Method and apparatus for capturing surroundings

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 involve capturing individual isolated targets as accurately as possible, but also good separation (discrimination) of the individual targets.

[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] To a first approximation, the velocity resolution for 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's say.

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

number

[0008] Here, the starting frequency of the signal is f start , the antenna extension (or the antenna aperture in the plane where the angle is measured) is l ant Let's say.

[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. 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 angle measurement.

[0010] According to the prior art, high angular resolution and accuracy can be achieved with large, spatially extensive antenna arrays, as described, for example, in A. Schiessl, A. Genghammer, S. Ahmed, and 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 present problems starting at a certain size with regard to the transmission and coherence length of the individual paths. Additionally, the antennas are rigidly mounted on the HF board. The arrangement of multiple boards and the connecting cables between them is technically very complex and cannot be performed in a stable manner at commonly used frequencies (usually above 10 GHz). Therefore, they do not represent a practical alternative. Overall, the prior art recognizes the problem that known methods for increasing the (azimuth) accuracy and resolution of radar systems are either relatively complex and expensive, or 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 surroundings that allows 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, each having at least one transmitting and at least one receiving antenna. The radar modules are or can be distributedly arranged on the moving object. 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 originating from the latter originate from a common source) so that the modified measurement signals are coherent with respect to each other.

[0015] The central idea of the present 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 signals (which are essentially incoherent with respect to each other), resulting in coherent signals that on the one hand originate from the transmit and receive signals and on the other hand originate from a common source, which allows for an easy (significant) improvement in the accuracy and resolution of the radar system.

[0016] Preferably, the at least two radar modules are 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., 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 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 the first signal as received by the evaluation device from the first radar module and by 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 essentially known from DE 10 2014 104 273 A1. In particular, the content disclosed in DE 10 2014 104 273 A1 is intended to be part of the present disclosure (especially with regard to further developments or specifications of the aspects described in the preceding paragraph), particularly in connection with further developments of the system described in the preceding paragraph. In this regard, the transceiver unit referred to in DE 10 2014 104 273 A1 can be part of a radar module in the present disclosure. Overall, the resolution and accuracy of the surroundings capture can be significantly improved by this functionality, especially when combined with a radar imaging method. In particular, by generating coherence in the basic signal, the radar imaging method can be applied to a larger array, which is possible as a result. The radar imaging method can benefit from a larger array.

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

[0025] In the following, the method according to DE 10 2014 104 273 A1 or the 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 incorporated by reference into the present disclosure, in particular with regard to the formation of a coherent (measurement) signal. The method or arrangement for forming a coherent (measurement) signal according to the just-mentioned application will be referred to below 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 in a second step is configured 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 from 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 Configuration 2 are explained in more detail below. Overall, Method 2 and Configuration 2 provide a radar system that allows a particularly high resolution or accuracy in the capture process, in this case capturing the surroundings, by simple means and without requiring particularly large computational effort, especially when combined with the method for capturing the surroundings.

[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 complex multiplication, correspond to comparison signals generated by means of a coherent radar system.

[0030] The first and / or second radar modules preferably (respectively) comprise at least one, more preferably at least two (particularly separate) transmit antennas and / or at least one, preferably at least two (particularly separate) receive antennas. Alternatively or additionally, the first and / or second radar modules comprise up to four, preferably up to three (particularly separate) transmit antennas and / or up to five (preferably up to four) receive antennas. Thus, the radar module preferably comprises at least one transmit and at least one receive antenna. The transmit and receive antennas can also be designed as a single (combined) transmit / receive antenna (i.e., a single antenna for both transmit and receive). Preferably, multiple transmit / receive antennas are housed in one module, more preferably one to three transmit antennas and two to four receive antennas (this has proven to be an advantageous compromise between size and space allocation in this application). The radar modules (respectively) preferably comprise 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 (each) comprise a device for converting the HF signals to a lower frequency level, for example by means of a mixer or a correlator. The radar module (each) preferably has a separate (local) clock source for the system clock and possibly an A / D converter.

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

[0032] The individual radar modules can be spatially distributed to form a shared aperture for the entire radar system. The antennas of the individual radar modules can represent individual antenna elements. The radar modules are preferably spaced relatively far apart from one another, for example, at least 5 cm apart, preferably at least 10 cm apart, and more preferably at least 40 cm apart. The maximum distance is less than 10 m, preferably less than 5 m, more preferably less than 2 m, and even more preferably less than 1.50 m. Alternatively or additionally, the radar modules are spaced far apart from one another so that the resulting aperture is thin and spread out (i.e., a sparse array in which only a small shared portion of transmit / receive antennas or transmit / receive patches exists across the entire antenna array). Such thin and spread arrays typically have high sidelobes, which can be optimized by individual placement. It is particularly preferred to use at least three radar modules, which further suppresses sidelobes. In particular, a thin and spread array (sparse array) is understood as an array in which the distance between individual transmit / receive devices (antennas) is greater than λ / 2 (λ = the (average) wavelength of the transmitted signal). In particular, a sparse array is also 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] Calibration measurements are preferably performed with the radar modules (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 predetermined angles, (optimal) correction factors can be calculated for each receive path. It is particularly preferred here to adjust the (complex) correction terms for each receive path so that the peak of the known target is as high and narrow as possible. This allows compensation for various phase offsets of the radar modules.

