Method and apparatus for capturing surroundings - Patents.com

Abstract

To provide a radar system for capturing the surroundings of a moving object, in particular a vehicle and / or a transportation apparatus, such as a crane, in particular.SOLUTION: A radar system disclosed herein is mounted or mountable on a moving object. The radar system comprises at least two non-coherent radar modules (RM1, RM2, . . . RMN) having at least one transmitter antenna and at least one receiver antenna, where the radar modules (RM1, RM2, . . . RMN) are arranged or arrangeable in distributed fashion on the moving object. The radar system is configured to process transmitted and received signals of the radar modules to form modified measurement signals in such a way that the modified measurement signals are coherent in relation to one another.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a radar system and a corresponding method for capturing the surroundings of a moving object. [Background technology]

[0002] The prior art uses radars to capture the surroundings of a moving object, for example a vehicle, in particular an autonomous vehicle, a robot (or part thereof), a crane system (or part thereof), etc. The aim here is to capture the surroundings as accurately as possible, in particular with regard to distance, lateral position, speed and, if necessary, specific movements. Accurate capture does not only relate to the most accurate possible capture of individual isolated objects, but also to a good separation (discrimination) of the individual objects.

[0003] In a first approximation, the range resolution of a radar measures:

number

[0004] Here, let c be the speed of light and B be the signal bandwidth.

[0005] In a first approximation, the velocity resolution of comparable sized targets measures:

number

[0006] Here, the measurement duration is T SW , the center frequency of the radar signal ("center frequency") is f C Let us assume that.

[0007] Bearing resolution is usually stated in polar coordinates with respect to the origin of the radar wave and measures:

number

[0008] Here, the starting frequency of the signal is f start , the extension of the antenna (or the aperture of the antenna in the plane in which the angle is measured) is l ant Let us assume that.

[0009] The depth and velocity resolution or accuracy achievable by conventional radar systems (in authorized frequency bands) is sufficient for most tasks in the area of ​​ambient capture herein. Important limitations in ambient capture include the previously achieved angular resolution (i.e., the ability to separate or resolve multiple adjacent targets through angle) and the accuracy of the angular measurements.

[0010] According to the prior art, high angular resolution and accuracy are achievable for large, spatially extensive antenna arrays, as described, for example, in A. Schiessl, A. Genghammer, S. Ahmed, L.-P. Schmidt, Hardware Realization of a 2m x 1m Fully Electronic Simultaneous Millimeter-Wave Imaging System, EUSAR, 2012, or D. Zankl et al., BLASTDAR: A Large Radar Sensor Array System for Blast Furnace Burden Surface Imaging, IEEE Sensor Journal, Vol. 15, No. 10, October 2015.

[0011] In the prior art, all transmit and receive paths must be fed from the same HF source. Here and in the following, "HF" means high frequency, i.e. in particular frequencies above 100 MHz, preferably above 1 GHz. Correspondingly large high-frequency boards are required, the manufacture and handling of which are technically complex. Furthermore, HF antennas can have problems starting at a certain size with regard to the transmission and coherence length of the individual paths. In addition, the antennas are rigidly arranged on the HF board. The arrangement of several boards and the connecting cables between them is technically very complex or cannot be performed in a phase-stable manner at the frequencies usually used (mostly above 10 GHz). Therefore, they do not represent a practical alternative. Overall, in the prior art, it is recognized that the known methods for increasing the (azimuth) accuracy and resolution of radar systems are problematic in that they are relatively complex and expensive, or are practically impossible to implement. Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the invention is to propose a method or system for capturing the surroundings, which allows a relatively high (orientation) accuracy and resolution at low cost. [Means for solving the problem]

[0013] This object is achieved in particular by a radar system for capturing the surroundings of a moving object according to claim 1 and a corresponding method according to claim 14.

[0014] In particular, this object is achieved by a radar system for capturing the surroundings of a moving object, in particular a vehicle and / or transport device, in particular a crane. The system is mounted or mountable on the moving object. The radar system comprises at least two (non-coherent) radar modules with at least one transmitting and at least one receiving antenna. The radar modules are arranged or can be arranged on the moving object in a distributed manner. At least one evaluation device is provided, which is configured to process the transmitted and received signals of the radar modules into modified measurement signals (such that the transmitted and received signals from which the latter originate originate from a common source) such that the modified measurement signals are coherent with respect to one another.

[0015] The central idea of ​​the invention is to configure a radar system in such a way that the transmit and receive signals of the radar module are processed (in post-processing) into modified measurement signals in order to generate coherent modified measurement signals from the signals (which are essentially incoherent with respect to each other), resulting in coherent signals which on the one hand originate from the transmit and receive signals and on the other hand originate from a common source. This makes it possible to easily (significantly) improve the accuracy and resolution of the radar system.

[0016] The at least two radar modules are preferably interconnected by a bus system. Typically, each of the at least two radar modules can form a self-contained unit. The at least two radar modules can be (spatially) separated or spaced apart from each other (e.g., by at least 10 cm).

[0017] The radar system is preferably configured as follows.

[0018] A first signal is generated (or can be generated) in a first radar module and transmitted (or can be transmitted) via a path, in particular emitted (or can be emitted).

[0019] An additional first signal is generated (or can be generated) in an additional, in particular a second radar module, and is transmitted (or can be transmitted) via a path, in particular emitted (or can be emitted).

[0020] A first comparison signal is formed (or can be formed) from a first signal as received from the first radar module and by the evaluation device, in particular the additional radar module, via the path in the first radar module.

[0021] A first comparison signal is formed (or can be formed) from the first signal of the additional radar module and from the first signal as received by the evaluation device, in particular the first radar module, via the path in the additional radar module.

[0022] The additional comparison signal is preferably transmitted, in particular communicated, from the additional radar module to the first radar module.

[0023] In another respect, such a system is basically known from DE 10 2014 104 273 A1. In particular in connection with the further development of the system described in the previous paragraph, the contents disclosed in DE 10 2014 104 273 A1 are intended to be part of the present disclosure (in particular with regard to further developments or specifications of the aspects described in the previous paragraph). In this respect, the transmitting / receiving unit referred to in DE 10 2014 104 273 A1 can be part of the radar module in the present disclosure. Overall, the resolution and accuracy of the surroundings capture can be significantly improved due to its functionality, especially when combined with the method of radar imaging. In particular, by generating coherence of the basic signal, the method of radar imaging can be applied to a larger array which is consequently possible. The method of radar imaging can benefit from a larger array.

[0024] The radar system, in particular the evaluation device for forming the comparison signal, is preferably composed in particular of the first comparison signal and the additional comparison signal. With regard to the formation of the comparison signal, reference is also made to DE 10 2014 104 273 A1, the relevant disclosure of which is intended to be part of the present disclosure by reference.

[0025] In the following, the method according to DE 10 2014 104 273 A1 or a corresponding arrangement for generating a modified coherent (measurement) signal will be referred to as "method 1" or "arrangement 1".

[0026] Further developments or modifications of method 1 or arrangement 1 are described in the currently unpublished German patent application with application number 10 2016 100 107.4 and in the corresponding international patent application with application number PCT / EP2017 / 050056, the disclosure content of which is also intended to be the subject of the present disclosure by reference, in particular with regard to the formation of the coherent (measurement) signal. The method or arrangement for forming a coherent (measurement) signal according to the just mentioned application will be referred to in the following as "method 2" or "arrangement 2".

[0027] As essentially described in method 2 and configuration 2, the system, in particular the evaluation device, is preferably configured to compensate for deviations of the comparison signals caused by systematic deviations in the radar module and is configured in a second step to use at least one complex value from a first of the two comparison signals or a signal resulting from this first comparison signal for adjusting the value of at least one complex value of a second of the two comparison signals or a signal resulting from this second comparison signal, thereby forming an adjustment signal (sigCC). The adjustment is performed in such a way that a vector sum or difference of complex values ​​or a phase sum or difference of complex values ​​is formed by a mathematical operation.

[0028] Further developments and specifications of method 2 and / or configuration 2 are explained in more detail below. Overall, method 2 and / or configuration 2 result in a radar system which in the present case of capturing the surroundings, in particular when combined with the method of capturing the surroundings, allows a particularly high resolution or accuracy in the capture process by simple means and without the need for particularly large computational efforts.

[0029] Preferably (essentially as described in DE 10 2014 104 273 A1), two comparison signals are processed with one another, in particular the comparison signals subjected to conjugate imaginary multiplication, correspond to comparison signals generated by means of a coherent radar system.

[0030] The first and / or second radar module preferably comprises (respectively) at least one, more preferably at least two (particularly separated) transmitting antennas and / or at least one, preferably at least two (particularly separated) receiving antennas. Alternatively or additionally, the first and / or second radar module comprises at most four, preferably at most three (particularly separated) transmitting antennas and / or at most five (preferably at most four) receiving antennas. Thus, the radar module preferably comprises at least one transmitting and at least one receiving antenna. This transmitting and receiving antenna can also be designed as one (combined) transmitting and receiving antenna (i.e. a single antenna for both transmitting and receiving). Preferably, several transmitting and receiving antennas are accommodated in one module, more preferably there are one to three transmitting antennas and two to four receiving antennas (this has proven to be an advantageous compromise between size and space allocation in the present application). The radar module (respectively) preferably comprises a device for generating HF signals (HF generator). The radar module may further comprise a device for transmitting HF signals (including one or more antennas) and a device for receiving HF signals (including one or more antennas). The radar module may further comprise (each) a device for converting the HF signals to a lower frequency level, for example by a mixer and / or a correlator. The radar module preferably comprises (each) a separate (local) clock source for the system clock and possibly an A / D converter.

[0031] The radar modules can be distributed, for example around the vehicle and / or facing forward, facing downwards to cover the direction of movement, especially in the case of crane systems, and can exchange received signals with each other or with a central processing unit (evaluation unit), preferably via a (digital) data bus.

[0032] By spatially distributing the individual radar modules, a shared aperture of the entire radar system can be formed. The antennas of the (individual) radar modules can represent individual antenna elements. The radar modules are preferably arranged relatively far apart from each other, for example at least 5 cm apart, preferably at least 10 cm apart, more preferably at least 40 cm apart. The maximum distance can be less than 10 m, preferably less than 5 m, more preferably less than 2 m, more preferably less than 1.50 m. Alternatively or additionally, the radar modules are arranged far apart from each other such that the resulting aperture is thin and spread out (i.e. a sparse array, where there is only a small shared portion of transmit / receive antennas or transmit / receive patches in the entire antenna array). Such a thin and spread out array usually has high side lobes, which can be optimized by the individual placement. It is particularly preferred to use at least three radar modules. This allows the side lobes to be further suppressed. In particular, a thin and spread out array (sparse array) is understood as an array in which the distance between the individual transmit / receive devices (antennas) is greater than λ / 2 (λ=(average) wavelength of the transmitted signal). In particular, a sparse array is an array in which the transmit and receive antennas are not arranged in a periodic lattice so as to completely occupy the periodic lattice.

[0033] A calibration measurement is preferably performed with the radar module (especially after assembly of the individual radar modules) (preferably on a single target with a precisely known position). By comparing the actually measured angles with the predefined angles, an (optimal) correction factor can be calculated for each receive path. Particularly preferred here is to adjust the (complex) correction term for each receive path in such a way that the peak of the known target is as high and narrow as possible. This allows to compensate for the different phase offsets of the radar module.

[0034] In particular, if there is redundancy in the measurement signals (with respect to the measurement angles), which is possible in particular when using radar modules with multiple transmit / receive paths, it is particularly advantageous to perform a self-calibration without the need to know the exact position of the individual targets a priori. From the perspective of an optimization problem, the (complex) correction terms can be adaptively adjusted so that the angle estimation from all radar modules to a given target (ideally) produces consistent results.

