Antenna Phase Center Determination Using Baseband Data

Abstract

One or more aspects of the present disclosure relate to the configuration and management of sensor components. More specifically, one or more aspects of the present application relate to the management of operational parameters of a radar sensor mounted on a vehicle. The radar sensor is illustratively comprised of multiple-input, multiple-output based radar components providing a phased array. A control component obtains and processes the measured complex response of the antenna array and utilizes the processing results to determine a phase center and optimize the operation of the radar sensor components.

Description

[Technical field]

[0001] Cross-reference to related applications This application claims priority to U.S. Provisional Application No. 63 / 202958, entitled "DETERMINING ANTENNA PHASE CENTER USING BASEBAND DATA," filed July 1, 2021. U.S. Provisional Application No. 63 / 202958 is incorporated by reference herein in its entirety. [Background technology]

[0002] Generally described, various vehicles, such as electric vehicles, combustion engine vehicles, hybrid vehicles, etc., can be configured with various sensors and components to facilitate operation. For example, the vehicle can be configured to operate autonomously or semi-autonomously, where user input is optional, reduced, or de-emphasized while moving. In such applications, information regarding the vehicle's motion and surrounding driving environment captured by various sensors / components, such as a radar detection system, can be used to assist in the operation of the vehicle. Typically, the benefits provided by sensor components, such as radar components, can be directly dependent on the control mechanisms and sensor components that are calibrated.

[0003] For antenna components such as radar antennas, the performance of the antenna components can be optimized or improved based on the determination of the antenna phase center. Generally speaking, the antenna phase center is defined as the point at which the signal is collected. The offset between the average phase center and the geometric center of the antenna can range from a few millimeters to a few centimeters. Today's physical antenna phase centers are carefully determined by isolating the antenna from the rest of the radio frequency (RF) and baseband system, placing the antenna in an anechoic chamber, and then performing a precision scan of the antenna pattern (complex antenna pattern) including the antenna's phase response as a function of 3D angle. The antenna response is then post-processed to determine the phase center.

[0004] In other cases, the antenna is moved repeatedly within the measurement domain until its phase response becomes insensitive to rotation. In this case, the phase center can be determined by trial and error after repeated measurements. None of these methods can be used on a fully functional system. The act of isolating the antenna from the system in some ways disturbs the integrity of the measurement and in other cases simply makes the method impractical. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a block diagram of an embodiment of a phase center estimation system.

[0006] [Figure 2A] FIG. 2 is a block diagram logically representing various components of the vehicle, including control and radar components.

[0007] [Figure 2B] FIG. 1 is a block diagram of an embodiment of a phase center estimation system.

[0008] [Diagram 3] FIG. 2 is a block diagram of exemplary components of processing components / services for performing the analysis methodology.

[0009] [Figure 4] 1 illustrates a method for radar sensor configuration processing.

[0010] [Diagram 5] The minimized vector response is shown.

[0011] [Figure 6A] 1 illustrates one embodiment of a one-dimensional angle measurement of the antenna array response before and after a phase center offset.

[0012] [Figure 6B] 1 illustrates one embodiment of a one-dimensional angle measurement of the antenna array response before and after a phase center offset.

[0013] [Figure 6C] 1 illustrates one embodiment of a one-dimensional angle measurement of the antenna array response before and after a phase center offset.

[0014] [Figure 7] The two-dimensional antenna vector response and two optimization algorithms are presented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Generally described, one or more aspects of the present disclosure relate to the configuration and management of sensor components. More specifically, one or more aspects of the present disclosure relate to the management of operational parameters of a radar sensor mounted on a vehicle. The radar sensor illustratively comprises a multi-input, multi-output based radar component providing a phased array. A control component obtains and processes the measured complex response of the antenna array and utilizes the processing results to determine a phase center and optimize the operation of the radar sensor component.

[0016] Generally described, vehicle-based radio detection and ranging (RADAR) systems can be used to actively estimate the distance, angle, or Doppler frequency shift to environmental features by emitting a radio signal and detecting the return of the reflected signal. The distance to the radio reflecting feature can be determined according to the time delay between transmission and reception. Vehicle-based radar systems can emit signals whose frequency varies over time, such as signals having a time-varying frequency ramp, and then relate the difference in frequency between the emitted signal and the reflected signal to a distance estimate. Some systems may also estimate the relative motion of a reflecting object based on the Doppler frequency shift of the received reflected signal.

