MIMO radar system

Abstract

A MIMO radar system has a transmitting array with a plurality of transmitting antennas arranged at a distance from each other in an angle resolving direction, a receiving array with a plurality of receiving antennas arranged at a distance from each other in an angle resolving direction, an antenna spacing of one of the transmitting and receiving arrays being above the Nyquist limit for a single valued angle measurement, however an antenna spacing of the combination of the transmitting and receiving arrays being below the Nyquist limit, a control and analysis processing device configured for transmitting a transmitting signal by the transmitting array in each of a plurality of measurement periods implemented repeatedly according to a periodic multiplexing scheme, converting a signal received in a measurement period into a detection space of at least two dimensions, testing a plurality of hypotheses of a plurality valuedness against an estimate, selecting a hypothesis of the plurality valuedness with a highest quality measure for a single valued Doppler measurement, performing an independent angle estimation based on the transmitting and receiving array, merging results of the independent angle estimations into a single valued angle measurement.

Description

Technical Field

[0001] This invention relates to a MIMO radar system, and more particularly to a MIMO radar system for motor vehicles. Background Technology

[0002] Radar systems are increasingly used in motor vehicles to detect traffic conditions and provide information such as distance, relative speed, and azimuth of located objects (e.g., vehicles or obstacles) to one or more safety or comfort functions that reduce the driver's workload in guiding the vehicle or completely or partially replace the human driver. MIMO (multiple input-multiple output) systems are increasingly used in this context, employing multiple transmitting and receiving antennas.

[0003] WO 2018 / 076005 A1 mentions different types of MIMO radar systems: transmitters and / or receivers can be located in different positions. Virtual channels can be generated by using mutually orthogonal codes. Time Division Multiple Access (TDMA) or Frequency Division Multiple Access (FDMA) methods can be used.

[0004] A MIMO radar measurement method is known from DE 10 2014 212 284 A1. In this method, the transmitted signal is subjected to ramp-shaped frequency modulation using a modulation mode in which a sequence of ramps is assigned to different transmit switching states and is interleaved in time. These transmit switching states differ in the selection of antenna elements used for transmission. The transmit switching states are further assigned multiple sequences that are interleaved in time. Based on the peak position of the signal obtained for a sequence in a two-dimensional spectrum, the relative velocity of the radar target is determined. These values ​​are periodic with a predetermined velocity period. The phase relationship of the spectral values ​​in the spectrum of the sequence for the transmit switching state is compared with the expected phase relationship for the corresponding periodic values ​​of the relative velocity, and an estimate for the relative velocity is selected based on the comparison result.

[0005] US 2017 / 0160380 A1 describes a MIMO radar system in which multiple transmit antennas transmit simultaneously. Pseudo-Random Phase Modulation (PRPM) is used to randomly change the phase of the signals directed to the respective transmit antennas in order to achieve orthogonality between the simultaneously transmitted and received signals.

[0006] Digital modulation methods with multiple carrier frequencies are called OFDM (orthogonal frequency division multiplexing). Increasingly, OFDM is being studied for application in radar systems. In OFDM, the frequency band is divided into multiple orthogonal subbands or subcarriers (FDM, frequency division multiplexing), and OFDM symbols are transmitted sequentially. The transmitted signal of an OFDM symbol consists of mutually orthogonal subcarrier signals modulated according to the symbol's modulation scheme; these subcarrier signals are transmitted simultaneously within the OFDM symbol period.

