Method for determining target information of a radar system, radar system and vehicle

Abstract

The invention relates to a method for determining target information of a radar target, in which a transmission signal (10) is transmitted with a first antenna array (8) of a radar system (1), a first received signal (11) reflected from the radar target (6) is received with the first antenna array (8), and a second received signal (12) is received with a second antenna array (9), first distance information (r1) is determined, and second distance information (r2) is determined. Second distance information (r2) and a second angle hypothesis (phi (2)) for the second antenna array (9) are determined on the basis of the first distance information (r1) and the first angle hypothesis (phi (1)), a first optimal filter (MF (1)) is determined on the basis of the first distance information (r1) and the first angle hypothesis (phi (1)), and / or a second optimal filter (MF (2)) is determined on the basis of the second distance information (r1) and the second angle hypothesis (phi (2)), and determining target information (14) on the basis of the first and / or second optimal filters (MF (1), MF (2)). The invention also relates to a radar system (1) and a vehicle (3).

Description

Technical Field

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

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

[0003] The invention also relates to a vehicle having a radar system. Background Art

[0004] In highly automated vehicles with a large number of driver assistance systems or vehicle guidance systems, radar information is of great importance, since primarily the assistance systems rely on radar information in order to be able to carry out at least partially autonomous driving maneuvers.

[0005] For example, patent document JP 2005 233 723A discloses a radar device having distributedly arranged antennas. Here, digital data received at a reception time can be extracted by a radar control device. Digital beamforming processing based on position information can be performed based on the transmitted digital data and the received time information to obtain the extracted received digital data. Beam combining can then be performed to thereby identify and display the target.

[0006] In addition, patent document CN 110 412 559A discloses a non-coherent fusion target recognition method for a distributed UAV MIMO radar. In this case, the position of the search base point and the target speed can be set first, wherein a four-dimensional search grid is established with the point as the center, and then the entire search area is crossed to obtain the range Doppler information of the target. On this basis, each receiver of the distributed UAV MIMO radar performs matched filtering on the received echo signal and extracts the echo signals emitted by different platforms.

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

[0008] The object of the present invention is to improve the target acquisition or target detection of a radar system or radar having mutually incoherent antenna elements or antenna arrays and in particular to increase the resolution or angular resolution of the radar system.

[0009] This technical problem is solved according to the method, the radar system and the vehicle according to the invention. Useful further developments are apparent from the description.

[0010] An advantageous embodiment of one aspect may be considered an advantageous embodiment of other or all aspects, and vice versa.

[0011] In particular, the radar system and / or the vehicle have (technical) means for carrying out or executing the method.

[0012] One aspect of the invention relates to a method for determining target information of a radar target of a radar system, wherein:

[0013] - in particular, emitting at least one transmission signal into the environment with a first antenna array of the radar system,

[0014] In particular, receiving with the first antenna array a first reception signal reflected from a radar target in the environment, the first reception signal being based on the transmitted transmission signal, and

[0015] - in particular, receiving with a second antenna array different from the first antenna array a second reception signal reflected from a radar target in the environment, the second reception signal being based on the transmitted transmission signal,

[0016] - in particular, determining at least one first distance information between the first antenna array and the radar target based on the transmission signal and the first reception signal,

[0017] - in particular, providing at least one first angle hypothesis for the first antenna array based on the first distance information,

[0018] - in particular, based on the first distance information and the first angle hypothesis about the first antenna array, determining second distance information corresponding to the first distance information and a second angle hypothesis corresponding to the first angle hypothesis for the second antenna array,

[0019] - in particular, determining a first optimal filter based on the first distance information and the first angle hypothesis, and / or determining a second optimal filter based on the second distance information and the second angle hypothesis, and

[0020] In particular, at least one target information item relating to the radar target is determined based on the first and / or second optimal filter.

[0021] The proposed method can be advantageously used to improve target acquisition of radar or radar systems. In particular, the accuracy of target acquisition or target detection of radar targets, ie, objects in the environment of the radar system, can be increased.

[0022] In the case of radar systems used in the automotive sector, precise, improved but still simple acquisition of objects is necessary, for example. In this case, improved recognition performance, reduced sidelobe ambiguity and a higher angular resolution of the radar system are very important, for example, for lane guidance, execution of overtaking maneuvers or obstacle recognition. This is where the invention is advantageous, and the invention can provide a remedy in this regard.

[0023] In the prior art, bistatic distributed systems and large coherent apertures can be used to improve the angular resolution. However, in this case, the following problems arise, which can be solved by the proposed method.

[0024] A bistatic configuration with coherent processing avoids the need for a common local oscillator by correlating the transmitted signals from the radar system's antennas. However, this propagation channel may be subject to unknown transfer functions due to active elements that may be limited by the field of view. The proposed method does not require large coherent devices. Previous systems required high computational overhead for angle processing, especially when the array geometry is not suitable for processing by Fast Fourier Transform (FFT).

[0025] Another problem that can be solved by the proposed method is that for radar systems with large apertures, the internal calibration of the phase imbalance is sensitive to the angular errors of the calibration target and requires an automatic calibration method. With this automatic calibration method, the phase imbalance of the channel, the antenna position and the angle of the calibration target can be estimated simultaneously, which is a multidimensional problem that is ambiguous and can be unstable to deviations in the parameter model, such as mutual coupling of non-uniform polarizations.

[0026] The problems just mentioned can be solved at least partially, in particular completely, by the proposed method. The proposed method can perform a non-coherent combination of monostatic and bistatic signals. The coupling between the range or distance of the radar target and the angle can improve the determination of target information, such as the angular resolution, by in particular sequential estimation.

[0027] For example, in non-coherent beamforming, the antenna positions in mutually incoherent array apertures can be optimized. This can be achieved by the proposed method. The individual apertures or antenna arrays can be designed very sparsely relative to each other and may have high sidelobes. The sidelobes can be averaged by combining, so that a higher resolution can be obtained with good sidelobe levels. Unlike the prior art, in the case of the present invention, it is not required that the target is identifiable and that it can be correctly distributed between the individual apertures of the antenna array and that it is visible from different apertures with a similar signal-to-noise ratio (SNR). For example, there are systems and algorithms for azimuth and elevation estimation, which use road reflections to improve the elevation resolution, including combining the phases of multiple apertures. For example, improved azimuth estimation can also be performed by the present invention.

[0028] For example, in the present invention, a processing chain with a distance distribution between apertures, i.e., a distance distribution on each individual antenna element of an antenna array, can be provided as a function of an angle hypothesis and a sequential angle estimate. The residual of each distance field can thereby be updated. In addition to radar systems in the automotive field, non-coherent beamforming can also be used in other fields such as aerospace or automation. For example, according to the present invention, at least one target information can be calculated based on a sparse reconstruction algorithm, such as "block orthogonal matching pursuit" (BOMP) or "block nearly orthogonal matching pursuit" (Block-NOMP).

