System and method for interpolated virtual aperture radar tracking

Abstract

A method for interpolating virtual aperture array radar tracking comprises: transmitting a first probe signal and a second probe signal; receiving the first reflected probe signal at the radar array; receiving the second reflected probe signal at the radar array; calculating a target range based on at least one of the first reflected probe signal and the second reflected probe signal; corresponding signal instances of the first reflected probe signal to physical receiver elements of the radar array; corresponding signal instances of the second reflected probe signal to virtual elements of the radar array; interpolating the signal instances; calculating a first target angle; and calculating a position of a tracked target relative to the radar array based on the target range and the first target angle.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a continuation-in-part of U.S. patent application No. 16 / 032,369, filed on July 11, 2018, which is a continuation-in-part of U.S. patent application No. 15 / 883,372, filed on January 30, 2018, all of which are incorporated by reference in their entirety. Technical Field

[0003] The present invention relates generally to the field of radar, and more particularly to new and useful systems and methods for interpolating virtual aperture radar tracks.

[0004] background

[0005] Conventional array-based receivers measure the power of an array (e.g., Figure 1 The azimuth and / or elevation angles are calculated by using the time or phase differences between the received probe signals at different receivers (or antennas) within the (1D array) shown. A similar effect can be achieved using a transmit array instead of a receiver array. These traditional solutions are limited: the angular resolution depends on the number of elements in the array and the angle between the array and the target:

[0006]

[0007] Where N is the number of elements in the array, and d is the distance between them.

[0008] While array interpolation can be used to improve the resolution of such systems, typical interpolation schemes require uniform arrays with sub-half-wavelength spacing and may offer limited improvement over non-interpolated systems.

[0009] Therefore, there is a need in the radar art to create new and useful systems and methods for interpolating virtual aperture radar tracks. The present invention provides such new and useful systems and methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a diagram of a prior art example of a 1D receiver array radar system;

[0012] Figure 2A is an example view of the physical aperture in SAR tracking;

[0013] Figure 2B is an example view of the virtual aperture in SAR tracking;

[0014] Figure 3A is an example view of the first physical aperture in VAA tracking;

[0015] Figure 3B is an example view of the second physical aperture in VAA tracking;

[0016] Figure 3C is an example view of the virtual aperture in VAA tracking;

[0017] Figure 4A is a schematic view of a signal incident on a conventional receiver array;

[0018] Figure 4B is a signal view of a signal incident on a conventional receiver array;

[0019] Figure 5A is a schematic view of a signal incident on a VAA system;

[0020] Figure 5B is a signal view of a signal incident on the VAA system;

[0021] Figure 6 is a chart view of a method according to an embodiment of the present invention;

[0022] Figure 7A is an example view of the first physical aperture in IVAA tracking;

[0023] Figure 7B An example view of the pre-interpolation virtual aperture in IVAA tracking.

[0024] Figure 7C is an example view of the virtual aperture after interpolation in IVAA tracking;

[0025] Figure 7D is an example view of the first physical aperture in IVAA tracking;

[0026] Figure 7E is an example view of the pre-interpolated virtual aperture in IVAA tracking;

[0027] Figure 7F is an example view of the virtual aperture after interpolation in IVAA tracking;

[0028] Figure 7G is an example view of the first physical aperture in IVAA tracking;

[0029] Figure 7H is an example view of the virtual aperture after interpolation in IVAA tracking;

[0030] Figure 8 is an example view of the phase shift of two transmitter elements separated by a certain distance;

[0031] Figure 9 is a schematic view of the virtual transmitter and receiver elements in the IVAA system pre-interpolation;

[0032] Figure 10 is the Cartesian coordinate view of the target position parameters;

[0033] Figure 11A is an example view of the physical and virtual elements of the interpolated virtual aperture array;

[0034] Figure 11B is an example view corresponding to the field of view of the interpolated virtual aperture array;

[0035] Figure 12A is an example view of conventional beamforming;

[0036] Figure 12B is an example diagram of beam steering according to a method of an embodiment of the present invention;

[0037] Figure 13 is an example view of target aliases;

[0038] Figure 14A is an example diagram of transmit beam steering according to a method according to an embodiment of the present invention;

[0039] Figure 14B is an example diagram of transmit beam steering according to a method according to an embodiment of the present invention;

[0040] Figure 15 is a schematic diagram of a system according to an embodiment of the present invention; and

[0041] Figure 16 is a schematic diagram of a system according to an embodiment of the present invention.

[0042] Description of Embodiments of the Invention

[0043] The following description of the inventive embodiments of the present invention is not intended to limit the invention to these inventive embodiments, but rather to enable any person skilled in the art to make and use the invention.

[0044] 1. Virtual Aperture Array (VAA) radar tracking

[0045] As discussed in the Background section, traditional array-based radar systems are limited: the angular resolution depends on the number of elements in the receiver array and the angle between the array and the target:

[0046]

[0047] Where N is the number of elements in the array, and d is the distance between them.

[0048] Here, the number of array elements (and the spacing between them) is related to the receiver aperture; that is, more elements (or increased element spacing) results in a larger receiver aperture. As the angular resolution formula indicates, to increase angular resolution (without changing the carrier frequency), the receiver aperture must be increased. This is typically achieved by adding receiver array elements or increasing the spacing between elements; however, these techniques increase the physical size of the receiver array or either its cost or physical complexity. However, the advantage of this traditional technique is that it improves radar resolution with relatively little change in processing latency.

