Radar device and method for evaluating radar measurement signals from a radar device

Abstract

A radar device comprises a plurality of radar units, each radar unit being configured to generate and output a radar measurement signal, and a computing unit being configured to evaluate the radar measurement signals of the radar units in combination, the computing unit being configured to perform a selection of the radar measurement signals of the radar units during the combined evaluation of the radar measurement signals.

Description

[0001] The present invention relates to a radar device and a method for evaluating radar measurement signals of a radar device. State of the art

[0002] A radar device transmits a radar signal, which is reflected by objects in the radar channel. In a monostatic case, the reflected radar signal is received by the same radar device and evaluated to determine the distance, speed, and angle of the reflecting objects relative to the radar device.

[0003] In the bistatic case, the reflected radar signal can also be received by a second radar device that is spatially separated from the first. The distance, speed, and angle of the reflected objects can be determined using the known distance between the two radar devices. The acquired data is processed into reflection lists in the respective radar devices and made available, for example, via a bus system.

[0004] A cooperative radar sensor system can consist of at least two radar sensors or a processing unit with an extended antenna array consisting of sub-arrays, whereby the radar sensors or sub-arrays can be synchronized according to a synchronization concept. An exemplary radar sensor system is known from DE 2019 / 10220238 A1. Disclosure of the invention

[0005] The invention provides a radar device and a method for evaluating radar measurement signals of a radar device having the features of the independent patent claims.

[0006] Preferred embodiments are the subject of the respective subclaims.

[0007] According to a first aspect, the invention therefore relates to a radar device having a plurality of radar devices, each radar device being designed to generate and output a radar measurement signal, and having a computing device which is designed to evaluate the radar measurement signals of the radar devices in a combined manner, the computing device being designed to carry out a selection of the radar measurement signals of the radar devices during the combined evaluation of the radar measurement signals.

[0008] According to a second aspect, the invention accordingly relates to a method for evaluating radar measurement signals from a radar device. Radar measurement signals are generated by a plurality of radar devices of the radar device. Furthermore, a combined evaluation of the radar measurement signals from the radar devices takes place, wherein a selection of the radar measurement signals from the radar devices is performed during the combined evaluation of the radar measurement signals. Advantages of the invention

[0009] According to the invention, the radar measurement signals from the radar devices are selected. This means that not all radar measurement signals from the radar devices are taken into account in the combined evaluation of the radar measurement signals. The invention thus enables the use of adaptive, dynamically generated apertures in radar devices.

[0010] In order to optimally and efficiently evaluate the radar measurement data of the radar devices of the radar device, different sized sensor apertures can be used to be evaluated, depending on the available measurement points or the relative position of the targets to the radar device (e.g. the ego vehicle).

[0011] According to one embodiment, the radar device is a cooperative radar sensor system, wherein the radar devices are individual radar sensors of the radar sensor system.

[0012] According to one embodiment, the radar device is a single radar sensor, wherein the radar device comprises subarrays of antenna elements of the radar sensor. In particular, the radar device can be a radar device with a thin (“sparse”) antenna aperture, preferably with subarrays (e.g., separated by cables).

[0013] According to one embodiment of the radar device, the computing device is configured to completely omit at least one radar measurement signal from a radar device during the combined evaluation of the radar measurement signals, or to consider it only with regard to a subset of transmit / receive channels of the radar device. A subset is understood here to be a true subset, i.e., one that does not include all radar devices.

[0014] According to one embodiment of the radar device, the computing device is designed to carry out an angle determination for predetermined angle segments and / or distance segments by combined evaluation of the radar measurement signals of a predetermined subset of the radar devices.

[0015] According to one embodiment of the radar device, sensor apertures of individual radar devices can be assigned to several angle segments and / or distance segments simultaneously for joint evaluation, e.g. depending on the distance to the target, or can be cut within a physically existing radar device, ie different antennas of the same radar device can be assigned to different angle segments and / or distance segments.

