Methods for determining target information of radar targets of a radar system, as well as radar system and vehicle with a corresponding radar system

Abstract

The invention relates to a method for determining target information of radar targets, wherein a transmit signal (10) is emitted by a first antenna array (8) of the radar system (1), a first received signal (11) reflected from a radar target (6) is received by the first antenna array (8) and a second received signal (12) is received by a second antenna array (9), a first distance information (r1) is determined, based on the first distance information (r1) and a first angle hypothesis (Φ (1) ) a second distance information (r2) and a second angle hypothesis (Φ (2) ) for the second antenna array (9), Determining a first optimal filter (MF) (1) ) based on the first distance information (r1) and the first angle hypothesis (Φ (1) ) and / or a second optimal filter (MF (2)) based on the second distance information (r1) and the second angle hypothesis (Φ (2) ) and a target information (14) based on the first and / or second optimal filter (MF (1) , MF (2) ) is determined. Furthermore, the invention relates to a radar system (1) and a vehicle (3).

Description

[0001] The invention relates to a method for determining target information of radar targets of a radar system, wherein at least one transmitted signal is sent into an environment by a first antenna array of the radar system. A first received signal, based on the transmitted signal, reflected by a radar target in the environment, is received by the first antenna array, and a second received signal, also based on the transmitted signal, reflected by the radar target in the environment, is received by a second antenna array different from the first antenna array.

[0002] Furthermore, the invention relates to a radar system comprising a first antenna array, at least a second antenna array and an electronic evaluation unit.

[0003] The invention also relates to a vehicle with a radar system.

[0004] In highly automated vehicles, which have a large number of driver assistance systems or vehicle guidance systems, radar information is of great importance, since assistance systems in particular rely on radar information to be able to perform at least partially autonomous driving maneuvers.

[0005] For example, JP 2005 233 723 A discloses a radar device with distributed antennas. In this device, digital data received by a radar control unit can be extracted at a given time. Based on the transmitted digital data and the received time information, digital beamforming processing based on position information can be performed to obtain the extracted received digital data. Subsequently, beam combination can be performed to detect and display the target.

[0006] Furthermore, CN 110 412 559 A discloses a non-coherent fusion target detection method for a distributed drone MIMO radar. In this method, the position and target velocity of a search base point are first determined, with this point being used as the center to create a four-dimensional search grid. The entire search area is then traversed to obtain distance Doppler information about a target. Based on this information, each receiver of the distributed drone MIMO radar performs customized filtering of the received echo signals and extracts the echo signals transmitted by different platforms.

[0007] For example, WO 2018 158 281 A1 discloses a method and a device for detecting the surrounding area of ​​a moving object, such as a vehicle.

[0008] Furthermore, EP 3 690 483 A1 discloses a design for an optimal antenna array for radar and radio frequency applications, composed of mutually incoherent apertures. This array provides high angular resolution and localization estimation with flexibility in utilizing available space and without the need to synchronize widely separated transmit and / or receive antenna elements. This avoids phase errors due to lack of synchronization, deformation, and vibration, and eliminates the need for techniques such as autofocusing or blind calibration between apertures, which would require multiple snapshots. In this way, a combined effective array factor with low sidelobes can be maintained.All these properties can be used for applications in automotive radar, advanced driver assistance systems (ADAS), ground-penetrating radar, synthetic aperture radar, medical imaging, navigation systems and communication.

[0009] One object of the present invention is to improve the target acquisition or target detection of a radar system or a radar which has mutually incoherent antenna elements or antenna arrays, and in particular to increase the resolving power or angular resolution of the radar system.

[0010] This problem is solved by a method, a radar system, and a vehicle according to the independent patent claims. Meaningful further developments arise from the dependent patent claims.

[0011] Advantageous embodiments of one aspect can be considered advantageous embodiments of the other aspects or of all aspects. The reverse is also true.

[0012] In particular, the radar system and / or the vehicle has (technical) means to carry out or execute the procedure.

[0013] One aspect of the invention relates to a method for determining target information of radar targets of a radar system, wherein - In particular, at least one transmission signal is sent into an environment using a first antenna array of the radar system, - In particular, a first received signal reflected from a radar target in the vicinity, which is based on the transmitted signal, is received by the first antenna array, and - In particular, a second received signal reflected from the radar target in the surrounding area, which is based on the transmitted signal, is received by a second antenna array that is different from the first antenna array, - In particular, at least initial distance information between the first antenna array and the radar target is determined depending on the transmitted signal and the first received signal, - In particular, depending on the initial distance information, at least a first angle hypothesis for the first antenna array is provided, - In particular, based on the first distance information and the first angle hypothesis regarding the first antenna array, a corresponding second distance information and a corresponding second angle hypothesis for the second antenna array are determined, - In particular, determining a first optimal filter based on the first distance information and the first angle hypothesis and / or a second optimal filter based on the second distance information and the second angle hypothesis, and - In particular, at least one target information concerning the radar target is determined based on the first and / or second optimal filter.

[0014] The proposed method can advantageously be used to improve the target acquisition of a radar or radar system.

[0015] In particular, this can increase the accuracy of target acquisition or target detection of radar targets, i.e., objects in the vicinity of the radar system.

[0016] When using a radar system in the automotive sector, for example, precise, improved, yet simpler object detection is necessary. Increased detection performance and reduced sidelobe ambiguity, combined with high angular resolution of the radar system, are important for applications such as lane keeping, overtaking maneuvers, and obstacle detection. The present invention advantageously addresses these needs and can provide a solution.

[0017] In the prior art, the angular resolution can be increased using bistically distributed systems and large coherent apertures. However, this leads to the following problems, which can be solved with the proposed method.

[0018] Bistactic configurations with coherent processing avoid the need for a common local oscillator by correlating with the transmit signal of a radar system antenna. However, such propagation channels can be affected by unknown transfer functions due to active elements, which may be limited by the fields of view. Furthermore, they require pre-measurements of the spacing or time delay between antenna arrays with wavelength accuracy to estimate filament offset. These measurements are difficult to obtain and are subject to vibration and deformation. Another problem with large coherent apparatuses is the need for high-frequency synchronization. These setups place high demands on the calibration of phase imbalances and antenna positions, yet they are also susceptible to vibration and deformation. The proposed method eliminates the need for large coherent apparatuses.Previous systems require a high computational effort for angle processing, especially if the array geometry is not suitable for processing via FFT (Fast Fourier Transform).

[0019] Another problem that can be solved with the proposed method is that the intrinsic calibration of phase mismatches for the large-aperture radar system is sensitive to angular errors of the calibration targets and requires an autocalibration procedure. Such autocalibration procedures can simultaneously estimate the phase mismatch of the channels, the antenna position, and the angles of the calibration targets, which is a multidimensional problem that suffers from ambiguity and may not be robust to deviations in parametric models, such as mutual coupling of non-uniform polarization.