[0034] In particular, when there is redundancy in the measurement signals (with respect to the measurement angles), which may be the case especially when radar modules with multiple transmit / receive paths are used, it is particularly advantageous to perform a self-calibration that does not require a priori knowledge of the exact position of each individual target.From the perspective of an optimization problem, the (complex) correction terms can be adaptively adjusted so that the angle estimations from all radar modules to a given target (ideally) produce consistent results.

[0035] Preferably, the radar system, particularly the evaluation device, is configured to determine the angular position of a surrounding structure using a phase monopulse method. Alternatively or additionally, the system, particularly the evaluation device, can be configured to estimate, particularly determine, a certain angular position of a certain surrounding structure using a state-space method. In general, the radar system can be configured to first separate targets according to distance and velocity criteria, for example, using range-Doppler estimation. The angle can then be determined by an interferometric process (also known in radar engineering as a phase monopulse method). For example, a range-Doppler diagram can be generated here in a first step for each receive channel. Next, for a specific target in the radar spectrum, the phase difference between two (closely) adjacent channels can be determined. To improve accuracy, the phase difference can then be determined for channels located further away. Here, the (now) significantly extended base length between these channels allows for increased accuracy. Preferably, a state-space method is used to improve or enhance angular resolution (particularly for improved sidelobe suppression). Preferably, the MUSIC method described in "R. Schmidt, 'Multiple Emitter Location and Signal Parameter Estimation,' IEEE Proceedings on Antennas and Propagation, Vol. AP-34, No. 3, March 1986 (particularly preferred for sidelobe suppression in sparse arrays)" can be used. Alternatively, or in addition, the Capon method described in "High-Resolution Frequency Wavelength Spectral Analysis,' IEEE Proceedings, Vol. 57, No. 8, August 1969" can be used. The Capon method is particularly preferred because it does not require 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, using coherent signals is relatively difficult because coherent signals have no clear distinction in quantity.In comparison with the application of these methods to direction-of-arrival estimation using far-field approximations, a correction of the hypotheses to be proven (called "steering vectors" in this context) is preferably performed in this application. This can be done, for example, based on hypotheses from holographic methods (see below for details) and, if necessary, after the calculation of the beat spectrum. Alternatively, a closed-form solution can be used using known methods, although 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 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 calibration using holographic methods.

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

[0038] The significantly enlarged aperture can also be used to improve (vector) motion estimation. Previous radar systems typically only estimated the system's radial velocity through the Doppler effect. However, with multiple receive channels, it's also possible to estimate the change in phase difference between the channels, from which lateral velocity can be estimated. However, these basic considerations mean that accurate results are only obtained when the antennas are spaced farther apart. Therefore, it's particularly preferable to construct a sparse array to enable accurate estimation using at least two modules spaced farther apart (e.g., greater than 10 cm). Here, the estimation is preferably achieved using the FMCW chirp sequence method. For example, multiple frequency ramps, e.g., 128 (with identical slopes), can be transmitted simultaneously (or overlapping) by at least two radar modules. The received signals can then be separated, for example, according to "S. Roehr, P. Gulden, and 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 on the indirect paths, for example, according to Method 2 or Configuration 2. Range-Doppler plots can then be calculated (for each path) to determine object position and velocity. From the phase difference of the received channels, angular position can then be determined according to known methods (e.g., using phase monopulse or holography). 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, vector velocity can be determined as the sum of lateral and radial velocities. This method significantly improves periphery capture, since the object's complete motion vector is present in the periphery. If the distance between the radar modules (inter-module base) is large, the accuracy of measuring the lateral velocity improves.

[0039] In particular, when using at least three receiving antennas, it is possible to determine (lateral) acceleration in addition to (lateral) velocity (again by differentiating or subtracting the phase difference changes). By then determining radial acceleration from at least three sequentially recorded radar spectra, it is then possible to determine vector acceleration as well. Again, it is particularly advantageous to space the antennas relatively far apart in this respect.

[0040] Near-field approximation is basically

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 a large (dispersed) aperture is advantageous for SAR applications.

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

[0043] It is also advantageous for the arrangement of three or more systems at different heights, whereby the elapsed 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 are not published at the time of filing.

[0044] In a preferred embodiment, phase noise or phase fluctuations 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 components into a single term for fluctuations within a measurement spectrum (or sweep or ramp) and fluctuations from measurement spectrum to measurement spectrum (or sweep to sweep or ramp to ramp). The fluctuations from measurement spectrum to measurement spectrum are preferably determined (and corrected, if necessary) as a first (separate) step. This allows for a significant improvement in the accuracy of the measurement result. The fluctuations of the phase noise components from measurement spectrum to measurement spectrum are preferably determined as a single (combined) component in two stations from the phase (combined) fluctuations 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, phase noise or phase fluctuations can be easily corrected.