[0035] Preferably, the radar system, in particular the evaluation device, is configured to determine the angular position of the surrounding structure by the phase monopulse method. Alternatively or additionally, the system, in particular the evaluation device, can be configured to estimate, in particular to determine, a / the angular position of a / the surrounding structure using a method in state space. In general, the radar system can be configured to first separate targets according to distance and speed criteria, for example using range-Doppler evaluation. The angle can then be determined by interferometric processing (also called phase monopulse method in radar engineering). For example, in a first step for each receiving channel, a range-Doppler diagram can now be generated. Then, for a specific target in the radar spectrum, the phase difference between two (closely) adjacent channels can be determined. Then, to improve accuracy, the phase difference can be determined for a channel located further away. Here, the (now) greatly extended base length between the channels allows for an increased accuracy. To improve or increase the angular resolution (in particular to improve sidelobe suppression), it is preferable to use a method in state space. Here, preferably, the MUSIC method according to "R. Schmidt, Multiple Emitter Location and Signal Parameter Estimation," IEEE Proceedings on Antennas and Propagation, AP-34, No. 3, March 1986 (particularly preferably for sidelobe suppression in sparse arrays) can be used. Alternatively or additionally, the Capon method according to "J. Capon, High Resolution Frequency Wavelength Spectral Analysis," IEEE Proceedings, Vol. 57, No. 8, August 1969 can be used. In particular, the Capon method is preferred because it does not require any assumptions regarding the number of targets. Such estimation can be performed in state space processing based on the quantity of eigenvalues ​​of the covariance matrix, which is relatively difficult to implement in practice. In particular, it is relatively difficult to use coherent signals, since they do not have a clear difference in terms of quantity.By comparison with the application of these methods for direction of arrival estimation using the far-field approximation, a correction of the hypothesis to be proven (called the "steering vector" in this context) is preferably performed in this application. This can be done, for example, based on the hypothesis of the holographic method (see below for details) and, if necessary, after the calculation of the beat spectrum. Alternatively, a closed solution can be used using known methods, but the latter is relatively CPU-intensive.

[0036] Preferably, the system, in particular the evaluation device, is configured to capture the surrounding structures using holographic methods, more preferably configured to use holographic methods to estimate the angular positions and / or in particular the vectorial (relative) velocities and / or in particular the vectorial (relative) accelerations of the surrounding structures. Alternatively or additionally, the system, in particular the evaluation device, is configured to perform a calibration using holographic methods.

[0037] Preferably, the radar system, in particular the evaluation device, is configured to determine a (lateral) velocity or a velocity vector, in particular by means of a method for comparing the changes in the differential phase of the reception channels. Alternatively or and / or the system, in particular the evaluation device, is preferably configured to determine a (lateral) acceleration or an acceleration vector, in particular by means of a method for comparing the changes in the differential phase of the reception channels.

[0038] The greatly enlarged aperture can also be used to improve the (vector) motion estimation, in principle. Past radar systems usually only estimate the line-of-sight velocity of the system by the Doppler effect. However, for multiple receiving channels, it is also possible to estimate the change in phase difference between the channels. From there, the transverse velocity can be estimated. However, according to these basic considerations, accurate results are only obtained when the antennas are more widely separated. It is therefore particularly preferred to build a sparse array so that accurate estimation can be achieved with at least two modules at a more widely separated interval (e.g., greater than 10 cm). Here, the evaluation is preferably realized using the FMCW chirp sequence method. For example, first, multiple, e.g., 128, frequency ramps (with the same slope) can be transmitted simultaneously (or overlapped) by at least two radar modules in unison. The received signals can then be separated, for example, according to S. Roehr, P. Gulden, M. Vossiek, "Accurate Range and Velocity Measurements for Real-Time Positioning in Multipath Environments Using a Frequency Modulated Continuous Wave Secondary Radar Approach," IEEE Proceedings of Microwave Theory and Technology, Vol. 56, No. 10, pp. 2329-2339, October 2008. Processing steps can then be performed for the indirect paths, for example, according to method 2 or configuration 2. Range-Doppler diagrams can then be calculated (for each path) and object positions and velocities can be determined. Now, from the phase difference of the received channels, according to known methods (for example, using phase monopulse or holography), the angular position can be determined. The differential phase change from ramp to ramp can then be determined (angular velocity). The latter can then be converted to lateral velocity using the measured distance. As a result, the vector velocity can be determined as the sum of the lateral and radial velocities. The above method significantly improves the process of capturing the surroundings, since the full motion vector of the object is present in the surroundings. If the distance between the radar modules (inter-module base) is large, the accuracy of the lateral velocity measurement increases.

[0039] In particular when using at least three receiving antennas, in addition to the (lateral) velocity, the (lateral) acceleration can also be determined (again by differentiating or subtracting the phase difference changes). By then determining the radial acceleration from at least three successively recorded radar spectra, the vector acceleration can also be determined. In this respect too, it is particularly advantageous to space the antennas apart from one another by a relatively large distance.

[0040] Near-field approximation is essentially a function of the target distance

number

[0041] The system, in particular the evaluation device, is preferably configured for SAR applications and / or (SAR) imaging processes, where SAR stands for Synthetic Aperture Radar. In particular, the use of large (dispersed) apertures is advantageous for SAR applications.

[0042] The radar modules are preferably arranged or can be arranged at varying heights on the moving object, preferably for measuring the heights of surrounding objects in the moving object's environment, in particular by (interferometric) SAR processing. For example, the radar modules can have a vertical distance of at least 5 cm, preferably at least 10 cm, more preferably at least 25 cm. For example, a first radar module can be arranged on the bumper of the motor vehicle, a second radar module can be arranged on or on the roof of the motor vehicle, and / or at least one radar module can be arranged at the location of the interior mirror. This results in a significant overall improvement of height measurement or height detection, for example for automatic parking maneuvers.

[0043] It is also advantageous for an arrangement of three or more systems at different heights, whereby the transit time differences between several, in particular all, stations can be used, in particular also following the approach taken in the German patent application with application number DE 10 2015 121 724.4 or the corresponding international patent application with application number PCT / EP2016 / 07596, which is not published at the time of filing.

[0044] In a preferred embodiment, phase noise or phase variations are corrected (the system, in particular the evaluation device, can be configured accordingly). The system, in particular the evaluation device, is configured to organize the phase noise part in one term for the variations in the measurement spectrum (or sweep or ramp) and the variations from measurement spectrum to measurement spectrum (or sweep to sweep or ramp to ramp). The variations from measurement spectrum to measurement spectrum are preferably determined (and corrected if necessary) as a first (separate) step. This allows a significant improvement in the accuracy of the measurement result. The variations of the phase noise part from measurement spectrum to measurement spectrum are preferably determined as one (combined) part in the two stations from the phase (combined) variations in each spectrum, preferably through a scalar product of the two measurement spectra. The two (two) measurement spectra are preferably added. These measurements also increase the accuracy of the measurement result. If necessary, the amplitudes of the spectra can be standardized beforehand to an absolute standard or to each other. In particular, the phase noise or phase variations can be easily corrected.

[0045] If necessary, a (preferably differential) correction of drift and / or jitter (in particular before phase noise correction) and / or a correction of elapsed time (in particular after drift or jitter correction) and / or a frequency offset can be performed. In particular, the embodiments described in this and the previous paragraphs also constitute an (optionally) independent subject matter of the invention, as further developments of method 1 and / or method 2. In this context, the additional features of claim 1 (and of the further independent claims) may only be optional. For example, the radar module may in this case be arranged stationary.

[0046] A (optionally independent) aspect of the invention is (thus) a radar system (with a mobile or stationary radar module or a non-coherent transmitting / receiving unit), in particular for capturing the surroundings of a (moving or non-moving) object, said system being in particular mounted or mountable on said object, said radar system comprising at least two (in particular distributedly arranged) non-coherent radar modules having at least one transmitting and at least one receiving antenna, said radar modules being in particular distributedly arranged or mountable on said object, and at least one evaluation device is provided, which is configured to process the transmitting and receiving signals of the radar modules coherently with respect to each other into a modified measurement signal, At that time A correction of phase noise or phase variations is performed (the system, in particular the evaluation device, is configured accordingly). This (optionally stationary) system, in particular the evaluation device, is configured to organize the phase noise part in one term for the variations in the measurement spectrum (or sweep or ramp) and the variations from measurement spectrum to measurement spectrum (or sweep to sweep or ramp to ramp). The variations from measurement spectrum to measurement spectrum are preferably determined (and if necessary corrected) as a first (separate) step. The variations of the phase noise part from measurement spectrum to measurement spectrum are preferably determined as one (combined) part at both stations from the phase (combined) variations in each spectrum, preferably through a scalar product of the two measurement spectra. The two (two) measurement spectra are preferably added. If necessary, the amplitudes of the spectra can be standardized beforehand to an absolute standard or to each other. In particular, the phase noise or phase variations can be easily corrected.

[0047] Another (optionally independent) aspect of the invention is (thus) a radar method (using mobile or stationary radar modules or non-coherent transmit / receive units) for capturing the surroundings of an object (moving or not moving), in particular with the above-mentioned system and / or the above-mentioned object, in which at least two non-coherent radar modules are arranged on and / or distributed over said object, and the transmit and receive signals of the radar modules are processed into modified measurement signals in a mutually coherent manner, At that time A correction of phase noise or phase variations is performed. The phase noise part is preferably organized in one term for the variations in the measurement spectrum (or sweep or ramp) and the variations from measurement spectrum to measurement spectrum (or sweep to sweep or ramp to ramp). The variations from measurement spectrum to measurement spectrum are preferably determined (and corrected if necessary) as a first (separate) step. The variations of the phase noise part from measurement spectrum to measurement spectrum are preferably determined as one (combined) part at both stations from the phase (combined) variations in each spectrum, preferably through a scalar product of the two measurement spectra. The two (two) measurement spectra are preferably added. If necessary, the amplitudes of the spectra can be standardized beforehand to an absolute standard or to each other. In particular, the phase noise or phase variations can be easily corrected.

[0048] In particular, a path is to be understood as an (air) interface, through which the corresponding signal (and, if necessary, the comparison signal) can be sent or received by means of an antenna.

[0049] An indirect path or cross path is understood as a path that originates from one (e.g. second) radar module and is received by another (e.g. first) radar module, whereas a direct path is understood as a signal that is both sent and received (as a reflected signal) by one and the same radar module.

[0050] A non-coherent radar module is understood as a radar module whose transmission signal is not coherent with respect to the signals of additional radar modules (even if the signals of the first radar module or the additional radar module are themselves coherent).

[0051] To the extent that calculations, evaluations and other processing steps are performed in the (respective) radar module, these also include, if necessary, physically self-contained evaluation devices, which are connected to the radar module. For example, each radar module can thus be designed, in particular, as an arrangement of one or more antennas with few signal generating or signal processing components, while additional components such as a signal comparison unit or evaluation device are connected to such an arrangement as structurally self-contained components. In the case of components, the latter can be structurally realizable, but this can consist of processing components as so-called hardware and / or can be converted into signal or data processing steps that are executed entirely or partly in a processor.

[0052] Typically, the evaluation device can be part of one or more (two) radar modules or can be connected to such one or more (two) radar modules. If necessary, a physically self-contained evaluation device can be provided, which is connected to the respective radar module or to the remaining parts of the respective radar module. Alternatively, the evaluation device can be integrated into the first and / or the additional (non-coherent) radar modules, for example in a shared housing and / or as one unit.

[0053] In any case, what is important is that (regardless of the specific location where the evaluation device is installed) cross paths (indirect paths) may occur, i.e. the transmission and reception areas may be covered accordingly.

[0054] In the following, method 2 or configuration 2 will be further described. In the following, it is intended that said (non-coherent) transmitting and receiving unit is part of (or forms) the above mentioned radar module. Said non-coherent transmitting and receiving unit will also be referred to as NKSE.

[0055] According to method 2, the signals transmitted between the NKSEs are processed so as to produce a comparison signal, which has advantageous properties that would otherwise only be exhibited by a radar signal associated with only one shared device for signal generation, i.e. a coherent signal source. The subject of method 2 is in particular a method for reducing the destructive effects caused by uncorrelated phase noise of multiple self-contained devices for signal generation.