[0020] The problems mentioned above can be solved at least partially, and in particular completely, by the proposed method. The proposed method allows for the incoherent combination of monostatic and bistatic signals. By coupling the range or distance with the angle of a radar target, the determination of target information, such as angular resolution, can be improved, particularly through sequential estimation.

[0021] For example, in incoherent beamforming allows for the optimization of antenna positions in mutually incoherent array apertures. This can be achieved using the proposed method. The individual apertures or antenna arrays can be very sparsely spaced and may exhibit high sidelobes. By combining them, the sidelobes can be averaged, resulting in higher resolution with good sidelobe levels. In contrast to the prior art, the present invention eliminates the need for the target to be identifiable, correctly assigned between the individual apertures of the antenna arrays, and exhibited with a similar signal-to-noise ratio (SNR) from the different apertures.For example, there are systems and algorithms for azimuth and height estimation that use road reflections to increase the height resolution, including combining phases from multiple apertures. Furthermore, for example, improved azimuth estimation can be performed with the present invention.

[0022] For example, in the present invention, a processing chain can be provided with the distance assignment between the apertures, i.e., at individual antenna elements of the antenna arrays, as a function of the angle hypothesis and the sequential angle estimation. This allows the residual to be updated for each distance field. In addition to the aperture control of radar systems in the automotive sector, incoherent beam shaping can also be used in other areas such as aerospace or automation. For example, according to the invention, at least one target information can be generated based on a sparse reconstruction algorithm such as "Block Orthogonal Matching Pursuit" (BOMP) or "Block Nearly Orthogonal Matching Pursuit" (Block-NOMP).

[0023] For example, the proposed method can be used in distributed radar systems with multiple configurations or bistatic configurations. Specifically, multipath or bistatic approaches with coherent phases can be used to increase resolution. This involves considering and utilizing a combination of one or more radar sensors and one or more transceivers, known as repeater tags. In the case of a MIMO sensor and a repeater tag, the repeater tag receives the target's echo and retransmits it, amplified and with a frequency shift, back to the receiver of the original sensor, which follows the target's path. This frequency shift allows the bistatic path to be identified. The bistatic path between the sensor and the repeater tag can remain coherent.This results in a virtual array that keeps the sensor's virtual TX-RX pairs, plus a virtual repetition of the transmitters, at a distance that depends on the distance of the repeater tag and the angle of the target. Since the combined virtual array has a length equal to the distance of the repeater tag, the aperture is increased, theoretically allowing for a higher resolution. However, this approach typically encounters the following problems, which can be solved by the proposed method.

[0024] The distance between the repeater tag and the sensor must be known with wavelength accuracy. This appears achievable for short ranges, which can indeed lead to a significant improvement in resolution, as a few centimeters may suffice. However, at greater distances, deformation and vibrations can impair the radar system's performance. Another issue is the gap in the virtual aperture, as this can cause high sidelobes that may obscure targets. Furthermore, performance can degrade with multiple targets because the bistatic range, even if separated from the monostatic path by a frequency shift, may coincide with the monostatic range of another target.

[0025] These problems are solved by the proposed method because the proposed method does not perform any correlations with bistatic signals using a transceiver, and therefore the problems mentioned above can be solved with the proposed method.

[0026] Furthermore, distributed systems are known that avoid the use of a common local oscillator by utilizing bistatic signal processing while maintaining phase information, i.e., these signals are coherent. The bistatic feedback from the target is encoded with crosstalk channels, which must first be measured to estimate the phase shift. Thus, prior measurements of the distance between the individual antennas with wavelength accuracy are necessary, and unknown transfer functions can cause this propagation channel and the lack of a clear line of sight when the field of view is restricted. These problems can be solved by the present invention. The present invention uses distance-angle coupling to enable target acquisition or determination of target information even with an incoherent arrangement of radar system antennas.If the combined distance between the individual antennas is greater than the distance due to a geometric near field or near field path, the proposed method can be used advantageously here.

[0027] Furthermore, there are systems that use the processing of standard three-dimensional FFTs for cascaded, adjacent radar systems. However, these cannot use separate apertures. The present method can be used primarily by radar systems that have separately or remotely arranged apertures.

[0028] Previous systems utilize an approach for fusing multiple and multimodal sensors, combining information at the level of time estimates, for example, using Kalman filtering or particle filtering. In contrast, the present invention combines complementary spectra across apertures.

[0029] In particular, the proposed method may be a computer-implemented method.

[0030] Using the proposed method, target information or radar information of radar targets of a radar system, which can be used particularly in a vehicle, can be determined.

[0031] The radar system can have several distributed antenna arrays. An antenna array, also called an aperture or array aperture, is a surface or defined area on or within which several or a large number of individual antennas or antenna elements are arranged. Most importantly, an antenna array can be used to both transmit and receive signals.

[0032] In the vicinity of the radar system, at least one or more transmitted signals can be emitted. If at least one of these transmitted signals, such as the transmitted signal, encounters a radar target, like an object in the vicinity, this signal is reflected and reflected back towards the radar system. Multiple reflected signals can be re-emitted. At least one received signal can be received by the first antenna array, and at least a second received signal can be received by the second antenna array. In other words, a signal can be transmitted using one antenna array, which in turn can be received by two or more antenna arrays.In this case, the first antenna array experiences a monostatic return of the signal, since the transmitted signal was both sent and received by the first antenna array. The second antenna array experiences a bistatic return, since the transmitted signal was not, and certainly not necessarily, sent by the second antenna array.

[0033] Based on the monostatic signal return from the first antenna array, initial range information can be determined using the Doppler effect, for example. This range information represents the distance or range between the first antenna array and the radar target. Similarly, multiple transmitted signals can be received, each corresponding to multiple received signals. Thus, multiple radar targets can be evaluated and reflected accordingly.

[0034] Based on the initial range information and thus a first Doppler effect determination, several angle hypotheses, i.e., mathematical hypotheses, can be formulated regarding the radar target. Specifically, at least one angle hypothesis can be formulated or provided for each range measurement determined by the first antenna array. Since the second antenna array only receives the signal and has not transmitted a corresponding signal, a correlation can now be performed based on the initial range information and the initial angle hypothesis to obtain a corresponding second range measurement for the second antenna array. In other words, based on the information concerning the first antenna array, the range between the second antenna array and the radar target is estimated, determined, or calculated.Thus, a second distance measurement corresponding to the first distance measurement can be determined. Similarly, a second angle hypothesis corresponding to the first angle hypothesis is determined. The advantages of the proposed method are already evident here, as a corresponding distance and angle determination has been performed for one antenna array and can then be used for further antenna arrays.