[0049] As an alternative to this traditional technology, synthetic aperture radar (SAR) was created. In SAR, a moving antenna (or antenna array) continuously captures multiple signals as it moves, such as Figure 2A These signals are then combined (using knowledge of the antenna movement) to simulate the effect of a larger antenna, as shown in Figure 2B SAR attempts to simulate an increased radar aperture (thus improving radar resolution), but requires precise antenna motion data and typically requires a significant increase in processing latency. Both requirements are problematic in many applications.

[0050] A novel technique (hereinafter referred to as virtual aperture array (VAA) radar tracking) was created to simulate an increased radar aperture (as exhibited by SAR) without incurring the additional cost / size of increasing the physical array size or the severe disadvantages of SAR (e.g., motion data requirements and high processing latency). This technique was first introduced in parent U.S. patent application Ser. No. 15 / 883,372. Note that while the term "virtual aperture" has various uses in the field of radar tracking, as used in this application, virtual aperture array radar tracking specifically refers to the tracking technique described herein (and not any unrelated techniques sharing the term).

[0051] VAA radar tracking technology works by simultaneously capturing an instance of a first signal at a physical array (like a traditional phased array), then capturing an instance of a second signal at the same physical array (capturing instances of the second signal simultaneously, but not necessarily at the same time as capturing instances of the first signal); if applicable, capturing additional instances in the same manner, and finally processing the data received from all captured instances together to generate a higher resolution radar tracking solution than would otherwise be possible. Notably, the first and second signals (and any additional signals) are encoded with different phase information. This different phase information enables the instance of the second signal to be treated as if it were received at a virtual receiver array that is shifted relative to the physical array (creating a virtual aperture that is larger than the physical aperture). For example, one can Figure 3A A first signal with a first phase encoding is captured as shown and can be Figure 3B As shown, a second signal with a second phase encoding is captured; these signals can be processed together, as shown Figure 3C shown.

[0052] like Figure 4A As shown, when a reflected signal is received from a target that is at an angle to (i.e., not perpendicular to) a six-element radar array, the signal received at each receiver element in the array is phase shifted relative to the signals received at the other elements in the array, as shown in FIG. Figure 4B Based on the phase shift and spacing between elements, the angle of the target relative to the array can be determined.

[0053] like Figure 5A As shown, VAA can simulate the same aperture with only three elements by using two phase-shifted signals, producing Figure 5B The signals at the receiver components are shown (note that the signal at RX1 at t2 is similar to Figure 4B The positioning of the "virtual element" depends on the phase shift between the first and second signals.

[0054] 2. Method for interpolating virtual aperture array radar tracking

[0055] The method 100 for interpolated virtual aperture array (IVAA) radar tracking includes: transmitting a set of detection signals S110, receiving a set of reflected detection signals S120, and calculating initial tracking parameters S130 based on the set of reflected detection signals, such as Figure 6 The method 100 may further include refining the initial tracking parameters S140 and / or modifying the detection signal characteristics S150.

[0056] While the original VAA technique is a powerful technique (especially given that it works well for small transmit and receive arrays), as the size of the virtual array increases, the errors in the system also increase. This is because each additional virtual element is essentially an extrapolation of the physical array. This application is directed to a novel technique that builds on aspects of the original VAA tracking, but does so within the framework of interpolating sparse physical arrays (limiting the errors that arise from adding virtual array elements). For example, Figure 7A The (sparsely spaced) two-transmitter, three-receiver array shown; the receive array can receive the probe signals from the two transmitters and, using VAA, can process the Figure 7B The signal shown increases the aperture and, therefore, the angular resolution. By incorporating interpolation, the angular resolution can be further increased, as Figure 7C Another example of interpolation is shown in Figure 7D-7F (Note that in these examples, while the first pair of physical receiver elements may be spaced some sub-half wavelength apart, additional elements may be spaced farther apart) and Figure 7G-7H (Note here that while the preceding examples are given for a 1D array, it will be understood that the technique can be extended to two or three dimensions.) In this implementation, the performance of the IVAA approaches that of a physical array while requiring a much smaller number of array elements, but the flexibility of the IVAA can provide further advantages. As described in a later section, the IVAA can utilize a FOV detection vector-based approach for target identification that can provide high angular resolution over a wide field of view (FOV) without the drawbacks of traditional beam steering. This technique is referred to hereinafter as "parallel FOV detection." Note that, as with VAA and IVAA, the term "parallel FOV detection" refers specifically to the detection technique described in the later section (and not to any unrelated techniques that share the term). In addition, the IVAA itself can utilize transmit and / or receive phase modifications to further increase the FOV.

[0057] Method 100 is preferably implemented by a system for IVAA radar tracking (e.g., system 200), but may additionally or alternatively be implemented using any suitable target tracking system (e.g., SONAR, LIDAR) capable of performing virtual aperture array target tracking.

