METHOD AND APPARATUS FOR CAPTURING THE SURROUNDINGS

Abstract

The invention relates to a radar system for capturing surroundings of a moving object, in particular a vehicle and/or a transportation apparatus, such as a crane, in particular, wherein the system is mounted or mountable on the moving object, wherein the radar system comprises at least two non-coherent radar modules (RM 1, RM 2, . . . RM N) having at least one transmitter antenna and at least one receiver antenna, wherein the radar modules (RM 1, RM 2, . . . RM N) are arranged or arrangeable in distributed fashion on the moving object, wherein provision is made of at least one evaluation device which 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.

Claims

1. A radar system for capturing the surroundings of an object in particular a moved object, in particular of a vehicle and/or a transport device, such as in particular a crane, wherein the system is mounted or mountable on the object, wherein the radar system comprises at least two non-coherent radar modules (RM 1, RM 2, . . . , RM N) with at least one transmitter and at least one receiver antenna, wherein the radar modules (RM 1, RM 2, . . . , RM N) are arranged or arrangeable on the object in a distributed fashion, wherein at least one evaluation device is provided, which is configured to process transmitted and received signals of the radar modules into modified measurement signals in such a way that the modified measurement signals are coherent in relation to each other, wherein the system, in particular the evaluation device, is configured to organize the phase noise portion in one term for a variation within a measuring spectrum and a variation from measuring spectrum to measuring spectrum, wherein the variation from measuring spectrum to measuring spectrum is preferably determined as a first, separate step.

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

3. The system according to claim 1, wherein a first signal (sigTX1) is generated in a first radar module (RM 1) and transmitted, in particular emitted, over a path (SP), an additional first signal (sigTX2) is generated in an additional, in particular a second, radar module (RM 2), and transmitted, in particular emitted, over a path (SP), in the evaluation device, in particular in the first radar module (RM 1), a first comparison signal (sigC12) is formed out of the first signal (sigTX1) of the first radar module and out of such a first signal (sigTX2) received by the additional radar module (RM 2) over the path (SP), and, in the evaluation device, in particular in the additional radar module (RM 2), an additional comparison signal (sigC21) is formed out of the first signal (sigTX2) of the additional radar module and out of such a first signal (sigTX1) received by the first radar module (RM 1) over the path (SP), wherein the additional comparison signal (sigC21) is preferably transmitted, in particular communicated, from the additional radar module (RM 2) to the first radar module (RM 1).

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

5. The system according to claim 3, wherein the system, in particular the evaluation device, is configured in a first step to compensate for deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the radar modules (RM 2, RM 1), and in a second step to use at least one complex value from a first of the two comparison signals or a signal derived from his first comparison signal to adjust at least one complex value of the second of the two comparison signals or a value of a signal that was derived from this second comparison signal, and thereby form an adjusted signal (sigCC), wherein the adjustment takes place in such a way that a mathematical operation forms the vectorial sum or the difference of complex values, or forms the sum or the difference of the phases of the complex values.

6. The system according to claim 4, wherein the comparison-comparison signal (sigC21; sigC12) is made to correspond with a comparison signal generated by a coherent radar system by processing the two comparison signals (sigC12, sigC21) with each other, in particular subjecting them to conjugated complex multiplication.

7. The system according to claim 1, wherein a first and/or a second radar module (RM 1, RM 2) has/have at least one, preferably at least two transmitter antenna(s) and or at least one, preferably at least two receiver antenna(s), and/or wherein a/the first and/or a/the second radar module (RM 1, RM 2) has/have at most four, preferably at most three, transmitter antennas and/or at most five, preferably at most four, receiver antennas.

8. The system according to claim 1, wherein the radar modules (RM 1, RM 2, . . . , RM N) are arranged so far apart from each other that an aperture resulting from the radar modules is spread thin and/or wherein the radar modules have a distance between them of at least 5 cm, preferably at least 10 cm, further preferably at least 40 cm.

9. The system according to claim 1, wherein the system, in particular the evaluation device, is configured to estimate, in particular determine, an angular position of a surrounding structure by means of a phase monopulse method and/or by means of a method in the state space.

10. The system according to claim 1, wherein the system, in particular the evaluation device, is configured to capture a surrounding structure using the holography method, preferably to use the holography method for estimating, in particular determining, an angular position and/or a (vectorial) (relative) velocity and/or a (vectorial) (relative) acceleration of the surrounding structure, and/or wherein the system, in particular the evaluation device, is configured to perform a calibration using the holographic method.

11. The system according to claim 1, wherein the system, in particular the evaluation device, is configured to determine a lateral velocity or a velocity vector, in particular by means of a method for comparing a change in the differential phases of reception channels, and/or wherein the system, in particular the evaluation device, is configured to determine a lateral acceleration or an acceleration vector, in particular by means of a method for comparing a change in the differential phases of reception channels.

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

13. The system according to claim 1, wherein the radar modules (RM 1, RM 2, . . . , RM N) are arranged or arrangeable on the object at a varying height, in particular for measuring a height of a surrounding object in an environment of the object, preferably by means of interferometric SAR processing.

14.-16. (canceled)

17. A movable object, in particular a vehicle, preferably a motor vehicle, further preferably an automobile and/or transport device, in particular such as a crane or part of a crane, comprising a system according to claim 1.

18. A method for capturing the surroundings of an object, in particular a moving object according to claim 17, wherein at least two non-coherent radar modules (RM 1, RM 2, . . . , RM N) are arranged on and/or in the moving object in a distributed fashion, wherein the transmitted and received signals of the radar modules are processed into modified measurement signals, such that the modified measurement signals are coherent relative to each other, wherein the phase noise portion is organized in one term for a variation within a measuring spectrum and a variation from measuring spectrum to measuring spectrum, wherein the variation from measuring spectrum to measuring spectrum is preferably determined as a first, separate step.

19. The method according to claim 18, wherein a first signal (sigTX1) is generated in a first radar module (RM 1) and transmitted, in particular emitted, over a path (SP), an additional first signal (sigTX2) is generated in an additional, in particular a second, radar module (RM 2), and transmitted, in particular emitted, over a path (SP), a first comparison signal (sigC12) is formed out of the first signal (sigTX1) of the first radar module and out of such a first signal (sigTX2) received by the additional radar module (RM 2) over the path (SP), and an additional comparison signal (sigC21) is formed out of the first signal (sigTX2) of the additional radar module and out of such a first signal (sigTX1) received by the first radar module (RM 1) over the path (SP), wherein the additional comparison signal (sigC21) is preferably transmitted, in particular communicated, from the additional radar module (RM 2) to the first radar module (RM 1), and/or wherein a comparison-comparison signal (sigCC21; sigCC12) is preferably formed out of the first comparison signal (sigC21) and the additional comparison signal (sigC21) and/or wherein, in a first step, deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the transmitter-receiver units (RM 2, RM 1) are compensated, and in a second step, at least one complex value from a first of the two comparison signals or a signal derived from this first comparison signal is used to adjust at least one complex value of the second of the two comparison signals or a value of a signal that was derived from this second comparison signal, and thereby form an adjusted signal (sigCC), wherein the adjustment takes place in such a way that a mathematical operation forms the vectorial sum or the difference of complex values, or forms the sum or the difference of the phases of the complex values.

20. Use of a system according to the method of claim 18 for capturing a surroundings of a moving object for determining a distance and/or an angular position and/or a (vectorial) (relative) velocity and/or a (vectorial) (relative) acceleration and/or for imaging a surrounding structure.

21. The system according to claim 1, wherein the variation of the phase noise portion from measuring spectrum to measuring spectrum is determined as a combined portion in both stations from the variation of the phase in each measuring spectrum, in particular via the scalar product of the two measuring spectra.

22. The system according to claim 1, wherein the two measuring spectra are added, wherein the amplitudes of the measuring spectra are optionally standardized to an absolute normal or relative to each other beforehand.

23. The method according to claim 17, wherein the variation of the phase noise portion from measuring spectrum to measuring spectrum is determined as a combined portion in both stations from the variation of the phase in each measuring spectrum, in particular via the scalar product of the two measuring spectra.

24. The system according to claim 17, wherein the two measuring spectra are added, wherein the amplitudes of the measuring spectra are optionally standardized to an absolute normal or relative to each other beforehand.

Description

[0084] Exemplary embodiments will be explained in more detail below based on the figures.

[0085] Shown on:

[0086] FIG. 1 are two transmitter-receiver units that communicate with each other, and individual components thereof;

[0087] FIG. 2 are the components from FIG. 1, with illustration of a process sequence;

[0088] FIG. 3 are beat signals of the two transmitter-receiver units with non-correlated noise portions prior to synchronization (top) and a synthetic mixed product with correlated phase noise after synchronization (bottom);

[0089] FIG. 4 are spectrograms of all ramps from the two transmitter-receiver units prior to synchronization;

[0090] FIG. 5 is a schematic view of a configuration of several radar modules;

[0091] FIG. 6A-6C are various embodiments for radar modules distributed on a motor vehicle;

[0092] FIG. 7 is a diagram concerning a holographic evaluation;

[0093] FIG. 8 is a schematic view of an SAR imaging;

[0094] FIG. 9 is a schematic view concerning an interferometric SAR;

[0095] FIG. 10 is a schematic view of a vehicle with sensor array;

[0096] FIG. 11a is a spectrogram for the first radar module, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0097] FIG. 11b is a spectrogram for the second radar module, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0098] FIG. 12a is an additional spectrogram for the first radar module, wherein only a primary response was evaluated, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0099] FIG. 12b is an additional spectrogram for the second radar module, wherein only a primary response was evaluated, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0100] FIG. 13a is an additional spectrogram for the first radar module, after a correction for drift and jitter, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0101] FIG. 13b is an additional spectrogram for the second radar module, after a correction for drift and jitter, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0102] FIG. 14a is an additional spectrogram for the first radar module, after a correction for time and frequency offset, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0103] FIG. 14b is an additional spectrogram for the second radar module, after a correction for time and frequency offset, wherein the horizontal axis indicates a distance in meters, and the vertical axis indicates a chirp or ramp number;

[0104] FIG. 15a is a phase progression for the first radar module, without any correction for phase deviation, wherein the horizontal axis indicates a chirp or ramp number, and the vertical axis indicates a phase in radians;

[0105] FIG. 15b is a phase progression for the second radar module, without any correction for phase deviation, wherein the horizontal axis indicates a chirp or ramp number, and the vertical axis indicates a phase in radians;

[0106] FIG. 16a is a phase progression for the first radar module, with a correction for phase deviation, wherein the horizontal axis indicates a chirp or ramp number, and the vertical axis indicates a phase in radians;

