METHOD FOR DETERMINING AT LEAST ONE OBJECT INFORMATION AT LEAST ONE OBJECT DETECTED BY A RADAR SYSTEM AND RADAR SYSTEM

Description

Technical field

[0001] The invention is defined by the independent claims.

[0002] The invention relates to a method for determining at least one object information of at least one object that is detected with a radar system, in which at least four transmitters send signals in the form of chirps, each in chirp sequences, into a monitoring area of ​​the radar system; at least one receiver, at which at least one object is at least one object, receives the reflected echoes of the signals as received signals and, if necessary, converts them into a form usable by an electronic control and / or evaluation device; the received signals are subjected to at least one two-dimensional discrete Fourier transform; at least one target signal is determined from the result of the at least one two-dimensional discrete Fourier transform; at least one object information is determined from the at least one target signal; on the transmitter side, at least one first transmit signal and at least three other transmit signals are generated from a frequency-modulated continuous wave signal and each is simultaneously sent into the monitoring area of ​​the radar system with its own transmitter.wherein the at least three other transmitted signals are each encoded by means of phase modulation relative to the at least one first transmitted signal, wherein the respective phase positions of the at least three other transmitted signals are incremented or decremented from one chirp to the next by a respective constant phase shift amount, wherein different phase shift amounts are used for the at least three other transmitted signals, and wherein the respective phase shift amounts for the at least three other transmitted signals are specified such that for at least four of the transmitted signals, including the at least one first transmitted signal, the absolute differences between the phase shift amounts of any two of the at least four transmitted signals are different. Furthermore, the invention relates to a radar system for determining at least one piece of object information about at least one object.with at least four transmitters for sending signals in the form of chirps in chirp sequences into a monitoring area, with at least one receiver for receiving echoes of the signals reflected by the at least one object as received signals, and with at least one control and / or evaluation device for controlling the at least four transmitters and the at least one receiver and for evaluating the received signals. State of the art

[0003] From WO 2018 / 137836, a method for determining at least one piece of object information about at least one object detected by a radar system, in particular a vehicle, is known. In this method, at least one transmitter sends signals into a monitoring area of ​​the radar system. At least one receiver receives the echoes of the transmitted signals reflected by the at least one object as received signals and, if necessary, converts them into a form usable by an electronic control and / or evaluation unit. The received signals are subjected to at least one two-dimensional discrete Fourier transform. At least one target signal is determined from the result of the at least one two-dimensional discrete Fourier transform. At least one piece of object information is determined from the at least one target signal.On the transmitter side, at least one first transmit signal and at least one second transmit signal are generated from a frequency-modulated continuous wave signal. The at least one second transmit signal is encoded relative to the at least one first transmit signal by means of phase modulation, whereby the phase of the at least one second transmit signal is incremented or decremented by a constant amount from one frequency ramp to the next. When phase modulating multiple second transmit signals, different phase increments can be used for the respective second transmit signals. The at least one first transmit signal is transmitted simultaneously into the surveillance area of ​​the radar system by at least one first transmitter, and the at least one second transmit signal is transmitted simultaneously by at least one second transmitter.The control and evaluation unit allows the transmitters to be controlled in such a way that the first transmitter sends the first signal, the second transmitter the second signal, and a third transmitter sends a third signal simultaneously into the monitoring area.

[0004] The invention is based on the objective of designing a method and a radar system of the type mentioned at the outset, in which any ambiguities with regard to object information, in particular distance, speed and / or direction of the at least one object relative to the radar system, can be resolved more easily and / or reliably. Disclosure of the invention

[0005] This problem is solved according to the invention by specifying the respective phase shift values ​​for the at least three other transmitted signals such that for at least four of the transmitted signals, including the at least one first transmitted signal, the absolute differences between the phase shift values ​​of three of the at least four transmitted signals are different.

[0006] According to the invention, at least one target signal is assigned to a corresponding transmit signal and thus validated. Through the phase modulation of the transmit signals according to the invention, the corresponding target signals resulting from the various transmitters, particularly when considered in the Doppler dimension, are shifted relative to each other, thus forming a unique overall pattern. Depending on the number of available modulation stages of the phase modulation, significantly more than four transmitters can be used simultaneously. The transmit signals are completely orthogonal at the output of the two-dimensional Fourier transform, in particular FFT. The method can be extended to a correspondingly large number of simultaneously active transmitters by using higher-level modulation techniques.

[0007] The invention enables the implementation of a MIMO radar using fast chirp signals. The MIMO radar can be operated using a Doppler multiplexing method. By applying different constant increments to the phases of the transmitted signals at the individual transmitters, signals can be generated that, after a two-dimensional discrete Fourier transform performed at the receiver, are shifted along the Doppler dimension and are therefore orthogonal.

[0008] A chirp is a signal whose frequency changes over time. The frequency profile of a chirp can be represented as a frequency ramp.

[0009] According to the invention, the respective phase shift values ​​for the at least three other transmitted signals are specified such that for at least four of the transmitted signals, including the at least one first transmitted signal, the absolute differences between the phase shift values ​​of any two of the at least four

[0010] The transmitted signals are different. In this way, the occurrence of interference between target signals, which can originate from different targets with different velocities at the same distance, particularly in a distance Doppler cell with the same distance value, is reduced. Interference between two target signals from targets with different velocities in the same distance cell can potentially occur without the invention if their velocities differ by exactly an integer multiple of a selected distance between the transmitters in the Doppler dimension. With the invention, interference between target signals from multiple targets with different velocities can also be avoided when using multiple transmitters.

