and the receive antennas 28 allows a virtual receive antenna array 50, shown in Figure 5, to be realized in the directional steering mode of the radar system 12, which array combines a large aperture in the azimuth angle φ with large angular resolution. By way of example, the receive array elements 52 are achieved by a geometric convolution of the positions of the phase centers 32 of the transmit antennas 26 and the receive antennas 28.

[0098] The virtual receive antenna array 50 includes a total of 12 virtual receive antenna array elements 52. The receive array elements 52 are arranged in a distributed manner on a first virtual array longitudinal axis 54a and a second virtual array longitudinal axis 54b. The distributed arrangement of the receive array elements 52 on the array longitudinal axes 54a and 54b allows the direction of a target object to be ascertained in two spatial dimensions: the y-axis or azimuth angle φ, and the z-axis or elevation angle Θ. The receive array elements 52 are illustratively located in a common array plane. Illustratively, the array plane extends parallel to the y- and z-axes.

[0099] Six of the receive array elements 52 are arranged on a first virtual array vertical axis 54a.

[0100] 5, the first and second receive array elements 52, the third and fourth receive array elements 52, and the fifth and sixth receive array elements 52 are arranged on the first array vertical axis 54a at base spacing 40. The receive array elements 52 arranged at base spacing 40 can be used to achieve unambiguous direction determination.

[0101] 5, the second and third receive array elements 52, the fifth and sixth receive array elements 52, the sixth and seventh receive array elements 52, and the seventh and eighth receive array elements 52 are arranged on the first array vertical axis 54a at a first interval 56a from each other. The first interval 56a corresponds to twice the base interval 40.

[0102] The second spacing 56 b between the seventh and eighth receive antenna elements 52 corresponds to four times the base spacing 40 .

[0103] Four of the receive array elements 52 are arranged on a second virtual longitudinal array axis 54b, which runs parallel to the first longitudinal array axis 54a in the array plane. The two longitudinal array axes 54a and 54b extend parallel to the y-axis.

[0104] When viewed in the direction of the array vertical axes 54a and 54b, the first receive array element 52 on the second array vertical axis 54b is, for example, positioned at the same height as the third receive array element 52 on the first array vertical axis 54a when viewed from the left in Figure 5. When viewed in the direction of the array vertical axes 54a and 54b, the second receive array element 52 from the left on the second array vertical axis 54b is positioned at the same height as the fourth receive array element 52 on the first array vertical axis 54a.

[0105] When viewed in the direction of the array longitudinal axes 54a and 54b, the third receive array element 52 from the left in FIG. 5 on the second array longitudinal axis 54b is, for example, centered between the fifth and sixth receive array elements 52 on the first array longitudinal axis 54a, in each case, at the base spacing 40, i.e., offset from the element in question.

[0106] When viewed along the array longitudinal axes 54a and 54b, the fourth receive array element 52 from the left in FIG. 5 on the second array longitudinal axis 54b is positioned between and offset from the seventh and eighth receive array elements 52 on the first array longitudinal axis 54a by the base spacing 40.

[0107] The first and second receive array elements 52 on the second array vertical axis 54b, as viewed from the left in FIG. 5, are spaced apart by the base spacing 40 from each other.

[0108] The second and third receive array elements 52, as viewed from the left, on the second array vertical axis 54b are spaced apart from each other by a first spacing 56a that corresponds to twice the base spacing 40. The third and fourth receive array elements 52, as viewed from the left, on the second array vertical axis 54b are spaced apart from each other by a third spacing 56c that corresponds to six times the base spacing 40.

[0109] The aperture of the radar system 12 in the direction of the longitudinal axes 54a and 54b, i.e., the y-axis direction, is defined by the maximum width of the virtual receive antenna array 50. The maximum width of the virtual receive antenna array 50 in the direction of the array longitudinal axes 54a and 54b is defined by the spacing 56d between the two outer receive array elements 52 on the first array longitudinal axis 54a. The spacing 56d between the two outer array elements 52 corresponds to 12 times the base spacing 40.

[0110] The offset configuration of the receive array elements 52 on the two array longitudinal axes 54a and 54b allows for better angular resolution when determining the direction of a target object in both azimuth angle φ and elevation angle Θ.

