Method and radar system for determining at least one object information item regarding at least one object sensed by means of a radar system

Abstract

The present invention relates to a method for determining at least one object information about at least one object sensed by means of a radar system and to a radar system. According to the method, in a monitoring area of the radar system, transmission signals in the form of chirp pulses are transmitted by at least three transmitters in a chirp pulse sequence respectively. The echoes of the transmission signals reflected at at least one object are received as received signals by means of at least one receiver and, if necessary, brought into a form that can be used 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 (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) 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 (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b). On the transmitter side, at least one first transmission signal and at least two other transmission signals are generated from a frequency-modulated continuous-wave signal and are respectively transmitted simultaneously into the monitoring area of the radar system by means of separate transmitters. The at least two other transmission signals are respectively encoded by a phase modulation related to at least one first transmission signal. The respective phase positions of the at least two other transmission signals are increased or decreased by a constant phase shift amount from one chirp pulse to the next chirp pulse. Different phase shift amounts are used for the at least two other transmission signals. The respective phase shift amounts of the at least two other transmission signals are specified such that, for at least three transmission signals including at least one first transmission signal, the amount difference between the phase shift amounts of two of the at least three transmission signals is different.

Description

Technical Field

[0001] The present invention relates to a method for determining at least one object information of at least one object sensed by a radar system, wherein,

[0002] - At least three transmitters transmit a transmission signal in the form of a chirp pulse as a chirp pulse sequence into a monitoring area of the radar system,

[0003] - An echo of the transmission signal reflected at at least one object is received as a received signal by at least one receiver and, if necessary, converted into a form usable by an electronic control and / or evaluation device,

[0004] - The received signal undergoes at least one two-dimensional discrete Fourier transform,

[0005] - At least one target signal is determined from the result of at least one two-dimensional discrete Fourier transform,

[0006] - At least one object information is determined from at least one target signal,

[0007] - wherein, at the transmitter side, at least one first transmission signal and at least two other transmission signals are generated from a frequency-modulated continuous wave signal, and each transmission signal is simultaneously transmitted into the monitoring area of the radar system using a separate transmitter,

[0008] - wherein at least two other transmission signals are respectively encoded by phase modulation relative to at least one first transmission signal,

[0009] - wherein the respective phase positions of at least two other transmission signals increase or decrease by a constant phase shift amount from one chirp pulse to the next chirp pulse,

[0010] - wherein different phase shift amounts are used for at least two other transmission signals.

[0011] Furthermore, the present invention relates to a radar system for determining at least one object information about at least one object,

[0012] - having at least one transmitter for transmitting chirp pulses into a monitoring area as a chirp pulse sequence,

[0013] - having at least one receiver for receiving an echo of the transmission signal reflected at at least one object as a received signal, and

[0014] - having at least one control and / or evaluation device for controlling at least one transmitter and at least one receiver and for evaluating the received signal,

[0015] characterized in that,

[0016] At least one control and / or evaluation device has means for carrying out the method according to any one of the preceding claims. Background Art

[0017] Document WO2018 / 137836 discloses a method for determining at least one piece of object information regarding at least one object sensed by a radar system, in particular a radar system of a vehicle. In this method, at least one transmitter is used to transmit a transmission signal into the monitoring area of the radar system. The echo of the transmission signal reflected at at least one object is received as a received signal by at least one receiver and, if necessary, converted into a form that can be used by an electronic control and / or evaluation device. The received signal is subjected to at least one two-dimensional discrete Fourier transform. At least one target signal is determined from the result of at least one two-dimensional discrete Fourier transform. At least one piece of object information is determined from at least one target signal. At the transmitter side, at least one first transmission signal and at least one second transmission signal are generated from a frequency-modulated continuous-wave signal, wherein at least one second transmission signal is encoded by means of a phase modulation relative to at least one first transmission signal, wherein the phase position of at least one second transmission signal increases or decreases by a constant amount from one frequency ramp to the next frequency ramp. In the phase modulation of a plurality of second transmission signals, different phase increments can be used for the respective second transmission signals. At least one first transmission signal is transmitted by at least one first transmitter, and at least one second transmission signal is transmitted by at least one second transmitter simultaneously into the monitoring area of the radar system. Using a control and evaluation device, the transmitters can be controlled such that the first transmitter transmits the first transmission signal, the second transmitter transmits the second transmission signal, and the third transmitter transmits the third transmission signal simultaneously into the monitoring area.

[0018] The present invention is based on the object of configuring a method and a radar system of the above type, in which any ambiguity regarding object information, in particular the distance, speed and / or direction of at least one object relative to the radar system, can be resolved more simply and / or more reliably. Summary of the Invention

[0019] According to the invention, this object is achieved by the fact that the respective phase shift amounts of at least two other transmission signals are specified such that for at least three transmission signals including at least one first transmission signal, the absolute difference between the phase shift amounts of any two of the at least three transmission signals is different.

[0020] According to the present invention, at least one target signal is assigned to a corresponding transmission signal and thus verified. By phase modulating the transmission signal according to the present invention, the corresponding target signals generated from different transmitters are offset relative to each other, particularly in the Doppler dimension, thus forming a unique overall pattern. Therefore, significantly more than three transmitters can be used simultaneously depending on the available modulation levels of the phase modulation. In this case, the transmission signals are completely orthogonal at the output of a two-dimensional Fourier transform, particularly an FFT. The method can be extended to a corresponding number of simultaneously active transmitters using higher-order modulation methods.

[0021] With the present invention, a MIMO radar with a chirp signal can be implemented. The MIMO radar can be operated using a Doppler multiplexing method. By different constant increments of the phase positions of the signals transmitted at the individual transmitters, signals that are shifted along the Doppler dimension can be generated after performing a two-dimensional discrete Fourier transform at the receiver end, and thus these signals are orthogonal.