[0056] Method 2 is particularly preferably applied to radar modules that are distributed, which allows a network to be formed.

[0057] In the field of radar signal processing, the goal is to convert the received signal into an intermediate frequency signal with the lowest possible noise, so that high accuracy and wide range can be achieved. Here, it is assumed that there are several extension paths between the transmitter and the receiver. In principle, the received multipath extension and correlated noise parts can be suppressed through bandpass filtering with filters precisely adapted to the expected frequencies. However, in practice this is difficult to achieve, since synchronization errors related to the sampling points and local oscillator frequencies only allow an accurate prediction of the beat signal generated after the mixing process within a limited framework. These problems reduce the correlation between the phase noise of these two signals and increase the phase estimation error.

[0058] Therefore, a method that includes a computational step that reduces or completely eliminates the effects of phase noise and synchronization errors would be advantageous.

[0059] Method 2 starts with at least two NKSEs transmitting approximately simultaneously. In this context, approximately simultaneously means transmitting the transmission signals sigTX1 and sigTX2 in both directions (i.e., sigTX1 from NKSE1 to NKSE2 and sigTX2 from NKSE2 to NKSE1) for most of their signal duration. The difference, which may not be known at first, between the start times of the transmission signals sigTX1 and sigTX2 is called T_off. The goal is to ideally have identical transmission times. Preferably, the T_off displacement is not greater than half the signal duration, and in any case, is smaller than the signal duration. Due to at least partially independent generation, the signals sigTX1 and sigTX2 have uncorrelated signal parts, which may be due to the phase noise of the signal sources at the NKSE1 and NKSE2 stations.

[0060] In such an arrangement, the same antenna transmits (T X ) and receive (R X ) is preferably used. It has been found that in the case of an arrangement (e.g. MIMOO), at least one of the transmission paths preferably exhibits a reciprocal relationship. The use of a transmission mixer in at least one transmission / reception path of the NKSE is particularly suitable for achieving this reciprocal relationship. An exemplary form of realizing a transmission mixer in a radar system is described, for example, in US 6317075 B1.

[0061] As a further step, a comparison signal (sigC21; sigC12) is then formed at each NKSE, in particular between each received signal and the transmitted signal or with a part of the transmitted signal that is correlated with the transmitted signal or with the phase noise. The method of forming these comparison signals corresponds to the approach in patent application DE 10 2014 104 273 A1.

[0062] According to the invention, the phase noise and the synchronization error are then at least reduced by processing the received signal in two stages: in a first step, systematic deviations are corrected prior to the reception of the signal by activation of a signal source and / or directly by compensation in the received signal and / or by compensation in the comparison signal, and as a second step, for example, a shortened evaluation of the correlation or the formation of a comparison signal only for the predicted deviation area or at most only for one deviation value is performed.

[0063] Contrary to what is stated in DE 10 2014 104 273 A1, it is particularly preferred not to use multiplications for the phase compensation, but rather an addition of the composite signals. The use of additions instead of multiplications is made possible by the first processing step described above, i.e. by compensating for systematic deviations in advance.

[0064] Multiplication or division of signals constitutes a non-linear operation. Non-linear operations are always accompanied by non-linear effects, namely here in particular the so-called intermodulation of signal and noise parts. This causes problems in particular in the case of radar signals with multiple signal components, i.e. in the case of signals with multiple targets or multiple signal transmission paths. The main advantage of the proposed application involving the addition of composite signals according to method 2 is that the addition is a non-linear operation, which avoids non-linear effects, namely in particular the intermodulation of signal and noise parts. Overall, this embodiment variant allows a clearly greater reduction in phase noise compared to the method of combining the comparison signals sigC21 and sigC12.

[0065] As a result, in method 2, the phase noise / phase noise effects are suppressed without the above-mentioned additional interferences foreseen in DE 10 2014 104 273 A1. Furthermore, this approach is technically advantageous, since the computational effort required in this approach is significantly lower than the computational effort required for a full multiplication or correlation as proposed as an embodiment in DE 10 2014 104 273 A1.

[0066] To be able to carry out the process according to method 2, it is preferable to first carry out an accurate (by controllable hardware) direct and / or synthetic (computer) synchronization so as to (at least largely) compensate for the frequency offset. Then, using a linearization approach, the correlated part of the impairment can be cancelled, subject only to a small residual phase difference (principle shown in FIG. 3).

[0067] Here, the synchronization can take place separately before the measurement, or during the measurement or after the measurement, for example by adjusting the comparison signal afterwards.

[0068] The synchronization may comprise any suitable means or method for adjusting the clock rates of the sources of sigTX1 and sigTX2 to each other directly (eg via a TCXO) or computationally (synthetic synchronization).

[0069] All known methods can be used to adjust the clock sources in the distributed stations. Particularly advantageous approaches to synchronization include the methods according to patent US 7,940,743, patent application DE 10 2008 010 536, or the substitution of a reference clock or a reference signal. Further methods for clock adjustment within the measurement of FMCW signals are described below.

[0070] All of these methods for adjusting the clock source can be implemented over the air or via a cable connection. "Corded" can mean an electrical or optical signal carried by a cable.

[0071] Alternatively, or to improve the method of adjusting the clock source, it is possible to use a very high quality clock source, for example a radio-controlled clock.

[0072] After the combining step, the comparison signal can be derived from the signals (sigEP21, sigEP12), which each represent a function having as functional independent variable the signal transit time or the length of the transmission channel of each signal component.

[0073] For example, the offset T_off between the stations is then determined by the method disclosed in DE 101 57 931 or by correlating at least two comparison signals of the NKSE. In this case, the offset is obtained by the maximum value. Alternatively, the method described below can also be used for FMCW signals. As before, the method implemented can be connected by cord or via radio waves.

[0074] From the signal sigEP21, at least one function value F1, which is assigned a specific elapsed time, and at least one additional function value F2 of the signal sigEP12, which is ideally assigned exactly the same elapsed time, can be determined. F1 and F2 are then cancelled out with respect to each other. For example, this can be done by adding or subtracting the two elapsed time values.

[0075] This makes it possible to eliminate or at least reduce interference from uncorrelated signal portions of the signals sigTX1 and sigTX2 due to signal phase noise.

[0076] The steps for Method 2 are summarized below:

[0077] 1. A method for reducing phase noise impairment in a radar system, comprising: In a first non-coherent transmitting / receiving unit (NKSE1), a first signal is generated (sigTX1) and transmitted, in particular emitted, via a path (SP); In an additional, in particular a second non-coherent transmitting / receiving unit (NKSE2), a (additional) first signal (sigTX2) is generated and transmitted, in particular emitted, via said path (SP), The signals (sigTX1 and sigTX2) at each of the other transceiver units are directly or indirectly received and further processed therein as received signals sigRX12 and sigRX21; in said first transceiver unit (NKSE1), a comparison signal (sigC12) is formed from its first signal (sigTX1) and from a first signal (sigRTX2) as received by said additional transceiver unit (NKSE2) via said path (SP), in said additional transceiver unit (NKSE2) an additional comparison signal (sigC21) is formed from said first signal (sigTX2) and from a first signal (sigTX1) as received by said first transceiver unit (NKSE1) via said path (SP), the additional comparison signal (sigC21) is transmitted, in particular communicated, from the additional transceiver unit (NKSE2) to the first transceiver unit (NKSE1); In a first step, deviations between the signals sigC21 and sigC12 caused by systematic deviations in the transceiver units (NKSE2, NKSE1) are compensated, in a second step, using at least one complex value from a first one of the two comparison signals or from a signal resulting from this first comparison signal for adjusting at least one complex value of a second one of the two comparison signals or from a signal resulting from this second comparison signal, thereby forming an (adjustment) signal (sigCC); The adjustment is performed such that a vector sum or difference of the complex values, or a phase sum or difference of the complex values, is formed by a mathematical operation. [Brief description of the drawings]

[0078] Exemplary embodiments are explained in more detail below on the basis of the drawings. [Figure 1] FIG. 1 shows two transmitting / receiving units communicating with each other and their individual components. [Diagram 2]FIG. 2 shows the parts from FIG. 1 along with the processing order. [Diagram 3] FIG. 3 shows the beat signals of two transmit and receive units with uncorrelated noise parts before synchronization (top), and the composite mixture with correlated phase noise after synchronization (bottom). [Figure 4] Figure 4 shows the spectrograms of all the lamps from the two transmitting and receiving units before synchronization. [Diagram 5] FIG. 5 is a schematic diagram of a configuration of multiple radar modules. [Figure 6a] FIG. 6a shows various embodiments of distributed radar modules in a motor vehicle. [Figure 6b] FIG. 6b shows various embodiments of radar modules distributed in a motor vehicle. [Figure 6c] FIG. 6c shows various embodiments of radar modules distributed in a motor vehicle. [Figure 7] FIG. 7 is a diagram relating to holographic evaluation. [Figure 8] FIG. 8 is a schematic diagram of SAR imaging. [Figure 9] FIG. 9 is a schematic diagram of an interferometric SAR. [Figure 10] FIG. 10 is a schematic diagram of a vehicle having a sensor array. [Figure 11a] FIG. 11a shows a spectrogram of the first radar module, where the horizontal axis shows distance in meters and the vertical axis shows the number of chirps or ramps. [Figure 11b] FIG. 11b shows a spectrogram of the second radar module, where the horizontal axis shows distance in meters and the vertical axis shows the number of chirps or ramps. [Figure 12a] FIG. 12a shows an additional spectrogram of the first radar module, where only the first order response was evaluated, in which the horizontal axis shows the distance in meters and the vertical axis shows the number of chirps or ramps. [Figure 12b]FIG. 12b shows an additional spectrogram of a second radar module in which only the first order response was evaluated, where the horizontal axis shows the distance in meters and the vertical axis shows the number of chirps or ramps. [Figure 13a] FIG. 13a shows an additional spectrogram of the first radar module after drift and jitter correction, where the horizontal axis shows distance in meters and the vertical axis shows chirp or ramp number. [Figure 13b] FIG. 13b shows an additional spectrogram of the second radar module after drift and jitter correction, where the horizontal axis shows distance in meters and the vertical axis shows chirp or ramp number. [Figure 14a] FIG. 14a shows an additional spectrogram of the first radar module after correction for time and frequency offsets, where the horizontal axis shows distance in meters and the vertical axis shows chirp or ramp number. [Figure 14b] FIG. 14b shows an additional spectrogram of the second radar module after correction for time and frequency offsets, where the horizontal axis shows distance in meters and the vertical axis shows chirp or ramp number. [Figure 15a] FIG. 15a shows the phase advance of the first radar module without correction of the phase deviation, where the horizontal axis shows the number of chirps or ramps and the vertical axis shows the phase in radians. [Figure 15b] FIG. 15b shows the phase advance of the second radar module without correction of the phase deviation, where the horizontal axis shows the number of chirps or ramps and the vertical axis shows the phase in radians. [Figure 16a] FIG. 16a shows the phase advance of the first radar module with correction for phase deviation, where the horizontal axis shows the chirp or ramp number and the vertical axis shows the phase in radians. [Figure 16b]FIG. 16b shows the phase advance of the second radar module with correction for phase deviation, where the horizontal axis shows the number of chirps or ramps and the vertical axis shows the phase in radians. [Figure 17a] FIG. 17a shows the 2D-(FFT) spectrum of the cross-path of the first radar module with drift and jitter and time and frequency offset correction, where the horizontal axis shows the speed in meters per second and the vertical axis shows the magnitude in decibels (dB). [Figure 17b] FIG. 17b shows the 2D-(FFT) spectrum of the cross-path of the second radar module with correction for drift and jitter and time and frequency offset, where the horizontal axis shows speed in meters per second and the vertical axis shows magnitude in decibels (dB). [Figure 18a] FIG. 18a shows the 2D-(FFT) spectrum of the cross-path of the first radar module with correction for drift and jitter and for time and frequency offset and phase variation, where the horizontal axis shows speed in meters per second and the vertical axis shows magnitude in decibels (dB). [Figure 18b] FIG. 18b shows the 2D-(FFT) spectrum of the cross-path of the second radar module with correction for drift and jitter and time and frequency offset and phase variation, where the horizontal axis shows speed in meters per second and the vertical axis shows magnitude in decibels (dB). [Figure 19] FIG. 19 shows the superimposed spectrum after addition of the spectra according to FIGS. 18a and 18b for the cross-path, where the horizontal axis shows the speed in meters per second and the vertical axis shows the magnitude in decibels (dB). [Figure 20a] FIG. 20a shows the spectrum of the first order response for the first radar module, where the horizontal axis represents speed in meters per second and the vertical axis represents magnitude in decibels (dB). [Figure 20b]FIG. 20b shows the spectrum of the first order response for the second radar module, where the horizontal axis represents speed in meters per second and the vertical axis represents magnitude in decibels (dB). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] As shown in Fig. 1, two transceiver units NKSE1 and NKSE2 communicate with each other via a radio interface. A first or second signal sigTX1 and sigTX2 is transmitted here. Each transceiver unit NKSE1 and NKSE2 comprises a signal source 1, a unit 2 for clock adjustment or comparison signal correction and a transmission comparison unit (SigComp1 and SigComp2). The (non-coherent) transceiver unit preferably consists of a radar module. In the following, NKSE1 can thus be considered as a first radar module and NKSE2 as a second radar module.