[0058] S110 includes transmitting a set of detection signals. S110 is used to transmit a set of signals that, after being reflected by the target, can provide information about the target (e.g., relative position, velocity, etc.). S110 preferably includes transmitting a frequency shift keying (FSK) radar signal or a frequency modified continuous wave (FMCW) radar signal, but S110 may include transmitting any signal that meets these constraints; for example, electromagnetic signals (such as radio waves in radar, infrared / visible light / UV waves in lidar), acoustic signals (such as in sonar).

[0059] S110 preferably includes transmitting at least two different detection signals. The set of detection signals in S110 preferably satisfies two constraints: each of the set is different in phase (as measured from a reference point), and each of the set is distinguishable from each other when received. The phase distinction effectively increases the aperture (thereby improving the angular resolution), while the distinguishability ensures that the signal data is properly processed when received, taking into account the phase distinction.

[0060] S110 can accomplish phase differentiation in several ways. For example, S110 can include transmitting the probe signal from physically different antenna elements. For a target at an angle to the transmitter element, the interval encodes the inherent phase difference (which depends on the angle!), such as Figure 8 As shown. For the distance d TX For two transmitters, the phase difference between the target and the normal at θ is approximately:

[0061]

[0062] And the phase difference seen at the receiver is roughly the same.

[0063] As a second example, S110 may include transmitting the probe signals from the same antenna element at different times, but the probe signals have different phase information. For example, S110 may include transmitting a first signal from an antenna element at a first time, and then transmitting a second phase-shifted signal from the same antenna element at a second time. Note that this is not equivalent to the phase difference in the first example; the phase difference dφ (between the first signal and the second signal) seen at the target is (approximately) constant and independent of the angle of the target. Note also that while this phase difference results in the simulation of an added receiver element, it also results in the simulation of an added transmitter element, as Figure 9 shown.

[0064] The result is that, although the phase differences are due to the antenna element spacing, the size of the virtual aperture is roughly the same for all target angles; in the case of explicit phase shifting, the size of the virtual aperture depends on the target angle. For example, in the case of transmitter spacing, the array shift can be written as

[0065]

[0066] In the case of explicit phase shift

[0067]

[0068] where dφ is constant (and hence d 阵列 depends on the target angle).

[0069] Although S110 preferably performs explicit phase shifting using a phase shifter (i.e., a device whose phase shift is ideally independent of frequency), S110 may additionally or alternatively perform explicit phase shifting using a delay line (or any other device whose phase shift is frequency dependent) and / or any combination of time delays and phase shifters.

[0070] S110 may additionally or alternatively include combined phase shifting techniques (eg, using multiple transmitters spaced a distance apart and phase shifting the transmitters relative to each other).

[0071] Note that although an example with a time constant phase shift is given, S110 may additionally or alternatively include physically moving the emitter (ie, giving d TX Time correlation) and / or modulating the phase over time by adding a phase dφ, where the phase is a function of time. The phase of the transmitted signal over time is called the phase function. The phase function can be referenced to any point. For example, if a first antenna element and a second antenna element (separated by a non-zero distance) generate the same first signal and second signal, respectively, then the phase function of the first signal (referenced to the first transmitter) is said to be the same as the phase function of the second signal (referenced to the second transmitter). However, the phases of these two signals after being reflected by a target at a certain angle relative to the transmitter array do not appear to be the same at the target (or at the receiver array).

[0072] S110 may additionally or alternatively include modulating phase with respect to angle (e.g., by using a steerable or directable antenna and modulating phase while scanning the antenna, using an antenna array and modulating phase for different elements of the array, etc.).

[0073] S110 can also achieve signal distinguishability in any of several ways. As previously described, one way S110 can achieve signal distinguishability is to time-duplex the signal (e.g., transmit a first frequency chirp signal with a first phase encoding and then transmit a second signal with a second phase encoding); however, S110 can additionally or alternatively make the signal distinguishable by frequency division multiplexing the signal (e.g., transmit the first frequency chirp signal in a first frequency band and transmit the second frequency chirp signal in a second frequency band that does not overlap with the first frequency band), or by encoding the signal (e.g., using a different frequency modulation or amplitude modulation technique to distinguish the signal from other signals). S110 can additionally or alternatively achieve signal distinguishability in any way.

[0074] S120 includes receiving a set of reflected probe signals. S120 is used to receive data generated by reflections of the probe signals transmitted in S110. S120 preferably includes measuring phase, amplitude, and frequency information from the reflected probe signals, but S120 may additionally or alternatively include measuring any available characteristics of the reflected probe signals.

[0075] S120 preferably includes measuring any data needed to recover signal identification information (ie, information for determining to which signal in the transmit group the reflected probe signal corresponds).

[0076] S130 includes calculating initial tracking parameters based on the set of reflected detection signals. S130 is used to calculate a set of tracking parameters that at least identify the position of the target relative to the radar receiver; additionally or alternatively, the tracking parameters may include additional parameters related to object tracking (e.g., target velocity, target acceleration). Note that S130 may include calculating more tracking parameters for a given target than required to obtain a position solution; for example, as described later, although only range, azimuth, and elevation may be necessary to calculate the target position, a composite angle may also be calculated and used to improve and / or check the azimuth / elevation calculation.

[0077] Furthermore, although S130 primarily includes calculating tracking parameters based on the reflected detection signal, S130 may additionally or alternatively calculate or otherwise receive parameters related to target tracking (eg, radar self-motion speed) that are not calculated using the detection signal.

