Method for controlling a coherent cooperative radar sensor network

Abstract

The invention relates to a method for controlling a coherent cooperative radar sensor network comprising a plurality of radar sensors (11, 12, 13), wherein at least two sensors (12, 13) operate coherently. The sensor data (SD1, SD2, SD3) are divided, according to the type of evaluation, into data (KD) to be evaluated coherently and data (NKD) to be evaluated non-coherently. The data (KD) to be evaluated coherently and the data (NKD) to be evaluated non-coherently are communicated to respectively different evaluation units (110, 120, 130; 31, 32, 33), each of which then carries out an evaluation. The individual evaluations are combined to form an overall evaluation.

Description

[0001]R. 402737 - 1 - Description Title Method for controlling a coherent cooperative radar sensor network The present invention relates to a method for controlling a coherent cooperative radar sensor network. Furthermore, the invention relates to a coherent cooperative radar sensor network which carries out the method. State of the art DE 102015224787 A1 describes a coherent cooperative radar sensor network comprising at least two radar sensors. The radar sensors are synchronized with one another, either by exchanging data or via a signal. Each radar sensor transmits information about the radar signals to a processing device. The processing device can be embodied externally or integrated into one of the radar sensors. The processing device processes the received information and preferably determines both bistatic and monostatic distances to an object.DE 102019220238 A1 discloses a coherent cooperative radar sensor network comprising at least two radar sensors and a method for calibrating it. A phase control signal is transmitted between the radar sensors, and a radar signal is sent based on the phase control signal. An evaluation unit evaluates the signals received from the radar sensors. The radar signals are conventionally evaluated centrally in an evaluation unit. This applies to both coherent and non-coherent data. The evaluation unit can also be part of a radar sensor, to which the data from the remaining radar sensors is then sent. R. 402737 - 2 - For a non-coherent radar sensor network, it is also known to evaluate the non-coherent data decentrally in the radar sensors. Disclosure of the Invention A method for controlling a coherent cooperative radar sensor network is proposed.The coherent cooperative radar sensor network comprises several interconnected and interacting radar sensors. At least two sensors, and preferably all sensors, operate coherently. However, non-coherent cooperative sensors can also be provided. The sensor data to be evaluated is divided into different evaluation units. The evaluation units can be physical computing devices or processors, or they can be implemented as virtual cores or software blocks. The sensor data is divided according to the evaluation type into data to be evaluated coherently (hereinafter also referred to as coherent data) and data to be evaluated non-coherently (hereinafter also referred to as non-coherent data). For this purpose, a calculation of the (two-dimensional) spectrum is preferably carried out. The division is then based on the spectrum.This involves identifying areas that are advantageously evaluated coherently or non-coherently. The complex spectral samples are then distributed according to the areas. With a frequency-modulated continuous wave radar (FMCW), the distribution can also be achieved by filtering based on a time signal. The coherent data is obtained from high-pass filtering, and the non-coherent data is obtained from low-pass filtering. The data to be evaluated coherently and the data to be evaluated non-coherently are each transmitted to different evaluation units. The data is then available to the evaluation units, which then each evaluate their own data. The non-coherent data is thus evaluated by at least one evaluation unit, and the coherent data is evaluated separately by at least one other evaluation unit.The individual evaluations are then combined into an overall evaluation, which is carried out in an evaluation unit. R. 402737 - 3 - By splitting the data up, the computing effort is distributed across several evaluation units, and the individual evaluations can be carried out in parallel, so that the respective evaluation units require less computing power or the overall performance increases. When evaluating the non-coherent data, for example, the vector velocity is recorded and / or a common target list is created (location aggregation). When evaluating the coherent data, phase and / or frequency synchronization can be carried out via the antenna array and / or an angle estimation can be carried out. Reference is made to DE 102019220238 A1 for this purpose. The evaluation units are preferably assigned to the data based on the expected computing effort orthe expected computing power required for the data of the respective evaluation