[0007] The applicant has proposed a MIMO radar system in which, for single-valued Doppler measurements, the repetition rate of the multiplexing sequence is below the Nyquist limit, resulting in a relative velocity measurement that, while high-resolution, is multi-valued. To resolve this multi-valuedness, the proposed method fully utilizes the fact that a demultiplexing method, which reconstructs the signal that can be single-valuedly assigned to each transmit antenna of the transmit array from the received signal only when the phase shift caused by the Doppler effect is properly corrected, provides high-quality results. However, this requires knowledge of the relative velocities of the objects involved. The resolution of multi-valuedness is achieved by testing different multi-valuedness assumptions and selecting the one that provides the signal with the highest quality metric during demultiplexing. Summary of the Invention

[0008] The objective of this invention is to propose a MIMO radar system with a simply constructed antenna array, in which the relative velocity and positioning angle of a radar object can be determined with high accuracy and a large range of single-valued values ​​within a short measurement time.

[0009] According to the present invention, this task is solved by a MIMO radar system, which has:

[0010] - A transmitting array having multiple transmitting antennas arranged at a distance from each other in an angularly resolved direction.

[0011] - A receiving array having multiple receiving antennas arranged at a distance from each other in an angularly resolved direction.

[0012] - Wherein, for single-value angle measurement, the antenna spacing in one of the transmitting and receiving arrays is higher than the Nyquist limit (spatial frequency below the Nyquist limit), however, the antenna spacing in the combination of the transmitting and receiving arrays is lower than the Nyquist limit (spatial frequency above the Nyquist limit), and has

[0013] - A control and analysis processing device, configured for,

[0014] - In each of the multiple repeated measurement cycles, the transmitted signal is transmitted via a transmit array according to a periodic multiplexing scheme, wherein the timing in the multiplexing scheme is selected such that single-valued Doppler measurements are possible.

[0015] - The signal received in one measurement cycle is converted into a detection space of at least two dimensions, in which one dimension represents an estimate of the Doppler frequency shift and another dimension represents an estimate of the positioning angle of the located object, wherein the estimate is multi-valued in at least one of these dimensions.

[0016] - The multivaluedness hypothesis is tested against the estimated values, wherein each test includes Doppler correction of the received signal based on the corresponding multivaluedness hypothesis, creating a mapping from the transmitting antenna to a combination of the Doppler-corrected received signals, and determining a quality metric for the multivaluedness hypothesis.

[0017] - The multivalued hypothesis with the highest quality metric is selected for single-valued Doppler measurements.

[0018] - Independent angle estimation is performed based on the transmit and receive arrays. Specifically, angle estimation based on the transmit array is performed using a mapping from the transmit antenna to a combination of Doppler-corrected received signals, which has been created based on a chosen multivalued assumption.

[0019] - Combine the results of independent angle estimates into a single angle measurement.

[0020] The present invention extends the previously proposed method as follows: undersampling (i.e., sampling below the Nyquist limit) is performed not only in Doppler measurements but also in angle measurements. For this purpose, the aperture of either the transmitting or receiving array is chosen such that high angle separation is achieved, but multi-valued results are obtained. Conversely, the aperture of the corresponding array is chosen such that the gaps between the antennas are filled to such an extent that single-valued results are obtained, but with lower angular resolution. If the results of the two angle measurements are then fused, a high-resolution, single-valued measurement result is obtained corresponding to the synthetic aperture produced by a relatively small total number of transmitting and receiving antennas. Thus, common data compression is achieved in both the "relative velocity" and "angle" dimensions.

[0021] However, angle estimation based on the transmitting array also necessitates the reconstruction of signals that can be individually assigned to each transmitting antenna, requiring correction of the phase step determined by the Doppler effect. Therefore, the multivalued nature of both Doppler measurements and angle measurements can be mutually resolved, enabling efficient and resource-saving signal analysis and processing.

[0022] This also discloses a method for spacing estimation, Doppler estimation, and angle estimation in a MIMO radar system, which includes the following steps:

[0023] -Perform spacing estimation

[0024] - Perform multi-valued Doppler estimation in the first stage.

[0025] - Angle estimation is performed in the first stage, or based on the receiver array.

[0026] - In the second stage, Doppler estimation and angle estimation are performed together to resolve multi-valuedness based on the transmitting array and supplement angle information.