[0011] According to the invention, after the Fourier transform, different Doppler offsets are realized on the receiver side in a distance Doppler matrix for the different transmitters due to the different phase shift magnitudes on the transmitter side. The Doppler offset for a transmitter results as an individual fraction of the uniqueness range in the Doppler dimension. The uniqueness range can be characterized in the distance Doppler matrix by a predetermined number of distance Doppler cells in the Doppler dimension. Accordingly, the uniqueness range on the transmitter side can correspond to a phase shift of 360°. The phase shift magnitudes of the different transmitters can each be specified as an individual fraction of 360°.

[0012] Advantageously, at least one second transmit signal can be encoded relative to at least one first transmit signal by means of phase modulation, such that at least temporary signal-technical orthogonality between the transmit signals is achieved.

[0013] At least four transmitters are active simultaneously. This allows the acquisition of object information to be accelerated.

[0014] By using different phase shift values ​​in the phase modulation of the at least three other transmitted signals, the at least three other transmitted signals can be realized orthogonally to each other and to the at least one first transmitted signal.

[0015] The reflected echoes are received as signals at the receiver and, if necessary, converted into a form usable by an electronic control and / or evaluation unit. If the transmitted signals and the resulting echoes are of a signal type that cannot be directly processed by the corresponding electronic control and / or evaluation unit, the received signals are converted into an electronically usable form. Otherwise, no corresponding adaptation, in particular conversion, of the received signals is necessary. In this way, the received signals can be processed by the electronic control and / or evaluation unit directly or, if necessary, after appropriate adaptation.

[0016] The method can advantageously be implemented using at least one means, either in software and / or hardware, in particular by means of a control and / or evaluation unit.

[0017] Advantageously, the radar system can utilize rapid frequency modulation. This involves transmitting several chirps in succession as a sequence.

[0018] Advantageously, the phase modulation can be synchronized with the chirps (chirp clock). This allows the required frequency of the code sequence, and therefore the required signal bandwidth, to be kept correspondingly low.

[0019] From the result of at least one two-dimensional discrete Fourier transform, a plurality of target signals can be determined, the number of which for each physically present target corresponds at most to the total number of the first and three other transmitted signals. A physically present target can be part of a detected object. Target signals can also be referred to as radar targets.

[0020] The invention can be used in a vehicle's radar system, particularly a motor vehicle. Advantageously, the invention can be used in a land vehicle, especially a passenger car, truck, bus, motorcycle, or the like, an aircraft, and / or a watercraft. The invention can also be used in vehicles that can be operated autonomously or at least semi-autonomously. However, the invention is not limited to vehicles. It can also be used in stationary radar systems.

[0021] The radar system can advantageously be connected to, or be part of, at least one electronic control device of the vehicle, in particular a driver assistance system and / or a chassis control system and / or a driver information system and / or a parking assistance system and / or a gesture recognition system or the like. In this way, the vehicle can be operated autonomously or semi-autonomously.

[0022] The radar system can detect stationary or moving objects, in particular vehicles, people, animals, plants, obstacles, road surface irregularities, in particular potholes or stones, road boundaries, traffic signs, open spaces, in particular parking spaces, precipitation or the like.

[0023] In an advantageous embodiment of the method, the phase of the at least one first transmission signal can be kept constant from one chirp to the next, and a corresponding phase shift of zero can be used. In this way, object information can be directly derived from target signals that can be assigned to the at least one first transmission signal.

[0024] In a further advantageous embodiment of the method, the at least three other transmitted signals can be encoded such that the magnitude differences between the phase shift values ​​of any two of the at least four transmitted signals are different for all transmitted signals, including the at least one first transmitted signal. In this way, the number of interfering target signals can be further reduced.

[0025] In a further advantageous embodiment of the method, the phase shift values ​​of the transmitted signals can be specified such that there are no two phase shift values ​​where the absolute difference between at least one of the two phase shift values ​​and the phase shift value of another transmitted signal corresponds to that of another transmitted signal. In this way, the number of interfering target signals can be minimized.

[0026] In a further advantageous embodiment of the method, the phase shift magnitude of at least one of the at least three other transmitted signals can be specified as the mathematical product of a basic phase shift magnitude and a Golomb number from a Golomb ruler assigned to said transmitted signal. In this way, the effort required to determine suitable phase shift magnitudes can be reduced.

[0027] In number theory, a Golomb ruler is a ruler where no two markings at integer positions are equidistant. Golomb rulers are categorized by their order and length. The order of a Golomb ruler is defined by the number of markings, and the length by the greatest distance between any two markings.

[0028] The advantage of the irregular arrangement of the target signals in the Doppler dimension increases with the number of simultaneously used transmitters. With a larger number of transmitters, the structure of the Golomb ruler becomes significantly more complex. Up to the maximum order of available Golomb rulers, at least one suitably appropriate Golomb ruler exists for any given order and thus for a corresponding number of transmitters.

[0029] In a high-resolution radar system (HD radar) with multiple simultaneously active transmitters, the invention minimizes the overlap of target signals for all possible constellations of multiple targets. A large proportion of the target signals remain undisturbed. In this way, the interference of multiple target signals can be reliably reduced to a minimum.

[0030] In an HD radar, a multitude of transmitters, particularly more than 12 transmitters, can send out individual signals. A multitude, particularly 128 or 256, of distance Doppler cells in the Doppler dimension can define the uniqueness range of the Doppler dimension. Without the method according to the invention, the number of possible interferences of target signals increases with the number of transmitters used simultaneously. For example, when using 12 simultaneously active transmitters, up to 11 of the 12 signals overlap in the distance Doppler matrix without the invention. With the method according to the invention, at most one signal overlaps in the distance Doppler matrix at any given time. The remaining 11 signals remain undisturbed.