[0045] If necessary, a (preferably differential) correction of drift and / or jitter (especially before phase noise correction) and / or a correction of elapsed time (especially 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 (optionally) independent subject matter of the present invention, as further developments of method 1 and method 2. In this context, the additional features of claim 1 (and of the additional independent claims) may only be optional. For example, the radar module may in this case be arranged stationary.

[0046] One (optionally independent) aspect of the present invention is thus a radar system (with a mobile or stationary radar module or a noncoherent transmit / receive unit), in particular for capturing the surroundings of a (moving or non-moving) object, the system being particularly mounted or mountable on the object, the radar system comprising at least two (particularly distributed) noncoherent radar modules with at least one transmit and at least one receive antenna, the radar modules being particularly distributed or mountable on the object, and at least one evaluation device being provided, configured to process the transmit and receive signals of the radar modules into modified measurement signals that are coherent with respect to each other, whereby phase noise or phase variations are corrected (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 components in one term for variations within a measurement spectrum (or sweep or ramp) and for variations from measurement spectrum to measurement spectrum (or from sweep to sweep or ramp to ramp). The variations from measured spectrum to measured spectrum are preferably determined (and corrected if necessary) as a first (separate) step. The variations in the phase noise portion from measured spectrum to measured spectrum are preferably determined as one (combined) portion at both stations from the phase (combined) variations in each spectrum, preferably through a scalar product of the two measured spectra. The two measured 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 a radar method (using mobile or stationary radar modules or noncoherent transmit / receive units) for capturing the surroundings of an object (moving or non-moving), in particular using the above-mentioned system and / or object, in which at least two noncoherent radar modules are arranged on and / or distributed around the object, and the transmit and receive signals of the radar modules are processed into a modified measurement signal so as to be coherent with each other, with correction for phase noise or phase variations. The phase noise component is preferably organized into a single term for variations within a measurement spectrum (or sweep or ramp) and variations from measurement spectrum to measurement spectrum (or from 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 in the phase noise component from measurement spectrum to measurement spectrum are preferably determined as a single (combined) component at both stations from the phase (combined) variations in each spectrum, preferably through a scalar product of the two measurement spectra. Preferably, the two measured spectra are added. If necessary, the amplitudes of the spectra can be standardized beforehand to an absolute standard or to each other. In particular, phase noise or phase variations can be easily corrected.

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

[0049] An indirect or cross path is understood as a path originating from one (e.g., second) radar module and being received by another (e.g., first) radar module. A direct path is therefore 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 transmitted 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 modules are themselves coherent).

[0051] To the extent that calculations, evaluations, and other processing steps are performed in the radar module(s), these may also include physically self-contained evaluation devices, which are connected to the radar module. For example, each radar module may be designed in this way, 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 structurally connected to such an arrangement as self-contained components. If components are used, the latter may be structurally realizable, but this may consist of processing components, so-called hardware, and / or may be converted into signal or data processing steps that are executed entirely or partly in a processor.

[0052] In general, 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 each radar module or to the remaining parts of each 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 radar module mentioned above. 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 radar signals 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 can form a network.

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

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

[0059] Method 2 begins 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 between the start times of the transmission signals sigTX1 and sigTX2, which may not be initially known, is called T_off. The goal is to ideally have identical transmission times. Preferably, the T_off deviation is no greater than half the signal duration, and in any case, is less than the signal duration. Due to at least partially independent generation, the signals sigTX1 and sigTX2 have uncorrelated signal portions, which may be due to signal source phase noise at the NKSE1 and NKSE2 stations.

[0060] In such an arrangement, the same antenna transmits (T X ) and receive (R X ) is preferably used. In the case of an arrangement in an array (e.g., MIMOO), it has been found that it is preferable for at least one of the multiple transmit paths to exhibit a reciprocal relationship. The use of a transmit mixer in at least one transmit / receive path of the NKSE is particularly suitable for achieving this reciprocal relationship. An exemplary form of realizing a transmit 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 the respective received signal and the transmitted signal, or using a portion of the transmitted signal that is correlated with the transmitted signal or the phase noise. The method for 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 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 signal reception by activation of the signal source and / or directly by compensation in the received signal and / or by compensation in the comparison signal, and in a second step, for example, a shortened evaluation of the correlation or formation of the comparison signal only for the predicted deviation area or only for at most one deviation value.

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

[0064] Multiplication or division of signals constitutes a nonlinear operation. Nonlinear operations always involve nonlinear effects, specifically so-called intermodulation of signal and noise components. This creates problems, especially in the case of radar signals with multiple signal components, i.e., 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 nonlinear operation, thereby avoiding nonlinear effects, specifically intermodulation of signal and noise components. Overall, this embodiment variant allows for a significantly 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 that are foreseen in DE 10 2014 104 273 A1. Furthermore, this approach is technically advantageous, since the required computational effort is significantly lower than that required for a full multiplication or correlation, as proposed as an embodiment in DE 10 2014 104 273 A1.