[0029] For example, the proposed method can be used for distributed radar systems with multi-configuration or bistatic configuration. For example, a multipath or multipath method or a bistatic method with coherent phase can be used for the proposed method to improve resolution or resolution. In this case, a combination of one or more radar sensors and one or more transceivers, so-called repeater tags, can be considered or used. In the case of a multiple-input multiple-output (MIMO) sensor and a repeater tag, the repeater tag receives the echo of the target and transmits it back to the receiver of the original sensor following the target path with an amplified frequency shift. The bistatic path can be identified based on the frequency shift. The bistatic path between the sensor and the repeater tag can be kept coherent. A virtual array is generated from it, which keeps the virtual Tx-Rx pair of the sensor together with the virtual repetition (virtuellen Wiederholung) of the transmitter at a distance that depends on the distance of the repeater tag and the angle of the target. Since the length of the combined virtual array matches the distance of the repeater tag, the aperture is increased, so that the resolution can be theoretically improved. The following problems usually occur when using this method, which can be solved by the proposed method.

[0030] The distance between the repeater tag and the sensor must be known with wavelength accuracy. This seems to be achievable for short distances, which can indeed greatly improve the resolution, since a few centimeters may be sufficient. But if the distance is larger, deformations and vibrations may impair the performance of the radar system. A further problem is the gaps in the virtual aperture, since these may lead to high side lobes, which may cause the target to be obscured. It is also problematic that the performance may degrade in the case of many targets, since the bistatic range, even if separated from the monostatic path by a frequency shift, may overlap with the monostatic range of other targets.

[0031] The above-mentioned problem is solved by the proposed method because the proposed method does not perform a correlation (or association) process with a bistatic signal when using a transceiver, and thus the above-mentioned problem can be solved by the proposed method.

[0032] In addition, known distributed systems avoid the use of a common local oscillator by using bistatic signal processing while retaining the phase information, i.e., the signals are coherent, wherein the bistatic feedback of the target is encoded with crosstalk channels, which must be measured in advance to estimate the phase offset. Therefore, the distance between the individual antennas must be measured in advance with wavelength accuracy, and in addition, when the field of view is limited, unknown transfer functions may cause the loss of the propagation channel and the line of sight. These problems can be solved by the present invention. The present invention uses distance-angle coupling to achieve target acquisition or determination of target information even in the case of an incoherent arrangement of the antennas of the radar system. If the combined distance between the individual antennas is greater than the distance caused by the geometric near field or the near field path, the proposed method can be used advantageously here.

[0033] In addition, there are some systems that use standard three-dimensional FFT processing for cascaded adjacent radar systems. However, these systems cannot use separate apertures. This method is mainly used by radar systems with separate or remotely arranged apertures.

[0034] Previous systems use multiple multimodal sensor fusion methods and combine information on the time-varying estimation level, for example by Kalman filtering or particle filtering. In contrast, by the present invention, a combination of spectra across apertures is performed, which spectra are complementary.

[0035] In particular, the proposed method can be a computer-implemented method.

[0036] With the aid of the proposed method, target information of a radar system or radar information of a radar target can be determined, which target information or radar information can be used in particular for a vehicle.

[0037] The radar system may have a plurality of distributed antenna arrays. The antenna array may also be referred to as an aperture or an antenna aperture or an array aperture. The antenna array may be a surface or a predetermined range on which a plurality or a large number of individual antennas or antenna elements are arranged. The antenna array may be used to transmit and receive signals.

[0038] In the environment of the radar system, at least one transmit signal or a transmission signal or multiple transmit signals can be emitted. When at least one of these transmit signals, for example, the at least one transmit signal hits a radar target, such as an object in the environment, the signal is reflected accordingly and reflected in the direction of the radar system. Here, multiple reflected signals can be reflected or emitted or sent back. Here, at least one first receive signal can be received with a first antenna array and at least one second receive signal can be received with a second antenna array. In other words, a signal can be transmitted by means of an antenna array, and the signal can be received by two or more antenna arrays. In this case, the first antenna array experiences a single-base return of the signal because the transmit signal is transmitted and received by the first antenna array. In the case of the second antenna array, a dual-base signal return is achieved because the transmit signal is not, especially not mandatory, transmitted by the second antenna array.

[0039] Based on the monostatic signal return associated with the first antenna array, for example, a first distance information based on the Doppler effect can be determined. The distance information is the distance or range between the first antenna array and the radar target. Likewise, of course, a plurality of transmission signals corresponding to the corresponding plurality of reception signals can be received. Thus, a plurality of radar targets can be analyzed or reflected accordingly.

[0040] Based on the first distance information and thus the first Doppler effect determination, multiple angle hypotheses, i.e. mathematical hypotheses, can be established about the radar target. In particular, at least one angle hypothesis can be established or provided for each distance information determined by the first antenna array. Since the second antenna array only obtains the received signal and does not transmit the corresponding transmission signal, an association process can be performed based on the first distance information and the first angle hypothesis to obtain the corresponding second distance information for the second antenna array. In other words, the distance information between the second antenna array and the radar target is estimated or determined or calculated based on the information related to the first antenna array. Therefore, the second distance information corresponding to the first distance information can be determined. Similarly, the second angle hypothesis corresponding to the first angle hypothesis can also be determined. It can already be seen here what advantages the proposed method brings, because the corresponding distance and angle determination is performed for one antenna array and the distance and angle determination is used for other antenna arrays.

[0041] Therefore, even in the case of non-coherent antenna arrays, target determination can be carried out in the simplest manner by each antenna array, since the corresponding information can be shared.

[0042] An optimum filter, a so-called "matched filter", can be generated or determined for the respective radar information of the first and / or second antenna array and the first and second antenna array, respectively. Thus, a respective optimum filter can be provided for the first antenna array and / or the second antenna array, so that the respective information can be filtered accordingly. For example, a generalization of an average "matched filter" can be realized based on the two optimum filters or the respective optimum filters for all antenna arrays. By means of this average matched filter, for example, target information, such as an angle estimate, can be determined.

[0043] For example, the antenna array can be referred to as an antenna arrangement structure, which is preferably designed as a planar arrangement structure of antennas. The antenna array can be a transmitting antenna and / or a receiving antenna arranged in different ways. In particular, the antenna array can be a sparsely arranged antenna arrangement structure. This is particularly advantageous when the radar system is used in the automotive field, because the antenna array should be arranged in various differently configured areas in or on a vehicle, especially for 360-degree acquisition of the environment of the vehicle.