[0031] Advantageously, the smallest phase shift value can be specified as smaller than the uniqueness range for the phase shift divided by the length of the Golomb ruler. The length of the Golomb ruler is the greatest distance between two markers. Advantageously, the smallest possible step for the phase shift can be specified as 360° / Q, where Q is a power of two. In this way, all target signals fit into a corresponding distance Doppler matrix with the appropriate uniqueness range of the Doppler dimension.

[0032] In a further advantageous embodiment of the method, the Golomb ruler can be used whose order is less than or equal to the number of transmitted signals, including the at least one first transmitted signal, to which different phase shift values ​​are to be assigned. If the order of the Golomb ruler corresponds to the number of transmitted signals, the number of possible interferences from multiple target signals at the receiver can be minimized.

[0033] If the order of the Golomb ruler is smaller than the number of transmitted signals, the Golomb ruler can still be used even if the number of transmitted signals is larger than the largest currently available order for Golomb rulers.

[0034] The largest Golomb ruler currently known has an order of 27. It is expected that Golomb rulers with orders greater than 27 will be determined in the future. In this way, the determination of phase shift magnitudes according to the invention using Golomb rulers will become possible in the future for an ever-increasing number of transmitters capable of simultaneously transmitting an ever-increasing number of signals.

[0035] In an advantageous embodiment of the method, a plurality of target signals can be determined on the receiver side from the result of at least one two-dimensional discrete Fourier transformation in a distance Doppler matrix.

[0036] Advantageously, the number of target signals per physically present target can correspond at most to the total number of first and other transmitted signals in one beat of the chirp sequence.

[0037] In a further advantageous embodiment, a power window can be determined for each distance Doppler cell on the receiver side from the distance Doppler matrix. A power window matrix can then be derived from these power windows, and a plurality of target signals can be assigned to respective transmitted signals using this matrix. In this way, the target signals can be validated.

[0038] For a distance Doppler cell, the corresponding power window PW can be determined using the following formula: PW r d = ∑ m = 0 GR _ Order − 1 SPEC r mod GR _ Marks m + d , D

[0039] Here, GR_Marks is the Golomb number of a Golomb ruler with order GR_Order. The order GR_Order corresponds to the number of transmitters used or the number of different transmitted signals. The distance values ​​r of the distance Doppler cells are from the range [0; R], where R is the number of distance Doppler cells of the distance Doppler matrix in the distance dimension. The Doppler values ​​d for the distance Doppler cells in the Doppler dimension are from the range [0; D], where D is the number of distance Doppler cells of the distance Doppler matrix in the Doppler dimension.

[0040] The following equations can be used to assign the correct complex values ​​to the corresponding transmitters from the original two-dimensional Fourier transform: 2 D - FFT TX 1 = 2 D - FFT D m + GR _ Marks 0 2 D - FFT TX 2 = 2 D - FFT D m + GR _ Marks 1 ... 2 D - FFT TXN = 2 D - FFT D m + GR _ Marks N - 1

[0041] Here, N is the number of transmitters. TX1 to TXN are the transmitter designations. Rm is the index for the cell for a detected target in the power matrix in the distance dimension. Dm is the index for the cell for a detected target in the power matrix in the Doppler dimension.

[0042] Optionally, an additional check can be performed in the same cell Rm in the distance dimension if there are other neighboring detections to cell Dm in the Doppler dimension that have colliding peaks in the distance-Doppler matrix. For the search, detections in cells in the Doppler dimension within the range [mod(Dm + GR_length, D), mod(Dm - GR_length, D)] can be checked. If a detection is found in this range, a further check can be performed to find possible collisions in the distance-Doppler matrix. These colliding cells in the Doppler dimension can be marked, and this information can be used for signal processing in the MIMO radar.

[0043] In a further advantageous embodiment of the method, at least one piece of object information can be determined from at least one target signal. In this way, the monitoring area can be described using the object information.

[0044] Advantageously, at least one piece of object information can be determined from at least one validated target signal. Validated target signals are target signals that can be uniquely assigned to a transmitted signal.

[0045] In a further advantageous embodiment of the method, at least one object piece of information in the form of a speed and / or a position, in particular a distance and / or a direction, of the at least one object relative to the radar system can be determined from at least one target signal. In this way, information about the at least one object can be obtained with the radar system, which is particularly useful for controlling the driving functions of a vehicle.

[0046] In a further advantageous embodiment of the method, a single two-dimensional discrete Fourier transform, in particular a single two-dimensional fast Fourier transform, can be performed. In this way, information from both the at least one first transmitted signal and from the at least three other transmitted signals can be processed using only a single two-dimensional, and especially fast, Fourier transform. This allows the method to be executed more efficiently.

[0047] In a further advantageous embodiment of the method, the at least three other transmitted signals can be encoded on the transmitter side using binary or higher-level phase-shift keying. In this way, signal orthogonality between the transmitted signals can be achieved.

[0048] Advantageously, the encoding of at least three other transmitted signals can occur in sync with the chirp sequences. In this way, successive chirps with linear frequency ramps can be selectively transmitted with the corresponding phase shifts. Thus, the phases can be shifted so that the transmitted signals are orthogonal at the receivers over the entire sequence duration.

[0049] In a further advantageous embodiment of the method, the procedure can be carried out several times in succession, particularly cyclically. In this way, the monitoring area can be monitored over a longer period. Additionally or alternatively, the results of the individual measurement cycles can be compared, thus improving the validation of the target signals and better resolving ambiguities.

[0050] Advantageously, at least one target signal can be validated over several measurement cycles. Such a method can be referred to as "tracking".

[0051] Furthermore, the technical problem is solved according to the invention in the radar system by the fact that the at least one control and / or evaluation unit has means for carrying out the method according to the invention.

[0052] Advantageously, the means of the control and / or evaluation system can be implemented using software and / or hardware.