[0066] To be able to process according to method 2, it is preferable to first perform precise (controllable hardware) direct and / or synthetic (computer) synchronization so as to compensate (at least largely) for the frequency offset. After that, a linearization approach can be used to cancel the correlated part of the impairment, subject only to a small residual phase difference (principle shown in Figure 3).

[0067] Here, synchronization can take place separately before the measurement, 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 either directly (eg via a TCXO) or computationally (synthetic synchronization).

[0069] Any known method 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 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 way the clock source is adjusted, it is possible to use a very high quality clock source, such as a radio-controlled clock.

[0072] After the combining step, the comparison signal can be derived from the signals (sigEP21, sigEP12), each of which represents a function having as a function argument 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 the comparison signals of at least two NKSEs, where the offset is determined by the maximum value. Alternatively, the following method can also be used for FMCW signals. As before, the method can be implemented either by cord connection 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. 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 the impairments of 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 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 between the signals sigC21 and sigC12 caused by systematic deviations in the transmitting / receiving units (NKSE2, NKSE1) are compensated, in a second step, using at least one complex value from a first of the two comparison signals or from a signal resulting from this first comparison signal to adjust at least one complex value from a second 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 explanation of the drawings]

[0078] Exemplary embodiments are explained in more detail below on the basis of the drawings. [Figure 1] Figure 1 shows two transmitting and receiving units communicating with each other and their individual components. [Figure 2]FIG. 2 shows the parts from FIG. 1 along with the processing sequence. [Figure 3] FIG. 3 shows the beat signals of two transmit and receive units with uncorrelated noise parts before synchronization (top), and the combined mixture with correlated phase noise after synchronization (bottom). [Figure 4] Figure 4 shows the spectrograms of all lamps from the two transmitting and receiving units before synchronization. [Figure 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 distributed radar modules in a motor vehicle. [Figure 6c] FIG. 6c shows various embodiments of distributed radar modules 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 the spectrogram of the first radar module, where the horizontal axis shows the distance in meters and the vertical axis shows the number of chirps or ramps. [Figure 11b] FIG. 11b shows the spectrogram of the second radar module, where the horizontal axis shows the 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 indicates the distance in meters and the vertical axis indicates 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 indicates the distance in meters and the vertical axis indicates the number of chirps or ramps. [Figure 13a] FIG. 13a shows an additional spectrogram of the first radar module after correction for drift and jitter, where the horizontal axis shows distance in meters and the vertical axis shows the number of chirps or ramps. [Figure 13b] FIG. 13b shows an additional spectrogram of the second radar module after correction for drift and jitter, 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 indicates distance in meters and the vertical axis indicates the number of chirps or ramps. [Figure 14b] FIG. 14b shows an additional spectrogram of the second radar module after correction for time and frequency offsets, where the horizontal axis indicates distance in meters and the vertical axis indicates chirp or ramp number. [Figure 15a] FIG. 15a shows the phase advance of the first radar module without 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 15b] FIG. 15b shows the phase advance of the second radar module without 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 16a] FIG. 16a shows the phase advance of the first 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 16b]FIG. 16b shows the phase advance of the second radar module with correction for the phase deviation, where the horizontal axis shows the number of chirps or ramps and the vertical axis shows the phase in radians. [Figure 17a] Figure 17a shows the 2D-(FFT) spectrum of the cross-path of the first radar module with correction for drift and jitter and time and frequency offset, where the horizontal axis shows the speed in meters per second and the vertical axis shows the magnitude in decibels (dB). [Figure 17b] Figure 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 the speed in meters per second and the vertical axis shows the magnitude in decibels (dB). [Figure 18a] Figure 18a shows the 2D-(FFT) spectrum of the cross-path of the first radar module with correction for drift and jitter and time and frequency offset and phase variation, where the horizontal axis shows the speed in meters per second and the vertical axis shows the magnitude in decibels (dB). [Figure 18b] Figure 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 variations, where the horizontal axis shows the speed in meters per second and the vertical axis shows the 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 represents the speed in meters per second and the vertical axis represents 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 INVENTION

[0079] As shown in Figure 1, two transceiver units NKSE1 and NKSE2 communicate with each other via a radio interface. A first or second signal sigTX1 or 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 units preferably consist of radar modules. In the following, NKSE1 can thus be considered as the first radar module and NKSE2 as the second radar module.

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

[0081] Below 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). Ideally, these signals are emitted simultaneously, but at least they are synchronized with each other so that the two signal waveforms preferably overlap for at least half of 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 present invention is preferably used for distance measurement or 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, and Barker codes, Kasami sequences, Huffman sequences, chirps, linear frequency modulated waves (FMCW), chirps, or FMCW sequences. Various types of such signal formats have long been known in radar engineering and communications engineering (especially in the field of CDMA).

