System in a vehicle and method of assembling the same

Abstract

A system in a vehicle includes a radar system having a uniform linear array (ULA) of antenna elements and a uniform rectangular array (URA) of antenna elements to receive reflected signals resulting from transmitted radio frequency energy. The ULA is arranged perpendicular to the URA. Processing circuitry estimates one or more elevation angles using the reflected signals received by the ULA of antenna elements and estimates an azimuth angle corresponding to each of the one or more elevation angles using the reflected signals received by the URA of antenna elements. Each of the one or more elevation angles and a respective one azimuth angle is referred to as an angle of arrival (AOA) of the reflected signals from an object. Control of operation of the vehicle is based on each AOA for each object.

Description

Technical Field

[0001] This subject matter discloses multi-stage angle of arrival (AOA) estimation in vehicle radar systems. Background Technology

[0002] Vehicles (such as cars, trucks, construction equipment, farm equipment, and automated factory equipment) are increasingly using sensors to acquire information about the vehicle and its surroundings. Exemplary sensors for acquiring information about the vehicle include inertial measurement units (IMUs) and steering wheel angle sensors. Exemplary sensors for acquiring information about the area around the vehicle include cameras, radar systems, and lidar systems. This information can contribute to semi-autonomous operation (such as adaptive cruise control, automatic braking), autonomous operation, or warnings to the driver. Different sensors provide different information.

[0003] A radar system comprises transmitting elements that emit radio frequency energy. When the emitted signal encounters an object, some energy is reflected back. The radar system provides range and AOA (Aspect-Oriented Area) for each detected object, and may also provide the rate of change of range (i.e., relative velocity or Doppler) for each object. AOA refers to the angle at which each antenna receives the reflected signal (relative to the antenna's line of sight). AOA estimation can be challenging when reflections are highly correlated. Therefore, it is desirable to provide multi-level AOA estimation in vehicle radar systems. Summary of the Invention

[0004] In one exemplary embodiment, a system in a vehicle includes a radar system. The radar system includes a uniform linear array (ULA) of antenna elements that receive reflected signals generated by transmitted radio frequency energy, and a uniform rectangular array (URA) of antenna elements that receive reflected signals generated by transmitted radio frequency energy, wherein the ULAs of the antenna elements are arranged perpendicular to the URAs of the antenna elements. The system also includes processing circuitry to estimate one or more elevation angles using the reflected signals received by the ULAs of the antenna elements, and to estimate an azimuth angle corresponding to each of the one or more elevation angles using the one or more elevation angles and the reflected signals received by the URAs of the antenna elements. Each of the one or more elevation angles and the corresponding azimuth angle is referred to as the angle of arrival (AOA) of the reflected signal from the object. The processing circuitry also controls the operation of the vehicle based on each AOA of each object.

[0005] Apart from one or more features described here, in the [x, y, z] coordinate system, the antenna elements of ULA are located at the same (x, y) coordinates and different z coordinates.

[0006] In addition to one or more features described here, the antenna elements of the URA are located in different (x,y) coordinates in rows and columns and the same z coordinate.

[0007] In addition to one or more features described herein, the ULA's antenna elements are located in [0, 0, z]. i The URA's antenna elements are located in [x] j , y k [0], where the value of index i is from 1 to M, and M is the number of antenna elements in the ULA, and the value of index j is from 1 to M. l The value of index k is from 0 to M. r The number of antenna elements in URA is M. l and M r The product of.

[0008] In addition to one or more features described herein, the processing circuitry estimates one or more elevation angles by calculating each of the one or more elevation angles using the reflected signal received by the ULA of the antenna element.

[0009] In addition to one or more features described herein, the processing circuitry calculates each of one or more elevation angles based on a computational received signal model.

[0010] In addition to one or more features described herein, the received signal model includes samples of the reflected signal received by the antenna elements of the ULA and a complex normal noise vector.

[0011] In addition to one or more features described herein, the processing circuit estimates the azimuth angle corresponding to each of the one or more elevation angles by calculating the azimuth angle corresponding to each of the one or more elevation angles.

[0012] In addition to one or more features described herein, the processing circuitry calculates the azimuth angle corresponding to each of one or more elevation angles based on a computational received signal model.

