Radar angle ambiguity resolution

Abstract

Radar angular ambiguity resolution is disclosed. Techniques and apparatus for radar angular ambiguity resolution are described. These techniques enable the angular position of a target to be determined based on a spatial response having multiple amplitude peaks. Rather than considering only which peak has the highest amplitude, the techniques for radar angular ambiguity resolution select a frequency sub-spectrum or multiple frequency sub-spectra that emphasize amplitude or phase differences in the spatial response, and analyze the irregular shape of the spatial response across a wide field of view to determine the angular position of the target. In this way, each angular position of the target has a unique signature that the radar system can determine and use to resolve the angular ambiguity. Using these techniques, the radar can have an antenna array element spacing that is greater than half the center wavelength of the reflected radar signal used to detect the target.

Description

[0001] Description of the case

[0002] This application is a divisional application of Chinese invention patent application No. 201880036085.5, filed on August 22, 2018. Technical Field

[0003] The present disclosure generally relates to radar angle ambiguity resolution. Background Art

[0004] Radar is a useful device that can detect and track objects, map surfaces, and map weather patterns. While radar is a common tool used in military and air traffic control operations, technological advances are making it possible to integrate radar into electronic devices. In many cases, radar can replace bulky and expensive sensors (such as cameras) and provide improved performance in the presence of varying environmental conditions (such as low lighting and fog) or in the presence of moving or overlapping targets. While using radar can be advantageous, there are many challenges associated with using radar in commercial devices.

[0005] One such issue involves integrating radar into consumer devices. Specifically, smaller consumer devices impose constraints on the design of radar antennas. To meet size or layout constraints, for example, fewer antenna elements and greater or lesser spacing between them can be used. However, such radar antenna designs can come at the expense of angular ambiguity, making it challenging for the radar to estimate the angular position of a target. When the position of a target cannot be determined due to angular ambiguity, the effective operation and capabilities of the radar are significantly reduced, frustrating the user or limiting the types of applications or environments the radar can support. Summary of the Invention

[0006] Techniques and apparatus are described that enable radar angular ambiguity resolution. These techniques enable the determination of a target's angular position based on a spatial response having multiple amplitude peaks. Rather than considering only which peak has the highest amplitude, the techniques for radar angular ambiguity resolution select a frequency sub-spectrum or multiple frequency sub-spectra that emphasize amplitude or phase differences in the spatial response and analyze the irregular shape of the spatial response across a wide field of view to determine the target's angular position. In this way, each angular position of the target has a unique signature that the radar system can determine and use to resolve the angular ambiguity. Using these techniques, the radar can have an antenna array element spacing greater than half the center wavelength of the reflected radar signal used to detect the target.

[0007] Various aspects described below include a radar system having a frequency selector, an antenna array, a digital beamformer, and an angle estimator. The frequency selector is configured to select a transmit frequency spectrum for a radar signal and cause a transmitter to transmit the radar signal using the transmit frequency spectrum. The antenna array is configured to receive the radar signal using at least three antenna elements. The digital beamformer is configured to generate a spatial response across a field of view based on the received radar signal, the spatial response having a shape across the field of view. The angle estimator is configured to analyze the shape of the spatial response across the field of view. Based on the shape of the spatial response, the angle estimator is further configured to determine an angle of arrival of the radar signal to estimate the angular position of a target that reflected the radar signal.

[0008] The various aspects described below also include a method for selecting a transmit frequency spectrum for a radar signal. The method also includes transmitting the radar signal using the transmit frequency spectrum and receiving the radar signal reflected by a target via the antenna array. Based on the received radar signal, a spatial response is generated across a field of view. The spatial response includes an amplitude response and a phase response. In addition, the method includes analyzing a shape of the amplitude response and a shape of the phase response to identify a characteristic of the shape of the amplitude response and another characteristic of the shape of the phase response. The shape of the amplitude response has at least two peaks within the field of view, and the at least two peaks are associated with angular ambiguity. Based on the characteristic and the other characteristic, the angular ambiguity within the field of view of the spatial response is resolved to determine the direction of the target that reflected the radar signal.

[0009] The various aspects described below also include another method for transmitting a radar signal using a frequency spectrum. The method also includes receiving the radar signal reflected by a target via an antenna array. In addition, the method includes dividing the frequency spectrum into at least two frequency sub-spectra and generating at least two spatial responses for the at least two frequency sub-spectra. The method also includes performing complex coherence on the at least two spatial responses to generate at least one phase coherence map. Based on the phase coherence map, the angular position of the target is estimated.

[0010] Aspects described below also include a system having means for determining a transmit frequency spectrum based on element spacing of an antenna array, means for analyzing a shape of a spatial response, and means for determining an angle of arrival of a reflected radar signal based on the shape of the spatial response. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The apparatus and techniques for enabling radar angle ambiguity resolution are described with reference to the following drawings. Like numbers are used throughout the drawings to reference similar features and components:

[0012] Figure 1 Illustration of an example environment in which radar angle ambiguity resolution can be implemented.

[0013] Figure 2-1 Illustration of example beam steering for target detection.

[0014] Figure 2-2 Illustration of example angular ambiguity.

[0015] Figure 3 Example amplitude and phase plots of the spatial response for two angular positions of the target are shown.

[0016] Figure 4 An example radar system is illustrated as part of a computing device.

[0017] Figure 5 Illustration of example single-frequency sub-spectrum selection for radar angle ambiguity resolution.

[0018] Figure 6 Illustration of example multi-frequency sub-spectrum selection for radar angle ambiguity resolution.

[0019] Figure 7 Illustrate example radar signal processing techniques for radar angle ambiguity resolution.