[0035] Thus, even with an incoherent antenna array, target determination can be carried out by each antenna array in the simplest way, since the corresponding information can be shared.

[0036] For the first and / or the second antenna array and the corresponding radar information from the first and second antenna arrays, an optimal filter, a so-called "match filter," can be generated or determined. Thus, an optimal filter can be provided for each antenna array to filter the corresponding information. For example, based on the two optimal filters or for the respective optimal filters of all antenna arrays, a generalization of the average "match filter" can be made. This can then be used, for example, to determine target information, such as an angle estimation.

[0037] For example, an antenna array can be described as an antenna arrangement, preferably designed as a planar arrangement of antennas. These antenna arrays can consist of transmitting and / or receiving antennas arranged in various configurations. In particular, the antenna arrays can be sparsely populated or thinned-out antenna arrangements. This is especially advantageous when using radar systems in the automotive sector, since, particularly for 360-degree detection of the vehicle's surroundings, antenna arrays should be arranged in various and differently configured areas in or on the vehicle.

[0038] In one embodiment, the initial distance information is determined using a fast Fourier transform (FFT). Based on the information from the received signals, a distance Doppler calculation, and thus a distance determination based on the Doppler effect, can be performed for each antenna array. To achieve particularly efficient calculations, a suitable mathematical transformation, such as the fast Fourier transform, can be used.

[0039] Other mathematical operations or transformations can also be used.

[0040] The false alarm rate (FAR) is a measure of the performance of a radar system. When radar receives echo signals, these signals are displayed against background noise. The noise signals occur with statistically distributed amplitudes that correspond to those of useful signals and are processed as such. This can lead to the display of incorrect radar targets. The false alarm rate is defined as the average number of false targets detected at the receiver output of the radar system within a specific time period, for example, per antenna rotation or per pulse repetition period. The constant false alarm rate (CFAR) is used to assume or utilize a constant false alarm rate, particularly for the duration of radar target acquisition or detection.In this context, an adapted function based on the perceived environmental conditions of the radar system's surroundings can be used. This allows for better suppression of false alarms and incorrect target detections, especially at close range. Accordingly, using a constant false alarm rate can increase the detection and acquisition of radar targets, particularly in their vicinity. This, in turn, can extend the radar system's range.

[0041] In one embodiment, extrinsic calibration is performed on the first and / or second antenna array to determine the second distance information and the second angle hypothesis for the second antenna array based on this extrinsic calibration. This is necessary because a coordinate transformation, or rather the provision of a common coordinate system for the first and second antenna arrays, is required to determine the corresponding second distance information and second angle hypothesis of the second antenna array based on the first distance information and the first angle hypothesis.To deduce the corresponding information from the second antenna array based on the information or data obtained from the first, a common coordinate system for both arrays is necessary for the calculation. To synchronize the two arrays for the calculation, a calibration is performed. This primarily involves intrinsic calibration. Extrinsic calibration combines the spatial position and orientation of the first and second antenna arrays into a single reference coordinate system. This allows a common reference coordinate system to be used for converting the distance information and angle assumptions of the first antenna array to the second.

[0042] In one embodiment, it is provided that the system checks whether the first antenna array is intrinsically calibrated. If so, the second antenna array is calibrated based on a cooperative auto-calibration procedure, depending on the calibrated first antenna array. Intrinsic calibration refers to the mapping of three-dimensional points in the camera coordinate system, i.e., in the radar system, onto a two-dimensional camera sensor, in this case, the antenna arrays. Thus, it can first be checked or determined whether the first antenna array is calibrated or not. If it is already calibrated, the second antenna array and other antenna arrays of the radar system can be calibrated in the simplest way based on this calibrated first antenna array.In other words, it may be sufficient for one antenna array of the radar system to be calibrated, and the other antenna arrays can then be calibrated based on this single calibrated receiver array. To perform the calibration of the other antenna arrays in the simplest and fastest way possible, a cooperative auto-calibration procedure is used. This allows all, or at least some, antenna arrays of the radar system to be calibrated automatically in an efficient manner. This is particularly advantageous for the accuracy of target detection and, in particular, for the precise determination of target information regarding radar targets.

[0043] The cooperative auto-calibration method is particularly useful for distributed antenna arrays in the automotive sector. Depending on the number of antenna arrays and their location and positioning on or in the vehicle, one antenna array can be calibrated first, and the remaining arrays can then be automatically calibrated based on this already calibrated array.

[0044] In one embodiment, it is provided that it is checked whether the determined second angle hypothesis lies within the field of view of the second antenna array. If the second angle hypothesis is within the field of view, at least one target piece of information is determined based on the first and second optimal filters. A field of view refers to the area within the viewing angle of an optical device within which events or changes can be perceived and recorded. An angle hypothesis can, for example, be used to understand an angular function. In particular, an angle hypothesis allows for the hypothetical consideration of various angles at which a radar target can be positioned relative to the radar. Thus, it is possible that the angle of the radar target relative to the radar or an antenna array lies outside its field of view and therefore outside its detection range.In other words, the angle hypotheses must be formulated or theoretically defined in such a way that the possible angle hypotheses lie within the field of view, otherwise radar target acquisition is impossible. Since the second angle hypothesis was determined based on the first angle hypothesis of the first antenna array, it can be verified whether this second angle hypothesis is indeed within the field of view of the second antenna array. If so, the information concerning the first and second antenna arrays, based on the two optimal filters, can be used to determine at least one target information or multiple target information pieces for the radar target. If the second angle hypothesis lies outside the field of view of the second antenna array, this information cannot be used to determine the target information.Accordingly, the target information is determined here based on the information from the first antenna array and, in particular, the first optimal filter.

[0045] In one embodiment, a first antenna signal of the first antenna array is determined based on the first distance information and antenna information relating to the antenna elements of the first antenna array. A second antenna signal of the second antenna array is determined based on the second distance information and antenna information relating to the antenna elements of the second antenna array. Based on the respective information from the first and second antenna arrays, a corresponding antenna signal can be generated for further processing. Each antenna signal is determined based on information from its respective antenna array. In addition to the respective distance information and antenna information, the respective angular assumptions of an antenna array can also be taken into account.Antenna information primarily concerns individual antenna elements, such as the transmitting and / or receiving antennas, of a given antenna array. In particular, virtual transmitting and receiving antennas, also known as TX-RX pairs (i.e., transmitting and receiving elements), of a given antenna element can be used to determine the respective antenna signal. Using the antenna signal simplifies further processing for determining the target information.