type in order to balance the computing effort required to evaluate the respective data set across the evaluation units. For example, the evaluation of coherent data requires more computing power than the evaluation of non-coherent data. Accordingly, in particular the number of evaluation units and / or the computing power of the evaluation unit is preferably selected depending on the evaluation type. Preferably, the divided data have the same data volumes in order to achieve a constant data rate. This is particularly relevant with multiple cooperative sensors (e.g., four or more sensors). Here, the coherent portion and / or the non-coherent portion could be further subdivided. Preferably, the threshold values ​​are dynamically adapted to the data.During the overall evaluation, the data from the individual evaluations for each target are combined in one evaluation unit. This means that all antenna combinations of the transmit and receive antennas of all sensors are ultimately evaluated together, which is necessary, for example, for cooperative angle calculation. R. 402737 - 4 - Further divisions of the sensor data to be evaluated can be provided. The sensor data can be divided according to one or more of the following criteria for the radar signal used: ^ Distance ranges – a distance threshold can be specified here for the division; ^ Doppler / speed ranges – the speed can be determined from the Doppler shift, therefore either the Doppler shift can be used directly as a criterion or a speed threshold can be specified; and ^ Angle ranges. The criteria represent meaningful cutting planes for the sensor data.Combinations of the criteria for the division can also be used. In particular, the division into coherent and non-coherent data and the division into distance ranges can be advantageously combined, since coherent angle evaluation can only be meaningfully carried out above a certain distance, where the assumption for the far field applies. The mentioned threshold values ​​can be optimized depending on the data rate, computing power, arithmetic operations, etc. Preferably, the common separation plane is determined before the information exchange. For this purpose, a handshake protocol between the sensors can be used, for example. As an example, the smallest threshold value can always be used for the division. Preferably, the sections have the same data volumes in order to achieve a constant data rate. This is particularly relevant if the division results in certain areas containing more targets than others.Preferably, the threshold values ​​are dynamically adapted to the data. The data for the different criteria are then transmitted to different evaluation units. The evaluation units then each carry out an evaluation of their data. The individual evaluations are then combined into an overall evaluation, which is carried out in one evaluation unit. By splitting the data, the computing effort is distributed among several evaluation units and the individual evaluations can be carried out in parallel, so that the respective evaluation units require less computing power. R. 402737 - 5 - To split the sensor data, it can be transmitted to a data distribution unit. The data distribution unit splits the sensor data as described above and then distributes it accordingly to the evaluation units. The data distribution unit can be part of one or more of the sensors or can be designed as a standalone unit.Nowadays, radar sensors often already have evaluation units. In particular, the data can be distributed to the evaluation units in the radar sensors. The data distribution unit mentioned above is preferably used for this. A bidirectional connection to the sensors is then required. The evaluation units in the radar sensors then evaluate their data. This has the advantage that no central computing device is necessary, since the evaluation can be carried out directly in the radar sensors. Furthermore, the overall data rate between the evaluation units is reduced compared to central evaluation. Part of the data remains in the sensor or in its evaluation unit until it has been fully evaluated. With the same data load between N evaluation units, the following relationship applies to the data rate in both cases: As an example, for three sensors, the total data rate is reduced by one-third compared to a centralized evaluation. Since the data in the radar sensor evaluation units can only be discarded or overwritten after complete exchange, a data buffer is preferably provided. For a uniform data volume D sensor data, the size of the buffer DPuffer can be estimated using the following relationship: 1 D Puffer = DN SensordatenAs an example, for three evaluation units, the size of the buffer is reduced to at least 1 / 3 compared to a central evaluation unit. R. 402737 - 6 - Buffering can also take place in the aforementioned data distribution unit in addition to data division. Alternatively or additionally, a central computing device with multiple evaluation units can be provided. The data