[0053] Furthermore, the features and advantages identified in connection with the inventive method and the inventive radar system and their respective advantageous embodiments apply mutatis mutandis to each other and vice versa. The individual features and advantages can, of course, be combined with one another, potentially resulting in further advantageous effects that go beyond the sum of the individual effects. Brief description of the drawings

[0054] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are explained in more detail with reference to the drawing. The person skilled in the art will expediently consider the features disclosed in the drawing, the description, and the claims individually and combine them into meaningful further combinations. The drawing schematically illustrates Figure 1 shows a motor vehicle with a driver assistance system and a MIMO radar system for monitoring a monitoring area in the direction of travel in front of the motor vehicle, wherein the radar system has, by way of example, four transmitters and two receivers; Figure 2 shows a functional representation of the motor vehicle with the radar system and the driver assistance system from the Figure 1 Figure 3 shows an amplitude-time diagram of a first transmitted signal in the form of a chirp, which is transmitted by a first transmitter of the radar system from Figures 1 and 2; Figure 4 shows an amplitude-time diagram of a chirp sequence of chirps of the first transmitted signal, which is transmitted by the first transmitter of the radar system from the Figure 1 and 3 is transmitted; Figure 5 a frequency-time diagram of the chirp sequence from the Figure 4 Figure 6 shows a range Doppler matrix with target signals derived from received signals of respective chirp sequences emitted by the four transmitters of the radar system. Figures 1 and 2transmitted and reflected at a target, are determined, whereby the detected target has no relative velocity with respect to the radar system; Figure 7 the range Doppler matrix from the Figure 6 , where additional target signals from a second target are shown, which has a relative velocity to the radar system.

[0055] In the figures, identical components are labelled with the same reference symbols. embodiment(s) of the invention

[0056] In the Figure 1 Figure 10 shows a motor vehicle 10 in the form of a passenger car in a front view. The motor vehicle 10 has a radar system 12. The radar system 12 is arranged in the front bumper of the motor vehicle 10 by way of example. The radar system 12 can detect a vehicle as shown in the functional diagram of the Figure 2 The indicated monitoring area 14 in the direction of travel 16 in front of the motor vehicle 10 is monitored for objects. Figure 2Two objects, 18a and 18b, are indicated.

[0057] The radar system 12 can also be located elsewhere on the motor vehicle 10 and oriented differently. The objects 18a and 18b can be stationary or moving objects, such as other vehicles, persons, animals, plants, obstacles, road surface irregularities (e.g., potholes or stones), lane markings, traffic signs, open spaces (e.g., parking spaces), precipitation, or the like.

[0058] Radar system 12 is designed as a frequency-modulated continuous wave radar. Frequency-modulated continuous wave radars are also known in technical circles as FMCW (frequency-modulated continuous wave) radars. Radar system 12 can, for example, determine the distance, direction, and speed of objects 18a and 18b relative to the vehicle 10.

[0059] The radar system 12 is connected to a driver assistance system 20. The driver assistance system 20 enables the motor vehicle 10 to be operated autonomously or semi-autonomously.

[0060] Radar system 12 is designed as a so-called MIMO radar system. Radar system 12 comprises, for example, a first transmitter Tx1, a second transmitter Tx2, a third transmitter Tx3, a fourth transmitter Tx4, an electronic control and evaluation unit 22, a first receiver Rx1, and a second receiver Rx2. Transmitters Tx1, Tx2, Tx3, and Tx4 are implemented, for example, with a radar sensor that contains, for instance, a chip with the four integrated transmitters Tx1, Tx2, Tx3, and Tx4. Transmitters Tx1, Tx2, Tx3, and Tx4 are each connected to a separate transmitting antenna. For example, the four transmitting antennas are arranged a few millimeters apart.

[0061] The control and evaluation unit 22 is connected to the driver assistance system 20 via a signal connection. Depending on object information from the radar system 12, the driver assistance system 20 can control / regulate functions of the motor vehicle 10. For the invention, it is not essential whether electrical control and / or evaluation devices, such as the driver assistance system 20, the control and evaluation unit 22, an engine control unit of the motor vehicle 10, or the like, are integrated into one or more components or component groups or are at least partially implemented as decentralized components or component groups.

[0062] The respective transmitting antennas of transmitters Tx1, Tx2, Tx3, and Tx4 are identically constructed. They have identical antenna gains and directional characteristics. Transmitters Tx1, Tx2, Tx3, and Tx4 can transmit signals C1, C2, C3, and C4, respectively, in the form of chirps with constantly changing frequencies, as chirp sequences Cseq, into monitoring area 14. For example, a transmit signal C1, which is sent by the first transmitter Tx1, is shown in the... Figure 3 and the corresponding chirp sequence Cseq in the Figure 4The transmitted signals C1, C2, C3, and C4 are reflected by object 18a and returned as corresponding received signals E1_a, E2_a, E3_a, and E4_a to receivers Rx1 and Rx2. Additionally, the transmitted signals C1, C2, C3, and C4 are reflected by object 18b and returned as corresponding received signals E1_b, E2_b, E3_b, and E4_b to receivers Rx1 and Rx2. Receivers Rx1 and Rx2 convert the received signals E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, and E4_b into a form usable by the control / evaluation unit 22. From the received signals E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b and E4_b, the distance, direction and speed of the objects 18a and 18b relative to the motor vehicle 10 are determined using the control and evaluation unit 22 according to a procedure described below.

[0063] The procedure for determining object information, namely the distances, directions and velocities, of objects 18a and 18b detected by radar system 12, is described below using the following: Figures 3 to 7 An example will be provided.