[0107] FIG. 16b is a phase progression for the second radar module, with a correction for phase deviation, wherein the horizontal axis indicates a chirp or ramp number, and the vertical axis indicates a phase in radians;

[0108] FIG. 17a is a 2D-(FFT) spectrum for the crossed path of the first radar module, with corrections for drift and jitter as well as time and frequency offset, wherein the horizontal axis indicates a velocity in meters per second, and the vertical axis indicates a magnitude in decibels (dB);

[0109] FIG. 17b is a 2D-(FFT) spectrum for the crossed path of the second radar module, with corrections for drift and jitter as well as time and frequency offset, wherein the horizontal axis indicates a velocity in meters per second, and the vertical axis indicates a magnitude in decibels (dB);

[0110] FIG. 18a is a 2D-(FFT) spectrum for the crossed path of the first radar module, with corrections for drift and jitter as well as time and frequency offset as well as phase variations, wherein the horizontal axis indicates a velocity in meters per second, and the vertical axis indicates a magnitude in decibels (dB);

[0111] FIG. 18b is a 2D-(FFT) spectrum for the crossed path of the second radar module, with corrections for drift and jitter as well as time and frequency offset as well as phase variations, wherein the horizontal axis indicates a velocity in meters per second, and the vertical axis indicates a magnitude in decibels (dB);

[0112] FIG. 19 is a superposition spectrum after an addition of spectra according to FIGS. 18a, 18b for the crossed path, wherein the horizontal axis indicates a velocity in meters per second, and the vertical axis indicates a magnitude in decibels (dB); and

[0113] FIG. 20a is a spectrum of a primary response for the first radar module, wherein the horizontal axis indicates a velocity in meters per second, and the vertical axis indicates a magnitude in decibels (dB);

[0114] FIG. 20b is a spectrum of a primary response for the second radar module, wherein the horizontal axis indicates a velocity in meters per second, and the vertical axis indicates a magnitude in decibels (dB).

[0115] As evident from FIG. 1, two transmitter-receiver units NKSE1, NKSE2 communicate with each other via a radio interface. A first or a second signal sigTX1, sigTX2 are here transmitted. The transmitter-receiver units NKSE1, NKSE2 each have a signal source 1, a unit for clock adjustment or comparison signal modification 2, and a transmission comparison unit (SigComp1, SigComp2). The (non-coherent) transmitter-receiver units are preferably comprised of radar modules. In the following, NKSE1 can thus be regarded as a first radar module, and NKSE2 as a second radar module below.

[0116] FIG. 2 additionally shows a respective unit for phase modification 4. Data is exchanged between the two units for phase modification 4.

[0117] In the following, the exact mathematical derivation of how method II functions will be performed. In a first non-coherent transmitter-receiver unit (NKSE1), a first signal (sigTX1) is generated and transmitted, in particular emitted, over a path (SP). In an additional, in particular second non-coherent transmitter-receiver unit (NKSE2), a second signal (sigTX2) is generated and transmitted, in particular emitted, over the path (SP). The signals are here ideally emitted simultaneously, or at the very least synchronized with each other in such a way that the two signal forms preferably overlap at least half the transmission time. The signal sources can be completely or partially independent.

[0118] As usually the case in communications engineering, the used transmitted signals (sigTX1, sigTX2) can be represented as a separation into an equivalent baseband signal (bbTX1) and a carrier signal.

[0119] Since the system according to the invention is preferably to be used for distance measurement or imaging, signals with so-called good correlation properties are preferably used as the baseband signals. For example, signals with good correlation properties include broadband pulses, noise signals, pseudo-random pulse sequences (PN code) such as M-sequences, Gold codes or Barker codes, Kasami sequences, Huffman sequences, chirps, linearly frequency modulated signals (FMCW), chirp or FMCW sequences, etc. Signal forms like these have been known in radar engineering and communications engineering (in particular in the CDMA area) for a long time and in a wide variety.

[0120] The transmitted signal (sigTX1) of the transmitter-receiver unit (NKSE1) can be represented as follows:

sigTX1(t)=Re{bbTX1(t−T.sub.01).Math.e.sup.j(ω.sup.c1.sup.(t-T.sup.01.sup.)+ϕTX1(t-T.sup.01.sup.))}

[0121] The time offset T01 defines the transmission time of signal sigTX1;

[0122] The phase term ϕTX1(t)=φTX1+ξTX1(t) comprises a constant phase offset and the phase noise of the carrier signal.

[0123] The angular frequency ω.sub.c1 characterizes the frequency of the carrier signal of sigTX1.

[0124] The transmitted signal (sigTX2) of the transmitter-receiver unit (NKSE2) can be formed in the same way. The following applies:

sigTX2(t)=Re{bbTX2(t−T.sub.02).Math.e.sup.j(ω.sup.c2.sup.(t-T.sup.02.sup.)+ϕTX2(t-T.sup.02.sup.))}

[0125] The transmitted signals (sigTX1 and sigTX2) arrive at the respective other transmitter-receiver station, either directly or reflected by objects, and are there received and further processed as received signals sigRX12 and sigRX21.

[0126] The received signal that is received at the second non-coherent transmitter-receiver unit (NKSE2) corresponds to the transmitted signal (sigTX1), but the latter has been altered in amplitude and delayed by transit time τ.sub.21. In order to simplify the mathematical representation and without limiting the general disclosure, all signals are to be represented below as complex valued signals. Therefore, the following applies:

sigRX21(t)=ARX21.Math.bbTX1(t−T.sub.01−τ.sub.21).Math.e.sup.j(ω.sup.c1.sup.(t-T.sup.01.sup.−τ.sup.21.sup.)+ϕTX1(t-T.sup.01.sup.−τ.sup.21.sup.))

[0127] If the transmitted signal (sigTX1) is transmitted on several (a number of l) transmission paths of varying length to the second transmitter-receiver unit (NKSE2), the received signal can be represented as a linear superposition of amplitude-weighted and time-delayed signals as follows:

[00004]$\mathrm{sigRX}21\left(t\right)=\underset{i=1}{\overset{I}{.Math.}}\mathrm{sigRX}21i\left(t\right)$$\mathrm{with}$$\mathrm{sigRX}21i\left(t\right)=\mathrm{ARX}21i.Math.\mathrm{bbTX}1\left(t-T_{01}-{\tau }_{21i}\right).Math.e^{j\left({\omega }_{c2}\left(t-T_{01}-{\tau }_{21i}\right)+\varphi \mathrm{TX}1\left(t-T_{01}-{\tau }_{21i}\right)\right)}$

[0128] Accordingly, the following applies to the signal transmitted from the second transmitter-receiver unit (NKSE2) to the first transmitter-receiver unit (NKSE1):

[00005]$\mathrm{sigRX}12\left(t\right)=\mathrm{ARX}21.Math.\mathrm{bbTX}2\left(t-T_{02}-{\tau }_{12}\right).Math.e^{j\left({\omega }_{c2}\left(t-T_{02}-{\tau }_{12}\right)+\varphi \mathrm{TX}2\left(t-T_{02}-{\tau }_{12}\right)\right)}$$\mathrm{or}$$\mathrm{sigRX}12\left(t\right)=\underset{i=1}{\overset{I}{.Math.}}\mathrm{sigRX}12i\left(t\right)$$\mathrm{with}$$\mathrm{sigRX}12i\left(t\right)=\mathrm{ARX}12i.Math.\mathrm{bbTX}2\left(t-T_{02}-{\tau }_{12i}\right).Math.e^{j\left({\omega }_{c2}\left(t-T_{02}-{\tau }_{12i}\right)+\varphi \mathrm{TX}2\left(t-T_{02}-{\tau }_{12i}\right)\right)}$

[0129] The transmitter-receiver units (NKSE1, NKSE2) were designed in such a way as to comprise signal comparison units SigComp1, SigComp in which the respective received signal of a transmitter-receiver unit is offset with its transmitted signal—i.e., signal sigRX12 with signal sigTX1 in NKSE1 and signal sigRX21 with signal sigX2 in NKSE2. The signal comparison units SigComp1, SigComp2 are designed as mixers Mix in the exemplary embodiment. That is to say, signal sigRX12 is here mixed with signal sigTX1 in NKSE1, and signal sigRX21 with signal sigTX2 in NKSE2. As generally known as such, a mixing process can be expressed in terms of system theory as multiplication, or a downmixing given two complex sinusoidal signals as the multiplication of one of the signals by the conjugated complex (*=conjugation sign) of the other signal. Therefore, the following applies:

[00006]$\begin{array}{cc}\mathrm{sigC}12=& \mathrm{sigRX}{12}^{*}.Math.\mathrm{sigTX}1\\ =& \mathrm{ARX}12.Math.\mathrm{bbTX}{2}^{*}\left(t-T_{02}-{\tau }_{12}\right).Math.\\ & e^{-j\left({\omega }_{c2}\left(t-T_{02}-{\tau }_{12}\right)+\varphi \mathrm{TX}2\left(t-T_{02}-{\tau }_{12}\right)\right)}.Math.\\ & \mathrm{bbTX}1\left(t-T_{01}\right).Math.\\ & e^{j\left({\omega }_{c1}\left(t-T_{01}\right)+\varphi \mathrm{TX}1\left(t-T_{01}\right)\right)}\\ =& \mathrm{ARX}12.Math.\mathrm{bbTX}{2}^{*}\left(t-T_{02}-{\tau }_{12}\right).Math.\\ & \mathrm{bbTX}1\left(t-T_{01}\right).Math.\\ & e^{j\left({\omega }_{C1}\left(t-T_{01}\right)+\varphi \mathrm{TX}1\left(t-T_{01}\right)-{\omega }_{c2}\left(t-T_{02}-{\tau }_{12}\right)-\varphi \mathrm{TX}2\left(t-T_{02}-{\tau }_{12}\right)\right)}\end{array}$

[0130] In another advantageous way of forming a comparison signal, NKSE1 does not mix signal sigRX12 with signal sigTX1, but instead only with its carrier. That is to say:

[00007]$\begin{array}{cc}\mathrm{siC}12=& \mathrm{sigRX}{12}^{*}.Math.e^{j\left({\omega }_{c1}\left(t-T_{01}\right)+\varphi \mathrm{TX}1\left(t-T_{01}\right)\right)}\\ =& \mathrm{ARX}12.Math.\mathrm{bbTX}{2}^{*}\left(t-T_{02}-{\tau }_{12}\right).Math.\\ & e^{j\left({\omega }_{c1}\left(t-T_{01}\right)+\varphi \mathrm{TX}1\left(t-T_{01}\right)-{\omega }_{c2}\left(t-T_{02}-{\tau }_{12}\right)-\varphi \mathrm{TX}2\left(t-T_{02}-{\tau }_{12}\right)\right)}\end{array}$