[0022] As is well known, a signal whose frequency varies with time is called a chirp. The frequency response of a chirp can be represented as a frequency ramp.

[0023] According to the present invention, the corresponding phase shift amounts of at least two other transmission signals are specified such that for at least three transmission signals including at least one first transmission signal, the absolute difference between the phase shift amounts of any two of the at least three transmission signals is different. This reduces the occurrence of interference effects between the target signals, which may occur from different targets at the same distance with different speeds, particularly in range-Doppler cells with the same range value. Without the present invention, if the speeds of two target signals of targets with different speeds in the same range cell happen to differ by an integer multiple of the selected distance between the transmitters in the Doppler dimension, interference between them may occur. With the aid of the present invention, interference between target signals from multiple targets with different speeds can also be avoided for multiple transmitters.

[0024] According to the present invention, at the receiver end, after Fourier transform, due to different phase shift amounts at the transmitter end, different Doppler offsets are achieved in the range-Doppler matrix for different transmitters. The Doppler offset of a transmitter is given by a single fraction of the uniqueness range in the Doppler dimension. The uniqueness range can be characterized by a specified number of range-Doppler cells in the Doppler dimension in the range-Doppler matrix. Therefore, the uniqueness range at the transmitter end can correspond to a 360° phase shift. The phase shift amounts of different transmitters can be specified as separate fractions of 360°, respectively.

[0025] At least one second transmission signal can be encoded by phase modulation relative to at least one first transmission signal such that at least temporary signal orthogonality is created between the transmission signals.

[0026] At least three transmitters are activated simultaneously. In this way, the determination of object information can be accelerated.

[0027] Due to the phase modulation of at least two other transmission signals using different amounts of phase shift, at least two other transmission signals can be orthogonal to each other and orthogonal to at least one first transmission signal.

[0028] The reflected echo is received at the transmitting end as a received signal and, if necessary, converted into a form that can be used by an electronic control and / or evaluation device. If the transmission signal and the generated echo have signal types that cannot be directly processed by the corresponding electronic control and / or evaluation device, the received signal is converted into an electronically usable form. Otherwise, no corresponding adaptation, in particular conversion, of the received signal is required. In this way, the received signal can be directly processed by the electronic control and / or evaluation device or, if appropriate, after the corresponding adaptation.

[0029] The method can be advantageously implemented by means of at least one device using a software and / or hardware solution, in particular by a control and / or evaluation device.

[0030] The radar system can advantageously use fast frequency modulation. Multiple chirp pulses are continuously transmitted as a sequence.

[0031] The phase modulation can advantageously be performed at the clock rate of the chirp pulse (chirp pulse clock rate). In this way, the required frequency of the code sequence as well as the required signal bandwidth can be kept correspondingly low.

[0032] From the result of at least one two-dimensional discrete Fourier transform, multiple target signals can be determined, and the number of target signals for each physically present target corresponds at most to the total number of the first and two other transmission signals. A physically present target can be part of a detected object. The target signal can also be referred to as a radar target.

[0033] The present invention can be used in the radar system of a vehicle, in particular a motor vehicle. The present invention can be advantageously used for land-based vehicles, in particular cars, trucks, buses, motorcycles, etc., airplanes and / or ships. The present invention can also be used for vehicles capable of autonomous or at least partially autonomous operation. However, the present invention is not limited to vehicles. It can also be used for a radar system operating in a stationary manner.

[0034] The radar system can advantageously be connected to at least one electronic control device of a vehicle, in particular a driver assistance system and / or a chassis control system and / or a driver information device and / or a parking assistance system and / or gesture recognition, etc., or can be part of such a device or system. The vehicle can operate autonomously or partially autonomously in this way.

[0035] The radar sensor can be used to detect standing or moving objects, in particular vehicles, persons, animals, plants, obstacles, road unevenness, in particular potholes or rocks, road boundaries, traffic signs, free space, in particular free parking spaces, or precipitation, etc.

[0036] In an advantageous configuration of the method, the phase position of at least one first transmission signal remains constant from one chirp pulse to the next chirp pulse, and a corresponding phase shift amount equal to zero is used. In this way, object information can be directly derived from the target signal, which can be assigned to at least one first transmission signal.

[0037] In another advantageous configuration of the method, at least two other transmission signals are encoded such that in all transmission signals including at least one first transmission signal, the absolute difference between any two of at least three transmission signals is different. In this way, the number of interfering target signals can be further reduced.

[0038] In another advantageous configuration of the method, the phase shift amounts of the transmission signals can be specified such that the absolute difference between no two phase shift amounts is equal to the absolute difference of at least one of two phase shift amounts of another transmission signal. In this way, the number of interfering target signals can be minimized.

[0039] In another advantageous configuration of the method, the phase shift amount of at least one of at least two other transmission signals can be defined as the mathematical product of a basic phase shift amount and a Golomb number of a Golomb ruler assigned to the transmission signal. In this way, the effort required to determine a suitable phase shift amount can be reduced.

[0040] As is well known, in number theory, a Golomb ruler is a ruler in which no two marks are at equal distances from each other at integer positions. Golomb rulers are classified by order and length. The order of a Golomb ruler is defined by the number of marks, and the length is defined by the maximum distance between two marks.

[0041] The advantage of the irregular arrangement of target signals in the Doppler dimension increases with the number of transmitters used simultaneously. As the number of transmitters increases, the structure of the Golomb ruler becomes more complex. Up to the maximum order of available Golomb rulers, for any order there exists at least one suitable Golomb ruler and thus a corresponding number of transmitters.