[0064] In this procedure, the control and evaluation unit 22 controls the transmitters Tx1, Tx2, Tx3, and Tx4 such that the first transmitter Tx1 sends a chirp sequence Cseq consisting of the first transmission signals C1, the second transmitter Tx2 sends a chirp sequence Cseq consisting of the second transmission signals C2, the third transmitter Tx3 sends a chirp sequence Cseq consisting of the third transmission signals C3, and the fourth transmitter Tx4 sends a chirp sequence Cseq consisting of the fourth transmission signals C4 into the monitoring area 14. The respective chirps of the transmission signals C1, C2, C3, and C4 are transmitted simultaneously at the same clock speed.

[0065] The transmitted signals C1, C2, C3, and C4 are generated from the same frequency-modulated continuous wave signal. The second transmitted signal C2, the third transmitted signal C3, and the fourth transmitted signal C4 are encoded using phase modulation relative to the first transmitted signal C1 in such a way that signal orthogonality is achieved between the first transmitted signal C1, the second transmitted signal C2, the third transmitted signal C3, and the third transmitted signal C4.

[0066] In the Figure 3 The first transmitted signal C1 is shown as an example in an amplitude-time diagram. The amplitude As is plotted on the ordinate axis and the time t on the abscissa axis. The amplitude As of the first transmitted signal C1 is normalized to 1 for this example.

[0067] The amplitude-time diagram from the Figure 4Figure 1 shows a chirp sequence Cseq consisting of initial signals C1. For example, a total of 128 such initial signals C1 can be transmitted as a chirp sequence Cseq in a single measurement. The number of signals C1 in a chirp sequence Cseq defines a uniqueness range, which in this example is 128. The successive initial signals C1 of a chirp sequence Cseq each have the same phase, meaning they are each shifted by a phase shift P_Tx1 of 0° relative to their phase. Therefore, the initial signals C1 are transmitted sequentially in a clocked fashion with constant or identical phase.

[0068] In the Figure 5 is a frequency-time diagram for the chirp sequence Cseq of the first transmitted signal C1 from the Figure 4The frequency f is plotted on the ordinate axis and the time t on the abscissa axis. The successive first transmission signals C1 are each shown here as frequency ramps, each shifted by 0° with respect to its phase.

[0069] The phase positions of the second transmitted signals C2 are incremented by a constant phase shift P_Tx2 from one chirp to the next in the corresponding chirp sequence Cseq. The phase positions of the third transmitted signals C3 are incremented by a constant phase shift P_Tx3 from one chirp to the next in the corresponding chirp sequence Cseq. The phase positions of the fourth transmitted signals C4 are incremented by a constant phase shift P_Tx4 from one chirp to the next in the corresponding chirp sequence Cseq. The phase positions of the first transmitted signals C1 are constant from one chirp to the next in the corresponding chirp sequence Cseq, so the corresponding phase shift P_Tx1 = 0.

[0070] The phase shift magnitudes P_Tx2, P_Tx3, and P_Tx4 are different and are defined such that, for all transmitted signals C1, C2, C3, and C4, the absolute differences Diff_P between the respective phase shift magnitudes P_Tx1, P_Tx2, P_Tx3, and P_Tx4 of any two of the transmitted signals C1, C2, C3, and C4 are different. Therefore, the respective absolute differences Diff_P between P_Tx1 and P_Tx2, between P_Tx1 and P_Tx3, between P_Tx1 and P_Tx4, between P_Tx2 and P_Tx3, between P_Tx2 and P_Tx4, and between P_Tx3 and P_Tx4 are different.

[0071] The phase shift values ​​P_Tx1, P_Tx2, P_Tx3, and P_Tx4 are defined as the mathematical product of a base phase shift value P0 and a respective Golomb number GR_Marks of a Golomb ruler with order GR_Order. A Golomb ruler is used whose order GR_Order corresponds to the total number N of transmitters Tx1, Tx2, Tx3, and Tx4. In this embodiment, four transmitters transmit simultaneously, so the Golomb ruler with order GR_Order = 4 is used. The Golomb numbers GR_Marks of the Golomb ruler used are 0, 1, 4, and 6.

[0072] To specify the basic phase shift magnitude P0, the smallest possible step for a phase shift can be set to 360° / Q, where Q is a power of two. For example, Q could be 16 and the basic phase shift magnitude P0 could be set to 22.5°. The basic phase shift magnitude P0 can also be specified in other ways. For example, the basic phase shift magnitude P0 can be chosen such that the smallest phase shift magnitude is smaller than the uniqueness range for the phase shift divided by the length of the Golomb ruler used. The length of the Golomb ruler is the greatest distance between two markings.

[0073] In general, the following applies to the calculation of the phase shift amounts P_Tx from the product of the respective Golomb numbers with the basic phase shift amount P0: P _ Txn = GR _ Marks _ n * P 0

[0074] Here, n is the operating parameter for the corresponding transmitter Tx. For n, n = [1; N], where N is the total number of simultaneously transmitting transmitters Tx.

[0075] In this specific embodiment, the total number of transmitters is N = 4. The basic phase shift magnitude is specified as P0 = 22.5°.

[0076] Accordingly, the phase shift values ​​P_Tx of the four transmitters Tx1, Tx2, Tx3 and Tx4 are: P _ Tx 1 = 0 * 22 , 5 ° = 0 ° P _ Tx 2 = 1 * 22 , 5 ° = 22 , 5 ° P _ Tx 3 = 4 * 22 , 5 ° = 90 ° P _ Tx 4 = 6 * 22 , 5 ° = 135 °

[0077] For all differences Diff_P between the phase shift amounts P_Tx of any two of the transmitters Tx1, Tx2, Tx3 and Tx4, the following different values ​​result: Diff _ P 2 1 = P _ Tx 2 - P _ Tx 1 = 22 , 5 ° Diff _ P 3 1 = P _ Tx 3 − P _ Tx 1 = 90 ° Diff _ P 4 1 = P _ Tx 4 − P _ Tx 1 = 135 ° Diff _ P 3 2 = P _ Tx 3 − P _ Tx 2 = 67 , 5 ° Diff _ P 4 2 = P _ Tx 4 − P _ Tx 2 = 112 , 5 ° Diff _ P 4 3 = P _ Tx 4 − P _ Tx 3 = 45 °