[0080] Figure 2 further shows each unit for phase correction 4. Data exchange takes place between the two units for phase correction 4.

[0081] In the following we provide a precise mathematical derivation of how method 2 works: In a first non-coherent transmitting / receiving unit (NKSE1), a first signal (sigTX1) is generated and transmitted, in particular emitted, via a path (SP). In an additional, in particular second non-coherent transmitting / receiving unit (NKSE2), a second signal (sigTX2) is generated and transmitted, in particular emitted, via said path (SP). Here, these signals are ideally emitted simultaneously, but at least are synchronized with each other such that the two signal waveforms overlap, preferably at least half the transmission time. The signal sources can be fully or partially independent.

[0082] As is usual in communications engineering, the transmission signals used (sigTX1, sigTX2) can be represented separately in an equivalent baseband signal (bbTX1) and a carrier signal.

[0083] Since the system according to the invention is preferably used for distance measurement and imaging, it is preferable to use signals with so-called good correlation properties as baseband signals. Signals with good correlation properties include, for example, broadband pulses, noise signals, pseudorandom pulse sequences (PN codes) such as M-sequences, Gold codes, Barker codes, Kasami sequences, Huffman sequences, chirps, linear frequency modulated signals (FMCW), chirps or FMCW sequences, etc. Such signal types have been known in various varieties for a long time in radar engineering and communication engineering (especially in the field of CDMA).

[0084] The transmission signal (sigTX1) of the transceiver unit (NKSE1) can be expressed as follows:

number

[0085] The time offset T01 defines the transmission time of the signal sigTX1.

[0086] phase term

number

[0087] angular frequency ω c1 characterizes the frequency of the carrier signal of sigTX1.

[0088] The transmit signal (sigTX2) of the transceiver unit (NKSE2) can be formed in a similar manner. The following applies:

number

[0089] The transmitted signals (sigTX1 and sigTX2), either directly or reflected by an object, arrive at the other transmitting / receiving stations where they are received and further processed as received signals sigRX12 and sigRX21.

[0090] The received signal received at the second non-coherent transmit / receive unit (NKSE2) corresponds to the transmitted signal (sigTX1), but the latter is modified in amplitude and has an elapsed time τ 21 For simplicity of mathematical expression, and without limiting the general disclosure, all signals are represented below as complex-valued signals. Thus, the following applies:

number

[0091] When a transmit signal (sigTX1) is transmitted to a second transceiver unit (NKSE2) in multiple (one) transmit paths of varying length, the received signal can be expressed as a linear superposition of amplitude-weighted and time-delayed signals as follows:

number

number

[0092] Therefore, the following applies to the signal transmitted from the second transceiver unit (NKSE2) to the first transceiver unit (NKSE1).

number

number

number

[0093] The transmitting / receiving units (NKSE1, NKSE2) are designed to include signal comparison units SigComp1 and SigComp, which offset each receiving signal of the transmitting / receiving unit with its transmitting signal, i.e. in NKSE1 the signal sigRX12 with the signal sigTX1 and in NKSE2 the signal sigRX21 with the signal sigX2. The signal comparison units SigComp1 and SigComp2 are designed in this exemplary embodiment as mixers Mix, i.e. here in NKSE1 the signal sigRX12 is mixed with the signal sigTX1 and in NKSE2 the signal sigRX21 is mixed with the signal sigTX2. Such a mixing process, which is generally known, can be expressed from the point of view of system theory as a multiplication or, assuming a multiplication of two complex sinusoidal signals by the complex conjugate (*=conjugate sign) of one of the signals, as a downmixing. The following therefore applies:

number

[0094] In another advantageous way of forming the comparison signal, NKSE1 does not mix signal sigRX12 with signal sigTX1, but instead mixes it only with its carrier, i.e.

number

[0095] Therefore, in NKSE2 the following applies to the signal:

number

[0096] Or, in an alternative embodiment,

number

[0097] Assume that a mechanism is provided on the NKSE to ensure that the following conditions are met:

number

[0098] How these means can be preferably configured has already been described or will be further described below in certain exemplary embodiments. Under these boundary conditions:

number

number

[0099] In a next step, data communication is used to send both comparison signals to a shared evaluation unit and ensure that both are there for evaluation, which could be NKSE1 and NKSE2, or other evaluation units.

[0100] In another processing step, the phases of the two comparison signals are added. If we only consider the carrier phase with its phase noise part, the unknown phase contribution is present only in this part and two carrier phase terms are added, so

number

[0101] Taking into account that the transit time τ is usually very small due to the high propagation speed of electromagnetic waves, that the associated phase noise part usually drops off sharply in the oscillator based on known correlations of oscillator phase noise with increasing distance from the carrier, and that φTX1 or φTX2 consequently show a pronounced low-pass behavior, especially at a cut-off frequency that is usually significantly lower than 1 / τ, we get:

number

number

[0102] In the proposed process, the phases of each of the other comparison signals are added for one of the comparison signals, which results in a significant reduction in interference due to phase noise, which increases the detectability of targets, increases the measurement range, and improves the measurement accuracy.

[0103] Depending on the mixer topology chosen, for example whether co-located or inverted mixers are used, it is possible for the phase terms presented above to have different signs. Depending on the signs, the preferred combination of the phase terms is not necessarily additive, but possibly also subtractive. The key element is that this combination leads to a reduction of the phase noise terms and the transit time dependent phase terms, i.e. the term ω cτ Furthermore, when the phase values ​​are represented by complex numbers, it is commonly known to multiply and divide the complex numbers by each other, or by the complex conjugates of each other, to form the phase sum or difference.

[0104] Possible preferred variants for reducing the phase noise part are described below. In many cases, it is beneficial to generate identical baseband signals in the first and second non-coherent transmitting / receiving units (NKSE1, NKSE2). That is, the following applies: bbTX1=bbTX2=bbTX

[0105] It is further assumed that, at least in approximate inter-radio channels, the following applies: ARX12=ARX21=ARX

[0106] Under these boundary conditions, the result is

number

number

[0107] As can be easily seen, the two signals are identical except for their phase terms.

[0108] However, regardless of the inter-radio channel, different characteristics of electronic components, such as mixers or amplifiers, can result in easily distinguishable amplitudes of the signals sigC12 and sigC21. If the amplitudes of the signals sigC12 and sigC21 are different, in the preferred variant described here, these signals must first be normalized to the same amplitude.

[0109] Additional systematic phase offsets may also occur in the formation of the signals sigC12 and sigC21. If the phase offsets of these signals sigC12 and sigC21 are different, these phase offsets must first be compensated for in the preferred variant described here.

[0110] The signals sigC12 and sigC21 can be considered as a composite pointer to a particular time t. Similar to the addition of phase terms described above, the composite addition of the pointers nullifies vector components of phase terms with different signs. As one possible preferred variant to reduce the phase noise portion, we propose to add the composite signals sigC12 and sigC21, i.e., form the signal as follows: sigCC=sigC12+sigC21

[0111] Thus, the signal sigCC has a significantly lower phase noise than the signals sigC12 or sigC21 and furthermore the signal sigCC is used for distance measurement, angle measurement or imaging purposes. However, before the summation of the signals it is important to compensate for the above-mentioned systematic deviations in amplitude and phase, which lead to different carrier frequencies and transmission times.

[0112] Of course, it is not necessary to add all the values ​​for sigC12 and sigC21, nor the signals sigC12 and sigC21 themselves, but at least one value of the signal (sigCC) is formed by using at least one complex value of a first of the two comparison signals or a signal resulting from this first comparison signal, and by adjusting the value of at least one complex value of a second of the two comparison signals or a signal resulting from this second comparison signal, but this adjustment is performed in such a way that a vector sum or difference of at least two complex values ​​resulting from sigC12 and sigC21, or a sum or difference of the phases of these complex values, is formed by a mathematical operation.

[0113] It must be noted here that the proposed mixing process only represents one possible embodiment, and the phase noise part can also be compensated in other ways: for example, all high-frequency signals can already be digitized before mixing, i.e. read by an analog-to-digital converter, and all other operations can be performed computationally or digitally, for example in a processor FPGA (Field Programmable Gate Array).

[0114] Basically, the transmission signals sigTX1 and sigTX2 can be FMCW modulated, where it is preferable to normalize the spectrum of the comparison signal to a maximum value (before the mathematical operations).

[0115] In the following, a special embodiment of method 2 using an FMCW signal and multiple consecutive N ramps is described, where the NKSE transmits multiple N signals with linearly rising or falling frequencies, hereafter referred to as frequency ramps. A comparison signal is generated from the received signal in the NKSE and temporarily stored for further processing. Rising and falling ramps are used as an example, as they allow the relative speed to be determined with the correct sign.

[0116] First individual spectrograms of the beat signals sigC12 and sigC21 are formed for each receive channel of each ramp. These spectrograms are aligned for all N consecutive ramps in amplitude representation, which does not contain phase information. This is illustrated in Figure 4 for the rising ramp, where two maxima appear, since no IQ mixing is performed, with the real-valued scanning signal present instead. During use with a primary radar, at least one reflecting object in the detection field must be identified for this step and represented as described above.

[0117] We generously cut out here the frequency band where beat signals are expected (ensuring through rough synchronization). Then we relate each spectrogram of the first N / 2 ramp to each spectrogram of the second N / 2 ramp along the frequency axis (step 1). The maximum found in this step reflects the relative time drift of the two NKSEs (a linear function can be assumed here). For example, receiving a signal via one or more reflections also allows us to identify the target via the opposite drift on both sides.

[0118] Alternatively, especially in the case of primary radars, the frequency offset can also be determined via a shared bus system by having the systems exchange their measurement signals or even synchronization signals through a cable of the bus system, where the bus system is in particular a CAN, FlexRay, Most, Gigabit Ethernet system, USB, Firewire or TTP system.

[0119] Then all the ramps in the spectrogram are corrected for this drift, for example by multiplying them with a composite correction signal with the opposite frequency offset in unit 2 for clock adjustment or comparison signal correction. The spectrograms of the different ramps obtained in this way are added (non-coherently) and the maximum corresponding to the time delay (offset error) is searched for in the superposition result. In the case of a primary radar, the identification in the previous step of co-belonging peaks can be used to select the peaks.

[0120] Alternatively, the time offset can also be determined by transmitting inter alia the measurement data or a suitable correlation sequence via the shared bus system.

[0121] The relative time delay and relative time drift parameters (=current frequency offset) thus determined are averaged over the entire sequence of N lamps. This result contains most of the clock deviation. Furthermore, it is known for each lamp and each station where in the spectrogram each energy of the arriving signal is expected.