[0078] The parameters used to establish the target position can be defined in any coordinate system and basis. In the present application, the target position is preferably expressed in a Cartesian coordinate system, where the origin is at the radar (e.g., x, y, z represents the target position), or in a spherical coordinate system, where the origin is the same, where the position is defined by range (R), azimuth (α), and elevation (θ); alternatively, the target position can be described in any way. Note that the elevation angle (and similarly the azimuth angle) are examples of angles between a reference vector and a projected target vector; the projected target vector is a vector between an observer (e.g., a radar) and the target, projected into a reference plane (the reference plane containing the reference vector). Method 100 can include calculating any such angles.

[0079] While any parameter related to target tracking can be calculated in S130 as previously described, some additional parameters that can be calculated include target range rate (dR / dt, typically calculated from Doppler data), relative target velocity (the velocity of the target relative to the radar receiver), and radar self-motion velocity (referred to herein as self-velocity, the velocity of the radar receiver relative to a stationary position). These may be related; for example, range rate is equal to relative target velocity multiplied by the cosine of the looking angle between the radar and the target.

[0080] S130 may additionally or alternatively include calculating a composite angle (β, the angle between the target and the radar: β = arccos [cos α × cos θ], see also Figure 10 While the composite angle can be derived from the elevation and azimuth angles (and vice versa), it can also be calculated from Doppler data. For example, if the elevation and azimuth angles are calculated from a first data source (e.g., phase differences between receivers in a receiver array), and the composite angle is calculated from a second data source (e.g., Doppler shift and relative velocity), the composite angle can be used together with the elevation and azimuth angles to produce a more accurate solution.

[0081] S130 may include calculating tracking parameters based on any suitable data source. For example, operating on a radar system having a horizontal receiver array, azimuth can be calculated based on the phase difference between the reflected probe signals seen by each receiver in the array. Similarly, a vertical receiver array can calculate elevation in a similar manner (and / or a two-dimensional receiver array can calculate elevation and azimuth in a similar manner). For example, range can be calculated based on the propagation time of the probe signal. For example, the rate of change of range can be calculated instantaneously (e.g., using Doppler shift data) or over time (e.g., by measuring the change in range over time). As previously described, the composite angle can be derived from the elevation / azimuth angles, or calculated explicitly from the Doppler data: f D ≈Kv cosβ;

[0082] Alternatively, S130 may include calculating the relative target velocity in any manner. For example, S130 may include determining that the target is stationary and calculating the relative target velocity based on the self-velocity (i.e., in this case, the relative target velocity is the self-velocity). The target may be determined to be stationary in any manner; for example, by visually identifying the target as a stationary target (e.g., a stop sign may be identified by its appearance), identifying the target as a stationary target by its radar cross section (e.g., a stop sign or road may be identified by its shape or other features), by comparing Doppler data with other (e.g., phase) data (e.g., if the composite angle provided by the Doppler data is substantially different from the composite angle derived from the elevation and azimuth angles, it may be a moving target), by the size of the target, or in any other manner. Similarly, the self-velocity may be determined in any manner (e.g., a GPS receiver or IMU coupled to the radar receiver's location, an external tracking system, etc.). As another example, S130 may include receiving relative target velocity information based on external data; for example, an estimate from a visual tracking system coupled to the radar receiver's location. Relative target velocity information can even be provided by an external tracking system or the target itself (e.g., transmitting IMU data from a target vehicle).

[0083] To determine the Doppler shift, S130 may include transforming the reflected signal data into the frequency domain using a fast Fourier transform (or any other technique that transforms a time domain signal into the frequency domain for analysis). S130 may also improve system performance by using a sliding fast Fourier transform (SFFT) or similar techniques, such as a sliding discrete Fourier transform (SDFT) and a short-time Fourier transform (STFT). These techniques allow the Fourier transform of successive samples in a sample stream to be calculated with significantly lower computational overhead, thereby improving performance.

[0084] S130 preferably includes calculating initial tracking parameters from two or more reflected detection signals by first linking signal instances to receiver elements S131 and generating interpolated signal instances S132. Based on the linked instances (including those generated by interpolation), S130 includes calculating tracking parameters. S130 may then include calculating tracking parameters by performing beamforming (S133) and / or by performing parallel FOV detection (S134).

[0085] S131 includes linking signal instances to receiver elements. S131 is used to associate a signal instance received at a given receiver element with a real or virtual receiver element. For example, a radar system that time-duplexes a first (zero-phase) signal and a second (phase-shifted) signal may associate a signal instance received at a physical receiver element with that receiver element (if the reflected signal is the first signal) or with a shifted virtual receiver element (if the reflected signal is the second signal). Note that while in some cases the translation of the virtual receiver element is independent of the target angle, in cases where the translation of the virtual receiver element is dependent on the target angle, it may be necessary to first independently determine the target angle (in order to know the position of the virtual receiver element) using one or more subsets of the received signals (each subset corresponding to one of the unique transmitted signals) before jointly using all received signals. In other words, a virtual element can be described in terms of a physical element via an element translation function; if this translation function is not yet known (such as in the case of spaced transmitters), S131 may include determining the element translation function for a given target.