[0013] In addition to one or more features described herein, the received signal model includes samples of the reflected signal received by the antenna elements of the URA and a complex normal noise vector.

[0014] In another exemplary embodiment, a method of assembling a system in a vehicle includes assembling a radar system. Assembling the radar system includes forming a uniform linear array (ULA) of antenna elements to receive reflected signals generated by transmitted radio frequency energy, and forming a uniform rectangular array (URA) of antenna elements to receive reflected signals generated by transmitted radio frequency energy. The ULA and URA of antenna elements are arranged perpendicular to the URA of antenna elements. The method also includes configuring processing circuitry to estimate one or more elevation angles using the reflected signals received by the ULA of antenna elements, and to estimate an azimuth angle corresponding to each of the one or more elevation angles using the one or more elevation angles and the reflected signals received by the URA of antenna elements. Each of the one or more elevation angles and the corresponding azimuth angle is referred to as the angle of arrival (AOA) of the reflected signal from the object. The processing circuitry is also configured to control the operation of the vehicle based on each AOA of each object.

[0015] In addition to one or more features described herein, in the [x, y, z] coordinate system, forming an antenna element of a ULA involves positioning the antenna elements of the ULA at the same (x, y) coordinates and different z coordinates.

[0016] In addition to one or more features described herein, forming an antenna element in a URA involves positioning the antenna elements of the URA in rows and columns at different (x, y) coordinates and the same z coordinate.

[0017] In addition to one or more features described herein, the antenna elements of the ULA are positioned in [0, 0, z]. i ], Position the URA's antenna elements at [x j , y k [0], where the value of index i is from 1 to M, and M is the number of antenna elements in the ULA, and the value of index j is from 1 to M. l The value of index k is from 0 to M. r The number of antenna elements in URA is M. l and M r The product of.

[0018] In addition to one or more features described herein, the configuration processing circuitry includes processing circuitry that estimates one or more elevation angles by calculating each of one or more elevation angles using reflected signals received by the ULA of the antenna element.

[0019] In addition to one or more features described herein, the configuration processing circuitry includes processing circuitry that calculates each of one or more elevation angles based on a computational received signal model.

[0020] In addition to one or more features described herein, the calculation of the received signal model includes samples of the reflected signal received by the antenna elements of the ULA and a complex normal noise vector.

[0021] In addition to one or more features described herein, the configuration processing circuitry includes processing circuitry that estimates the azimuth angle corresponding to each of the one or more elevation angles by calculating the azimuth angle corresponding to each of the one or more elevation angles.

[0022] In addition to one or more features described herein, the configuration processing circuitry includes processing circuitry that calculates the azimuth angle corresponding to each of one or more elevation angles based on a computational received signal model.

[0023] In addition to one or more features described herein, the calculation of the received signal model includes samples of the reflected signal received by the antenna elements of the URA and a complex normal noise vector.

[0024] The above-described features and advantages, as well as other features and advantages, of this disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. Attached Figure Description

[0025] Other features, advantages, and details appear only by way of example in the following detailed description, which refers to the accompanying drawings, wherein:

[0026] Figure 1 A vehicle having a radar system that performs multi-level angle of arrival (AOA) estimation, according to one or more embodiments;

[0027] Figure 2 A detailed description is provided of various aspects of a radar system for performing multi-level AOA estimation according to one or more embodiments; and

[0028] Figure 3 This is a flowchart of a method for performing multi-level AOA estimation according to one or more embodiments. Detailed Implementation

[0029] The following description is exemplary in nature only and is not intended to limit this disclosure, its application, or use. It should be understood that in all the drawings, corresponding reference numerals denote the same or corresponding parts and features.

[0030] As previously mentioned, a radar system can be one of the sensors used to acquire information about the environment surrounding a vehicle. The angle of arrival (AOA) provided by the radar system is the angle relative to the antenna's line of sight when a reflected signal arrives at the antenna. Therefore, AOA represents the angle from the radar system to the reflecting object. Distinguishing the azimuth and elevation AOA components can be challenging when reflected signals are highly correlated (i.e., very similar). Existing methods involve estimating the azimuth and elevation separately, and then pairing the elevation and corresponding azimuth estimates associated with the same reflection. Embodiments of the systems and methods described here relate to multi-stage AOA estimation in a vehicle radar system. A uniform linear array (ULA) of antenna elements is used to estimate the elevation angle. A vertically uniform rectangular array (URA) of antenna elements is used to estimate the azimuth angle based on the elevation estimate in a subsequent stage.