[0122] The initially recorded local mixed signals sigC12 and sigC21 are first replaced by an integer value Tint (time delay between the two stations expressed as ΔT=|T01-T02|=Tint+Tfrac) so that a uniform time base is obtained. Due to the shared accurate time base, phase noise is more strongly correlated. The remaining small time error Tfrac can be compensated, for example, using a fractional delay filter. The thus replaced signals are corrected for the staggered ramp slope caused by the frequency offset Δω=ω1-ω2 of the two local oscillators by folding or spectrally multiplying with a standardized composite correction signal that captures the frequency progression in the opposite direction.

[0123] After FFT of the beat signal against the channel impulse response, a search for peaks in these further improved mixed signals is performed. In the case of a secondary radar, it is preferable to take the strongest or first peak. For a primary radar, a peak that is equally included on both sides must be selected. Thus, a maximum value occurs for each lamp at both stations with the associated phase position and estimated distance. In principle, these values ​​coincide with each other with respect to the measurement of the round trip path in the mutual channel. The cause of the remaining deviations can be the residual frequency and the phase difference between the two signal sources 1 of the oscillators of the NKSE, for example the root cause of phase noise. In this way, the exact frequency difference can be reliably determined and corrected (the phase difference can be determined up to an ambiguity of 180° (360° for the IQ mixer)). This ambiguity can be removed by limiting the phase advance to ±90° from lamp to lamp. This is also called unwrapping. After this exact correction of the remaining phase errors, there is almost no difference between the composite mixed signals of both stations.

[0124] After this pre-processing, the systematic errors specific to the radar system are fully corrected, resulting in a small phase shift difference between the two beat signals. Here, on the one hand, a precise synchronization is achieved in terms of time and frequency, and on the other hand, the phase noise can be considered as an additive contribution and removed by a linear combination. This is done, for example, by a 2D Fourier transform of all N ramps in both NKSEs, where the amplitude-normalized beat signals are finally summed up. The maximum of the result of this linear combination, including system parameters (sampling rate, ramp slope, carrier frequency, etc.), represents the range and velocity estimate.

[0125] FIG. 5 illustrates diagrammatically the arrangement of several radar modules RM1, RM2, ..., RMN, each of which has a device for frequency generation (HF generator) 11, a device for frequency conversion 12, an (optional) device for clock generation 13 and an (optional) device for AD conversion 14.

[0126] FIG. 6 shows an example of how the radar modules depicted diagrammatically in FIG. 1 can be arranged in a motor vehicle. In FIG. 6a, four radar modules are arranged in the motor vehicle (front left, front right, rear left, rear right). This results in a particularly advantageous capture of the surroundings (in this case with four sensors). In FIG. 6b, three radar modules are arranged in the front, specifically in the front left, front center and front right (and none in this case at the rear). This results in a particularly advantageous capture of the surroundings in the direction of travel (in this case with three sensors). In FIG. 6c, in this case, eight radar modules (front left, front center, front right, rear left, rear center, rear right, radars on both sides) can be used to achieve a particularly comprehensive capture of the surroundings.

[0127] An embodiment for holographic evaluation is described below with reference to Figure 7. For the present application, the holographic calculation can be performed as follows. The space to be calculated can be represented by individual points in the space. The arrangement of the transmit and receive antennas in or relative to the space to be calculated is (usually) known. The composite signal (amplitude, phase, frequency) resulting for the propagation path (from tentative transmit antenna a to tentative receive antenna b) can be calculated for each point in the space. This signal can then be correlated with the actual measurement data for this transmission path and a composite correlation result can be recorded for this point in the space. This process is repeated for all k propagation paths for a point in the space, each of which is (compositely) added to the previous calculation result. This sum represents the distribution probability of this point in the space. This process can be repeated for all n, m points in the space and in this way a radar image can be generated.

[0128] Specifically when using FMCW signals, holographic processing can also be performed as follows.

[0129] First, the beat spectrum can be calculated for each channel. A signal hypothesis for the phase position for each transmit-receive signal combination can be presented for each point in space, corresponding to the expected phase shift along this propagation path (from tentative transmit antenna a to tentative receive antenna b). The expected phase position can be expressed as:

number

[0130] It is particularly preferred to use holographic calculations for the calibration as well. Here, the correction vectors representing the ideally focused targets can be determined, in particular iteratively. For the calibration of the antenna array, a distant point target is used, which is (ideally) located very far away from the arrangement in the distributed radar module according to the above approximation. As a result, the required high signal-to-noise ratio is not reached. Also, in this case, it is very difficult to measure the exact position of the calibration object, and the arrangement requires a large space. It is also relatively complicated to choose a suitable environment with low noise without adding reflecting objects. It is preferred to use a large ideal point target (e.g. a metal cylinder or metal sphere) at a known position in the vicinity (rather than a distant object) for the calibration. After determining the radar arrangement and the exact position of the target, it is possible to adjust in particular the amplitude and to correct the phase difference (following the above holographic approach).

[0131] This holographic processing can also be carried out at the velocity and acceleration level. Thus, the velocity and acceleration vectors can be (holographically) determined for each image point. Suitable holographic methods for velocity and acceleration are described, for example, in DE 10 2009 030 076.

[0132] SAR imaging according to the invention will be described below with reference to FIG. 8. Radar measurements can be made and recorded in SAR imaging along a certain path of movement. These can be mathematically combined as if they were combined by an antenna array with elements at each location where measurements were recorded. In the prior art, a radar is used for this purpose to generate a synthetic aperture over the entire length of movement. By using two radars whose signals are mutually coherent, the radar data of both sensors and an additional path between the radars can be used, and the traverse path required for illumination is smaller. For this reason, a radar system is advantageously mounted on a large aperture, whose signals are corrected by post-processing as if they were generated by a coherent radar. Thus, the radar signals of both radar modules (direct path and cross or indirect path) can be used together in the SAR algorithm.

[0133] Figure 9 shows a schematic diagram of an Interferometric SAR (Synthetic Aperture Radar). Figure 10 shows a schematic vehicle with an exemplary sensor arrangement (arrangement of modules).

[0134] Measuring the height of objects is a major obstacle, especially in the field of fully automated driving, because the currently used environmental sensors (usually) only allow estimating the distance, speed and azimuth angle of targets in the vehicle environment. According to MA Richards, "A Beginner's Guide to Interferometric SAR Concepts and Signal Processing", IEEE Aerospace Electronic Systems Magazine, Vol. 22, No. 9, pp. 5-29, 2007, a system with multiple spatially offset receiving antennas can be used for height measurement. In this case, the antennas of the system are tilted downwards, where the directional characteristics of forward and downward emission (depending on the situation) can also be advantageous. Here, the achievable accuracy is largely limited by the height difference between the receiving antennas. A relatively high accuracy is especially advantageous in distinguishing objects present on the road such as curbs, fences, posts, traffic signs, manhole covers and garbage (here, for example, drink containers and small bags do not represent meaningful objects on the road), but also in detecting and distinguishing passing people and animals. Additionally, height detection is (very) important for automated parking maneuvers. According to MA Richards, "A Beginner's Guide to Interferometric SAR Concepts and Signal Processing," IEEE Aerospace Electronics Systems Magazine, Vol. 22, No. 9, pp. 5-29, 2007, the accuracy of the height measurement is determined by an approximation using:

number

[0135] Here, the two angles Ψ and β, and the distances R, B and ΔR can be gathered from FIG. 9. Here, δ(ΔR) represents the measurement accuracy with respect to the differential distance and can be determined very accurately, for example, using phase comparison. In the present invention, the reference line B can be significantly increased, since additional receiving elements (modules) can be arranged on the vehicle as desired (or at least essentially as desired). For example, by arranging one radar module on the bumper and a second radar module on the roof of the vehicle, the accuracy can be improved by a factor of 10 (compared to one small radar module with multiple receiving elements). Exemplary installation positions are shown in FIG. 10. In particular, side mirrors 16 are shown at the bumper 15 and / or on the roof (roof rail) 17.

[0136] Methods for reducing interference components, in particular phase noise, are described on the basis of diagrams according to figures 11a, 11b to 20a, 20b. These methods are also described as further developments of method 1 or method 2 as an (optionally) independent subject matter of the present invention. In this context, the additional features of claim 1 (and the other independent claims) may be merely optional.

[0137] To the extent that modules are described below, these may in particular be (non-coherent) transmitting / receiving units according to method 1 or method 2. The modules (transmitting / receiving units) therefore do not (necessarily) need to be placed on a moving object (e.g. a motor vehicle according to FIG. 8) or configured for such a placement, although this is possible.

[0138] FIG. 11a shows the spectrum of a first radar module. In particular, it shows the progression of several (here, for example, 128) lamps when they are drawn next to each other relative to the transmission channel. As can be seen, the cross paths are affected on the one hand by a frequency offset Δf (here chosen as 350 kHz) and also by unknown drifts Td and jitters Tj, so that the beat frequency varies with respect to the signal duration (i.e., a sequence of 128 lamps for example). Furthermore, the cross paths of the module T off,0 There may also be an unknown time offset between the two. This offset is generated by different starting points for signal generation in the radar modules. This offset may not be fully known even assuming pre-synchronization over the air interface or over a synchronization line. Figure 11b shows the corresponding spectrum of the second radar module.

[0139] The case where (only) one primary radar response is evaluated is shown in Fig. 12a (for the first radar module) and Fig. 12b (for the second radar module). These representations result specifically from a 2D-FFT without preprocessing.

[0140] It can be seen that a stationary target with v=0 m / s is lined up with a moving target with a constant velocity of 0.2 m / s at a certain distance. The cross-path response cannot be evaluated this way (at least not particularly accurately), but it can be corrected based on the following statements (algorithm). The azimuth angle can be used for further (complete) evaluation.

[0141] The cross-path signal of the (two) radar modules after the blending process is subject to (all) system variables for the signal path and is described accurately enough for an initial observation (initially multipath propagation or multiple targets are not modeled for clarity) as follows:

number

[0142] In principle, the mixed signal can have the amplitude A a , Two phase terms

number

number

[0143] In the above equation (1), the following applies: a: Number of stations (e.g., 1 or 2) n: number of channels (e.g. 1 to 8) l: Number of lamps (e.g., 1 to 128) A a : Signal amplitude f0: Carrier frequency (e.g., about 78 GHz) τ: elapsed time, cross path τ l :Change in time due to object movement T off,l =T off,0 +T j,l +l T D Timing offsets (e.g. due to cable length, jitter and / or drift) δφ 0,l : Phase variation via carrier frequency drift and / or other unknown components φ p,al (t): (uncorrelated) phase noise φ an : Phase variation between stations and individual channels Δ f : Frequency offset (e.g., 350 kHz) μ: sweep speed (e.g., 500GHz / s)

[0144] This change in time is detected by a phase change in the beat frequency, which (assuming at least approximately uniform motion during the measurement period) is assumed to be at least approximately constant within the measurement period.

[0145] The Fourier transform of the ramp produces a beat signal.

number

[0146] This description is essentially possible independent of the window function selected, so the latter can be omitted. The phase noise in the mixed signal of a station depends on the current phase position, φ p、1l (t)=Ψ p,1l (tT off,l )-Ψ p,2l (t-τ) and φ p,1l (t)=Ψ p,1l (t-τ-T off,l )-Ψ p,2l (t). Since the time difference between the two points in time is important for the variance of the phase noise (Allan variance), the manifestations at both stations are almost the same (φ p、1l (t)~φ p、2l (t)). Local oscillator Ψ p,1l and Ψ p,2l The phase noise of is uncorrelated (in contrast to primary radar) and can (significantly) degrade phase estimation or signal coherence or velocity measurements.

[0147] The algorithm for evaluating the sampled signal (according to equation (1)) is given below:

[0148] In a first step, each spectrum can be calculated, for example, via a Fourier transform from a Hilbert transform (which may be necessary if I / Q data is not available).