[0086] S132 includes generating interpolated signal instances. S132 is used to generate additional signal instances from those captured signal instances, wherein these additional signal instances correspond to additional virtual receiver elements located between other receiver elements (real or virtual). For example, if in S131 the signal instances are linked to physical receiver elements at positions {0, d, 2d, 3d} and virtual receiver elements at positions {10d, 11d, 12d, 13d}, then S132 may include generating additional signal instances corresponding to virtual receiver elements at positions {4d, 5d, ..., 8d, 9d}. S132 may use any technique to generate these interpolated signal instances.

[0087] In one embodiment, S132 includes generating a linear combination of phase modulation codes (transmitted by a transmitter of the ranging system) to simulate signal components as expected and / or predicted at the interpolated receiver elements.

[0088] S133 includes performing beamforming on the receiver elements. Once the data has been linked to the real or virtual receiver element positions, S133 uses beamforming techniques to calculate object tracking data (e.g., target range and angle). Beamforming techniques that S133 may use include, but are not limited to, conventional (i.e., Bartlett) beamforming, minimum variance distortionless response (MVDR, also known as Capon) beamforming, multiple signal classification (MUSIC) beamforming, or any other beamforming technique.

[0089] S133 preferably includes performing digital beamforming for a given array of target tracking elements using every element in the array (real and virtual elements), but S133 may additionally or alternatively use any subset of elements to perform angle calculations. In some embodiments, S133 may include dynamically selecting receiver elements for performing digital beamforming techniques (e.g., based on receiver noise or any other relevant factors).

[0090] S134 includes performing parallel FOV detection. In parallel FOV detection, signals from pairs of receiver elements (each corresponding to a different field of view) are analyzed in parallel to determine an angle-to-target.

[0091] For example, consider a system with n elements {e1, ..., e n} (for example, Figure 11A As shown). n-1 pairs can be composed of the first element: {e 12 ,…,e 1n Each pair has an associated FOV given by:

[0092]

[0093] where d is the inter-element spacing. Note that while this formula assumes regular inter-element spacing, it should be understood that the elements do not need to be regularly spaced (even without regular inter-element spacing, the basic relationship of FOV being inversely proportional to the distance between the first and i-th elements holds true). The FOV of the entire system (i.e., the widest FOV) is the FOV of the first two elements:

[0094]

[0095] In a traditional phased array radar system, the angular resolution of the array is Note here that the resolution decreases as the angle moves away from the central angle α = 0. For example, when (resolution at the center angle), (for This is why beamforming is often performed on such arrays - by steering the central angle over the FOV, high angular resolution can be achieved (but this requires modifying the phase over time to accomplish the beam steering).

[0096] In parallel FOV detection, FOV detection vectors are generated for multiple FOVs instead of beam steering over a wide FOV to maintain angular resolution. Figure 11B As shown in Figure 2, consider two targets (target 1 and target 2). Target 1 is located in the third narrowest FOV (width is ) and each wider FOV {FOV n-2 ,…FOV2}, while target 2 exists in all FOVs {FOV n , ... FOV2}. By performing object detection in parallel on a set of FOVs, a FOV detection vector can be generated for each detected object. For example, object 1 (at angle θ1) may be associated with a FOV detection vector that looks like {θ1, ..., θ1, x, x}. The first series θ1 indicates that object 1 has been detected by each element pair e 12 …e 1(n-2) is detected at θ1, while x is shown at {e 1(n-1) , e 1n Similarly, target 2 may be associated with a FOV detection vector that looks like {θ2,…,θ2,θ2,θ2}.

[0097] In other words, a FOV detection vector may be calculated for a superset pair of radar array elements comprising the physical elements of the array and first and second sets of virtual elements (corresponding to the virtual elements generated by phase shifting and interpolation, respectively).

[0098] It is worth noting that at wider angles, the angular resolution is poor (as mentioned above). However, the angular differences between FOVs are relatively small. For example, imagine an array with 2λ element spacing and 10 elements. The FOVs are as follows: {29°, 14.4°, 9.6°, 7.2°, 5.7°, 4.8°, 4.1°, 3.6°, 3.2°}. At FOV4…FOV 10 The elements are detected within 0±4.8° (i.e., within 0±4.8°). The size of FOV3 and FOV4 differs by 2.4°. At this angle, the angular resolution of a conventional array (not performing beam steering and using only three elements) would be 9.6°. (We only use three elements because the FOV of a 4+ element array with this spacing would be narrower than the area where the target is located). Similarly, the conventional array with beam steering achieves a resolution of 2.8°. The key point here is that parallel FOV detection can achieve an accuracy comparable to that of beam steering (without actually performing the time-intensive phase modulation required to perform beam steering).

[0099] Therefore, S134 preferably includes generating a FOV detection vector for the detected target and determining the angle to the target based on the FOV detection vector. Each detection vector preferably includes an entry for each FOV window (corresponding to each possible pair of a reference receiver element and all other receiver elements) corresponding to whether the target was detected (and / or a value that can be used to indicate the entry, such as a detection probability magnitude and / or an angle to the target calculated based on the receiver pair); additionally or alternatively, the FOV detection vector can include any information relevant to determining the target angle. FOV detection across the FOVs preferably occurs simultaneously, but can additionally or alternatively occur sequentially or in any other manner.