[0044] In one embodiment, it is provided that the first distance information is determined based on a fast Fourier transform (FFT). Based on the information in the received receive signal, for example, a range Doppler determination can be performed for each antenna array, thereby performing a distance determination based on the Doppler effect. In order to be able to perform particularly efficient calculations here, in particular corresponding mathematical transformations, such as fast Fourier transforms, can be used.

[0045] Other mathematical operations or transformations may also be used.

[0046] False alarm rate (FAR) is an evaluation measure for radar system operation. The echo signal is shown before the background noise when the radar is received. The noise signal has an amplitude distributed statistically, which is consistent with the amplitude of the useful signal and is processed as the amplitude of the useful signal. This may lead to the display of wrong radar targets or targets. The false alarm rate is understood as the average number of false targets that can be determined on the receiver output of the radar system within a specific time, such as every turn of the antenna or every pulse sequence cycle. In the case of the mentioned constant false alarm rate (CFAR), a constant false alarm rate can be mainly adopted or used in the duration or duration of the acquisition or detection of the radar target. The adaptation function of the perceived environmental conditions of the environment of the radar system can be mainly used here. Thus, false alarms or false targets that occur in the close range can be mainly suppressed better. Accordingly, the discovery of the target or the acquisition of the radar target, especially the discovery or acquisition within its range, can be improved by using a constant false alarm rate. Thus, the range of action of the radar system can be mainly improved.

[0047] In one embodiment, it is provided that an external calibration is performed in the case of the first and / or second antenna array in order to determine the second distance information and the second angle hypothesis for the second antenna array based on the external calibration. This needs to be performed because a coordinate transformation or the provision of a common coordinate system related to the first and second antenna arrays is necessary in order to be able to determine the second distance information and the second angle hypothesis of the second antenna array that are consistent or corresponding thereto based on the first distance information and the first angle hypothesis. In order to be able to infer the corresponding information of the second antenna array based on the determined information or data of the first antenna array, it is necessary to use the common coordinate system of the two antenna arrays for calculation. In order to achieve synchronization of the two antenna arrays for calculation, a corresponding calibration is performed. In this case, an internal calibration is performed in particular. In the case of external calibration, the spatial position and orientation of the first and second antenna arrays can be combined into a reference coordinate system. Therefore, the distance information and the angle hypothesis of the first antenna array can be converted to the second antenna array using a common reference coordinate system.

[0048] In one embodiment, it is provided that the first antenna array is checked whether it has been internally calibrated, and if so, the second antenna array is calibrated according to the calibrated first antenna array based on the collaborative automatic calibration method. Internal calibration is understood as mapping the three-dimensional points in the camera coordinate system, that is, the three-dimensional points in the radar system, to the two-dimensional camera sensor, that is, the antenna array. Therefore, for example, it is possible to first check or determine whether the first antenna array is calibrated or uncalibrated. If it has been calibrated, the second antenna array and other antenna arrays of the radar system can be calibrated in the simplest way based on the calibrated first antenna array. In other words, it may be sufficient that an antenna array of the radar system is calibrated and the calibration of other antenna arrays can be performed based on the calibrated, especially the only calibrated receiver array. In order to be able to calibrate other antenna arrays in the simplest way, especially faster, a collaborative automatic calibration method is applied. Therefore, all antenna arrays or at least some antenna arrays of the radar system can be automatically calibrated in an efficient way. This is particularly beneficial to the accuracy of target detection, and is particularly beneficial to the particularly accurate determination of target information related to radar targets.

[0049] The collaborative automatic calibration method can be used primarily in distributed antenna arrays in the automotive field. Depending on the number of antenna arrays present and their location and positioning on or in the vehicle, one antenna array can be calibrated first in the simplest way, and the remaining antenna arrays can be automatically calibrated based on this already calibrated antenna array.

[0050] In one embodiment, it is provided that the determined second angle hypothesis is checked whether it is located within the field of view of the second antenna array, and if the second angle hypothesis is located within the field of view, the at least one target information is determined based on the first and second optimal filters. The area within the viewing angle of the optical device is called the field of view, in which events or changes can be perceived and recorded. With the help of the angle hypothesis, for example, the angle function can be understood. It is mainly possible to use different angles at which the radar target may be positioned relative to the radar in a hypothetical manner with the help of the angle hypothesis. Therefore, the angle of the radar target relative to the radar or the antenna array may be outside its field of view and therefore outside its acquisition range. In other words, the angle hypothesis must be established or theoretically presupposed so that the possible angle hypothesis is located within the field of view, because otherwise the acquisition of the radar target is not feasible. Since the second angle hypothesis is determined based on the first angle hypothesis of the first antenna array, it can be checked for monitoring whether the second angle hypothesis is actually located within the field of view of the second antenna array. If this is the case, at least one target information or multiple target information of the radar target can be determined based on two optimal filters using information related to the first antenna array and the second antenna array. If the second angle hypothesis is located 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 of the first antenna array and in particular based on the first optimal filter.

[0051] In one embodiment, it is provided that based on the first distance information and the antenna information related to the antenna elements of the first antenna array, the first antenna signal of the first antenna array is determined, and based on the second distance information and the antenna information related to the antenna elements of the second antenna array, the second antenna signal of the second antenna array is determined. Based on the corresponding information of the first and second antenna arrays, the corresponding antenna signals can be generated for a further processing chain or a further processing step. The corresponding antenna signals are determined based on the information of the corresponding antenna array. In this case, in addition to the corresponding distance information and antenna information, the corresponding angle assumptions of the antenna array can also be taken into account. In the case of antenna information, mainly information related to the individual antenna elements of the corresponding antenna array, such as the transmitting and / or receiving antennas, can be taken into account. In this case, mainly the virtual transmitting and receiving antennas of the corresponding antenna elements can be taken into account in order to determine the corresponding antenna signals, the transmitting and receiving antennas are also referred to as Tx-Rx pairs (transmitting and receiving elements). With the help of the antenna signals, further processing in terms of determining the target information can be simplified.

[0052] In one embodiment, it is provided that the first optimal filter of the first antenna array is determined based on the first antenna signal and a preset model of the spatial region of the first antenna array. Therefore, an optimal filter or a "matched filter" that is adapted to or consistent with the first antenna array can be generated. Here, a distinction can be made mainly between two situations. Here, a distinction can be made mainly between near-field acquisition and far-field acquisition. In other words, a distinction is made between whether the radar target is in the near field or in the far field. Accordingly, a corresponding preset model, in particular a vector model, which is also called a steering vector model, can be taken into account when determining the optimal filter. Similarly, a second optimal filter can be determined based on the second antenna signal and a preset model of the spatial region of the second antenna array.