[0016] According to one embodiment of the radar device, if the radar measurement signals only have a target for a subset of the radar devices in a specific distance-speed cell (i.e. a target has been detected), the computing device is designed to select the radar measurement signals of those radar devices in the subset of radar devices for the combined evaluation which form the longest, uninterrupted aperture. Depending on the preprocessing of the radar measurement data from the radar devices, whereby target lists are generated from the raw data, it may happen that not all radar devices have identified the same measurement point, e.g. with regard to distance and speed. As a result, measurement data for a cross-sensor angle evaluation is missing and defects or unoccupied spots (holes) arise in the aperture.Depending on which radar device is not providing information, the longest, reasonable aperture can be generated from the available radar measurement data and enhanced (e.g., the longest uninterrupted aperture). The same procedure can also be applied, for example, depending on the distance or angle of incidence to the target to avoid range migration effects due to the aperture size.

[0017] According to one embodiment of the radar device, the computing device is configured to detect a misalignment of the radar devices by omitting radar measurement signals from individual radar devices during the combined evaluation. For example, the misalignment detection can be performed by rollingly omitting radar measurement data from individual radar devices from the overall aperture and verifying the radar measurement data of the remaining aperture against the omitted radar device, or a correction of the measurement results from misaligned individual sensors can be performed.

[0018] According to one embodiment of the radar device, the computing device is configured to calibrate the radar device upon detecting a misalignment of one of the radar devices. This can be done, for example, using an algorithm.

[0019] According to one embodiment of the radar device, the computing device is designed to perform a single-target estimation based on a selection of the radar measurement signals and to calculate at least one quality value of the single-target estimation. The computing device is further designed to perform a combined evaluation of all radar measurement signals only if the at least one quality value falls below a predetermined threshold value. For example, when evaluating the angles of distance-velocity cells that potentially contain more than one target, a quality criterion can be determined by using a sub-aperture with few virtual channels (i.e., by selecting radar measurement data from only a few radar devices), from which it can be derived whether there is potentially more than one target in the distance-velocity cell.From this criterion, it can be determined whether further evaluation is worthwhile, such as a method for reducing a sidelobe level, multi-target estimation, or a more complex detection of targets across the spectrum of the entire aperture. This can significantly reduce the computational effort of the angle estimation.

[0020] According to one embodiment of the radar device, the combined evaluation of all radar measurement signals comprises a single-target estimation or a multi-target estimation.

[0021] According to one embodiment of the radar device, the computing device is configured to perform an angle estimation during the combined evaluation of the radar measurement signals from the radar devices. By selecting multiple radar devices, the aperture is enlarged, which increases the accuracy of the angle estimation.

[0022] Further advantages, features and details of the invention will become apparent from the following description, in which various embodiments are described in detail with reference to the drawing. Short description of the drawings

[0023] They show: Fig. 1 is a schematic block diagram of a radar device according to an embodiment of the invention; Fig. 2 schematic angle / distance segments; Fig. 3 an exemplary selection of radar measurement signals for a short range and a central long range; Fig. 4 an exemplary selection of radar measurement signals for edge segments; Fig. 5 an exemplary illustration of a lack of measurement results in the radar measurement signals; Fig. 6 an exemplary illustration for determining a misalignment of a radar device due to rotation; Fig. 7 an exemplary illustration for determining a misalignment of a radar device due to displacements of the individual radar devices relative to one another; Fig. 8 shows an exemplary illustration for determining a misalignment of a radar device due to displacements of groups of radar devices relative to one another; Fig. 9 an exemplary illustration of a determination of quality values; and Fig. 10 a flowchart of a method for evaluating radar measurement signals of a radar device according to an embodiment of the invention.

[0024] In all figures, identical or functionally equivalent elements and devices are provided with the same reference numerals. The numbering of process steps serves the purpose of clarity and is generally not intended to imply a specific chronological order. In particular, several process steps can be performed simultaneously. Description of the embodiments

[0025] Fig. 1 shows a schematic block diagram of a radar device 1 with a plurality of radar devices 21 to 2n, where n denotes the total number of radar devices. However, the invention is not limited to a specific number. The radar devices 21 to 2n can be arranged in a motor vehicle. The radar device 1 can be a cooperative radar sensor system, wherein the radar devices 21 to 2n are individual radar sensors. The radar device 1 can also be a single radar sensor, wherein the radar devices 21 to 2n are subarrays of antennas of the radar sensor.