[0017] In some examples, directional antennas may be used to transmit or receive signals to associate each distance estimate with a bearing. More generally, directional antennas may also be used to focus radiated energy on a given field of interest, such as the vehicle's forward, side, and rearward facing surfaces to detect objects / information. Combining the measured distance with directional information allows for mapping of surrounding environmental features. In other examples, omnidirectional antennas may alternatively be used. In these examples, the receiving antenna may have a 90 degree field of view and may be configured to utilize multiple channels with phase offsets to determine the angle of arrival of the received signal. Thus, radar sensors may be used by autonomous vehicle control systems, for example, to avoid obstacles indicated by sensor information.

[0018] Some exemplary automotive radar systems may be configured to operate in the 76-77 gigahertz (GHz) electromagnetic frequency range. These radar systems may use a transmitting antenna that can focus radiated energy into a tight beam to enable a receiving antenna (e.g., having a wide beam) in the radar system to measure the vehicle's environment with high accuracy.

[0019] Many modern telecommunications standards, especially in the consumer space, employ multiple-input multiple-output antenna (MIMO) technology because it offers significant advantages over similar systems that utilize single antenna transceivers (SISO). Multiple-input multiple-output (MIMO) radar is an advanced type of phased array radar that uses digital receivers and waveform generators distributed across the aperture. MIMO radar signals propagate similarly to multistatic radar.

[0020] In conventional phased array systems, additional antennas and associated hardware are required to improve spatial resolution. MIMO radar systems transmit mutually orthogonal signals from multiple transmit antennas, and these waveforms can be extracted from each receive antenna by a set of matched filters. For example, if a MIMO radar system has x transmit antennas and y receive antennas, the product, or x*y, of the transmitted signals can be extracted from the receiver due to the orthogonality of the transmitted signals. That is, an x*y element virtual antenna array is created using only x+y antennas by performing digital signal processing on the received signals, thereby obtaining finer spatial resolution compared to its phased array counterpart.

[0021] Conventional methods for obtaining radar antenna center can be used in a fully functional system. The act of isolating the antenna from the system in some ways disturbs the integrity of the measurement and in other cases only makes the method impractical. For example, measuring the phase center of 8 or 10 ports in a radar receiver array involves creating multiple coupons with a small number of ports being fed each time (due to the closeness of the ports and the large size of the waveguide feed). Furthermore, in MIMO radar, the phase center is most directly related to the phase center of a virtual array formed by the convolution of the actual receiver array with the location of the Tx antenna array. The conventional methods mentioned above cannot measure such a virtual array because it is only formed when the transceiver chip is transmitting a different coded chirp through each transmitter antenna element.

[0022] The present disclosure provides a method to use the output of the radio transceiver itself to estimate these phase centers, eliminating the need for physical access to the antenna feed port. In this way, it can be used to calibrate radar / GNSS etc. antennas in-situ (on the vehicle), with the possibility of extending the procedure to every car rolling off the production line. The antenna phase center or radiation center refers to a virtual point from which the radiation appears to originate. Such a point is important in applications such as GNSS / GPS, automotive radar etc. In GPS systems, a fixed position is the location of the phase center of the GNSS antenna. In radar applications, the accuracy of the estimation of the angle of arrival of the scattered signal is determined primarily by the accuracy of the antenna's estimated phase center, which is retained by the signal processing algorithm.

[0023] Illustratively, the control component obtains and processes the measured complex response of the antenna array (in the frequency domain) as a function of angle (e.g., azimuth) as a vector field (a collection of vectors laid out along a point corresponding to the orientation of the measurements). The control component then calculates the transformed complex response from a virtual transformation of the origin of the coordinate system. For each such virtual origin, the control component determines the flatness in the complex response of the array ports to identify a point that minimizes the variation of the vector field. The result of such processing can be characterized as declaring or identifying the phase center of the antenna array.

[0024] While various aspects are described according to exemplary embodiments and feature combinations, those skilled in the art will appreciate that the examples and feature combinations are exemplary in nature and should not be construed as limiting. FIG. 1 is a block diagram logically representing various components of a vehicle and analyzer system 100 formed according to aspects of the present application. As shown in FIG. 1, a vehicle 102 includes one or more radar sensor components 104 for utilization in the operation of the vehicle. The individual radar sensor components may be implemented with a MIMO array as shown in FIG. 1. The system may further include a network analyzer 110 and another antenna 112 (illustratively a horn antenna) for generating signals, obtaining measured responses from the MIMO array, and determining operational parameters of the MIMO array. Illustratively, processing of the MIMO array operational parameters does not require manual adjustment of the radar components 104 or modification of the physical components of the underlying hardware components implementing the MIMO array 114. This therefore provides the ability to determine operational parameters of the MIMO array in a more efficient manner, as partially described in the present disclosure, and addresses shortcomings in conventional methods for other determination methods. A detailed configuration of the analysis method of the present application is described below.

