SYSTEM AND METHOD FOR DETERMINING THE ARRIVAL ANGLE OF A DESTINATION

Abstract

System for determining the angle of arrival (θ) of a target (140), comprising: one or more transmitters (201), one or more receivers (202) and a local oscillator configured to provide a local reference signal (205) to two or more transmitter / receiver nodes (210); and a controller (120) configured to determine received phase differences for each of the two or more transmitter / receiver nodes (210), wherein each of the received phase differences lies between a signal transmitted by one of the one or more transmitters (201) and received by one of the one or more receivers (202) of the same two or more transmitter / receiver nodes (210), and to estimate the arrival angle (θ) of the target (140) based on the received phase differences determined for the two or more transmitter / receiver nodes (210), characterized in that the controller (120) is further configured to store a matrix A, wherein each column of matrix A is assigned to a different target position and each row of matrix A is assigned to a different one of the one or more receivers (202) or the two or more transmitter / receiver nodes (210), wherein the controller (120) is further configured to obtain a vector y based on the obtained phase differences and to estimate the arrival angle (θ) of the target (140) using a vector w based on: w = |AH y | , where H indicates a Hermitian transposition, each element of the vector w corresponds to an arrival angle (θ) for a different position of the target (140), and the control (120) is further configured to determine the arrival angle (θ) of the target (140) based on which element of the vector w has maximum values.

Description

INTRODUCTION

[0001] The subject matter of the disclosure relates to target angle determination using radar elements of a vehicle with local reference signals.

[0002] The document DE 10 2017 100 909 A1 discloses a system for determining the arrival angle of a target according to the preamble of claim 1 and a method for determining the arrival angle of a target according to the preamble of claim 4.

[0003] Various sensor systems can be used in a vehicle (e.g., cars, trucks, construction equipment, agricultural machinery, operational equipment) to automate or enhance vehicle operation, such as steering, braking, and the like. Vehicles may employ a radar system with high angular resolution to facilitate target acquisition and tracking, which in turn enables the desired automation or enhancement of vehicle operation. Typically, the angle to a target is determined by comparing the phase of a received signal (i.e., a signal transmitted by the radar system and reflected by the target) at two or more antenna elements to the phase of a common reference signal. This phase difference between the received signal phase and the reference signal phase at each element is a function of the angle of incidence of the received signal.The use of a common reference signal at each element requires precise synchronization of the elements so that the multiple phase differences can be used to estimate the angle to the target. However, the carrier frequency commonly used in vehicular radar systems can be on the order of 77 gigahertz (GHz). The effect of path length on attenuation increases with frequency, making distributing a common reference signal on the order of 77 GHz over the distances required for vehicular radar systems impractical.

[0004] Therefore, it is an object of the invention to carry out the target angle determination using radar elements of a vehicle with local reference signals and not with a common reference signal. SUMMARY

[0005] The aforementioned problem is solved by the features of the independent claims. Advantageous further developments emerge from the subclaims.

[0006] A system for determining the angle of arrival of a target includes one or more transmitters, one or more receivers, and a local oscillator, each for providing a local reference signal in two or more transmitter / receiver nodes. The system also includes a controller for determining the obtained phase differences for each of the two or more transmitter / receiver nodes. Each of the obtained phase differences is a signal transmitted by one or more transmitters and received by one or more receivers of the same one of the two or more transmitter / receiver nodes. The controller estimates the angle of arrival of the target based on the obtained phase differences determined for the two or more transmitter / receiver nodes.

[0007] The controller is further configured to store a matrix A. Each column of the matrix A is associated with a different target position, and each row of the matrix A is associated with a different one of the one or more receivers of the two or more transmitter / receiver nodes.

[0008] In addition to one or more of the features described herein, each column of the matrix A comprises a vector a(u i ) for a target position u i : a(ui)=[ejϕ0ejϕ1…ejϕR]T, where T indicates the transposition, each ϕ corresponds to an actual phase difference between a transmitted signal and a received signal with the same of the two or more transmitter-receiver nodes when the target is at the target position u i and the indices 0 to R indicate a sum of R receivers within the two or more sender / receiver nodes.

[0009] The controller is further configured to obtain a vector y based on the obtained phase differences.