[0026] Each radar device has a specific number of transmit / receive channels 311 to 31m, 3n1 to 3nk, where m and k denote the number of transmit / receive channels for the first radar device 21 and the nth radar device, respectively. The radar devices 21 to 2n can be configured differently or identically, ie, in particular, they can have the same or at least partially different numbers of transmit / receive channels 311 to 31m, 3n1 to 3nk.

[0027] Each radar device 21 to 2n is configured to generate and output a radar measurement signal. The radar measurement signal can comprise the radar data of all transmit / receive channels 311 to 31m, 3n1 to 3nk of the corresponding radar device 21 to 2n.

[0028] The radar device 1 further comprises a computing device 4. This can be an external device or a component of one or more of the radar devices 21 to 2n. The computing device 4 can be formed by components of each radar device 21 to 2n, whereby these components can exchange data.

[0029] The computing device 4 may comprise a processor, microprocessor, integrated circuit, application-oriented circuit, or the like. The computing device 4 may further comprise at least one memory device for storing data, in particular the radar measurement data, and program instructions.

[0030] The computing device 4 receives the radar measurement signals from the radar devices 21 to 2n and evaluates them.

[0031] The computing device 4 can perform a combined evaluation of the radar measurement signals, for example, to perform an angle estimation. The computing device 4 can perform a selection of the radar measurement signals from the radar devices 21 to 2n.

[0032] For example, the computing device 4 can completely omit at least one radar measurement signal from a radar device 21 to 2n during the combined evaluation of the radar measurement signals. The computing device 4 can also consider only a subset of transmission / reception channels 311 to 31m, 3n1 to 3nk of the radar device 21 to 2n.

[0033] Fig. Figure 2 shows schematic angle and distance segments. The radar device 1 is located at the origin of a coordinate system with x and y axes. The surrounding area is divided into six segments 51 to 56, namely a near area 56, a central far area 53 around the x-axis, and two left and two right edge areas or edge segments 51, 52 and 54, 55, respectively. The invention is not limited to a specific number of segments; the number can also be greater or less than six.

[0034] The computing device 4 can perform an angle determination for the predetermined angle and distance segments by combined evaluation of the radar measurement signals of a predetermined subset of the radar devices 21 to 2n.

[0035] Fig. 3 shows an exemplary selection of radar measurement signals for the short range 56 and the central long range 53. In this exemplary case, there are five radar devices 21 to 25, although the invention is not limited thereto.

[0036] For the near range 56, the radar measurement signals from radar devices 21 to 25 are evaluated individually (selections 61 to 65). This can, for example, also be performed as preprocessing within radar devices 21 to 25 and is particularly useful in the near range, since the far-field condition is not met there due to the size of the cooperative total aperture.

[0037] For the central long-range range 53, the radar measurement signals from all radar systems 21 to 25 are combined (selection 66). The central long-range range 53 corresponds to an angular range near boresight from a greater distance.

[0038] Fig. 4 shows an exemplary selection of radar measurement signals for the edge segments 51, 52 and 54, 55, respectively. For the outer left edge segment 51, the radar measurement signals from the two left radar devices 21, 22 are combined (selection 71). For the inner left edge segment 52, the radar measurement signals from the two left radar devices 21, 22 and a left half of the transmission / reception channels of the middle radar device 23 (i.e., with respect to the antennas arranged further to the left) are combined (selection 72). For the inner right edge segment 54, the radar measurement signals from the two right radar devices 24, 25 and a right half of the transmission / reception channels of the middle radar device 23 (i.e., with respect to the antennas arranged further to the right) are combined (selection 73). For the outer left edge segment 55, the radar measurement signals of the two right radar devices 24, 25 are combined (selection 74).

[0039] The edge segments 51, 52, 54, 55 are defined based on the far-field condition, i.e., the minimum distance from which the evaluation is to begin, or based on range migration effects along the aperture, i.e., with respect to the angular segments. The edge segments 51, 52, 54, 55 can be defined either in such a way that no significant influences arise due to the far-field condition or range migration, or in such a way that the resulting effects can be eliminated with acceptable effort.

[0040] An estimate of the far-field condition with aperture A and wavelength λ (at 77 GHz) is: dfern>2A2λ.

[0041] For range migration along the aperture A, the modulation bandwidth B, the speed of light c and the angle of incidence ϕ are: ±ϕmax <sin−1c2BA.