[0020] Figure 8 Illustration of example complex coherence used for radar angle ambiguity resolution.

[0021] Figure 9 Illustration of an example method for radar angle ambiguity resolution.

[0022] Figure 10 An example computing system that embodies radar-based force sensing or in which techniques enabling the use of radar-based force sensing may be implemented is illustrated. DETAILED DESCRIPTION

[0023] summary

[0024] This document describes techniques and apparatus for radar angular ambiguity resolution. These techniques and apparatus are designed to determine the angular position of a target by resolving angular ambiguities resulting from the design of the radar antenna and the wavelength of the radar signal. In particular, antenna array element spacing greater than half the wavelength can significantly increase the number of angular ambiguities, making it challenging to distinguish the direction of arrival of reflected radar signals. In general, the angular ambiguity depends on the distribution of antenna array elements and the central wavelength of the radar signal (e.g., the wavelength corresponding to the center frequency of the radar signal).

[0025] Conventional angular estimation techniques identify the angular position of a target based on the peak amplitude of the spatial response. In other words, the target's location is determined based on the azimuth and elevation angles at which the radar detects the strongest response. Typically, conventional radar systems have antenna array designs that minimize angular ambiguity based on an optimal wavelength (e.g., element spacing less than half the optimal wavelength).

[0026] To further avoid these angular ambiguities, other conventional techniques constrain the field of view, which represents the range of angles considered possible for the angular position of a target. By limiting the field of view, conventional techniques can avoid hazy regions with angular ambiguity, thereby reducing false detections. However, this reduces the range of angles that the radar system can monitor to detect targets, which can significantly limit the radar system's capabilities. As an example, if the field of view is limited to angles between approximately -45 degrees and 45 degrees, angular ambiguity can be avoided for a wavelength of 5 millimeters (mm) and an element pitch of 3.5 mm (e.g., an element pitch of 70% of the wavelength). As a result, the radar system may be unable to detect targets beyond the 45-degree limit.

[0027] As constraints increase the element spacing, such as for radar systems integrated into smaller electronic devices, angular ambiguities become more prevalent. These angular ambiguities cause multiple peak amplitudes to exist in the spatial response, making it challenging for conventional techniques to determine the angle of a target. In some cases, the highest peak amplitude in the spatial response may not correspond to the target's location. Furthermore, the multiple peak amplitudes may be within approximately ten decibels of each other, or within some other ambiguity threshold where the radar system cannot confidently determine whether a target is detected in the main lobe or side lobes of the antenna pattern. Furthermore, for wideband radars capable of transmitting and receiving radar signals using a wide range of different center wavelengths, the element spacing may not be optimal for each of the different center wavelengths, making some radar signals more susceptible to angular ambiguity than others.

[0028] Rather than considering peak amplitude alone, techniques for resolving radar angular ambiguity analyze the shape of the spatial response across the field of view and select frequencies that emphasize amplitude or phase differences across that spatial response. Typically, the field of view is larger than conventional and includes an ambiguity region, which is used as a source of information and enables analysis of amplitude and phase differences across additional angles. By distinguishing different steering angles through these amplitude and phase differences and identifying features in the shape of the spatial response, the radar can resolve angular ambiguity and determine the angular position of the target. In other words, techniques for radar angular ambiguity resolution enable a target to have unique signatures for different angular positions. The unique signature can be determined through signal processing techniques, pattern matching, or machine learning.

[0029] This document now turns to an example environment, after which example apparatus, example methods, and example computing systems are described.

[0030] Sample Environment

[0031] Figure 1 FIG1 is an illustration of an example environment 100 in which techniques for using radar angular ambiguity resolution and apparatus including radar angular ambiguity resolution may be implemented. Environment 100 includes a radar system 102 embedded in a computing device 104. Computing device 104 may use radar system 102 to detect the presence of a user, map the user's face for authentication, track the user's gestures for touchless control, track the movement of one or more users around computing device 104 for a specific application, and the like. Radar system 102 may further determine the range and angular position of the user over time.

[0032] To integrate radar system 102 within computing device 104, the arrangement of antenna elements 106 within radar system 102 may be based on the size or layout constraints of computing device 104. Radar system 102 may include at least three antenna elements 106 positioned in a two-dimensional shape to enable radar system 102 to determine a two-dimensional vector associated with the angle of arrival of a reflected radar signal (e.g., to determine both the azimuth and elevation angles of a target). Typically, two of antenna elements 106 are positioned along one dimension of angular space (e.g., the azimuth or horizontal dimension), while another antenna element 106 is positioned along another dimension of antenna space relative to one of the two antenna elements 106 (e.g., the elevation or vertical dimension). However, other configurations of radar system 102 may include two antenna elements 106 so that either the azimuth or elevation angle can be estimated by radar system 102.

[0033] exist Figure 1 , two example radar systems 102 are illustrated. A first radar system 102-1 includes four antenna elements 106 within a rectangular arrangement 110 with an element spacing 108-1. A second radar system 102-2 includes three antenna elements 106 within a triangular arrangement 112 with another element spacing 108-2. As described herein, element spacing 108 is determined relative to the centers of adjacent antenna elements 106. In some cases, element spacing 108 is non-uniform, such as a rectangular arrangement 110, which may have different element spacing 108 along the horizontal and vertical axes of the rectangular arrangement 110. Other configurations of antenna elements 106 are also possible, such as an "L"-shaped configuration in which one of the antenna elements 106 in the rectangular arrangement 110 is removed.