[0010] The controller is further configured to estimate the arrival angle of the target using a vector w based on: w=|AH y|, where H indicates a Hermitian transposition.

[0011] Each element of the vector w corresponds to an arrival angle for a different position of the target.

[0012] The controller is further configured to determine the arrival angle of the target based on which element of the vector w has maximum values.

[0013] In addition to one or more of the features described herein, the system is located in a vehicle.

[0014] In addition to one or more of the features described herein, the controller is coupled to a vehicle system that uses the target's angle of arrival for autonomous driving, collision avoidance, or adaptive cruise control.

[0015] A method for determining the angle of arrival of a target includes transmitting a signal from each of one or more transmitters from each of two or more transmitter / receiver nodes. The signal transmitted by each of the two or more transmitter / receiver nodes is generated based on a different local reference signal. The method also includes receiving a resulting reflection signal at each of one or more receivers. Receiving the resulting reflection signal is based on a transmission from one of the two or more transmitter / receiver nodes. The obtained phase differences are determined for each of the two or more transmitter / receiver nodes. Each of the obtained phase differences is a signal transmitted by one or more transmitters and received by one or more receivers of the same one of the two or more transmitter / receiver nodes.The angle of arrival of the target is determined based on the determined phase differences for the two or more transmitter / receiver nodes.

[0016] The method further comprises storing a matrix A. Each column of the matrix A is associated with a different target position and each row of the matrix A is associated with a different one of the one or more receivers of the two or more transmitter / receiver nodes.

[0017] In addition to one or more of the features described herein, storing the matrix A includes storing each column of the matrix A with a vector a(u i ), which corresponds to a target position u i is assigned to: a(ui)=[ejϕ0ejϕ1…ejϕR]T, where T Transpose indicates, each ϕ corresponds to an actual phase difference between a transmitted signal and a received signal with the same of the two or more transmitter-receiver nodes when the target is at the target position u iand the indices 0 to R indicate a sum of R receivers within the two or more sender-receiver nodes.

[0018] The method further comprises obtaining a vector y based on the obtained phase differences.

[0019] Estimating the target's arrival angle involves using a vector w based on: w=|AH y|, where H indicates a Hermitian transposition.

[0020] Each element of the vector w corresponds to an arrival angle for a different position of the target.

[0021] The arrival angle of the target is determined based on which element of the vector w has maximum values.

[0022] In addition to one or more of the features described herein, the target arrival angle is provided to a vehicle system that uses the target arrival angle for autonomous driving, collision avoidance, or adaptive cruise control.

[0023] In addition to one or more of the features described herein, the signal is transmitted at a frequency of 77 gigahertz.

[0024] In another exemplary embodiment, a method for fabricating a system for determining the angle of arrival of a target includes assembling two or more transceiver nodes, each comprising one or more transmitters, one or more receivers, and a local oscillator for generating a local reference signal. The method also includes coupling a controller to the two or more transceiver nodes to determine the angle of arrival of the target based on determining the obtained phase differences for each of the two or more transceiver nodes. Each of the obtained phase differences is a signal transmitted by one or more transmitters and received by one or more receivers of the same one of the two or more transceiver nodes.

[0025] In addition to one or more of the features described herein, the system is coupled to a vehicle system in a vehicle. The vehicle system uses the target's arrival angle for autonomous driving, collision avoidance, or adaptive cruise control.

[0026] The above features and advantages, as well as other features and functions of the present disclosure, will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, advantages and details appear only by way of example in the following detailed description of the embodiments, which detailed description refers to the drawings, where: Fig. 1 is a block diagram of a system for determining the target angle using vehicle radar elements with local reference signals; Fig. 2 is a process flow of a method for determining the angle of arrival using local reference signals according to one or more embodiments; Fig. 3 illustrates an exemplary target whose position is determined according to one or more embodiments; and Fig. 4 illustrates an improvement in target angle estimation according to one or more embodiments. DETAILED DESCRIPTION

[0028] The following description is merely exemplary in nature. It should be understood that throughout the drawings, corresponding reference characters designate like or corresponding parts and features.