[0042] In the case of a high-resolution radar system (HD radar) with multiple simultaneously active transmitters, the present invention minimizes the overlap of target signals of all possible constellations consisting of multiple targets. Most of the target signals are not interfered with. In this way, the interference from multiple target signals can be reliably minimized.

[0043] For an HD radar, multiple transmitters, especially more than 12 transmitters, can transmit their respective transmission signals. Multiple, especially 128 or 256 range-Doppler cells in the Doppler dimension can define the uniqueness range of the Doppler dimension. Without the method according to the present invention, the greater the number of possible interferences of the target signals, the more transmitters are used simultaneously. For example, when 12 simultaneously active transmitters are used, without the present invention, up to 11 out of 12 transmission signals overlap in the range-Doppler matrix. Using the method according to the present invention, a maximum of one transmission signal in the range-Doppler matrix overlaps. The remaining 11 transmission signals remain non-interfered with.

[0044] The minimum phase shift amount can be defined as less than the uniqueness range of the phase shift divided by the length of the Golomb ruler. The length of the Golomb ruler is the maximum distance between two marks. It is advantageous to define the minimum possible step size of the phase shift as 360° / Q, where Q is a power of 2. In this way, all target signals conform to the corresponding range-Doppler matrix of the uniqueness range with the same Doppler dimension.

[0045] In another advantageous configuration of the method, a Golomb ruler can be used, the order of which is less than or equal to the number of transmission signals to which different phase shift amounts will be assigned, including at least one first transmission signal. If the order of the Golomb ruler corresponds to the number of transmission signals, the number of possible interferences from multiple target signals at the receiver side can be minimized.

[0046] If the order of the Golomb ruler is less than the number of transmission signals, the Golomb ruler can also be used when the number of transmission signals is greater than the maximum order currently available for the Golomb ruler.

[0047] The currently known largest Golomb ruler has 27 orders. It is expected that Golomb rulers with orders greater than 27 will be determined in the future. Therefore, according to the present invention, it will be possible in the future to use Golomb rulers to determine phase shift amounts for an increasing number of transmitters that can simultaneously transmit an increasing number of transmission signals.

[0048] In an advantageous configuration of the method, multiple target signals in the range-Doppler matrix can be determined at the receiver side from the result of at least one two-dimensional discrete Fourier transform.

[0049] It is advantageous to note that the number of target signals for each physically present target can be at most equal to the total number of the first and other transmitted signals in one cycle of the chirp pulse sequence.

[0050] In another advantageous embodiment, at the receiver side, a corresponding power window can be determined for each range-Doppler cell based on the range-Doppler matrix, a power window matrix can be determined based on the power window, and the power window matrix can be used to assign a plurality of target signals to the corresponding transmitted signals. In this way, the target signals can be verified.

[0051] For a range-Doppler cell, the corresponding power window PW can be determined by the following formula:

[0052]

[0053] where GR_Marks is the Golomb number of the Golomb ruler of order GR_Order. The order GR_Order corresponds to the number of transmitters used or the number of different transmitted signals. The range value r of the range-Doppler cell ranges from [0; R], where R is the number of range-Doppler cells of the range-Doppler matrix in the range dimension. The Doppler value d of the range-Doppler cell in the Doppler dimension ranges from [0; D], where D is the number of range-Doppler cells of the range-Doppler matrix in the Doppler dimension.

[0054] The following equations can be used to assign the correct complex values to the corresponding transmitters according to the original two-dimensional Fourier transform:

[0055] 2D-FFT TX1 = 2D-FFT[D m + GR_Marks[0]]

[0056] 2D-FFT TX2 = 2D-FFT[D m + GR_Marks[1]]

[0057] …

[0058] 2D-FFT TXN = 2D-FFT[D m + GR_Marks[N - 1]]

[0059] Here, N is the number of transmitters. TX1 to TXN are the identifiers of the transmitters. R m is the index of the cell of the detected target in the power matrix in the range dimension. D m is the index of the cell of the detected target in the power matrix in the Doppler dimension.

[0060] Optionally, if there are other detections adjacent to cell D in the Doppler dimension that have conflicting peaks in the range-Doppler matrix, additional checks can be performed in the same cell R in the range dimension m For the search, detections can be checked in the cells of the Doppler dimension that are within the range [mod(D m +GR_length, D), mod(D m -GR_length, D)]. If there is a detection within this range, further verification can be performed to find possible collisions in the range-Doppler matrix. These collision cells in the Doppler dimension can be marked, and this information can be used for signal processing of the MIMO radar. m In another advantageous configuration of the method, at least one item of object information can be determined from at least one target signal. In this way, the object information can be used to describe the monitored area.

[0061] At least one item of object information can advantageously be determined from at least one verified target signal. A verified target signal is a target signal that can be uniquely assigned to the transmitted signal.

[0062] In another advantageous refinement of the method, at least one item of object information can be determined from at least one target signal in the form of at least one object's velocity and / or position relative to the radar system, in particular the range and / or direction. In this way, the radar system can be used to obtain information about at least one object that is particularly meaningful for controlling the driving functions of a vehicle.

[0063] In another advantageous refinement of the method, a single two-dimensional discrete Fourier transform, in particular a single two-dimensional fast Fourier transform, is performed. In this way, the information from at least one first transmitted signal and from at least two other transmitted signals can be utilized by means of only a single two-dimensional, in particular fast, Fourier transform. Thus, the method can be performed more efficiently.

[0064] In another advantageous configuration of the method, at least two other transmitted signals can be encoded at the transmitter side by binary or higher-order phase shift keying. In this way, signal orthogonality can be generated between the transmitted signals.