[0034] For radar system 102 embedded within computing device 104, the element pitch may be, for example, between about one millimeter (mm) and five millimeters. In situations where element pitch 108 is greater than half the central wavelength of the radar signal (e.g., greater than 60% of the wavelength, 70% of the wavelength, 80% of the wavelength, etc.), ambiguity may make it challenging for radar system 102 to determine the angular position of the target, such as with respect to Figure 2-1 and Figure 2-2 As described in more detail.

[0035] Figure 2-1 An example beam steering for target detection is illustrated. In depicted environment 200-1, radar system 102 searches for target 202 by steering the main lobe 204 of the antenna pattern using digital beamforming techniques. Digital beamforming enables the responses from each receive antenna element 106 in the antenna array of radar system 102 to be digitally combined to form multiple simultaneous beams. Generally speaking, the multiple simultaneous beams represent different steering angles 206 of main lobe 204. Steering angle 206-1 may, for example, include a two-dimensional angular direction of main lobe 204 having azimuth and elevation components.

[0036] Radar system 102 determines the angular position of target 202 by detecting radar signal 208 reflected from target 202 and determining which steering angle 206 corresponds to the angle of arrival of radar signal 208. Digital beamforming is used to generate spatial response 210-1, which includes amplitude and phase information for different steering angles 206. Figure 2-1 , amplitude information is shown in spatial response 210-1 via different shading. Darker shading indicates higher amplitudes and lighter shading indicates lower amplitudes. Assuming the highest amplitude represents the angular position of target 202, steering angle 206-1 is shown as having the highest amplitude across field of view 212 (e.g., the range of steering angles 206). However, as Figure 2-2 As shown in , angular ambiguity is such that the highest peak amplitude does not always represent the angular position of target 202 , or multiple peaks can make it challenging to determine which direction corresponds to the location of target 202 and whether there is one target 202 or multiple targets 202 in field of view 212 .

[0037] Figure 2-2 Example angular ambiguity is shown. Although Figure 2-1200-1, but the antenna pattern has additional undesirable lobes that can be directed toward target 202 for different steering angles 206. As shown in environment 200-2, these undesirable lobes include at least one sidelobe 214 or at least one grating lobe. Typically, sidelobe 214 has an amplitude response that is lower than mainlobe 204, and grating lobes, which are one type of sidelobe 214, have an amplitude response that is relatively close to mainlobe 204. Although conventional techniques can design the characteristics of the antenna array to increase the amplitude difference between mainlobe 204 and sidelobe 214 or to reduce the number of grating lobes within field of view 212, these techniques may not be possible if radar system 102 is integrated into a smaller computing device 104.

[0038] As shown in environment 200-2, if main lobe 204 is steered in another direction away from target 202, such as by steering angle 206-2, side lobe 214-1 becomes unintentionally directed toward target 202. Therefore, the resulting spatial response 210-2 has multiple peak amplitudes within field of view 212; Figure 2-1 2. Assume that the amplitudes at these two steering angles 206 are relatively similar, conventional techniques cannot distinguish whether target 202 is positioned at steering angle 206-1 or steering angle 206-2 (e.g., the angular difference between the two steering angles 206 is insufficient to determine the angular position of target 202). This may further cause conventional radar system 102 to erroneously determine that additional targets are present in the environment (e.g., causing a false detection) or cause radar system 102 to identify the position of target 202 as corresponding to an incorrect steering angle 206 (e.g., steering angle 206-2). Although Figure 2-2 The middle sidelobe 214 - 1 is described as causing angular ambiguity, but grating lobes can also cause angular ambiguity.

[0039] Because multiple steering angles 206 can have large amplitudes for a single target 202, determining which of the responses corresponds to the target 202 is a challenge that radar angle ambiguity resolution addresses. Rather than considering only which peak has the highest amplitude, techniques for resolving radar angle ambiguity analyze the shape of the spatial response 210 across a field of view 212. In this case, the field of view 212 includes an ambiguity zone to enable consideration of amplitude or phase differences across additional angles. When considering the previous example for a center wavelength of 5 millimeters (mm) and an element spacing of 3.5 mm, the field of view 212 may include angles greater than -45 degrees and 45 degrees, such as angles between approximately -90 degrees and 90 degrees, or up to approximately -180 degrees and 180 degrees. The above-described angular ranges may also be applied across one or more directions (e.g., azimuth and / or elevation). With respect to Figure 3Analyzing the shape of spatial response 210 to estimate the angular position of target 202 is further described.

[0040] Figure 3 Example amplitude and phase plots of the spatial response 210 for two angular positions of the target 202 are shown. The amplitude plot 302 (e.g., amplitude response) and the phase plot 304 (e.g., phase response) depict the amplitude and phase differences that may occur for different angular positions of the target and for different steering angles 206, respectively. A first amplitude response 306-1 and a first phase response 308-1 are shown for the target 202 positioned at a first angular position 310-1. Similarly, a second amplitude response 308-1 and a second phase response 308-2 are shown for the target 202 positioned at a second angular position 310-2. In this example, these differences are considered across angles between -180 degrees and 180 degrees.

[0041] As shown in amplitude graph 302, an ambiguity exists for two angular positions 310. In this example, first amplitude response 306-1 (shown via a solid line) has the highest peak at first angular position 310-1 and a smaller peak at second angular position 310-2. While the highest peak corresponds to the actual location of target 202, the smaller peak ambiguities angular position 310. In contrast, second amplitude response 306-2 (shown via a dashed line) has a smaller peak at second angular position 310-2 and a higher peak at first angular position 310-1. In this case, the smaller peak corresponds to the location of the target. These two amplitude responses 306 illustrate different angular ambiguities that can be resolved by analyzing subtle differences in the shape of amplitude responses 306. Characteristics of the shape may include, for example, roll-off, peak or null width, angular location of peaks or nulls, and / or the height or depth of peaks and nulls. Typically, peaks and nulls occur where the derivative of the amplitude response is zero. The shape characteristics may also be associated with side lobes, which represent other peaks within the field of view that have smaller amplitudes than the highest peak. Additional shape characteristics may also be considered, such as symmetry or lack thereof. Similar shape characteristics may be analyzed in phase diagram 304. The shapes of phase responses 308-1 and 308-2 may provide additional information for distinguishing the actual location of target 202. Based on these analyzed shapes, the angular position of target 202 may be determined. Figure 3 Some of the peaks and zeros are identified in the amplitude plot 302 and phase plot 304 of FIG.