[0027] The advantageous configurations and extensions of the present invention are derived from the extended technical solutions of the present invention.

[0028] In one implementation, the radar system is an FMCW radar or a chirp-sequence radar, in which a sequence corresponding to a steep frequency ramp (so-called chirp) modulates the frequency of the transmitted signal. The slope of this frequency ramp is so large that the Doppler effect on the ramp is negligible, and thus a pure propagation time measurement (i.e., a spacing measurement) is performed. The relative velocity is then measured by analyzing the phase shift between the ramps, which is determined by the Doppler effect.

[0029] According to the principles of MIMO, suitable multiplexing and demultiplexing methods are needed to separate signals transmitted by different antennas. Code division multiplexing (CDM) and time division multiplexing (TDM) methods are particularly noteworthy in this regard.

[0030] In code division multiplexing (CDM), signals simultaneously transmitted by transmitting antennas are encoded using orthogonal or quasi-orthogonal codes defined in a code matrix. The transmitted signals are then divided into a sequence of periodically repeating code blocks, each defining a different code division on a different transmitting antenna. The repetition rate of these code blocks corresponds to the sampling rate used for Doppler measurements. If the reciprocal of this repetition rate (i.e., the period duration) exceeds a predetermined value (the Nyquist limit), the Doppler measurement result will become multivalued.

[0031] For example, if a single code block contains nCI code instances (Code-Instanzen), each pre-defined by a different division of the code on the transmitting antenna, then the phase of the signal received in a single code block forms a vector with nCI components. In the case of a square code matrix, nCI equals the number of antennas transmitting simultaneously in the transmitting array. The received signal can then be decoded by multiplying the vector by the inverse of the code matrix. However, this is contingent on the orthogonality of the encoded signal being preserved or at least recoverable upon reflection at the radar target. If the relative velocity of the radar target is not zero, the Doppler effect causes some interference with orthogonality, resulting in the decoded signal for a given transmitting antenna also containing signal components originating from other transmitting antennas.

[0032] Therefore, to obtain measurement results with high-quality metrics, the received signal must be corrected for the Doppler effect, which is only successful if, among the multivalued values ​​obtained when measuring the Doppler frequency shift, the value corresponding to the true relative velocity of the object is precisely selected. Thus, multivaluedness can be discerned based on quality metrics. For example, in the case of orthogonal codes, the quality of the angle estimation can be used as a metric for the quality of the decoding.

[0033] In another implementation, time-division multiplexing can be used instead of code-division multiplexing. In this case, only one transmit antenna of the transmit array is active at any given time, and switching between different transmit antennas occurs according to a periodic scheme. Here, the order in which the individual antennas are activated is typically different from the order in which the antennas are spatially arranged in the transmit array. Therefore, due to the time offset (with which signals are transmitted), the relative motion of the radar target causes characteristic phase shifts between the signals obtained from the different transmit antennas, and these phase shifts can be distinguished from the phase shifts resulting from angle-dependent propagation time differences when signals are transmitted at a defined angle relative to the normal of the transmit array. In this case, phase errors caused by relative motion can also be corrected by selecting the correct assumption or the correct pair of assumptions among different multivalued assumptions for Doppler shift and / or the positioning angle of the object, and using this as the basis for correction.

[0034] Another possible implementation of the present invention is a combination of code division multiplexing and time division multiplexing.

[0035] Similarly, it is conceivable to implement a non-square code matrix. If the number of code instances is less than the number of transmitting antennas, an underdetermined set of equations is obtained during decoding; however, this underdetermined set of equations can be solved with the aid of credible additional assumptions (e.g., regarding the number of simultaneously located radar targets). Conversely, if there are more code instances than transmitting antennas, an overdetermined set of equations can be achieved. In this case, greater robustness in multivalued resolution is achieved, for example, relative to signal noise or other interference effects.