[0065] The encoding of at least two other transmitted signals can advantageously occur at the frequency of a chirp pulse sequence. In this way, continuous chirp pulses with a linear frequency ramp can optionally be transmitted at corresponding phase positions. Thus, the phase can be shift-keyed such that when considering the entire sequence length, the transmitted signals at the receiver are orthogonal.

[0066]

[0067] ​In a further advantageous configuration of the method, the method can be carried out several times in succession, in particular in a loop. In this way, the monitoring area can be monitored over a relatively long period of time. Additionally or alternatively, the results of the individual measurement cycles can be compared with each other, so that the verification of the target signal can be improved and ambiguities can be better resolved.

[0068] At least one target signal can be advantageously verified within multiple measurement cycles. This method can be referred to as "tracking".

[0069] Furthermore, according to the invention, the technical object of having at least one control and / or evaluation unit with means for carrying out the method according to the invention is solved by a radar system.

[0070] The means of the control and evaluation device can be advantageously implemented by software and / or hardware solutions.

[0071] Furthermore, the features and advantages presented in connection with the method according to the invention and the radar system according to the invention and their respective advantageous configurations apply in a corresponding manner, and vice versa. It goes without saying that the individual features and advantages can be combined with each other, whereby further advantageous effects can be established that exceed the sum of the individual effects. Description of the Drawings

[0072] From the following description, other advantages, features and details of the invention will become apparent, in which exemplary embodiments of the invention are explained in more detail with reference to the drawings. Those skilled in the art will also conveniently consider the features disclosed separately in the drawings, the description and the claims and combine them to form further meaningful combinations. Schematically, in the drawings:

[0073] Figure 1 A motor vehicle equipped with a driver assistance system and a MIMO radar system for monitoring a monitoring area in front of the driving direction of the motor vehicle is shown. As an example, the radar system has four transmitters and two receivers;

[0074] Figure 2 Shows a motor vehicle having Figure 1 the radar system and the functional diagram of the driver assistance system in;

[0075] Figure 3 Shows the amplitude-time diagram of a first transmission signal in the form of a chirp pulse, which signal is transmitted by the first transmitter of the Figure 1 and 2 radar system;

[0076] Figure 4 Shows the amplitude-time diagram of a chirp pulse sequence composed of the chirp pulses of the first transmission signal, which first transmission signal is transmitted by the Figure 1 andFigure 3 transmitted by the first transmitter of the radar system;

[0077] Figure 5 shows a frequency - time diagram of a chirp pulse sequence from Figure 4 ;

[0078] Figure 6 shows a range - Doppler matrix with target signals, which are determined from the signals of the received individual chirp pulse sequences, and the chirp pulse sequences are transmitted by Figure 1 and Figure 2 the four transmitters of the radar system and reflected at the target, where the detected target has no relative velocity with respect to the radar system;

[0079] Figure 7 shows a range - Doppler matrix from Figure 6 ; here, target signals from a second target are also shown, and the second target has a relative velocity with respect to the radar system.

[0080] In the figures, the same components have the same reference numerals. Detailed Description

[0081] Figure 1 shows a front view of a motor vehicle 10 in the form of a passenger car. The motor vehicle 10 has a radar system 12. The radar system 12 is arranged, for example, in the front fender of the motor vehicle 10. The radar system 12 can be used to monitor objects in the monitoring area 14 shown in the functional diagram in the Figure 2 travel direction 16 in front of the motor vehicle 10. In the Figure 2 , two objects 18a and 18b are indicated.

[0082] The radar system 12 can also be arranged and oriented differently at another position on the motor vehicle 10. The objects 18a and 18b can be standing or moving objects, such as other vehicles, people, animals, plants, obstacles, road unevenness, such as potholes or rocks, road boundaries, traffic signs, free space, such as parking spaces, precipitation, etc.

[0083] The radar system 12 is configured as a frequency - modulated continuous - wave radar. In the expert community, a frequency - modulated continuous - wave radar system is also referred to as an FMCW (Frequency - Modulated Continuous - Wave) radar system. The radar system 12 can be used, for example, to determine the respective distances, respective directions, and respective velocities of the objects 18a and 18b relative to the motor vehicle 10.

[0084] The radar system 12 is connected to a driver assistance system 20. With the help of the driver assistance system 20, the motor vehicle 10 can operate autonomously or semi - autonomously.

[0085] The radar system 12 is configured as a so-called MIMO radar system. The radar system 12 includes, for example, a first transmitter Tx1, a second transmitter Tx2, a third transmitter Tx3, a fourth transmitter Tx4, an electronic control and evaluation device 22, a first receiver Rx1, and a second receiver Rx2. The transmitters Tx1, Tx2, Tx3, and Tx4 are implemented, for example, by radar sensors that include, for example, a chip with four integrated transmitters Tx1, Tx2, Tx3, and Tx4. The transmitters Tx1, Tx2, Tx3, and Tx4 are each connected to a separate transmit antenna. For example, the four transmit antennas here are arranged at a distance of a few millimeters.

[0086] The control and evaluation device 22 has a signal transmission connection to the driver assistance system 20. The driver assistance system 20 can be used to perform open-loop / closed-loop control of the functions of the motor vehicle 10 independently of the object information of the radar system 12. For the present invention, it is not important whether the electrical control and / or evaluation device, such as the driver assistance system device 20, the control and evaluation device 22, the engine control device of the motor vehicle 10, etc., is integrated into one or more components or assemblies or is at least partially implemented as decentralized components or assemblies.