[0111] The control and evaluation unit 24 is realized in the form of software and hardware. The control and evaluation unit 24 is connected to a transmitting antenna 26 and a receiving antenna 28. The control and evaluation unit 24 may be used to generate an electrical transmission signal for controlling the transmitting antenna 26. In addition, the control and evaluation unit 24 may be used to ascertain object information about the object 18 detected using the radar signal 30 from the electrical reception signal of the receiving antenna 28.

[0112] The radar system 12 is switchable between a range mode and a directional mode of operation. To this end, the transmit antennas 26 may be controllable in a switched manner using the same or different transmit signals. Accordingly, the receive antennas 28 are switchable between a range mode and a directional mode of operation.

[0113] The switching from the range operation mode to the directional operation mode may be automatic or performed as needed. The directional operation mode allows a higher angular resolution for direction determination than the range operation mode. Conversely, the range operation mode allows a larger detection range than the directional operation mode. The control and evaluation device 24 comprises switching means 58 that can switch the radar system 12 between the range operation mode and the directional operation mode.

[0114] In the range operation mode of the radar system 12, the transmit antennas 26 can be controlled using the same transmit signal. Controlling the transmit antennas 26 using the same transmit signal allows the target transmit antennas 26 to simultaneously emit the same radar signal 30. For this purpose, the transmit antennas 26 can be controlled using a so-called beamforming method. In this case, multiple transmit channels can be used coherently with adjacent transmit antennas 26 transmitting the same radar signal 30 with a defined phase offset. The signal strengths of the radar signals 30 from each transmit antenna 26 are added together to form a larger signal strength. This can increase the detection range.

[0115] The radar system 12 is used to continuously perform radar measurements to monitor the surveillance area 14 for objects 18. Each radar measurement has a range measurement sequence in which the radar system 12 is operated in a range operation mode and a direction measurement sequence in which the radar system 12 is operated in a direction operation mode. During a radar measurement, the radar system 12 switches from the range operation mode to the direction operation mode. Here, each radar measurement may begin with either a range measurement sequence or a direction measurement sequence.

[0116] As an example, the following text describes a radar measurement that begins with a range measurement sequence.

[0117] The range measurement sequence involves the control and evaluation device 24 being used to control the transmitting antennas 26 via each transmission channel using the same transmit signal. Each transmitting antenna 26 simultaneously emits the same radar signal 30. The signal strengths of each radar signal 30 are summed and transmitted into the surveillance area 14 with an increased detection range.

[0118] When the radar signal 30 strikes an object 18, the radar signal 30 is reflected by the corresponding object target. Echoes 44 of the reflected radar signal 30 are received using the receive antenna 28 and converted into respective receive signals.

[0119] The received signals are transmitted to a control and evaluation unit 24, which processes the signals, for example by means of a Fourier transform. Object information about the object 18, i.e., the range r, and the direction, i.e., the azimuth angle φ and the elevation angle Θ, and optionally the velocity of the detected target object relative to the radar system 12, is determined from the received signals.

[0120] The radar system 12 is then switched from the range operation mode to the direction operation mode, for example using the control and evaluation unit 24, and a direction measurement sequence is performed.

[0121] The direction finding sequence involves the control and evaluation device 24 being used to control the transmitting antennas 26 via each transmission channel with different transmit signals. The different transmit signals are coded relative to each other. The transmitting antennas 26 emit radar signals 30 that are appropriately coded relative to each other. The radar signals 30 are transmitted into the surveillance area 14.

[0122] When the distinguishable radar signal 30 strikes the object 18, the radar signal 30 is reflected by the target object 18. Echoes 44 of the reflected distinguishable radar signal 30 are received using the receive antenna 28 and converted into respective received signals.

[0123] The received signals are transmitted to a control and evaluation unit 24. The received signals are assigned to a transmitting antenna 26. This is possible because the radar signal 30 and the echoes 44 are distinguished. The assigned received signals are processed, for example by a Fourier transform. Object information about the object 18, i.e., the range r, and the direction, i.e., the azimuth angle φ and the elevation angle Θ, and optionally the velocity of the detected target object relative to the radar system 12, is determined from the received signals.

[0124] Generally, object information about an object target is ascertained at a larger detection range in a range measurement sequence than in a direction measurement sequence in radar measurements. Object information about an object target is ascertained at a shorter detection range in a direction measurement sequence than in a range measurement sequence, but at a higher angular resolution than in a range measurement sequence.