[0053] Additionally or alternatively, the nominal or calibrated antenna positions of the individual antenna elements of the first or second antenna array may be taken into account when determining the first and / or second optimal filter and / or a phase asymmetry or phase imbalance of the first or second antenna array may be taken into account in the corresponding determination of the optimal filter.

[0054] In one embodiment, it is provided that a near-field vector model or a far-field vector model is provided as a preset model of the spatial region of the first and second antenna arrays. Thus, depending on whether a near or far radar target is detected with the corresponding antenna array, a model adapted thereto can be provided and in particular used for calculations or determinations.

[0055] The near field is also called the reactive near field and is understood to be the region in the immediate vicinity of an antenna, such as an antenna array. The far field is also called the Fraunhofer region and is the maximum region in which electromagnetic waves can propagate in space as plane waves independently of the antenna.

[0056] In one embodiment, it is provided that the first antenna signal is filtered by a first optimal filter, and the second antenna signal is filtered by a second optimal filter, and the at least one target information is determined based on the filtered first and second antenna signals. In other words, the determined or calculated antenna signal can be filtered accordingly in order to obtain one or more target information, such as the angle of the radar target. In particular, the target information can be used to be able to perform an angle estimation related to the radar target.

[0057] In one embodiment, the at least one target information is determined based on an orthogonal matching pursuit algorithm. An approximation algorithm, in particular a sparse approximation algorithm, can therefore be applied with the aid of the corresponding distance information, angle assumptions and an optimal filter in order to be able to determine the corresponding target information or multiple target information.

[0058] In one embodiment, it is provided that the at least one target information item provides an angle and / or a direction relative to the radar target. In other words, an angle estimation can be performed in particular with the aid of the target information in order to be able to determine the corresponding angle of the radar target relative to the radar system and / or the direction of the radar target. This is particularly important for the acquisition of the vehicle environment.

[0059] A further aspect of the invention relates to a radar system having a first antenna array and a second antenna array and an electronic evaluation unit, wherein the radar system is designed to perform or implement the method according to the above-mentioned aspect or an advantageous development thereof. In particular, the above-mentioned method can be performed by the radar system just mentioned.

[0060] A radar system is in particular an electronic radar device or radar apparatus, by means of which radar targets in the environment can be detected or acquired. The radar system can in particular have a plurality of antenna arrays, which can also be referred to as antenna arrangements. Thus, the radar system can have a large number of distributedly arranged antenna arrays, which can in turn each have a plurality of transmitting elements and receiving elements. Thus, in particular 360-degree acquisition of the surrounding area can be performed by the proposed radar system.

[0061] The electronic analysis unit can be an electronic computing system. In particular, the electronic analysis unit can be designed as a distributed system, wherein at least a part of the analysis unit can be arranged in the corresponding antenna array in order to perform the corresponding preprocessing. The electronic analysis unit can also be designed as a central system, which is connected or coupled to the corresponding antenna array in terms of communication or data technology in order to be able to perform the corresponding analysis on the target information.

[0062] In one embodiment of this further aspect, it is provided that the first antenna array and the second antenna array are arranged at a distance from each other. In particular, the antenna arrays of the radar system are arranged relatively far from each other so that a larger range can be covered with fewer antenna arrays. Even if the antenna arrays of the radar system have uneven and / or unequal antenna distances relative to each other, radar information can be effectively determined by the method according to the aforementioned aspect of the invention. This is particularly advantageous for the use of radar systems in the automotive field, because the antenna arrays can thus be arranged in different areas or positions in and / or on a motor vehicle, so as to be able to perform a particularly 360-degree acquisition of the surrounding area of ​​the motor vehicle.

[0063] A further aspect of the invention relates to a vehicle having a radar system according to the previous aspect or an advantageous extension thereof. The aforementioned radar system can be integrated or installed in particular in the vehicle just mentioned. Thus, the aforementioned radar system can be used for environmental acquisition of the vehicle. This can be particularly advantageously used for driver assistance systems or autonomous systems of the vehicle.

[0064] An advantageous embodiment of one aspect may be considered an advantageous embodiment of other or all aspects, and vice versa.

[0065] In particular, the radar system and / or the vehicle have (technical) means for carrying out or executing the method.

[0066] For application scenarios or use cases that can be derived from the method and are not explicitly described here, provision can be made for outputting a fault message and / or a request for inputting user feedback and / or adjusting standard settings and / or predefined initial states according to the method.

[0067] The present invention also includes an extended design of the radar system according to the present invention and the vehicle according to the present invention, which has the features already described with respect to the extended design of the method according to the present invention. Therefore, the corresponding extended design of the radar system according to the present invention and the vehicle according to the present invention will not be described here.

[0068] The invention also includes combinations of features of the described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] The embodiments of the present invention are described below. In the accompanying drawings:

[0070] Figure 1 An exemplary radar system for use on a vehicle is shown;

[0071] Figure 2 Show Figure 1 Schematic diagram of two antenna arrays of the radar system in the far field;

[0072] Figure 3 and Figure 2 Conversely, the near-field acquisition situation is shown;

[0073] Figure 4 Shown for determining Figure 1 Schematic flow of target information of radar system in;

[0074] Figure 5 Show Figure 4 A continuation of the working principle of the orthogonal matching pursuit algorithm with the addition of the implementation in;

[0075] Figure 6Another exemplary embodiment of determining target information or performing angle estimation of a non-coherent antenna array is shown; and

[0076] Figure 7 based on Figure 1 The corresponding fields of view for different antenna arrays are shown, which overlap each other.

[0077] The embodiments described below are preferred embodiments of the present invention. In these embodiments, the components described are each individual, mutually independently viewable features of the present invention, which also form an expansion of the present invention independently of each other and can therefore also be considered as components of the present invention individually or in a combination different from the combination shown. In addition, the described embodiments can also be supplemented by other features of the present invention that have been described.

[0078] In the figures, functionally identical elements are in each case provided with the same reference symbols. DETAILED DESCRIPTION

[0079] exist Figure 1 , a schematic diagram of a radar system 1 is shown. The radar system 1 can be used in particular for environment acquisition. In this case, radar targets or objects in the environment 2 of the radar system 1 can be acquired or detected. In this embodiment, the radar system 1 can be used in the automotive field. In this case, the radar system 1 is arranged or integrated in a vehicle 3, in particular a motor vehicle. Thus, the environment 2, in this case the vehicle environment, can be acquired with the aid of the radar system 1. This is particularly advantageous for driver assistance systems and in particular for systems for performing at least partially autonomous interventions.