[0084] The transmission signal (sigTX1) of the transmitting / receiving 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 transmit / receive unit (NKSE2) can be formed in a similar manner.

number

[0089] The transmitted signals (sigTX1 and sigTX2) arrive at the other transmitting / receiving stations, either directly or after being reflected by an object, 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 (single) transmit paths of varying lengths, 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, signal sigRX12 is offset with signal sigTX1, and in NKSE2, signal sigRX21 is offset with signal sigX2. In this exemplary embodiment, the signal comparison units SigComp1 and SigComp2 are designed as mixers Mix. That is, in NKSE1, signal sigRX12 is mixed with signal sigTX1, and in NKSE2, signal sigRX21 is mixed with signal sigTX2. This mixing process, which is generally known, can be expressed as a multiplication from the perspective of system theory, or as a downmixing, assuming that two complex sinusoidal signals are multiplied by the complex conjugate (*=conjugate sign) of one of the signals. Therefore, the following 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 means is provided on the NKSE to ensure that the following conditions are met:

number

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

number

number

[0099] In the next step, data communication is used to send both comparison signals to a shared evaluation unit and ensure that both are present 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 consider only the carrier phase with the 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 component usually drops off rapidly in oscillators with increasing distance from the carrier based on known correlations of oscillator phase noise, and that φTX1 or φTX2 consequently exhibits a pronounced low-pass behavior, especially at a cut-off frequency that is usually significantly lower than 1 / τ, we obtain:

number

number

[0102] In the proposed process, the phases of the other comparison signals are summed for one of the comparison signals, resulting in a significant reduction in interference from phase noise, which increases the likelihood of target detection, extends the measurement range, and improves measurement accuracy.

[0103] Depending on the mixer topology chosen, for example, whether co-located or inverted mixers are used, the phase terms presented above can have different signs. Depending on the signs, the preferred combination of the phase terms is not necessarily additive, but may also be 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 conjugate of each other, to form the phase sum or difference.

[0104] Possible preferred variants for reducing the phase noise portion 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 the following applies in at least approximate reciprocal radio channels: 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 be introduced in the formation of signals sigC12 and sigC21. If the phase offsets of 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 cancels vector components of phase terms with different signs. As one possible preferred variation 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, signal sigCC has significantly lower phase noise than signals sigC12 or sigC21, and signal sigCC can be used for distance measurement, angle measurement, or imaging purposes. However, before adding the signals, it is important to compensate for the systematic amplitude and phase deviations mentioned above, which lead to different carrier frequencies and transmission times.

[0112] Of course, it is not necessary to add all values for sigC12 and sigC21, nor for 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 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 the vector sum or difference of the at least two complex values resulting from sigC12 and sigC21, or the phase sum or difference of these complex values, is formed by a mathematical operation.

[0113] It should be noted here that the proposed mixing process represents only one possible embodiment, and that the phase noise portion 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] Essentially, the transmit signals sigTX1 and sigTX2 can be FMCW modulated, where it is preferable to normalize the spectrum of the comparison signal to its highest value (before the mathematical operations).

[0115] Below, we describe a specific embodiment of Method 2 using an FMCW signal and multiple consecutive N ramps. Here, 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 because they allow relative speeds 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 include 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 primary radar use, at least one reflecting object in the detection field must be identified for this step and represented as described above.

[0117] Here, we generously cut out the frequency band where beat signals are expected (ensuring rough synchronization). Next, we correlate each spectrogram of the first N / 2 ramps with each spectrogram of the second N / 2 ramps along the frequency axis (step 1). The maximum value found in this step reflects the relative time drift of the two NKSEs (a linear function can be assumed here). For example, if a signal is received via one or more reflections, we can also identify the target via the opposite drift on both sides.

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

[0119] All ramps in the spectrogram are then corrected for this drift, for example by multiplying them by a composite correction signal with the opposite frequency offset in unit 2 for clock adjustment or comparison signal correction. The spectrograms of the various 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 primary radar, the identification in the previous step of co-located peaks can be used to select the peaks.

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

[0121] The relative time delay and relative time drift parameters (= current frequency offset) determined in this way 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 displaced by the integer value Tint (the time delay between the two stations, expressed as ΔT = |T01 - T02| = Tint + Tfrac) to obtain a uniform time base. A shared, precise time base allows for stronger phase noise correlation. The remaining small time error Tfrac can be compensated for, for example, using a fractional delay filter. The displaced signals are then corrected for the misaligned ramp slopes caused by the frequency offset Δω = ω1 - ω2 of the two local oscillators by folding or spectrally multiplying them 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 refined mixed signals is performed. In the case of a secondary radar, it is preferable to select the strongest or first peak. For a primary radar, a peak equally distributed on both sides must be selected. Thus, a maximum value is generated for each ramp at both stations with the associated phase position and estimated distance. In principle, these values will coincide with each other based on measurements of the round-trip path in the inter-channel. The source of any remaining deviations can be the residual frequency and phase difference between the two signal sources 1, e.g., the oscillators responsible for the phase noise that is the root cause of NKSE. In this way, the exact frequency difference can be reliably determined and corrected (the phase difference can be determined with an ambiguity of up to 180° (360° for an IQ mixer)). This ambiguity can be eliminated by limiting the phase advance from ramp to ramp to ±90°, also known as unwrapping. After accurately correcting the remaining phase error in this way, there is almost no difference between the combined mixed signals of both stations.