[0125] For comparison, Figure 6 shows a range / direction graph 60a (dashed line) of the radar system 12 in the range operation mode and a range / direction graph 60b (solid line) of the radar system 12 in the direction operation mode, where each range is recorded in azimuth angle φ. From Figure 6, it can be seen that the radar system 12 has a maximum detection range of approximately 250 m in the range operation mode. However, in the directional operation mode, the radar system 12 has a maximum detection range of only slightly less than 200 m. In contrast, in the azimuth angle φ direction, the radar system 12 has a larger field of view in the directional operation mode than in the range operation mode.

[0126] 7 shows a received signal / direction graph 62a from a direction measurement sequence in which a target object is detected at an azimuth angle φ of 0 degrees ahead of the motor vehicle 10. The sidelobe level is approximately 8 dB, which is sufficient to distinguish target objects with different reflectivities, for example, in that direction, i.e., in actual driving situations of the motor vehicle 10 for each azimuth angle φ.

[0127] 8 shows a family of curves associated with a received signal / direction graph 62b of a sequence of direction measurements in which two target objects having the same range r and the same speed relative to the radar system 12 are detected at an angular interval of approximately 11 degrees around an azimuth angle φ of 0 degrees in front of the motor vehicle 10. The curves in the family of received signal / direction graphs 62b correspond to different phase differences of the transmitted signals. The two target objects can be distinguished at all possible phase differences. The curves in the family of received signal / direction graphs 62b can be confirmed, for example, by so-called beamforming methods and / or so-called super-resolution methods and similar methods.

[0128] The received signal / direction graph for the range measurement sequence, which corresponds to the direction measurement sequence in Figure 8, is shown in Figure 9. The angular resolution based on the azimuth angle φ is about 11 degrees. The side lobe level in this case is about 3 dB, which is insufficient to distinguish between two target objects in the range operation mode.

[0129] 10 illustrates an antenna array 22 for a radar system 12 according to a second exemplary embodiment. FIG. 11 illustrates a virtual receive antenna array 50 that is part of the antenna array 22 of FIG.

[0130] Those elements that are similar to those of the first exemplary embodiment of Figures 4-11 are designated with the same reference numerals. The second exemplary embodiment differs from the first exemplary embodiment in that the phase center 32 of the second-from-the-left receive antenna 28 is positioned a receiver longitudinal spacing 48c from the phase center 32 of the third-from-the-left receive antenna 28. The receiver longitudinal spacing 48c corresponds to three times the base spacing 40, optionally plus or minus a tolerance.

[0131] The phase center 32 of the third receiving antenna 28 from the left in Figure 10 is spaced a receiver longitudinal spacing 48a from the phase center 32 of the fourth receiving antenna 28 from the left. The receiver longitudinal spacing 48a corresponds to twice the base spacing 40, optionally plus or minus the tolerance. The quotient of longitudinal spacing 48c and longitudinal spacing 48a is 1.5.

[0132] The virtual receive antenna array 50 according to the second exemplary embodiment of FIG. 11 differs from the virtual receive antenna array 50 according to the first exemplary embodiment of FIG. 5 in that the virtual receive antenna array 50 according to the second exemplary embodiment has only eleven receive antennas 28, only seven of which are located on the first array longitudinal axis 54a.

[0133] Unlike the first exemplary embodiment, in the second exemplary embodiment, the third receive array element 52 from the left on the first array vertical axis 54a is spaced apart from the second receive array element 52 by a distance 56e that corresponds to three times the base spacing 40. The seventh receive array element 52 from the left is the rightmost receive array element 52 on the first array vertical axis 54a. The maximum width of the virtual receive antenna array 50 corresponds to a distance 56f between the leftmost receive array element 52 and the rightmost receive array element 52. The distance 56f corresponds to ten times the base spacing 40.

[0134] Additionally, when viewed in the direction of the array longitudinal axes 54a and 54b, the first receive array element 52 from the left on the second array longitudinal axis 54b is positioned between the second and third receive array elements 52 on the first array longitudinal axis 54a at a base spacing 40 from, or offset from, the third receive array element 52.