[0131] The following applies accordingly for the signals in the NKSE2:

[00008]$\begin{array}{cc}\mathrm{sigC}21=& \mathrm{sigRX}{21}^{*}.Math.\mathrm{sigTX}2\\ =& \mathrm{ARX}21.Math.\mathrm{bbTX}{1}^{*}\left(1-T_{01}-{\tau }_{21}\right).Math.\\ & e^{-j\left({\omega }_{c1}\left(t-T_{01}-{\tau }_{21}\right)+\varphi \mathrm{TX}1\left(t-T_{01}-{\tau }_{21}\right)\right)}.Math.\\ & \mathrm{bbTX}2\left(t-T_{02}\right).Math.\\ & e^{j\left({\omega }_{c2}\left(t-T_{02}\right)+\varphi \mathrm{TX}2\left(t-T_{02}\right)\right)}\\ =& \mathrm{ARX}21.Math.\mathrm{bbTX}{1}^{*}\left(t-T_{01}-{\tau }_{21}\right).Math.\\ & \mathrm{bbTX}2\left(t-T_{02}\right).Math.\\ & e^{j\left({\omega }_{c2}\left(t-T_{02}\right)+\varphi \mathrm{TX}2\left(t-T_{02}\right)-{\omega }_{c1}\left(t-T_{01}-{\tau }_{21}\right)-\varphi \mathrm{TX}1\left(t-T_{01}-{\tau }_{21}\right)\right)}\end{array}$

[0132] Or in the alternative embodiment:

[00009]$\begin{array}{cc}\mathrm{sigC}21=& \mathrm{sigRX}{21}^{*}.Math.e^{j\left({\omega }_{c2}\left(t-T_{02}\right)+\varphi \mathrm{TX}2\left(t-T_{02}\right)\right)}\\ =& \mathrm{ARX}21.Math.\mathrm{bbTX}{1}^{*}\left(t-T_{01}-{\tau }_{21}\right).Math.\\ & e^{j\left({\omega }_{c2}\left(t-T_{02}\right)+\varphi \mathrm{TX}2\left(t-T_{02}\right)-{\omega }_{c1}\left(t-T_{01}-{\tau }_{21}\right)-\varphi \mathrm{TX}1\left(t-T_{01}-{\tau }_{21}\right)\right)}\end{array}$

[0133] It is now assumed that means are provided in NKSE for ensuring that the following conditions are satisfied:

T.sub.01=T.sub.02=T.sub.0 und ω.sub.c2=ω.sub.c1=ω.sub.c

[0134] How these means can preferably be configured was already described above, or has yet to be described further below in an exemplary embodiment. Under these boundary conditions:

[00010]$\begin{array}{cc}\mathrm{sigC}12=& \mathrm{ARX}12.Math.\mathrm{bbTX}{2}^{*}\left(t-T_0-{\tau }_{12}\right).Math.\\ & \mathrm{bbTX}1\left(t-T_0\right).Math.\\ & e^{j\left({\omega }_c\left(t-T_0\right)+\varphi \mathrm{TX}1\left(t-T_0\right)-{\omega }_c\left(t-T_0-{\tau }_{12}\right)-\varphi \mathrm{TX}2\left(t-T_0-{\tau }_{12}\right)\right)}\\ =& \mathrm{ARX}12.Math.\mathrm{bbTX}{2}^{*}\left(t-T_0-{\tau }_{12}\right).Math.\\ & \mathrm{bbTX}1\left(t-T_0\right).Math.\\ & e^{j\left({\omega }_c{\tau }_{12}+\varphi \mathrm{TX}1\left(t-T_0\right)-\varphi \mathrm{TX}2\left(t-T_0-{\tau }_{12}\right)\right)}\end{array}$$\begin{array}{cc}\mathrm{sigC}21=& \mathrm{ARX}21.Math.\mathrm{bbTX}{1}^{*}\left(t-T_0-{\tau }_{21}\right).Math.\\ & \mathrm{bbTX}2\left(t-T_0\right).Math.\\ & e^{j\left({\omega }_c\left(t-T_0\right)+\varphi \mathrm{TX}2\left(t-T_0\right)-{\omega }_c\left(t-T_0-{\tau }_{21}\right)-\varphi \mathrm{TX}1\left(t-T_0-{\tau }_{21}\right)\right)}\\ =& \mathrm{ARX}12.Math.\mathrm{bbTX}{1}^{*}\left(t-T_0-{\tau }_{21}\right).Math.\\ & \mathrm{bbTX}2\left(t-T_0\right).Math.\\ & e^{j\left({\omega }_c{\tau }_{21}+\varphi \mathrm{TX}2\left(t-T_0\right)-\varphi \mathrm{TX}1\left(t-T_0-{\tau }_{21}\right)\right)}\end{array}$

[0135] Assuming a reciprocal transmission channel, the following also applies:

τ.sub.21=τ.sub.12=τ

[0136] In the next step, data communication is used to ensure that both comparison signals are transmitted to a shared evaluation unit, and that both are there present for evaluation. The shared evaluation unit can be NKSE1, NKSE2 or another evaluation unit.

[0137] In another processing step, the phases of the two comparison signals are now added. If only the carder phases with the phase noise portion are here considered, since unknown phase contributions are present only in this portion, and the two carrier phase terms are added, then:

[00011]$\begin{array}{cc}\mathrm{\Delta \varphi }=& \left({\omega }_c\tau +\varphi \mathrm{TX}1\left(t-T_0\right)-\varphi \mathrm{TX}2\left(t-T_0-\tau \right)\right)+\\ & \left({\omega }_c{\tau }_{21}+\varphi \mathrm{TX}2\left(t-T_0\right)-\varphi \mathrm{TX}1\left(t-T_0-{\tau }_{21}\right)\right)\\ =& 2{\omega }_c\tau +\varphi \mathrm{TX}1\left(t-T_0\right)-\varphi \mathrm{TX}1\left(t-T_0-\tau \right)+\\ & \varphi \mathrm{TX}2\left(t-T_0\right)-\varphi \mathrm{TX}2\left(t-T_0-\tau \right)\end{array}$

[0138] Taking into account that the transit time τ is as a rule very small due to the high propagation velocity of electromagnetic waves, and that the relevant phase noise portions typically drop off sharply in an oscillator based on the known correlations of oscillator phase noises as the distance from the carrier increases, and ϕTX1 or ϕTX2 resultantly exhibit a pronounced low-pass behavior, specifically a low-pass behavior with a cut-off frequency that is usually significantly less than 1/τ, it follows that:

δϕ1(t)=ϕTX1(t−T.sub.0)−ϕTX1(t−T.sub.0−τ) with δϕ1(t)<<ϕTX1(t)

δϕ2=ϕTX2(t−T.sub.0)−ϕTX2(t−T.sub.0−τ) with δϕ2(t)<<ϕTX1(t)

[0139] The proposed processing, in which the phase of the respective other comparison signal is added up for one of the comparison signals, thus results in a very significant reduction in the disturbances caused by phase noises. This reduction in phase noises leads to a better detectability of targets, a larger measuring range and an improved measuring accuracy.

[0140] Depending on the selected mixer topology, e.g., on whether an identical position or inverted position mixer is used, it is possible for the phase terms represented above to have different signs. Depending on the sign, the preferred linkage for the phase terms is not invariably an addition, but potentially also a subtraction. The key factor is that the linkage lead to a reduction in the phase noise terms and transit time dependent phase term, i.e., that an expression comprising the term ω.sub.cτ be retained. It is further generally known that, in a case where the phase values are represented by complex numbers, the complex numbers are multiplied and divided with each other, or multiplied with the conjugated complex of the respective other number, so as to form the sum or difference of phases.

[0141] One possible preferred variant for reducing the phase noise portions will be described below. In many cases, it is favorable that identical baseband signals be generated in the first and second non-coherent transmitter-receiver unit (NKSE1, NKSE1), i.e., that the following applies:

bbTX1=bbTX2=bbTX.

[0142] In an at least approximatively reciprocal radio channel, it must further be assumed that the following applies:

ARX12=ARX21=ARX.

[0143] Under these boundary conditions, the result is:

sigC12=ARX.Math.bbTX*(t−T.sub.0−τ.sub.12).Math.bbTX(t−T.sub.0).Math.e.sup.j(ω.sup.c.sup.τ+ϕTX1(t-T.sup.0.sup.)-ϕTX2(t-T.sup.0.sup.−τ))

sigC21=ARX.Math.bbTX*(t−T.sub.0−τ.sub.21).Math.bbTX(t−T.sub.0).Math.e.sup.j(ω.sup.c.sup.τ+ϕTX2(t-T.sup.0.sup.)-ϕTX1(t-T.sup.0.sup.−τ))

[0144] As readily discernible, the two signals are identical except for their phase terms.

[0145] However, despite a reciprocal radio channel, easily distinguishable amplitudes for signals sigC12 and sigC21 can arise due to varying properties of the electronic components, e.g., mixers or amplifiers, etc. If the amplitudes of signals sigC12 and sigC21 differ, the signals must first be standardized to the same amplitude in the preferred variant described here.

[0146] Additional systematic phase offsets can also arise during the process for forming signals sigC12 and sigC21. If these phase offsets of signals sigC12 and sigC21 differ, these phase offsets must first be compensated in the preferred variant described here.

[0147] Signals sigC12 and sigC21 can be viewed as a complex pointer for a specific time t. A complex addition of pointers cancels out the vector components of the phase terms with differing sign in the same way as described above for the addition of phase terms. As one possible preferred variant for reducing the phase noise portions, it is thus proposed that complex signals sigC12 and sigC21 be added, i.e., that a signal be formed as follows:

sigCC=sigC12+sigC21

[0148] Signal sigCC then has a significantly lower phase noise than signal sigC12 or sigC21, and signal sigCC is then further used for distance measurement, angle measurement or imaging purposes. Prior to the addition of signals, however, it is important to compensate for the systematic deviations of amplitudes and phases described above, which lead to varying carrier frequencies and transmission times.