[0100] Note that the above examples are given for a single transmit signal. When multiple transmit signals are used (e.g., via time division multiplexing or via multiple transmitter elements), the detection vector can include data for each transmit signal. Notably, because the transmit elements themselves can be in an array (physical, virtual, or other), using multiple transmit signals can also increase the angular resolution of method 100 (i.e., the transmit signals themselves form the "field of view").

[0101] S140 includes refining the initial tracking parameters. S140 is used to generate a more accurate tracking solution than the one initially calculated in S130. In a first example implementation, S140 includes running a Kalman filter on the Cartesian coordinates of the target, the Cartesian coordinates of the target being generated by an elevation angle or an azimuth angle (determined based on phase information), a range, and a composite angle constrained by an error bound on the composite angle. In a second example implementation, S140 includes running a Kalman filter on the Cartesian coordinates of the target, the Cartesian coordinates of the target being generated by an elevation angle and an azimuth angle (determined based on phase information), a range, and a composite angle constrained by an error bound on the composite angle.

[0102] S140 may additionally or alternatively include filtering, refining, and / or constraining tracking parameters in any manner.

[0103] S150 includes modifying the detection signal characteristics. S150 is used to modify the characteristics of the transmitted detection signal (at one or both of the transmitter and receiver elements) to ensure high performance of the radar tracking algorithm. One advantage of method 100 is that virtual transmitter / receiver elements can be added (and the virtual aperture expanded) or removed at will. Adding more virtual elements increases the potential accuracy of object tracking performed by method 100, but also increases the latency of object tracking.

[0104] S150 may include modifying the detection signal characteristics based on the output of S130; for example, if it is detected during object tracking that a first set of data (e.g., corresponding to an earlier transmitted signal and a real receiver) and a second set of data (corresponding to a later transmitted signal and a virtual receiver) fail to converge to an object tracking solution within a threshold error range, S150 may include modifying the transmitted signal to reduce the number of virtual elements (e.g., reducing the number of different phase-encoded signals from three to two).

[0105] Alternatively, S150 may include modifying the detection signal characteristics based on other data. For example, S150 may include modifying the detection signal data based on radar array motion (e.g., vehicle speed for a vehicle-mounted radar); modifying the transmission to increase the virtual aperture when the vehicle is moving slower, and modifying the transmission to decrease the virtual aperture when the vehicle is moving faster.

[0106] S150 may additionally or alternatively include modifying (at the transmitter or receiver) the probe signal characteristics in any manner.

[0107] In one implementation of an embodiment of the present invention, S150 includes performing beam steering on one or both of the transmit signal and the receive signal. This is different from the beam forming previously described for conventional linear radar arrays (where a narrow beam is scanned over a wide and static FOV, such as Figure 12A Compared to the S150, the beam steering is used to move the center angle of all FOVs, as shown in Figure 12B As shown. Beam steering is preferably performed by modifying the phase of the transmitted signal at the transmitting element or the receiving element, but can additionally or alternatively be performed in any manner. Beam steering can be used to further increase angular resolution (detection accuracy / resolution can be improved by scanning the entire FOV2 at a known deflection angle when a detected target crosses the FOV boundary).

[0108] Note that since the spacing between array elements may be larger than λ / 2, aliasing may occur, e.g. Figure 13 In this case, S150 may include controlling or otherwise modifying the signal (at the transmitter and / or receiver) to help reject aliasing. For example, the transmitter FOV may be scanned independently of the receiver FOV, eliminating symmetries that would otherwise prevent detection of a true target through aliasing. For example, if the transmit array is scanned so that the null of the transmit pattern falls on an alias, the target will still appear (e.g., Figure 14A If the zero point falls on the real target, the target will have no transmitted signal to reflect, as shown in Figure 14B shown.

[0109] 2. System for interpolated virtual aperture array radar tracking

[0110] like Figure 15 As shown, system 200 for interpolated virtual aperture array (IVAA) radar tracking includes a transmitter array 210, a horizontal receiver array 220, and a signal processor 240. System 200 may additionally include a vertical receiver array 230 and / or a velocity sensing module 250.

[0111] Furthermore, the system 200 may include any number of virtual transmitters 211 and / or virtual receiver elements 222 / 232, such as Figure 16 as shown (although not explicitly shown here, it should be understood that such virtual receiver elements may also include interpolation elements as described in method 100).

[0112] Similar to method 100, system 200 utilizes IVAA radar tracking to simulate increased radar aperture (as exhibited by SAR) without incurring the additional cost / size of increasing the physical array size or the severe disadvantages of SAR (e.g., motion data requirements and high processing latency).

[0113] The IVAA radar tracking technique of system 200 works by simultaneously capturing an instance of a first signal at a physical array (like a conventional phased array), then capturing an instance of a second signal at the same physical array (capturing the instance of the second signal simultaneously, but not necessarily at the same time as capturing the instance of the first signal); if applicable, capturing additional instances in the same manner, and finally processing the data received from all captured instances together to generate a higher resolution radar tracking solution than would otherwise be possible. Notably, the first signal and the second signal (and any additional signals) are encoded with different phase information. This different phase information enables the instance of the second signal to be treated as if it were received at a virtual receiver array that is shifted relative to the physical array (creating a virtual aperture that is larger than the physical aperture). For example, one can Figure 4A A first signal with a first phase encoding is captured as shown and can be Figure 4B A second signal with a second phase encoding is shown captured; these signals can be processed together as shown in FIG4C .