[0036] In one implementation, the receiving array has a large, partially filled aperture, resulting in high-resolution but multi-valued angle estimation based on the receiving array, while the transmitting array has a fully filled but smaller aperture, thus enabling single-valued angle measurements with lower resolution. However, in another implementation, the transmitting array may have a large aperture while the receiving array has a small aperture. Attached Figure Description

[0037] The following describes the embodiments in further detail with reference to the accompanying drawings.

[0038] Figure 1 A schematic diagram of the simulation portion of a MIMO radar system with independent spacing and velocity determination is shown.

[0039] Figure 2 The frequency diagram and modulation scheme diagram of the FMCW transmitted signal are shown.

[0040] Figure 3 The diagram shows the antenna array of the radar system.

[0041] Figure 4 This diagram shows the positioning angle range of the radar system.

[0042] Figure 5 A block diagram of a digital signal analysis and processing apparatus according to an embodiment of the present invention is shown;

[0043] Figure 6 and Figure 7 A block diagram of a digital signal analysis and processing apparatus according to another embodiment of the present invention is shown. Detailed Implementation

[0044] based on Figures 1 to 4 An example of a fast linear frequency modulated MIMO radar system will be described as an example of an FMCW-MIMO radar system, in which the encoding of the transmitted signal is performed by means of phase modulation. Figure 1 The structure of the analog section of the radar system is shown schematically and in a simplified manner.

[0045] Frequency modulation device 10 controls HF oscillator 12, which generates a sequence of identical signals in the form of frequency ramps for multiple transmitting antennas 14. In each of the multiple transmitting channels, a corresponding phase modulator 16 connected in front of amplifier 18 modulates the phase of the signal according to a corresponding code 20 generated by code generator 22. The phase-modulated signal is transmitted through one of the transmitting antennas 14. The transmitted signal, reflected at object 24, is received by multiple receiving antennas 26, and in each receiving channel, it is mixed with the unmodulated portion of the signal from HF oscillator 12 by mixer 28 and brought into the low-frequency range. Then, A / D conversion is performed in the usual manner by A / D converter 30.

[0046] exist Figure 2 The diagram schematically illustrates the frequency variation process of the transmitted signal and the scheme of code block 32 below it, by means of which the transmitted signal is phase modulated.

[0047] Using a "fast linear frequency modulation" scheme with a sequence having a relatively "fast" frequency ramp 34, the analysis and processing of spacing and velocity can be performed substantially independently, for example, by means of a two-dimensional Fourier transform. In particular, the Doppler frequency shift within the ramp can be neglected.

[0048] according to Figure 2The codes 20 for each transmit antenna 14 are combined into code block 32. Code block 32 assigns the code values ​​A, B, C, ... of the relevant code 20 to each signal for a single transmit antenna. A single code value defines the phase of the signal by which the phase modulator 18 modulates. Therefore, at each code moment, also called code instance I, i.e., at each position within code 20, code block 32 defines the relevant code value for each transmit antenna. The number of codes 20 in code block 32 corresponds to the number of transmit antennas transmitting simultaneously. In the sequence of code instances I = 1, ..., m, for each transmit antenna, the phase modulation traverses the code values ​​of the relevant codes. Figure 2 As shown, code block 32 is set to 1 / T C2C The repetition rate (corresponding to the period duration T) C2C Repeat in the same way. Figure 2 The indexes C# = 1...k in the code block count the repetitions, while the indices TX = 1...n (n = m) number the transmitting antennas. The codes 20 of code block 32 are orthogonal to each other (preferably fully orthogonal, or alternatively quasi-orthogonal, i.e., with a small Kreuz-Korrelation between the codes). Therefore, the signals from each transmitting antenna are encoded by codes; the transmitted signals are mutually orthogonal so that signal separation can be achieved in the receiving channel.

[0049] like Figure 3 As shown, transmitting antenna 14 forms transmitting array 36, and receiving antenna 26 forms receiving array 38. In the example shown, both arrays are two-dimensional, thus enabling MIMO angle measurements in both azimuth and elevation.