[0149] As is evident from the spectra in Figure 11a and Figure 11b, there is a (roughly) linear increase in the cross-path beat frequency over time, and there may also be a ±1 clock jitter. This may be due to the fact that each radar module uses a different clock source. In the modified form this can be excluded and can be formulated as follows:

number

[0150] Now, the drift TD along with the randomly distributed jitter (from a signal processing point of view) can be corrected in this calculation step.

number

[0151] The area around the cross-path can be cut into intervals (larger) so that the resulting signal also contains information about (farther) distant targets (with a larger beat frequency in the second radar module). In this case, equation (2) describes all the relevant signal components.

[0152] As is evident from equation (2), the beat frequency for the target is the same for all channels (where the antenna position only varies slightly).

[0153] The absolute values ​​of equation (2) can be summed for each channel in both radar modules as follows:

number

[0154] This results in a signal with a relatively high SNR (signal to noise ratio), which can be expressed as follows:

number

[0155] Here, B arepresents the sum of the amplitudes of the individual channels. In the system under consideration (which has relatively little phase noise), this effect causes very little beat frequency change during the ramp, as seen by the following approximation:

number

[0156] As can be seen from equation (3), the frequency offset Δf and the timing offset T off,l causes a variation in the beat frequency in the same direction and the signal transit time causes a variation in the opposite direction.

[0157] Two station signals S 1l (f) and S 2l We can calculate the convolution of (f) and remove the signal transit time τ. The resulting signal

number

number

[0158] To remove all assignments that are constant over time, we use the difference sequence

number

[0159] D1 to c 1l , c 2land c 3l The sequence can be divided into three subsequences, denoted by

[0160] The jump height due to jitter can be determined by expectation generation.

number

[0161] Drift can also be estimated by expectation generation in a similar manner.

number

[0162] Thus, the two correction values ​​J0 and T D Let D1 = μ(T j,l -T j、l+1 -T D ) and, if necessary, for jitter and drift correction. Figures 13a and 13b show the spectrograms of both modules after drift and jitter correction (Figure 13a for the first radar module and Figure 13b for the second radar module).

[0163] If necessary, a jitter-free system (in clock magnitude) can be achieved when using a shared trigger for each module, but in this case there may still be an obviously small portion of residual jitter, which is compensated for in other processing steps.

[0164] Synchronization via, for example, the CAN bus could prevent drifts of both modules. Synchronization of clock signals and a shared trigger facilitates evaluation using the described method, as there is no jitter and the drift is (negligible).

[0165] The correction of elapsed time and frequency offset is described below.

[0166] The time lapse through the synchronization cable or the (set) frequency offset (to separate the first and second order responses) can cause an (unknown) displacement of the beat frequency, which is the same at both stations. After applying the above corrections, and following from equation (3), the amplitude of the beat signal at both stations is:

number

[0167] This signal no longer varies with chirp, i.e. with respect to the number of lamps l. Therefore, the sum

number

number

[0168] The spectrum of one station is arbitrarily reflected to this virtual center, and then the amplitudes of the two spectra appear at the same position, and after shifting the focus to a beat frequency of 0 Hz (the absolute position of the maximum now corresponds to the actual target range), it can be expressed as follows:

number

[0169] Figures 14a and 14b show the spectrograms of both modules after correction for time and frequency offsets (Figure 14a for the first module and Figure 14b for the second module, both modules being spaced a small distance apart, which allows a certain level of crosstalk to be discerned as a "target" at 0m).

[0170] The correction of the phase variation will be described below.

[0171] In principle, as can be seen in Figures 15a and 15b (Figure 15a for the first module and Figure 15b for the second module), in this example 128 consecutive ramps are transmitted so that the phase progression of the two stations coincides with respect to the target (here the one with the largest amplitude). After correction of all frequency terms, the spectrogram can be expressed as follows:

number

[0172] This now has a quasi-constant beat frequency of the target at the defined distance.

number

[0173] In principle, the phase can be determined at the maximum occurrence peak, but on the one hand, this phase position can only be determined as an overlap assuming closely adjacent targets, and on the other hand, this variant only incorporates information about the target, which is generally disadvantageous in the case of multipath propagation or multiple reflection points to be detected.

[0174] Therefore, the argument of the composite standard scalar product

number

number

[0175] The phase progression assuming fixed targets for both stations and all channels is shown in Figures 16a and 16b (Figure 16a for the first module and Figure 16b for the second module), the latter only slightly deviating from a constant function (residual deviations are corrected as necessary in subsequent steps).

[0176] The next complex conjugate of the signal from the second radar module leads to the following spectrum:

number

[0177] This is essentially the term

number

[0178] That is, the phase jump between adjacent ramps may be too large for phase tracking in a large number of measurements. In particular, the maximum expected phase jump may limit the measurement range in terms of Doppler frequency and therefore in terms of maximum detectable velocity. By improving the synchronization of the two stations, this problem can be mitigated. Deviations remaining after adjustment of the clock speed may (no longer) cause phase jumps to occur over the uniqueness region between adjacent sweeps.

[0179] Spectral adjustment and overlapping are described below.

[0180] Before overlapping the two spectra, an adjustment can be made to correct for the potential phase shift of the strongest target given the non-reciprocal channel. Additionally, the amplitude of this target can be aligned for both spectra and / or normalized to a shared or third variable. After these two operations, the selected channel n can be expressed as:

number

[0181] Here, the phase noise remaining in the chirp (sweep) is

number

number

[0182] The correction signal model will now be described.

[0183] Cross-path signal

number

number

[0184] With the above corrections, improved 2D range-Doppler plots or simple Doppler plots can be generated (sic) as shown in Fig. 17a and 17b (which show plots without the corrected phase variation, while Fig. 18a and 18b show plots with the corrected phase variation, Fig. 17a and 18b for the first module and Fig. 18a and 18b for the second module), from which the velocity can be derived relatively accurately. On the cross-path, the residual phase noise, which is much stronger than for the primary radar response, appears in the form of small randomly distributed peaks. These are distributed over all velocities and are (pseudo) identical (but 180 degrees out of phase) in the first and second modules. After adding both 2D spectra, a spectrum (except for potentially relatively small amplitude noise) is generated (see Fig. 19) corresponding to the primary radar (see Fig. 20a for the first module and Fig. 20b for the second module). This leads to much more measurement dynamics, where weak targets (in an environment of strong targets) can also be recognized. Since changing azimuth angles can introduce additional phase offsets, the method is shown here for individual channels.

[0185] The described method of reducing interference components, in particular the phase noise, has a series of advantages (especially in the automotive field), in particular an improvement in the SNR (signal-to-noise ratio) and in reliability can be achieved, and furthermore, the distance and velocity vector of the target can be estimated with a relatively high degree of accuracy, since additional estimates can be obtained and used.

[0186] The (coherent) processing of the frequency shift caused by the Doppler effect can be facilitated via the cross-path. In this way, the phase information from the first radar module and the second radar module can be used to accurately measure the surroundings. As a result, SAR processing can be performed to generate a high-resolution image of the surroundings, especially in automotive radar applications.

[0187] The application of both stations as a phase monopole can help to estimate the azimuth angle very accurately, which can also be used in conjunction with existing angle information to further improve accuracy.

[0188] It can be noted that a rough synchronization (pre-synchronization) is basically possible by feeding in an external regulated clock, for example via the (motor vehicle) CAN bus, which can reduce the computational effort of the method and reduce error propagation.

[0189] The additional information increases the probability of validating the validity of radar targets in road traffic: cross-path measurements (directly) of each target allow additional estimates of speed, azimuth angle and distance, which makes tracking particularly easy.

[0190] Reflections from complex objects can be recognized relatively easily, possibly even when they do not travel in the direction of the incident wave (bistatic radar principle). By combining several radar modules, the estimation of the specific movement of a moving object (vehicle) can be (significantly) improved, since the accuracy of the angle measurement has a significant influence on the latter.

[0191] By combining several radar modules in the direction of ascent, in particular with Interferometric SAR, the height estimation, i.e. the estimation of the height profile of the (complete) surroundings of a moving object (vehicle), can be significantly improved.

[0192] Aspects and embodiments of the method 1 or the configuration 1 are described below, where the reference numbers relate to the numerical values ​​of DE 10 2014 104 273 A1. The transceiver unit can be part of or comprise a radar module.

[0193] Aspect 1: A method in a radar system, comprising: In a first (non-coherent) transmitting / receiving unit (NKSE1), a first signal (sigTX1) is generated and transmitted, in particular emitted, via a path (SP); In an additional, in particular a second (non-coherent) transceiver unit (NKSE2), a first signal (sigTX2) is generated and transmitted, in particular emitted, via a path (SP), in said first transceiver unit (NKSE1) a comparison signal (sigC12) is formed from said first signal (sigTX1) and from a first signal (sigRTX2) as received by said additional transceiver unit (NKSE2) via said path (SP), in said additional transceiver unit (NKSE2) an additional comparison signal (sigC21) is formed from said first signal (sigTX2) and from a first signal (sigTX1) as received by said first transceiver unit (NKSE1) via said path (SP), The comparison signal (sigC21) is transmitted, in particular communicated, from the additional transceiver unit (NKSE2) to the first transceiver unit (NKSE1).

[0194] Aspect 2: In the method according to the first aspect, a comparison signal (sigC21; sigC12) is formed from the comparison signal (sigC21) and the additional comparison signal (sigC21).

[0195] Aspect 3: In the method according to aspect 2, the comparison signal (sigC21; sigC12) is generated by processing the two comparison signals (sigC12, sigC21) together, in particular by subjecting them to conjugate imaginary multiplication, so that the comparison signal corresponds to a comparison signal generated by a coherent radar system.

[0196] Aspect 4: In the method according to the preceding aspect, at least one of the comparison signal (sigC12), the additional comparison signal (sigC21) or the comparison comparison signal (sigC21;sigC12) is formed by mixing or correlation.

[0197] Aspect 5: In a method according to a preceding aspect, at least one such additional comparison signal (sigC21; sigC12) is transmitted between the transmitting / receiving units (NKSE2; NKSE1) as one of data, a signal containing data or a signal reconfigurably containing data.

[0198] Aspect 6: In a method according to a preceding aspect, at least one of the first signals (sigTX1, sigTX2) is transmitted as a transmission signal via the path (SP) designed as an air interface.

[0199] Aspect 7: In a method according to any preceding aspect, the points in time at which the first signals (sigTX1, sigTX2) are transmitted are adjusted so that the first signals (sigTX1, sigTX2) at least partially overlap in chronological order.

[0200] Aspect 8: In a method according to a preceding aspect, the signal transit time (τ12) required by such a first signal (sigTX1, sigTX2) for the path between the transceiver units (NKSE1, NKSE2) is determined from at least one comparison signal (sigC21; sigC12) by analyzing at least one of the frequency phase or phase values ​​(φ12, φ13, ... φ1N, φ22, φ23, φ24, ... φ2N, ... φN-1N), amplitude progression or phase progression of the comparison signal (sigCC12).

[0201] Aspect 9: In the method according to the preceding aspect, at least one of the first signals (sigTX1, sigTX2) is generated and transmitted as an FMCW or OFDM modulated signal.

[0202] Aspect 10: In the method according to the preceding aspect, at least one of the first signals (sigTX1, sigTX2) is generated and transmitted as a multi-ramp signal.

[0203] Embodiment 11: In the method according to any preceding embodiment, A plurality of comparison comparison signals (sigCC12) are measured alternately in a time sequence using at least two transmitting / receiving units (NKSE1, NKSE2), at least one of the transmitting / receiving units (NKSE1, NKSE2) is moved; A synthetic aperture process is used to determine at least one of the range, position, velocity or presence of one of the transmitting / receiving units (NKSE2, NKSE1), or the presence of such a transmitting / receiving unit (NKSE2, NKSE1), or at least one of the range, position, velocity or presence of object (O) relative to object (O).