[0042] In more detail, consider Figure 4 , Figure 4The radar system 102 is shown as part of a computing device 104. The computing device 104 is illustrated with various non-limiting example devices including a desktop computer 104-1, a tablet 104-2, a laptop 104-3, a smartphone 104-4, a computing watch 104-5, computing glasses 104-6, a gaming system 104-7, a microwave oven 104-8, and a vehicle 104-9. Other devices such as televisions, drones, trackpads, drawing tablets, netbooks, e-readers, home automation and control systems, and other household appliances may also be used. Note that the computing device 104 may be wearable, non-wearable but mobile, or relatively immobile (e.g., a desktop computer and an appliance).

[0043] The radar system 102 may be used as a standalone radar system or used with or embedded in many different computing devices 104 or peripherals, such as in a control panel that controls home appliances and systems, in an automobile to control interior functions (e.g., volume, cruise control, or even the steering of the automobile), or as an accessory to a portable computer to control computing applications on a laptop.

[0044] Computing device 104 includes one or more computer processors 402 and computer-readable media 404, including memory media and storage media. Applications and / or operating systems (not shown) embodied as computer-readable instructions on computer-readable media 404 can be executed by computer processor 402 to provide some of the functionality described herein. Computer-readable media 404 also includes radar-based applications 406 that use radar data generated by radar system 102 to perform functions such as gesture-based control, facial mapping, or user authentication.

[0045] The computing device 104 may also include a network interface 408 for transmitting data over a wired, wireless, or optical network. For example, the network interface 408 may transmit data over a local area network (LAN), a wireless local area network (WLAN), a personal area network (PAN), a wired local area network (WAN), an intranet, the Internet, a peer-to-peer network, a point-to-point network, a mesh network, etc. The computing device 104 may also include a display (not shown).

[0046] Radar system 102 includes a communication interface 410 for transmitting radar data to a remote device, although this need not be used when radar system 102 is integrated within computing device 104. Typically, the radar data provided via communication interface 410 is in a format usable by radar-based application 406.

[0047] Radar system 102 also includes at least one antenna array 412 and at least one transceiver 414 to transmit and receive radar signals 208. Antenna array 412 includes at least three antenna elements 106, as described with respect to FIG. Figure 1 As described. In some cases, a portion of antenna elements 106 may be dedicated to transmitting radar signals 208, while another portion of antenna elements 106 may be dedicated to receiving radar signals 208. In other cases, antenna elements 106 may be used for both transmitting and receiving. The element spacing 108 associated with antenna elements 106 that receive radar signals may be less than, greater than, or equal to half the center wavelength of the radar signal. Via antenna array 412, radar system 102 may form a steered or unsteered, wide or narrow, or shaped (e.g., hemispherical, cubic, sector, conical, cylindrical) beam. Steering and shaping may be achieved using analog or digital beamforming techniques.

[0048] Radar system 102 can be configured for continuous wave or pulse radar operation. Various modulations can be used, including linear frequency modulation, step frequency modulation, and phase modulation. Radar system 102 can be configured to transmit microwave radiation in the 1 GHz to 400 GHz range, the 4 GHz to 100 GHz range, and narrower frequency bands (such as 57 GHz to 63 GHz). Generally, the operation of radar system 102 is associated with a range of frequencies (e.g., a frequency spectrum), a portion of which can be used to transmit radar signal 208 based on a center frequency and bandwidth within the frequency spectrum.

[0049] Radar system 102 may also include one or more system processors 416 and system media 418 (e.g., one or more computer-readable storage media). System media 418 includes a frequency selector 420, a digital beamformer 422, and an angle estimator 424, which may at least partially implement radar angle ambiguity resolution.

[0050] Frequency selector 420 selects a portion of a frequency spectrum (e.g., a frequency sub-spectrum including a center frequency and a bandwidth) for transmitting radar signal 208. In some cases, a portion of the frequency spectrum is selected based on element spacing 108 to increase the amplitude and phase differences between at least two different steering angles 206 compared to another frequency sub-spectrum. In other words, frequency selector 420 enables angular ambiguity to be resolved by determining a range of frequencies for which a unique spatial response exists for different angular positions of target 202. In effect, the frequencies selected by frequency selector 420 enhance and emphasize the difference across at least a portion of the spatial response. Figure 5 and Figure 6 Two example frequency selection techniques are discussed: single-frequency sub-spectrum selection and multi-frequency sub-spectrum selection.

[0051] Figure 5An example single-frequency sub-spectrum selection for radar angle ambiguity resolution is illustrated. Generally, radar system 102 has a frequency spectrum 502 (e.g., a range of frequencies) that limits the available center frequencies and bandwidths for transmitting radar signal 208. Frequency spectrum 502 can be divided into a plurality of sub-spectra 504, such as sub-spectra 504-1, 504-2, 504-3, 504-4, and 504-M, where the variable "M" represents a positive scalar number. Sub-spectra 504 can have the same or different bandwidths, such as 500 megahertz (MHz), one gigahertz (GHz), two gigahertz, and so on.