[0124] After this preprocessing, the systematic errors inherent in the radar system are fully corrected, resulting in a small phase shift difference between the two beat signals. Here, on the one hand, 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 linear combination. This can be done, for example, by a 2D Fourier transform of all N ramps in both NKSEs, where the amplitude-normalized beat signals are finally summed. The maximum value 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 a schematic configuration 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, using four sensors). In FIG. 6b, three radar modules are arranged in the front, specifically in the front left, front center, and front right (no radar modules are arranged in the rear). This results in a particularly advantageous capture of the surroundings in the direction of travel (in this case, using three sensors). In FIG. 6c, eight radar modules are used in this case (front left, front center, front right, rear left, rear center, rear right, and radars on both sides), which results in a particularly comprehensive capture of the surroundings.

[0127] An embodiment for holographic evaluation will now be described with reference to Figure 7. For the present application, the holographic calculation can be performed as follows. The calculation space can be represented by individual points in space. The placement of the transmit and receive antennas in or relative to the calculation space is (usually) known. For each point in space, the resulting composite signal (amplitude, phase, frequency) for the propagation path (from virtual transmit antenna a to virtual receive antenna b) can be calculated. 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 space. This process is repeated for all k propagation paths for a point in space, each of which is (compositely) added to the previous calculation result. This sum represents the distribution probability for this point in space. This process can be repeated for all n, m points in 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 regarding the phase position for each transmitted and received signal combination can be presented for each point in space, corresponding to the expected phase shift along this propagation path (from tentative transmitting antenna a to tentative receiving antenna b). The expected phase position can be expressed as

number

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

[0131] This holographic processing can also be carried out at the velocity and acceleration level. Thus, the velocity and acceleration vectors can be determined (holographically) 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 present invention will be described below with reference to FIG. 8. Radar measurements can be made and recorded in SAR imaging along a specific travel path. These can be mathematically combined, as if by combining elements from each location where measurements were recorded using an antenna array. In the prior art, radars are used for this purpose to generate a synthetic aperture over the entire travel length. By using two radars whose signals are coherent with each other, the radar data from both sensors and an additional path between the radars can be used, reducing the traverse path required for illumination. For this reason, radar systems with large apertures are advantageously equipped, with the signals corrected by post-processing as if they were generated by coherent radar. In this way, the radar signals from 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), and Figure 10 shows a schematic vehicle with an exemplary sensor arrangement (arrangement of modules).

[0134] Measuring the height of an object is a major obstacle, especially in the field of autonomous driving, because current environmental sensors typically only estimate the range, speed, and azimuth angle of targets in the vehicle's environment. According to M.A. 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 system's antennas are tilted downward, and forward and downward beaming directional characteristics can also be advantageous (depending on the situation). The achievable accuracy is largely limited by the height difference between the receiving antennas. Relatively high accuracy is particularly advantageous in distinguishing between roadway objects such as curbs, fences, posts, traffic signs, manhole covers, and garbage (here, for example, drink containers and small bags do not represent meaningful roadway objects), but also in detecting and distinguishing between 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 Electronic Systems Magazine, Vol. 22, No. 9, pp. 5-29, 2007, the accuracy of 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 for the differential distance and can be determined very accurately, for example, using phase comparison. In the present invention, additional receiving elements (modules) can be placed on the vehicle as desired (or at least essentially as desired), thereby significantly increasing the reference line B. For example, by placing one radar module on the bumper and a second radar module on the vehicle's roof, accuracy can be improved by a factor of 10 (compared to a single small radar module with multiple receiving elements). Exemplary installation locations are shown in FIG. 10. Specifically, side mirrors 16 are shown on the bumper 15 and / or on the roof (roof rails) 17.

[0136] Methods for reducing interference components, in particular phase noise, are described based on diagrams according to Figures 11a, 11b to 20a, 20b. These methods are also described as further developments of Method 1 or Method 2 as (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) transceiver units according to method 1 or method 2. The modules (transceiver 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 placement, although this is possible.

[0138] 11a shows the spectrum of the 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 drift Td and jitter Tj, so that the beat frequency varies with respect to the signal duration (i.e., a sequence of, for example, 128 lamps). 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 Figure 12a (for the first radar module) and Figure 12b (for the second radar module). These depictions 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 in 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 a further (complete) evaluation.

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

number

[0142] In principle, the mixed signal has an 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., approximately 78 GHz) τ: elapsed time, cross path τ l :Change in elapsed time due to object movement T off,l =T off,0 +T j,l +l·T D Timing offset (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 variations between stations and individual channels Δ f : Frequency offset (e.g., 350 kHz) μ: sweep speed (e.g., 500 GHz / 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 during the measurement period.

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

number

[0146] This description is essentially independent of the window function selected, so the latter can be omitted. The phase noise in the station's mixed signal 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 two points in time is important for the variance of the phase noise (Allan variance), the manifestations at both stations are approximately the same (φ p、1l (t)~φ p、2l (t)). Local oscillator Ψ p,1l and Ψ p,2l The phase noise in 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 via a Fourier transform, for example from a Hilbert transform (which may be necessary if I / Q data is not available).