[0204] Aspect 12: A radar system, comprising: at least one first (non-coherent) transmitting / receiving unit (NKSE1) is designed to generate and transmit, in particular emit, a first signal (sigTX1) via a path (SP); at least one additional, in particular a second (non-coherent) transmitting / receiving unit (NKSE1), designed to generate and transmit, in particular emit, a first signal (sigTX2) via said path (SP), said first transceiver unit (NKSE1) is designed to form a comparison signal (sigC12) from its first signal (sigTX1) and from a first signal (sigTX2) as received by said additional transceiver unit (NKSE2) via said path (SP), said additional transceiver unit (NKSE2) is designed to form a comparison signal (sigC21) from its first signal (sigTX2) and from a first signal (sigTX1) as received by said first transceiver unit (NKSE1) via said path (SP), The comparison signal (sigC21) is transmitted, in particular communicated, from the additional transceiver unit (NKSE2) to the first transceiver unit (NKSE1).

[0205] Aspect 13: In the radar system according to aspect 12, a comparison signal (sigC21; sig12) is formed from the comparison signal (sigC21) and the additional comparison signal (sigC21).

[0206] Aspect 14: In a radar system having three or more spatially separated transceiver units (NKSE1, NKSE2, NKSE3, ..., NKSE-N) according to aspect 12 or 13, at least one of the distance, position, velocity or presence of one of the transceiver units (NKSE2, NKSE1), or the presence of such a transceiver unit (NKSE2, NKSE1), or the distance, position, velocity or presence of an object (O) relative to an object (O) is determined from two or more comparison signals (sigCC12, sigCC12, sigCC13, sigCC22, ..., sigCC32) measured using two or more pairs of each of the spatially separated transceiver units (NKSE1, NKSE2; NKSE-N, NKSE2).

[0207] Aspect 15: In a radar system according to one of aspects 12 to 14, the first transceiver unit (NKSE1) and at least one such additional transceiver unit (NKSE2) and / or the evaluation device (P) are designed to implement a method according to one of the preceding aspects.

[0208] Aspect 16: An apparatus of a radar system, in particular for implementing a method according to one of aspects 1 to 11, and / or in a radar system according to one of aspects 12 to 15, comprising: Designed as the first (non-coherent) transmit / receive unit (NKSE1), a signal generator and at least one antenna (TA1; RA1) that are designed in particular to generate and transmit a first signal (sigTX1) via a path (SP), said first signal and an arrangement designed to form a comparison signal (sigC12) from the first signal (sigTX2) as received by said additional transceiver unit (NKSE2) via said path (SP), an interface (CommTX) specifically designed for communication, which transmits said comparison signal (sigC12) to said additional transceiver unit (NKSE2), or an interface (CommRX) designed to transmit, in particular receive by communication, an additional comparison signal (sigC21) as generated by said additional transceiver unit (NKSE2) in said first transceiver unit (NKSE1), The present invention has at least one of the following:

[0209] Aspect 17: The device according to aspect 16 has an additional comparison unit (sigComp12) which forms a comparison signal (sigCC12) from the comparison signal (sigC21) formed in the same transceiver unit (NKSE1) and the comparison signal (sigC21) transmitted to this transceiver unit (NKSE1).

[0210] Example 18: In the device according to example 16 or 17, the at least one interface (CommTX, CommRX) is a data interface.

[0211] Aspect 19: In an apparatus relating to one of aspects 16 to 18, a filter (FLT) is arranged between the arrangement that outputs the comparison signal (sigC12) and the additional comparison unit (sigComp12) that forms the comparison comparison signal (sigCC12), and the filter (FLT) applies the comparison signal (sigC12) to the comparison unit (sigComp12), and the filter (FLT) does not apply the additional comparison signal (sigC11) formed in the arrangement upstream of the filter (FLT) and suppresses the comparison signal (sigC11) formed in the upstream arrangement or supplies it at a terminal.

[0212] Aspect 20: An apparatus according to one of aspects 16 to 19 has a plurality of receiving antennas (RA1, 1, ..., RA1, N; RA2, 1, ..., RA2, N) spatially separated from one another, each of the plurality of receiving antennas being assigned an arrangement designed to form a respective comparison signal (sigC21, 1, sigC21, 2, sigC21, 3) from said first signal (sigTX2) and from a first signal (sigTX1) as received by such additional transceiver unit (NKSE2) via said path (SP).

[0213] Aspects and embodiments of method 2 or configuration 2 are described below, where reference numbers refer to Figures 1 to 4 of the present application. The transceiver unit may be part of or comprise a radar module.

[0214] Aspect 1: A method for reducing phase noise impairment in a radar system, comprising: In a first (non-coherent) transmitting / receiving unit (NKSE1), a first signal (sigTX1) is generated and transmitted, in particular emitted, via a path (SP); In an additional, in particular a second (non-coherent) transmitting / receiving unit (NKSE1), a first signal (sigTX2) is generated and transmitted, in particular emitted, via said path (SP), said first signals (sigTX1 and sigTX2) being received directly or indirectly in each additional transceiver unit and further processed therein as received signals (sigRX12 and sigRX21); in said first transceiver unit (NKSE1), a comparison signal (sigC12) is formed from its first signal (sigTX1) and from a first signal (sigRTX2) as received by said additional transceiver unit (NKSE2) via said path (SP), in said additional transceiver unit (NKSE2) an additional comparison signal (sigC12) is formed from its first signal (sigTX2) and from a first signal (sigTX1) as received by said first transceiver unit (NKSE1) via said path (SP), the additional comparison signal (sigC21) is transmitted, in particular communicated, from the additional transceiver unit (NKSE2) to the first transceiver unit (NKSE1); In a first step, deviations of the comparison signals (sigC21 and sigC12) caused by systematic deviations in the transmitting / receiving units (NKSE2, NKSE1) are compensated for, In a second step, at least one complex value from a first one of the two comparison signals or a signal derived from this first comparison signal is used to adjust at least one complex value from a second one of the two comparison signals or a signal derived from this second comparison signal, thereby forming an adjustment signal (sigCC); Said adjustment is performed such that the mathematical operation forms a vector sum or difference of complex values, or forms a phase sum or difference of said complex values.

[0215] Aspect 2: In the method according to aspect 1, the transmission signals (sigTX1 and sigTX2) are FMCW modulated.

[0216] Aspect 3: In the method according to aspect 1 or 2, the clock speed adjustment, in particular of the signal sources of the first signals (sigTX1 and sigTX2), is performed via a bus system, preferably a communication bus, and / or the clock speed adjustment, in particular of the clock speed of the signal sources of the first signals (sigTX1 and sigTX2), is performed via radio and / or cable connection, in particular during operation as a primary radar.

[0217] Aspect 4: In a method according to one of the preceding aspects, the synchronization of the (non-coherent) transmitting / receiving units (NKSE1, NKSE2), in particular pre-synchronization by determining the frequency offset, is performed successively over multiple ramps, in particular when using a secondary radar.

[0218] Aspect 5: In a method according to one of the preceding aspects, the offset, in particular the time offset and / or the frequency offset, is determined via the bus system, preferably during operation as a primary radar.

[0219] Aspect 6: In a method according to one of the preceding aspects, the / the offset, in particular the / the time offset and / or the / the frequency offset, is / are determined, in particular by evaluating the position of a correction maximum of the spectrum of the comparison signals (sigC12 and sigC21).

[0220] Aspect 7: In the method according to one of the preceding aspects, the first and / or the additional (non-coherent) transmitting / receiving unit comprises at least one evaluation device for carrying out individual processing steps, in particular calculation and evaluation, each evaluation device comprising: It may be a self-contained evaluation device, connected to the respective transceiver unit or to the remaining parts of the respective transceiver unit, or it may be integrated into the first and / or the additional (non-coherent) transceiver unit, for example in a shared housing and / or as one unit.

[0221] Aspect 8: In a method according to one of the preceding aspects, the comparison signals (sigC12 and sigC21) are in particular transmitted to a shared evaluation unit, where both are present for evaluation, said shared evaluation unit being optionally the first (non-coherent) transceiver unit (NKSE1), optionally the second (non-coherent) transceiver unit (NKSE2), or optionally another, in particular separate, evaluation unit.

[0222] Aspect 9: In a method according to one of the preceding aspects, the first signals (TX1 and TX2) are transmitted at least overlapping in time order, and the additional first signal (TX2) of the additional (non-coherent) transceiver unit (NKSE2) is preferably transmitted during half the signal duration of the first signal (TX1) of the first (non-coherent) transceiver unit (NKSE2), and more preferably at least approximately simultaneously.

[0223] Aspect 10: In the method according to one of the preceding aspects, the spectrum of the comparison signal is normalized to a maximum value prior to the mathematical operation.

[0224] Aspect 11: A system for reducing interference due to phase noise in a radar system comprising a unit implementing the method according to one of the preceding aspects, in particular a first (non-coherent) transmitting / receiving unit (NKSE1) for generating a first signal (sigTX1) and for transmitting, in particular emitting, said first signal (sigTX1) via a path (SP); an additional, in particular a second (non-coherent) transmitting / receiving unit (NKSE1) for generating a first signal (sigTX2) and for transmitting, in particular emitting, said first signal (sigTX2) via a path (SP), said (non-coherent) transmitting / receiving units (NKSE1 and NKSE2) are designed to directly or indirectly receive said first signals (sigTX1 and sigTX2) and thereafter further process them as received signals (sigRX12 and sigRX21); said first transceiver unit (NKSE1) is designed to form a comparison signal (sigC12) from its first signal (sigTX1) and from a first signal (sigRTX2) as received by said additional transceiver unit (NKSE2) via said path (SP), said additional transceiver unit (NKSE2) is designed to form an additional comparison signal (sigC21) from its first signal (sigTX2) and from a first signal (sigTX1) as received by said first transceiver unit (NKSE1) via said path (SP), a sending unit is provided in particular for communicating to send said additional comparison signal (sigC21) from said additional transceiver unit (NKSE2) to said first transceiver unit (NKSE1), At least one evaluation unit is provided which is designed in a first step to compensate for deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the transmitting / receiving units (NKSE2, NKSE1) and in a second step to use at least one complex value from a first of the two comparison signals or a signal resulting from this first comparison signal to adjust the value of at least one complex value of a second of the two comparison signals or a signal resulting from this second comparison signal, thereby forming an adjustment signal (sigCC), said adjustment being performed such that a mathematical operation forms a vector sum or difference of complex values ​​or a phase sum or difference of the complex values.

[0225] Aspect 12: In the system according to aspect 11, a bus system, in particular a communication bus, is provided, in particular for clock speed adjustment of the signal source of the first signals (sigTX1 and sigTX2), And / or a bus system is provided for determining the offset, in particular the time offset and / or the frequency offset.

[0226] Aspect 13: In the system according to any one of aspects 11 or 12, a shared transmit / receive antenna is provided in the first and / or the additional (non-coherent) transmit / receive unit (NKSE1 and / or NKSE2); and / or A transmit mixer is provided on said path (SP).

[0227] Aspect 14: Use of the method according to one of aspects 1 to 10 for a system having at least one shared transmit / receive antenna in the first and / or second (non-coherent) transmit / receive units (NKSE1 and / or NKSE2), respectively.

[0228] Aspect 15: Use of the method according to any one of aspects 11 to 13 to reduce interference due to phase noise in a radar system.