[0042] Based on the two estimates, a smooth transition between the apertures can also be created by defining more segments. The granularity of the respective aperture and the resulting segments is limited only by the positioning of the virtual antenna channels of the overall aperture. Depending on the system concept and data connection, the segments can also be processed at different locations, e.g., in one of the radar devices 21 to 2n, in an accumulator, or in a central processing unit, which can reduce the required data rates between the system components.

[0043] Fig. Figure 5 shows an example illustration of a missing measurement results in the radar measurement signals. Here, certain measurement data is missing from the radar measurement data of the fourth radar device 24. For example, the radar measurement signals only show a target for a subset of the radar devices 21 to 25 in a specific distance-velocity cell, namely only for the radar devices 21 to 23 and 25. Since not all radar devices 21 to 25 can provide data for the joint angle estimation (e.g., no target was found in a specific distance-velocity cell for the fourth radar device 24), data is missing to perform a joint angle estimation across the defined aperture. This leads to holes in the aperture.

[0044] One reason for this is, for example, targets with a strongly angle-dependent backscatter cross-section or a high degree of preprocessing, which has already discarded data. Instead of aborting the angle analysis and, if necessary, resorting to the results of the individual radar devices 21 to 25, an angle estimation with dynamic aperture can be performed.

[0045] For this purpose, the computing device 4 selects the radar measurement signals from those radar devices 21 to 23 and 25 of the subset of radar devices 21 to 23 and 25 for the combined evaluation, which form a longest, uninterrupted aperture (sub-aperture). In this case, these are the first three radar devices 21 to 23, responding to selection 75. This sub-aperture can be cut sensor-by-sensor or within the radar device 21 to 25, if the necessary data is available. A mask can be created based on the available data of the total aperture, which is used to cut out the relevant area from the steering matrix used for angle estimation, which is then applied to the measurement data for angle evaluation.

[0046] Fig. Figure 6 shows an exemplary illustration for determining a misalignment of a radar device 21 to 25 due to rotation. In this case, the fifth radar device 25 is rotated, i.e., misaligned.

[0047] Fig. 7 shows an exemplary illustration for determining a misalignment of a radar device 21 to 25 due to a translation, wherein the radar devices 21 to 25 are each individually shifted relative to one another and are individually checked for plausibility.

[0048] Fig. 8 shows an exemplary illustration for determining a misalignment of a radar device due to a lateral displacement in the x-, y- or z-direction, wherein groups of radar devices 21 to 25 are shifted relative to other groups of radar devices 21 to 25 or are plausibly checked on different apertures.

[0049] The computing device 4 can, by omitting radar measurement signals of individual radar devices 21 to 25 during the combined evaluation, detect a misalignment of the radar devices 21 to 25 in one of the Fig. 6 to 8. By evaluating the remaining aperture without the radar device 21 to be tested against the radar devices 21 to 25 to be tested, a misalignment can be detected.

[0050] If a target, preferably in the far field, is detected in the data from all radar devices 21 to 25, a misalignment of the individual radar devices 21 to 25 or of any subaperture can be detected by generating different subapertures, e.g., by omitting one radar device 21 to 25 at a time. Further recalibration is possible.

[0051] The misalignments can be corrected computationally and / or recalibrated. A prominent target can be selected, which is detected by the sub-aperture under investigation and by the remaining aperture, or by each radar device 21 to 25 of the remaining aperture.

[0052] For misalignments due to angular or rotational misalignments, an angle estimate of the remaining aperture and the individual sensor or the sub-aperture to be tested is performed. By comparing and verifying the plausibility of the two estimated angles, the misalignment can be detected and / or quantified. This relative misalignment can be verified and verified by permuting the combined sub-apertures, and conclusions can be drawn about the radar device, sensor, or sub-aperture that is actually misaligned. Using appropriate algorithms, the quantified misalignment can be converted into, for example, calculated correction factors, and / or a calibration matrix can be adjusted, and / or a misalignment can be reported to the user.

[0053] By using correction factors or adjusting the calibration matrix, the measurement result of the radar device or the misaligned individual sensor or the misaligned sub-aperture can be corrected and thus a deterioration of the measurement results of the overall aperture can be prevented.