[0149] Of course, it is not necessary to add up all values for sigC12 and sigC21, and not even necessarily the signals sigC12 and sigC21 themselves. However, at least one complex value comprised of a first of the two comparison signals or of a signal derived from this first comparison signal is to be used to adjust at least one complex value of the second of the two comparison signals or a value of a signal derived from this second comparison signal, so as to thereby form at least one value of a signal (sigCC), wherein the adjustment takes place in such a way that a mathematical operation forms the vectorial sum or the difference of at least two complex values derived from sigC12 and sigC21, or forms the sum or the difference of the phases of these complex values.

[0150] Let it be noted here that the proposed mixing processes only represent one possible embodiment, and that the phase noise portions could also be compensated using alternative methods. For example, all high frequency signals could already be digitized prior to mixing, i.e., scanned with an analog-to-digital converter, and all other operations could take place computationally or digitally, for example in a processor FPGA (field programmable gate array).

[0151] The transmitted signals sigTX1 and sigTX2 can basically be FMCW modulated. The spectra of the comparison signals are here preferably standardized to the highest value (prior to the mathematical operation).

[0152] A special embodiment of method II with FMCW signals and several sequential N ramps will be described below. The NKSE's here transmit several N signals with a linearly rising or falling frequency, referred to below as frequency ramps. The comparison signals are then generated out of the received signals in the NKSE, and then temporarily stored for further processing. Rising and falling ramps are used as an example, since this makes it possible to determine the relative velocity with the correct sign.

[0153] Individual spectrograms of beat signals sigC12 and sigC21 are first generated for each reception channel for each ramp. These spectrograms are juxtaposed for all N sequential ramps in an amplitude display without phase information. This is depicted on FIG. 4 for the rising ramps, in which two maxima appear, since no IQ mixing was performed, with a real-valued scanning signal being present instead. During use in primary radars, the at least one reflector in the detection area must be identified for this step, and depicted as described above.

[0154] The frequency band in which the beat signal is to be expected (ensured via rough synchronization) is now generously cropped. The respective spectrogram of the first N/2 ramps is then correlated with that of the second N/2 ramps along the frequency axis (step 1). The maximum found in the process reflects the relative time drift of the two NKSE's (a linear function can here be assumed). For example, when receiving the signals via one or several reflections, the targets can also be identified via the opposing drift on both sides.

[0155] In particular in the case of primary radars, the frequency offset can alternatively also be determined via a shared bus system, by having the systems exchange their measurement signals or further synchronization signals via the cable of a bus system. The bus system is here in particular a CAN, FlexRay, Most, gigabyte ethernet system, USB, Firewire or TTP system.

[0156] All ramps in the spectrogram are then corrected by this drift, for example by multiplying with a complex correction signal with opposing frequency offset in the unit for clock adjustment or comparison signal modification 2. The spectrograms of the various ramps obtained in this way are (incoherently) added, and the maximum corresponding to the time delay (offset error) is searched for in the superposition result. In the case of primary radar, the peaks can be selected using the identification in the preceding step of peaks that belong together.

[0157] Alternatively, the time offset can also be determined by way of a shared bus system, in particular by transmitting either the measurement data or suitable correlation sequences.

[0158] The parameters for relative time delay and relative time drift (=current frequency offset) determined in this way are averaged over the entire sequence of N ramps. This result contains a large part of the clock deviation. In addition, at what location in the spectrogram the respective energy of the incoming signal is to be expected is now known for each ramp and each station.

[0159] The originally recorded local mixed signals sigC12 and sigC21 are now first displaced by integral values Tint (the time delay between the two stations represented as ΔT=|T01−T02|=Tint+Tfrac), so as to obtain a uniform time basis. The phase noise is more strongly correlated owing to the shared, precise time basis. The remaining, slight time error Tfrac can now be compensated for, e.g., by using a fractional delay filter. The signals displaced in this way are now corrected by the deviating ramp slope, which arises due to the frequency offset Δω=ω1−ω2 of the two local oscillators, by folding or spectrally multiplying with a standardized, complex correction signal, which images the frequency progression in the opposite direction.

[0160] After an FFT of the beat signal to the channel impulse response, a search is performed for a peak in these further refined mixed signals. In the case of secondary radar, the strongest peak or alternatively the first peak is preferably taken, while a peak contained equally on both sides must be selected for primary radar. In this way, a maximum arises for each ramp at both stations at the estimated distance with the accompanying phase position. In principle, these values coincide with each other for the measurement on the outward and return path given a reciprocal channel. The remaining deviations can be attributed to remaining frequency and phase differences between both signal sources 1 of the NKSE, for example of the oscillators, the underlying cause for which is phase noise. The exact frequency difference can now be absolutely determined, and thus corrected (the phase difference can be determined up to a 180° ambiguity (360° for IQ mixers)). This ambiguity is eliminated by limiting the phase progression to +/−90° from ramp to ramp, which is also referred to as unwrapping. After this precise correction of the remaining phase error, there exists hardly any difference between the synthetic mixed signals of both stations.

[0161] After this preliminary processing, the characteristic, systematic errors of the radar system were completely corrected, as a result of which the phase shift of the two beat signals now only deviates by a small amount. At this juncture, a precise synchronization of the time and frequency basis has been achieved on the one hand, and the phase noise can be regarded as an additive contribution and eliminated through linear combination on the other. For example, this is done via the 2D Fourier transformation of all N-ramps on both NKSE's, whereupon the amplitude-standardized beat signals are finally added together. With the inclusion of the system parameters (sampling rate, ramp slope, carrier frequency, . . . ), the maximum of the result for this linear combination represents the estimated value for distance and velocity.

[0162] FIG. 5 schematically depicts a configuration of a plurality of radar modules RM 1, RM 2, . . . RM N, which each have a device for frequency generation (HF-generator) 11, a device 12 for frequency conversion as well as an (optional) device 13 for clock generation and an (optional) device 14 for AD conversion.

[0163] FIG. 6 shows examples for how the radar modules depicted schematically on FIG. 1 can be arranged on a motor vehicle (automobile). On FIG. 6a, four radar modules are arranged on the motor vehicle (front left, front right, rear left and rear right). As a result, the surroundings can be especially advantageously captured (with four sensors in the present case). Three radar modules are arranged in the front (none in the rear in this case) on FIG. 6b, specifically front left, front center and front right. As a result, the surroundings can be especially advantageously captured in the traveling direction (with three sensors in the present case). On FIG. 6c, the surroundings can be captured especially comprehensively, in the present case with eight radar modules (front left, front center, front right, rear left, rear center, rear right and a respective radar module on the two sides).

[0164] An embodiment for a holographic evaluation will be described below, drawing reference to FIG. 7. For the present application, the holographic calculation can be performed as follows.

[0165] A space to be calculated can be represented by individual points in space. The configuration of the transmitter and receiver antennas in the space to be calculated or relative to the space to be calculated is (usually) known. A synthetic signal (amplitude, phase, frequency) that arises for a propagation path (from an assumed transmitter antenna a to an assumed receiver antenna b) can be calculated for each point in space. This signal can then be correlated with real measurement data for this transmission path, and the complex correlation result can be recorded for this point in space. The process can be repeated for all k propagation paths for a point in space, and respectively (complexly) added to the result of the preceding calculation. An amount value for this sum then represents an allocation probability for the point in space. This process can be repeated over all n, m points in space, and the radar image can thus be generated.

[0166] In particular when using FMCW signals, the holographic process can be performed as follows:

[0167] A beat spectrum can first be calculated for each channel. A signal hypothesis relating to the phase position for each transmitted signal-received signal combination can be set up for each point in space in such a way as to correspond with an expected phase shift on this propagation path (from an assumed transmitter antenna a to an assumed receiver antenna b). An expected phase location can be correlated with a staring frequency f.sub.u and a signal path length d of an FMCW system according to φ.sub.H=exp(j2πdf.sub.u/c). This signal hypothesis can then be multiplied (on a complexly conjugated manner) with real measurement data (a precise amplitude and phase value can be obtained from the beat spectrum through interpolation) of this transmission path, and the (complex) intermediate result for this point in space can be recorded. This procedure can be repeated for all k propagation paths for the point in space, and respectively (complexly) added to the result of the preceding calculation. An amount value for this sum then represents the allocation probability for the point in space. This process can be repeated over all n, m points in space (in the two spatial dimensions), and a radar image can thus be generated.

[0168] The holographic calculation can especially preferably also be used for calibration purposes. The correction vector that represents an ideally focused target can here be determined, in particular iteratively. When calibrating antenna arrays, use is (ideally) made of a point target in the far field that is located very far away from the configuration in distributed radar modules according to the above approximation formula. As a result, the required high signal-to-noise ratio is not reached. In addition, it is very difficult to measure the exact position of the calibration object in this case, and the configuration requires a lot of space. Selecting a suitable environment without additional reflecting objects and with little clutter is also comparatively complicated. A largely ideal point target at a known position (e.g., a metal cylinder or metal ball) in the near field is preferably used for calibration purposes (instead of an object in the far field). After the exact position of the radar configuration and the target has been determined, in particular the amplitudes can be adjusted and the phase differences (according to the above holographic approach) can be corrected.

[0169] The holographic processes can also be performed at the velocity and acceleration level. As a consequence, the velocity and acceleration vector can be (holographically) determined for each image point. For example, DE 102009030076 describes suitable velocity and acceleration holography methods.

[0170] SAR imaging according to the invention will be illustrated below, drawing reference to FIG. 8. Radar measurements can be performed and recorded in SAR imaging along a specific movement path. These can then be mathematically combined as though they were combined by an antenna array with elements at each location where a measurement was recorded. In prior art, radar was used for this purpose, and the synthetic aperture was generated over the entire movement length. By using two radars whose signals are coherent relative to each other, the radar data of both sensors and the additional paths between the radars can be used, and a traversing path required for illumination becomes smaller. For this reason, the radar systems whose signals are corrected via postprocessing as though they were generated by a coherent radar are advantageously mounted in a large aperture. The radar signals of both radar modules (a direct path and a crossed path or indirect path) can then be used together in an SAR algorithm.

[0171] FIG. 9 presents a schematic sketch of an interferometric SAR (SAR-synthetic aperture radar). FIG. 10 shows a schematic vehicle with an exemplary sensor layout (layout of modules).