[0046] In one embodiment, the first optimal filter of the first antenna array is determined based on the first antenna signal and a predefined model of a spatial region of the first antenna array. This allows the generation of an optimal filter, or "match filter," adapted to the first antenna array. A key distinction here is between two situations: near-field and far-field detection. In other words, the distinction is made between whether the radar target is located in a near field or a far field. Depending on the situation, a corresponding predefined model, particularly a vector model (also known as a guidance vector model), can be considered when determining the optimal filter.Similarly, the second optimal filter can be determined based on the second antenna signal and a given model of a boundary region of the second antenna array.

[0047] Additionally or instead, nominal or calibrated antenna positions of the individual antenna elements of the first or second antenna array and / or phase asymmetries or phase imbalances of the first or second antenna array can be taken into account when determining the first and / or second optimal filter.

[0048] In one embodiment, a near-field vector model or a far-field vector model is provided as a predefined model of the spatial region of the first and second antenna arrays. Thus, depending on whether a near or far radar target is being detected with the respective antenna array, a suitable model can be provided and used, in particular, for calculation or determination.

[0049] The near field, also known as the reactive near field, refers to the area in the immediate vicinity of an antenna, such as an antenna array. The far field, also called the Fraunhofer region, is the largest area in which electromagnetic waves can propagate independently of the antenna as plane waves in space.

[0050] In one embodiment, the first antenna signal is filtered using the first optimal filter, and the second antenna signal is filtered using the second optimal filter. Based on the filtered first and second antenna signals, at least one piece of target information is determined. In other words, the determined or calculated antenna signals can be filtered accordingly to obtain the target information, such as the angle of the radar target. In particular, the target information can be used to perform an angle estimation of the radar target.

[0051] In one embodiment, at least one target piece of information is determined based on an orthogonal matching pursuit algorithm. Thus, using the corresponding distance information, angle hypotheses, and optimal filters, an approximation algorithm, particularly a sparse one, can be applied to determine the corresponding target piece of information or pieces of target information.

[0052] In one embodiment, the at least one target information component provides an angle and / or direction to the radar target. In other words, the target information can be used, in particular, to estimate the angle between the radar target and the radar system, and / or to determine the direction of the radar target. This is especially relevant for detecting the surroundings of a vehicle.

[0053] Another aspect of the invention relates to a radar system comprising a first antenna array, a second antenna array, and an electronic evaluation unit, wherein the radar system is configured to perform a method according to the previous aspect or an advantageous embodiment thereof. In particular, the method described above can be performed with the aforementioned radar system.

[0054] The radar system is, in particular, an electronic radar device or radar assembly with which radar targets can be detected or acquired in an environment. The radar system can, in particular, comprise multiple antenna arrays, which in turn can be referred to as an antenna arrangement. Thus, the radar system can have a multitude of distributed antenna arrays, each of which can contain multiple transmitting and receiving elements. Therefore, the proposed radar system can be used to perform, in particular, 360-degree surveillance of an area.

[0055] The electronic evaluation unit can be an electronic computing system. In particular, the electronic evaluation unit can be designed as a distributed system, with at least part of it located in a specific antenna array to perform preprocessing. Alternatively, the electronic evaluation unit can be a central system that is communicatively and / or data-technically linked or coupled to the respective antenna arrays to perform the corresponding evaluation of the target information.

[0056] In one embodiment of the further aspect, the first and second antenna arrays are arranged at a distance from each other. In particular, the antenna arrays of the radar system are arranged far apart, so that a large area can be covered with fewer antenna arrays. With the method according to the previous aspect, radar information can again be effectively determined even if the antenna arrays of the radar system have uneven, heavy, and / or non-equidistant antenna spacings. This is particularly advantageous for the use of the radar system in the automotive sector, since antenna arrays can thus be arranged in various areas or positions in and / or on the vehicle in order to perform, in particular, 360-degree coverage of the vehicle's surroundings.

[0057] Another aspect of the invention relates to a vehicle with a radar system according to the previous aspect or an advantageous embodiment thereof. In particular, the aforementioned radar system can be integrated or installed in the aforementioned vehicle. Thus, the aforementioned radar system can be used for the vehicle's environment detection. This can be particularly advantageous for driver assistance systems or autonomous systems of the vehicle.

[0058] Advantageous embodiments of one aspect can be considered advantageous embodiments of the other aspects or of all aspects. The reverse is also true.

[0059] In particular, the radar system and / or the vehicle has (technical) means to carry out or execute the procedure.

[0060] For use cases or application situations that may arise during the procedure and are not explicitly described here, it may be provided that, according to the procedure, an error message and / or a request for user feedback is issued and / or a default setting and / or a predetermined initial state is set.

[0061] The invention also includes further developments of the radar system and the vehicle according to the invention, which have features already described in connection with the further developments of the method according to the invention. For this reason, the corresponding further developments of the radar system and the vehicle according to the invention are not described again here.

[0062] The invention also includes combinations of the features of the described embodiments.

[0063] The following describes exemplary embodiments of the invention. This is illustrated by: Fig. 1 an exemplary radar system used on a vehicle; Fig. 2 a schematic representation of two antenna arrays of the radar system Fig. 1 in a far-field situation; Fig. 3 again contrary to the Fig. 2 the case of a near-field detection situation; Fig. 4. A schematic procedure for determining target information from the radar system Fig. 1; Fig. 5 a continuation of the statements from Fig. 4 with an additional functionality of an orthogonal matching pursuit algorithm; Fig. 6. A further schematic representation of the determination of target information or the performance of an angle estimation of incoherent antenna arrays; and Fig. 7 starting from Fig. 1. For different antenna arrays, the respective fields of view, which overlap.

[0064] The embodiments described below are preferred embodiments of the invention. In these embodiments, the described components each represent individual features of the invention that can be considered independently of one another. Each of these features further develops the invention independently and can therefore be considered part of the invention individually or in a combination other than that shown. Furthermore, the described embodiments can also be supplemented by other features of the invention already described.

[0065] In the figures, functionally identical elements are each provided with the same reference symbols.

[0066] In the Fig. Figure 1 shows a schematic representation of a radar system 1. The radar system 1 can be used, in particular, for environmental sensing. Specifically, radar targets or objects in the environment 2 of the radar system 1 can be detected. In this embodiment, the radar system 1 can be used in the automotive sector. Here, the radar system 1 is arranged in or integrated into a vehicle 3, in particular a motor vehicle. Thus, the environment 2, here the vehicle's surroundings, can be detected with the aid of the radar system 1. This is particularly advantageous for driver assistance systems and especially for systems for performing at least partially autonomous interventions.

[0067] The radar system 1 can include an electronic evaluation unit 4 for processing information, data and / or signals.