is transmitted to the central computing device and there divided among the various evaluation units. The division can be performed by the aforementioned data distribution unit, which can also be implemented in one or more of the sensors, as a separate unit, or as part of the central computing device. The multiple evaluation units within the central computing device then evaluate their data. The data from each sensor can be evaluated separately, down to an angle estimate.In particular, the multiple evaluation units are implemented as different processors of the computing device, as virtual cores, or as software blocks. Preferably, the evaluation units of the central computing device access a central memory so that the data is available to each evaluation unit. Alternatively, a memory can be provided for each evaluation unit or for a group of evaluation units. If both evaluation units are present in the sensors and a central computing device with multiple evaluation units, it is preferably provided that the sensor data to be evaluated non-coherently is transmitted to the evaluation unit of the non-coherent radar sensor, since this requires less computing power. The sensor data to be evaluated coherently can then be transmitted to the central computing device, whose more powerful evaluation units perform the evaluation with greater computing effort.According to one aspect, the sensor data can be transmitted as raw data from the sensors. This allows the use of simple sensor heads that provide raw data, e.g., analog-to-digital converter data. Optionally, this raw data can be decimated before transmission. Alternatively, Fourier-transformed data, such as range FFT data, Doppler FFT data, and / or range Doppler FFT data, can be transmitted. This allows the use of simple and cost-effective radar sensors that do not require a preprocessing unit for raw data and a simple preprocessing unit that performs the Fourier transformation R. 402737 - 7 - for Fourier-transformed data. If a central computing device is available for the evaluation, the radar sensors do not need an evaluation unit either. Furthermore, all information for all targets is transmitted via the raw data or the Fourier-transformed data.While this results in a high data rate during transmission, it does not result in any loss of information. If only raw data is transmitted, measures that typically occur during preprocessing, such as range and / or Doppler analysis using fast Fourier transformation, can be performed during the evaluation. During the overall evaluation, a non-coherent integration (NCI) based on multiple sensors can be performed. The NCI calculation can be performed for both coherent and non-coherent data. Preferably, a joint NCI calculation is performed for targets with far-field conditions, as it can be assumed that these targets can be detected by multiple sensors in the same distance-velocity cell. For the short-range (non-coherent range), the NCI calculation is preferably performed based on the data from the individual sensors or the bistatic measurements individually.With individual evaluation, there is a risk that targets may not be detected by the individual sensor. Before the data is finally discarded, the missing targets from individual sensors or bistatic measurements can be subsequently detected by the central NCI calculation. This results in a higher integration gain for downstream target detection, e.g., using a constant false alarm rate (CFAR), compared to individual evaluation. As a result, the sensitivity and range of the cooperative sensor network are increased. Finally, further signal processing steps typical for the respective data type, such as angle evaluation and / or velocity evaluation, and non-coherent processing steps (e.g., determining a vector velocity and / or creating a common target list) are performed based on the multiple or individual sensors.The signal processing steps have the same names for coherent and non-coherent evaluation, but are carried out differently. Preferably, the angle evaluation for the coherent data can be performed based on all sensors; for non-coherent data, the angle evaluation can be performed based on the individual sensor data. Preferably, the speed evaluation for the coherent data can be performed in the conventional R. 402737 - 8 - manner; for the non-coherent data, the speed evaluation can be supplemented by a vectorial speed evaluation. This represents an additional evaluation result. The combined result can be output, for example, in the form of a target list. According to a further aspect, the sensor data can be preprocessed in the sensors before it is transmitted.For this purpose, a preprocessing unit can be provided in the sensors, or the evaluation unit described above can be used in the sensors. The preprocessed sensor data is then transmitted and divided and evaluated as described above. According to a further aspect, the sensor data can be transmitted to the evaluation units. The evaluation unit can be integrated into the sensors