[0172] Measuring a height of objects poses a significant obstacle in particular in the area of autonomous driving, since currently used environment sensors (usually) only make it possible to estimate the distance, velocity and azimuth angle of a target in the vehicle environment. Known from M. A. Richards, “A Beginner's Guide to Interferometric SAR Concepts and Signal Processing”, IEEE Aerospace and Electronic Systems Magazine, Vol. 22, No. 9, pages 5-29, 2007, is that a system having several spatially offset receiver antennas can be used for measuring height. In this case, the antennas of the system are downwardly inclined, wherein a directional characteristic that radiates toward the front as well as downwardly (situationally) can also be advantageous. The achievable accuracy is here significantly limited by a difference in height between the receiver antennas. A comparatively high accuracy is advantageous in particular for differentiating between objects, such as curbs, fences, reflector posts, traffic signs, manhole covers, or trash (for example, beverage containers or small packages here do not represent any significant objects on the road), which are present on the road, but also for detecting and differentiating between people or animals in traffic. In addition, height detection is (critically) significant for automatic parking processes. According to M. A. Richards, “A Beginner's Guide to Interferometric SAR Concepts and Signal Processing”, IEEE Aerospace and Electronic Systems Magazine, Vol. 22, No. 9, pages 5-29, 2007, the accuracy of height measurement is determined by approximation using

[00012]$.Math.\delta h.Math.\approx \frac{\cos \left(\psi \right)}{\sin \left(\psi +\beta \right)}\frac{R}{B}.Math.\delta \left(\Delta R\right).Math.$

wherein the two angles ψ and β, as well as the distances R, B and ΔR, can be gleaned from FIG. 9. δ(ΔR) here represents the accuracy of measurement with respect to differential distance, for example which can be determined very precisely by means of a phase comparison. In the present invention, the baseline B can be significantly increased, since additional reception elements (modules) can be positioned as desired (or at least essentially as desired) on the vehicle. For example, by placing one radar module in a bumper and a second radar module on the roof of the vehicle, this makes it possible to raise the accuracy by a factor of 10 (compared with a single, compact radar module with several reception elements). Exemplary installation positions are illustrated on FIG. 10, specifically in a bumper 15, side mirrors 16 and/or in a roof (roof rail) 17.

[0173] Methods for reducing interference components, in particular phase noises, are explained based upon the diagrams according to FIG. 11a, 11b-20a, 20b. These methods are also to be described as a further development of method I or method II as (optionally) independent subject matters of the present invention. In this conjunction, the additional features in claim 1 (as well as the other independent claims) are here possibly only optional.

[0174] To the extent modules are discussed below, these can in particular be the (non-coherent) transmitter-receiver units according to method I or method II. The modules (transmitter-receiver units) thus need not (necessarily) be arranged on a moving object (e.g., on a motor vehicle according to FIG. 8) or be configured for such a layout. However, this is possible.

[0175] FIG. 11a shows a spectrum of a first radar module. Specifically prescribed is a progression of several (here for example 128) ramps, if the latter are depicted one next to each other for a transmission channel. As evident, a crossed path is influenced on the one hand by a frequency offset Δf (here selected as 350 kHz), but also by an unknown drift T.sub.d and jitter T.sub.j, in such a way that a beat frequency changes over a signal duration (i.e., for example the sequence of 128 ramps). In addition, the unknown time offset between the modules T.sub.off,0 can possibly also have an influence. This offset is produced by the various starting points for signal generation in the radar module. This offset might not be completely known even given a pre-synchronization via the air interface or via a synchronization line. FIG. 11b shows a corresponding spectrum for a second radar module.

[0176] Evaluating (only) one primary radar response yields an illustration according to FIG. 12a (for the first radar module) and 12b (for the second radar module). These depictions stem in particular from a 2D-FFT without pre-processing.

[0177] In evidence are standing targets at v=0 m/s along with a moving target with a constant velocity of 0.2 m/s at a specific distance. A crossed path response cannot be evaluated in this way (at least not especially accurately), but can be corrected based upon the following statements (algorithms). An azimuth angle can further be drawn upon for a (complete) evaluation.

[0178] Crossed path signals of the (two) radar modules after a mixing process, being influenced by (all) system variables for a signal path, are described accurately enough for initial observations as (wherein a multipath propagation or several targets will initially not be modelled for the sake of clarity)

s.sub.an1(t)=A.sub.ae.sup.j2π(f.sup.0.sup.((−1).sup.a-1.sup.(τ+τ.sup.l.sup.)-T.sup.off,l.sup.)+δϕ.sup.0,l.sup.)e.sup.j(ϕ.sup.p,al.sup.(t)+(−1).sup.a-1.sup.ϕ.sup.an.sup.)e.sup.−j2πt(Δf+μ((−1).sup.a-1.sup.τ-T.sup.off,l.sup.)).  (1)

[0179] In principle, then, the mixed signal consists of an amplitude

A.SUB.a.,

[0180] Two phase terms

e.sup.j2π((f.sup.0.sup.((−1).sup.a-1.sup.(τ+τ.sup.l.sup.)-T.sup.off,l.sup.)+δϕ.sup.0,l.sup.)e.sup.j(ϕ.sup.p,al.sup.(t)+(−1).sup.a-1.sup.ϕ.sup.an.sup.),

And a frequency term

e.sup.−j2πt(Δf+μ((−1).sup.a-1.sup.τ-T.sup.off,l.sup.)).

[0181] In the above equation (1), the following applies: [0182] a: Number of station (e.g., 1 or 2) [0183] n: Number of channel (e.g., 1 to 8) [0184] l: Number of ramp (e.g., 1 to 128) [0185] A.sub.a: Signal amplitude [0186] f.sub.0: Carrier frequency (e.g., about 78 GHz) [0187] τ: Transit time, crossed path [0188] τ.sub.l: Transit time change owing to the movement of an object [0189] T.sub.off,l=T.sub.off,0+T.sub.j,l+l.Math.T.sub.D: Timing offset (e.g., owing to cable length, jitter and/or drift) [0190] δϕ.sub.0,l: Phase displacement through carrier frequency drift and/or unknown other components [0191] ϕ.sub.p,al(t): Phase noise (uncorrelated) [0192] ϕ.sub.an: Phase displacement between stations and individual channels [0193] Δf: Frequency offset (e.g., 350 kHz) [0194] μ: Sweep rate (e.g., 500 GHz/s)

[0195] This transit time change (given an at least approximately uniform movement over the measuring period) is detected via a phase change in the beat frequency, which can be assumed to be at least approximately constant within the measuring period.

[0196] The Fourier transformation of a ramp yields the beat signal

[00013]$\begin{array}{cc}{S}_{\mathrm{ant}}\left(f\right)=ℱ\left\{s_{\mathrm{ant}}\left(t\right)\right\}=A_a{e}^{j2\pi f_0\left({\left(-1\right)}^{\alpha -1}\left(\tau +{\tau }_l\right)-T_{\mathrm{off},l}+{\mathrm{\delta \varphi }}_{0,l}\right)}{e}^{{j\left(-1\right)}^{\alpha -1}{\varphi }_{\mathrm{an}}}.Math.ℱ\left\{e^{j{\varphi }_{p,\mathrm{at}}\left(t\right)}\right\}*\delta \left(g-\left(\Delta f+\mu \left({\left(-1\right)}^{\alpha -1}\tau -T_{\mathrm{off},l}\right)\right)\right).& \left(2\right)\end{array}$

[0197] Since this description is basically possible independently of a selected window function, the latter can be omitted. The phase noise in the mixed signal of a station depends on the current phase position, and thus is found to be ϕ.sub.p,1l(t)=ψ.sub.p,1l(t−T.sub.off,l)−ψ.sub.p,2l(t−τ) and ϕ.sub.p,1l(t)=ψ.sub.p,1l(t−τ−T.sub.off,l)−ψ.sub.p,2l(t). Because the time difference between 2 points in time is critical for the variance of the phase noise (Allan variance), the manifestation at both stations is about the same (ϕ.sub.p,1l(t)˜ϕ.sub.p,2l(t)). The phase noise of the local oscillators ψ.sub.p,1l and ψ.sub.p,2l is not correlated (as opposed to a primary radar), and can (drastically) impair the phase evaluation or signal coherence or velocity measurement.

[0198] An algorithm for evaluating the sampled signal (according to equation (1)) is indicated below:

[0199] In a first step, for example, the respective spectrum can be calculated via a Fourier transformation out of a Hibert transformation (which might be necessary if no I/Q data are available).

[0200] As evident from the spectra on FIG. 11a, 11b, a beat frequency for a crossed path rises (approximately) linearly over time, in addition to which jitters with a ±1 clock can arise. This may be due to the fact that each radar module uses different clock sources. This can be precluded in a modified version, which can be modelled as

T.sub.off,l=T.sub.off,0+T.sub.j,l+l.Math.T.sub.D,

wherein a drift TD along with the (from the standpoint of signal processing) randomly distributed jitter can be corrected in this calculation step. Shown as a random variable, the distribution

[00014]$p\left(T_{j,l}\right)=\{\begin{array}{cc}\alpha & \mathrm{for}{T}_{j,l}=-J_0\\ 1-2\alpha & \mathrm{for}{T}_{j,l}=0\\ \alpha & \mathrm{for}{T}_{j,l}=J_0\end{array},$

results for each ramp I, which with probability α leads to a jump by ±1 clock. The change in beat frequency is denoted with J.sub.0˜12.5 ns, and depends on the system clock (e.g., here f.sub.clk=80 MHz) and sweep rate p.

[0201] A region around the crossed path can be (generously) cut out as an interval, so that a resultant signal also contains information about (remotely) distant targets (with a larger beat frequency at the second radar module). In this case, equation (2) describes all relevant signal components.

[0202] As evident from equation (2), a beat frequency for a target is identical in all channels (an antenna position is only to vary slightly here).

[0203] Absolute values in equation (2) can be added for each channel in both radar modules, as follows:

[00015]$s_{\mathrm{al}}\left(f\right)=\underset{n}{.Math.}.Math.s_{\mathrm{anl}}\left(f\right).Math..$

[0204] What then results is a signal with a relatively high SNR (signal-to-noise ratio), which can be described by

S.sub.al(f)=B.sub.a|{e.sup.jϕ.sup.p,al.sup.(t)}*δ(f−(Δf+μ((−1).sup.a-1τ−T.sub.off,l)))|

wherein B.sub.a denotes the sum of amplitudes for the individual channels. In the system examined (with relatively slight phase noise), this effect produces hardly any change in the beat frequency during a ramp, as permitted by the approximation

S.sub.al(f)≈B.sub.aδ(f−(Δf+μ((−1).sup.a-1τ−T.sub.off,l)))  (3)

[0205] As discernible in equation (3), the frequency offset Δf and timing offset T.sub.off,l leads to a displacement of the beat frequency in the same direction, while the signal transit time produces a displacement with the opposite orientation.