[0087] The respective transmit antennas of the transmitters Tx1, Tx2, Tx3, and Tx4 have, for example, the same design. They have the same antenna gain and directional characteristics. The transmitters Tx1, Tx2, Tx3, and Tx4 can be used to transmit the respective transmission signals C1, C2, C3, and C4, respectively, as linear frequency modulation pulse sequences Cseq with a constantly varying frequency into the monitoring area 14. As an example, the transmission signal C1 transmitted by the first transmitter Tx1 is shown in Figure 3 and the corresponding linear frequency modulation pulse sequence Cseq is shown in Figure 4 The transmission signals C1, C2, C3, and C4 are reflected at the object 18a and are sent back to the receivers Rx1 and Rx2 as the respective received signals E1_a, E2_a, E3_a, and E4_a. In addition, the transmission signals C1, C2, C3, and C4 are reflected at the object 18b and are sent back to the receivers Rx1 and Rx2 as the respective received signals E1_b, E2_b, E3_b, and E4_b. By means of the receivers Rx1 and Rx2, the received signals E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, and E4_b are converted into a form that can be used by the control / evaluation device 22. According to another method described below, the control and evaluation device 22 is used to determine the range, direction, and speed of the objects 18a and 18b relative to the motor vehicle 10 from the received signals E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, and E4_b.

[0088] The following is referred toFigures 3 to 7 An example is given to illustrate a method for determining various pieces of object information of objects 18a and 18b sensed by the radar system 12, namely range, direction, and velocity.

[0089] In this method, transmitters Tx1, Tx2, Tx3, and Tx4 are controlled by the control and evaluation device 22 such that the first transmitter Tx1 transmits a chirp pulse sequence Cseq of the first transmission signal C1, the second transmitter Tx2 transmits a chirp pulse sequence Cseq of the second transmission signal C2, the third transmitter Tx3 transmits a chirp pulse sequence Cseq of the third transmission signal C3, and the fourth transmitter Tx4 transmits a chirp pulse sequence Cseq of the fourth transmission signal C4 into the monitoring area 14. The respective chirp pulses of the transmission signals C1, C2, C3, and C4 are transmitted simultaneously at the same clock rate.

[0090] For example, the transmission signals C1, C2, C3, and C4 are generated from the same frequency-modulated continuous-wave signal. The second transmission signal C2, the third transmission signal C3, and the fourth transmission signal C4 are encoded by phase modulation relative to the first transmission signal C1 such that signal orthogonality is achieved among the first transmission signal C1, the second transmission signal C2, the third transmission signal C3, and the fourth transmission signal C4.

[0091] Figure 3 An example of the first transmission signal C1 is shown in an amplitude-time diagram. The amplitude A s is plotted on the vertical axis, and the time t is plotted on the horizontal axis. For example, the amplitude A of the first transmission signal C1 s is normalized to 1.

[0092] Figure 4 The amplitude-time diagram of... shows the chirp pulse sequence Cseq of the first transmission signal C1. For example, during the measurement, a total of 128 such first transmission signals C1 can be transmitted as the chirp pulse sequence Cseq. The number of transmission signals C1 in the chirp pulse sequence Cseq defines the uniqueness range, which is 128 in this example. Each consecutive first transmission signal C1 in the chirp pulse sequence Cseq has the same phase position, that is, each has a phase shift amount P_Tx1 of 0° relative to their phases. In summary, the first transmission signal C1 is thus transmitted cyclically with a constant or the same phase or phase position.

[0093] Figure 5 shows the frequency-time diagram of the chirp pulse sequence Cseq of the first transmission signal C1 from... Figure 4 The frequency f is plotted on the vertical axis, and the time t is plotted on the horizontal axis. The consecutive first transmission signals C1 are here each shown as a frequency ramp, which is phase-shifted by 0° relative to their phases.

[0094] In the corresponding chirp pulse sequence Cseq, from one chirp pulse to the next chirp pulse, the phase position of the second transmission signal C2 increases by a constant phase shift amount P_Tx2 respectively. In the corresponding chirp pulse sequence Cseq, from one chirp pulse to the next chirp pulse, the phase position of the third transmission signal C3 increases by a constant phase shift amount P_Tx3 respectively. In the corresponding chirp pulse sequence Cseq, from one chirp pulse to the next chirp pulse, the phase of the fourth transmission signal C4 increases by a constant phase shift amount P_Tx4 respectively. In the corresponding chirp pulse sequence Cseq, the phase of the first transmission signal C1 is constant from one chirp pulse to the next chirp pulse, such that the corresponding phase shift amount P_Tx1 = 0.

[0095] The phase shift amounts P_Tx2, P_Tx3, and P_Tx4 are different and are specified such that in all the transmission signals C1, C2, C3, and C4, the absolute difference Diff_P between the corresponding phase shift amounts P_Tx1, P_Tx2, P_Tx3, and P_Tx4 of any two of the transmission signals C1, C2, C3, and C4 is different. Therefore, the corresponding 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.

[0096] The phase shift amounts P_Tx1, P_Tx2, P_Tx3, and P_Tx4 are specified as the mathematical products of the corresponding Golomb numbers GR_Marks of a Golomb ruler of order GR_Order and the phase shift base value P0. A Golomb ruler is used, and its order GR_Order corresponds to the total number N of transmitters Tx1, Tx2, Tx3, and Tx4. In this exemplary embodiment, four transmitters transmit simultaneously, so a Golomb ruler of order GR_Order = 4 is used. The Golomb numbers GR_Marks of the Golomb ruler used are 0, 1, 4, and 6.

[0097] For example, for the specification of the phase shift base value P0, the minimum possible step size of the phase shift can be specified by 360° / Q, where Q is a power of 2. For example, Q can be 16, and the phase shift base value P0 = 22.5° can be specified. The phase shift base value P0 can also be specified in other ways. For example, the phase shift base amount P0 can be selected such that the minimum phase shift amount is less than the uniqueness range of the phase shift divided by the length of the Golomb ruler used. The length of the Golomb ruler is the maximum distance between two marks.