[0068] Furthermore, the radar system 1 can have a plurality of antenna arrays 5, also referred to as antenna apertures. As in this embodiment regarding the use of the radar system 1 in the vehicle 2, the antenna arrays 5 are located in the front area of ​​the vehicle 3. Likewise, further antenna arrays 5 can be arranged in the surrounding body of the vehicle 3.

[0069] The antenna array 5 can, for example, be an antenna arrangement, in particular an uneven, sparsely populated antenna arrangement. In this case, the antenna distances between the individual antenna arrays 5 can be non-equidistant.

[0070] An antenna array 5 can in particular be an antenna arrangement which in turn has a large number of individual transmitting and / or receiving antennas.

[0071] For example, a radar target 6, such as an object in the environment 2, can be located in front of the vehicle 3, particularly in the direction of travel 7. This radar target 6 can thus represent a collision object or a disturbing object with respect to the vehicle 3. It is essential to detect this object as effectively and efficiently as possible. The radar system 1 according to the invention is used for this purpose. For example, a distance n to the at least one antenna element and the radar target 6 can be determined using the radar system 1. Furthermore, an azimuth angle Φ can be determined. Likewise, as described in the Fig. As shown in Figure 1, a polar angle θ can be determined. These are exemplary quantities for defining or determining a distance, direction and / or angle relative to the vehicle 3 and the radar target 6.

[0072] The radar system 1 according to the invention uses an incoherent combination of monostatic and bisstatic radar echoes or radar signals via the antenna arrays 5 for target acquisition or target detection of the radar target 6, in particular for determining target information of the radar target 6. For this purpose, a generalization of the average "match filter" is used for a possibly subsequent angle estimation, whereby the coupling between distance and angle is taken into account and used.

[0073] In the Fig. 2 and in the Fig. Figure 3 shows two antenna arrays 8, 9 as examples, i.e. a first and a second antenna array 8, 9.

[0074] In the Fig. Figure 2 represents the far field of the antenna arrays 8 and 9. The radar target 6 is located at a considerable distance from the antenna arrays 8 and 9. The first antenna array 8 can transmit at least one signal 10. This transmitted signal 10 can reach the radar target 6 or multiple other radar targets and be reflected or bounced back once or multiple times. Accordingly, at least one initial signal 11 can be received by the first antenna array 8 and a second signal 12 by the second antenna array 9. In this case, the first antenna array 8 is monostatic, as it both transmits and receives. The second antenna array 9 can be bistastatic, as it only receives.The first antenna array 8 can have at least one transmitting antenna or transmitting element and one receiving element or receiving antenna. The second antenna array 9 can have at least one receiving element accordingly. In order to determine the distances and / or angles of the radar target 6 or another radar target, the transmission channel d can be formed between the antenna arrays 8 and 9.

[0075] This transmission channel d can, for example, be an "eavesdropping or cross-talk propagation channel". Thus, the corresponding Rx and Tx elements of the two antenna arrays 8, 9 can exchange radar information or radar signals. In the Fig. 3 is contrary to the example from Fig. Figure 2 shows the area covered by radar system 1 in a near field. Here, signal 10 is again transmitted and the received signals 11, 12 are received accordingly by the antenna arrays 8, 9.

[0076] Furthermore, in the Fig. For example, distances r1 and r2 are shown in Figure 3. These are, in particular, the distances or distance information between antenna arrays 8 and 9 and the radar target 6. Furthermore, the two angles or angular separations of antenna arrays 8 and 9 with respect to the radar target 6 are shown here. In the case of a monostatic signal, antenna arrays 8 and 9 can have the same local oscillator.

[0077] In an incoherent bistastatic case, different local oscillators can be used. A "soft" or "mild" synchronization between the two antenna arrays 8 and 9 may be sufficient. Phase noise can occur because the noise characteristics of the different local oscillators may differ. In this case, more virtual apertures can be used.

[0078] In a coherent bistactic case or situation, a crosstalk signal can be mixed between the antenna arrays 8 and 9 according to the two transmissions. However, the distance between the two antenna arrays 8 and 9 must be precisely specified or defined.

[0079] In the following Fig. Figure 4 shows a schematic representation of a process for determining target information according to the invention concerning a radar target 6.

[0080] In particular, the present invention enables the incoherent combination of monostatic and bisstatic transmit and receive signals across multiple antenna arrays 5 using a generalization of an average match filter. This can be used, in particular, for subsequent angle estimation, so that, for example, an angle can be provided as target information 14. For this purpose, soft synchronization of the antenna arrays 5 on the order of the delay of a distance spin can be performed, and the bisstatic receive signals can be incoherently integrated or determined using a multiplexing method such as TDM, which also only requires soft synchronization.

[0081] First, the received signals 11, 12 can be digitized in steps S10, S11. Accordingly, processing can be carried out in one processing path or processing chain with regard to the first antenna array 8, and processing or evaluation with regard to the second antenna array 9 can be carried out in a further processing chain.

[0082] The digitization of the received signals 11, 12 can be carried out using an analog-to-digital converter (ADC). First, the distance information r1, r2 can be determined. For this purpose, a conventional two-dimensional FFT can be performed. In particular, a fast Fourier transform is performed on the ADC data of a respective receiver, i.e., an Rx element of a respective antenna array 8, 9. This can then be carried out in optional steps S20 and S21. Here, a Doppler frequency, or range Doppler frequency, can be determined. This can be done, for example, for a respective antenna array 5.

[0083] In optional steps S30 and S31, a constant false alarm rate can be used or specified for each antenna array 8, 9, so that potential targets can be detected based on these detections. In particular, the first distance information r1 can be determined. This can also be applied to the second distance information r2. For example, distance Doppler detections r can be performed for each antenna array 8, 9. (1) , r (2) Possible distance information r1, r2, can be determined or provided. Detections can be determined for either one radar target (6) or for multiple radar targets. For example, based on a distance Doppler detection r (1) and a corresponding first angle hypothesis Φ (1)of the first antenna array 8 the corresponding or equivalent distance Doppler detection r (2) and the associated angle hypothesis Φ (2) This can be calculated. This can be done especially for a large number of possible angle hypotheses concerning the first antenna array 8.

[0084] This can be defined, for example, with the following formula: (r(2),ϕ(2))=T(r(1),ϕ(1))

[0085] To assign the respective data or information from the first antenna array 8 to the second antenna array 9, the antenna arrays 8 and 9 must be fitted by a coordinate transformation T. This can also be referred to as preliminary extrinsic calibration. Furthermore, in step S40, it can be checked whether the associated angle hypothesis Φ is correct. (2)lies within the field of view of the second antenna array 9. If this is the case, further processing can proceed. Otherwise, standard processing based on the first antenna array 8 is performed, for example, to determine the target information.