[0052] For single frequency sub-spectrum selection, frequency selector 420 selects one of frequency sub-spectra 504 for transmitting radar signal 208. Because angular ambiguity depends on the center wavelength of radar signal 208 and the element spacing 108 of antenna array 412, frequency sub-spectra 504 may be determined such that the center frequency of frequency sub-spectra 504 reduces angular ambiguity by reducing the number or amplitude of sidelobes 214 and grating lobes. In some cases, the center frequency may be selected based on known element spacing 108 stored in system media 418 of radar system 102 or computer-readable media 404 of computing device 104.

[0053] As an example, frequency sub-spectra 504-2, 504-3, and 504-4 may include frequencies between approximately 57 GHz and 59 GHz, 59 GHz and 61 GHz, and 61 GHz and 63 GHz, respectively. Assuming element spacing 108 is approximately 3.5 mm, frequency selector 420 may determine that frequency sub-spectra 504-2 and 504-4 reduce the amplitude of the side lobes compared to frequency sub-spectra 504-3. The amplitude of the side lobes may be reduced by, for example, 0.5 decibels, one decibel, or more. Therefore, frequency sub-spectra 504-2 and 504-4 use the techniques used for radar angle ambiguity resolution to unambiguously render steering angles 206-1, 206-2, 206-3, and 206-4. In contrast, frequency sub-spectra 504-3 is ambiguous between these steering angles and, therefore, is not selected by frequency selector 420.

[0054] Figure 6 An example multi-frequency sub-spectrum selection is shown for radar angular ambiguity resolution. Multi-frequency sub-spectrum selection enables different distributions of angular ambiguities for different frequency sub-spectra. While the shape and characteristics of the angular ambiguities may vary, the main peak associated with target 202 maintains a similar shape in each of the different frequency sub-spectra.

[0055] For multi-frequency sub-spectrum selection, frequency selector 420 selects at least two frequency sub-spectra 504 for transmitting radar signal 208. In this case, the frequency sub-spectra 504 selected for multi-frequency sub-spectra selection have the same bandwidth for coherence. Multi-frequency sub-spectra 504 can be transmitted simultaneously or separated in time using a single radar signal 208 or multiple radar signals 208. Figure 6 Three example multi-frequency sub-spectrum selections 602, 604, and 606 are depicted in FIG.

[0056] Frequency selection 602 includes three consecutive frequency sub-spectra 504-2, 504-3, and 504-4. In this case, the consecutive frequency sub-spectra selection enables one radar signal 208 to be transmitted using a bandwidth that includes three consecutive frequency sub-spectra 504. When the reflected radar signal 208 is received, spatial response 210 can be segmented according to the different frequency sub-spectra 504.

[0057] In contrast to frequency selection 602, frequency selection 604 includes three non-contiguous frequency sub-spectra 504-1, 504-3, and 504-M. Non-contiguous frequency sub-spectra 504 enable further separation between selected frequency sub-spectra 504, which can further emphasize the amplitude and phase differences between different steering angles 206. Generally speaking, the further apart frequency sub-spectra 504 are relative to each other, the easier it is for radar system 102 to resolve angular ambiguities.

[0058] Another frequency selection 606 is also shown to indicate that two frequency sub-spectra (such as frequency sub-spectra 504-2 and 504-4) can be selected by the frequency selector 420. This is beneficial for situations where it is desired to reduce the number of calculations or the additional information provided by selecting another frequency sub-spectra 504 is not required. Figure 6 As shown in , any combination of frequency sub-spectra can be used for multi-frequency sub-spectra selection. Using these frequency sub-spectra 504, a phase coherence map is generated and used to estimate the angular position of the target 202, as shown in FIG. Figure 8 Described in more detail.

[0059] Return to Figure 6 After the frequency selector 420 causes the transceiver 414 to transmit the radar signal 208 using the selected frequency sub-spectrum 504, the antenna elements 106 of the antenna array 412 receive the radar signal 208, which is reflected by the target 202. Figure 7 As shown in , the system processor 316 processes the responses from the antenna elements 106 to detect the target 202 and determine the angular position of the target 202.

[0060] Figure 71 illustrates an example radar signal processing technique for radar angle ambiguity resolution. The system processor 316 generates raw data 702 representing a digital response from each of the antenna elements 106 of the antenna array 412 for receiving the radar signal 208. Typically, the response from each of the antenna elements 106 is processed by a separate receive channel. Figure 7 , where "N" represents a positive scalar value. Raw data 702 includes digital information (e.g., in-phase and quadrature data) spanning a time period and for different wave numbers associated with radar signal 208, as illustrated by raw data 702-1, which is associated with one of the N channels. System processor 416 performs a fast Fourier transform (FFT) on raw data 702 to generate pre-processed data 704. Pre-processed data 704 includes digital information spanning the time period and for different ranges (e.g., range intervals), as illustrated by pre-processed data 704-1, which is associated with one of the N channels.

[0061] Figure 4 The digital beamformer 422 receives the pre-processed data 404 and generates a spatial response 210. The spatial response 210 includes amplitude and phase information, an example of which is illustrated in FIG. Figure 2-1 、 Figure 2-2 and Figure 3 The spatial response includes spatial response subsets 706-0 to 706-K, which include spatial responses for different time intervals (such as time t0 and time t k ) is a set of spatial responses 210. In this case, "K" represents a positive scalar value.