[0080] On the one hand, radar system 1 can have an electronic evaluation unit 4 for processing information, data and / or signals.

[0081] Furthermore, the radar system 1 can have a large number of antenna arrays 5, also called antenna apertures. As in the present exemplary embodiment with regard to the use of the radar system 1 in a vehicle 3, the antenna array 5 is located in the front region of the vehicle 3. Additional antenna arrays 5 can also be arranged in the surrounding body of the vehicle 3.

[0082] The antenna array 5 may be, for example, an antenna arrangement structure, in particular an uneven, sparse antenna arrangement structure. In this case, mainly the antenna distances between the individual antenna arrays 5 may be non-equidistant.

[0083] The antenna array 5 can be, in particular, an antenna arrangement having a large number of individual transmitting and / or receiving antennas.

[0084] For example, a radar target 6, such as an object in the environment 2, may be located or situated in front of the vehicle 3, especially when viewed in the driving direction 7. The radar target 6 may thus be a collision object or an interfering object in relation to the vehicle 3. The radar target needs to be detected as well and efficiently as possible. For this purpose, a radar system 1 according to the invention is used. For example, the distance n between at least one antenna element and the radar target 6 can be determined with the aid of the radar system 1. Furthermore, the azimuth angle Φ can be determined. It is also possible, as in Figure 1 The polar angle θ is determined as shown by way of example in FIG. These are exemplary variables in order to be able to determine the distance, direction and / or angle with respect to vehicle 3 and relative to radar target 6 .

[0085] The radar system 1 according to the invention uses non-coherent combination of monostatic and bistatic radar echoes or radar signals at multiple antenna arrays 5 for target acquisition or target detection of radar targets 6, in particular for determining target information of radar targets 6. For this purpose, a generalization of an averaging “matched filter” is used for the possible subsequent angle estimation, wherein the coupling between distance and angle is taken into account and used.

[0086] exist Figure 2 and Figure 3 Two antenna arrays 8 , 9 , namely a first and a second antenna array 8 , 9 are shown by way of example.

[0087] exist Figure 2 , the far field is shown as a spatial region of the antenna arrays 8, 9. In this case, the radar target 6 is at a relatively large distance from the antenna arrays 8, 9. In this case, at least one transmit signal 10 can be emitted by the first antenna array 8. The emitted transmit signal 10 can hit the radar target 6 or a plurality of other radar targets and be reflected therefrom once or multiple times. Accordingly, at least one first receive signal 11 can be received by the first antenna array 8, and a second receive signal 12 can be received by the second antenna array 9. In this case, the first antenna array 8 is monostatic, since the antenna array 8 both transmits and receives. The second antenna array 9 can be bistatic, since the second antenna array 9 only receives. In this case, the first antenna array 8 can have at least one transmit antenna or transmit element and at least one receive element or receive antenna. The second antenna array 9 can accordingly have at least one receive element. In order to be able to determine the distance and / or angle of the radar target 6 or other radar targets, respectively, a transmission channel d can be formed between the antenna arrays 8, 9.

[0088] The transmission channel d can be, for example, an "eavesdropping or crosstalk propagation channel". Thus, the corresponding Rx and Tx elements of the two antenna arrays 8, 9 can exchange radar information or radar signals. Figure 3 In, with Figure 2The example in , on the other hand, shows the spatial range of the radar system 1 in the near field. In this case, a signal 10 is transmitted and receive signals 11 , 12 are received by the antenna arrays 8 , 9 , respectively.

[0089] In addition, Figure 3 For example, the distances r1, r2 are shown in . This is in particular the distance or distance information between the antenna arrays 8, 9 and the radar target 6. In addition, two angles or angular distances of the antenna arrays 8, 9 relative to the radar target 6 are shown here. In the case of a monostatic signal, the antenna arrays 8, 9 can have the same local oscillator.

[0090] In the case of non-coherent bistatics, different local oscillators can be used. In this case, a "soft" or "gentle" synchronization between the two antenna arrays 8, 9 may be sufficient. In this case, phase noise may occur, since the noise characteristics of different local oscillators may be different. In this case, more virtual apertures can be used.

[0091] In the case of coherent bistatics, crosstalk signals can be mixed in accordance with the two transmissions between the antenna arrays 8, 9. In this case, however, the distance between the two antenna arrays 8, 9 must be predefined or defined with the utmost accuracy.

[0092] In the following Figure 4 Detailed description of a schematic diagram of a process for determining target information relating to radar target 6 according to the present invention is shown in FIG.

[0093] In particular, the invention makes it possible to carry out non-coherent combination of monostatic and bistatic transmission and reception signals on a plurality of antenna arrays 5 using a generalization of an averaging “matched filter”. This can be used in particular for the subsequent angle estimation, in order to be able to provide the angle as target information 14, for example. For this purpose, a soft synchronization of the antenna arrays 5 can be achieved in the order of magnitude of the delay of the range needle, and the bistatic reception signals can be non-coherently integrated or determined using a multiplexing method such as “TDM”, which also requires only soft synchronization.

[0094] First, received receive signals 11, 12 can be digitized in steps S10, S11. Accordingly, processing can be performed in one processing path or processing chain with respect to first antenna array 8 and processing or evaluation can be performed in connection with second antenna array 9 in another processing chain.

[0095] The digitization of the received signals 11, 12 can be performed by an analog-to-digital converter (ADC). First, the distance information r1, r2 can be determined. For example, a conventional two-dimensional FFT can be performed or executed for this purpose. In this case, the ADC data of the respective receivers, i.e., the Rx elements of the corresponding antenna arrays 8, 9 are particularly subjected to a fast Fourier transform. This can in turn be performed in the corresponding optional steps S20 and S21. In this case, the Doppler frequency or "range Doppler frequency" can be mainly determined. This can be performed, for example, for the corresponding antenna array 5.

[0096] In the optional corresponding steps S30 and S31, a constant false alarm rate can be used or preset for each antenna array 8, 9 in order to be able to detect possible targets based on these findings. In this case, the first distance information r1 can be primarily determined. This can also apply to the second distance information r2. In this case, for example, the range Doppler identification r can be determined or provided for each antenna array 8, 9. (1) 、r (2) Possible distance information r1, r2 can be used. In this case, a corresponding detection or identification can be determined for a radar target 6 or for a plurality of radar targets. For example, the range Doppler identification r1 of the first antenna array 8 can be used. (1) and the first angle hypothesis Ф (1) Calculate the corresponding or corresponding range Doppler identification r (2) And here the angle assumption Φ (2) This may be performed primarily for a number of possible angular hypotheses relating to the first antenna array 8 .