[0086] Distance Doppler detection r (2) Based on the false alarm rate for the second antenna array 9, it can be determined whether or not a target has been detected. The respective cases can be differentiated and considered separately, as an aspect angle in an antenna array 5 can lead to a lower RCS (Reference Counter Score).

[0087] A respective antenna signal γ (1) (r1), γ (2) (r (2) The array signal of the first and second antenna arrays 8, 9 can be provided for further processing. A respective antenna signal or array signal γ (1) (r1), γ (2) (r (2)) of a respective antenna array 8, 9, the spectral phases can be measured via T x -R x -pairs of the corresponding apertures or antenna arrays 8, 9, which are used in a corresponding distance Doppler detection system. (1) , r (2) were detected or calculated.

[0088] Subsequently, in one step S50, a first optimal filter MF can be applied. (1) for the first antenna array 8 and in one step S51 a second optimal filter MF (2) These can be determined. These are the optimal filters MF. (1) , MF (2) to adapt filters or match filters, which are adapted or determined for each antenna array 8, 9, as can be expressed as follows: MF(i)(ϕ(i)),i=1,2,

[0089] These optimal filters can be determined by correlating the antenna signals with a near-field or far-field model based on nominal or calibrated antenna positions and point symmetries. This can be done using the following formula, where i represents a specific antenna array. MF(i)(ϕ(i))=|(a(i)(ϕ(i)))Hy(i)(ri)|

[0090] For example, when using a near-field steering vector model, the dependence on distance can already be included, which can be described as follows: a(i)(ϕ(i),r(i))

[0091] To determine an average or sum-adjusted optimal filter, which is based on the two optimal filters MF (1) , MF (2) was determined, can be used for the angle hypotheses Φ (1) and Φ (2) can be determined or calculated. This can be done using the following formula: MF¯(ϕ(1))=MF(1)(ϕ(1))+MF(2)(ϕ(2))

[0092] Two alternatives are available for applying the average matching optimal filter for a given angle hypothesis. In one alternative, the peak values ​​can be distributed across the angle hypothesis Φ. (1) , Φ (2) for each distance Doppler detection r (1) and each corresponding reference frame of the second antenna array 9.

[0093] In the other, or second, alternative, an “orthogonal matching pursuit algorithm” 13 can be applied, particularly for determining the target information. This algorithm 13 can be an “associated range-angle block orthogonal matching pursuit” (ARABOMP).

[0094] This algorithm 13 can be performed iteratively, particularly in a step S60. This involves first averaging the strongest target signal and then iterating with the antenna signals, which can be replaced by the residual for each distance.

[0095] In step S60, the average optimal filter can again be determined (compare Fig. 5) The exact procedure of the second alternative for evaluating the average matching filter is described below. Fig. Section 5 explains this again. Here, the next steps or processing steps are discussed. Fig. Figure 4 shows that step S70 can now be performed after step S60. An initiated residual can be generated in this process. u0(i)(r(i))=y(i)(r(i)) assumed. Here, for each distance Doppler detection, r (1)Accordingly, one iteration is performed. Here, for each angle hypothesis Φ, the following can be determined: (2) and the associated distance an angle hypothesis Φ (2) in the second antenna array 9, as below. (r(2),ϕ(2))=T(r(1),ϕ(1))

[0096] The average adjusted optimal filter with the residual can be calculated as follows: MF(i)(ϕi)=|(a(i)(ϕi))Huk(i)(r(i))|

[0097] In step S71, the angle of the strongest detected target, such as radar target 6, can be determined. The following formula can be used for this determination. ϕk+1(1)=arg max MF¯(ϕ(1))

[0098] In a subsequent step S72, amplitudes can be determined for the identified targets. sk+1(1),sk+1(2) to determine which ones can be calculated using an orthogonal projection.

[0099] The residuals can be updated in step S73 for the corresponding distances or distance ranges as follows: uk+1(1)(r(1)):=uk(1)(r(1))−sk+1(1)a(1)(ϕk+1(1)), uk+1(2)(r(2)):=uk(2)(r(2))−sk+1(2)a(2)(ϕk+1(2)).

[0100] If the size of the array signal residue is smaller than a certain threshold for the corresponding distance band, the search for an angle for that distance is aborted.

[0101] In step S74, further iterations can be performed for k + 1 iterations. To efficiently determine the radar target 6 and, in particular, the target information, such as the corresponding angle, it can be verified whether the first antenna array 8 is intrinsically calibrated. Further embodiments are explained below.

[0102] If the first antenna array 8 is intrinsically calibrated and, for example, the second antenna array 9 is not, a cooperative intrinsic autocalibration procedure can optionally be used, in which the first antenna array 8 either provides an angle estimate or the angle estimate is performed jointly with the estimate and symmetry of the second antenna array 9. In the latter case, the joint optimization for radar target 6 can be described as follows: ϕ(1),ψ(2)=arg max MF(1)(ϕ(1))+|(D(ψ(2))a(2)(ϕ(2)))Hy(2)(r(2))|

[0103] This can be a (2) (ϕ (2) ) the far-field or near-field longitudinal vector model and D(ψ (2) ) is defined as follows with respect to the phase asymmetry of the Tx and Rx channels: ψTx(2)=(ψTx1,...,ψTxN),ψRx(2)=(ψRx1,...,ψRxM), D(ψ(2)):=exp(j diag(ψTx(2)⊗ψRx(2)))

[0104] It should be noted that the optimization is performed using ϕ.(1) sufficient, since ϕ (2) a function of ϕ (1) according to the target association (r(2),ϕ(2))=T(r(1),ϕ(1)).

[0105] Potential advantages of cooperative calibration in the case of a small calibrated antenna array and a large uncalibrated antenna array are evident, at least in a controlled scenario or situation where the same target group shares a distance field and the corresponding distance field in the other antenna arrays. Considering an antenna array consisting of a large array with a large product of transmit / receive elements combined with a small antenna array, the large antenna array benefits from measurements, but the resolution is too high, and it can be very sensitive to DOA (angle estimation). With known positions, joint estimations of phase and angle for smaller arrays can be performed more easily.The average matched filter (that is, the average of the angular spectra) benefits from low sensitivity to angle estimation due to the average resolution. In other words, the matched angle of the small antenna array acts like a smoother or regulator. This can be an advantage over simply passing on a previous estimate.

[0106] If the large antenna array detects two or more targets due to its resolution, the smoothing effect helps to automatically group them, which is also beneficial for angle estimation, and thus particularly for phase estimation. Meanwhile, the optional estimation of the antenna position of individual antenna elements results from a large number of measurements. A further advantage over amplitude tapering is that the average-matched filter does not experience SMR loss, as with tapering, and benefits from the already calibrated antenna array.