[0206] A folding of the signals S.sub.1l(f) and S.sub.2l(f) of the two stations can be calculated so as to eliminate the signal transmit time τ. The resultant signal

H(f)=S.sub.1l(f)*S.sub.2l(f)=δ(f−2(Δf−μT.sub.off,l)))

contains a clear maximum given a frequency at 2(Δf−μT.sub.off,l). Since the folding encompasses all targets, this operation functions independently of the measured scenario. In the measurement examined, the SNR need only be sufficiently high overall. The maximum can now be determined for each individual ramp, which can be understood as the sequence

b.sub.l=2(Δf−μT.sub.off,l)=2(Δf−μ(T.sub.off,0+T.sub.j,l+l.Math.T.sub.D)).

[0207] In order to remove all shares that are constant over time, the differential sequence

[00016]$D_l=\frac{\left(b_l-b_{l+1}\right)}{2}=\frac{2\mu \left(T_{j,l}+l.Math.T_D-\left(T_{j,l+1}+\left(l+1\right).Math.T_D\right)\right)}{2}=\mu \left(T_{j,l}-T_{j,l+1}-T_D\right)$

can be calculated for l=1 . . . N−1, wherein N=128 in this case is an example for the total number of transmitted ramps.

[0208] D.sub.l can now be divided into three partial sequences, which are denoted with c.sub.1l, c.sub.2l, and c.sub.3l, and sequentially go with the jumps by 0, J.sub.0 and −J.sub.0. [0209] A jump height via jitter can be determined through expected value creation

Ĵ.sub.0=(E{c.sub.1l}+E{c.sub.2l}+E{c.sub.3l})/3.

[0210] A drift can now likewise be estimated through expected value creation

{circumflex over (T)}.sub.D=(E{c.sub.2l}−E{c.sub.3l})/2.

[0211] The two correction values J.sub.0 and T.sub.D can now be used to completely describe the sequence D.sub.1=μ(T.sub.j,l−T.sub.j,l+1−T.sub.D), and correct for jitter and drift as needed. FIGS. 13a, 13b show spectrograms for both modules (FIG. 13a for the first radar module; FIG. 13b for the second radar module) after correction for drift and jitter.

[0212] If necessary, a system without jitter (in the clock magnitude) can be realized when using a shared trigger per module. In this case, however, there may be a clearly smaller residual jitter portion, which is compensated in the other procedural steps.

[0213] Synchronization, e.g., via a CAN bus, can potentially prevent the drift of both modules. Clock signal synchronization and a shared trigger make it easy to perform an evaluation with the described method, since jitter no longer arises, and the drift is (negligibly) small.

[0214] A correction for transit time and frequency offset will be described below.

[0215] A transit time over a synchronization cable or a (preset) frequency offset (for separating primary and secondary responses) can lead to an (unknown) displacement in the beat frequency, which is identical at both stations. Proceeding from equation (3) after applying the corrections described above, the amplitude of the beat signal for both stations amounts to

S.sub.al(f)≈B.sub.aδ(f−(μ((−1).sup.a-1τ+Δf−μT.sub.off,0))).  (4)

[0216] This signal no longer varies from chirp to chirp, meaning over the ramp number l, which is why the summation over l

[00017]$S_a\left(f\right)=\underset{l}{.Math.}.Math.S_{\mathrm{al}}\left(f\right).Math.=C_a\delta \left(f-\left(\mu \left({\left(-1\right)}^{\alpha -1}\tau +\Delta f-\mu T_{\mathrm{off},0}\right)\right)\right).$

leads to strong maxima. The latter are identical in terms of distribution, but lie to the left and right of a “virtual center” f.sub.m, which derives from f.sub.m=Δf−T.sub.off,0. A renewed folding of the two channel responses

H(f)=S.sub.1(f)*S.sub.2(f)=δ(f−2(Δf−μT.sub.off,l)))

makes it possible to determine the maximum of H(f), which can be used as a very precise estimation {circumflex over (f)}.sub.m of the virtual center. A preceding correction for drift and jitter is advantageous at this juncture, since the entire SNR can thereby be (distinctly) increased.

[0217] The spectrum of one of the stations is now optionally mirrored at this virtual center, after which the amplitudes of the two spectra appear at the same positions, and, after shifting the focal point to a beat frequency of 0 Hz (absolute position of the maxima now corresponds to the actual target distances), can be represented by

[00018]$\begin{array}{cc}{S}_{\mathrm{anl}}\left(f\right)=A_a{e}^{j2\pi f_0\left({\left(-1\right)}^{\alpha -1}\left(\tau +{\tau }_1\right)-\mu T_{\mathrm{off},l}+{\mathrm{\delta \varphi }}_{0,l}\right)}{e}^{{j\left(-1\right)}^{\alpha -1}{\varphi }_{\mathrm{an}}}.Math.ℱ\left\{e^{j{\varphi }_{p,\mathrm{al}}\left(t\right)}\right\}*\delta \left(f-\mathrm{\mu \tau }\right).& \left(5\right)\end{array}$

[0218] FIGS. 14a, 14b show spectrograms of both modules after a correction for the time and frequency offset (FIG. 14a for the first module; FIG. 14b for the second module; both modules were spaced a slight distance apart, thereby making a certain level of crosstalk discernible as the “target” at 0 m.).

[0219] A phase variation correction will be explained below.

[0220] In principle, the phase progression of the two stations coincides for a target (here the one with the largest amplitude), since 128 sequential ramps are transmitted in the present example, as evident from FIGS. 15a, 15b (FIG. 15a for the first module, FIG. 15b for the second module). After correcting for all frequency terms, the spectrograms can be represented as

[00019]$\begin{array}{cc}{S}_{\mathrm{anl}}\left(f\right)=A_a{e}^{j2\pi f_0\left({\left(-1\right)}^{\alpha -1}\left(\tau +{\tau }_1\right)-\mu T_{\mathrm{off},l}+{\mathrm{\delta \varphi }}_{0,l}\right)}{e}^{{j\left(-1\right)}^{\alpha -1}{\varphi }_{\mathrm{an}}}.Math.e^{j{\gamma }_l}.Math.ℱ\left\{e^{j{\eta }_l\left(t\right)}\right\}*\delta \left(f-\mathrm{\mu \tau }\right),& \left(6\right)\end{array}$

which now have a quasi-constant beat frequency for a target at a defined distance. This step is to involve correcting the rough influence of phase noise (approximated as {e.sup.jϕ.sup.p,al.sup.(t)}≈e.sup.jγ.sup.l{e.sup.jη.sup.l.sup.(t)}, i.e., a large share of sweep to sweep and a smaller one during an (FMCW) ramp), as well as the influences of the timing offset, modelled as T.sub.off,l, on the phase position and unknown remaining terms δϕ.sub.0,l, of the two stations. The latter are contained in the equation as T.sub.off,l+δϕ.sub.0,l, and arise equally in both stations. In summation, then, a phase displacement Γ.sub.al=T.sub.off,l+δϕ.sub.0,l+γ.sub.1 arises from sweep to sweep.

[0221] It is basically possible to determine the phase at the largest occurring peak. On the one hand, however, this phase position can only be determined as an overlap given closely adjacent targets; on the other hand, this variant only incorporates the information about a target, which is generally disadvantageous in the case of multipath propagation or several reflection points to be detected.

[0222] For this reason, the argument for the complex standard scalar product

[00020]${\hat{\Gamma }}_l=\frac{1}{8}\underset{n}{.Math.}\arg \left\{.Math.S_{1\mathrm{nl}}^{*}\left(f\right),S_{2\mathrm{nl}}\left(f\right).Math.\right\}\text{/}2$

will at this juncture be evaluated for each (FMCW) sweep and each individual channel, after which the average value will be generated (e.g., with a prefactor ⅛ for 8 receiving channels). This does not influence the phase relationship between the channels. This estimated result can be used to correct the disturbing portion in equation (6), which leads to

[00021]$\begin{array}{cc}{S}_{\mathrm{anl}}\left(f\right)=A_a{e}^{j2\pi f_0\left({\left(-1\right)}^{\alpha -1}\left(\tau +{\tau }_1\right)\right)}{e}^{{j\left(-1\right)}^{\alpha -1} 0_{\mathrm{an}}}.Math.ℱ\left\{e^{j{\eta }_l\left(t\right)}\right\}*\delta \left(f-\mathrm{\mu \tau }\right),.& \left(7\right)\end{array}$

[0223] The progression of the phase given a fixed target for both stations and all channels is depicted on FIGS. 16a, 16b (for the first module on FIG. 16a, for the second module on FIG. 16b). The latter only deviates slightly from a constant function (remaining deviations can be corrected in the continued process as needed).

[0224] An ensuing complex conjugation of the signals from the second radar module leads to the spectra

[00022]$\begin{array}{cc}{S}_{\mathrm{anl}}\left(f\right)=A_a{e}^{j2\pi f_0\left(\tau +{\tau }_l\right)}{e}^{j{\varphi }_{\mathrm{an}}}.Math.ℱ\left\{e^{{j\left(-1\right)}^{\alpha -1}{\eta }_l\left(t\right)}\right\}*\delta \left(f-\mathrm{\mu \tau }\right),,& \left(8\right)\end{array}$

which essentially deviate from a typical primary response only in term

[00023]$ℱ\left\{e^{{j\left(-1\right)}^{\alpha -1}{\eta }_l\left(t\right)}\right\}.$

This portion represents the influence of the uncorrelated phase nose, which leads to a phase deviation within an (FMCW) ramp or an (FMCW) sweep.

[0225] In summation, a phase jump between adjacent ramps might be too large for phase tracking in numerous measurements. In particular, a maximum expected phase jump can limit the measurement range in terms of the doppler frequency, and hence in terms of the maximum velocity that can be detected. This problem can be reduced by an improved synchronization of the two stations. A deviation remaining after adjusting the clock rates might not (any longer) result in phase jumps arising over a uniqueness region between adjacent sweeps.

[0226] An adjustment and superposition of spectra will be described below.

[0227] Before superposing the two spectra, an adjustment can also be performed so as to correct a potential phase displacement of the strongest target given a non-reciprocal channel. In addition, the amplitudes of this target can be aligned for both spectra and/or a standardization to a shared or third variable can take place. After these two operations, the representation for a selected channel n can be as follows

S.sub.anl(f)=Ae.sup.j2πf.sup.0.sup.(τ+τ.sup.l.sup.)e.sup.jϕ.sup.n.Math.δ(f−μτ)*(1+j(−1).sup.a-1ε.sub.l(t))

wherein the phase noise remaining inside a chirp (sweep) can be approximated via Taylor development with termination after the linear term as

[00024]$ℱ\left\{e^{{j\left(-1\right)}^{\alpha -1}{\eta }_l\left(t\right)}\right\}\approx 1+{j\left(-1\right)}^{\alpha -1}{\mathrm{.Math.}}_l\left(t\right).$

Following an ensuing addition, the result is a (final) signal model

[00025]$S_{\mathrm{nl}}\left(f\right)=S_{1\mathrm{nl}}\left(f\right)+S_{2\mathrm{nl}}\left(f\right)=2{\mathrm{Ae}}^{j2\pi f_0\left(\tau +{\tau }_l\right)}{e}^{j{\varphi }_n}.Math.\delta \left(f-\mathrm{\mu \tau }\right).$

[0228] A corrected signal model will be described below.