[0114] Transmitter 210 is used to transmit a signal that, after being reflected by a target, can provide information about the target (e.g., relative position, velocity, etc.). Transmitter 210 preferably transmits a frequency shift keying (FSK) radar signal or a frequency modified continuous wave (FMCW) radar signal, but transmitter 210 can transmit any signal that meets these constraints; for example, electromagnetic signals (e.g., in the form of radio waves in radar, infrared / visible light / UV waves in lidar), acoustic signals (e.g., in the form of sonar).

[0115] Transmitter 210 preferably has multiple transmit elements (e.g., a transmit array), but may additionally or alternatively have a single transmit element (e.g., a transmit antenna). If transmitter 210 has multiple elements, these elements may include a single transmitter paired with multiple antennas (e.g., spaced in a particular pattern and / or paired with antennas coupled to phase / time delays); multiple transmitters, each paired with a single antenna; multiple transmitters paired with multiple antennas, or any other configuration. For example, transmitter 210 may include transmitter elements spaced apart at a distance that is significantly greater (e.g., >3x) than the distance between receiver elements. Similarly, the transmitter array may be oriented in any manner relative to the receiver array.

[0116] In addition to transmitter 210, system 200 may additionally include any number of virtual transmitters 211. As described in section 100 of method 100, a virtual transmitter is created by phase shifting the output of one or more real transmitters 210 and may correspond to a translational element of transmitter 210.

[0117] The horizontal receiver array 220 is used to receive data generated by reflections of the probe signal transmitted by the transmitter 210. The horizontal receiver array 220 preferably measures phase, amplitude, and frequency information from the reflected probe signal, but the horizontal receiver array 220 may additionally or alternatively measure any usable characteristic of the reflected probe signal.

[0118] Tracking parameters associated with the tracked target can be calculated based on the data received from the horizontal receiver array 220. The horizontal receiver array 220 is preferably used to determine the azimuth angle (α), such as Figure 9 As shown, the parameters used to establish the target position can be defined in any coordinate system and basis, and the horizontal receiver array 220 can be used to determine any relevant tracking parameters. In the present application, the target position is preferably expressed in a Cartesian coordinate system with the origin at the radar (e.g., x, y, z represent the target position), or in a spherical coordinate system with the same origin, where the position is defined by range (R), azimuth (α), and elevation (θ); alternatively, the target position can be described in any manner. Note that the elevation angle (and similarly the azimuth angle) are examples of angles between a reference vector and a projected target vector; the projected target vector is a vector between an observer (e.g., a radar) and the target, projected into a reference plane (a reference plane containing the reference vector). The system 100 can calculate any such angles.

[0119] The horizontal receiver array 220 includes a set of receiver elements 221 arranged in a pattern, for example, along a horizontal axis. The set of receiver elements 221 can include a single receiver paired with multiple antennas (e.g., spaced apart in a particular pattern and / or paired with antennas coupled to phase / time delays); multiple receivers, each paired with one antenna; multiple receivers paired with multiple antennas, or any other configuration.

[0120] The horizontal receiver array 220 may additionally include any number of virtual receiver elements 222. As described in part of method 100, the virtual receiver elements 222 are created in response to phase shifts (or by interpolation) of the outputs of one or more real transmitters 210 and may correspond to the translated receiver elements 221 of the horizontal receiver array 220.

[0121] The horizontal receiver array 220 is preferably used to calculate angle from phase information, but may additionally or alternatively be used to calculate angle in any manner (eg, using the horizontal component of the Doppler shift).

[0122] The vertical receiver array 230 is preferably substantially similar to the horizontal receiver array 220, except that the vertical receiver array is arranged on an axis that is not parallel to the axis of the horizontal receiver array (e.g., a vertical axis). The vertical receiver array 230 is preferably used to calculate elevation angles, but may additionally or alternatively be used to calculate any tracking parameter. The vertical receiver array 230 includes a plurality of receiver elements 231 and may additionally include any number of virtual receiver elements 232. As described in section 100 of method 100, the virtual receiver elements 232 are created in response to phase shifts in the outputs of one or more real transmitters 210, and the virtual receiver elements 232 may correspond to the translated receiver elements 231 of the vertical receiver array 230.

[0123] Signal processor 240 is used to calculate tracking parameters based on data collected by horizontal receiver array 220, vertical receiver array 230, and / or velocity sensing module 250. Signal processor 240 preferably comprises a microprocessor or microcontroller that calculates tracking parameters according to method 100; additionally or alternatively, signal processor 240 may calculate tracking parameters in any manner. Signal processor 240 may additionally or alternatively be used to communicate with an external computer (e.g., to offload computations, receive additional data, or for any other reason). Signal processor 240 may also control the configuration of components of system 200 or any computations or actions performed by system 200. For example, signal processor 240 may be used to control the creation of virtual transmitters or virtual array elements and / or other parameters, as described in section 100 of method 100.