or embodied in a central computing device. The preprocessing is then performed in the evaluation units. Preferably, the sensor data is preprocessed in the evaluation units, where the evaluation also takes place. Alternatively, the preprocessed sensor data can be transmitted and divided as described above.In one type of preprocessing, a range and / or Doppler analysis is carried out in each sensor or in each evaluation unit, for example using a fast Fourier transform (FFT) or a discrete Fourier transform (DFT). Furthermore, an adapted analysis with a constant false alarm rate (CFAR) is carried out in each sensor using this data, thus enabling targets to be detected. With adapted CFAR, a higher false alarm rate is used than with conventional methods. The higher false alarm rate means that comparatively more targets are detected. The higher false alarm rate should be chosen so that as many targets as possible are detected, so that no information about targets in the scene detected by the sensors is discarded. The preprocessed sensor data is then transmitted.The data rate for transmitting preprocessed data is thereby reduced by a multiple of, for example, a factor of 10 compared to transmitting raw data. R. 402737 - 9 - For the overall evaluation, an evaluation with a lower constant false alarm rate is advantageously carried out on the basis of all sensors. The term "lower" refers here to the comparison with the CFAR described above. The usual parameterizations are preferably used for this CFAR. This means that the common targets are recorded in the usual way. In addition, a non-coherent integration (NCI) can be carried out on the basis of several sensors in the spectral ranges in which data was transmitted by more than one sensor, as described above. This achieves a significantly higher integration gain compared to individual evaluation.Finally, as described above, further signal processing steps typical for the respective data type, such as angle evaluation and / or velocity determination and non-coherent processing steps (e.g., determination of a vector velocity and / or creation of a common target list) are carried out based on the multiple or individual sensors. During preprocessing, each sensor or evaluation unit independently decides which data to discard. This means that some of the sensors may not transmit any sensor data. However, angle determination with incomplete data is detrimental to the overall evaluation of the coherent cooperative radar network. Preferably, a quality criterion is introduced to decide whether targets detected by only some of the radar sensors are evaluated. Such a quality criterion could, for example, be a majority decision of the sensors.If the quality criterion is met, the partially detected targets are evaluated. In this case, it can be provided that the angle evaluation is only carried out with a subset of the radar sensors. For the evaluation of the non-coherent data, the targets can be aggregated. With a further type of preprocessing of the sensor data, a range and Doppler evaluation is carried out in each sensor or in each evaluation unit. Then, a complete evaluation with a constant false alarm rate is carried out in each sensor or in each evaluation unit. The usual parameterizations are preferably used for this CFAR. This means that the common targets are detected in the usual form. In this case, targets with a lower CFAR can be discarded compared to the raw data and the R. 402737 - 10 - evaluation.In addition, a peak search can be performed and, if necessary, neighboring regions of the peak values ​​can also be transmitted, preprocessed and / or evaluated. Furthermore, an angle estimate is performed in each sensor or in each evaluation unit based on the sensor data of the individual sensors and / or the bistatic measurement paths. This yields a roughly estimated angle. The result of this preprocessing is saved in a target list, which also contains phase information. This additional information relates to the relative phase positions of the individual transmitter-receiver antenna channels for each target and is available as a complex amplitude of all virtual channels. The target list with the phase information is transmitted as preprocessed sensor data. During the overall evaluation, the target lists of the individual sensors or the individual evaluation units can be combined.In addition, CFAR and / or peak detection can be performed again to reduce the data volume. If multiple preprocessed sensor data provide the same target (e.g., the same range and Doppler data, and possibly also the same angles or angular ranges), a cooperative angle estimation can be performed based on the target lists. As a result, the computational effort for the overall evaluation and, ideally, for the evaluation of the coherent data is significantly reduced. The data rate for transmitting the preprocessed data is thus reduced by a factor of several times compared to transmitting raw data, for example, by a factor of 1000. When evaluating the individual