[0025] In an exemplary embodiment, one or more aspects of the present application may address the determination of exemplary components of a vehicle and analyzer system 100 within a vehicle or other device that may utilize a radar sensing component, with FIG. 2A illustrating a vehicle 102 comprising a radar component 104, an antenna 106, and a controller component 110. The vehicle 102 may include any type of vehicle incorporating one or more radar sensing components. Additionally, the controller component 108 may include one or more physical or virtual components configured to control the operation of the radar sensing component 104 and the antenna 106 and to perform processing to determine various operating parameters of the radar sensing component 104. Thus, aspects of the present application are not limited to any particular type or implementation of the vehicle 102, the radar sensing component 104, or the antenna 106.

[0026] FIG. 2B is a block diagram logically representing various components of the vehicle and analyzer system 100 formed in accordance with aspects of the present application. FIG. 2B represents an alternative embodiment logically representing FIG. 1, illustrating the utilization and configuration of the analysis method of the present application. FIG. 1 may represent a configuration for measurements with access to the antenna via a coaxial cable or a waveguide. FIG. 2 may represent a configuration for data collection to support phase center estimation without access to the antenna. Due to highly integrated designs, the antenna may not be accessible. FIG. 2B illustrates the generation of a signal 120 received by the MIMO antenna 114. Additionally, FIG. 2B further illustrates the reception of the generated output 122 by the MIMO array 114 to facilitate the determination of the operating parameters of the MIMO antenna 114 in accordance with various aspects of the present application.

[0027] 3 is a block diagram illustrating processing components / services for performing functions of the vehicle and analyzer system 100. The processing components include a processing unit 302, a network interface 304, a computer readable media drive 306, and an input / output device interface.

[0028] The network interface 304 may provide a connection to one or more networks or computing systems. Thus, the processing unit 302 may receive information and instructions from other computing systems or services via the network. The processing unit 302 may also communicate with the memory 310 and further provide output information for optional display via the input / output device interface 308. In some embodiments, the vehicle and analyzer system 100 may include more (or fewer) components than those shown in FIG.

[0029] Memory 310 may include computer program instructions that processing unit 304 executes to implement one or more embodiments. Memory 310 generally includes RAM, ROM, or other persistent or non-transitory memory. Memory 310 may store an operating system 314 that provides computer program instructions used by processing unit 302 in the general management and operation of customer computing device 102. Memory 310 may further include computer program instructions and other information for implementing aspects of the disclosure. For example, in one embodiment, memory 310 includes interface software 312 for receiving a list of discovered SAML-enabled services and operations by selecting one or more services from a customer.

[0030] Additionally, the memory 310 includes a baseband processing component 314 , a set of virtual offsets 316 , and a phase center determination component 318 .

[0031] 4, a routine 400 for an exemplary radar sensor configuration process is described. The routine 400 is exemplary implemented by a processing component / service as shown in FIG. 2B. In block 402, the processing component obtains a complex baseband response of each transceiver port Tx-Rx combination. Illustratively, a complex baseband response is obtained for each frequency and angle scan. Illustratively, the processing component may be located in proximity to the radar sensing components and antenna of the vehicle to obtain the complex baseband response. In block 404, the processing component views the complex response as a vector field.

[0032] In block 406, the processing component assumes a hypothetical change in the origin or center of the radar sensing component, which may be defined as an offset. This allows for the establishment of multiple E^(j*additional path delays) measured from each relative target origin / center to the complex response. In block 408, the processing component calculates the integral of the Laplacian operator over the vector field as a function of the offset.