[0078] For the respective chirp sequences Cseq, which are transmitted with the four transmitters Tx1, Tx2, Tx3 and Tx4, the following phase constellation results, where "Tkt" denotes the respective clock of the chirp sequences Cseq and for the sake of clarity only 10 of the clocks are shown as an example: Tkt1 Tkt2 Tkt3 Tkt4 Tkt5 Tkt6 Tkt7 Tkt8 Tkt9 Tkt10 ... Tx1 0° 0° 0° 0° 0° 0° 0° 0° 0° 0° Tx2 0° 22,5° 45° 67,5° 90° 112,5° 135° 157,5° 180° 202,5° Tx3 0° 90° 180° 270° 0° 90° 180° 270° 0° 90° Tx4 0° 135° 270° 45° 180° 315° 90° 225° 0° 135°

[0079] The phases of the transmitted signals C1, C2, C3, and C4 are incremented with each clock cycle by their respective phase shift amounts P_Tx1, P_Tx2, P_Tx3, and P_Tx4, respectively. In the first clock cycle Tkt1, the transmitted signals C1, C2, C3, and C4 each start with a phase of 0°. For example, in the case of the transmitted signal C2 from the second transmitter Tx2, the phase increases in the following clock cycles, i.e., from chirp to chirp, by the phase shift amount P_Tx2, i.e., by 22.5°.

[0080] The receivers Rx1 and Rx2 receive the echoes of the transmitted signals C1, C2, C3 and C4 reflected from object 18a as received signals E1_a, E2_a, E3_a and E4_a and the echoes of the transmitted signals C1, C2, C3 and C4 reflected from object 18b as received signals E1_b, E2_b, E3_b and E4_b and convert them into a form usable by the control and evaluation unit 22.

[0081] The received signals E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b and E4_b are subjected to a single two-dimensional fast Fourier transformation using appropriate means of the control / evaluation unit 22.

[0082] From the result of the two-dimensional discrete Fourier transform, four target signals corresponding to the transmitted signals C1, C2, C3, and C4 are determined for each detected object 18a and 18b. These target signals are ZS1_a, ZS2_a, ZS3_a, and ZS4_a for object 18a and ZS1_b, ZS2_b, ZS3_b, and ZS4_b for object 18b. The number of target signals for an object corresponds to the total number of transmitters Tx1, Tx2, Tx3, and Tx4, which in this case is four. In this phase of the procedure, the eight example target signals are not yet assigned to the respective transmitters Tx1, Tx2, Tx3, and Tx4, but for the sake of clarity, they are already labeled here with the respective reference symbols ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, and ZS4_b. The assignment of the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, and ZS4_b, i.e., their validation, will only take place in a later phase of the procedure.

[0083] In the Figure 6For clarity, the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a are shown as examples only for object 18a in a distance Doppler matrix 24, each indicated by hatching extending to the upper right. Figure 7The target signals ZS1_b, ZS2_b, ZS3_b, and ZS4_b for object 18b are additionally indicated by hatching extending downwards to the right. As explained further below, the target signal ZS4_a for object 18a and the target signal ZS3_b for object 18b fall within the same distance Doppler cell 26 of the distance Doppler matrix 24, which is therefore marked with cross-hatching. In the described embodiment, object 18a does not move relative to the radar system 12. Object 18b does move relative to the radar system 12. Furthermore, in the described embodiment, the target objects of objects 18a and 18b, from which the transmitted signals C1, C2, C3, and C4 are reflected, are located at the same distance from the radar system 12.Object targets within the meaning of the invention are areas of objects in the monitoring area where transmitted signals are reflected in such a way that the corresponding echoes can be detected as received signals by the radar system 12.

[0084] The in the Figures 6 and 7 The distance Doppler matrix 24 shown can also be referred to as a range Doppler matrix. The distance Doppler matrix 24 is composed of a multitude of distance Doppler cells 26. Each distance Doppler cell 26 is characterized by a distance value r, also called range bin, and a Doppler value d, also called Doppler bin. In the Figures 6 and 7 The distance values ​​r are plotted on the abscissa axis and the Doppler values ​​d on the ordinate axis as examples.

[0085] In the present embodiment, the uniqueness range in the Doppler dimension corresponds to the number of transmitted signals of a chirp sequence Cseq and, as already mentioned above, corresponds to 128 distance Doppler cells 26 in the distance Doppler matrix 24. In the Figures 6 and 7 For the sake of clarity, only some of the distance Doppler cells 26 are shown as examples in the form of a grid.

[0086] Since the target objects of objects 18a and 18b are at the same distance from radar system 12, all target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b have the same distance value r, for example r=6.

[0087] As a consequence of the phase configuration described above according to the invention for the transmitted signals C1, C2, C3 and C4, the distances 28 in the Doppler dimension, i.e. the difference between the respective Doppler values ​​d, between adjacent target signals ZS1_a to ZS2_a, ZS2_a to ZS3_a and ZS3_a to ZS4_a, which originate from the object 18a, are as shown in the Figures 6 and 7 shown, differently.

[0088] The target signal ZS1_a has, for example, the distance Doppler coordinates (6, 1). The target signal ZS2_a has, for example, the distance Doppler coordinates (6, 2). The target signal ZS3_a has, for example, the distance Doppler coordinates (6, 5). The target signal ZS4_a has, for example, the distance Doppler coordinates (6, 7). The distance 28 in the Doppler dimension between the target signals ZS1_a and ZS2_a is therefore 1. The distance 28 between target signals ZS2_a and ZS3_a is therefore 3. The distance 28 between target signals ZS3_a and ZS4_a is therefore 2.