[0062] Each spatial response 210 within the spatial response subset 706 contains digital information for a set of azimuth, elevation, and range. The set of azimuths and elements represents the field of view 212 for forming different steering angles or beams by the digital beamformer 422. The techniques for radar angular ambiguity resolution can be used with any number of beams. As an example, the digital beamformer 422 can generate approximately 2,000 beams, 4,000 beams, 6,000 beams, etc.

[0063] Figure 4Angle estimator 424 receives spatial response 210 and estimates the angular position of target 202 by analyzing the shape of spatial response 210 across field of view 212. In some aspects, angle estimator 424 may use signal processing techniques, pattern matching techniques, or machine learning to determine the angle of arrival of radar signal 208. Example signal processing techniques may utilize algorithms to analyze the shape of spatial response 210 and determine a difference indicating the direction of target 202. Typically, the shape of spatial response 210 is analyzed to determine one or more characteristics of the shape, such as peak roll-off, null shape, angles associated with peaks or nulls, or asymmetry. These characteristics may be determined based on an amplitude other than the maximum amplitude (e.g., an amplitude associated with a smaller peak or another null), at least two amplitudes (either of which may or may not be associated with the maximum amplitude (e.g., to determine a slope associated with the width of a peak or null)), phase, both amplitude and phase, and the like. Alternatively, the example pattern matching technique may compare the characteristics of the spatial response 210 to a predetermined pattern or previously generated spatial response 210 stored in the system media 418 of the radar system 102 or the computer readable medium 404 of the computing device 104. The example machine learning technique may evaluate changes in the spatial response 210 over time. Based on these changes, the machine learning may detect the moving target 202 and record information for detecting future targets at the angle of the identified target 202. To reduce the complexity of the machine learning, a portion of the spatial response may be provided to the machine learning to reduce the number of calculations. The portion may be based on, for example, a slice of a range that includes the maximum amplitude response compared to other ranges. If a multi-frequency sub-spectrum selection is selected by the frequency selector 420, the angle estimator 424 may perform complex coherence, such as with respect to Figure 8 As described, the position of the target 202 is identified based on the differences that occur in the shapes of the angular ambiguities for different frequency sub-spectra.

[0064] Figure 8 Figure 3. Complex coherence used for radar angle ambiguity resolution. Figure 6Frequency selection 602 is selected by frequency selector 420, and digital beamformer 422 processes each of frequency sub-spectra 504-2, 504-3, and 504-4 to generate spatial responses 210-1, 210-2, and 210-3, respectively. Using these spatial responses 210, angle estimator 424 performs complex coherence to generate phase coherence maps 802-1, 802-2, and 802-3. Phase coherence map 802 contains phase information of the complex coherence (e.g., interferogram) between pairs of beamformed reconstructions. Due to the different frequency sub-spectra 504, angle estimator 424 can use phase coherence map 802 to determine the position of target 202 because a portion of spatial response 210 associated with target 202 generally maintains a similar shape in each of the different frequency sub-spectra, while the shape of the angular ambiguity may be different.

[0065] The phase information is calculated according to Equation 1:

[0066]

[0067] Wherein, Sn represents the signal received by antenna element "n", E{} represents the expected value estimate, and "*" represents the complex conjugate.

[0068] If through Figure 8 As shown by the arrows in , phase coherence maps 802-1, 802-2, and 802-3 are calculated using the spatial responses 210 associated with the frequency sub-spectra 504-2 and 504-3, the frequency sub-spectra 504-2 and 504-4, and the frequency sub-spectra 504-3 and 504-4, respectively. In general, each possible target position within the field of view 212 has a unique phase coherence map 802, which can be identified by the angle estimator 424.

[0069] Example Method

[0070] Figure 9 An example method 900 for radar angle ambiguity resolution is depicted. The method 900 is shown as a set of operations (or actions) that are performed but are not necessarily limited to the order or combination of operations shown herein. In addition, any one or more of these operations may be repeated, combined, reorganized, or chained to provide a variety of additional and / or alternative methods. In portions of the following discussion, reference may be made to the following examples, which are referenced only by way of example. Figure 1 、 Figure 2-1 and Figure 2-2 Environments 100, 200-1 and 200-2 and Figure 4 These techniques are not limited to performance by one entity or multiple entities operating on one device.

[0071] At 902, a transmit frequency spectrum for the radar signal is selected. For example, the transmit frequency spectrum may include a frequency sub-spectrum 504 within the frequency spectrum 502 of the radar system 102. The transmit frequency spectrum may have a central wavelength greater than, less than, or equal to twice the element spacing of the antenna array. Example wavelengths may be approximately 50%, 75%, 110%, 120%, 150%, or 200% of the element spacing 108. Assuming the element spacing 108 is approximately 3.5 mm, the transmit frequency spectrum may include frequencies between approximately 57 GHz and 62 GHz, with corresponding wavelengths between approximately 5.3 mm and 4.8 mm. Frequency selector 420 may further determine the transmit frequency spectrum for the radar signal 208 based on the element spacing 108 of the antenna elements 106 of the antenna array 412. The transmit frequency spectrum may be selected to enhance and emphasize amplitude or phase differences associated with different positioning or steering angles 206 of the target 202. The transmit frequency spectrum may also include at least one frequency or a range of frequencies, such as those used for frequency modulation. The transmitted frequency spectrum may further include multiple frequency sub-spectra 504 that are transmitted individually, simultaneously, or as one continuous frequency sub-spectra.

[0072] At 904 , a radar signal is transmitted using the transmit frequency spectrum. For example, frequency selector 420 may cause transceiver 414 to transmit radar signal 208 .

[0073] At 906, the radar signal reflected by the target is received via the antenna array. For example, the antenna array 412 receives Figure 2-1 and Figure 2-2 The radar signal 208 is reflected by the target 202 as shown in FIG. The antenna array 412 may include at least three antenna elements 106, such as Figure 1 As shown in .