[0135] When viewed in the direction of the array longitudinal axes 54a and 54b, the second receive array element 52 from the left on the second array longitudinal axis 54b is positioned at the same height as the third receive array element 52 on the first array longitudinal axis 54a.

[0136] When viewed in the direction of the array longitudinal axes 54a and 54b, in each case, the fourth receive array element 52 from the left on the second array longitudinal axis 54b is, for example, centered between the sixth and seventh receive array elements 52 on the first array longitudinal axis 54a, i.e., offset from the element at base spacing 40.

[0137] A method of monitoring a surveillance area 14 for an object 18 includes a radar system 12 having an antenna array 22 according to a second exemplary embodiment being operated in the same manner as a radar system 12 having an antenna array 22 according to a first exemplary embodiment.

[0138] For comparison, FIG. 12 shows a range / direction graph 60c of the radar system 12 in the range operation mode (dashed line) and a range / direction graph 60d of the radar system 12 in the directional operation mode (solid line). Here, each range is recorded at an azimuth angle φ. From FIG. 12, it can be seen that the radar system 12 has a maximum detection range of approximately 250 m in the range operation mode. However, in the directional operation mode, the radar system 12 has a maximum detection range of only slightly less than 200 m. In contrast, at an azimuth angle φ, the radar system 12 has a larger field of view in the directional operation mode than in the range operation mode.

[0139] 13 shows a received signal / direction graph 62d from a direction measurement sequence in which a target object is detected at an azimuth angle φ of 0 degrees ahead of the motor vehicle 10. The sidelobe level is approximately 11.2 dB, which is sufficient to distinguish target objects with different reflectivities, for example, in the actual driving situation of the motor vehicle 10 for that direction, i.e., for each azimuth angle φ.

[0140] 14 shows a family of curves associated with a received signal / direction graph 62e of a number of direction measurement sequences in which two target objects having the same range r and the same speed relative to the radar system 12 are detected at angular intervals of approximately 15 degrees around an azimuth angle φ of 0 degrees ahead of the motor vehicle 10. The family of curves corresponds to direction measurement sequences in which radar signals 30 with different phase differences are transmitted. The two target objects can be distinguished at all possible phase differences. The curves of the family of received signal / direction graphs 62e can be confirmed, for example, by so-called beamforming and / or so-called super-resolution methods and similar techniques.

[0141] A received signal / direction graph 62f for a range measurement sequence corresponding to the situation in Figure 14 is shown in Figure 15. The main lobe width is about 16 degrees. The side lobe level is about 5.25 dB, which is insufficient to distinguish between two target objects in range operation mode.

Claims

[Claim 1] 1. A method of operating a radar system (12) adapted to monitor at least one surveillance area (14) for an object (18), comprising: using the transmit signal to control a plurality of transmit antennas (26) and transmit applicable radar signals (30) into the monitored area (14); receiving echoes (44) of the transmitted radar signal (30) using a plurality of receiving antennas (28), converting the echoes into corresponding received signals, processing the received signals using signal processing, and ascertaining object information (r, φ, Θ) relating to objects within the surveillance area (14) from the received signals; A method comprising: Between at least two radar measurements, switching is performed between a range operation mode in which at least some of the transmitting antennas (26) are at least temporarily controlled using the same transmit signal, and a directional operation mode in which at least some of the transmitting antennas (26) are at least temporarily controlled using different transmit signals such that each received radar signal (30) is at least temporarily distinguishable at at least the receiving antenna (28); the phase centers (32) of the at least four receive antennas (28) are positioned on an imaginary receiver longitudinal axis (46); the phase centers (32) of at least two adjacent receiving antennas (28) are spaced apart from one another by a base spacing (40), and the phase centers (32) of at least two adjacent receiving antennas (28) are spaced apart from one another by a receiver longitudinal spacing (48a, 48b, 48c) greater than the base spacing (40); At least one of the receiver longitudinal spacings (48a, 48b, 48c) is an integer multiple of the base spacing (40), in particular plus or minus a tolerance; The configuration of the transmit antenna (26) and receive antenna (28) is used in a directional steering mode of the radar system (12) to achieve a virtual receive antenna array (50) in which at least two adjacent virtual receive array elements (52) are positioned on at least one virtual array longitudinal axis (54 a, 54 b). A method characterized by:

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