sensors and subsequent cooperative evaluation, the cooperative integration gain before CFAR is comparatively small.Finally, as described above, further signal processing steps typical for the respective data type are carried out on the basis of the individual or multiple sensors. The roughly estimated angle obtained in the preprocessing described above can be determined more precisely during the overall evaluation by means of refinement, since relative phase positions of the transmit-receive antenna channels are present in all target lists. For this purpose, a coherent cooperative angle estimation is carried out in a definable range around the at least one estimated angle with a higher angular resolution. This can be done, for example, using fast Fourier transformation or a Bartlett estimator or a maximum likelihood method. Since the angular range in which the higher angular resolution is applied is severely restricted, e.g.Within the separation capability of the individual sensors in elevation and azimuth, the computational effort for this evaluation is comparable to a conventional angle estimation of a single sensor across the entire angular range. This evaluation can, in particular, also find and separate multiple targets within the angular range. Normally, the result of this angle estimation can replace the rough angle estimate of the sensors or the evaluation units. If a quality value of the cooperative evaluation is undershot, the angle estimate of the individual sensors or the evaluation units can be used. The quality value can, for example, be obtained as a result of the correlation between a control matrix and the complex amplitude. For this purpose, meta-information about the type of processing can be appended to the target list.The computer program is configured to perform each step of the method, particularly when performed on a computing device. It enables implementation of the method in a conventional computing device without requiring structural modifications. For this purpose, it is stored on the machine-readable storage medium. Furthermore, a coherent cooperative radar sensor network is proposed, which comprises a plurality of radar sensors. At least two sensors operate coherently. Furthermore, the radar sensor network comprises a data distribution unit with which sensor data can be distributed. The data distribution unit can be part of one or more of the sensors. The radar network is configured to perform the steps of the method described above. Furthermore, the coherent cooperative radar sensor network can comprise a central computing device.The central computing device is configured to carry out the steps of the method described above. For this purpose, the central computing device can have the data distribution unit. R. 402737 - 12 - Brief description of the drawings Exemplary embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Figure 1 shows a schematic diagram of the data and its division. Figure 2 shows a systematic representation of a coherent cooperative radar sensor network according to one embodiment of the invention. Figure 3 shows a systematic representation of a coherent cooperative radar sensor network according to a further embodiment of the invention. Figure 4 shows an angle diagram of the azimuth and elevation angles for estimating the angle of a target. Exemplary embodiments of the invention Figure 1 shows the basic idea of ​​the method according to the invention in a schematic diagram of data.Figures 2 and 3 each show a coherent cooperative radar sensor network with multiple radar sensors (three of which are shown) 11, 12, 13. In this example, a first radar sensor 11 is designed as a non-coherent sensor, a second radar sensor 12 and a third radar sensor 13 are designed coherently. In other embodiments, all radar sensors 11, 12, 13 can be designed coherently. Sensor data SD1, SD2, SD3 acquired by radar sensors 11, 12, 13 are divided by a data distribution unit 2 according to their evaluation type, i.e., whether they are evaluated coherently or non-coherently. The (two-dimensional) spectrum can be calculated beforehand, and the division can be based on the spectrum. In this process, regions that are advantageously evaluated coherently or non-coherently are determined. In a frequency-modulated continuous wave radar (FMCW), the division can be done by filtering.Coherent data KD is obtained by high-pass filtering, and non-coherent data NKD is obtained by low-pass filtering. The coherent data KD and the non-coherent data NKD are distributed to various evaluation units 110, 120, 130; 31, 32, 33 and evaluated there. Reference is made to Figures 2 and 3 for this purpose. From the non-coherent data NKD, for example, a vector velocity is determined and / or a common target list is created. For the coherent data KD, for example, phase and / or frequency synchronization is performed via the antenna array, and an angle estimation is also performed. In addition, the data can be divided according to distance ranges, Doppler / speed ranges