[0124] Speed ​​sensing module 250 is used to determine the speed of system 200 (or a component of system 200, or an object coupled to system 200). Speed ​​sensing module is preferably a communication interface coupled to an inertial measurement unit (IMU), but may additionally or alternatively be any communication interface (e.g., Wi-Fi, Ethernet, ODB-II) or sensor (accelerometer, wheel speed sensor, IMU) capable of determining speed and / or velocity.

[0125] The methods of the preferred embodiments and variations thereof may be embodied and / or implemented, at least in part, as a machine configured to receive a computer-readable medium storing computer-readable instructions. The instructions are preferably executed by a computer-executable component that is preferably integrated with a system for IVAA radar tracking. The computer-readable medium may be stored on any suitable computer-readable medium, such as RAM, ROM, flash memory, EEPROM, optical devices (CD or DVD), hard drives, floppy drives, or any other suitable device. The computer-executable component is preferably a general-purpose or special-purpose processor, but any suitable special-purpose hardware or hardware / firmware combination device may alternatively or additionally execute the instructions.

[0126] As those skilled in the art will recognize from the previous detailed description and from the accompanying drawings and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of the invention defined in the appended claims.

Claims

1. A method for interpolated virtual aperture array radar tracking, comprising: transmitting a first detection signal, wherein the first detection signal has a first phase function; transmitting a second detection signal having a second phase function; receiving, at a radar array, a first set of signal instances corresponding to a first reflected detection signal in response to reflection of the first detection signal by a tracked target, wherein the tracked target and the radar array are connected by a target vector; wherein the radar array includes a plurality of radar elements positioned along a first radar axis; receiving, at the radar array, a second set of signal instances corresponding to a second reflected detection signal in response to a reflection of the second detection signal by the tracked target; calculating a target distance based on at least one of the first reflected detection signal and the second reflected detection signal; linking the first set of signal instances to physical receiver elements of the radar array; linking the second set of signal instances to a first set of virtual elements of the radar array; wherein the virtual elements of the radar array are described in terms of physical elements of the radar array via element translation functions; generating a third set of signal instances by interpolating the first set of signal instances and the second set of signal instances; linking the third set of signal instances to a second set of virtual elements of the radar array; calculating a first target angle between a first reference vector and a first projected target vector; wherein the first projected target vector is a target vector projected into a first reference plane, the first reference plane containing both the first radar axis and the first reference vector, wherein calculating the first target angle comprises performing parallel field of view (FOV) detection using the first set of signal instances, the second set of signal instances, and the third set of signal instances, and wherein performing the parallel FOV detection comprises generating a first set of FOV detection vectors for first and other element pairs of a superset of receiver elements, the superset of receiver elements comprising the physical receiver element and the first and second sets of virtual elements; calculating the first target angle using the first set of FOV detection vectors; and The position of the tracked target relative to the radar array is calculated according to the target distance and the first target angle.

2. The method according to claim 1, wherein Calculating the first target angle includes performing beamforming using the first set of signal instances, the second set of signal instances, and the third set of signal instances.

3. The method according to claim 1, wherein Performing parallel FOV detection also includes simultaneously generating the first set of FOV detection vectors.

4. The method according to claim 1, wherein Calculating the first target angle includes calculating one of an elevation angle and an azimuth angle.

5. The method according to claim 1, wherein Transmitting the first detection signal includes transmitting the first detection signal from a first transmitter element; wherein transmitting the second detection signal includes transmitting the second detection signal from a second transmitter element; wherein the first transmitter element and the second transmitter element are separated by a non-zero distance.

6. The method according to claim 5, wherein: The first phase function referenced to the first radiator element is the same as the second phase function referenced to the second radiator element.

7. The method according to claim 6, wherein: The element translation function is independent of the first target angle.

8. The method according to claim 6, wherein: The first detection signal is transmitted during a first time period; wherein the second detection signal is transmitted during a second time period, the second time period being after the first time period and not overlapping with the first time period.

9. The method according to claim 6, wherein: The first detection signal is transmitted in a first frequency band; wherein the second detection signal is transmitted in a second frequency band that does not overlap with the first frequency band.

10. The method according to claim 6, wherein: The first detection signal is encoded using a first amplitude modulation; wherein the second detection signal is encoded using a second amplitude modulation different from the first amplitude modulation.

11. The method according to claim 5, wherein: The first phase function referenced to the first radiator element is different from the second phase function referenced to the second radiator element.

12. The method according to claim 11, wherein The first phase function and the second phase function differ by a constant phase.

13. The method according to claim 11, wherein The first phase function and the second phase function differ by a time-varying phase.

14. The method according to claim 11, wherein The element translation function depends on the first target angle.

15. The method of claim 1, further comprising modifying at least one of the first detection signal and the second detection signal in response to calculated position data.

16. The method according to claim 15, wherein Modifying at least one of the first and second probe signals includes modifying the at least one of the first and second probe signals to add virtual elements to the radar array and widen a virtual aperture of the radar array.

17. The method according to claim 15, wherein: Modifying at least one of the first detection signal and the second detection signal includes modifying the phase of at least one of the first detection signal, the second detection signal, the first reflected detection signal, and the second reflected detection signal so as to modify the central angle used by the parallel FOV detection.

18. The method according to claim 17, wherein The phases of the first detection signal and the second detection signal are modified independently of the phases of the first reflected detection signal and the second reflected detection signal, thereby enabling rejection of target aliasing.

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