[0050] In the receiver array 38, the receiver antennas 26 are arranged at a uniform spacing in the angular resolution direction y (e.g., in the azimuth direction). The large spacing between the individual receiver antennas allows for a large aperture and correspondingly high angular resolution with a small number of antennas. However, here, the antenna-to-antenna spacing is greater than half the wavelength of the radar beam, thus failing to satisfy the Nyquist single-valuedness criterion.

[0051] exist Figure 4 The image shows the field of view of the radar sensor, which includes angles from -θ to +θ relative to the axis x perpendicular to the plane of the receiving array 38. Only when the positioning angle is within the range of -θ... a to +θ a Within a small interval, the angle measurement result is single-valued. If larger positioning angles cannot be excluded, multiple angles exist, for which the signals at the receiving antenna obtain the same phase relationship, thus the measurement is no longer single-valued.

[0052] exist Figure 3 In the example shown, the receiving antenna 26 is also arranged at a uniform spacing in the elevation angle (in the angularly resolved direction z), and the antenna spacing in this direction is so large that non-single-value undersampling is performed.

[0053] The transmitting antennas 14 of the transmitting array 36 are arranged at a uniform spacing in the azimuth angle, but this spacing is chosen to enable single-value angle measurements. However, for this purpose, the aperture is significantly smaller than the aperture in the receiving array 38, resulting in lower angular resolution. In the elevation angle, the transmitting array 36 also utilizes a small aperture design for single-value angle measurements.

[0054] exist Figure 3 Additionally, a composite array 40 is shown, which is obtained by combining each of the receiving antennas 26 with each of the transmitting antennas 14, such that the propagation time difference of the signal from the transmitting antenna to the object and the propagation time difference from the object to the receiving antenna are added together. Ultimately, it is the aperture of this virtual array 40 that determines the resolving power of the radar sensor. However, it is necessary to separate the signal components originating from the different transmitting antennas 14 in the received signal so that the multivalued nature of the receiving array can be discerned.

[0055] exist Figure 3 In the example shown, in the receiver array 38, the two angle-resolved directions y and z are also decoupled from each other because for every y-position of the receiver antenna, all z-positions are also occupied by the receiver antenna. Conversely, the transmitter array 36 is an example of a non-decoupled array in which, for several y-positions ( Figure 3 (Two positions on the right side of the array), not all z positions are occupied. Generally, decoupled arrays facilitate data analysis and processing, while non-decoupled arrays require fewer antenna elements. Depending on the specific requirements, different decisions can be made between decoupled and non-decoupled arrays for the transmitting and receiving sides.

[0056] The equidistant arrangement of antenna elements (in azimuth and / or elevation) also facilitates data analysis and processing, as this equidistant arrangement enables the use of, for example, Fast Fourier Transform (FFT). On the other hand, as in transmitting antenna 14 here, a non-equidistant arrangement of the antenna has the advantage of optimizing the single-valued angular range for a given aperture. Figure 4 ).

[0057] Typically, in the radar system described herein, all combinations of equidistant and non-equidistant arrangements, as well as decoupled and non-decoupled arrangements, are conceivable. Similarly, implementations are also possible in which the transmitting array is designed for multi-valued, high-resolution angle measurements, while the receiving array is designed for single-valued angle measurements with lower angular resolution.

[0058] Now based on Figure 5 An example of an analytical processing apparatus is described, which is used for analyzing and processing data using... Figure 3 Antenna array and by means of Figure 2 The received signal obtained by the multiplexing scheme.