[0229] The signal for the crossed path

S.sub.anl(f)=A.Math.e.sup.j2πf.sup.0.sup.τ.Math.e.sup.j2πf.sup.0.sup.τ.sup.l.Math.e.sup.jϕ.sup.an.Math.δ(f−μτ)  (8)

now (completely) resembles a primary response, and can thus preferably be used for coherent processing. A here represents the amplitude, e.sup.j2πf.sup.0.sup.τ the initial phase, e.sup.j2πf.sup.0.sup.τ.sup.l the doppler portion, e.sup.jϕ.sup.an the angular component and δ(f−μτ) the accompanying beat frequency. In the case of a multipath propagation or given several targets, the modelling

S.sub.anl(f)=τ.sub.kA.sub.k.Math.e.sup.j2πf.sup.0.sup.τ.sup.k.Math.e.sup.j2πf.sup.0.sup.τ.sup.kl.Math.e.sup.jϕ.sup.kan.Math.δ(f−μτ.sub.k)  (9)

results, wherein k corresponds to the number of the individual path.

[0230] The corrections described above makes it possible to generate an improved 2D range doppler plot or a simple doppler plot as on FIGS. 17a, 17b [sic] (show the plots without corrected phase variations; FIGS. 18a, 18b show plots with corrected phase variations; FIG. 17a, 18a for the first module, FIG. 18a, 18b for the second module), from which the velocity can be comparatively accurately derived. A remaining phase noise, which on the crossed path is significantly stronger than for a primary radar response, becomes noticeable in the form of randomly distributed, small peaks. These are distributed over all velocities and (quasi) identical in the first and second module (but phase displaced by 180 degrees). After adding both 2D spectra, a spectrum arises (see FIG. 19) that (except potentially for a comparatively small amplitude noise) corresponds to that of a primary radar (see FIG. 20a for the first module and FIG. 20b for the second module). This leads to significantly more measuring dynamics, whereupon weak targets (in the environment of strong targets) also become discernible. This method is here shown for an individual channel, since varying azimuth angles can result in an additional phase offset.

[0231] The method just described for reducing interference components, in particular phase noise, has a series of advantages (in particular in the automotive area). In particular, an improved SNR (signal-to-noise ratio) and an elevated reliability can be achieved. Furthermore, the distance and velocity vector of a target can be estimated with a comparatively high accuracy, since additional estimation values are available and can be used.

[0232] A (coherent) processing of a frequency displacement caused by a doppler effect can also take place smoothly via a crossed path. Phase information from a first radar module and a second radar module can thus be used to perform a precise measurement of the surroundings. As a result, SAR processing can be implemented, in particular in an automobile radar application, for generating a high-resolution image of the surroundings.

[0233] An application as a phase monopole with both stations can serve to be able to very precisely estimate an azimuth angle. This estimate can also be used in conjunction with existing angular information to further increase accuracy.

[0234] Feeding in an external, controlled clock made it possible to recognize that a rough synchronization (pre-synchronization) is basically possible, for example which would be conceivable via a CAN bus (of a motor vehicle). As a result, the computing outlay for the method can be reduced, and the error propagation can be diminished.

[0235] Additional information makes it possible to raise the probability for validating the plausibility of radar targets in road traffic. If a measurement of the crossed path is (directly) measured for each target, an additional estimation of velocity, azimuth angle and distance can be made available, which in particular can facilitate tracking.

[0236] Reflections of complex objects can be recognized with comparatively no problem, possibly even when they are not going in the direction of an incident wave (bistatic radar principle). A combination of several radar modules makes it possible to (distinctly) improve an estimate of a proper motion of the moving object (vehicle), since the accuracy of the angular measurement significantly influences the latter.

[0237] Combining several radar modules in the direction of elevation makes it possibly to distinctly improve a height estimate, in particular by means of interferometric SAR, i.e., an estimate of the height profile of a (complete) surroundings of a moving object (vehicle).

[0238] Aspects and embodiments of method I or configuration I will be described below. The reference numbers here relate to the figures from DE 10 2014 104 273 A1. The transmitter-receiver units can be part of the radar modules or comprise the latter:

[0239] Aspect 1: Method in a radar system, in which [0240] in a first (non-coherent) transmitter-receiver unit (NKSE1), a first signal (sigTX1) is generated and transmitted, in particular emitted, over a path (SP), [0241] in an additional, in particular second (non-coherent) transmitter-receiver unit (NKSE1), a first signal (sigTX2) is generated and transmitted, in particular emitted, over the path (SP), [0242] in the first transmitter-receiver unit (NKS1), a comparison signal (sigC12) is formed out of its first signal (sigTX1) and out of such a first signal (sigRTX2) received by the additional transmitter-receiver unit (NKSE2) over the path (SP), and [0243] in the additional transmitter-receiver unit (NKSE2), an additional comparison signal (sigC21) is formed out of its first signal (sigTX2) and out of such a first signal (sigTX1) received by the first transmitter-receiver unit (NKSE1) over the path (SP), [0244] wherein the additional comparison signal (sigC21) is transmitted, in particular communicated, from the additional transmitter-receiver unit (NKSE2) to the first transmitter-receiver unit (NKSE1).

[0245] Aspect 2: Method according to the first aspect, in which a comparison-comparison signal (sigC21; sigC12) is formed out of this comparison signal (sigC21) and the additional comparison signal (sigC21).

[0246] Aspect 3: Method according to the second aspect, in which the comparison-comparison signal (sigC21; sigC12) is made to correspond to a comparison signal generated by a coherent radar system by processing the two comparison signals (sigC12, sigC21) with each other, in particular subjecting them to conjugated complex multiplication.

[0247] Aspect 4: Method according to a preceding aspect, in which at least one of the comparison signal (sigC12), the additional comparison signal (sigC21) or the comparison-comparison signal (sigC21; sigC12) is formed via either mixing or correlation.

[0248] Aspect 5: Method according to a preceding aspect, in which at least one such additional comparison signal (sigC21; sigC12) is transmitted between the transmitter-receiver units (NKSE2; NKSE1) as at least one of data, a signal containing data or a signal reconstructably containing data.

[0249] Aspect 6: Method according to a preceding aspect, in which at least one of the first signals (sigTX2, sigTX2) is transmitted as a transmitted signal over the path (SP) designed as an air interface.

[0250] Aspect 7: Method according to a preceding aspect, in which the points in time for transmitting the first signals (sigTX1, sigTX2) are coordinated in such a way that the first signals (sigTX1, sigTX) at least partially chronologically overlap.

[0251] Aspect 8: Method according to a preceding aspect, in which a signal transmit time (τ12) that such a first signal (sigTX1, sigTX2) requires for the path between the transmitter-receiver units (NKSE1, NKSE2) is determined out of at least one comparison-comparison signal (sigC21; sigC12) by analyzing at least one of a phase or a phase value (φ12, φ13, . . . φ1N, φ22, φ23, φ24, . . . φ2N, . . . φN−1N) of a frequency, an amplitude progression or a phase progression of the comparison-comparison signal (sigCC12).

[0252] Aspect 9: Method according to a preceding aspect, in which at least one of the first signals (sigTX1, sigTX2) is generated and transmitted as an FMCW or OFDM modulated signal.

[0253] Aspect 10: Method according to a preceding aspect, in which at least one of the first signals (sigTX1, sigTX2) is generated and transmitted as a multi-ramp signal.

[0254] Aspect 11: Method according to a preceding aspect, in which [0255] several comparison-comparison signals (sigCC12) are measured chronologically one after the other with at least two transmitter-receiver units (NKSE1, NKSE2), of which at least one of the transmitter-receiver units (NKSE1, NKSE2) moves, and [0256] a synthetic aperture process is used to determine at least one of a distance, a position, a velocity or the presence of one of the transmitter-receiver units (NKSE2, NKSE1) or the presence of such a transmitter-receiver unit (NKSE2, NKSE1) or at least one of a distance, a position, a velocity relative to an object (O) or the presence of an object (O).

[0257] Aspect 12: A radar system, in which [0258] at least a first (non-coherent) transmitter-receiver unit (NKSE1) is designed to generate a first signal (sigTX1) and transmit, in particular emit, it over a path (SP), [0259] at least one additional, in particular second (non-coherent) transmitter-receiver unit (NKSE1) is designed to generate a first signal (sigTX2) and transmit, in particular emit, it over the path (SP), [0260] the first transmitter-receiver unit (NKS1) is designed to form a comparison signal (sigC12) out of its first signal (sigTX1) and out of such a first signal (sigTX2) received by the additional transmitter-receiver unit (NKSE2) over the path (SP), [0261] the additional transmitter-receiver unit (NKSE2) is designed to form an additional comparison signal (sigC21) out of its first signal (sigTX2) and out of such a first signal (sigTX1) received by the first transmitter-receiver unit (NKSE1) over the path (SP), and [0262] the additional comparison signal (sigC21) is transmitted, in particular communicated, from the additional transmitter-receiver unit (NKSE2) to the first transmitter-receiver unit (NKSE1).

[0263] Aspect 13: Radar system according to aspect 12, in which a comparison-comparison signal (sigCC21; sigCC12) is formed out of this comparison signal (sigC21) and the additional comparison signal (sigC21).

[0264] Aspect 14: Radar system according to aspect 12 or 13 with three or more transmitter-receiver units (NKSE1, NKSE2, NKSE3, . . . , NKSE-N) spaced spatially apart from each other, in which, out of two or more comparison-comparison signals (sigCC12, sigCC12, sigCC13, sigCC22, . . . , sigCC32) measured with more than two pairs of a respective two of the transmitter-receiver units (NKSE1, NKSE2; NKSE-N, NKSE2) spaced spatially apart, a distance, a position, a velocity or the presence of one of the transmitter-receiver units (NKSE2, NKSE1) or the presence of such a transmitter-receiver unit (NKSE2, NKSE1) or at least one of a distance, a position, a velocity relative to an object (O) or the presence of an object (O) is determined.