[0033] Equation (1) describes the Laplacian function as follows: Laplacian (F(Θ i ,φ j ))=0.25*(F(Θ i+1 ,φ j )+F(Θ i ,φ j+1 )+F(Θ i-1 ,φj)+F(Θ i ,φ j-1 ))-F(Θ i ,φ j )

[0034] In general, we explain the physical meaning of the Laplacian of a vector field described on a circle or sphere. Minimizing the Laplacian of the antenna response vector field is equivalent to finding a fixed offset of the antenna's position that results in an invariant (or minimal change) response to changes in the angle of the vector field. Figure 5 shows the resulting minimized vector response 500. As shown in Figure 5, for every point 502, the processing component looks at neighboring points and takes the average measured distance. The processing result corresponds to the minimum of the sum over all points.

[0035] At block 410, the processing component performs further processing. Illustratively, the further processing includes utilizing particle swarm optimization or other search algorithms to determine the offset that has the minimum integral of the Laplacian over the angle cut. Illustratively, the resulting determined offset may be through a single plane or over a portion of a sphere.

[0036] In block 412, the processing component identifies the offset as the phase center (offset from the physical center of rotation) of the antenna using the above criteria. Figures 6A-6C show one-dimensional angle measurements of the antenna array response before phase center offsets 602, 612, 622 and after the resulting phase center offsets 604, 614, 624 for three example ports of the antenna array. As shown in Figures 6A-6C, by appropriately offsetting the antenna positions, a vector field response with many "turns" (e.g., high index numbers relative to the origin) is reduced to one with a "nearly parallel" vector response (i.e., 0 index relative to the new origin). In accordance with block 412, the processing component identifies the new origin as the phase center of this particular element (port) of the array.

[0037] 7 illustrates an example of a two-dimensional antenna vector response showing a uniform vector field 702 with a minimized Laplacian when an offset transform is applied to the vector field response of the antenna. Illustratively, in this example, the processing component utilizes two standard numerical optimization algorithms to search for the point that provides the minimum integral of the Laplacian: particle swarm optimization (PSO) 704 and simulated annealing (SA) 706. However, one skilled in the art will appreciate that additional or alternative algorithms may be used, such as any standard numerical optimization algorithm may be used with appropriate parameters.

[0038] The foregoing disclosure is not intended to limit the disclosure to the exact form or specific field of use disclosed. Thus, various alternative embodiments and / or modifications to the disclosure, whether expressly described or implied herein, are possible in light of the disclosure. Although the embodiments of the disclosure have been described in this manner, those skilled in the art will recognize that changes can be made in form and detail without departing from the scope of the disclosure. Therefore, the disclosure is limited only by the scope of the claims.

[0039] In the foregoing specification, the present disclosure has been described with reference to certain embodiments. However, as those skilled in the art will appreciate, the various embodiments disclosed herein can be modified or implemented in various other ways without departing from the spirit and scope of the present disclosure. Thus, this description should be considered as illustrative and is for the purpose of teaching those skilled in the art how to make and use the various embodiments of the disclosed ventilation assembly. It should be understood that the forms of the disclosure shown and described herein should be construed as representative embodiments. Equivalent elements, materials, processes or steps may be substituted for those typically shown and described herein. Furthermore, some features of the present disclosure may be utilized independently of the use of other features, as will become apparent to those skilled in the art after having the benefit of this description of the present disclosure. The terms "including," "comprising," "incorporating," "consisting of," "have," "is," and the like, used to describe and claim the present disclosure, are intended to be construed in a non-exclusive manner, i.e., allowing for the presence of items, components, or elements not expressly described. References to the singular are also to be construed as relating to the plural.

[0040] Furthermore, the various embodiments disclosed herein should be construed in an illustrative and descriptive sense, and should not be construed as limiting the present disclosure in any way. Any joint references (e.g., attached, fastened, coupled, connected, etc.) are used only to aid the reader in understanding the present disclosure, and may not create limitations with respect to the position, orientation, or use of the systems and / or methods specifically disclosed herein. Thus, any reference to a joint, if any, should be interpreted broadly. Moreover, such a reference to a joint does not necessarily imply that two elements are directly connected to each other. Additionally, and without limitation, all numerical terms such as "first," "second," "third," "primary," "secondary," "main," or any other conventional and / or numerical terms, should also be construed merely as identifiers to aid the reader in comprehension of the various elements, embodiments, variations and / or modifications of the present disclosure, and in particular should not create any limitation as to the order or preference of any element, embodiment, variation and / or modification relative to or over another element, embodiment, variation and / or modification.

[0041] It will also be understood that one or more of the elements shown in the drawings / figures may also be implemented in a more separated or integrated manner, or in some cases removed or rendered inoperative, as may be useful depending on the particular application.