[0031] According to an exemplary embodiment, Figure 1 It is a vehicle 100 equipped with a radar system 110 that performs multi-level AOA estimation. Figure 1 The exemplary vehicle 100 shown is a car 101. In addition to the radar system 110, vehicle 100 may include additional sensors 130 (e.g., cameras, lidar systems). The number and location of the radar system 110 and additional sensors 130 are not limited to the exemplary illustration. Vehicle 100 also includes a controller 120. For example, controller 120 may obtain information from the radar system 110 and one or more additional sensors 130, and use that information to control the operation of vehicle 100. An exemplary object 140 (e.g., another vehicle 100, a pedestrian, a tree) is indicated, as is the reflected signal R generated by the object 140 reflecting emitted energy. The AOA relative to the antenna line of sight b is shown. Figure 1 In a two-dimensional view, AOA represents the azimuth angle (in the xy plane), while the elevation angle (between the xy plane and the z-axis) is not visible.

[0032] Radar system 110 may include its own controller, and the processes involved in estimating AOA may be performed by the controller of radar system 110, controller 120, or a combination thereof. The controller and controller 120 of radar system 110 may include processing circuitry, which may include application-specific integrated circuits (ASICs), electronic circuitry, a processor (shared, dedicated, or grouped) and memory executing one or more software or firmware programs, combinational logic circuitry, and / or other suitable components providing the aforementioned functionality.

[0033] Figure 2A radar system 110 for performing multi-level AOA estimation according to one or more embodiments is described in detail. Specifically, antenna configurations are illustrated in meters (m) on the x, y, z coordinate system. A uniform linear array (ULA) 205 and a uniform rectangular array (URA) 215 of antenna elements 210 are shown. There are M antenna elements 210 in ULA 205. Figure 2 In the exemplary case shown, M=16. In the example shown, in URA215, the number of rows Mr of antenna elements 210 is 12, and the number of columns Mc of antenna elements 210 is 4. Therefore, in the exemplary case, the total number of antenna elements 210 in URA215 is 48 (Mr×Mc). As shown, ULA205 is perpendicular to URA215. This relative positioning of ULA205 and URA215 is necessary to eliminate the azimuth component from the angle estimate obtained using ULA205, as referenced Figure 3 Detailed description. All antenna elements 210 receive reflected energy from the radio frequency emissions emitted by the radar system 110.

[0034] Figure 3 This is a flowchart of a method 300 for performing multi-level AOA estimation according to one or more embodiments. The process can be performed by processing circuitry within radar system 110, controller 120, or a combination of both. At block 310, the process includes obtaining reflected signals at each antenna element 210 of ULA 205 and URA 215. At block 320, the process includes estimating the elevation angle based on the reflected signal R received at each antenna element 210 of ULA 205, as described in detail. At block 330, the process includes estimating the azimuth angle corresponding to each elevation angle estimate obtained using ULA 205 (at block 320) based on the reflected signal R received at each antenna element 210 of URA 215, also as described in detail. Once the azimuth and elevation angle estimates (i.e., AOA estimates) are obtained (at blocks 320 and 330), at block 340, those and other information from radar system 110 (e.g., range, rate of change of range) can be used to perform autonomous or semi-autonomous control of vehicle 100 or to provide the driver with an alert regarding one or more objects 140.

[0035] The reflected signal R received at each antenna element 210 forms a vector of signal copies:

[0036] [Equation 1]

[0037] In Equation 1, T denotes transpose. The number of reflected signals R received at each antenna element 210 is L, with indices k = 1, 2, ..., Ns, i.e., the number of time samples. As mentioned earlier, the L received reflected signals R can be highly correlated. Therefore, conventional AOA estimation may not be feasible. The received signal model is given below:

[0038] [Equation 2]

[0039] In equation 2, y represents the time sample t. k The sampled signal (M + M) r x M l ) x 1 complex vector, ϕ is the azimuth angle, θ is the elevation angle, n(t k ) represents the time sample t k Additive noise (M + M) r x M l A complex vector of size 1 x 1. Statistically, the assumptions regarding the received reflected signal R and the noise are:

[0040] [Equation 3]

[0041] [Equation 4]

[0042] In equations 3 and 4, CN represents a complex normal random vector with a mean of 0. The covariance matrix in equation 3... It is an Lx L off-diagonal complex matrix, and in Equation 4, the covariance matrix is ​​the noise power σ. ω The product of the identity matrix I and the identity matrix I.