[0149] As can be seen from the spectra in Figures 11a and 11b, the cross-path beat frequency increases (approximately) linearly over time, and there can also be ±1 clock jitter. This may be due to the fact that each radar module uses a different clock source. In the modified version, this can be eliminated and can be formulated as follows:

number

[0150] Now, the drift TD as well as 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 off as a (large) interval so that the resulting signal also contains information about (far) distant targets (with a larger beat frequency in the second radar module). In this case, equation (2) describes all 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:

number

[0155] where 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 of 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 folding 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 It can be divided into three subsequences denoted by , successively with jumps 0, J0 and -J0.

[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 , the sequence D1 = μ(T j,l -T j、l+1 -T D ) and correct for jitter and drift if necessary. Figures 13a and 13b show the spectrograms of both modules (Figure 13a for the first radar module and Figure 13b for the second radar module) after drift and jitter correction.

[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 be an obviously small portion of residual jitter, which is compensated for in other processing steps.

[0164] For example, synchronization via the CAN bus could prevent drifts between 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 small (negligible).

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

[0166] The time lapse through the synchronization cable or the (configured) 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 the chirp, i.e., with respect to the ramp number l. Therefore, the sum

number

number

[0168] The spectrum of one station is arbitrarily reflected at 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 separated by a small distance, which allows a certain level of crosstalk to be recognized as a "target" at 0 m).

[0170] The correction of the phase fluctuation will be explained 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 matches 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 a 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 modification 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 a term

number

[0178] This means that the phase jump between adjacent ramps may be too large for phase tracking over a large number of measurements. In particular, the maximum expected phase jump may limit the measurement range in terms of Doppler frequency and therefore the maximum detectable velocity. Improving the synchronization of the two stations can alleviate this problem. Deviations remaining after adjusting the clock speed may no longer cause phase jumps to occur across the uniqueness region between adjacent sweeps.

[0179] Spectral adjustment and overlapping are described below.

[0180] Before superimposing the two spectra, an adjustment can be made to compensate 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 be described below.

[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 Figures 17a and 17b (which show plots without the corrected phase variation, while Figures 18a and 18b show plots with the corrected phase variation, Figures 17a and 18b for the first module, and Figures 18a and 18b for the second module), from which velocities can be derived relatively accurately. Residual phase noise, much stronger than that of the primary radar response, appears on the cross-path in the form of randomly distributed small peaks. These are distributed across all velocities and are (pseudo) identical in the first and second modules (but 180 degrees out of phase). After adding both 2D spectra, a spectrum (except potentially for relatively small amplitude noise) corresponding to the primary radar (see Figure 20a for the first module and Figure 20b for the second module) is generated (see Figure 19). This leads to much more measurement dynamics, where weak targets (in a strong target environment) can also be recognized. Since varying azimuth angles can introduce additional phase offsets, this method is shown here for individual channels.

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

[0186] The (coherent) processing of frequency shifts caused by the Doppler effect can be smoothly performed through 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 for further accuracy.

[0188] It can be seen that a rough synchronization (pre-synchronization) is basically possible by supplying an external regulated clock, for example via the CAN bus (of the motor vehicle), which reduces the computational effort of the method and reduces 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 estimation of speed, azimuth angle and distance, which in particular facilitates tracking.

[0190] Reflections from complex objects can be recognized relatively easily, possibly even if 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 major influence on the latter.

[0191] By combining multiple radar modules in the direction of elevation, 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 method 1 or 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 the 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 its first signal (sigTX2) and from the 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, the 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 complex multiplication, so as to correspond 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 and 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 a preceding aspect, the point in time at which the first signals (sigTX1, sigTX2) are transmitted is 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 transmitting and receiving units (NKSE1, NKSE2) is determined from at least one comparison comparison signal (sigC21; sigC12) by analyzing at least one of the phase or phase values of the frequency (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 time sequence using at least two transmitting / receiving units (NKSE1, NKSE2), and 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 said transmitting / receiving units (NKSE2, NKSE1), or the presence of such 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, 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 at least one of 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 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 evaluation device (P) are designed to implement a method according to one of the preceding aspects.

[0208] Aspect 16: An apparatus, in particular of a radar system 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) designed to generate and transmit a first signal (sigTX1) via a path (SP), in particular to emit the first signal (sigTX1); an arrangement designed to form a comparison signal (sigC12) from said 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 transmitting / receiving unit (NKSE2), or an interface (CommRX) designed to transmit, in particular communicate, receive in said first transceiver unit (NKSE1) an additional comparison signal (sigC21) as generated by said additional transceiver unit (NKSE2), 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] Aspect 18: In the device according to aspect 16 or 17, the at least one interface (CommTX, CommRX) is a data interface.

[0211] Aspect 19: In the device according 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, comprising 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 the first signal (sigTX2) and from the first signal (sigTX1) as received by such additional transceiver unit (NKSE2) via the path (SP).