[0059] The digital data provided by the A / D converter 30 is sampled separately within a complete measurement cycle. The total number of (complex) signal values ​​recorded within the measurement cycle is given by the product of the following: the number of receiving antennas 26 of the receiving array 38, nRX; the number of code instances I, nCI; the number of repetitions of code block 32 within the measurement cycle, ns; and the number of sampling points on a single frequency ramp 34, nf. In the processing stage 42, the data sampled within the measurement cycle undergoes a four-dimensional Fourier transform (4D-FFT). The result is a four-dimensional spectrum with the following dimensions: "azimuth 1", "elevation 1", "Doppler 1", and "spacing". The dimension "azimuth 1" describes the distribution of complex amplitude over the azimuth angle range based on the data of the receiving antennas 26 arranged in the same row in the azimuth direction. Correspondingly, the dimension "elevation 1" describes the distribution over the elevation angle range based on the data of the receiving antennas 26 arranged in the same column in the elevation direction. The dimension "Doppler 1" is described by the code block repetition rate 1 / T. C2C The Doppler spectrum is obtained by "slow" sampling of the code block. It should be noted that the results in all three dimensions are multi-valued due to the corresponding undersampling. The "Spacing" dimension describes the spacing spectrum based on "fast" sampling on each frequency ramp 34. In this dimension, the result is single-valued. A separate spectrum is obtained for each transmitted ramp.

[0060] The four-dimensional spectrum is incoherently integrated (the sum of the absolute values ​​of the complex amplitudes). The result is the amplitude distribution in the four-dimensional probe space 44. Each point in this four-dimensional space is assigned a definite value of the amplitude sum, and each located object in this space is represented by a peak (local maximum) at a definite spacing, a definite Doppler shift, a definite azimuth angle, and a definite elevation angle, where the latter three parameters are multivalued, so that the object can only be assigned one of several hypotheses about the relative velocity, and similarly, only one of several hypotheses about the azimuth and elevation angles. Then, the four-dimensional coordinates of the found peaks are searched in the probe space 44, each peak representing a probe result. For each of these points, (before the incoherent integration) there are nCI complex amplitudes, which form a vector with nCI components, and these are now further analyzed to resolve the remaining multivaluedness.

[0061] Therefore, in testing phase 46, different triple hypotheses of the multivaluedness hypothesis are tested. Each multivaluedness hypothesis includes: a value for the Doppler frequency shift that can still be considered given the multivalued parameter "Doppler 1"; one of the possible values ​​for the azimuth angle that can be considered due to the multivalued parameter "azimuth 1"; and one of the elevation angles described by the multivalued parameter "elevation 1". Thus, all these triple hypotheses together cover all possible combinations of Doppler frequency shift and angle. Each triple hypotheses specifically includes an assumed value for the Doppler frequency shift and therefore for the relative velocity. This value can now be used to correct the phase appearing in the signal vector corresponding to the relative velocity. This restores the orthogonality of the code in the code instance, so that if the assumption for the relative velocity is correct, correct decoding can be achieved, and a decoded signal vector is obtained, whose components respectively describe the phase of the signal originating from one of the transmitting antennas 14. Then, based on the vector components belonging to the transmitting antenna 14 arranged in the azimuth direction, a single (but low-resolution) value for the azimuth angle can be determined, and correspondingly, based on the components belonging to the transmitting antenna arranged in the elevation direction, a single value for the elevation angle can be determined.

[0062] If the assumptions used for relative velocity are incorrect, the decoding will not be entirely successful. In this case, the quality of the angle estimates in azimuth and elevation will also be lower.

[0063] Based on these criteria, multivalued resolution can now be performed in the second detection phase 48. To this end, the phase-corrected, decoded signal vectors obtained from the multivalued hypothesis test are combined (e.g., coherently added) into a three-dimensional spectrum. This spectrum has dimensions “Doppler 2”, “azimuth 2”, and “elevation 2”, and the sharpest (and highest) peaks in the spectrum represent the true, single-valued values ​​for the relative velocity, azimuth, and elevation of the object. Multiple targets can also be resolved in this three-dimensional space in the same manner.