[0265] Aspect 15: Radar system according to one of aspects 12 to 14, in which the first transmitter-receiver unit (NKSE1) and at least one such additional transmitter-receiver unit (NKSE2) and/or an evaluation device (P) are designed to implement a method according to one of the preceding claims.

[0266] Aspect 16: Device of a radar system, in particular for implementing a method according to one of aspects 1 to 11 and/or in a radar system according to one of aspects 12 to 15, wherein the device [0267] is designed as a first (non-coherent) transmitter-receiver unit (NKSE1) and [0268] has a signal generator and at least one antenna (TA1; RA1), which are designed to generate a first signal (sigTX1) and transmit, in particular emit, it over a path (SP), [0269] has a layout designed to form a comparison signal (sigC12) out of the and out of such a first signal (sigTX2) received by the additional transmitter-receiver unit (NKSE2) over the path (SP), [0270] and at least one of [0271] an interface (CommTX), which is designed to transmit, in particular communicate, the comparison signal (sigC12) to the additional transmitter-receiver unit (NKSE2), or [0272] an interface (mRX), which is designed to receive such an additional comparison signal (sigC21) generated by the additional transmitter-receiver unit (NKSE2) in the first transmitter-receiver unit (NKSE1) via transmission, in particular communication.

[0273] Aspect 17: Device according to aspect 16 with an additional comparison unit (sigComp12), which forms a comparison-comparison signal (sigCC12) out of the comparison signal (sigC21) formed in the same transmitter-receiver unit (NKSE1) and the comparison signal (sigC21) transmitted to this transmitter-receiver unit (NKSE1).

[0274] Aspect 18: Device according to aspect 16 or 17, in which the at least one interface (CommTX, CommRX) is a data interface.

[0275] Aspect 19: Device according to one of aspects 16 to 18, in which 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), wherein the filter (FLT) applies the comparison signal (sigC12) to the comparison unit (sigComp12), wherein the filter (FLT) does not apply an additional comparison signal (sigC11) formed in the arrangement upstream from the filter (FLT), and suppresses the comparison signal (sigC11) formed in the upstream arrangement or provides it at a terminal.

[0276] Aspect 20: Device according to one of aspects 16 to 19, which has a plurality of receiver antennas (RA1,1, . . . , RA1,N; RA2,1, . . . , RA2,N) spaced spatially apart from each other, which each have allocated to them a layout designed to form a respective comparison signal (sigC21,1, sigC21,2, sigC21,3) out of the first signal (sigTX2) and out of such a first signal (sigTX1) received by such an additional transmitter-receiver unit (NKSE2) over the path (SP).

[0277] Aspects and embodiments of method II or configuration II will be described below. The reference numbers here relate to FIGS. 1 to 4 of the present application. The transmitter-receiver units can be part of the radar modules or comprise the latter:

[0278] Aspect 1: Method for reducing disturbances by phase noise in a radar system, in which [0279] in a first (non-coherent) transmitter-receiver unit (NKSE1), a first signal (sigTX1) is generated and transmitted, in particular emitted, over a path (SP), [0280] in an additional, in particular second (non-coherent) transmitter-receiver unit (NKSE1), a first signal (sigTX2) is generated and transmitted, in particular emitted, over the path (SP), [0281] the first signals (sigTX1 and sigTX2) are directly or indirectly received in the respective additional transmitter-receiver unit, and there further processed as received signals (sigRX12 and sigRX21), [0282] in the first transmitter-receiver unit (NKS1), a comparison signal (sigC12) is formed out of its first signal (sigTX1) and out of such a first signal (sigRTX2) received by the additional transmitter-receiver unit (NKSE2) over the path (SP), and [0283] in the additional transmitter-receiver unit (NKSE2), an additional comparison signal (sigC21) is formed out of its first signal (sigTX2) and out of such a first signal (sigTX1) received by the first transmitter-receiver unit (NKSE1) over the path (SP), [0284] wherein the additional comparison signal (sigC21) is transmitted, in particular communicated, from the additional transmitter-receiver unit (NKSE2) to the first transmitter-receiver unit (NKSE1), [0285] wherein, in a first step, deviations in the comparison signals (sigC21 and sigC12) caused by systematic deviations in the transmitter-receiver units (NKE2, NKSE1) are compensated, [0286] wherein, in a second step, at least one complex value from a first of the two comparison signals or a signal derived from this first comparison signal is used to adjust at least one complex value of the second of the two comparison signals or a value of a signal that was derived from this second comparison signal, and thereby form an adjusted signal (sigCC), [0287] wherein the adjustment takes place in such a way that a mathematical operation forms the vectorial sum or the difference of complex values, or forms the sum or the difference of the phases of the complex values.

[0288] Aspect 2: Method according to aspect 1, wherein the transmitted signals (sigTX1 and sigTX2) are FMCW modulated.

[0289] Aspect 3: Method according to aspect 1 or 2, wherein a clock rate adjustment, in particular of signal sources of the first signals (sigTX1 and sigTX2), takes place via a bus system, preferably a communications bus, and/or wherein a clock rate adjustment, in particular of clock rates for signal sources of the first signals (sigTX1 and sigTX2), takes place via radio waves and/or via a cable connection, in particular during operation as the primary radar.

[0290] Aspect 4: Method according to one of the preceding aspects, wherein a synchronization of the (non-coherent) transmitter-receiver units (NKSE1, NKSE2), in particular a pre-synchronization by determining a frequency drift, takes place over several ramps in succession, in particular when using a secondary radar.

[0291] Aspect 5: Method according to one of the preceding aspects, wherein an offset, in particular a time offset and/or a frequency offset, is determined via a bus system, preferably during operation as a primary radar.

[0292] Aspect 6: Method according to one of the preceding aspects, wherein a/the offset, in particular a/the time offset and/or a/the frequency offset, is determined by evaluating a position of in particular corrected maxima for the spectra of the comparison signals (sigC12 and sigC21).

[0293] Aspect 7: Method according to one of the preceding aspects, wherein the first and/or the additional (non-coherent) transmitter and receiver unit has at least one evaluation device for performing the individual procedural steps, in particular calculations and evaluations, wherein the respective evaluation device

is possibly a self-contained evaluation device, which is connected to the respective transmitter and receiver unit or the remaining components of the respective transmitter and receiver unit, or
is possibly integrated into the first and/or the additional (non-coherent) transmitter and receiver unit, for example in a shared housing and/or as a unit.

[0294] Aspect 8: Method according to one of the preceding aspects, wherein the comparison signals (sigC12 and sigC21) are transmitted to an in particular shared evaluation unit, and are there both present for evaluation, wherein the shared evaluation unit is optionally the first (non-coherent) transmitter-receiver unit (NKSE 1), or optionally the second (non-coherent) transmitter-receiver unit (NKSE2), or optionally another, in particular separate, evaluation unit.

[0295] Aspect 9: Method according to one of the preceding aspects, wherein the first signals (TX1 and TX2) are transmitted at least chronologically overlapping, wherein the additional first signal (TX2) of the additional (non-coherent) transmitter-receiver unit (NKSE2) is preferably transmitted during half of the signal duration of the first signal (TX1) of the first (non-coherent) transmitter-receiver unit (NKSE2), further preferably at least approximately simultaneously.

[0296] Aspect 10: Method according to one of the preceding aspects, wherein the spectra of the comparison signals are standardized to the highest value prior to the mathematical operation.

[0297] Aspect 11: System for reducing disturbances by phase noise in a radar system with units for implementing the method according to one of the preceding claims, in particular comprising: [0298] a first (non-coherent) transmitter-receiver unit (NKSE1) for generating a first signal (sigTX1) and for transmitting, in particular emitting, the first signal (sigTX1) over a path (SP), [0299] an additional, in particular second (non-coherent) transmitter-receiver unit (NKSE1) for generating a first signal (sigTX2) and for transmitting, in particular emitting, the first signal (sigTX2) over a path (SP), [0300] wherein the (non-coherent) transmitter-receiver units (NKSE1 and NKSE2) are designed to directly or indirectly receive the first signals (sigTX1 and sigTX2), and there further process them as received signals (sigRX12 and sigRX21), [0301] wherein the first transmitter-receiver unit (NKS1) is designed to form a comparison signal (sigC12) out of its first signal (sigTX1) and out of such a first signal (sigTX2) received by the additional transmitter-receiver unit (NKSE2) over the path (SP), and [0302] wherein the additional transmitter-receiver unit (NKSE2) is designed to form an additional comparison signal (sigC21) out of its first signal (sigTX2) and out of such a first signal (sigTX1) received by the first transmitter-receiver unit (NKSE1) over the path (SP), [0303] wherein a transmission unit is provided to transmit, in particular communicate, the additional comparison signal (sigC21) from the additional transmitter-receiver unit (NKSE2) to the first transmitter-receiver unit (NKSE1), [0304] wherein at least one evaluation unit is provided, which is designed in a first step to compensate for deviations in the comparison signals (sigC21 and sigC12) caused by systemic deviations in the transmitter-receiver units (NKE2, NKSE1), and in a second step to use at least one complex value from a first of the two comparison signals or a signal derived from this first comparison signal to adjust at least one complex value of the second of the two comparison signals or a value of a signal that was derived from this second comparison signal, and thereby form an adjusted signal (sigCC), wherein the adjustment takes place in such a way that a mathematical operation forms the vectorial sum or the difference of complex values, or forms the sum or the difference of the phases of the complex values.

[0305] Aspect 12: System according to aspect 11, wherein a bus system, in particular a communications bus, is provided for a clock rate adjustment, in particular of signal sources of the first signals (sigTX1 and sigTX2),

and/or wherein a bus system is provided for determining an offset, in particular a time offset and/or frequency offset.

[0306] Aspect 13: System according to one of aspects 11 or 12, wherein a shared transmitter and receiver antenna is provided in the first and/or the additional (non-coherent) transmitter-receiver unit (NKSE1 and/or NKSE2), and/or

wherein a transmission mixer is provided in the path (SP).

[0307] Aspect 14: Use of the method according to one of aspects 1 to 10 for a system with at least one shared transmitter and receiver antenna each in the first and/or second (non-coherent) transmitter-receiver unit (NKSE1 and/or NKSE2).

[0308] Aspect 15: Use of the method according to one of aspects 11 to 13 for reducing disturbances by phase noises in a radar system.

[0309] Let it be noted at this juncture that all parts or functions described above are claimed as essential to the invention, taken separately and in any combination, in particular the details shown on the drawings. Modifications thereof are familiar to the expert.