[0054] In the case of a rotational misalignment, both solid angles of the radar system 21 to 2n are detuned, and detection or correction can occur in both angular directions. When detecting lateral misalignment or misalignment in the z-direction, all subapertures can be combined and permuted, as with the detection of tilt and rotation. The measurement parameters distance, velocity, and both solid angles are recorded for all subapertures and are checked against each other, for example, using a prominent target that appears in all radar measurement data or subaperture measurement data.

[0055] For example, using the solid angles and distance, all targets can be entered into a Cartesian three-dimensional grid, allowing any displacements along the x-, y-, and z-axes for given radar devices or subapertures to be detected and their measurement results corrected accordingly.

[0056] If a misalignment of one of the radar devices 21 to 25 is detected, the computing device 4 can carry out a calibration of the radar device 21 to 25.

[0057] In the example of Fig. 6, the radar measurement data of the fifth radar device 25 (aperture or selection 65) can be additionally evaluated in order, for example, to verify the plausibility of a result based on selection 72.

[0058] Fig. 9 shows an exemplary illustration of a determination of quality values. The computing device 4 can perform an angle estimation based on a selection of the radar measurement signals and calculate at least one quality value of the angle estimate. The computing device 4 can be configured to perform a combined evaluation of all radar measurement signals only if the at least one quality value falls below a predetermined threshold value.

[0059] According to one embodiment of the radar device, the combined evaluation of all radar measurement signals includes multi-target estimation and / or methods for reducing sidelobe levels. Whether such combined evaluation is performed at all on an overall aperture 81 (comprising all radar devices 21 to 24) is determined by a benefit assessment on smaller, low-computing, virtual subapertures 82, 83, 84.

[0060] For large antenna apertures with many virtual channels, angle estimation, and especially multi-target estimation, is very complex. Furthermore, the sparsity of the total aperture 81 results in very high sidelobe levels, which can be suppressed by algorithms prior to multi-target estimation. This allows two or more targets with significantly different radar backscatter cross-sections located within a distance-velocity cell to be distinguished, and to prevent weaker targets from being masked by the sidelobes of stronger ones.

[0061] Both multi-target estimation and algorithms for reducing the sidelobe level are computationally intensive and should only be applied if they are also promising. Therefore, sub-apertures 82, 83, 84 of the corresponding virtual bistatic radar devices 21 to 24 or individual sensors 21 to 24, or all virtual apertures consisting of more than two individual sensors 21 to 24, can be used to determine or estimate the number of targets in the angular spectrum and to decide on the use of multi-target estimators or target selection criteria (e.g., decision thresholds) and on the use of methods for reducing the sidelobe level on the total aperture 81.

[0062] An example of a multi-objective estimator is the two-objective deterministic maximum likelihood estimator. Decision criteria can include the choice of the threshold above which a peak in the angular spectrum is recognized as a target. Methods for reducing the sidelobe level can be so-called "compressed sensing" methods, such as the "iterative method with adaptive threshold" (IMAT), Clean, or similar.

[0063] To determine whether the use of reduction techniques, multi-objective estimators, and more complex detection methods is appropriate for the computationally intensive total aperture 81, quality criteria, such as the magnitude of the correlation factor (Bartlett estimator) for the principal angle on the computationally low-intensity subapertures, are determined. The curve 85 of an amplitude A as a function of the angle φ is plotted for the total aperture 81.

[0064] If this angular quality value, e.g., correlation value or another quality criterion, is below a certain threshold, meaning the probability that only one target is present in the spectrum is low, or if two targets are detected directly, it is very likely that multiple targets 87, 88 are present at different angles in this distance-velocity cell. Plots 86 of the amplitude A as a function of the angle φ are shown for the total aperture 81 and for a smaller sub-aperture 82.

[0065] The computing device 4 can then decide whether a downstream reconstruction of the fine-resolved angles, the use of multi-target estimators or the adaptation of the decision criteria or the detection technique based on the entire aperture is justified, and whether the computational effort for the reduction of the side lobe level is worthwhile, or whether a single-target estimator on the full aperture is already sufficient.

[0066] Fig. 10 shows a flowchart of a method for evaluating radar measurement signals of a radar device 1. The method can be carried out with the radar device 1 described above.