[0098] Generally, the following applies to calculating the phase shift amount P_Tx from the product of each Golomb number and the basic phase shift amount P0:

[0099] P_Txn = GR_Marks_n * P0

[0100] where n is the serial parameter of the corresponding transmitter Tx. For n, n = [1; N], where N is the total number of transmitters Tx transmitted simultaneously.

[0101] In a specific exemplary embodiment, the total number of transmitters N = 4. The basic phase shift amount is specified as P0 = 22.5°.

[0102] Therefore, the phase shift amounts P_Tx of the four transmitters Tx1, Tx2, Tx3, and Tx4 are obtained as follows:

[0103] P_Tx1 = 0 * 22.5° = 0°

[0104] P_Tx2 = 1 * 22.5° = 22.5°

[0105] P_Tx3 = 4 * 22.5° = 90°

[0106] P_Tx4 = 6 * 22.5° = 135°

[0107] For all differences Diff_P between the phase shift amounts P_Tx of any two of the transmitters Tx1, Tx2, Tx3, and Tx4, the different value results are as follows:

[0108] Diff_P(2, 1) = P_Tx2 - P_Tx1 = 22.5°

[0109] Diff_P(3, 1) = P_Tx3 - P_Tx1 = 90°

[0110] Diff_P(4, 1) = P_Tx4 - P_Tx1 = 135°

[0111] Diff_P(3, 2) = P_Tx3 - P_Tx2 = 67.5°

[0112] Diff_P(4, 2) = P_Tx4 - P_Tx2 = 112.5°

[0113] Diff_P(4, 3) = P_Tx4 - P_Tx3 = 45°

[0114] For the corresponding chirp pulse sequences Cseq transmitted using the four transmitters Tx1, Tx2, Tx3, and Tx4, the following phase constellations are thus generated, where "Tkt" represents the corresponding cycle of the chirp pulse sequence Cseq, and for clarity, only 10 cycles are shown as an example:

[0115] 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°

[0116] The phases of the transmission signals C1, C2, C3, and C4 increase by their respective phase shift amounts P_Tx1, P_Tx2, P_Tx3, or P_Tx4 in each clock cycle. In the first clock cycle Tktl, the transmission signals C1, C2, C3, and C4 each start with a phase of 0°. For example, for the transmission signal C2 of the second transmitter Tx2, the phase in subsequent cycles increases by the phase shift amount P_Tx2, i.e., 22.5°, between the respective cycles, i.e., between the respective chirp pulses.

[0117] Using the receivers Rx1 and Rx2, the echoes of the transmission signals C1, C2, C3, and C4 reflected at the object 18a are received as the received signals E1_a, E2_a, E3_a, and E4_a, and the echoes of the transmission signals C1, C2, C3, and C4 reflected at the object 18b are received as the received signals E1_b, E2_b, E3_b, and E4_b, and are converted into a form that can be used by the control and evaluation device 22.

[0118] The received signals E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, and E4_b are each subjected to a single two-dimensional fast Fourier transform by corresponding means of the control / evaluation device 22.

[0119] Based on the results of the two-dimensional discrete Fourier transform, four target signals corresponding to the transmission signals C1, C2, C3, and C4 are determined for each detected object 18a and 18b, i.e., the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a of the object 18a and the target signals ZS1_b, ZS2_b, ZS3_b, ZS3_b, ZS4_b of the object 18b. The number of target signals of an object corresponds to the total number of transmitters Tx1, Tx2, Tx3, and Tx4, which is four in this case. At this stage of the method, the exemplary eight target signals have not yet been assigned to the respective transmitters Tx1, Tx2, Tx3, and Tx4, but the corresponding reference signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b have been assigned here. The assignment of the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b, i.e., their verification, is only carried out at a later stage of the method.

[0120] At Figure 6In order to be clearer, the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a are only shown for object 18a in the range-Doppler matrix 24, each time being shown by diagonal hatching extending towards the upper right. In Figure 7 The target signals ZS1_b, ZS2_b, ZS3_b, ZS4_b of object 18b are also represented by diagonal hatching extending towards the lower right. As will be explained below, the target signal ZS4_a for object 18a and the target signal ZS3_b for object 18b fall into the same range-Doppler cell 26 of the range-Doppler matrix 24, and this range-Doppler cell 26 is accordingly shown with cross-hatching. In the exemplary embodiment described, by way of example, object 18a does not perform a relative movement with respect to the radar system 12. Object 18b performs a relative movement with respect to the radar system 12. Furthermore, in the embodiment described, the object targets of objects 18a and 18b which reflect the transmitted signals C1, C2, C3 and C4 are at the same distance from the radar system 12. For the purposes of the present invention, the target object is the region of an object in the monitoring area where the transmitted signal is reflected such that the corresponding echo can be detected by the radar system 12 as a received signal.

[0121] Figure 6 and 7 The range-Doppler matrix 24 shown in can also be referred to as a range-velocity matrix. The range-Doppler matrix 24 is composed of a plurality of range-Doppler cells 26. Each range-Doppler cell 26 is characterized by a range value r and a Doppler value d, the range value r also being referred to as a range bin and the Doppler value d also being referred to as a Doppler bin. By way of example, in Figure 6 and 7 the range value r is shown on the horizontal axis and the Doppler value d is shown on the vertical axis.

[0122] In the present exemplary embodiment, the unambiguous range in the Doppler dimension corresponds to the number of transmitted signals of the chirp pulse sequence Cseq and corresponds to 128 range-Doppler cells 26 in the range-Doppler matrix 24, as described above. In Figure 6 and Figure 7 only some of the range-Doppler cells 26 are shown by way of example in the form of a grid for the sake of clarity.