[0107] As previously explained, various steering vector models can be used. The formulas described below describe an array steering vector model for a given antenna array, where, for the sake of simplicity, the superindices a = a (i) omitted for better understanding.

[0108] The following describes the model of the steering vector in the near field, i.e., in the spherical wavefront. In the near field, for a receiver located in the reception area {p i = [x i , y i , z i ]} at an angle ϕ, θ by a distance r, the receiver control vector: [aRx(ϕ,θ,r)]i=exp(−j2πλr1−2rnTpi+piTpir2)

[0109] This can be done with n :=[cos(θ)cos(ϕ), cos(θ)sin(ϕ),sin(θ)] The target direction is specified. Due to the reciprocity of sending and receiving, the transmission control vector is... aTx(ϕ,θ,r) analogous to the transmission sites.

[0110] The array signal model for the virtual Tx-Rx pairs is defined as follows: a(ϕ,θ,r):=aTx(ϕ,θ,r)⊗aRx(ϕ,θ,r), where The ⊗ refers to the Kronecker product.

[0111] In the bistactic scenario, where the transmitter and receiver (i.e., the transmitting and receiving elements of the antenna arrays 5) are located in different antenna arrays, the frame of reference can be related to the transformation from the extrinsic calibration. For example, if the transmitters are located in the first antenna array 8 and the receivers in the second antenna array 9, this can be described as follows: [aRx(ϕ,θ)]i=exp(j2πλnTpi), where (r(2),ϕ(1),θ(2))=T(r(1),ϕ(1),θ(2)) applies.

[0112] The far-field control vector model, i.e., in the plane wavefront, is described below. In the far field, the control vector or the array signal simplifies, either through transmission or the receiver, to [aRx(ϕ,θ)]i=exp(j2πλnTpi).

[0113] In the monostatic case, the combined control vector of sending and receiving is defined as follows: a(ϕ,θ) :=aTx(ϕ,θ)⊗aRx(ϕ,θ)=exp(j2πλnTpvirt) with p virt = p Tx ⊕ p Rx , taking into account the Kronecker sum ⊕.

[0114] In the bistactic case, the planar wavefronts are viewed from the perspective of each antenna array, and the intrinsic calibration transformation can be related, as in the near-field case.

[0115] In the Fig. Section 6 describes the method according to the invention elsewhere.

[0116] First, in one step S80, the distance information r can be obtained. (1) or the distance Doppler detection r (1)to be determined. Here, it can again be checked whether the distance Doppler detection or the target detection of the second antenna array 9 corresponds to the first antenna array 8, as with the condition r (1) (1) = r (2) (1)This corresponds to the following. Subsequently, a distinction can be made between near-field and far-field acquisition. In step S81, the processing of information for a near field is carried out, and in step S82, the processing is carried out for a far field. After step S81, it may have been determined in step S90 that the second antenna array 9 has different "range pins" compared to the first antenna array 8. This may not be the case, so the process can be terminated in step S83. If, however, the second antenna array 9 has the same "range pin" as antenna 1, as with condition r (1) (2) = r (2) (2)This can be determined in step S84. Subsequently, in step S85, the SMR can be amplified again, and further calculations can be performed using algorithm 13.

[0117] If the focus shifts to step S82, i.e., a far field, then, for example, step S86 can be used to check whether the range information of the first antenna array 8 and the second antenna array 9 is the same. If this is the case, then in step S88 the sidelobe suppression can be improved, since the second antenna array 9 has also detected the radar target 6 and further targets can be detected. If in step S87 it is determined that the range information of the two antenna arrays 8 and 9 is the same, then in step S89 the SMR can be increased and the procedure of algorithm 13 can be started or continued.

[0118] In other words, if radar target 6 or more radar targets are detected in each antenna array 8, 9 and thus have a range information, the ARA-BOMP method can be used to find the strongest target and remove it from the range information or range fields. The obscuration of sidelobes can be reduced, precisely because of the residual update, and the resolution can be increased accordingly. It should be noted that a common range and common far angle can occur if the targets are positioned symmetrically above and / or behind one antenna array.

[0119] In the following Fig.Figure 7 again shows vehicle 3. Various viewing areas 15, 16, and 17 for different antenna arrays 5 are depicted. The antenna arrays 5 are arranged so that the viewing areas or fields of view 15 to 17 overlap to cover the largest possible area with sensors. Each viewing area 15 to 17 can be designed for different angles or angle hypotheses.

[0120] In the following steps, particularly before the radar is operated, an intrinsic calibration using calibration targets can be performed for each target detection or acquisition system to carry out a coordinate transformation between the reference frames of the antenna arrays 5. This allows for the consideration of potentially unknown relative positional orientations of the antenna arrays 5 due to manufacturing or assembly tolerances. One advantage is that the coordinate transformation does not require wavelength accuracy, as the information is combined at the level of spectra or absolutely supported filters. The transformation T is calculated only once, but then for the range spin or for each antenna array 5. For simplicity, this transformation is expressed in polar coordinates, such as... (r(2),ϕ(2))=T(r(1),ϕ(1)).

[0121] Furthermore, an adjustment to Cartesian coordinates can also be made here.

[0122] The presented method for target detection or the determination of target information applies to any two-dimensional and three-dimensional geometries, provided that the coupling between the antenna arrays 5 does not occur within each antenna array 5. Far-field or after-field models a (1) a (2) can be taken into account or used.

[0123] However, for uniform arrays or antenna arrays 5 or antenna arrays with special symmetries, standard smoothing methods can be included for target decorrelation.

[0124] Furthermore, it should be noted that the signals y (1) (r (1) ) , y (2) ( r (2)The spectral phases of the two antenna arrays 8 and 9, after distance Doppler processing for the selected distance, correspond to the spectral phases for all virtual Tx-Rx pairs in each antenna array 8 and 9. Including measurements with Tx and Rx in different apertures is optional, as down-mixing with a local oscillator other than the one used for transmission is known to increase phase noise.

[0125] For example, soft synchronization can be used between the local oscillators, meaning they are synchronized not to wavelength accuracy, but to the accuracy of their distance spins. This can further include synchronization to the time delay between distance spins; for example, 15 cm corresponds to 15 ns. In contrast, synchronization to the time of a carrier wavelength at 77 GHz is 13 ps. Furthermore, it is not necessary to transmit local oscillator signals between the antenna arrays, as it is much simpler to use independent local oscillators, which are easier to synchronize. The MIMO scheme for avoiding interference between transmitters includes the popular time-division multiplexing technique, which also requires soft synchronization between the antenna arrays.