[0029] As previously mentioned, the use of a common reference signal for each element of the vehicle radar system requires precise synchronization of the phase difference detected by each receiver antenna element. A common reference signal means that each of the radar system's transmitters receives and processes a signal from the same radio frequency (RF) carrier oscillator. In this case, the phase differences between the signals received at all receivers are generally used to determine the angle to a target. However, the use of a common reference signal spanning the dimension of the vehicle is not feasible at the high frequencies required for the carrier signal (e.g., 77 GHz) due to the high attenuation over distances. The systems and methods set forth herein relate to determining the target angle using vehicle radar elements with local reference signals.The radar system includes two or more nodes, each with one or more transmit antenna elements and one or more receive antenna elements. Each of the nodes uses a different local reference signal obtained from a different local oscillator. Therefore, phase differences between signals received by receivers in different nodes cannot be used for accurate target angle determination. According to embodiments, the angle of arrival of the target to the vehicle is instead determined based on the received signals in each of the nodes, as set forth herein.

[0030] According to an exemplary embodiment, Fig. 1 is a block diagram of a system for determining the target angle using vehicle radar elements with local reference signals. Fig. The exemplary vehicle 100 shown in Figure 1 is a motor vehicle 101. The vehicle 100 includes a radar system 110 which, with reference to Fig. 2. Exemplary transmitter / receiver nodes 210-1 to 210-N (commonly referred to as 210) of the radar system 110 are shown in Fig. 1. An exemplary target 140 that can be detected by the radar system 110 is shown in Fig. 1. Determining the angle of arrival θ to the target 140 with respect to the center of the array of transmitter / receiver nodes 210 is performed by a controller 120, according to one or more embodiments.

[0031] The controller 120 includes a processing circuit, which may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor 115 (shared or dedicated or group), and a memory 125 that may store one or more software or firmware programs, as in Fig. 1, executes a combinational logic circuit and / or other suitable components that provide the described functionality. The controller 120 may provide information regarding the target 140 to one or more vehicle systems 130. The vehicle systems 130 may include, for example, a collision avoidance system, a cruise control system, or a fully autonomous driving system. The vehicle systems 130 use the target information to supplement or automate vehicle operation.

[0032] Fig. 2 is a process flow of a method for determining the angle of arrival θ using local reference signals according to one or more embodiments. Fig. 2 illustrates the exemplary radar system 110 having N nodes 210-1 through 210-N (generally referred to as 210). Transmitters 201-1 through 201-N (generally referred to as 201) and receivers 202-1 through 202-Nm (generally referred to as 202) are disposed in each node 210. Specifically, in the exemplary embodiment, one transmitter 201 and m receivers 202 are part of each node 210. Each node 210 is associated with various local reference signals 205-1 through 205-N (generally referred to as 205). The transmitters 201 in each node transmit sequentially according to a time-division multiplexing scheme or simultaneously according to a frequency-division or code-division multiplexing scheme. For the receivers 202 in any node 210, only the reflections resulting from the transmission by the transmitter 201 in the same node 210 are relevant. The transmitters 201 and receivers 202 of a node use the same local reference signal 205.In alternative embodiments, each node 210 may have more than one transmitter 201 or only one receiver 202.

[0033] At block 220, among other things, local phase differences are determined. The local phase difference refers to the difference between the phase of the signal transmitted by transmitter 201 and received by a specific receiver 202 within the same node 210. For example, if transmitter 201-1 of node 210-1 transmits a signal, the difference between the phase of the transmitted signal and the phase of the received signal at receiver 202-1-1 is determined at block 220. The phase difference between the same transmitted signal and the signal received at each of the receivers 202-1-2 to 202-1-m is also determined. Thus, at each block 220, m phase differences based on the one transmitter 201 and m receivers 202 in each node 210 are determined and recorded.If each transmitter / receiver node 210 includes not one, as shown in the example, but q transmitters 201, the phase difference between each of the q transmitters 201 and each of the m receivers 202 (i.e., m phase differences per transmitter 201) is determined. At block 230, the m phase differences determined at the N nodes 210 are used to determine the target position 140 with respect to . Fig. 3 to be estimated in further detail.