[0089] Also as a consequence of the phase constellation described above according to the invention for the transmitted signals C1, C2, C3 and C4, the distances 28 in the Doppler dimension, i.e. the differences between the respective Doppler values ​​d, are between the adjacent target signals ZS1_b and ZS2_b and adjacent target signals ZS3_b and ZS4_b, which originate from the object 18b, as shown in the Figure 7The target signal ZS1_b, for example, has the distance Doppler coordinates (6, 3). The target signal ZS2_b, for example, has the distance Doppler coordinates (6, 4). The target signal ZS3_b, for example, has the distance Doppler coordinates (6, 7). The target signal ZS4_b, for example, has the distance Doppler coordinates (6, 9). Therefore, the distance 28 in the Doppler dimension between the target signals ZS1_b and ZS2_b is 1. The distance 28 between the target signals ZS3_b and ZS4_b is 2. The distance 28 between the adjacent target signals ZS2_b and ZS3_b is 3.

[0090] The phase configuration according to the invention for the transmitted signals C1, C2, C3, and C4 ensures that the target signals ZS1_a, ZS2_a, and ZS4_a, originating from object 18a, and the target signals ZS1_b, ZS2_b, and ZS4_b, originating from object 18b, are each located in different distance Doppler cells 26 and can therefore be distinguished from one another. Only the target signal ZS4_a from object 18a and the target signal ZS3_b from object 18b are located in the same distance Doppler cell 26 with the distance Doppler coordinates (6, 5) in this embodiment.

[0091] In order to validate the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b, these must be assigned to the respective transmitting signals C1, C2, C3 and C4, i.e. to the respective transmitters Tx1, Tx2, Tx3 and Tx4 respectively.

[0092] To assign the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b to the respective transmit signals C1, C2, C3, and C4, a power window PW is determined for each distance Doppler cell 26 from the distance Doppler matrix 24. A power window matrix (not shown in the figures) is then derived from the power windows PW. From this power window matrix, power window target signals are determined that correspond to the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b from the distance Doppler matrix 24.

[0093] The power windows PW are determined for each distance Doppler cell 26 according to the following formula: PW r d = ∑ m = 0 GR _ Order − 1 SPEC r mod GR _ Marks m + d , D

[0094] Here, GR_Marks is the Golomb number of the Golomb ruler used, with order GR_Order, which in the following embodiment is 4. The parameter for the distance values ​​of the distance Doppler cells 26 is the distance value r from the range [0; R], where R is the number of distance Doppler cells 26 of the distance Doppler matrix 24 in the distance dimension. D is the number of distance Doppler cells 26 of the distance Doppler matrix 24 in the Doppler dimension. The parameter for the distance Doppler cells 26 in the Doppler dimension is the Doppler value d from the range [0; D].

[0095] The following equations assign the correct complex values ​​from the original two-dimensional Fourier transform, namely the distance Doppler matrix 24, to the corresponding transmitters Tx1, Tx2, Tx3 and Tx4: 2 D − FFT TX 1 = 2 D − FFT D m + GR _ Marks 0 2 D − FFT TX 2 = 2 D − FFT D m + GR _ Marks 1 ... 2 D − FFT TXN = 2 D − FFT D m + GR _ Marks N − 1

[0096] Here, N is the number of transmitters, which in the illustrated embodiment is 4. TX1 to TXN, namely Tx1 to Tx4, are the designations for the transmitters. Rm is the index for the distance values ​​of the distance Doppler cells for a detected target in the power matrix. Dm is the index for the Doppler values ​​of the distance Doppler cells for a detected target in the power matrix.

[0097] Optionally, an additional check can be performed in a distance cell Rm if there are other neighboring detections to the Doppler cell Dm that have colliding peaks in the distance Doppler matrix 24. For the search, the detections in Doppler cells in the range [mod(Dm + GR_length, D), mod(Dm - GR_length, D)] can be checked. If a detection is found in this range, a further check can be performed to find possible collisions in the distance Doppler matrix 24. These colliding Doppler cells can be marked, and this information can be used for MIMO signal processing.

[0098] Since the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b have the same distance value in the distance Doppler matrix 24, the correct distance can be derived from each of them.

[0099] Since the first transmitted signal C1 is not encoded and its phase is shifted, the Doppler value d corresponding to the first target signal ZS1_a can be considered the correct Doppler value, and the correct relative velocity of object 18a can be derived from it. Similarly, the correct relative velocity of object 18b can be derived from the Doppler value d of the first target signal ZS1_b.

[0100] After appropriate correction of the phase constellation of the transmitted signals C1, C2, C3, and C4, the correct relative velocity can also be derived from the other unambiguous and validated target signals ZS2_a, ZS3_a, ZS2_b, and ZS4_b. The target signals ZS4_a and ZS3_b fall within the same distance Doppler cell 26 and therefore cannot be unambiguously assigned and validated to the transmitted signals C1, C2, C3, and C4 and the objects 18a and 18b.

[0101] The phase values ​​belonging to the unique and validated target signals ZS1_a, ZS2_a, ZS3_a, ZS1_b, ZS2_b, ZS4_b, and the phase values ​​belonging to the transmit signals C1, C2, C3 and C4 can be determined independently of each other due to the shift and used for a phase-based angle measurement of the azimuth and elevation of objects 18a and 18b with respect to radar system 12.

[0102] From the validated target signals ZS1_a, ZS2_a, ZS3_a, ZS1_b, ZS2_b, ZS4_b, the respective relative speed, the respective distance and direction and thus the position of the objects 18a and 18b with respect to the radar system 12 is determined as object information.