and / or angle ranges of the radar signal used and distributed to the evaluation units 110, 120, 130, 31, 32, 33, which then carry out the evaluation of their data.In Figure 2, the radar sensors 11, 12, 13 each have an evaluation unit 110, 120, 130, which preprocesses the sensor data SD1, SD2, SD3. Alternatively, raw data and / or Fourier-transformed data, such as range FFT data, Doppler FFT data, and / or range Doppler FFT data, can also be transmitted, and the corresponding steps can be performed later during the evaluation. The preprocessed sensor data SD1, SD2, SD3 contain target lists ZL1, ZL2, ZL3 (see Figure 4) with the respective targets Z1, Z2, Z3. The preprocessed sensor data SD1, SD2, SD3 (or the raw data and / or the Fourier-transformed data) are transmitted to a data distribution unit 2. The data distribution unit 2 is designed here as a separate unit, but can also be part of a radar sensor 11, 12, 13.The data distribution unit 2 divides the data as described above in connection with Figure 1 and transmits it to the evaluation units 120, 130, 140 of the radar sensors 11, 12, 13. A bidirectional connection exists between the radar sensors 11, 12, 13 and the data distribution unit 2. The non-coherent data NKD are sent to the evaluation unit 110 of the first radar sensor 11. This applies in particular if the data distribution unit 2 is part of the radar sensors 11, 12, 13. The coherent data KD are separated according to targets or partial spectra of the selected areas and divided accordingly and transmitted to the evaluation unit 120 of the second radar sensor 12 and to the evaluation unit 130 of the third radar sensor 13, which operate coherently. In the evaluation units 110, 120, 130, an evaluation of their data then takes place as described above in connection with Figure 1.The evaluated data is then transmitted again via the data distribution unit 2 to a central computing device 3. The central computing device 3 has an evaluation unit 30 that generates a common evaluation result. Alternatively, this can also take place in one of the evaluation units 110, 120, 130 of the radar sensors 11, 12, 13. In Figure 3, the radar sensors 11, 12, 13 each have a preprocessing unit 111, 121, 131 that preprocesses the sensor data SD1, SD2, SD3. Alternatively, raw data and / or Fourier-transformed data, such as range FFT data, Doppler FFT data, and / or range Doppler FFT data, can be transmitted, and the corresponding steps can be performed later during the evaluation. The preprocessed sensor data SD1, SD2, SD3 contain target lists ZL1, ZL2, ZL3 (see Figure 4) with the respective targets Z1, Z2, Z3. The preprocessed sensor data SD1, SD2, SD3 (orThe raw data (i.e., the raw data and / or the Fourier-transformed data) are transmitted to a data distribution unit 2. In addition, a central computing device 3 is provided, which has a plurality of evaluation units 30, 31, 32, 33. The evaluation units 30, 31, 32, 33 can be, for example, processors, virtual cores, or software blocks. The data distribution unit 2 is designed here as a separate unit, but can also be part of the central computing device 3. The data distribution unit 2 divides the data as described above in connection with Figure 1 and transmits it to the evaluation units 31, 32, 33 of the central computing device 3. The connections between the radar sensors 11, 12, 13 and the data distribution unit 2, as well as between the data distribution unit 2 and the central computing device 3, can be designed as simple connections. The non-coherent data NKD are sent to the evaluation unit 31 purely as an example.The coherent data KD are separated according to targets or partial spectra of selected areas and divided accordingly and transmitted to the evaluation units 32 and 33. In the evaluation units 31, 32, 33, their data is then evaluated as described above in connection with Figure 1. The evaluated data is then transmitted to the evaluation unit 30, which performs an overall evaluation of the combined evaluations. Figure 4 shows three target lists ZL1, ZL2, ZL3 for the three radar sensors 11, 12, 13. In this example, these each have three targets Z1, Z2, Z3. At least the first target Z1 should be identical in the three target lists ZL1, ZL2, ZL3 of the three radar sensors 11, 12, 13. An angle diagram of the azimuth angle ^ and the elevation angle ^ is given.During preprocessing, an azimuth angle ^1 and an elevation angle ^1 for the first target Z1 were estimated by the first radar sensor 11 using a coarse angle estimate with low resolution. During the overall evaluation, a coherent cooperative angle estimation is performed for all radar sensors 11, 12, 13. Since the coarse angles ^1 and ^1 are already known, the angle estimation is performed with a higher angular resolution in a definable range around them. The higher angular resolution is represented by the finer grid in Figure 4. The boundaries of the range are chosen to be ^1- ^ ^ and ^1+ ^ ^ for the azimuth angle ^, and ^1- ^ ^ and ^1+ ^ ^ for the elevation angle ^.