[0126] Decentralized computation can be performed, meaning within the FPGA of each sensor. This allows the area assignment between the antenna arrays to be provided for each angle hypothesis. Subsequently, the average matched filter can be calculated across all antenna arrays. The front ends have no special requirements. These front ends, i.e., the antenna arrays, can function as sparsely configured arrays.

[0127] Averaging sidelobes can assume that radar target 6 has a similar SMR on both antenna arrays, and sparse array configurations can generate sidelobes that obscure targets with different radar cross-sections. Using the orthogonal matching pursuit can eliminate sidelobes from strong targets. However, the sidelobe level should be reduced in this process.

[0128] Furthermore, the proposed invention can also be used for coherent processing. In this context, a combination with coherent systems that use one or more local oscillators or phase-locked loop modules, electrical or optical, can be considered.

[0129] Other synchronization and quasi-synchronization systems and / or algorithms that enable quasi-coherent processing with estimation of phase matching / inequality in each frame can also be considered. In particular, the discussion shows how a distributed aperture radar system can be used for monostatic and / or bistastatic signal processing, where the individual apertures are positioned unevenly or sparsely relative to each other. This allows the radar system 1 to be used especially in dynamic applications, such as in motor vehicles, trains, aircraft, or ships. Reference symbol list 1 radar system 2 Environment 3 vehicles 4 electronic evaluation units 5 antenna arrays 6 Radar target 7 Direction of travel 8, 9 first and second antenna array 10 transmission signal 11, 12 first and second received signal 13 Orthogonal Matching Pursuit Algorithm 14 Target Information 15 to 17 fields of vision S10 to S90 steps d transmission channel r (1) , r (2) first, second distance information Φ (1) , Φ (2) first, second angle hypothesis Φ angle or azimuth angle n distance θ Polar angle r (1) , r (2) Distance Doppler detection MF (1) , MF (2) first and second optimal filters γ (1) (r (1) ), γ (2) (r (1)) first and second antenna signal

Claims

[1] Method for determining target information of radar targets of a radar system (1), wherein - at least one transmission signal (10) is transmitted into an environment (2) by a first antenna array (8) of the radar system (1), - a first reception signal (11) reflected by a radar target (6) in the environment (2), which is based on the transmitted transmission signal (10), is received by the first antenna array (8), and - a second reception signal (12) reflected by the radar target (6) in the environment (2), which is based on the transmitted transmission signal (10), is received by a second antenna array (9) different from the first antenna array (8), characterized by , that - at least a first distance information item (r1) between the first antenna array (8) and the radar target (6) is determined depending on the transmitted signal (10) and the first received signal (11), - depending on the first distance information (r1) at least one first angle hypothesis (Φ (1) ) is provided for the first antenna array, - based on the first distance information (r1) and the first angle hypothesis (Φ (1) ) with respect to the first antenna array (8) a corresponding second distance information (r2) and a corresponding second angle hypothesis (Φ (2) ) for the second antenna array (9), - Determining a first optimal filter (MF (1) ) based on the first distance information (r1) and the first angle hypothesis (Φ (1) ) and / or a second optimal filter (MF (2) ) based on the second distance information (r1) and the second angle hypothesis (Φ (2) ) and - at least one target information item (14) relating to the radar target (6) based on the first and / or second optimal filter (MF (1) , MF (2) ) is determined. [2] Method according to claim 1, characterized by that the first distance information (r1) is determined on the basis of a fast Fourier transform. [3] Method according to claim 1 or 2, characterized by that the first distance information (r1) is determined on the basis of a constant false alarm rate concerning the first antenna array (8). [4] Method according to one of the preceding claims, characterized by that an extrinsic calibration is carried out on the first and / or second antenna array (8, 9) in order to determine the second distance information (r2) and the second angle hypothesis (Φ (2) ) for the second antenna array (9). [5] Method according to one of claims 1 to 3, characterized bythat it is checked whether the first antenna array (8) is intrinsically calibrated, and if so, then the second antenna array (9) is calibrated on the basis of a cooperative auto-calibration method depending on the calibrated first antenna array (8). [6] Method according to one of the preceding claims, characterized by , that - it is checked whether the determined second angle hypothesis (Φ (2) ) is located within a field of view of the second antenna array (9), and - if the second angle hypothesis (Φ (2) ) is located within the field of view, the at least one target information item (14) is determined on the basis of the first and second optimal filters (MF (1) , MF (2) ) and - if the second angle hypothesis (Φ (2) ) is outside the field of view, the at least one target information (14) is determined on the basis of the first optimal filter (MF (1) ) certainly. [7] Method according to one of the preceding claims, characterized by that a first antenna signal (γ (1) (r1)) of the first antenna array (8) on the basis of the first distance information (r1) and antenna information concerning antenna elements of the first antenna array (8) and a second antenna signal ( γ (2) (r (2) ) of the second antenna array (9) is determined on the basis of the second distance information (r2) and antenna information relating to antenna elements of the second antenna array (9). [8] Method according to claim 7, characterized by , that - the first optimal filter (MF (1) ) of the first antenna array (8) based on the first antenna signal (γ (1)(r1)) and a predetermined model of a spatial region of the first antenna array (8), in particular nominal or calibrated antenna positions and / or phase asymmetries of the first antenna array (8) when determining the first optimal filter (MF (1) ) are taken into account, and - the second optimal filter (MF (2) ) of the second antenna array (9) based on the second antenna signal (γ (2) (r (2) ) and a predetermined model of a spatial region of the second antenna array (9), in particular nominal or calibrated antenna positions and / or phase asymmetries of the second antenna array (9) when determining the second optimal filter (MF (2) ) should be taken into account. [9] Method according to claim 8, characterized by that a near-field vector model or a far-field vector model is provided as a predetermined model of the spatial region of the first and second antenna arrays (8, 9). [10] Method according to one of claims 7 to 9, characterized by that the first antenna signal (γ (1) (r1)) using the first optimal filter (MF (1) ) and the second antenna signal (γ (2) (r2)) using the second optimal filter (MF (2) ) and based on the filtered first and second antenna signals (γ (1) (r1), γ (2) (r2)) the at least one item of target information (14) is determined. [11] Method according to claim 10, characterized by that the at least one item of target information (14) is determined on the basis of an orthogonal matching pursuit algorithm (13). [12] Method according to one of the preceding claims, characterized by that with the at least one target information (14) an angle and / or a direction to the radar target (6) is provided. [13] Radar system (1) with a first antenna array (8), at least one second antenna array (9) and an electronic evaluation unit (4), wherein the radar system (1) is designed to carry out a method according to one of the preceding claims. [14] Radar system (1) according to claim 13, characterized by that the first antenna array (8) and the second antenna array (9) are arranged at a distance from one another. [15] Vehicle (3) with a radar system (1) according to claim 13 or 14.

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