[0213] Aspects and embodiments of Method 2 or Configuration 2 are described below, where reference numbers relate to Figures 1 to 4 of the present application. The transceiver unit can 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, where they are further processed 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 the 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 and receiving units (NKSE2, NKSE1) are compensated; 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); The 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 of the signal sources, in particular of the first signals (sigTX1 and sigTX2), is performed via a bus system, preferably a communication bus, and / or the clock speed adjustment of the signal sources, in particular of the clock speed 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 and receiving units (NKSE1, NKSE2), in particular the pre-synchronization by determining the frequency offset, is performed successively over multiple ramps, in particular when using a secondary radar.

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

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

[0220] Aspect 7: In a method according to one of the preceding aspects, the first and / or the additional (non-coherent) transceiver unit comprises at least one evaluation device for performing individual processing steps, in particular calculations and evaluations, and each evaluation device: 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 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 transmitted in particular to a shared evaluation unit, where both are present for evaluation, and the shared evaluation unit is 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 before 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 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 transmitting, in particular emitting, said first signal (sigTX2) via a path (SP), said (non-coherent) transmitting and receiving units (NKSE1 and NKSE2) are designed to directly or indirectly receive said first signals (sigTX1 and sigTX2) and then process them further 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 the first signal (sigTX1) as received by said first transceiver unit (NKSE1) via said path (SP), a transmitting unit, in particular for communicating, for transmitting said additional comparison signal (sigC21) from said additional transmitting / receiving unit (NKSE2) to said first transmitting / receiving unit (NKSE1); At least one evaluation unit is provided, which is designed to, in a first step, compensate for deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the transmitting / receiving units (NKSE2, NKSE1), and to, in a second step, 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 in such a way that a mathematical operation forms a vector sum or difference of complex values or a phase sum or difference of said 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 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 transmission mixer is provided in the 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 each of the first and / or second (non-coherent) transmit / receive units (NKSE1 and / or NKSE2).

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

[0229] It should be noted that at this stage all the components or features described above, 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 those skilled in the art.

Claims

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 one another; Radar system.

2. The system of claim 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 the 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); The system of claim 1 or claim 2.

4. 4. The system according to claim 1, in particular claim 3, wherein the evaluation device is configured to form a comparison signal (sigCC21; sigCC12) from the first comparison signal (sigC21) and the additional comparison signal (sigC21).

5. the system, in particular the evaluation device, is configured to compensate in a first step for deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the radar modules (RM1, RM2), and to use 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 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 adjusted 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. A system according to one of claims 1 to 4, in particular claim 3 or 4.

6. 6. The system of claim 1, wherein the comparison signal (sigC21; sigC12) corresponds to a comparison signal generated by a coherent radar system by processing the two comparison signals (sigC12, sigC21) together, in particular by subjecting them to a conjugate complex 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) comprises up to four, preferably up to three, transmitting antennas and / or up to five, preferably up to four, receiving antennas, A system according to one of claims 1 to 6.

8. the radar modules (RM1, RM2, ..., RMN) are spaced far apart from one another so that the apertures resulting from the radar modules are narrow and wide, and / or the radar modules are spaced at a distance of at least 5 cm, preferably at least 10 cm, and more preferably at least 40 cm, A system according to one of claims 1 to 7.

9. 9. The system according to claim 1, 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. 10. The system according to claim 1, wherein 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 determine, angular positions and / or (vector) (relative) velocities and / or (vector) (relative) accelerations of the surrounding structures, and / or the system, in particular the evaluation device, is configured to perform calibration using the holographic method.

11. the system, in particular the evaluation device, is adapted to determine the transverse velocity or velocity vector, in particular by comparing the changes in the differential phase of the reception channels; and / or the system, in particular the evaluation device, is configured to determine the lateral acceleration or the acceleration vector, in particular by comparing the changes in the differential phase of the reception channels; A system according to one of claims 1 to 10.

12. 12. The system according to claim 1, wherein the system, in particular the evaluation device, is configured for SAR applications and / or imaging processes.

13. 13. The system of one of claims 1 to 12, wherein the radar modules (RM1, RM2, ..., RMN) are positioned or positionable on the moving object at varying heights, preferably by interferometric SAR processing, in particular to measure the heights of surrounding objects in the environment of the moving object.

14. 14. The system according to claim 1, wherein the evaluation device is configured to organize the phase noise components into one term for variations within the measurement spectrum and variations from measurement spectrum to measurement spectrum, the variations from measurement spectrum to measurement spectrum being preferably determined as a first separation step.

15. A system according to one of claims 1 to 14, in particular claim 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. 16. A system according to one of claims 1 to 15, in particular claim 14 or 15, wherein 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 a system according to one of claims 1 to 16.

18. 16. 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 claims 1 to 16 and / or a mobile object according to claim 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 in such a way that they are coherent with each other.

19. 20. The method of claim 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 the 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 the 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 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; method.

20. Use of a system according to one of claims 1 to 16 and / or a movable object according to claim 17 and / or a method according to one of claims 18 or 19 for capturing the surroundings of a moving object, in particular a vehicle and / or transport device such as a crane or part of a crane, in particular for estimating, in particular determining, the distance and / or angular position and / or (vector) (relative) velocity and / or (vector) (relative) acceleration and / or for capturing the surrounding structure.

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