[0043] Also from Equation 2:

[0044] [Equation 5]

[0045] Generalized array response vector It is given by the following formula:

[0046] [Equation 6]

[0047] Then, to facilitate array processing:

[0048] [Equation 7]

[0049] In Equation 7, H represents the Hermitian operator. In Equations 6 and 7, the array radiation pattern G is given by the following equation:

[0050] [Equation 8]

[0051] Each This is the complex gain associated with one of the M antenna elements 210 in the direction (θ, ϕ). The gain value can be obtained by calibrating each antenna element 210 before deployment in the radar system 110. This value reflects the antenna phase and gain in the presence of mutual coupling with other adjacent antenna elements 210 in ULA205 or URA215. If each antenna element 210 has equal gain in all directions (i.e., omnidirectional), then the radiation pattern G will be an identity matrix. In Equation 6, the steering vector a is the signal phase shift vector observed over the signal transmitted from (θ, ϕ), expressed as:

[0052] [Equation 9]

[0053] In Equation 9, each q m It is antenna element 210 in Figure 2 The positions shown on the x, y, and z axes are indexed m to identify antenna element 210 in ULA205 or URA215. Each position is given by the following formula:

[0054] [Equation 10]

[0055] When antenna element 210 is part of ULA205, the x and y coordinates are 0 ( ),like Figure 2 As shown, or another constant. In the case of antenna element 210 of URA215, the z-coordinate is 0 ( ),like Figure 2 As shown, it could be another constant. Also in Equation 9, the phase shift vector u corresponding to each AOA of interest is given by the following equation:

[0056] [Equation 11]

[0057] Using equations 9 and 11, for ULA205 (i.e. ), the product u, which is part of equation 9 T q m According to Equation 11, only the sin θ component of the vector u will remain. That is, only the elevation angle θ remains. Thus, the reflected signal R received by ULA205 can be used to estimate the elevation angle θ of each reflected signal R reaching each antenna element 210 of ULA205. The elevation angle θ is between -π / 2 and π / 2.

[0058] Known algorithms can be used to obtain estimates of the elevation angle θ. That is, instead of performing a grid search according to existing methods, an estimate of each elevation angle θ can be computed. For example, multi-signal classification (MUSIC) type algorithms (such as root-MUSIC) can be used to compute the elevation angle θ. i , where i = 1, ..., L. According to Equation 2, the root-MUSIC algorithm obtains the singular value decomposition of the covariance matrix, which is obtained using snapshots and consists of the reflected signals R received at antenna elements 210 of the ULA205. According to Equation 1, for each of the M antenna elements 210 of the ULA205, the unitary matrix obtained from the singular value decomposition includes L replica components.

[0059] For elevation angle θ i Each estimated value, as indicated by Equation 11, can be used to estimate the corresponding azimuth angle ϕ. Therefore, it is unnecessary to subsequently pair the separately estimated azimuth and elevation angles, as is done with existing methods. Known algorithms can also be used to obtain the azimuth angle ϕ estimate. For example, an extension of the MUSIC-type algorithm estimates the signal parameters using the rational invariance technique (ESPRIT). According to Equation 2, the ESPRIT algorithm obtains the singular value decomposition of the covariance matrix, which is obtained using a snapshot of the reflected signal R received at antenna element 210 of the URA215.

[0060] While the foregoing disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for its elements without departing from its scope. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this disclosure without departing from its essential scope. Therefore, it is intended that this disclosure be limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A system in a vehicle, comprising: Radar systems, including: A uniform linear array ULA of antenna elements is configured to receive reflected signals generated by transmitted radio frequency energy; and A uniform rectangular array URA of antenna elements is configured to receive reflected signals generated by transmitted radio frequency energy, wherein the URAs of antenna elements are arranged perpendicular to the URAs of the antenna elements; and The processing circuit is configured to estimate one or more elevation angles using reflected signals received by the ULA of the antenna element, to estimate an azimuth angle corresponding to each of the one or more elevation angles using the one or more elevation angles and the reflected signals received by the URA of the antenna element, wherein each of the one or more elevation angles and the corresponding azimuth angle are referred to as the angle of arrival (AOA) of the reflected signal from the object, and to control the operation of the vehicle based on each AOA of each object.