[0074] At 908, a spatial response across the field of view is generated based on the received radar signal. The spatial response includes an amplitude response and a phase response. For example, the digital beamformer 422 can generate a spatial response 210 that includes amplitude and phase information for different steering angles 206, range intervals, and time intervals. Figure 2-1 、 Figure 2-2 、 Figure 3 、 Figure 7 and Figure 8 An example spatial response 210 or portion of a spatial response 210 is described in .

[0075] At 910, a shape of the amplitude response and a shape of the phase response are analyzed to identify a characteristic of the shape of the amplitude response and another characteristic of the shape of the phase response. The shape of the amplitude response has at least two peaks associated with angular ambiguity within the field of view. The characteristics of the amplitude response or the phase response may include one or more amplitudes or phases associated with the shape of peaks, nulls, or sidelobes across one or more angles within the field of view. Example shape characteristics may include slope (e.g., derivative), height or depth, width, and asymmetry. Based on at least two peaks having an amplitude difference within an ambiguity threshold (such as less than about ten decibels), the at least two peaks may be associated with angular ambiguity.

[0076] At 912, angular ambiguity is resolved based on the characteristic and another characteristic to determine the direction of the target that reflected the radar signal. These characteristics can be used, for example, by a signal processing algorithm, pattern matching technique, or machine learning technique implemented by angle estimator 424 to resolve the angular ambiguity. Generally, the transmit frequency spectrum and shape of spatial response 210 enable target 202 to have unique signatures at different directions, thereby enabling radar system 102 to resolve the angular ambiguity and estimate the angular position of target 202. The determined direction of the target can then be used by radar-based application 406 to track a user's gestures, detect approaching obstacles, map the user's face for authentication, and the like.

[0077] Example computing system

[0078] Figure 10 Illustrate various components of an example computing system 1000, which may be used as a reference to the previous Figure 1 and Figure 4 Any type of client, server, and / or computing device described is implemented to perform radar angle ambiguity resolution.

[0079] The computing system 1000 includes a communication device 1002 that enables wired and / or wireless communication of device data 1004 (e.g., received data, data being received, data scheduled for broadcast, data packets of data). The device data 1004 or other device content may include configuration settings for the device, media content stored on the device, and / or information associated with a user of the device. The media content stored on the computing system 1000 may include any type of audio, video, and / or image data. The computing system 1000 includes one or more data inputs 1006 that can be used to receive any type of data, media content, and / or input, such as human speech, radar-based applications 406, predetermined spatial responses for angle estimation or information about element spacing 108 of the radar system 102 within the computing system 1000, user-selectable input (explicit or implicit), messages, music, television media content, recorded video content, and any other type of audio, video, and / or image data received from any content and / or data source.

[0080] The computing system 1000 also includes a communication interface 1008, which can be implemented as any one or more of a serial and / or parallel interface, a wireless interface, any type of network interface, a modem, and any other type of communication interface. The communication interface 1008 provides a connection and / or communication link between the computing system 1000 and a communication network through which other electronic, computing, and communication devices communicate data with the computing system 1000.

[0081] The computing system 1000 includes one or more processors 1010 (e.g., any of microprocessors, controllers, etc.) that process various computer-executable instructions to control the operation of the computing system 1000 and enable implementation of techniques for radar angle ambiguity resolution or in which radar angle ambiguity resolution may be specifically implemented. Alternatively or in addition, the computing system 1000 may be implemented using any one or a combination of hardware, firmware, or fixed logic circuitry, along with processing and control circuitry generally identified at 1012. Although not shown, the computing system 1000 may include a system bus or data transfer system that couples the various components within the device. The system bus may include any one or a combination of different bus structures, such as a memory bus or memory controller, a peripheral bus, a universal serial bus, and / or a processor or local bus utilizing any of a variety of bus architectures.

[0082] The computing system 1000 also includes computer-readable media 1014, such as one or more storage devices that enable persistent and / or non-transitory data storage (i.e., as opposed to mere signal transmission), examples of which include random access memory (RAM), non-volatile memory (e.g., any one or more of read-only memory (ROM), flash memory, EPROM, EEPROM, etc.), and disk storage devices. The disk storage device can be implemented as any type of magnetic or optical storage device (such as a hard drive, a recordable and / or rewritable compact disk (CD), any type of digital versatile disk (DVD), etc.). The computing system 1000 may also include a mass storage media device (storage media) 1016.

[0083] The computer-readable medium 1014 provides a data storage mechanism for storing device data 1004, as well as various device applications 1018 and any other types of information and / or data related to operational aspects of the computing system 1000. An operating system 1020 may be maintained as a computer application along with the computer-readable medium 1014 and executed on the processor 1010. The device applications 1018 may include a device manager, such as any form of control application, software application, signal processing and control module, code native to a particular device, a hardware abstraction layer for a particular device, and the like.

[0084] The device applications 1018 may also include system components, engines, or managers for implementing radar angle ambiguity resolution. In this example, the device applications 1018 include a frequency selector 420, a digital beamformer 422, and an angle estimator 424.

[0085] in conclusion

[0086] Although techniques using and apparatus including radar angle ambiguity resolution have been described in language specific to features and / or methods, it is to be understood that the subject matter of the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example implementations of radar angle ambiguity resolution.

Claims

1. A radar system comprising: an antenna array comprising a plurality of antenna elements, the antenna array configured to receive radar signals using the plurality of antenna elements; and A processor configured to: generating a spatial response across a field of view based on received radar signals and using digital beamforming; characterizing a shape of the spatial response across the field of view based on two or more data points within the spatial response, wherein the shape of the spatial response has at least one peak within the field of view, the at least one peak associated with angular ambiguity; and Based on the shape of the spatial response, an angle of arrival of the radar signal is determined to estimate an angular position of an object that reflected the radar signal.