[0064] The results obtained in the first detection phase 14, namely "Doppler 1," "azimuth 1," and "elevation 1," are high-resolution but multi-valued, while the results obtained in the second detection phase 48 are low-resolution but single-valued. These results can now be fused by selecting the value from the multiple high-resolution values ​​used for "Doppler 1" that best matches "Doppler 2" as the final, single-valued value for relative velocity. Correspondingly, the values ​​used for azimuth and elevation will also be fused.

[0065] Since each located object may have a different relative velocity, the verification phase 46 and the second detection phase 48 are performed separately for each detection result obtained in the detection space 44.

[0066] exist Figure 1 The architecture of the radar system shown also allows for an alternative operating mode in which the transmitted signal is transmitted using time division multiplexing instead of code division multiplexing. In this case, the code generator 22 manipulates the various amplifiers 18 such that only one transmitting antenna is active at any given time, and switches between the transmitting antennas in a defined order. This switching then corresponds to... Figure 2 The period duration T C2C The periodic duration (always in the same order) repeats periodically. Then, there is no need to encode the transmitted signals, because the transmitted signals are already separated from each other by transmitting them with a time offset. Nevertheless, phase correction is still required for the received signals in time division multiplexing to compensate for the time offset between signals transmitted sequentially by transmit antenna 14. Similar to the phase correction used to restore orthogonality in code division multiplexing, in this case, the phase correction is also based on the multivalued assumption regarding relative velocity.

[0067] Similarly, the following operating mode can be conceived: in this mode, code division multiplexing and time division multiplexing are combined. In this case, the transmitting antenna 14 is subdivided into multiple groups, which transmit simultaneously, and their signals are encoded with correspondingly smaller code matrices.

[0068] For in Figure 5There are different alternatives to the signal analysis and processing types shown.

[0069] Figure 6 An example is shown where digital data sampled within a measurement cycle initially undergoes a two-dimensional Fourier transform in processing stage 42 only in the dimensions “Doppler 1” and “spacing”. Therefore, for each detected object, the first detection stage provides only one value for the spacing and different assumptions for the parameter “Doppler 1”. The complex amplitude for the detected object is provided to the first angle estimation stage 50, where angle estimation is performed based on the phase values ​​obtained for different receiving antennas 26. In the example shown here, for simplicity, it is assumed that the radar sensor is angle-resolved only in the azimuth angle. It is obviously possible to extend this to angle estimation in the elevation angle as well.

[0070] Then, in the verification phase 46, the multivaluedness hypothesis is verified by phase correction for the assumed relative velocity and decoding of the phase-corrected signal vector. In this way, a single-valued value for the relative velocity, "Doppler 2," and a set of signals TX assigned to the simultaneously activated transmitting antenna 14 are obtained. Then, based on these signals, angle estimation based on the transmitting array 36 is performed in the second angle estimation phase 52, thereby obtaining a single-valued value for the azimuth angle, "azimuth 2." Thus, in the second detection phase 48, for each detection result of the first phase, a three-dimensional spectrum in dimensions "Doppler 2," "azimuth 1," and "azimuth 2" is obtained. Then, the values ​​for "Doppler 1" and "Doppler 2," and for "azimuth 1" and "azimuth 2," are fused in the manner already described.

[0071] exist Figure 7 Another variation of the analysis and processing method is illustrated. In this method, in processing stage 42, a three-dimensional Fourier transform is performed in dimensions “Doppler 1”, “spacing”, and “azimuth 1” to obtain single-valued spacing values ​​and multi-valued values ​​“Doppler 1” and “azimuth 1” in the probe space 44. Then, in verification stage 46, phase correction and decoding are performed for each probe result and each Doppler hypothesis. Then, in angle estimation stage 52, angle estimation based on the transmitting array 36 is performed using the decoded signal to obtain a single-valued value “azimuth 2” for the azimuth. Then, in the second probe stage 48, peaks in the two-dimensional spectrum are searched for in dimensions “Doppler 2” and “azimuth 2” for each probe result, and then the probe results obtained in probe stages 44 and 48 are fused in the manner already described.