2. The system according to claim 1, wherein, In the [x, y, z] coordinate system, the antenna elements of the ULA are located at the same (x, y) coordinates and different z coordinates, while the antenna elements of the URA are located at different (x, y) coordinates and the same z coordinate in rows and columns. The antenna elements of the ULA are located in [0, 0, z]. i ].

3. The system according to claim 2, wherein, The antenna element of the URA is located in [x j , y k [0], where the value of index i is 1 to M, and the value of index j is 1 to M. l The value of index k is from 0 to M. r The number of antenna elements in URA is M. l and M r The product of.

4. The system according to claim 1, wherein, The processing circuitry is configured to estimate one or more elevation angles by calculating each of the one or more elevation angles using the reflected signal received by the ULA of the antenna element. The processing circuitry is configured to calculate each of the one or more elevation angles based on a received signal model, and the received signal model includes samples of the reflected signal received by the antenna element of the ULA and a complex normal noise vector.

5. The system according to claim 1, wherein, The processing circuitry is configured to estimate the azimuth angle corresponding to each of the one or more elevation angles by calculating the azimuth angle corresponding to each of the one or more elevation angles. The processing circuitry is configured to calculate the azimuth angle corresponding to each of the one or more elevation angles based on a received signal model, and the received signal model includes samples of reflected signals received by the antenna elements of the URA and a complex normal noise vector.

6. A method for assembling a system in a vehicle, the method comprising: Assemble the radar system, including: A uniform linear array ULA forming antenna elements, configured to receive reflected signals generated by transmitted radio frequency energy; and A uniform rectangular array URA forming antenna elements, configured to receive reflected signals generated by transmitted radio frequency energy, wherein the ULA forming the antenna elements and the URA forming the antenna elements include arranging the ULA of the antenna elements perpendicular to the URA of the antenna elements; and The configuration processing circuitry is used to estimate one or more elevation angles using the reflected signals received by the ULA of the antenna element, and to estimate the azimuth angle corresponding to each of the one or more elevation angles using the one or more elevation angles and the reflected signals received by the URA of the antenna element, wherein each of the one or more elevation angles and the corresponding azimuth angle are referred to as the angle of arrival (AOA) of the reflected signal from the object, and the operation of the vehicle is controlled based on each AOA of each object.

7. The method according to claim 6, wherein, In the [x, y, z] coordinate system, forming an antenna element ULA involves positioning the antenna elements of the ULA at the same (x, y) coordinates and different z coordinates, while forming an antenna element URA involves positioning the antenna elements of the URA at different (x, y) coordinates and the same z coordinates in rows and columns.

8. The method according to claim 7, wherein, The antenna element of the ULA is positioned in [0, 0, z]. i The antenna element of the URA is positioned at [x] j , y k [0], where the value of index i is from 1 to M, and M is the number of antenna elements in the ULA, and the value of index j is from 1 to M. l The value of index k is from 0 to M. r The number of antenna elements in URA is M. l and M r The product of.

9. The method according to claim 6, wherein, The configuration of the processing circuitry includes processing circuitry estimating one or more elevation angles by calculating each of the one or more elevation angles using reflected signals received by the ULA of the antenna element. The configuration of the processing circuitry includes processing circuitry calculating each of the one or more elevation angles based on a calculated received signal model, and the calculated received signal model includes a received signal model comprising samples of reflected signals received by the antenna element of the ULA and a complex normal noise vector.

10. The method of claim 6, wherein, The configuration of the processing circuit includes the processing circuit estimating the azimuth angle corresponding to each of the one or more elevation angles by calculating the azimuth angle corresponding to each of the one or more elevation angles. The configuration of the processing circuit includes the processing circuit calculating the azimuth angle corresponding to each of the one or more elevation angles based on a calculated received signal model. The calculated received signal model includes a sample of the reflected signal received by the antenna element of the URA and a complex normal noise vector.

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