[0097] This can be defined, for example, by the following formula:

[0098] (r (2) ,φ (2) )=T(r (1) ,φ (1) )

[0099] In order to assign (or assign corresponding data or information of the first antenna array 8 to the second antenna array 9, the antenna arrays 8 and 9 must be aligned by means of a coordinate transformation T. This can also be referred to as a preliminary external calibration. In addition, the associated angle assumption Φ can be checked in step S40. (2) Is it in the field of view of the second antenna array 9? If this is the case, further processing can be continued. Otherwise, standard processing is performed based on the first antenna array 8, for example, to determine target information.

[0100] The range Doppler identification r(2) may or may not be an identification or target detection, depending on the false alarm rate associated with the second antenna array 9. In this case, the respective situation can be distinguished or taken into account, since the line of sight angle (Aspektwinkel, or aspect angle) in the antenna array 5 may result in a lower "RCS (Radar Cross Section)".

[0101] The respective antenna signals γ of the first and second antenna arrays 8, 9 may be provided (1) (r1),γ (2) (r (2) ) or array signals for further processing. The respective antenna signals or array signals γ of the corresponding antenna arrays 8 and 9 (1) (r1),γ (2) (r (2) ) may be the spectral phases on the Tx-Rx pairs of the corresponding apertures or antenna arrays 8, 9, which are at the corresponding range Doppler identification r (1) 、r (2) is identified or calculated.

[0102] Next, in step S50 , a first optimal filter MF may be determined for the first antenna array 8 . (1) And in step S51, the second optimal filter MF is determined (2) In this case, the optimal filter MF (1) MF (2) To adapt (or adjust) the filter or matched filter, which is adjusted or determined for each antenna array 8, 9, it can be expressed as follows, for example:

[0103] MF (i) (φ (i) ), i = 1, 2,

[0104] These optimal filters can be determined based on nominal or calibrated antenna positions and point symmetry by correlating the antenna signals with near-field or far-field models. This can be achieved by the following formula, where i represents the corresponding antenna array.

[0105] MF (i) (φ (i) )=|(a (i) (φ (i) )) H γ (i) (r (i) )|

[0106] The dependence on the distance can already be included, for example, when using a near-field steering vector model, where this can be described as follows:

[0107] a (i) (φ(i) , r (i) )

[0108] In order to determine the optimal filter MF based on two (1) MF (2) The determined average or summed optimal filter can be used for the angle hypothesis Φ (1) and Φ (2) Determine or calculate. This can be done using the following formula:

[0109]

[0110] Two alternatives are available for applying the average consistent best filter for the corresponding angular hypothesis. In one alternative, a peak may be located at each range Doppler identification r for the second antenna array 9. (1) The angle assumption Φ corresponding to each reference frame (1) , Φ (2) above.

[0111] In another or second alternative, an "orthogonal matching pursuit algorithm" 13 can be used, in particular for determining target information. This algorithm 13 can be an "associated distance-angle-block-orthogonal matching pursuit algorithm" (ARABOMP).

[0112] In particular, the algorithm 13 can be executed iteratively in step S60 . In this case, the strongest targets can be averaged first and an iteration can be executed with the antenna signals, which can be replaced by the residual for each distance.

[0113] In step S60, the averaged optimal filter can be determined again (see Figure 5 ). In the following Figure 5 The detailed procedure for analyzing the second alternative of the average matched filter is described again in FIG. Figure 4 However, step S70 may be performed after step S60. In this case, the residual

[0114]

[0115] can be used. Here, for the respective range Doppler identification r (1) The iteration is performed accordingly. Here, we can first assume for each angle Φ (2) and the associated distances are assumed as follows using the angle φ in the second antenna array 9 (2) .

[0116] (r (2) ,φ (2) )=T(r (1) ,φ(1) )

[0117] The optimal filter with mean adaptation of the residual can be calculated as follows:

[0118]

[0119] In step S71 , the angle of the strongest detected object, for example radar object 6 , can be determined. The following formula can be used for this determination.

[0120]

[0121] In the next step S72, the amplitude can be determined for the found target. These amplitudes can be calculated by orthogonal projection.

[0122] The residuals may be updated in step S73 for the corresponding distance or distance range as follows:

[0123]

[0124]

[0125] If the size of the array signal residual is less than a certain threshold for the corresponding range band, the search for the angle for that range is aborted.

[0126] In step S74 , k+1 iterations can be performed again. In order to be able to efficiently determine radar target 6 and in particular target information, such as the corresponding angle, it can be checked whether first antenna array 8 is already internally calibrated.

[0127] Further embodiments will be described below.

[0128] If the first antenna array 8 is internally calibrated and the second antenna array 9 is not internally calibrated, for example, a collaborative internal autocalibration method can optionally be used, wherein either the first antenna array 8 provides the 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 in the case of the radar target 6 can be described as follows:

[0129] φ(1), ψ(2)=argmaxMF(1)(φ(1))+|(D(ψ(2))a(2)(φ(2))) H γ(2)(r(2))|Here, a( 2 )(φ( 2 )) can contain either far-field or near-field steering vector models, and D(ψ( 2 )) is defined as follows with respect to the phase asymmetry of the Tx and Rx channels:

[0130]

[0131]

[0132] It should be noted here that in φ (1) The optimization on φ is sufficient, because (2) According to the following target association is φ (1) Function

[0133] (r (2) ,φ (2) )=T(r (1) ,φ (1) ).

[0134] In the case of a small calibrated antenna array and a large uncalibrated antenna array, the possible advantages of collaborative calibration are realized at least in controlled scenarios or controlled situations, where the same target group shares a distance field and the corresponding distance field in the other antenna array. Considering the combination of an antenna array 5 consisting of a large array of larger products with transmit-receive elements and a small antenna array, the large antenna array benefits from the measurement, but the resolution is too high because it may be very sensitive to the DOA estimate (angle estimate). In the case of known positions, the joint estimation of the phase and angle of the smaller array can be more easily implemented. The average matched filter (i.e. the average value of the angle spectrum) benefits from the lower sensitivity to the angle estimate due to the average resolution. That is, the adaptation angle of the small antenna array acts like a smoother or regulator. This may have advantages over simply transferring the previous estimate.

[0135] When a large antenna array observes or detects two or more targets due to resolution, the smoothing effect helps to automatically group these targets, which also facilitates angle estimation and thus in particular at least phase estimation, while the optional estimation of the antenna position of each individual antenna element is the result of a large number of measurements. An additional advantage compared to amplitude tapering is that the average matched filter does not experience SNR losses as in tapering and benefits from a calibrated antenna array.