[0034] Fig. Figure 3 illustrates an exemplary target 140 whose position is determined according to one or more embodiments. For illustrative purposes, two nodes 210-1, 210-2 are shown, each with a transmitter 201 Tx and two receivers 202 Rx1 and Rx2. The phase shift of the signal received at each of the receivers 202 is shown in Fig. 3. Each phase shift can be expressed as the distance traveled by the associated signal. For example, the phase shift at receiver 202 Rx1 in node 1 is a function of the distance p0 from transmitter 201 Tx in node 1 to destination 140 and the distance p1 from destination 140 to receiver 202 Rx1 in node 1, where p0+p1 is the total distance traveled by the signal to receiver 202 Rx1 in node 1. As another example, the phase shift at receiver 202 Rx2 in node 2 is a function of the distance p3 from transmitter 201 Tx in node 2 to destination 140 and the distance p5 from destination 140 to receiver 202 Rx2 in node 2, where p3+p5 is the total distance traveled by the signal to receiver 202 Rx2 in node 2. The phase differences are expressed according to the distance, which is given below: ϕ0=2π(p0+p1λ) ϕ1=2π(p0+p2λ) ϕ2=2π(p3+p4λ) ϕ3=2π(p3+p4λ)

[0035] In Eq. 1-4, λ indicates the wavelength of the transmitted signal and is considered equivalent for signals transmitted by both transmitters 201 in nodes 210-1 and 210-2, as in the exemplary case in Fig. 3 shown.

[0036] If the position of the Fig. 3 is designated as u0, is the vector of received signals (received at the four in Fig. 3 shown receivers 202), based on the phase differences described above, given by: a(u0)=[ejϕ0ejϕ1ejϕ2ejϕ3]

[0037] The vector elements denote the angle of arrival (AOA) of the signal from the target 140. These are, for example, the elements of a(u0) in Eq. 5 corresponding to the angle of arrival of the signals from a position of the target 140 at u0. The vector shown in Eq. 5 would have N*m elements instead of four elements if the Fig. 2 shown N-nodes 210 with m receivers 202 each instead of the ones shown in Fig. 3 were used. Furthermore, if per transmitter / receiver node 210, as already mentioned, q transmitters 201 are present, then the vector shown in Eq. 5 would have N*m*q elements. If the vector of received signals is obtained for K+1 different positions of the target 140 (ie, for u0, u1, ..., u k ), then a matrix A can be expanded as: A=[a(u0)a(u1)…a(uk)]

[0038] As Eq. 6 shows, each column of the matrix A is a vector a(u i ).

[0039] After matrix A has been developed using distances traveled by transmitted signals for each target position in question, as described above, the target position for a detected target 140 can be determined using a received signal y according to: w=‖AHy‖=[|a(uo)Hy||a(u1)Hy|…|a(uo)Hy|]

[0040] In Equation 7, H refers to a Hermitian transpose. The vector y is obtained at block 230 based on determining phase differences at block 220. If there were no noise at all in the system, the vector y would be identical to a(u0) when the target 140 is at position u0, the vector y would be identical to a(u1) when the target 140 is at position u1, and so on. The vector w has the same number of elements as the number of columns of the matrix A, as given by Equation 7, and each element of the matrix w is given by: wi=|a(ui)Hy|

[0041] That is, each column vector of matrix A, which becomes a row vector based on Hermitian transpose, is correlated with the column vector y to provide an element in the vector w. The position of the target 140 is estimated as the index i of w for which Eq. 8 has a maximum value (i.e., the column of matrix A that yields the element of vector w in Eq. 7 with the maximum value). Consequently, the AOA of the signals from the target 140 can be estimated by determining the element of vector w with the maximum value.

[0042] Fig.4 shows an improvement in AOA estimation according to one or more embodiments. The beamforming results (result of Eq. 8) are shown. Angles are given in degrees along axis 410 and amplitude in decibels (dB) along axis 420. The angular resolution with which AOA can be estimated is shown for a radar system with one transceiver node 210 (graph 440) and two transceiver nodes 210 (graph 430), where each transceiver node 210 has two transmitters 201 and four receivers 202. As graphs 430, 440 show, increasing the number of nodes 210 with their independent local reference signals 205 increases the angular resolution with which AOA can be estimated. That is, the graphic 430 associated with two nodes 210 has a narrow angular range with high amplitude (narrower beam) compared to the graphic 440 associated with only one node 210.This narrower angular beam indicates improved angular resolution, which allows the radar system 110 to estimate the angle of the target point 140 with greater accuracy and also improves the separation of nearby reflections.