[0229] It is to be noted that at this stage all the above mentioned components or features, both individually and in any combination, are claimed as essential to the invention and are particularly shown in detail in the drawings, modifications thereto being well known to the expert. The invention as originally claimed in the present application is set forth below. [1] A radar system for capturing the surroundings of a moving object, in particular a vehicle and / or transport device such as a crane, said system being mounted or mountable on said moving object, said radar system comprising at least two non-coherent radar modules (RM1, RM2, ..., RMN) with at least one transmitting and at least one receiving antenna, the radar modules (RM1, RM2, ..., RMN) are arranged or can be arranged on the moving object in a distributed manner, at least one evaluation device is provided, which is configured to process the transmitted and received signals of the radar module into modified measurement signals such that the modified measurement signals are coherent with respect to each other; Radar system. [2] The system of [1] , wherein the at least two radar modules are connected to each other by a bus system. [3] A first signal (sigTX1) is generated in a first radar module (RM1) and transmitted, in particular emitted, via a path (SP); an additional first signal (sigTX2) is generated in an additional, in particular a second, radar module (RM2) and transmitted, in particular emitted, via a path (SP); in the evaluation device, in particular in the first radar module (RM1), a first comparison signal (sigC12) is formed from the first signal (sigTX1) of the first radar module and from a first signal (sigTX2) as received by the additional radar module (RM2) via the path (SP), in the evaluation device, in particular in the additional radar module (RM2), an additional comparison signal (sigC21) is formed from the first signal (sigTX2) of the additional radar module and from a first signal (sigTX1) as received by the first radar module (RM1) via the path (SP), the comparison signal (sigC21) is preferably transmitted, in particular communicated, from the additional radar module (RM2) to the first radar module (RM1); [1] or [2] system. [4] The system, in particular the evaluation device, is configured to form a comparison comparison signal (sigCC21; sigCC12) from the first comparison signal (sigC21) and the additional comparison signal (sigC21), in one of [1] to [3], in particular the system [3]. [5] the system, in particular the evaluation device, is configured in a first step to compensate for deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the radar modules (RM1, RM2) and in a second step to use at least one complex value from a first of the two comparison signals or a signal resulting from this first comparison signal for adjusting the value of at least one complex value of a second of the two comparison signals or a signal resulting from this second comparison signal, thereby forming an adjustment signal (sigCC), the adjustment being performed in such a way that a mathematical operation forms a vector sum or difference of complex values ​​or a phase sum or difference of the complex values, One of the systems [1] to [4], especially [3] or [4]. [6] The system of one of [1] to [5], in particular [4], wherein the comparison signal (sigC21; sigC12) is made to correspond to a comparison signal generated by a coherent radar system by processing the two comparison signals (sigC12, sigC21) with one another, in particular by subjecting them to conjugate imaginary multiplication. [7] the first and / or second radar module (RM1, RM2) comprises at least one, preferably at least two, transmitting antennas and / or at least one, preferably at least two, receiving antennas, and / or a / the first and / or a / the second radar module (RM1, RM2) is / are equipped with up to four, preferably up to three, transmitting antennas and / or up to five, preferably up to four, receiving antennas, One of the systems: [1] through [6]. [8] the radar modules (RM1, RM2, ..., RMN) are positioned far apart from each other such that the aperture resulting from the radar modules is narrow and wide, and / or the radar modules are spaced at least 5 cm apart, preferably at least 10 cm apart, and more preferably at least 40 cm apart, One of the systems: [1] to [7]. [9] The system according to one of [1] to [8], wherein the system, in particular the evaluation device, is configured to estimate, in particular determine, the angular position of surrounding structures by a phase monopulse method and / or by a method in state space.

[10] The system, in particular the evaluation device, is configured to capture surrounding structures using a holographic method, preferably configured to use the holographic method to estimate, in particular to determine, an angular position and / or a (vector) (relative) velocity and / or a (vector) (relative) acceleration of the surrounding structures, and / or the system, in particular the evaluation device, is configured to perform a calibration using the holographic method.

[11] the system, in particular the evaluation device, is adapted to determine the transverse velocity or the velocity vector, in particular by a method of comparing the changes in the differential phase of the reception channels; and / or the system, in particular the evaluation device, is adapted to determine the lateral acceleration or the acceleration vector, in particular by a method of comparing the changes in the differential phase of the reception channels; One of the systems: [1] to

[10] .

[12] The system, in particular the evaluation device, is configured for SAR applications and / or imaging processing.

[13] The system according to any one of [1] to

[12] , wherein the radar modules (RM1, RM2, ..., RMN) are positioned or positionable on the moving object at varying heights, in particular for measuring the heights of surrounding objects in the moving object's environment, preferably by interferometric SAR processing.

[14] The system, in particular the evaluation device, is configured to organize the phase noise part in one term for the variation in the measured spectrum and the variation from the measured spectrum to the measured spectrum, the variation from the measured spectrum being preferably determined as a first separation step.

[15] The system of one of [1] to

[14] , in particular

[14] , wherein the / the variation of the phase noise portion from measurement spectrum to measurement spectrum is determined as a combined portion at both stations from the phase variation in each measurement spectrum, in particular through a scalar product of the two measurement spectra.

[16] The system according to one of [1] to

[15] , in particular

[14] or

[15] , in which two / the two measurement spectra are added together and the amplitudes of the measurement spectra are optionally standardized in advance to an absolute standard or to each other.

[17] A movable object, in particular a vehicle, preferably a motor vehicle, more preferably a motor vehicle and / or a transport device, in particular a crane or part of a crane, comprising one of the systems according to [1] to

[16] .

[18] A method for capturing the surroundings of a moving object, in particular a vehicle and / or transport equipment such as a crane or part of a crane, in particular using a system according to one of [1] to

[16] and / or a mobile object according to

[17] , wherein at least two non-coherent radar modules (RM1, RM2, ..., RMN) are arranged in a distributed manner on and / or at the moving object, and the transmitted and received signals of the radar modules are processed into a modified measurement signal such that they are coherent with each other.

[19] In the method of

[18] , A first signal (sigTX1) is generated in a first radar module (RM1) and transmitted, in particular emitted, via a path (SP), an additional first signal (sigTX2) is generated in an additional, in particular a second radar module (RM2) and transmitted, in particular emitted, via a path (SP); a first comparison signal (sigC12) is formed from the first signal (sigTX1) of the first radar module and from a first signal (sigTX2) as received by the additional radar module (RM2) via the path (SP), an additional comparison signal (sigC21) is formed from the first signal (sigTX2) of the additional radar module and from the first signal (sigTX1) as received by the first radar module (RM1) via the path (SP), The additional comparison signal (sigC21) is preferably transmitted, in particular communicated, from the additional radar module (RM2) to the first radar module (RM1); and / or a comparison signal (sigCC21; sigCC12) is preferably formed from the first comparison signal (sigC21) and the additional comparison signal (sigC21) and / or in a first step deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the transmitting / receiving units (RM2, RM1) are compensated and in a second step at least one complex value from a first one of the two comparison signals or a signal resulting from this first comparison signal is used to adjust the value of at least one complex value of a second one of the two comparison signals or a signal resulting from this second comparison signal, thereby forming an adjustment signal (sigCC), said adjustment being performed such that a mathematical operation forms a vector sum or difference of complex values ​​or a phase sum or difference of said complex values, method.

[20] Use of a system according to one of [1] to

[16] and / or a mobile object according to

[17] and / or a method according to one of

[18] or

[19] for capturing the surroundings of a moving object, in particular a vehicle and / or a transport device such as a crane or a part of a crane, in particular for estimating, in particular determining, the distance and / or the angular position and / or the (vector) (relative) velocity and / or the (vector) (relative) acceleration and / or for capturing the surrounding structure.

Claims

1. A radar system for capturing the surroundings of an object, said system being mounted or mountable on said object, said system comprising at least two non-coherent radar modules (RM1, RM2, ..., RMN) having at least one transmitting antenna and at least one receiving antenna, the radar modules (RM1, RM2, ..., RMN) are arranged or can be arranged on the object in a distributed manner, at least one evaluation device is provided, the evaluation device being configured to process transmitted and received signals of the radar module into modified measurement signals such that the modified measurement signals are coherent with respect to one another, A first signal (sigTX1) is generated in a first radar module (RM1) and transmitted via a path (SP); an additional first signal (sigTX2) is generated in an additional radar module (RM2) and transmitted via said path (SP), said additional first signal (sigTX2) being non-interfering with said first signal (sigTX1); in the first radar module (RM1), a first comparison signal (sigC12) is formed from the first signal (sigTX1) of the first radar module (RM1) and from a first signal (sigTX2) as received from the additional radar module (RM2) via the path (SP), in said additional radar module (RM2) an additional comparison signal (sigC21) is formed from said first signal (sigTX2) of said additional radar module (RM2) and from a first signal (sigTX1) as received from said first radar module (RM1) via said path (SP), the additional comparison signal (sigC21) is transmitted from the additional radar module (RM2) to the first radar module (RM1); The evaluation device processes the transmitted and received signals of the radar module into the corrected measurement signal, In a first step, compensation of deviations in two comparison signals (sigC21, sigC12) caused by systematic deviations in the radar modules (RM2, RM1) is carried out; in a second step, it is arranged to use at least one complex value from a first of the two comparison signals or a signal resulting from this first comparison signal for adjusting the value of at least one complex value of a second of the two comparison signals or a signal resulting from this second comparison signal, thereby forming an adjustment signal (sigCC), said adjustment being performed such that a mathematical operation forms a vector sum or difference of complex values ​​or a phase sum or difference of said complex values, system.

2. The system of claim 1 , wherein the at least two radar modules are connected to each other by a bus system.

3. the first and / or second radar module (RM1, RM2) comprises at least one or at least two transmitting antennas and / or at least one or at least two receiving antennas, and / or a / the first and / or a / the second radar module (RM1, RM2) is / are equipped with up to four or up to three transmit antennas and / or up to five or up to four receive antennas, The system of claim 1 or claim 2.

4. the radar modules (RM1, RM2, ..., RMN) are arranged far apart from each other so that the aperture caused by the radar modules is narrow and wide; and / or the radar modules are spaced at least 5 cm, at least 10 cm, or at least 40 cm apart; A system according to one of claims 1 to 3.

5. 5. The system according to claim 1, wherein the evaluation device is configured to estimate the angular positions of surrounding structures by a phase monopulse method and / or by a method in state space.

6. the evaluation device is configured to capture the surrounding structure using a holographic method; and / or The evaluation device is configured to perform calibration using the holographic method. A system according to one of claims 1 to 5.

7. the evaluation device being adapted to determine the lateral velocity or velocity vector of the object relative to the surrounding structures by means of comparing the changes in the differential phase of the reception channels; and / or the evaluation device being configured to determine a lateral acceleration or an acceleration vector of the object relative to the surrounding structures by means of comparing the changes in the differential phase of the reception channels; A system according to one of claims 1 to 6.

8. The system of claim 1 , wherein the evaluation device is configured for SAR applications and / or imaging processes.

9. 9. The system of claim 1, wherein the at least two radar modules (RM1, RM2, ..., RMN) are positioned or can be positioned on the object at different heights each to measure the heights of surrounding objects in the object's environment by interferometric SAR processing.

10. A movable object comprising a system according to any one of claims 1 to 9, the movable object comprising a vehicle, a motor vehicle, a motor vehicle and / or a transport device, the transport device comprising a crane or part of a crane.

11. A method for capturing the surroundings of an object using a system according to one of claims 1 to 9 and / or a mobile object according to claim 10, characterized in that at least two non-coherent radar modules (RM1, RM2, ..., RMN) are arranged in a distributed manner on and / or at the object, and the transmitted and received signals of the radar modules are processed into a modified measurement signal so as to be mutually coherent, A first signal (sigTX1) is generated in a first radar module (RM1) and transmitted via a path (SP); an additional first signal (sigTX2) is generated in an additional radar module (RM2) and transmitted via said path (SP), said additional first signal (sigTX2) being non-interfering with said first signal (sigTX1); a first comparison signal (sigC12) is formed from the first signal (sigTX1) of the first radar module (RM1) and from a first signal (sigTX2) as received from the additional radar module (RM2) via the path (SP), an additional comparison signal (sigC21) is formed from the first signal (sigTX2) of the additional radar module (RM2) and from the first signal (sigTX1) as received from the first radar module (RM1) via the path (SP), the additional comparison signal (sigC21) is transmitted from the additional radar module (RM2) to the first radar module (RM1); The transmitting and receiving signals of the radar module are processed into a modified measurement signal so as to be coherent with each other, In a first step, deviations in two comparison signals (sigC21, sigC12) caused by systematic deviations in the radar modules (RM2, RM1) are compensated for; in a second step, at least one complex value from a first of the two comparison signals or a signal resulting from this first comparison signal is used to adjust the value of at least one complex value of a second of the two comparison signals or a signal resulting from this second comparison signal, thereby forming an adjustment signal (sigCC), said adjustment being performed such that a mathematical operation forms a vector sum or difference of complex values ​​or a phase sum or difference of said complex values, method.

Images