[0072] In the radar system (in this radar system, and in...) Figure 3Unlike the transmitting array (which has a large, unfilled aperture, while the receiving array has a smaller aperture), the described analysis and processing methods can still be applied, but with the roles of the transmitting and receiving arrays interchanged.

Claims

1. A MIMO radar system, the MIMO radar system comprising: The transmitting array (36) has a plurality of transmitting antennas (14) arranged at a distance from each other in an angularly resolved direction. A receiving array (38) having a plurality of receiving antennas (26) arranged at a distance from each other in the angularly resolved direction. in, For single-value angle measurements, the antenna spacing in one of the transmitting and receiving arrays is above the Nyquist limit; however, the antenna spacing in the combination of the transmitting and receiving arrays is below the Nyquist limit. A control and analysis processing device is configured to transmit a signal through the transmission array according to a periodic multiplexing scheme in each of a plurality of repeatedly performed measurement cycles, wherein the timing in the multiplexing scheme is selected such that single-valued Doppler measurements are possible. The received signal received in one measurement cycle is converted into at least a two-dimensional detection space (44), in which one dimension represents an estimate for the Doppler frequency shift and another dimension represents an estimate for the positioning angle of the located object, wherein the estimate in at least one of the dimensions is multi-valued. The multivaluedness assumptions of the estimated values ​​are tested, wherein each test includes: performing Doppler correction of the received signal based on the corresponding multivaluedness assumption, creating a mapping from the transmitting antenna (14) to a combination of the Doppler-corrected received signals, and determining a quality metric for the multivaluedness assumption. The multivaluedness assumption, which yields the highest quality metric, is selected for single-valued Doppler measurements. Independent angle estimation is performed based on the transmitting array (36) and the receiving array (38), wherein the angle estimation based on the transmitting array (36) is based on a mapping from the transmitting antenna to the combination of the Doppler-corrected received signal, and the mapping has been created based on a selected multivalued assumption. The results of the independent angle estimates are fused into a single-value angle measurement.

2. The radar system according to claim 1, wherein the multiplexing scheme comprises code division multiplexing for at least a plurality of transmitting antennas in the transmitting antenna (14).

3. The radar system according to claim 1 or 2, wherein the multiplexing scheme comprises time-division multiplexing for at least a plurality of transmitting antennas in the transmitting antenna (14).

4. The radar system according to claim 1 or 2, wherein the transmitted signal (20) comprises a sequence of frequency ramps (34), the slope of which is designed for spacing measurement according to the FMCW principle, and the Doppler measurement is based on the relative phase of the signal obtained by periodic repetition of the multiplexing scheme.

5. The radar system according to claim 1 or 2, wherein the transmitting array (36) is designed for single-value angle measurement and the receiving array (38) is designed for multi-value angle measurement with higher resolution.

6. The radar system according to claim 1 or 2, wherein the receiving array (38) is designed for single-value angle measurement and the transmitting array (36) is designed for multi-value angle measurement with higher resolution.

7. The radar system according to claim 1 or 2, wherein the receiving antenna (26) and / or the transmitting antenna (14) are arranged equidistantly in the angular resolution direction.

8. The radar system according to claim 1 or 2, wherein in the radar system, in the at least two-dimensional detection space (44), the estimate for Doppler frequency shift and the estimate for positioning angle are both multivalued, and the test of the multivaluedness hypothesis includes the test of different combinations of the hypothesis for Doppler frequency shift and the hypothesis for positioning angle.

9. The radar system according to claim 1 or 2, wherein, The angle estimation (50) based on the receiving array (38) is performed independently of the test of the multivalue hypothesis.

10. The radar system according to claim 9, wherein the receiving antenna (26) is arranged equidistantly in the angular resolution direction, and the angle estimation based on the receiving array (38) is performed by Fast Fourier Transform (FFT).

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