[0123] Since the object targets of objects 18a and 18b are at the same distance from the radar system 12, all the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b have the same range value r, for example r = 6.

[0124] As a result of the phase constellation according to the invention described above for the transmitted signals C1, C2, C3 and C4, the distance 28 in the Doppler dimension, i.e. respectively asFigure 6 and 7 The differences between the individual Doppler values d between adjacent target signals ZS1_a to ZS2_a, ZS2_a to ZS3_a and ZS3_a to ZS4_a, which are shown originating from object 18a, are different.

[0125] For example, target signal ZS1_a has a range Doppler coordinate of (6, 1). For example, target signal ZS2_a has a range Doppler coordinate of (6, 2). For example, target signal ZS3_a has a range Doppler coordinate of (6, 5). For example, target signal ZS4_a has a range Doppler coordinate of (6, 7). Therefore, the distance 28 between target signals ZS1_a and ZS2_a in the Doppler dimension is equal to 1. Therefore, the distance 28 between target signals ZS2_a and ZS3_a is 3. Therefore, the distance 28 between target signals ZS3_a and ZS4_a is 2.

[0126] Furthermore, as a result of the phase constellations described above for the transmission signals C1, C2, C3 and C4, the distances 28 in the Doppler dimension, i.e. Figure 7 The differences between the corresponding Doppler values d between the adjacent target signals ZS1_b and ZS2_b and the adjacent target signals ZS3_b and ZS4_b shown originating from the object 18b are different. For example, the target signal ZS1_b has a range Doppler coordinate (6, 3). For example, the target signal ZS2_b has a range Doppler coordinate (6, 4). For example, the target signal ZS3_b has a range Doppler coordinate (6, 7). For example, the target signal ZS4_b has a range Doppler coordinate (6, 9). Therefore, the distance 28 in the Doppler dimension between the target signals ZS1_b and ZS2_b is equal to 1. The distance 28 between the target signals ZS3_b and ZS4_b is 2. The distance 28 between the target signals ZS2_b and ZS3_b is 3.

[0127] The phase constellation for transmitting signals C1, C2, C3 and C4 according to the present invention 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 respectively located in different range Doppler bins 26 and can therefore be distinguished from each other. In the exemplary embodiment, only the target signal ZS4_a from object 18a and the target signal ZS3_b from object 18b are in the same range Doppler bin 26 with the range Doppler coordinates (6, 5).

[0128] In order to verify the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b, they must be assigned to the corresponding transmission signals C1, C2, C3, and C4, i.e., the corresponding transmitters Tx1, Tx2, Tx3, and Tx4.

[0129] In order to assign the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b to the corresponding transmission signals C1, C2, C3, and C4, a corresponding power window PW is determined for each range-Doppler cell 26 from the range-Doppler matrix 24. A power window matrix (not shown in the figure) is determined by the power window PW. The power window matrix is used to determine the power window target signals corresponding to the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b from the range-Doppler matrix 24.

[0130] The following formula is used to calculate the power window PW for each range-Doppler cell 26:

[0131]

[0132] where GR_Marks is the Golomb number of the Golomb ruler used with the order GR_Order and is thus 4 in the following exemplary embodiment. The parameter of the range value of the range-Doppler cell 26 is the range value r from [0; R], where R is the number of range-Doppler cells 26 of the range-Doppler matrix 24 in the range dimension. D is the number of range-Doppler cells 26 of the range-Doppler matrix 24 in the Doppler dimension. The parameter of the range-Doppler cell 26 in the Doppler dimension is the Doppler value d from [0; R].

[0133] The following equations are used to assign the correct complex values from the original two-dimensional Fourier transform, i.e., the range-Doppler matrix 24, to the corresponding transmitters Tx1, Tx2, Tx3, and Tx4:

[0134] 2D-FFT TX1 = 2D-FFT[D m + GR_Marks[0]]

[0135] 2D-FFT TX2 = 2D-FFT[D m + GR_Marks[1]]

[0136] …

[0137] 2D-FFT TXN = 2D-FFT[D m+GR_Marks[N - 1]]

[0138] Where N is the number of transmitters, which is 4 in the exemplary embodiment shown. Tx1 to TXN, i.e., Tx1 to Tx4, are the identifiers of the transmitters. R m is the index of the range value of the range - Doppler cell of the detected target in the performance matrix. D m is the index of the Doppler value of the range - Doppler cell of the detected target in the performance matrix.

[0139] Optionally, if other adjacent detections of Doppler cell D m have conflicting peaks in the range - Doppler matrix 24, additional verification can be performed in range cell R m . For the search, the detections in the Doppler cells within the range [mod(D m +GR_length, D), mod(D m -GR_length, D)] can be checked. If there are detections within this range, further verification can be performed to find possible collisions in the range - Doppler matrix 24. These conflicting Doppler cells can be marked, and this information can be used for MIMO signal processing.

[0140] Since the target signals ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b have the same range value in the range - Doppler matrix 24, the correct range can be derived from them in each case.

[0141] Since the first transmission signal C1 is not encoded and is phase - shifted, the Doppler value d associated with the first target signal ZS1_a can be considered as the correct Doppler value, and the correct relative velocity of object 18a can be derived from it. Thus, the correct relative velocity of object 18b can be derived from the Doppler value d of the first target signal ZS1_b.

[0142] After appropriate correction of the phase constellations of the transmission signals C1, C2, C3, and C4, the correct relative velocities can also be derived from the other unique and valid target signals ZS2_a, ZS3_a and ZS2_b, ZS4_b. The target signals ZS4_a and ZS3_b fall into the same range - Doppler cell 26, so they cannot be uniquely assigned to the transmission signals C1, C2, C3, and C4 and the objects 18a and 18b and are to be verified.