Claims

1. 1. A method for determining a phase center of a radar sensor antenna, comprising: obtaining respective complex baseband responses for a plurality of transceiver port Tx-Rx combinations at each frequency forming part of a time-varying frequency ramp; characterizing the complex baseband response as a function of angle as a vector field; generating, for each offset of the plurality of offsets, a value based on a respective calculation of an integral of a Laplacian operation over the vector field as a function of the respective offset; determining the offset at a minimum integral of the Laplacian operator over an angle cut; and identifying the offset having the minimum integral as a phase center of the radar sensor antenna; The method according to claim 1, wherein the radar sensor antenna is a multiple-input multiple-output array.

2. 2. The method for determining a phase center of a radar sensor antenna as recited in claim 1, wherein said transceiver port combination comprises a transceiver Tx-Rx combination.

3. 2. The method of claim 1, wherein the phase center of the radar sensor antenna comprises a virtual phase center of the multiple-input multiple-output antenna.

4. 2. The method of claim 1, wherein determining the offset at a minimum integral of the Laplacian operator over angle cuts comprises utilizing particle swarm optimization.

5. 1. A radar sensor configuration processing system, comprising: an antenna configured to receive the response; a processor, the processor comprising: Obtaining at least one of the complex baseband responses; characterizing the at least one complex baseband response as a vector field; Calculate the integral of the Laplacian operator as a function of the offset, determining the offset at a minimum integral of the Laplacian operator; A radar sensor configuration processing system configured to identify the offset having the minimum integral as a phase center of the antenna.

6. The radar sensor configuration processing system of claim 5 , wherein the offset corresponds to the offset between the phase center and a physical center.

7. The radar sensor configuration processing system of claim 5 , wherein the response is the complex baseband response.

8. The radar sensor configuration processing system of claim 5 , wherein the processor is further configured to calculate an integral of the Laplacian operator as a function of the offset for a set of offsets.

9. The radar sensor configuration processing system of claim 5 , wherein determining the offset having the minimum integral of the Laplacian operator includes utilizing particle swarm optimization.

10. 6. The radar sensor configuration processing system of claim 5, wherein each of said at least one complex baseband response corresponds to a combination of transceiver ports Tx-Rx.

11. 11. The radar sensor configuration processing system of claim 10, wherein each of said at least one complex baseband response corresponds to a combination of said transceiver ports Tx-Rx at each frequency and angle scan.

12. The radar sensor configuration processing system of claim 5 , wherein the antenna comprises a multiple-input multiple-output antenna.

13. The radar sensor configuration processing system of claim 12 , wherein the phase center of the antenna comprises the phase center of a virtual array of the multiple-input multiple-output antenna.

14. 6. The radar sensor configuration processing system of claim 5, wherein characterizing the at least one complex baseband response as a vector field comprises characterizing the at least one baseband response of an antenna array as a function of angle as the vector field.

15. 1. A vehicle-based radar configuration system, comprising: a vehicle comprising a multiple-input multiple-output antenna, the multiple-input multiple-output antenna comprising at least one of an array of waveform generators and at least one of an array of digital receivers; and a control component comprising a processor, the processor configured to obtain at least one of a complex baseband response and determine a phase center of the multiple-input multiple-output antenna based on a received complex baseband response.

16. The vehicle-based radar configuration system of claim 15 , wherein the phase center is determined as an offset from a physical center.

17. The control component adjusts the phase center of the multiple-input multiple-output antenna based on the complex baseband response. Calculating the integral of the Laplacian operator as a function of the virtual offset; determining the virtual offset using a minimum integral of the Laplacian operator; and identifying the virtual offset that makes the minimum integral of the Laplacian operator a phase center of the multiple-input multiple-output antenna.

18. 20. The vehicle-based radar configuration system of claim 17, wherein determining the phase center of the multiple-input multiple-output antenna based on the complex baseband responses further comprises characterizing the at least one complex baseband response as a vector field prior to calculating an integral of a Laplacian operator as a function of a virtual offset.

19. The vehicle-based radar configuration system of claim 15 , wherein the phase center of the multiple-input multiple-output antenna comprises a virtual phase center of the multiple-input multiple-output antenna.

20. 16. The vehicle-based radar configuration system of claim 15, wherein the determination of the phase center of the multiple-input multiple-output antenna is further based on a calculated angular momentum of a set of virtual offsets.

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