[0103] The procedure is carried out cyclically, so that the monitoring area 14 can be continuously monitored for objects 18a and 18b and corresponding detected objects 18a and 18b can be tracked.

[0104] The invention can also be used in radar systems 12 with more or less than four transmitters Tx1, Tx2, Tx3 and Tx4, for example 12 or more transmitters, and / or more or less than two receivers Rx1 and Rx2 and corresponding transmitting signals C1, C2, C3 and C4 or received signals E1, E2, E3 and E4.

Claims

1. Method for determining at least one piece of object information about at least one object (18a, 18b) sensed with a radar system (12), in which - transmission signals (C1, C2, C3, C4) in the form of chirps are each transmitted in chirp sequences (Cseq) into a monitoring region (14) of the radar system (12) with at least four transmitters (Tx1, Tx2, Tx3, Tx4), - echoes, which are reflected at the at least one object (18a, 18b), of the transmission signals (C1, C2, C3, C4) are received as received signals (E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, E4_b) with at least one receiver (Rx1, Rx2), and if necessary are converted into a form which can be used by an electronic control and / or evaluation device (22), - the received signals (E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, E4_b) are subjected to at least one two-dimensional discrete Fourier transformation, - from the result of the at least one two-dimensional discrete Fourier transformation, at least one target signal (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) is determined, - from the at least one target signal (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) at least one piece of object information is determined, - wherein at the transmitter end at least one first transmission signal (C1) and at least three other transmission signals (C2, C3, C4) are generated from a frequency-modulated continuous wave signal and each is transmitted simultaneously into the monitoring region (14) of the radar system (12) with a separate transmitter (Tx1, Tx2, Tx3, Tx4), - wherein the at least three other transmission signals (C2, C3, C4) are each encoded by means of a phase modulation with respect to the at least one first transmission signal (C1), - wherein the respective phase positions of the at least three other transmission signals (C2, C3, C4) are each incremented or decremented by a constant phase shift amount from one chirp to the next, - wherein different phase shift amounts are used for the at least three other transmission signals (C2, C3, C4), characterized in that the respective phase shift amounts for the at least three other transmission signals (C2, C3, C4) are specified in such a way that for at least four of the transmission signals (C1, C2, C3, C4), including the at least one first transmission signal (C1), the absolute differences between the phase shift amounts of any two of the at least four transmission signals (C1, C2, C3, C4) are different.

2. Method according to Claim 1, characterized in that the phase position of the at least one first transmission signal (C1) is held constant from one chirp to the next and a corresponding phase shift amount equal to zero is used.

3. Method according to Claim 1 or 2, characterized in that the at least three other transmission signals (C2, C3, C4) are encoded in such a way that of all transmission signals (C1, C2, C3, C4), including the at least one first transmission signal (C1), the absolute differences between the phase shift amounts of any two of the at least four transmission signals (C1, C2, C3, C4) are different.

4. Method according to any of the previous claims, characterized in that the phase shift amounts of the transmission signals (C1, C2, C3, C4) are specified in such a way that there are no two phase shift amounts among the phase shift amounts for which the absolute difference equals the absolute difference of at least one of the two phase shift amounts for a phase shift amount of another transmission signal (C1, C2, C3, C4).

5. Method according to any of the previous claims, characterized in that a phase shift amount of at least one of the at least three other transmission signals (C2, C3, C4) is defined as the mathematical product of a phase shift basic amount and a Golomb number of a Golomb ruler assigned to said transmission signal (C2, C3, C4).

6. Method according to Claim 5, characterized in that the Golomb ruler is used, the order of which is less than or equal to the number of transmission signals (C1, C2, C3, C4), including the at least one first transmission signal (C1), to which different phase shift amounts are to be assigned.

7. Method according to any of the previous claims, characterized in that at the receiver end, from the result of the at least one two-dimensional discrete Fourier transformation, a plurality of target signals (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) is determined in a range Doppler matrix (24).

8. Method according to claim 7, characterized in that at the receiver end, a respective power window is determined for each range Doppler cell (26) from the range Doppler matrix (24), a power window matrix is determined from the power windows and the power window matrix is used to assign a plurality of target signals (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) to respective transmission signals (C1, C2, C3, C4).

9. Method according to any of the previous claims, characterized in that from at least one target signal (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) at least one piece of object information is determined.

10. Method according to any of the previous claims, characterized in that from at least one target signal (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) at least one piece of object information is determined in the form of a speed and / or a position, in particular a distance and / or a direction, of the at least one object (18a, 18b) relative to the radar system (12).

11. Method according to any of the previous claims, characterized in that a single two-dimensional discrete Fourier transformation, in particular a single two-dimensional fast Fourier transformation, is performed.

12. Method according to any of the previous claims, characterized in that the at least three other transmission signals (C2, C3, C4) are encoded at the transmitter end by means of binary or higher-order phase-shift keying.

13. Method according to any of the previous claims, characterized in that the method is carried out multiple times in succession, in particular cyclically.

14. Radar system (12) for determining at least one piece of object information about at least one object (18a, 18b), - having at least four transmitters (Tx1, Tx2, Tx3, Tx4) for transmitting transmission signals (C1, C2, C3, C4) in the form of chirps in chirp sequences (Cseq) into a monitoring region (14), - having at least one receiver (Rx1, Rx2) for receiving echoes, which are reflected at the at least one object (18a, 18b), of the transmission signals (C1, C2, C3, C4) as received signals (E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, E4_b) and - having at least one control and / or evaluation device (22) for controlling the at least four transmitters (Tx1, Tx2, Tx3, Tx4) and the at least one receiver (Rx1, Rx2) and for evaluating the received signals (E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, E4_b), characterized in that the at least one control and / or evaluation device (22) has means for carrying out the method according to one of the previous claims.