[0143] The phase values associated with the unique and valid target signals ZS1_a, ZS2_a, ZS3_a, ZS1_b, ZS2_b, ZS4_b and the phase values associated with the transmission signals C1, C2, C3, and C4 can be determined independently of each other due to the offset and can be used for angle measurements of the azimuth and elevation angles of the objects 18a and 18b relative to the radar system 12 based on the phase.

[0144] From the verified target signals ZS1_a, ZS2_a, ZS3_a, ZS1_b, ZS2_b, ZS4_b, the corresponding relative velocities, the corresponding distances, and the corresponding directions and thus the positions of the objects 18a and 18b relative to the radar system 12 are accordingly determined as object information.

[0145] This method is executed cyclically so that the monitoring area 14 is continuously monitored for the objects 18a and 18b, and accordingly, the detected objects 18a and 18b can be tracked.

[0146] The present invention can also be used for a radar system 12 having more or fewer than four transmitters Tx1, Tx2, Tx3, and Tx4, for example, 12 or more transmitters, and / or more or fewer than two receivers Rx1 and Rx2 and the corresponding transmission signals C1, C2, C3, and C4 or reception signals E1, E2, E3, and E4.

Claims

1. A method for determining at least one object information regarding at least one object (18a, 18b) sensed by a radar system (12), wherein, - By at least four transmitters (Tx1, Tx2, Tx3, Tx4), transmission signals (C1, C2, C3, C4) in the form of chirp pulses are each transmitted as a chirp pulse sequence (Cseq) into the monitoring area (14) of the radar system (12), - The echoes of the transmission signals (C1, C2, C3, C4) reflected at at least one object (18a, 18b) are received as received signals (E1_a, E2_a, E3_a, E4_a, E1_b, E2_b, E3_b, E4_b) by at least one receiver (Rx1, Rx2) and, if necessary, converted into a form usable 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 transform, - 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 result of at least one two-dimensional discrete Fourier transform, - At least one object information is determined from at least one target signal (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b), - Wherein, at the transmitter side, 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 transmission signal is simultaneously transmitted into the monitoring area (14) of the radar system (12) using separate transmitters (Tx1, Tx2, Tx3, Tx4), - Wherein at least three other transmission signals (C2, C3, C4) are each encoded by phase modulation relative to at least one first transmission signal (C1), - Wherein the corresponding phase positions of at least three other transmission signals (C2, C3, C4) each increase or decrease by a constant phase shift amount from one chirp pulse to the next chirp pulse, - Wherein different phase shift amounts are used for at least three other transmission signals (C2, C3, C4), It is characterized in that the corresponding phase shift amounts of at least three other transmission signals (C2, C3, C4) are specified such that for at least four transmission signals (C1, C2, C3, C4) including at least one transmission signal (C1), the absolute difference between the phase shift amounts of any two of the at least four transmission signals (C1, C2, C3, C4) is different, and the 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 basic phase shift amount and a Golomb number of a Golomb ruler assigned to the transmission signals (C2, C3, C4).

2. The method according to claim 1, characterized in that, From one chirp pulse to the next chirp pulse, the phase position of the at least one first transmission signal (C1) remains constant and a corresponding phase shift amount equal to zero is used.

3. The method according to claim 1 or 2, characterized in that, The at least three other transmission signals (C2, C3, C4) are encoded such that, among all the transmission signals (C1, C2, C3, C4) including the at least one first transmission signal (C1), the absolute difference between the phase shift amounts of any two of the at least four transmission signals (C1, C2, C3, C4) is different.

4. The method according to any one of the preceding claims, characterized in that, The phase shift amounts of the transmission signals (C1, C2, C3, C4) are specified such that the absolute difference between no two phase shift amounts is equal to the absolute difference of at least one of the two phase shift amounts of another transmission signal (C1, C2, C3, C4).

5. The method according to claim 1, wherein The Golomb ruler is used, the order of which is less than or equal to the number of transmission signals (C1, C2, C3, C4) to which different phase shift amounts will be assigned, including the at least one first transmission signal (C1).

6. The method according to any one of the preceding claims, characterized in that, At the receiver side, a plurality of target signals (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) are determined in the range-Doppler matrix (24) according to the result of the at least one two-dimensional discrete Fourier transform.

7. The method according to claim 6, wherein At the receiver side, a corresponding 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 the plurality of target signals (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b) to the corresponding transmission signals (C1, C2, C3, C4).

8. The method according to any one of the preceding claims, characterized in that, At least one object information is determined from at least one target signal (ZS1_a, ZS2_a, ZS3_a, ZS4_a, ZS1_b, ZS2_b, ZS3_b, ZS4_b).

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

10. The method according to any one of the preceding claims, characterized in that, A single two-dimensional discrete Fourier transform is performed, in particular a single two-dimensional fast Fourier transform.

11. The method according to any one of the preceding claims, characterized in that, The at least three other transmission signals (C1, C2, C3, C4) are encoded at the transmitter side by binary or higher-order phase shift keying.

12. The method according to any one of the preceding claims, characterized in that, The method is continuously executed multiple times, in particular executed cyclically.

13. A radar system (12) for determining at least one object information about at least one object (18a, 18b), - having at least one transmitter (Tx1, Tx2, Tx3, Tx4) for transmitting transmission signals (C1, C2, C3, C4) in the form of chirp pulses into a monitoring area (14) in a chirp pulse sequence (Cseq), - having at least one receiver (Rx1, Rx2) for receiving echoes of transmitted signals (C1, C2, C3, C4) reflected at at least one object (18a, 18b) 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 at least one transmitter (Tx1, Tx2, Tx3, Tx4) and 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 at least one control and / or evaluation device (22) has means for performing the method according to any one of the preceding claims.

Images