[0136] As described above, different steering vector models may be used. The following formula describes the array steering vector model for a corresponding antenna array, where, for simplicity, the super index a=a (i) Omitted for better understanding.

[0137] The following describes the steering vector model in the near field, that is, in the spherical wavefront. In the near field, for the receiving range {p i =[x i ,y i , z i The receiver located at angle φ, θ and distance r within ]} generates the receive control vector:

[0138]

[0139] Here you can use

[0140] n:=[cos(θ)cos(φ), cos(θ)sin(φ), sin(θ)]

[0141] Preset target direction. Due to the reciprocity of transmission and reception, the transmission control vector

[0142] a Tx (φ,θ,r)

[0143] Similar to the launch position.

[0144] The array signal model for a virtual Tx-Rx pair is defined as follows:

[0145]

[0146] in, Refers to the Kronecker product.

[0147] In a bistatic scenario, where the transmitter and the receiver, i.e. the transmitting element and the receiving element of the antenna array 5, are located in different antenna arrays, the reference system can be related to the transformation in the external calibration. In the case where the transmitter is located in the first antenna array 8 and the receiver is located in the second antenna array 9, this can be described, for example, as follows:

[0148] in,

[0149] Applicable (r (2) ,φ (2) ,θ (2) )=T(r (1) ,φ (1) ,θ (2) ).

[0150] The following describes the far-field control vector model, that is, the control vector model in a plane wavefront. In the far field, the control vector or array signal is simplified to

[0151]

[0152] In the single-base case, the combined steering vector for transmit and receive is defined as follows:

[0153]

[0154] in, Among them, Kronecker and

[0155] In the bistatic case, the plane wavefront is considered from the point of view of each antenna array and the internal calibration transform can be related as in the near-field case.

[0156] exist Figure 6 The method according to the invention is described elsewhere in .

[0157] First, the distance information r can be determined in step S80. (1) or range Doppler identification (1) In this case, it is possible to check whether the range Doppler recognition or target detection of the second antenna array 9 is consistent with that of the first antenna array 8, for example, whether the condition r is met. (1) (1) =r (2) (1) . Next, it can be distinguished whether it is a near-field acquisition or a far-field acquisition. In step S81, processing is performed with respect to the near-field information, and in step S82, processing is performed with respect to the far-field. After step S81, it can be determined in step S82 that the second antenna array 9 has a different "range pin" than the first antenna array 8. This may also not exist, so that in step S83, it can be aborted. If the second antenna array 9 has the same "range pin" as the antenna 1, the condition r can be used. (1) (2) =r (2) (2) This can be done in step S84. Next, the SNR can be amplified again in step S85 and further calculated using algorithm 13.

[0158] If step S82 is to be used, i.e. the far field, then, for example, a check can be made in step S86 whether the distance information of the first antenna array 8 and the second antenna array 9 are identical. If this is the case, the sidelobe suppression can be improved in step S88, since the second antenna array 9 has also identified the radar target 6 and possibly further targets. If it is determined in step S87 that the distance information of the two antenna arrays 8, 9 is identical, then the SNR can be increased in step S89 and the execution of the algorithm 13 can be started or continued.

[0159] In other words, if a radar target 6 or multiple radar targets are detected in each antenna array 8, 9 and therefore have the same range information, they can be removed from the range information or range field using the ARA-BOMP method of finding the strongest target. Precisely because of the residual update, the masking of the side lobes can be reduced and the resolution can be improved accordingly. It should be noted that a common range of distances and a common far angle may occur when these targets are symmetrically located above and / or behind one antenna array relative to the other antenna array.

[0160] In the following Figure 7 3 is shown again in FIG. Here, different visibility ranges 15, 16, 17 are shown for different antenna arrays 5. The antenna arrays 5 are arranged so that the visibility ranges or fields of view 15 to 17 overlap in each case, so that the largest possible range can be covered with the sensor. In this case, each field of view 15 to 17 can be set for different angles or angle assumptions.

[0161] In particular, an internal calibration can then be performed with the aid of a calibration target before the corresponding radar operation for target detection or target acquisition in order to carry out a coordinate transformation between the reference systems of the antenna array 5. In this case, a possibly unknown relative position orientation of the antenna array 5 can be taken into account due to manufacturing or assembly tolerances. One advantage is that the coordinate transformation does not require wavelength accuracy, since the information is combined at the spectral or absolutely supported filter level. The transformation T is only calculated once, but then it is calculated for the range needle or for each antenna array 5. For simplicity, the transformation is expressed in polar coordinates, e.g.

[0162] (r (2) ,φ (2) )=T(r (1) ,φ (1) ).

[0163] In addition, however, the adjustment can also be carried out in Cartesian coordinates.

[0164] If coupling between antenna arrays 5 does not occur within each antenna array 5, the described methods for target detection or target information determination are applicable to any two-dimensional and three-dimensional geometry. Far field or near field model a (1) a (2) Can be considered or used.

[0165] However, for uniform arrays or antenna arrays 5 or antenna arrays with special symmetry, standard smoothing methods can be used to perform decorrelation on the target.

[0166] It should also be noted that the signal γ of the two antenna arrays 8, 9 (1) (r (1) ), γ (2) (r (2) ) matches the spectral phase after range Doppler processing for the selected range for all virtual Tx-Rx pairs in each antenna array 8, 9. Optionally, measurements using Tx and Rx in different apertures are included, since down-mixing performed by a different local oscillator as the one used for transmission is known to increase phase noise.

[0167] For example, a gentle synchronization (soft synchronization) can be performed between local oscillators, that is, they are not synchronized according to the wavelength accuracy, but synchronized according to the accuracy of the range pin. In addition, the synchronization can be based on the time delay between the range pins, that is, for example, 15cm corresponds to 15ns. In contrast, the synchronization according to the time of the carrier wavelength at 77GHz is 13ps. In addition, there is no need to transmit local oscillator signals between the antenna arrays 5, because it is much easier to use independent local oscillators that can be synchronized more easily. Multiple-input multiple-output schemes for avoiding interference between transmitters include commonly used time-division multiplexing methods, which also require soft synchronization between antenna arrays.

[0168] The calculation can be performed decentralized, i.e. in the FPGA of each sensor. Here, a range correspondence configuration between the antenna arrays can be provided for each angle hypothesis. Then, the average compensation filter can be calculated over all antenna arrays. There are no special requirements for the front end. Here, these front ends, i.e. the antenna arrays, can function as sparsely designed arrays.