[0067] In a first step S1, radar measurement signals are generated by a plurality of radar devices 21 to 2n of the radar apparatus 1.

[0068] In a second step S2, a combined evaluation of the radar measurement signals of the radar devices 21 to 2n takes place, wherein a selection of the radar measurement signals of the radar devices 21 to 2n is carried out during the combined evaluation of the radar measurement signals.

[0069] At least one radar measurement signal of a radar device can be completely omitted in the combined evaluation of the radar measurement signals or only a subset of transmission / reception channels of the radar device can be taken into account.

[0070] An angle determination for given angle segments and / or distance segments can be carried out by combined evaluation of the radar measurement signals of a given subset of the radar devices.

[0071] Furthermore, radar devices with the longest uninterrupted aperture can be selected for combined analysis.

[0072] Furthermore, any misalignment of the radar equipment can be detected and corrected if necessary.

[0073] Furthermore, an angle estimation can be performed based on a selection of the radar measurement signals, and at least one quality value of the angle estimation can be calculated. A combined evaluation of all radar measurement signals is only performed if at least one quality value falls below a specified threshold. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 2019 / 10220238 A1

[0004]

Claims

[1] Radar device (1), with: a plurality of radar devices (21-2n), each radar device (21-2n) being designed to generate and output a radar measurement signal; and a computing device (4) which is designed to evaluate the radar measurement signals of the radar devices (21-2n) in a combined manner, wherein the computing device (4) is designed to carry out a selection of the radar measurement signals of the radar devices (21-2n) during the combined evaluation of the radar measurement signals. [2] Radar device (1) according to claim 1, wherein the computing device (4) is designed to completely omit at least one radar measurement signal of one of the radar devices (21-2n) in the combined evaluation of the radar measurement signals or to take it into account only with regard to a subset of transmission / reception channels (311-31m, 3n1-3nk) of the radar device (21-2n). [3] Radar device (1) according to claim 2, wherein the computing device (4) is designed to carry out an angle determination for predetermined angle segments and / or distance segments by combined evaluation of the radar measurement signals of a predetermined subset of the radar devices (21-2n). [4] Radar device (1) according to one of the preceding claims, wherein the computing device (4) is designed to select, if the radar measurement signals have a target only for a subset of the radar devices (21-2n) in a specific distance-speed cell, the radar measurement signals of those radar devices (21-2n) of the subset of radar devices (21-2n) for the combined evaluation which form a longest, uninterrupted aperture. [5] Radar device (1) according to one of the preceding claims, wherein the computing device (4) is designed to detect a misalignment of the radar devices (21-2n) by omitting radar measurement signals of individual radar devices (21-2n) during the combined evaluation. [6] Radar device (1) according to claim 5, wherein the computing device (4) is designed to carry out a calibration of the radar device (21-2n) upon detection of a misalignment of one of the radar devices (21-2n). [7] Radar device (1) according to one of the preceding claims, wherein the computing device (4) is designed to carry out a single-target estimation based on a selection of the radar measurement signals and to calculate at least one quality value of the single-target estimation, wherein the computing device (4) is further designed to carry out a combined evaluation of all radar measurement signals only if the at least one quality value falls below a predetermined threshold value. [8] Radar device (1) according to claim 7, wherein the combined evaluation of all radar measurement signals comprises a multi-target estimation. [9] Radar device (1) according to one of the preceding claims, wherein the computing device (4) is designed to carry out an angle estimation during the combined evaluation of the radar measurement signals of the radar devices (21-2n). [10] Radar device (1) according to one of the preceding claims, wherein the radar device (1) is a cooperative sensor system, and wherein the radar devices (21-2n) are radar sensors. [11] Radar device (1) according to one of claims 1 to 9, wherein the radar device (1) is a radar sensor, and wherein the radar devices (21-2n) are sub-arrays of antenna elements of the radar sensor. [12] Method for evaluating radar measurement signals of a radar device (1), comprising the steps: Generating (S1) radar measurement signals by a plurality of radar devices (21-2n) of the radar device (1); and combined evaluation (S2) of the radar measurement signals of the radar devices (21-2n), wherein a selection of the radar measurement signals of the radar devices (21-2n) is carried out during the combined evaluation of the radar measurement signals.

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