Claims

[1] A system for determining the angle of arrival (θ) of a target (140), comprising: one or more transmitters (201), one or more receivers (202) and a local oscillator configured to provide a local reference signal (205) in each of two or more transmitter / receiver nodes (210); and a controller (120) configured to determine obtained phase differences for each of the two or more transmitter / receiver nodes (210), each of the obtained phase differences being between a signal transmitted by one of the one or more transmitters (201) and received by one of the one or more receivers (202) of a same one of the two or more transmitter / receiver nodes (210), and to estimate the angle of arrival (θ) of the target (140) based on the obtained phase differences determined for the two or more transmitter / receiver nodes (210), characterized by , that the controller (120) is further configured to store a matrix A, wherein each column of the matrix A is associated with a different target position and each row of the matrix A is associated with a different one of the one or more receivers (202) of the two or more transmitter / receiver nodes (210), wherein the controller (120) is further configured to obtain a vector y based on the obtained phase differences and to estimate the angle of arrival (θ) of the target (140) using a vector w based on: w=|AHy|, where H indicates a Hermitian transpose, each element of the vector w corresponds to an angle of arrival (θ) for a different position of the target (140), and the controller (120) is further configured to determine the angle of arrival (θ) of the target (140) based on which element of the vector w has maximum values. [2] The system of claim 1, wherein each column of the matrix A contains a vector a(u i ) for a target position u i includes: a(ui)=[ejϕ0ejϕ1…ejϕR]T, where T indicates transpose, each ϕ corresponds to an actual phase difference between a transmitted signal and a received signal with the same one of the two or more transmitter / receiver nodes (210) when the target (140) is at the target position u i and the indices 0 to R indicate a sum of R receivers (202) within the two or more transmitter / receiver nodes (210). [3] The system of claim 1, wherein the system is located in a vehicle (100) and the controller (120) is coupled to a vehicle system that uses the angle of arrival (θ) of the target (140) to perform autonomous driving, collision avoidance, or adaptive cruise control. [4] A method for determining the angle of arrival (θ) of a target (140), comprising: Transmitting a signal from each of one or more transmitters (201) from each of two or more transmitter / receiver nodes (210), wherein the signal transmitted by each of the two or more transmitter / receiver nodes (210) is generated based on a different local reference signal (205); Receiving a resulting reflection signal at each of one or more receivers (202), wherein receiving the resulting reflection signal is based on a transmission from a same one of the two or more transmitter / receiver nodes (210); Determining the obtained phase differences for each of the two or more transmitter / receiver nodes (210), wherein each of the obtained phase differences is between a signal transmitted by one of the one or more transmitters (201) and received by one of the one or more receivers (202) of a same one of the two or more transmitter / receiver nodes (210); and Estimating the angle of arrival (θ) of the target (140) based on the obtained phase differences determined for the two or more transmitter / receiver nodes (210), characterized by that the procedure further comprises: Storing a matrix A, wherein each column of the matrix A is associated with a different target position and each row of the matrix A is associated with a different one of the one or more receivers (202) of the two or more transmitter / receiver nodes (210); and Obtaining a vector y based on the obtained phase differences and estimating the angle of arrival (θ) of the target (140) using a vector w based on: w=|AHy|, where H indicates a Hermitian transpose, wherein estimating the angle of arrival (θ) using the vector w includes each element of the vector w corresponding to an angle of arrival (θ) for a different position of the target (140) and determining the angle of arrival (θ) of the target (140) is based on which element of the vector w has maximum values. [5] The method of claim 4, wherein storing the matrix A comprises storing each column of the matrix A including a vector a(u i ), which corresponds to a target position u i assigned includes: a(ui)=[ejϕ0ejϕ1…ejϕR]T, where T indicates transpose, each ϕ corresponds to an actual phase difference between a transmitted signal and a received signal with the same one of the two or more transmitter / receiver nodes (210) when the target is at the target position u iand the indices 0 to R indicate a sum of R receivers (202) within the two or more transmitter / receiver nodes (210). [6] The method of claim 4, further comprising providing the arrival angle (θ) of the target (140) to a vehicle system that uses the arrival angle (θ) of the target (140) to perform autonomous driving, collision avoidance, or adaptive cruise control, wherein the signal is transmitted at a frequency of 77 gigahertz.

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