2. The radar system of claim 1 , wherein: The spatial response includes an amplitude response; a shape of the amplitude response across the field of view comprising at least two amplitude peaks and at least one amplitude zero; and The processor is further configured to determine the angle of arrival of the radar signal based on a shape of the at least two amplitude peaks and a shape of the at least one amplitude zero.

3. The radar system of claim 2, wherein: The at least two amplitude peaks include a first peak having a first amplitude and a second amplitude peak having a second amplitude; and An amplitude difference between the first amplitude and the second amplitude is within an ambiguity threshold such that the amplitude difference alone is insufficient for determining the angle of arrival of the radar signal.

4. The radar system according to claim 1, wherein: The processor is configured to characterize the shape of the spatial response based on one or more of: the steepness of the peak roll-off within the spatial response; the width of a peak within the spatial response; the width of a zero value within the spatial response; an angular position of the peak within the spatial response; an angular position of the null within the spatial response; the height of the peak within the spatial response; the depth of the null within the spatial response; or Symmetry of the response across the space.

5. The radar system of claim 1 , wherein: The spatial response includes a phase response; a shape of the phase response across the field of view comprising at least one phase peak and at least one phase zero; and The processor is further configured to determine the angle of arrival of the radar signal based on a shape of the at least one phase peak and a shape of the at least one phase zero.

6. The radar system according to claim 1, wherein: The field of view is greater than 90 degrees.

7. The radar system of claim 1 , wherein: The radar signal is associated with a frequency spectrum; The frequency spectrum is associated with a central wavelength; and Each of the plurality of antenna elements has an element pitch greater than half the center wavelength.

8. The radar system according to claim 1, wherein: The plurality of antenna elements includes at least three antenna elements positioned in a triangular arrangement.

9. A method for radar angle ambiguity resolution, the method comprising: receiving, via an antenna array, a radar signal using a plurality of antenna elements of the antenna array; generating a spatial response across a field of view based on received radar signals and using digital beamforming; characterizing a shape of the spatial response across the field of view based on two or more data points within the spatial response, wherein the shape of the spatial response has at least one peak within the field of view, the at least one peak associated with angular ambiguity; and Based on the shape of the spatial response, an angle of arrival of the radar signal is determined to estimate an angular position of an object that reflected the radar signal.

10. The method according to claim 9, wherein: The spatial response includes an amplitude response; a shape of the amplitude response across the field of view comprising at least two amplitude peaks and at least one amplitude zero; and Determining the angle of arrival further comprises determining the angle of arrival based on shapes of the at least two amplitude peaks and a shape of the at least one amplitude zero.

11. The method according to claim 10, wherein: The at least two amplitude peaks include a first peak having a first amplitude and a second amplitude peak having a second amplitude; and An amplitude difference between the first amplitude and the second amplitude is within a ambiguity threshold.

12. The method according to claim 9, wherein Characterizing the shape of the spatial response includes one or more of the following: Characterizes the steepness of the peak roll-off within the spatial response; Characterizing the width of a peak within the spatial response; Characterizes the width of a zero value within the spatial response; characterizing an angular position of the peak within the spatial response; characterizing an angular position of the null within the spatial response; characterizing the height of the peak within the spatial response; characterizing a depth of the null within the spatial response; or Symmetries of the response across the space are identified.

13. The method according to claim 9, wherein: The spatial response includes a phase response; a shape of the phase response across the field of view comprising at least one phase peak and at least one phase zero; and Determining the angle of arrival further includes determining the angle of arrival based on a shape of the at least one phase peak and a shape of the at least one phase zero.

14. A method for radar angle ambiguity resolution, the method comprising: receiving, via an antenna array, a radar signal using a plurality of antenna elements of the antenna array, the radar signal comprising a plurality of frequencies associated with a plurality of frequency sub-spectra; generating, based on the received radar signal and using digital beamforming, spatial responses across a field of view, the spatial responses correspondingly associated with the plurality of frequency sub-spectra, each spatial response comprising an amplitude response having at least two amplitude peaks within the field of view, the amplitude peaks associated with angular ambiguities; and Resolving the angular ambiguity to determine a direction to an object reflecting the radar signal, the resolving comprising: characterizing a shape of at least one of the spatial responses across the field of view based on two or more data points within the spatial response, the shape identifying one of the amplitude peaks as associated with a direction to the object; or generating a phase coherence map using the complex coherence and at least two of the spatial responses; and identifying the direction to the object based on the phase coherence map.

15. The method according to claim 14, wherein: Generating the phase coherence map includes: generating a plurality of phase coherence maps using different combinations of the spatial responses; and Identifying the direction includes identifying similar shapes across the plurality of phase coherence maps, the similar shapes associated with the direction to the object.

16. The method according to claim 14, wherein The multiple frequency sub-spectra include: a first frequency sub-spectrum comprising frequencies between 57 gigahertz and 59 gigahertz; and A second frequency sub-spectrum includes frequencies between 61 gigahertz and 63 gigahertz.

17. The method according to claim 14, wherein: The bandwidths of the multiple frequency sub-spectra are equal.

18. The method according to claim 17, wherein The bandwidth is 2 GHz.

19. The method according to claim 14, wherein The plurality of frequency sub-spectra include at least two consecutive frequency sub-spectra.

20. The method according to claim 14, wherein The plurality of frequency sub-spectra include at least two disjoint frequency sub-spectra.

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