Claims

R. 402737 - 16 - Claims 1. A method for controlling a coherent cooperative radar sensor network, comprising a plurality of radar sensors (11, 12, 13), wherein at least two sensors (12, 13) operate coherently, characterized in that the sensor data (SD1, SD2, SD3) are divided according to the evaluation type into data to be evaluated coherently (KD) and data to be evaluated non-coherently (NKD), and that the data to be evaluated coherently (KD) and the data to be evaluated non-coherently (NKD) are transmitted to different evaluation units (110, 120, 130; 31, 32, 33), which then each carry out an evaluation, and wherein the individual evaluations are combined into an overall evaluation. 2.Method according to claim 1, characterized in that the sensor data (SD1, SD2, SD3) are divided according to distance ranges, Doppler / speed ranges and / or angle ranges of the radar signal used and that the data of the different ranges are transmitted to different evaluation units (110, 120, 130; 31, 32, 33), which then each carry out an evaluation, and wherein the individual evaluations are combined to form an overall evaluation.

3. Method according to one of the preceding claims, characterized in that the sensor data (SD1, SD2, SD3) are transmitted to a data distribution unit (2), the sensor data (SD1, SD2, SD3) are divided by the data distribution unit (2), and the data to be evaluated coherently (KD) and the data to be evaluated non-coherently (NKD) are distributed by the data distribution unit (2) to the evaluation units (110, 120, 130; 31, 32, 33).Method according to one of the preceding claims, characterized in that the data (KD, NKD) are distributed to evaluation units (110, 120, 130) in the sensors (11, 12, 13) and the. R. 402737 - 17 - Evaluation units (110, 120, 130) of the sensors (11, 12, 13) carry out the evaluation.

5. Method according to one of the preceding claims, characterized in that the data (KD, NKD) are transmitted to a central computing device (3), and evaluation units (31, 32, 33) of the central computing device (3) carry out the evaluation.

6. Method according to one of claims 1 to 5, characterized in that the sensor data (SD1, SD2, SD3) are transmitted as raw data or as Fourier-transformed data from the sensors (11, 12, 13).

7. The method according to one of claims 1 to 5, characterized in that the sensor data (SD1, SD2, SD3) are preprocessed in the sensors (11, 12, 13) and the sensor data (SD1, SD2, SD3) are transmitted as preprocessed sensor data.

8. The method according to one of claims 1 to 6, characterized in that the sensor data (SD1, SD2, SD3) are preprocessed in the evaluation units (110, 120, 130). 9.Method according to claim 7 or 8, characterized in that during the pre-processing of the sensor data (SD1, SD2, SD3) a range and Doppler analysis is carried out and from this a detection of targets (Z1, Z2, Z3) takes place by means of an adapted analysis with a constant false alarm rate.

10. Method according to claim 9, characterized in that during the overall analysis a further analysis with a lower constant false alarm rate is carried out to detect common targets (Z1).

11. Method according to claim 9 or 10, characterized in that targets which were only detected by some of the radar sensors (11, 12, 13) are only evaluated if a quality criterion is met.

12. Method according to claim 7 or 8, characterized in that during the pre-processing of the sensor data (SD1, SD2, SD3) a range and... R. 402737 - 18 - Doppler evaluation is performed, and from this, a complete evaluation with a constant false alarm rate results in target detection and an angle estimation, wherein the transmitted sensor data contain a target list (ZL1, ZL2) with phase information.

13. The method according to claim 12, characterized in that, during the evaluation, for at least one angle (^1, ^1) of a target (Z1) estimated during the preprocessing, a coherent cooperative angle estimation is performed in a definable range around the at least one estimated angle with a higher angular resolution.

14. A computer program configured to perform each step of the method according to one of claims 1 to 13.

15. A machine-readable storage medium on which a computer program according to claim 14 is stored. 16.A coherent cooperative radar sensor network comprising a plurality of radar sensors (11, 12, 13), at least two sensors (12, 13) operating coherently, and a data distribution unit (2), the radar network being configured to carry out the method according to one of claims 1 to 13.

17. A coherent cooperative radar sensor network according to claim 16, characterized by a central computing device (3) which is configured to carry out the method according to one of claims 1 to 13.

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