[0169] The prerequisite for averaging the side lobes can be that the radar target 6 has a similar SNR on the two antenna arrays and that an array configuration that is too sparse may produce side lobes that cause targets with different radar cross-sections to be obscured. By using orthogonal matching pursuit, the side lobes of strong targets can be eliminated. However, the side lobe level should be reduced.

[0170] Furthermore, the proposed invention can also be used for coherent processing. Thus, a combination with a coherent system using one or more local oscillators or phase adjustment loop modules either electrically or optically is conceivable.

[0171] Other synchronization systems, quasi-synchronous systems and / or algorithms are also conceivable, which enable quasi-coherent processing with an estimation of the phase match / imbalance in each frame. These embodiments show in particular how a radar system with a distributed aperture can be used for monostatic and / or bistatic signal processing, wherein the individual apertures are positioned unevenly or sparsely relative to one another. As a result, the radar system 1 can be used in particular for dynamic applications, for example for motor vehicles, trains, aircraft or ships.

[0172] Reference numerals list

[0173] 1 Radar system

[0174] 2 Environment

[0175] 3. Transportation

[0176] 4 Electronic analysis unit

[0177] 5 Antenna Array

[0178] 6 Radar Targets

[0179] 7 Driving direction

[0180] 8.9 First and second antenna arrays

[0181] 10 Transmitting a signal

[0182] 11, 12 First and second received signals

[0183] 13 Orthogonal Matching Pursuit Algorithm

[0184] 14 Target Information

[0185] 15 to 17 Field of view

[0186] Steps S10 to S89

[0187] d Transmission channel

[0188] r (1) 、r (2) First and second distance information

[0189] Ф (1) , Ф (2) First and second perspective assumptions

[0190] Ф Angle or azimuth

[0191] Distance

[0192] θ Polar angle

[0193] r (1) 、r (2) Range Doppler Identification

[0194] MF (1) MF (2) First and second best filters

[0195] γ (1) (r (1) ), γ (2) (r (1) ) First and second antenna signals

Claims

1. A method for determining target information of a radar target of a radar system (1), wherein: - emitting at least one transmission signal (10) into the environment (2) using a first antenna array (8) of the radar system (1), - receiving with the first antenna array (8) a first received signal (11) reflected from a radar target (6) in the environment (2), the first received signal being based on the transmitted transmit signal (10), and - receiving a second receive signal (12) reflected from a radar target (6) in the environment (2) with a second antenna array (9) different from the first antenna array (8), the second receive signal being based on the transmitted transmit signal (10), It is characterized in that - determining at least one first distance information (r1) between the first antenna array (8) and the radar target (6) based on the transmission signal (10) and the first reception signal (11), - providing at least one first angle hypothesis (φ) for the first antenna array according to the first distance information (r1); (1) ), - Based on the first distance information (r1) about the first antenna array (8) and the first angle hypothesis (Φ (1) ), determining second distance information (r2) corresponding to the first distance information and a second angle hypothesis (φ) corresponding to the first angle hypothesis for the second antenna array (9) (2) ), -Based on the first distance information (r1) and the first angle hypothesis (Ф (1) ) determines the first optimal filter (MF (1) ), and / or based on the second distance information (r1) and the second angle hypothesis (Ф (2) ) determines the second best filter (MF (2) ),and - Based on the first and / or second best filter (MF (1) MF (2) ) determines at least one target information (14) related to the radar target (6).

2. The method according to claim 1, It is characterized in that The first distance information (r1) is determined based on a fast Fourier transform.

3. The method according to claim 1 or 2, It is characterized in that The first distance information (r1) is determined based on a constant false alarm rate associated with the first antenna array (8).

4. The method according to any one of the preceding claims, It is characterized in that An external calibration is performed in the case of the first and / or second antenna array (8, 9) in order to determine second distance information (r2) and a second angle hypothesis (φ) for the second antenna array (9) based on the external calibration. (2) ).

5. The method according to any one of claims 1 to 3, It is characterized in that It is checked whether the first antenna array (8) is already internally calibrated, and if so, the second antenna array (9) is calibrated according to the calibrated first antenna array (8) based on a collaborative automatic calibration method.

6. The method according to any one of the preceding claims, It is characterized in that - Check the determined second angle hypothesis (Ф (2) ) is located within the field of view of the second antenna array (9), and - If the second angle assumption (Ф (2) ) is located within the field of view, then based on the first and second best filters (MF (1) MF (2) ) determines the at least one target information (14), and - If the second angle assumption (Ф (2) ) is outside the field of view, then based on the first best filter (MF (1) ) determine at least one target information (14).

7. The method according to any one of the preceding claims, It is characterized in that Based on the first distance information (r1) and the antenna information related to the antenna elements of the first antenna array (8), a first antenna signal (γ) of the first antenna array (8) is determined. (1) (r1)), and based on the second distance information (r2) and the antenna information related to the antenna elements of the second antenna array (9), determine the second antenna signal (γ) of the second antenna array (9) (2) (r (2) ).

8. The method according to claim 7, It is characterized in that Based on the first antenna signal (γ (1) (r1)) and a preset model of the spatial region of the first antenna array (8), determining a first optimal filter (MF) of the first antenna array (8) (1) ), in determining the first optimal filter (MF (1) ), in particular taking into account the nominal or calibrated antenna positions and / or phase asymmetries of the first antenna array (8), and -Based on the second antenna signal (γ (2) (r (2) ) and a preset model of the spatial region of the second antenna array (9), determining a second optimal filter (MF) of the second antenna array (9) (2) ), in determining the second best filter (MF (2) ), in particular the nominal or calibrated antenna positions and / or phase asymmetries of the second antenna array (9) are taken into account.

9. The method according to claim 8, It is characterized in that A near-field vector model or a far-field vector model is provided as a preset model of the spatial region of the first and second antenna arrays (8, 9).

10. The method according to any one of claims 7 to 9, It is characterized in that Through the first optimal filter (MF (1) ) for the first antenna signal (γ (1) (r1)) and filtered by the second best filter (MF (2) ) for the second antenna signal (γ (2) (r2)) is filtered, and based on the filtered first and second antenna signals (γ (1) (r1),γ (2) (r2)) determining the at least one target information (14).

11. The method according to claim 10, It is characterized in that The at least one target information (14) is determined based on an orthogonal matching pursuit algorithm (13).

12. The method according to any one of the preceding claims, It is characterized in that The at least one target information item (14) provides an angle and / or a direction relative to the radar target (6).

13. A radar system (1) comprising 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 the method according to one of the preceding claims.

14. The radar system (1) according to claim 13, It is characterized in that The first antenna array (8) and the second antenna array (9) are arranged at a distance from each other.

15. A vehicle (3) having a radar system (1) according to claim 13 or 14.

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